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Brine mining can represent a valuable non-conventional resource for the extraction of Mg, Li, B, Sr and other Trace Elements (TEs) such as Rb, Cs, whose recoveries require chemical reagents such as alkaline and acidic solutions. In a circular strategy, these required chemicals can be produced in-situ through Electrodialysis with Bipolar Membranes (EDBM). In this work, a laboratory EDBM unit was operated using real brines from Trapani saltworks to investigate, for the first time, the migration of minor and trace ions, as Li, B, Sr, Cs and Rb through ion-exchange membranes (IEMs). Two different operating configurations were tested by feeding real brines: i) only in the salt channel or ii) in both salt and alkaline compartments. Trace ions migration was assessed by determining their apparent transport number in IEMs to better understanding their "fate" within the EDBM process. The use of real solutions in the base channel resulted in a 50 % reduction in the process water demand, while achieving similar overall Current Efficiencies (75-78 %) and Specific Energy Consumptions (1.50-1.80 kWh/kg NaOH ) compared to the reference layout, where real brine was only fed in the salt compartment. Li, Rb, Sr and Cs were mostly transported across the cation-exchange membrane and concentrated in the alkaline channel. Such results lay the ground for the use of complex (multi-ionic) solutions and new designs of the EDBM process that can be operated in integrated chains to valorise saline wastes, reducing water consumption and avoiding the dilution of trace elements before their selective recovery., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

This study addresses the potential of sourcing Critical Raw Materials (CRMs) using Acidic Mine Waters (AMWs) as a secondary resource. AMWs, often viewed as waste, contain valuable metals like zinc and copper, as well as critical metals like magnesium and cobalt. Moreover, recent studies also reported the presence of Rare Earth Elements (REEs) at concentrations (mg/L) that make their extraction both technically and economically viable. The research focuses on a circular process to recover these metals from AMWs, specifically from the Aznalcóllar open-pit mine, which contains 216 mg/L of Al, 47 mg/L of Fe, 547 mg/L of Zn, and 18.56 mg/L of REEs. The proposed method involves pre-treating the AMW to remove Fe and Al, achieving removals of over 99.9 % and 90 %, respectively, at pH 4.5. Following this, transition metals like Zn, Cd, and Cu were removed as sulphides with a removal efficiency exceeding 99 %. This pre-treatment step reduced the concentration of competing metals in the ion-exchange process, thereby enhancing the recovery and purity of REEs. To separate heavy and light REEs, two types of resins in series were used: an impregnated resin (TP272) and a chelating resin (S930), which can be regenerated using sulphuric acid (H 2 SO 4 ). The final recovery of REEs as oxalates was achieved using oxalic acid and ammonia at pH 1, with further optimization of the elution process to minimize ammonia consumption and undesired precipitation of other oxalates. Finally, REE oxalates with purities exceeding 90 % were obtained. This research demonstrates a sustainable method for efficiently recovering valuable REEs from AMWs, while also addressing environmental concerns related to hazardous sludge generation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The technical feasibility of leaching antimony from an antimony-bearing copper sulphide concentrate, using alkaline sulphide solutions and microwave-assisted and non-assisted heating technology, is investigated at a laboratory scale. The leaching test examines the influence of selective leaching reagent (Na 2 S and NaOH) concentrations, solid/liquid ratio, and temperature. The results indicate that antimony dissolution is highly selective (e.g. only Sb and As are leached), depending on the concentrations of leaching reagents and the leaching temperature. The influence of temperature on the mineral's dissolution, in the range 25-140 °C, is analysed from a thermochemical point of view using equilibrium databases. Under the optimal conditions: leaching agent: 250 g/L Na 2 S, 60 g/L NaOH, 2 h, 140 °C, with microwave assisted, the leaching efficiency of Sb reached 95.7 %. The antimony content in the copper concentrate is successfully reduced from 1.1 wt% to <0.2 wt% Sb, making it suitable for copper concentrate metallurgical processing. The study demonstrates that increasing temperature and NaOH/Na 2 S concentrations collectively enhance leaching efficiency, with a statistical significance, reducing both leaching time and the required temperature, compared to non-microwave-assisted leaching. Furthermore, it is established that excess free hydrogen sulphide ions ensure the efficient dissolution of the main impurities associated with penalties, such as antimony and arsenic, with limited copper and iron dissolution from the copper concentrate, predominantly chalcopyrite. Finally, an integrated hydrometallurgical process flowsheet for antimony removal and recovery from a sulphide copper concentrate is proposed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The global demand for valuable metals and minerals necessitates the exploration of alternative, sustainable approaches to mineral recovery. Seawater mining has emerged as a promising option, offering a vast reserve of minerals and an environmentally friendly alternative to land-based mining. Among the various techniques, Nanofiltration (NF) has gained significant attention as a preliminary treatment step in Minimum Liquid Discharge (MLD) and Zero Liquid Discharge (ZLD) schemes. This study focused on the potential of two underexplored commercial polyamide based NF membranes, Synder NFX and Vontron VNF1, with enhanced divalent over monovalent separation factors, in optimizing the extraction of magnesium hydroxide (Mg(OH) 2 ) from seawater and seawater reverse osmosis (SWRO) brines. The research encompassed a thorough characterization of the membranes utilizing advanced physic-chemical analytical techniques, followed by rigorous experimental assessments using synthetic seawater and SWRO brine in concentration configuration. The findings highlighted the superior selectivity of NFX for magnesium recovery from SWRO brine and the promising concentration factors of VNF1 for seawater treatment. Cross-validation of experimental data with a mathematical model demonstrated the model's reliability as a process design tool in predicting membrane performance. A comprehensive techno-economic evaluation demonstrates the potential of NFX, operating optimally at 23 bar pressure and 70% permeate recovery rate, to yield an estimated annual revenue of 5.683 M€/yr through Mg(OH) 2 production from SWRO brine for a plant with a nominal capacity of 0.8 Mm 3 /y. This research shed light on the promising role of NF membranes in enhancing mineral recovery taking benefit of their separation factors and emphasizes the economic viability of leveraging NF technology for maximizing magnesium recovery from seawater and SWRO brines., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The European Union (EU) identified a list of Critical Raw Materials (CRMs) crucial for its economy, aiming to find alternative sources. Seawater is a promising option as it contains almost all elements, although most at low concentrations. However, to the present, the CRMs' recovery from seawater is technically and economically unfeasible. Other alternatives to implement sea mining might be preferred, such as reverse osmosis brines or saltworks bitterns (after sodium chloride crystallisation). The CRMs' extraction in a selective way can be achieved using highly selective recovery processes, such as chelating sorbents. This study focuses on extracting Trace Elements (TEs) from solar saltworks brines, including boron, cobalt, gallium and germanium, using commercial N-methylglucamine sorbents (S108, CRB03, CRB05). The application of these sorbents has shown potential for boron recovery, but their selectivity for cobalt, gallium, and germanium requires further investigation. This research aims to assess these sorbents' kinetics and column mode performance for TEs recovery from synthetic bitterns. Boron and germanium were rapidly sorbed, reaching equilibrium (>90 %) within 1 h, except for S108, which took 2 h. In column mode, 20-25 pore volumes of bittern were treated to remove boron and germanium, but competition from other elements reduced treatment capacity. An acidic elution (1 M hydrochloric acid) allowed to elute them (>90 %), reaching concentration factors for germanium and boron of 35 and 11, respectively, while cobalt and gallium had less affinity for the sorbents. In addition, the experiments performed were fitted by a mass transfer model to determine the equilibrium constants and selectivities. Therefore, bittern mining has been proven as a secondary/alternative source to obtain CRMs, which can lead the EU to a position in which its dependence on other countries to obtain these raw materials would be decreased., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Ammonia (NH 3 ), as a prevalent pollutant in municipal wastewater discharges, can impair aquatic life and have a negatively impact on the environment. Proper wastewater treatment and management practices are essential to protect ecosystems and keep human populations healthy. Therefore, using highly effective NH 3 -N recovery technologies at wastewater treatment plants (WWTPs) is widely acknowledged as a necessity. In order to improve the overall efficiency of NH 3 removal/recovery processes, innovative technologies have been generally applied to reduce its concentration when discharged into natural water bodies. This study reviews the current status of the main issues affecting NH 3 recovery from municipal/domestic wastewater discharges. The current study investigated the ability to recover valuable resources, e.g., nutrients, regenerated water, and energy in the form of biogas through advanced and innovative methods in tertiary treatment to achieve higher efficiency towards sustainable wastewater and resource recovery facilities (W&RRFs). In addition, the concept of paradigm shifts from WWTP to a large/full scale W&RRF has been studied with several examples of conversion to innovative bio-factories producing materials. On the other hand, the carbon footprint and the high-energy consumption of the WWTPs were also considered to assess the sustainability of these facilities., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

