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Reverse osmosis (RO) membrane exposure to bisulphite, chlorite, bromide and iron(III) was assessed in terms of membrane composition, structure and performance. Membrane composition was determined by Rutherford backscattering spectrometry (RBS) and membrane performance was assessed by water and chloride permeation, using a modified version of the solution-diffusion model. Iron(III) dosage in presence of bisulphite led to an autooxidation of the latter, probably generating free radicals which damaged the membrane. It comprised a significant raise in chloride passage (chloride permeation coefficient increased 5.3–5.1 fold compared to the virgin membrane under the conditions studied) rapidly. No major differences in terms of water permeability and membrane composition were observed. Nevertheless, an increase in the size of the network pores, and a raise in the fraction of aggregate pores of the polyamide (PA) layer were identified, but no amide bond cleavage was observed. These structural changes were therefore, in accordance with the transport properties observed. [ABSTRACT FROM AUTHOR]

Over the 65–100 °C range and at a water content of 1.6 kg kg −1 db, a comparison was conducted between plantain paste (dispersion made of flour and water) and pulp pieces after cooking to evaluate their respective degree of starch gelatinization (α) and in vitro digestibility. Below 76 °C and at 100 °C, the gelatinization behaviour of starch into pulp pieces and paste was similar, whereas at 85 °C a significant mean relative difference was observed in between. For α in the 0–1 range, pieces of plantain pulp exhibited a lower rapidly digestible starch fraction (30%) and a higher resistant starch fraction (33%) than the flour paste, suggesting some structural effects. Both Weibull and exponential models showed a good fit for α over temperature range and starch digestibility fractions over α. Although no explicit relationship was established between the intact pulp structure and grinded flour state of plantain, the evaluation of the degree of starch gelatinization and digestibility of a plantain flour paste, could be used to predict the gelatinization and digestibility behaviour of plantain starch in entire pieces of pulp. [ABSTRACT FROM AUTHOR]

• Acidic mine water as a valuable source of valuable metals. • Use of nanofiltration for water (or acid) recovery and metal concentration. • Metal rejections higher than 75% using Desal DK. • Design projection tools for integrating nanofiltration into treatment chains. • 0.52€/m3 for treating Acidic Mine Waters using Nanofiltration. Acid Mine Waters (AMWs) are considered the most challenging environmental problem in the Iberian Pyrite Belt (South of Spain) so far, being characterised by an acidic pH (H 2 SO 4 -based), high content of heavy metals (e.g. Co, Pb, rare earth elements (REEs)) and non-metals (e.g. As). Nowadays, AMWs are being contemplated as a source of valuable metals (e.g. Zn, Cu, REEs), and different recovery routes have been studied (e.g. ion-exchange, membrane technologies). Among them, nanofiltration (NF) provides the possibility of water (or H 2 SO 4) recovery and concentration of metals, which can be recovered in a subsequent stage. This work evaluates the performance of the Desal DK NF membrane to treat AMW from Aznalcóllar open-pit, which presents a low pH (2.6) and high contents of Zn (920 mg/L), Mg (2540 mg/L) and REEs (17 mg/L). The effect of solution pH on membrane performance was evaluated. Results showed that the equilibrium SO 4 2-/HSO 4 - controlled the transport of species. Rejections of sulphate were around 84 % at pH 2.1 (prevalence of HSO 4 -) and increased to 92 % at pH 3.1 (prevalence of SO 4 2-). Metal rejections remained higher than 74 % (except for monovalent species). Additionally, membrane permeances were determined using the Solution-Electro-Diffusion model coupled with reactive transport, and later used to assess the design of the process treatment of the AMW. Results demonstrated the possibility of concentrating metals and recovering H 2 SO 4 as permeate, but also showed that gypsum and anhydrite precipitation can occur. Additionally, CAPEX and OPEX were estimated for a NF plant treating 2 Hm3/year. [ABSTRACT FROM AUTHOR]