This article investigates the economic and environmental implications of implementing green ammonia production plants in Spain. To this end, one business-as-usual scenario for gray ammonia production was compared with three green ammonia scenarios powered with different renewable energy sources (i.e., solar photovoltaic (PV), wind, and a combination of solar PV and wind). The results illustrated that green ammonia scenarios reduced the environmental impacts in global warming, stratospheric ozone depletion, and fossil resource scarcity when compared with conventional gray ammonia scenario. Conversely, green ammonia implementation increased the environmental impacts in the categories of land use, mineral resource scarcity, freshwater eutrophication, and terrestrial acidification. The techno-economic analysis revealed that the conventional gray ammonia scenario featured lower costs than green ammonia scenarios when considering a moderate natural gas cost. However, green ammonia implementation became the most economically favorable option when the natural gas cost and carbon prices increased. Finally, the results showed that developing efficient ammonia-fueled systems is important to make green ammonia a relevant energy vector when considering the entire supply chain (production/transportation). Overall, the results of this research demonstrate that green ammonia could play an important role in future decarbonization scenarios., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

The recovery of nitrogen and phosphorus is important to promote circular economy in wastewater treatment plants (WWTPs). In this study, the life cycle assessment (LCA) and techno-economic assessment (TEA) of a novel pilot-scale plant aimed at recovering ammonium nitrate and struvite for subsequent application in agriculture was conducted. The nutrient recovery scheme was implemented in the sludge line of the WWTP and included (i) struvite crystallisation and (ii) ion-exchange process combined with gas permeable membrane contactor. The LCA showed that using a fertilizer solution containing the recovered nutrients was environmentally better in most of the impact categories evaluated. Ammonium nitrate was the most important environmental contributor when using the recovered fertilizer solution as a result of the high consumption of chemicals needed for its production. The TEA illustrated that the implementation of the nutrient recovery scheme in the WWTP featured a negative net present value (NPV), primarily attributed to the high consumption of chemicals (representing 30 % of the gross cost). However, the implementation of the nutrient recovery scheme in the WWTP could be economically favourable if the cost of ammonium nitrate and struvite increased to 0.68 and 0.58 €/kg, respectively. The results of this pilot-scale study highlight that nutrient recovery considering the whole value chain for fertilizer application can be an attractive full-scale alternative from a sustainability point of view., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The present study investigates the environmental and economic feasibility of implementing membrane technologies and struvite crystallisation (SC) for nutrient recovery from the anaerobic digestion supernatant. To this end, one scenario combining partial-nitritation/Anammox and SC was compared with three scenarios combining membrane technologies and SC. The combination of ultrafiltration, SC and liquid-liquid membrane contactor (LLMC) was the less environmentally impactful scenario. SC and LLMC were the most important environmental and economic contributors in those scenarios using membrane technologies. The economic evaluation illustrated that combining ultrafiltration, SC and LLMC (with or without reverse osmosis pre-concentration) featured the lowest net cost. The sensitivity analysis highlighted that the consumption of chemicals for nutrient recovery and the ammonium sulphate recovered had a large impact on environmental and economic balances. Overall, these results demonstrate that implementing membrane technologies and SC for nutrient recovery can improve the economic and environmental implications of future municipal wastewater treatment plants., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Highly permeable polyamide reverse osmosis (RO) membranes are desirable for reducing the energy burden and ensuring future water resources in arid and semiarid regions. One notable drawback of thin film composite (TFC) polyamide RO/NF membranes is the polyamide's sensitivity to degradation by free chlorine, the most used biocide in water purification trains. This investigation demonstrated a significant increase in the crosslinking-degree parameter by the m-phenylenediamine (MPD) chemical structure extending in the thin film nanocomposite (TFN) membrane without adding extra MPD monomers to enhance the chlorine resistance and performance. Membrane modification was carried out according to monomer ratio changes and Nanoparticle embedding into the PA layer approaches. A new class of TFN-RO membranes incorporating novel aromatic amine functionalized (AAF)-MWCNTs embedded into the polyamide (PA) layer was introduced. A purposeful strategy was carried out to use cyanuric chloride (2,4,6-trichloro-1,3,5-triazine) as an intermediate functional group in the AAF-MWCNTs. Thus, amidic nitrogen, connected to benzene rings and carbonyl groups, assembles a structure similar to the standard PA, consisting of MPD and trimesoyl chloride. The resulting AAF-MWCNTs were mixed in the aqueous phase during the interfacial polymerization to increase the susceptible positions to chlorine attack and improve the crosslinking degree in the PA network. The characterization and performance results of the membrane demonstrated an increase in ion selectivity and water flux, impressive stability of salt rejection after chlorine exposure, and improved antifouling performance. This purposeful modification resulted in overthrowing two tradeoffs; i) high crosslink density-water flux and ii) salt rejection-permeability. The modified membrane demonstrated ameliorative chlorine resistance relative to the pristine one, with twice the increase in crosslinking degree, more than four times the enhancement of the oxidation resistance, negligible reduction in the salt rejection (0.83 %), and only 5 L/m2.h flux loss following a rigorous static chlorine exposure of 500 ppm.h under acidic conditions. The excellent performance of new chlorine resistant TNF RO membranes fabricated via AAF-MWCNTs together with the facile membrane manufacturing process offered the possibility of postulating them in the desalination field, which could eventually help the current freshwater supply challenge., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

This study evaluates a hybrid system combining zeolites as a sorption stage and a hollow fiber membrane contactor (HFMC) for ammonia (NH 3 ) recovery from treated urban wastewater. Ion exchange with zeolites was selected as an advanced pretreatment and concentration step before the HFMC. The system was tested with wastewater treatment plant (WWTP) effluent (mainstream, 50 mg N-NH 4 /L) and anaerobic digestion centrates (sidestream, 600-800 mg N-NH 4 /L) from another WWTP. Natural zeolite, primarily clinoptilolite, demonstrated effective desorption of retained ammonium using a 2% NaOH solution in a closed-loop configuration, resulting in an ammonia-rich brine that enabled over 95% NH 3 recovery using polypropylene HFMCs. A 1 m 3 /h demonstration plant processed both urban wastewaters, which were pretreated by ultrafiltration, removing over 90% of suspended solids and 60-65% of COD. The 2% NaOH regeneration brines (2.4-5.6 g N-NH 4 /L) were treated in a closed-loop HFMC pilot system, producing 10-15% N streams with potential use as liquid fertilizers. The resulting ammonium nitrate was free of heavy metals and organic micropollutants, making it suitable for use as liquid fertilizer. This comprehensive N management solution for urban wastewater applications can contribute to local economies while achieving reduced N discharge and circularity goals.