The effect of temperature ( T = 55–120 °C) and water content ( X 1 = 1.4–2.0 kg kg −1 dry basis) on the gelatinization and digestibility of plantain flour (Dominico Harton genotype) were investigated. The degree of plantain starch gelatinization ( α ) was measured by DSC and modelled as a function of T and X 1 , using the Weibull model. Rapidly digestible starch ( RDS ) and resistant starch ( RS ) fractions were evaluated for different α values. An appropriate dimensionless variable was introduced to the analyzed and modelled RDS and RS as a function of α . Starch gelatinization begins at a temperature above 59.6 ± 0.5 °C and α is strongly dependent on T in non-limiting water conditions. The combined effects of T and X 1 on the RDS and RS can be explained by α . We demonstrate that various heat treatments and water contents lead to the same α , with the same RDS and RS values. [ABSTRACT FROM AUTHOR]

Water activity is the main criterion for characterizing the storage and drying behavior of biological products. As current standardized devices are expensive, a cheaper apparatus was designed and built. After preliminary tests, functional specifications were determined. This gravimetric device was tested and validated on microcrystalline cellulose and then used for the characterization of various tropical products. This operational equipment, easy to handle, robust, and four times cheaper than the reference apparatus, was able to obtain accurate sorption isotherms. [ABSTRACT FROM AUTHOR]

• Mining and hydrometallurgical industries as large generators of acidic liquid wastes. • Current management options do not contemplate their valorisation. • Membrane technologies provide resource recovery options. • New membranes with enhanced properties for long-term industrial operation. The mining and hydrometallurgical industries generate effluents characterised by a high acidity (pH < 3) and a high content of metals (e.g. Fe, Al, Cu and Zn, among others) and non-metals (e.g. As, Sb, Bi), which confers them toxicity that makes necessary their treatment. The conventional treatments of such streams mainly rely on neutralisation/precipitation, solvent extraction, ion-exchange and adsorption. However, these options are often not feasible because of their high consumption of chemicals and the generation of large volumes of sludge. On the other hand, due to the exhaustion of natural resources, circular economy schemes are increasingly promoted for the recovery of valuable elements (e.g. Cu, Zn, rare earth elements) from waste effluents as an alternative to mining the already over-exploited mine sites. Within this new paradigm, the integration of membrane technologies are gaining importance for the valorisation of such effluents since they provide the possibility of: i) reducing the volume of the streams to be treated, ii) favour the selective separation of metal ions from acids, and, iii) the concentration of metals in acidic streams. Membrane technologies are promoting the recovery of valuable dissolved components and the reuse of the acid, reducing the generation and disposal of sludge. Among the different membrane technologies, nanofiltration (NF), diffusion dialysis (DD), reverse osmosis (RO), electrodialysis (ED), forward osmosis (FO) and membrane distillation (MD) are the most promising ones to tackle these challenges and promote circularity. [ABSTRACT FROM AUTHOR]

• Valorisation of acidic waters using nanofiltration (NF) in the Cu industry. • Characterisation of Duracid membrane as polysulphonamide. • High metal rejections (>85%) and acid recovery (rejection below 40%) with Duracid. • Precipitation of calcium and iron sulphates during the process. • Use of SEDF model as a designing tool for scaling-up. The exhaustion of Cu reserves minable and processable with the available technology is forcing the hydrometallurgical copper industry to seek alternative sources. Following circular economy principles, researchers' attention has focused on the recovery of valuable metals from the acidic waste streams generated. Nowadays, membrane technologies are being selected as the first alternative for the treatment and valorisation of such acidic waste streams. Among them, a new generation of high acidity resistance nanofiltration (NF) membranes offer the alternative for acid recovery while providing a metal-enriched stream. In this work, the extreme-acid resistant Duracid membrane was evaluated for the valorisation of different synthetic acidic waste streams from the hydrometallurgical Cu industry. These waters were characterised by a high acidity (pH 0.5–1.5) and the presence of Fe (11–14 g/L), Zn (0.7–1.4 g/L) and As (0.5–0.7 g/L), among others. Initially, the membrane was characterised by different techniques (SEM, FTIR-ATR, XPS). Experiments were performed under constant and varying permeate flux and feed water composition. Metals were effectively rejected (>90%), whereas H+ easily permeated through the membrane. The experimental results were adjusted to the Solution-Electro-Diffusion-Film (SEDF) model to determine the membrane permeances to species. Empirical mathematical equations were developed and validated to express the dependence of permeances on solution composition. Finally, the prediction capability of the SEDF model, together with the developed empirical equations for the permeances, was proposed as a tool for designing a NF unit to valorise acidic streams from the hydrometallurgical Cu industry. The model predicted gypsum scaling onto the membrane and therefore anticipated the need of applying antiscalants. [ABSTRACT FROM AUTHOR]