In agreement with the Water Framework Directive, Circular Economy and European Union (EU) Green Deal packages, the EU-funded WATER-MINING project aims to validate next-generation water resource solutions at the pre-commercial demonstration scale in order to provide water management and recovery of valuable materials from alternative sources. In the framework of the WATER-MINING project, desalination brines from the Lampedusa (Italy) seawater reverse osmosis (SWRO) plant will be used to produce freshwater and recover valuable salts by integrating different technologies. In particular, electrodialysis with bipolar membranes (EDBM) will be used to produce chemicals (NaOH and HCl). A novel EDBM pilot plant (6.4 m 2 , FuMa-Tech) has been installed and operated. The performance of EDBM for single pass under different flowrates (2-8 L·min -1 ) for acid, base and saline channels, and two current densities (200 and 400 A·m -2 ), has been analyzed in terms of specific energy consumption (SEC) and current efficiency (CE). Results showed that by increasing the flowrates, generation of HCl and NaOH slightly increased. For example, ΔOH - shifted from 0.76 to 0.79 mol·min -1 when the flowrate increased from 2 to 7.5 L·min -1 at 200 A·m -2 . Moreover, SEC decreased (1.18-1.05 kWh·kg -1 ) while CE increased (87.0-93.4%), achieving minimum (1.02 kWh·kg -1 ) and maximum (99.4%) values, respectively, at 6 L·min -1 .

Nitrogen (N) is a macronutrient that, together with P and K, is vital for improving agricultural yields, but its excessive use in crop fertilisation and presence in treated wastewater and sludge are generating emissions both into the atmosphere and into natural water bodies, which leads to eutrophication events. The Haber-Bosch process is energy-intensive and it is the main chemical route to produce reactive nitrogen for the production of fertilisers. Furthermore, there is a strong dependence on imports of reactive nitrogen in Spain and Europe. For these reasons, it is necessary to propose sustainable alternatives that allow solving environmental and supply problems, in addition to proposing efficient management schemes that fit into the circular economy approach. In this context, a nitrogen flow analysis (NFA) was carried out for Spain with the year 2016 as reference. To assess some interactions and flows of N, specific sub-models were also considered for the agriculture and waste management systems. For the food and non-food flow systems, country-specific data were considered. The sectors covered were crop production (CP), animal production (AP), food processing (FP), non-food production (NF) and human consumption (HC). The results reveal a total annual import of 2142 kt N/y, of which 43 % accumulated in stocks of soils and water bodies (913 kt N/y). The largest proportion of losses was associated with emissions from agriculture (724 kt N/y to water bodies and 132 kt N/y accumulated in soils), followed by industry emissions to the atmosphere (122 kt N/y). Wastewater treatment plants (WWTPs) received around 67 kt N/y, of which 26 % was removed as biosolids and 20 % of these biosolids were recovered to be used for fertilising applications. The 49 kt N/y discharged in the final treated effluent represented 79 % of the total loss of reactive nitrogen to water bodies. In addition, an analysis of N-use efficiency and the actions required for its improvement in Spain, as well as the impact of the current diet on the N cycle, was carried out., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Winery wastes are rich in polyphenols with high added value to be used in cosmetics, pharmaceuticals, and food products. This work aims at recovering and purifying the polyphenolic fraction occurring in the malolactic fermentation lees generated during the production of Albariño wines. Phenolic acids, flavonoids, and related compounds were recovered from this oenological waste by green liquid extraction using water as the solvent. The resulting extract solution was microfiltered to remove microparticles and further treated by ultrafiltration (UF) using membranes of 30 kDa and 5 kDa molecular weight cut-offs (MWCOs). The feed sample and the filtrate and retentate solutions from each membrane system were analyzed by reversed-phase liquid chromatography (HPLC) with UV and mass spectrometric (MS) detection. The most abundant polyphenols in the extracts were identified and quantified, namely: caftaric acid with a concentration of 200 µg g -1 and trans-coutaric acid, cis-coutaric acid, gallic acid, and astilbin with concentrations between 15 and 40 µg g -1 . Other minor phenolic acids and flavanols were also found. The UF process using the 30 kDa membrane did not modify the extract composition, but filtration through the 5 kDa poly-acrylonitrile membrane elicited a decrease in polyphenolic content. Hence, the 30 kDa membrane was recommended to further pre-process the extracts. The combined extraction and purification process presented here is environmentally friendly and demonstrates that malolactic fermentation lees of Albariño wines are a valuable source of phenolic compounds, especially phenolic acids., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Membrane contactor is a promising technology for ammonia recovery from the anaerobic digestion centrate. However, high suspended solids and dissolved organic matter concentrations can reduce the effectiveness of the technology. In this study, coagulation-flocculation (C/F) and aeration pre-treatments were evaluated to reduce chemical oxygen demand (COD), turbidity, suspended solids and alkalinity before the ammonia recovery stage using a membrane contactor. The mass transfer coefficient (Km) and total ammonia (TAN) recovery efficiency of the membrane contactor increased from 7.80 × 10 -7 to 1.04 × 10 -5 m/s and from 8 to 67%, respectively, after pre-treating the real sidestream centrate. The pre-treatment results showed that dosing aluminium sulphate (Al 2 (SO 4 ) 3 ) at 30 mg Al/L was the best strategy for the C/F process, providing COD, turbidity and TSS removal efficiencies of 50 ± 5, 95 ± 3 and 90 ± 4%, respectively. The aeration step reduced 51 ± 6% the HCO 3 - content and allowed reducing alkaline consumption by increasing the pH before the membrane contactor. The techno-economic evaluation showed that the combination of C/F, aeration and membrane contactor can be economically feasible for ammonia recovery. Overall, the results of this study demonstrate that C/F and aeration are simple and effective techniques to improve membrane contactor performance for nitrogen recovery from the anaerobic digestion centrate.

The SEArcularMINE project aims to recover critical raw materials (CRMs) from brines from saltworks, thus facing a CRM shortage within Europe. To promote a fully circular scheme, the project valorises concentrated brines using electrodialysis with bipolar membranes (EDBM) to generate the required amounts of reactants (i.e., acids and bases). Regarding the performances of new non-woven cloth ion-exchange membranes (Suez): (i) an ultra-thin non-woven polyester cloth and (ii) a thin polypropylene cloth acting as the support structures were assessed. Additionally, the anion layer includes a catalyst to promote the water dissociation reaction. The effect of current density (100, 200, and 300 A m -2 ) on the performance of two combinations of membranes in an inter-laboratory exercise using 2 M NaCl was evaluated. According to statistical analysis ANOVA, there was an agreement on the results obtained in both laboratories. NaOH/HCl solutions up to 0.8 M were generated working at 300 A m -2 using both combinations of membranes. Regarding the performance parameters, stack set-ups incorporating thin polypropylene membranes showed lower specific energy consumption (SEC) and higher specific productivity (SP) than ultra-thin polypropylene ones. Hence, for ultra-thin polypropylene membranes, SEC was reported to be between 2.18 and 1.69 kWh kg -1 NaOH and SP between 974 and 314 kg m -2 y -1 .

Seawater represents a potential resource for raw materials extraction. Although NaCl is the most representative mineral extracted other valuable compounds such as Mg, Li, Sr, Rb and B and elements at trace level (Cs, Co, In, Sc, Ga and Ge) are also contained in this "liquid mine". Most of them are considered as Critical Raw Materials by the European Union. Solar saltworks, providing concentration factors of up-to 20 to 40, offer a perfect platform for the development of minerals and metal recovery schemes taking benefit of the concentration and purification achieved along the evaporation saltwork ponds. However, the geochemistry of these elements in this environment has not been yet thoroughly evaluated. Their knowledge could enable the deployment of technologies capable to achieve the recovery of valuable minerals. The high ionic strengths expected (0.5-7 mol/kg) and the chemical complexity of the solutions imply that only numerical geochemical codes, as PHREEQC, and the use of Pitzer model to estimate the activity coefficients of the different species in solution can be adopted to provide valuable description of the systems. In the present work, for the first time, PHREEQC Pitzer code database was extended to include the target minor and trace elements using Trapani saltworks (Sicily, Italy) as a case study system. The model was able to predict: i) the purity in halite and the major impurities contained, mainly Ca, Mg and sulphate species; ii) the fate of minor components as B, Sr, Cs, Co, Ge and Ga along the evaporation ponds. The results obtained pose a fundamental step in critical raw materials mining from seawater brine, for process intensification and combination with desalination., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