• Hydrometallurgical wastewaters as a potential source for chemicals recovery. • Nanofiltration membranes for acid recovery. • Use of Solution-Electro-Diffusion model to determine membrane permeances. The metallurgical industry generates large volumes of toxic effluents characterised, generally, by high acidity and a noticeable content of metals (Fe, Cu and Zn) and non-metals (As, Sb, Bi). The toxicity of these streams makes necessary treatment before its discharge to the environment or reuse. Sustainable management of these effluents must be focused on the recovery of low added valuable by-products (e.g. strong acids) to reduce the wastes generated along with the treatment (e.g. sludge). Nanofiltration offers clear advantages for acid recovery instead of the conventional treatments such as neutralisation and precipitation, due to the high membrane transport ratios of single charged ions and high rejection of multi-charged ions. The performance of a semi-aromatic poly(piperazineamide) membrane (NF270) was evaluated for the treatment of effluents from copper metallurgical process streams of off-gases treatment trains. These streams are characterised by a high acidity (pH < 1) due to a mixture of strong (H 2 SO 4 , HCl) and weak (H 3 AsO 4) acids and the presence of metallic species (Fe, Cu, Zn). The membrane performance was evaluated in terms of acid recovery and metal ions rejection taking into account their aqueous speciation in strong acid media. The transport of the species across the membrane was characterised according to the Solution-Electro-Diffusion model. The membrane permeances to aqueous species (both charged and non-charged) in strongly acidic solutions were calculated. NF270 showed good results for strong acid recovery, exhibiting high rejections of the metallic impurities. The implications of the presence of large amounts of As present as H 3 AsO 4 should involve a selective removal stage using H 2 S or Na 2 S 2 O 3. [ABSTRACT FROM AUTHOR]

Highlights • Acidic mine waters as a potential source for chemicals recovery. • Nanofiltration membranes for metal and acid recovery. • Study of the effect of Fe concentration on membrane separation performance. • Use of Solution-Electro-Diffusion model to determine membrane permeances. Abstract Acidic mine waters (AMWs) contain, in addition to moderate concentrations of sulphuric acid, relatively high concentrations of transition elements (e.g. Fe, Al, Cu, Zn) and, in some cases, minor amounts of valuable rare earth elements (REEs). The established management routes for AMWs, based on the neutralisation and metal stabilisation as hydroxides, are limited by the associated costs, such as reagent consumption. Nanofiltration (NF)-based treatment processes could improve these management routes by recovering the sulphuric acid and simultaneously increasing the concentration of valuable elements (e.g. Zn, Cu and REEs) for further valorisation after the proper removal of Fe. Three different types of NF membranes with (a) a poly(piperazinamide) active layer (NF270), (b) a double active layer (poly(piperazinamide)/proprietary polyamide) (Desal DL) and (c) a sulphonated poly(ethersulphone) active layer (HydraCoRe 70pHT) were evaluated. The influence of Fe(III) concentration on the sulphuric acid recovery from solutions at pH 1 was characterised. NF270 showed the higher permeate fluxes and the higher heavy and REE metal rejections (i.e. the higher concentration factors). As the Fe(III) concentration increased, higher acid permeation was obtained, which helped to decrease the neutralisation costs during its post-treatment. The membrane chemistry of the active layer (nature and acid-base membrane properties) and structure (single/double layer) were found to be strong parameters in the membrane separation performance. Ion transport data were modelled according to a Solution-Electro-Diffusion model coupled with Ion Reactive Transport and the membrane permeances to ions were determined. [ABSTRACT FROM AUTHOR]

Abstract Acid mine waters (AMWs) are characterized by a low pH, high concentrations of transition metals (iron, copper, zinc), and the presence of highly valuable metals such as rare earth elements (REE) at lower concentrations. Sustainable management of AMW implies the reduction of acidity and Fe/Al concentrations and the recovery of valuable metals by ion-exchange processes. Nanofiltration (NF) offers a good opportunity compared to conventional methods to treat AMW, such as good passage of mono-charged ions (e.g. hydrogen sulphate, proton) for further recovery of sulphuric acid and high rejection of multi-charged ions, such as transition metals and REE. Two membranes with a different active layer, a double membrane (poly-piperazinamide/proprietary polyamide) (Desal DL) and a sulphonated polyethersulphone (HydraCoRe 70pHT), were evaluated with a solution mimicking acidic streams generated after the removal of iron by precipitation and its subsequent treatment with ion-exchange resins. The recovery of sulphuric acid and metal rejections were evaluated by changing the sulphuric concentration/pH (1.0–1.5) and by varying the concentration of aluminium in the solution (0.6–2.2 g/L). The transport of ions through NF membranes was described according to the solution-electro-diffusion model coupled with reactive transport of ions, and the membrane permeances to ions were determined as a function of aluminium concentration. Desal DL showed better results than HydraCoRe 70pHT in terms of acid recovery and metal rejections for both tested conditions. Membrane chemistry of the active layer (nature and acid-base membrane properties) and chemical speciation were found to be strong parameters in the separation performance of the membranes. Finally, a process scheme for recovering the REE is proposed. Highlights • Acidic mine waters as a potential source for rare earths elements recovery. • Evaluation of nanofiltration metals for the treatment of acid mine waters. • Study of the effect of aluminium concentration on metal rejection and acid passage. • Determination of membrane permeances by means of solution-electro-diffusion model. • Proposal of a nanofiltration stage in a process for rare earths recovery. [ABSTRACT FROM AUTHOR]

A better understanding of starch-process interactions is the key point to better control banana starch digestibility and degree of cooking. This study aims at investigating and modelling the evolution of both the degree of cooking and in vitro digestibility of plantain starch as a function of steeping conditions. A 2D-axial-symmetric model considering a single Harton plantain cylinder being steeped in water was developed and adjusted to experimental data collected at 25, 50, 75 and 100 °C. Experimental temperature distribution was well predicted, with a thermal diffusivity of 1.5 × 10 −7 m 2 s −1 . The model was also validated against degree of starch gelatinization kinetics obtained by DSC at 100 °C. Two modes of water transport were found, depending on the starch state. At 25 °C or high degree of starch gelatinization ( α ≥ 0.38), molecular diffusion was observed with an apparent water diffusivity of 2.4 × 10 −9 m 2 .s −1 , which may be due to structural cellular effects. At 50 °C, capillary diffusion was observed due to gas desorption, with an apparent water diffusivity of 10 × 10 −9 m 2 .s −1 . Starch digestibility was governed by gelatinization process which strongly depends on heat transport. This approach could be used to identify some steeping conditions that modulate both banana starch digestibility and degree of starch gelatinization. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) are acidic streams rich in dissolved ferrous and non-ferrous metal sulfates and minor amounts of non-metals. Nanofiltration (NF) has been postulated as a potential technology in the metallurgical and mining industry to recover strong acids as H 2 SO 4 and concentrate metallic ions from acidic mine waters. The performance of semi-aromatic polyamide (NF270) and sulfonated polyethersulfone (HydraCoRe 70pHT) NF membranes were evaluated at different trans-membrane pressures. Different synthetic solutions were filtered under spiral wound configuration at two pHs (2.0 and 2.8): i) a solution of Na 2 SO 4 and ii) a solution mimicking AMD from dams, containing Na 2 SO 4 and Fe 2+ , Zn 2+ and Cu 2+ . NF270 showed metal rejections higher than 90%, while for HydraCoRe 70pHT they were in between 60 and 70%. Metal rejection values decreased when solution acidity was increased. Chemical composition of the membrane active layer and the aqueous metal-sulfate speciation were found to have a large impact on membrane separation process. Solution-Electromigration-Diffusion-Film model was used to estimate the membrane permeances to ions from the measured ion rejections. Furthermore, a full scale unit vessel containing six spiral wound membrane modules was simulated. NF270 showed a higher capacity for concentrating metal and sulfate ions (100%) than Hydracore 70pHT (50%). [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) is considered the main environmental problem in mining operation due to its acidity, metal content (Fe, Al, Zn, Cu) and onerous associated treatment cost. However, the presence of relatively high levels of added value elements (rare earth elements (REE)) could make its valorisation economically affordable. Membrane nanofiltration (NF) has been postulated as a potential recovery technology because it allows the recovery of a sulphuric acid rich stream and a metal rich stream in one step. In this study, the performance of a semi-aromatic polyamide NF membrane (NF270) in filtering model solutions containing common metals (Ca, Al, Zn) in sulphuric solutions (pH 1.5–3.0) was evaluated. In a second stage, the performance was assessed with the same model solutions but also containing REE. NF270 showed high rejections for metallic ions in solution, allowing acid permeation. Ion rejection data were used to determine membrane permeances to ions using the solution-diffusion model considering reactive transport. The stability of the membrane was also studied by comparing performances of a virgin membrane with an aged membrane exposed to 1 M sulphuric acid for 4 weeks. Physicochemical changes of membrane properties after ageing were also analysed by ATR-FTIR, AFM and XPS. [ABSTRACT FROM AUTHOR]