This study evaluates the NO 3 - removal from groundwater through Heterotrophic Denitrification (HDN) (promoted by the addition of acetate and/or an inoculum rich in denitrifiers) and Abiotic Chemical Nitrate Reduction (ACNR) (promoted by pulse injection of zerovalent iron nanoparticles (nZVI)). HDN and ACNR were applied, separately or combined, in packed soil column experiments to complement the scarce research on pulse-injected nZVI in continuous-flow systems mimicking a Well-based Denitrification Barrier. Together with NO 3 - , the removal of two common pesticides (dieldrin and lindane) was evaluated. Results showed that total NO 3 - removal (>97%) could be achieved by either bioestimulation with acetate (converting NO 3 - to N 2 (g) via HDN) or by injecting nZVI (removing NO 3 - via ACNR). In the presence of nZVI, NO 3 - was partially converted to N 2 (g) and to a lower extent NO 2 - , with unreacted NO 3 - being likely adsorbed onto Fe-(oxy)hydroxides. Combination of both HDN and ACNR resulted in even a higher NO 3 - removal (>99%). Interestingly, nZVI did not seem to pose any toxic effect on denitrifiers. These results showed that both processes can be alterned or combined to take advantage of the benefits of each individual process while overcoming their disadvantages if applied alone. With regard to the target pesticides, the removal was high for dieldrin (>93%) and moderate for lindane (38%), and it was not due to biodegradation but to adsorption onto soil. When nZVI was applied, the removal increased (generally >91%) due to chemical degradation by nZVI and/or adsorption onto formed Fe-(oxy)hydroxides., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The development of an efficient adsorbent is required in tertiary wastewater treatment stages to reduce the phosphate-phosphorous content within regulatory levels (1 mg L -1 total phosphorous). In this study, a natural muscovite was used for the preparation of muscovite/zeolite composites and the incorporation of Fe 3+ /Mn 2+ (oxy)hydroxide nanoparticles for the recovery of phosphate from synthetic wastewater. The raw muscovite MC and the obtained muscovite/sodalite composite LMC were used in the powder form for the phosphate adsorption in batch mode. A muscovite/analcime composite was obtained in the pellets PLMCT 3 and monolith SLMCT 2 forms for the evaluation in fixed-bed mode for continuous operation. The effect of pH, equilibrium and kinetic parameters on phosphate adsorption and its further reuse in sorption-desorption cycles were determined. The characterization of the adsorbents determined the Fe 3+ and Mn 2+ incorporation into the muscovite/zeolite composite's structure followed the occupancy of the extra-framework octahedral and in the framework tetrahedral sites, precipitation and inner sphere complexation. The adsorbents used in this study (MC, LMC, PLMCT 3 and SLMCT 2 ) were effective for the phosphate recovery without pH adjustment requirements for real treated wastewater. Physical (e.g., electrostatic attraction) and chemical (complexation reactions) adsorption occurred between the protonated Fe 3+ /Mn 2+ (oxy)hydroxy groups and phosphate anions. Higher ratios of adsorption capacities were obtained by powder materials (MC and LMC) than the pellets and monoliths forms (PLMCT 3 and SLMCT 2 ). The equilibrium adsorption of phosphate was reached within 30 min for powder forms (MC and LMC) and 150 min for pellets and monoliths forms (PLMCT 3 and SLMCT 2 ); because the phosphate adsorption was governed by the diffusion through the internal pores. The adsorbents used in this study can be applied for phosphate recovery from wastewater treatment plants in batch or fixed-bed mode with limited reusability. However, they have the edge of environmentally friendly final disposal being promissory materials for soil amendment applications.

A parent Mg-Al-LDH was upgraded in its adsorption properties due to the incorporation of tri-metal species oxy(hydroxide) nanoparticles obtaining Mn 2+ /Zn 2+ /Fe 3+ /Mg-Al-LDH composite for the phosphate recovery from simulated urban treated wastewater. The physicochemical properties of the synthesized Mn 2+ /Zn 2+ /Fe 3+ /Mg-Al-LDH make promising for real application without being environmentally harmful. The performance of Mn 2+ /Zn 2+ /Fe 3+ /Mg-Al-LDH composite was evaluated through batch adsorption assays. The support of iron, manganese, and zinc (oxy)hydroxide nanoparticles onto the parent Mg-Al-LDH structure was performed by precipitation, isomorphic substitution, and complexation reactions. The main improvement of the Mn 2+ /Zn 2+ /Fe 3+ /Mg-Al-LDH composite was the highest phosphate adsorption capacity (82.3 mg∙g -1 ) in comparison to the parent Mg-Al-LDH (65.3 mg∙g -1 ), in a broad range of concentrations and the effective phosphate adsorption at neutral pH (7.5) near to the real wastewater effluents conditions in comparison to the conventional limitations of other adsorbents. The effectiveness of Mn 2+ /Zn 2+ /Fe 3+ /Mg-Al-LDH composite was higher than the conventional metal LDHs materials synthesized in a single co-precipitation step. The phosphate adsorption onto Mn 2+ /Zn 2+ /Fe 3+ /Mg-Al-LDH composite was described to be governed by both physical and chemical interactions. The support of Mn 2+ /Zn 2+ /Fe 3+ oxy(hydroxide) nanoparticles over the parent Mg-Al-LDH was a determinant for the improvement of the phosphate adsorption that was governed by complexation, hydrogen bonding, precipitation, and anion exchange. The intra-particular diffusion also described well the phosphate adsorption onto the Mn 2+ /Zn 2+ /Fe 3+ /Mg-Al-LDH composite. Three specific stages of adsorption were determined during the phosphate immobilization with an initial fast rate, followed by the diffusion through the internal pores and the final equilibrium stage, reaching 80% of removal and the equilibrium within 1 h. The Mn 2+ /Zn 2+ /Fe 3+ /Mg-Al-LDH was strongly selective towards phosphate adsorption in presence of competing ions reducing the adsorption capacity at 20%. The Mn 2+ /Zn 2+ /Fe 3+ /Mg-Al-LDH has limited reusability, only 51% of the adsorbed phosphate could be recovered in the second cycle of the adsorption-desorption process. Around 14% of phosphate was loosely-bond to Mn 2+ /Zn 2+ /Fe 3+ /Mg-Al-LDH which brings the opportunity to be a new source of phosphorus. The use of eluted concentrates and the final disposal of the exhausted adsorbent for soil amendment applications can be an integral nutrient system (P, Mn, Zn, Fe) for agriculture purposes.

An extensive experimental campaign on Li recovery from relatively dilute LiCl solutions (i.e., Li + ∼ 4000 ppm) is presented to identify the best operating conditions for a Li 2 CO 3 crystallization unit. Lithium is currently mainly produced via solar evaporation, purification, and precipitation from highly concentrated Li brines located in a few world areas. The process requires large surfaces and long times (18-24 months) to concentrate Li + up to 20,000 ppm. The present work investigates two separation routes to extract Li + from synthetic solutions, mimicking those obtained from low-content Li + sources through selective Li + separation and further concentration steps: (i) addition of Na 2 CO 3 solution and (ii) addition of NaOH solution + CO 2 insufflation. A Li recovery up to 80% and purities up to 99% at 80 °C and with high-ionic strength solutions was achieved employing NaOH solution + CO 2 insufflation and an ethanol washing step., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