The feasibility of continuous phosphate recovery, by adsorption on powdered Ca-activated zeolite (PAZ), was assessed in a hybrid sorption-membrane ultrafiltration (UF) system. The objective was to explore the influence of process parameters such as initial P(V) concentration, pH, and PAZ dose on P(V) recovery from a tertiary treatment effluent. The hydrodynamic parameters of the UF operation were also evaluated as a function of the PAZ dose. The P(V) recovery profiles as a function of the initial P(V) concentrations, at pH 8 and 2.5 gPAZ/L, indicated that the sorbent was not saturated, and recoveries reported were 1.8 ± 0.2, 5.7 ± 0.3, and 47.2 ± 2 mg P(V)/gPAZ for 10 ± 1, 25 ± 2, and 100 ± 6 mg P(V)/L, respectively. The increase of the pH of the feed solution from 8 to 9 increased the P(V) recovery up to 70 ± 4%. A P(V) fractionation protocol of the loaded samples confirmed that the phosphate-sorption process involves the formation of calcium phosphate mineral forms. [ABSTRACT FROM AUTHOR]

Nanofiltration (NF), as a selective Mg(II) and Ca(II) separation and concentration treatment, and electrodialysis with bipolar membranes (EDBM) were evaluated for the valorization of seawater desalination reverse osmosis brines (60 NaCl/L) to produce both rich Mg(II) and Ca(II) brines for phosphate recovery and HCl and NaOH as chemicals for desalination treatments. A NF pilot plant, using NF270 membranes at 20 bar, provided a rich Mg(II) (8.3 g Mg(II)/L) and Ca(II) (2.1 g Ca(II)/L) brine on the concentrated stream with enrichment factors of 3.2 for Mg(II) and 2.5 for Ca(II). The NF permeate stream containing 50 ± 2 g NaCl/L was treated to remove residual Mg(II) (760 mg/L) and Ca(II) (415 mg/L) by chemical precipitation with Na 2 CO 3 and NaOH before the EDBM unit. Divalent cations free brine containing NaCl (50 g NaCl/L) were fed into the EDBM stack in order to produce NaOH and HCl under recirculation configuration. Constant voltage and acid and base concentrations at different initial conditions were evaluated to obtain the maximum acid and base concentration (approximately 1 M NaOH/HCl) at 9 V. No substantial effect of initial acid and base concentrations on the overall performance was observed. An energy consumption of 2.6 kWh/kg NaOH and current efficiency of 77 ± 3% were calculated. [ABSTRACT FROM AUTHOR]

Seawater mining is certainly a green alternative source for obtaining minerals as seawater is a natural renewable and unlimited available resource. Based on the lack of ways to obtain certain raw materials, the European Union has created the Critical Raw Materials (CRM) list. Seawater contains almost all elements, including some of those present in the CRM list, but only a few are economically feasible to be extracted as most of them are considered Trace Elements (TEs) (μg L−1). Therefore, an improvement in TEs extraction must be carried out. Saltwork brines can be considered as they are naturally concentrated (20–40 times) compared to seawater, which makes the extraction and recovery of TEs easier. Selective polymeric and inorganic sorbents were evaluated for TEs recovery (Li, B, Co, Ga, Ge, Rb, Sr, and Cs) from synthetic brines mimicking sea saltwork bitterns. Distribution coefficients were determined to characterize selectivity patterns toward TEs. Although amine and sulphonic sorbents showed low sorption of TEs, carboxylic sorbents presented good sorption and recovery for Co and Ga. Among phosphonic/phosphinic sorbents, MTX8010 achieved >98% sorption and desorption of Ga. Aminophosphonic and iminodiacetic are the best sorbents for Sr, but its desorption was incomplete. B was only sorbed by N-Methylglucamine (>98%) and N-Methylpyridine sorbents (75%), and its desorption was 37–64% and 66−>99%, respectively. SbTreat presented good performance targeting Ga and Ge, and CsTreat demonstrated high Cs uptake, but its desorption was unachieved. The most highly selective sorbents could provide the possibility of building a green option to recover critical elements for societal development in the next decade. [ABSTRACT FROM AUTHOR]

• Feed and acid stripping inputs were optimized as shell and lumen sides respectively. • It was better to work with the module in vertical position regardless of acid used. • Higher ammonia recovery was achieved, increasing the acid stripping flow rate. • 96% NH 3 recovery and 4.6% N in the liquid fertiliser were obtained by 2 LLMC-1 step. • Treated ammonia stream, rich in NaOH, could be reused in zeolite regeneration step. The transformation of wastewater treatment plants (WWTPs) to resources recovery plants (nutrients and energy) is forcing the development of specific technologies for selective recovery. Ion-exchange and hollow fibre liquid-liquid membrane contactors (HF-LLMCs) appeared as promising technologies to reduce operation costs, at ambient temperature, on the N-recovery from main-streams of urban WWTPs. A concentrated ammonia stream (4.5 g/L), recovered from treated wastewater using zeolites and NaOH, was used to test different operational parameters on the performance of the HF-LLMC process for ammonia recovery. These tested parameters were HF-LLMC position (horizontal and vertical), HF-LLMC feed and acid streams inputs (shell and lumen), type of acid stripping solution (0.4 M H 3 PO 4 and 0.4 M HNO 3), membrane drying, flow rate for each stream (263–770 mL/min), number of steps (1 and 2) and number of membrane contactors (1 and 2 in series). The maximum ammonia recovery (>95%) was achieved by a one-step configuration using two vertical membrane contactors in series; using the shell side for feed stream and the lumen side for the acid stripping solution (HNO 3); at 450 mL/min and 770 mL/min flow rates for feed and acid stripping solutions, respectively. The liquid fertiliser composition obtained was around 4.6% N (from NH 4 +). Additionally, the ammonia treated stream, rich in NaOH, had residual levels of NH 3 (about 200 mg/L) that could be reused for the regeneration of the zeolites. This optimized HF-LLMC process allowed to recover ammonia from a tertiary treatment solution of an urban WWTP and at the same time to produce ammonium salts that could be used as liquid fertilisers in irrigation applications. Therefore, this technology promotes the circular economy concept for nutrient recovery in urban WWTPs. [ABSTRACT FROM AUTHOR]