The aim of this study was to evaluate the recovery of phenolic compounds from olive mill and winery wastes by conventional solid-liquid extraction (SLE) using water as the extraction solvent. The studied variables were extraction time (5-15 min), temperature (25-90 °C), solid-to-liquid ratio (1:10-1:100 (kg/L)), pH (3-10) and application of multiple extractions (1-3). The extraction efficiency was evaluated in terms of total phenolic content (TPC), determined by high performance liquid chromatography (HPLC-UV), but also from the recovery of some representative phenolic compounds. The optimized conditions were one extraction step, 10 min, 25 °C, 1:30 (kg/L), pH 5 for olive pomace, and one extraction step, 10 min, 70 °C, 1:100 (kg/L), pH 5 for winery residues. The extraction method is simple and suitable for scaling-up in industry, and the aqueous extracts are fully compatible with further purification schemes based on the use of membranes or resins. The optimized technique was applied to a set of different representative residues from olive mill and winery industries, to assess their suitability as sources for phenolic compounds recovery. The phenolic content in the extracts was evaluated by chromatographic analysis and by the Folin-Ciocalteu assay (FC). Furthermore, the antioxidant capacity was determined by 2,2-azinobis-3-etilbenzotiazolina-6-sulfonat (ABTS), 2,-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays. Because of their high contents in phenolic compounds and great antioxidant capacity, olive pomace and lees filters were identified as especially suited sources for phenolic compounds recovery., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Hydrothermally synthesized Linde type A (LTA) and faujasite X (FAU-X) zeolites are low-cost and environmentally benign inorganic carriers for environmental applications. In this study, (oxy)hydroxides were incorporated onto LTA and FAU-X zeolites to promote the phosphate adsorption. The performance of LTA-Fe and FAU-X-Fe was evaluated through batch adsorption assays. A complete evaluation was performed to recover phosphate from synthetic wastewater. The effect of pH, concentration, equilibrium, and kinetic parameters on phosphate adsorption and its further reuse in sorption-desorption cycles were evaluated. LTA-Fe and FAU-X-Fe are effective for adsorption of phosphate at neutral (e.g., pH 7.0 ± 0.2) and in a broad range of phosphate concentrations. Higher ratios of adsorption capacities were obtained by synthetic zeolites enriched with iron in comparison to their parent forms. The phosphate adsorption occurred through hydrogen bonding and complexation reactions between protonated iron hydroxyl groups and phosphate anions. The phosphate monolayer adsorption was followed by diffusion through the internal pores and 80% of the equilibrium adsorption was reached within 50 min. The LTA-Fe and FAU-X-Fe can be used for phosphate recovery from wastewater treatment plants. The use of LTA-Fe and FAU-X-Fe in a tertiary wastewater treatment stage could allow to reduce the phosphate-phosphorous content, reaching the regulatory levels (equal 1 mg L -1 total phosphorous). The phosphate adsorption using LTA-Fe and FAU-X-Fe does not require pH adjustment, and it is endothermic. The reusability of both iron zeolites is limited, and they can be finally disposed for soil amendment applications.

The European Union (EU) depends on third markets to supply many important raw materials. Increasing the circularity of critical raw materials within the EU is important not only from an environmental perspective, but also as a competitive advantage for the EU economy. In the case of boron, the EU's import dependency is about 100%. This work aims to evaluate the boron recovery from seawater desalination plants (SWDP) brines using ion-exchange resins in a circular economy approach. Commercial boron selective resins Purolite S108, DIAION CRB03 and CRB05 were tested and compared on batch and dynamic experiments. Thermodynamic and kinetic experiments were performed, and results were fitted by linear and non-linear models. After a comparison, results showed a good fit to the Langmuir isotherm and the pseudo-second order model, respectively, for all the commercial resins tested. The DIAION CRB03 resin presented higher sorption capacity and percentage of boron sorbed than the other resins and was selected as the best option for boron recovery from SWDP brine. Dynamic experiments in fixed bed column using DIAION CRB03 resulted in a sorption capacity of 13 mg/g of resin, a boron recovery of 98% and a concentration factor of 30, for an initial boron concentration of 50 mg/L. In addition, an economic analysis was carried out as a preliminary estimate of the revenues obtained from the production of boric acid from the brine produced by El Prat desalination plant., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Spinach and orange by-products are well recognized for their health benefits due to the presence of natural polyphenols with antioxidant activity. Therefore, the demand to produce functional products containing polyphenols recovered from vegetables and fruits has increased in the last decade. This work aims to use the integrated membrane process for the recovery of polyphenols from spinach and orange wastes, implemented on a laboratory scale. The clarification (microfiltration and ultrafiltration, i.e., MF and UF), pre-concentration (nanofiltration, NF), and concentration (reverse osmosis, RO) of the spinach and orange extracts were performed using membrane technology. Membrane experiments were carried out by collecting 1 mL of the permeate stream after increasing the flow rate in 1 mL/min steps. The separation and concentration factors were determined by HPLC-DAD in terms of total polyphenol content and by polyphenol families: hydroxybenzoic acids, hydroxycinnamic acids, and flavonoids. The results show that the transmembrane flux depended on the feed flow rate for MF, UF, NF, and RO techniques. For the spinach and orange matrices, MF (0.22 µm) could be used to remove suspended solids; UF membranes (30 kDa) for clarification; NF membranes (TFCS) to pre-concentrate; and RO membranes (XLE for spinach and BW30 for orange) to concentrate. A treatment sequence is proposed for the two extracts using a selective membrane train (UF, NF, and RO) to obtain polyphenol-rich streams for food, pharmaceutical, and cosmetic applications, and also to recover clean water streams.

Liquid-liquid membrane contactors (LLMCs) were studied as a sustainable technology for ammonia recovery from wastewater. Ammonia can be valorized by LLMCs as a potential nutrient and produce liquid fertilizers. Thus, this work aims for the study of different experimental LLMC conditions to produce ammonium salts by an acid stripping stream. The experiments were conducted using two 3M TM Liqui-Cell TM LLMC in a series, located in the vertical position and using HNO 3 as the acid stripping solution. The flow rates for the feed and stripping sides were fixed during the tests, and two steps were conducted based on previous works. However, different experimental conditions were evaluated to determine its effect on the overall performance: (i) replacing the feed or stripping solution between the steps, (ii) the initial ammonia concentration of the feed solution, (iii) feed volume and (iv) feed temperature. The results demonstrated that better achievements were obtained replacing the acid stripping solution between steps, whereas the feed temperature did not substantially affect the overall performance. Additionally, a high initial ammonia concentration provided more ammonia recovery, although the concentration factor achieved was higher for the low initial ammonia concentration. Finally, a high feed volume afforded better results for the fertilizer side, whereas more NH 3 recovery was achieved using less feed volume.

Here, novel hydroxyl and carboxyl functionalized multiwalled carbon nanotubes (AHF-MWCNT and ACF-MWCNT) were successfully synthesized and introduced for modification and antifouling improvement of the PVDF membrane. The blending effect of AHF-MWCNT and ACF-MWCNT on the morphology and surface properties of the PVDF membrane was explored by SEM, AFM, water contact angle, and zeta potential analysis. The results indicated that the membrane surface has become more hydrophilic, smoother as well more negative. In addition, the overall porosity and mean pore radius are increased by MWCNTs embedding. The filtration performance, antifouling and dye separation of the nanocomposite membranes were improved by adding any amounts of AHF-MWCNT and ACF-MWCNT in the PVDF membrane matrix. The carboxylic modification presented better performance than the hydroxyl functionalization. The 0.1 wt% ACF-MWCNT blended membrane presented an optimum performance with 46 L m -2 h -1 bar -1 permeability, 93% FRR, and 97.3% dye rejection. Consequently, embedding functionalized MWCNT in the PVDF membrane matrix was led to improvement of membrane characteristics and enhancement of pure water flux, antifouling feature, and dye separation. So, the functionalized MWCNT could be a promising additive for the PVDF membrane modification., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

This study demonstrates the techno-economic reliability of an innovative fit-for-use treatment train to boost municipal reclaimed water reuse fore industrial uses in the Barcelona Metropolitan Area (BMA). The relatively high conductivity (2090 μS/cm) and hardness (454 mg/L) of reclaimed water in the BMA (e.g. Water Reclamation Plant (WRP) of El Baix Llobregat, Barcelona, Spain), together with the restrictive water quality demands in industrial uses, claims for the implementation of advanced reclamation schemes based on desalination technologies such as reverse osmosis (RO). The study assesses the benefits of two potential pre-treatments of the RO stage: (i) ultrafiltration (UF) or (ii) an innovative high-performance nano-structured polymeric adsorbent (CNM); in which a permeability decline of 5% was observed when CNM was used as a pre-treatment, while a stable permeability of RO was found when was fed by the UF effluent. On the other hand, generic cost curves have been calculated for the technologies evaluated and were applied to estimate capital and operational expenditures (CAPEX and OPEX) for the scale-up in three different industrial sites (e.g., chemical, waste management and electro-coating industries). The economic assessment indicates that the use of municipal reclaimed water is economically competitive in front of the use of tap water in the BMA, providing savings between 0.13 and 0.52 €/m 3 for the waste management industry and between 0.49 and 0.98 €/m 3 for the electrocoating industry. On the other hand, the use of groundwater in one of the industrial sites and its relatively low cost implied that, although it is necessary a RO, the current cost of water is significantly lower., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Winery and olive mill industries generate large amounts of wastes causing important environmental problems. The main aim of this work is the evaluation of different membrane separation processes like microfiltration, ultrafiltration, nanofiltration, and reverse osmosis for the recovery of polyphenols from winery and olive mill wastes in aqueous solutions. Membrane processes were tested separately in a closed-loop system, and by an integration in a concentration mode sequential design (open-loop). Feed flow rate was varied from 1 to 10 mL min -1 , and permeate samples were taken in order to measure the polyphenols concentration. The separation and concentration efficiency were evaluated in terms of total polyphenol content, and by polyphenols families (hydroxybenzoic acids (HB), hydroxycinnamic acids (HC), and flavonoids (F)), using high performance liquid chromatography. Results showed that MF and UF membranes removed suspended solids and colloids from the extracts. NF was useful for polyphenols separation (HB rejections were lower than for HC and F: HB rejections of 50 and 63% for lees filters and olive pomace extracts, respectively), and RO membranes were able to concentrate polyphenols streams (86 and 95% rejection from lees filters and olive pomace, respectively). Membranes sequential designs for lees filters and olive pomace extracts, using a selective membrane train composed by UF, NF and RO membranes, were able to obtain polyphenol rich streams and high-quality water streams for reuse purposes., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

More sustainable waste management in the winery and olive oil industries has become a major challenge. Therefore, waste valorization to obtain value-added products (e.g., polyphenols) is an efficient alternative that contributes to circular approaches and sustainable environmental protection. In this work, an integration scheme was purposed based on sustainable extraction and membrane separation processes, such as nanofiltration (NF) and reverse osmosis (RO), for the recovery of polyphenols from winery and olive mill wastes. Membrane processes were evaluated in a closed-loop system and with a flat-sheet membrane configuration (NF270, NF90, and Duracid as NF membranes, and BW30LE as RO membrane). The separation and concentration efficiency were evaluated in terms of the total polyphenol content (TPC), and by polyphenol families (hydroxybenzoic acids, hydroxycinnamic acids, and flavonoids), using high-performance liquid chromatography. The water trans-membrane flux was dependent on the trans-membrane pressure for the NF and RO processes. NF90 membrane rejected around 91% of TPC for the lees filters extracts while NF270 membrane rejected about 99% of TPC for the olive pomace extracts. Otherwise, RO membranes rejected more than 99.9% of TPC for both types of agri-food wastes. Hence, NF and RO techniques could be used to obtain polyphenol-rich streams, and clean water for reuse purposes.

Acidic mine Drainage (AMD) is still considered one of the greatest mining sustainability challenges due to the large volumes of wastes generated and the high associated treatment cost. New regulation initiatives on sustainable development, circular economy and the need for strategic elements as Rare Earth Elements (REE) may overcome the traditional research initiatives directed to developing low cost treatment options and to develop research initiatives to identify the potential benefit of considering such AMD as a potential secondary resource. As an example, this study develops the integration of a three-stage process where REE are selectively separated from base metals (e.g. Fe, Al, Mn, Ca, Mg, Cd, Pb) and then concentrate to produce a rich REE by-product recovered as REE-phosphates. Selective separation of Fe (>99%) was achieved by total oxidation to Fe(III) and subsequent precipitation as schwertmannite at pH 3,6 ± 0.2. REE were then extracted from AMD using a sulfonic ion-exchange resin to produce concentrated REE sulfuric solutions up to 0.25 gREE/L. In a final stage selective separation of REE from Al(III), Ca(II) and Mg(II) and transitions elements (Cu, Zn, Ni) was achieved by precipitation with phosphate solutions under optimized pH control and total phosphate concentration. XRD analysis identified low-crystalline minerals. By using a thermal treatment the presence of PrPO 4 (s) and Cheralite (CePO 4 (s)) where Ce is substituted by La and Ca and Xenotime (YPO 4 (s)) were found as main minerals AlPO 4 (s) Ca,MgYPO 4 (s) were also identified., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

Injection of zero-valent iron nanoparticles (nZVI) into aquifers has gained increasing attention of researchers for in-situ treatment of NO 3 - -contaminated groundwater. nZVI has proved efficient in chemically reducing NO 3 - and, according to recent research efforts, in supporting biological denitrification under favoured conditions. Given the scarce research on nZVI pulsed injection in continuous-flow systems, the objective of this study was to evaluate the effect of nZVI pulses on the removal of NO 3 - from groundwater in packed soil columns and, more particularly, to elucidate whether or not biotic NO 3 - removal processes were promoted by nZVI. Three identical columns were filled with aquifer soil samples and fed with the same nitrate polluted groundwater but operated under different conditions: (A) with application of nZVI pulses and biocide spiked in groundwater, (B) without application of nZVI pulses and (C) with application of nZVI pulses. Results showed that the application of nZVI (at 30 mg/L and 78 mg/L doses) resulted in an immediate and sharp removal of NO 3 - (88-94%), accompanied by an increase in pH (from 7.0 to 9.0-10.0), a drop in redox potential (Eh) (from +420 mV to <100 mV) and a release of Fe(II) and Total Organic Carbon (TOC) in the effluent (to 200 mg/L and 150-200 mg/L, respectively). The released TOC came from the organic polymer used as stabilizer of the nZVI particles. Comparison against the sterilized control column revealed that, under the experimental conditions, no biological denitrification developed and that the removal of NO 3 - was due to chemical reduction by nZVI. The main by-product of the NO 3 - removal was NH 4 + , which at the prevailing pH was partially converted to NH 3 , which dissipated from the aqueous solution resulting in a net removal of total dissolved N. A mass balance of Fe permitted to quantify the percentage of injected nZVI trapped in the column (>98%) and the NO 3 - retention capacity of the nZVI particles (13.2-85.5 mg NO 3 - /g nZVI)., Competing Interests: Declaration of competing interest Hereby, the authors declare that the content of this article is subject to no conflict of interest., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

The production of olive oil and wine are two of the main agri-food economic activities in Southern Europe. They generate large amounts of solid and liquid wastes (e.g., olive pomace, olive mill wastewater, grape pomace, grape stems, wine lees, and wine processing wastewater) that represent a major environmental problem. Consequently, the management of these residues has become a big challenge for these industries, since they are harmful to the environment but rich in bioactive compounds, such as polyphenols. In recent years, the recovery of phenolic compounds has been proposed as a smart strategy for the valorization of these by-products, from a circular economy perspective. This review aims to provide a comprehensive description of the state of the art of techniques available for the analysis, extraction, and purification of polyphenols from the olive mill and winery residues. Thus, the integration and implementation of these techniques could provide a sustainable solution to the olive oil and winery sectors.

Fruits, vegetables, spices, and herbs are a potential source of phenolic acids and polyphenols. These compounds are known as natural by-products or secondary metabolites of plants, which are present in the daily diet and provide important benefits to the human body such as antioxidant, anti-inflammatory, anticancer, anti-allergic, antihypertensive and antiviral properties, among others. Plentiful evidence has been provided on the great potential of polyphenols against different viruses that cause widespread health problems. As a result, this review focuses on the potential antiviral properties of some polyphenols and their action mechanism against various types of viruses such as coronaviruses, influenza, herpes simplex, dengue fever, and rotavirus, among others. Also, it is important to highlight the relationship between antiviral and antioxidant activities that can contribute to the protection of cells and tissues of the human body. The wide variety of action mechanisms of antiviral agents, such as polyphenols, against viral infections could be applied as a treatment or prevention strategy; but at the same time, antiviral polyphenols could be used to produce natural antiviral drugs. A recent example of an antiviral polyphenol application deals with the use of hesperidin extracted from Citrus sinensis. The action mechanism of hesperidin relies on its binding to the key entry or spike protein of SARS-CoV-2. Finally, the extraction, purification and recovery of polyphenols with potential antiviral activity, which are essential for virus replication and infection without side-effects, have been critically reviewed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Phenolic compounds recovery by mechanical stirring extraction (MSE) was studied from orange and spinach wastes using water as a solvent. The statistical analysis showed that the highest total polyphenol content (TPC) yield was obtained using 15 min, 70 °C, 1:100 ( w/v ) solid/solvent ratio and pH 4 for orange; and 5 min, 50 °C, 1:50 ( w/v ) solid/solvent ratio and pH 6 for spinach. Under these conditions, the TPC was 1 mg gallic acid equivalent (GAE) g -1 fresh weight (fw) and 0.8 mg GAE g -1 fw for orange and spinach, respectively. MSE substantially increased the phenolic compounds yields (1-fold for orange and 2-fold for spinach) compared with ultrasound-assisted extraction. Furthermore, the antioxidant activity of orange and spinach extracts was evaluated using DPPH, FRAP and ABTS. The obtained results pointed out that the evaluated orange and spinach residues provided extracts with antioxidant activity (2.27 mg TE g -1 and 0.04 mg TE g -1 , respectively).

The use of treatments of segregated process streams as a water source, as well as technical fluid reuse as a source of value-added recovery products, is an emerging direction of resource recovery in several applications. Apart from the desired final product obtained in agro-food industries, one of the challenges is the recovery or separation of intermediate and/or secondary metabolites with high-added-value compounds (e.g., whey protein). In this way, processes based on membranes, such as microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO), could be integrated to treat these agro-industrial streams, such as milk and cheese whey. Therefore, the industrial application of membrane technologies in some processing stages could be a solution, replacing traditional processes or adding them into existing treatments. Therefore, greater efficiency, yield enhancement, energy or capital expenditure reduction or even an increase in sustainability by producing less waste, as well as by-product recovery and valorization opportunities, could be possible, in line with industrial symbiosis and circular economy principles. The maturity of membrane technologies in the dairy industry was analyzed for the possible integration options of membrane processes in their filtration treatment. The reported studies and developments showed a wide window of possible applications for membrane technologies in dairy industry treatments. Therefore, the integration of membrane processes into traditional processing schemes is presented in this work. Overall, it could be highlighted that membrane providers and agro-industries will continue with a gradual implementation of membrane technology integration in the production processes, referring to the progress reported on both the scientific literature and industrial solutions commercialized.

Management of in-land reverse osmosis (RO) desalination brines generated from surface brackish waters is a current challenge. Among the different near-Zero and Zero Liquid Discharge (ZLD) alternatives, Membrane Distillation (MD), in which the transport of water is thermally driven, appears as an attractive technology if a residual heat source is available. The aim of this study was to identify the limits of Direct Contact MD (DCMD) pre-treatments such as acidification and aeration, or the combination of both to quantify the scaling reduction potential when treating a RO brine from surface brackish water. Experimental data were used to evaluate the effectiveness of DCMD to achieve the highest concentration factors, depending on the chosen pre-treatment. Additionally, an economic analysis of the operational cost, taking as case study a site where the current management of the brine is the discharge to the sea, was also carried out. Results showed that pre-treatments enhanced MD performance by increasing the concentration factor achieved and highest volume reductions (about 3 times) were reached with the combination of acidification and aeration pre-treatments. Both processes reduced the precipitation potential of CaCO 3 (s) by reducing the total inorganic carbon (>90%); however, CaSO 4 ·2H 2 O(s) precipitated. Results also indicated that even if a waste heat source is available, brine disposal into the sea is the cheapest option, while ZLD alternatives were not attractive in the current regulatory framework since their cost was higher than the discharge to the sea. Other options related to the Minimal Liquid Discharge may be more economically attractive., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The most common reactive material used for the construction of a permeable reactive barrier (PRB) is zero valent iron (ZVI), however, its processing can generate corrosive effects that reduce the efficiency of the barrier. The present study makes a major contribution to understanding new reactive materials as natural and synthetic, easy to obtain, economical and environmentally friendly as possible substitutes for the traditional ZHV to be used as filters in the removal of three transition metals (Zn, Cu, Cd). To assess the ability to remove these pollutants, a series of batch and column tests were carried out at laboratory scale with these materials. Through BACH tests, four of seven substances with a removal percentage higher than 99% were prioritized (cabuya, natural clinoptilolite zeolites, sodium mordenite and mordenite). From this group of substances, column tests were performed where it is evidenced that cabuya fiber presents the lowest absorption time (≈189 h) while natural zeolite mordenite shows the highest time (≈833 h). The latter being the best option for the PRB design. The experimental values were also reproduced by the RETRASO code; through this program, the trend between the observed and simulated values with respect to the best reactive substance was corroborated.

In the recent decades, zinc (Zn) and its alloys have been drawing attention as promising candidates for bioresorbable cardiovascular stents due to its degradation rate more suitable than magnesium (Mg) and iron (Fe) alloys. However, its mechanical properties need to be improved in order to meet the criteria for vascular stents. This work investigates the mechanical properties, biodegradability and biocompatibility of Zn-Mg and Zn-Cu alloys in order to determine a proper alloy composition for optimal stent performance. Nanoindentation measurements are performed to characterize the mechanical properties at the nanoscale as a function of the Zn microstructure variations induced by alloying. The biodegradation mechanisms are discussed and correlated to microstructure, mechanical performance and bacterial/cell response. Addition of Mg or Cu alloying elements refined the microstructure of Zn and enhanced yield strength (YS) and ultimate tensile strength (UTS) proportional to the volume fraction of secondary phases. Zn-1Mg showed the higher YS and UTS and better performance in terms of degradation stability in Hanks' solution. Zn-Cu alloys presented an antibacterial effect for S. aureus controlled by diffusion mechanisms and by contact. Biocompatibility was dependent on the degradation rate and the nature of the corrosion products., Competing Interests: The authors declare no conflict of interest., (© 2021 The Authors.)

Acid mine waters (AMWs), generated in the processing of polymetallic sulphides, contain copper and zinc as the main valuable transition metal ions, which are typically removed by liming, due to their great environmental impact. In this context, this work proposes the integration of selective precipitation (SP) and ion-exchange (IX) processes for the separation and recovery of both valuable metals to encourage on-site and off-site management options promoting valorisation routes. Thus, the main objectives of this work were (i) the selective removal of Fe(III) and Al(III), using NaOH under pH control (pH < 5) to avoid the precipitation of Cu(II) and Zn(II) and (ii) the evaluation of a solvent-impregnated resin (Lewatit VP OC 1026, named VP1026) and a cation IX resin (Lewatit TP 207, named TP207) for the sequential extraction of both metal ions from AMW (batch and column experiments). Results indicated that the metallic pollution load was mostly removed during the SP process of Fe(III) (>99%) and Al(III) (>90%) as hydroxylsulphates (e.g., schwertmannite and basaluminite). The metal extraction profiles were determined for both metals from pH 1 to pH 5 by batch experiments, and indicated that the best extraction of Zn(II) was obtained using VP1026, being higher than 96% (pH = 2.6-2.8), whereas TP207 extraction performance was optimal for Cu(II) extraction (>99%) at pH = 3-4. Moreover, in dynamic experiments using a fixed-bed configuration, it was possible to separate and concentrate Zn(II) (concentration factor = 10) and Cu(II) (concentration factor = 40) using VP1026 and TP207, respectively. Overall, the integration of SP and IX processes showed a great potential in the separation and recovery of valuable metals from mine waters to promote a circular economy, based on the management proposal for non-ferrous metallurgical industries. The recovered Zn-rich and Cu-rich sulphuric concentrated streams were theoretically evaluated for further on-site or off-site re-use treatments (e.g., electrowinning, precipitation, crystallization)., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Arsenic and selenium presence in acid mine waters (AMWs) limits their disposal due to environmental regulations. The focus to solve the economic infeasibility is directed to sustainable solutions, promoting resource recovery. In fact, rare earth elements (REEs) recovery is proposed in most of the Iberian Pyrite Belt AMWs. However, the presence of arsenic and selenium may impact in the REEs recovery. Among different alternatives, nanofiltration (NF) provides a concentration stage on REEs recovery, reduces the nominal flow and removes hazardous species. In this work, Iberian Pyrite Belt AMWs with up to 10 mg/L REEs, containing arsenic (2 mg/L), were treated with a NF membrane. Firstly, AMWs were pre-treated with H 2 O 2 /NaOH, to oxidise Fe(II) to Fe(II) and As(III) to As(V), promoting their removal and avoiding their potential precipitation at the membrane. Subsequently, NF pressure effect (6-20 bar) was studied, removing metals (>95 %), whereas arsenic rejections ranged from 60 to 71 %. Then, water recovery potential was evaluated at 10, 15 and 22 bar by reproducing a 10-stages NF plant. Results showed that the proposed treatment could be an alternative for arsenic and selenium removal (70 μg/L and 0.5 μg/L permeate concentrations, respectively) to achieve mining discharge limits according to regulations., (Copyright © 2020 Elsevier B.V. All rights reserved.)

In this study, the recovery of polyphenols from olive oil mill and winery waste was investigated. The performance of ultrasound assisted extraction (UAE), microwave assisted extraction (MAE), and pressurized liquid extraction (PLE) was assessed using ethanol-water mixtures, which are compatible with food, nutraceutical, and cosmetic applications. The extraction efficiency from olive pomace and lees samples was evaluated in terms of total polyphenol content (TPC), determined by high performance liquid chromatography (HPLC) and Folin-Ciocalteu assay. The effect of solvent composition, temperature, and time was analyzed by response surface methodology. Ethanol:water 50:50 ( v/v ) was found to be a suitable solvent mixture for both kinds of samples and all three extraction techniques. The performance of the extraction techniques was evaluated, under optimal experimental conditions, with a set of different representative samples of residues from olive oil and wine production. Overall, the best extraction efficiency for olive pomace residues was provided by MAE (ethanol:water 50:50 ( v/v ), 90 °C, 5 min), and for wine residues by PLE (ethanol:water 50:50 ( v / v ), 100 °C, 5 min, 1 cycle). However, the results provided by UAE (ethanol:water 50:50 ( v / v ), 30 min) were also suitable. Considering not only extraction performance, but also investment and operational costs, UAE is proposed for a future scaling up evaluation. Regarding olive pomace as a source for natural phenolic antioxidants, olive variety and climatic conditions should be taken into account, since both influence TPC in the extracts, while for winery residues, lees from red wines are more suitable than those from white wines.

Acidic Mine Waters (AMWs) are characterised by high acidity (pH < 3) as H 2 SO 4 and elevated contents of metals (Al, Fe, Cu, Zn), including rare earth elements (REEs). Due to the exhaustion of minable REE containing-minerals, AMWs are increasingly regarded as an alternative source of REEs. Among the different alternatives for the pre-concentration of AMWs required to make the REE extraction possible, nanofiltration (NF) membranes emerge as a promising technology because they not only successfully reject multivalent ions (metals), allowing its concentration in the retentate stream, but also permit the transport of monovalent ones, such as H + and HSO 4 - , allowing the recovery of sulphuric acid in the permeate. Despite this potential of NF, there is still a lack of modelling tools for predicting the performance of NF membranes because of its dependence on solution composition, membrane properties and interaction between both. In this study, a prediction tool based on the Solution-Electro-Diffusion model (including the effect of solution composition) was developed and experimentally validated for the application of two polyamide-based NF membranes (NF270 and Desal DL) for the recovery of REEs and H 2 SO 4 from three different synthetic solutions mimicking AMWs (pH 1.0, 60 mg/L REEs and, 25-600 mg/L Al, Cu, Ca and Zn) differing in their Fe concentration (0-2125 mg/L). Metals were effectively rejected (>98%), whereas H 2 SO 4 was transported across the membrane (H+ rejections <30%). The mathematical model was able to predict the performance of both membranes as well as the potential scaling events associated with Fe and Al hydroxides and hydroxy-sulphates., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The sorption of phosphate by K-zeolites synthesized from fly ash (FA) by hydrothermal conversion is investigated in this study. The aim is the synthesis of Ca bearing K-zeolites to recover phosphate from urban and industrial wastewater effluents. The loaded zeolites are considered as a by-products rich in essential nutrients such K and P (KP1) with a potential use as slow release fertilizer. A number of synthesis conditions (temperature, KOH-solution/FA ratio, KOH concentration, and activation time) were applied on two FA samples (FA-TE and FA-LB) with similar glass content but different content of crystalline phases, to optimize the synthesis of a zeolitic sorbent suitable for the subsequent phosphate uptake. Merlinoite and W rich zeolitic products synthesized from FA-LB and FA-TE were found to have sorption properties for phosphate removal. A maximum phosphate sorption capacity of 250 mgP-PO 4 /g and 142 mgP-PO 4 /g for the zeolitic products selected (KP1-LB and KP1-TE, respectively) was achieved. The dominant phosphate sorption mechanism, in the pH range (6-9) of treated wastewater effluents, indicated that sorption proceeds via a diffusion-controlled process involving phosphate ions coupled with calcium supply dissolution from K-zeolitic products and subsequent formation of brushite (CaHPO 4 2H 2 O(s)). The phosphate loaded sorbent containing a relatively soluble phosphate mineral is appropriate for its use as a synthetic slow release fertilizer. The simultaneous valorisation of fly ash waste and the P recovery from treated wastewaters effluents, (a nutrient with scarce natural resources and low supply) by obtaining a product with high potential for land restoration and agriculture will contribute to develop one example of circularity., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The usefulness of a nutrient-enriched zeolite (NEZ) obtained from simultaneous ammonium (NH 4 + ) and phosphate (PO 4 3- ) recovery from urban wastewaters was evaluated as soil amendment through the early growth of sunflower (Helianthus annuus). The NEZ systems were applied to sandy (acid) and clayey (basic) soils from Mediterranean agricultural areas (Spain). Some plant growth indicators were measured: evapotranspiration, plant moisture content, plant biomass, root/shoot ratio, nitrogen and phosphorous uptake and the C/N ratio. The experimental data exhibited differences in the growth indicators for un-amended and amended soils. The addition of the NEZ system increase the plant water content of sunflowers grown on clay soils. The plant biomass of sunflower was improved by the incorporation of NEZ system in all treatments for the two soils studied. A reduction of the root/shoot ratio for the treatments of clay soil by application of NEZ systems were observed. The content of ammonium and phosphorous in tissues increased considerably with the addition of amendment material. Besides, the ammonium, nitrate and inorganic phosphorous in the post-test soils revealed that nutrients were still available for a second growth cycle. As demonstrated in previous work, the NEZ system releases nutrients continuously controlled by soil pH and mineral composition as well as the irrigation conditions provided. Therefore, this approach of amendment materials for soil seems to be a promising alternative for agricultural practice, where the dose selection must be balanced according to the plant's nutrient needs and soil properties by adjusting the growth conditions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)