The accumulation of ammonia in water bodies can cause eutrophication and reduce water quality. Furthermore, 80% of the ammonia in the world is consumed as fertilizer, which makes it a resource that can be recovered under the circular economy concept. Then, ammonia from wastewater can be valorised for agricultural applications. Liquid-liquid membrane contactors (LLMCs) have been postulated as a novel and eco-friendly technology for ammonia recovery, because they can convert dissolved ammonia into ammonium salts by an acid stripping solution. The concentration of the ammonium salt produced is limited by the co-transport of water in LLMC. Further concentration by electrodialysis (ED) is presented as a solution to overcome this problem. In this work, ammonia streams with different initial ammonia concentrations (1.7–4.0 g/L) were treated by LLMCs to produce liquid ammonium salt fertilizers (as NH 4 NO 3 and NH 4 H 2 PO 4). Then, these ammonium solutions were concentrated by ED in order to achieve the nitrogen content required for direct application in agriculture for fertigation. After the LLMC process, the fertilizer obtained was composed of approximately 5.1% or 10.1% (w/w) nitrogen, depending on the initial ammonia concentration. After that, it was possible to concentrate these ammonium salts by a factor of 1.6 ± 0.3 using ED with an optimal energy consumption of 0.21 ± 0.08 kWh/kg ammonium salt and 93.1 ± 4.2% of faradaic yield. This gave a liquid fertilizer composed of 15.6% (w/w) nitrogen as NH 4 NO 3. Overall, it was possible to integrate two innovative membrane technologies for the valorisation and concentration of nutrients from ammonia wastewater streams. Image 1 • Ammonia is a non-environmental friendly specie since it could cause eutrophication. • LLMC can convert ammonia into ammonium salts by using an acid stripping solution. • Ammonium salts can be used as liquid fertilizers due to its N content. • Ammonium salts were concentrated by ED to achieve N fertilizers requirements. • LLMC + ED integration was used to valorize and concentrate nutrients from wastewater. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Activated carbon was used to remove DOM and reduce fouling before HF-LLMC process. • Ammonia-rich streams, from a zeolites regeneration step, were treated by HF-LLMC. • One/two-steps HF-LLMC configuration were tested using different stripping solutions. • H 3 PO 4 was the best acid stripping solution by two-step HF-LLMC removing 94% ammonia. • Ammonia was recovered as a multi-nutrient liquid fertilizer (7.8% N and 21.6% P 2 O 5). Abstract The nitrogen load on urban wastewater should be considered as a secondary resource for nitrogen-based fertilizers. From this point of view, ammonia-rich streams obtained from a regeneration step with zeolites using 70–80 g NaOH/L could contain up to 3.5–4.5 g NH 3 /L as well as other ionic species (Na+, K+, Ca2+, Mg2+) and dissolved organic matter (DOM). Thus, they could be treated to obtain a valuable product composed by ammonia for fertilizing applications. A sorption pre-treatment process was carried out to remove the residual amount of DOM and to reduce membrane fouling before processing with hollow fibres liquid-liquid membrane contactors (HF-LLMC). Polypropylene HF-LLMC was used to selectively extract ammonia in single or two-step configurations using different acid stripping solutions (H 3 PO 4 , HNO 3 or a mixture of HNO 3 /H 3 PO 4). For ammonia recovery, the ammonia mass transfer coefficient (K m (NH 3)) and water transport by HF-LLMC were determined. H 3 PO 4 was found to be the best acid stripping solution by one-step HF-LLMC; the ammonia removal was 76% with a K m (NH 3) of 8.8 × 10−7 m/s. Additionally, the ammonia was concentrated 26 times, and it was recovered as multi-nutrient liquid fertilizer (NP) composed of 7.8% N and 21.6% P 2 O 5. Furthermore, ammonia recovery was increased, reaching values up to 94%, through two-step HF-LLMC, and again H 3 PO 4 was used as stripping solution. Finally, water transport from the feed to the stripping phase was estimated to be 0.022 L/m2·h for one-step HF-LLMC with H 3 PO 4. Finally, the use of UV–Vis and 2D-Fluorescence was shown to be a successful approach for monitoring pore wetting events. [ABSTRACT FROM AUTHOR]

In this work, selectrodialysis (SED) was used to separate arsenic (As(V)) from copper (Cu(II)) and zinc (Zn(II)) of acidic metallurgical process streams by integrating non-selective and selective membranes. The separation process is determined by the chemical speciation of the involved elements. In this case, As(V) is mainly present as anionic species (H 2 AsO 4 − ), while Cu(II) and Zn(II) are mainly present as cationic species although partially complexed as neutral complexes (CuSO 4 and ZnSO 4 ). A lab set-up was used to conduct the experimental tests with different type of standard and monovalent selective ion-exchange membranes. The results obtained showed that by SED configuration it was possible to recover around 80 ± 0.2% of Cu(II), 87 ± 0.2% of Zn(II) and 95 ± 0.3% of As(V) from the feed solution to the rich-product streams with an energy consumption of 2.6 ± 0.2 kWh/kg CuSO 4 +ZnSO 4 . Furthermore, a Cu/Zn-rich stream with a purity of both divalent cations of 99.8% (0.02% of As(V)) was achieved by means of SED. Overall, the results herein gathered suggest that SED is an efficient separation technology for Cu(II) and Zn(II) recovery from mining and metallurgical acidic streams. [ABSTRACT FROM AUTHOR]

The decrease of water quantity and quality in water scarcity areas is palliated by improving water treatments with membrane technologies. System performance and efficiency, and then cost, is mainly affected by membrane fouling, which is still not well understood and controlled appropriately. In this study, the influence of content and composition of dissolved organic matter (DOM) on a membrane ultrafiltration (UF) stage from a full-scale UF stage in a drinking water treatment plant (DWTP) fed with surface water, groundwater (or blends of them) was investigated. Excitation-emission matrix (EEM) fluorescence spectroscopy coupled with parallel factor analysis (PARAFAC) was used to characterize and assess DOM changes in water samples Water streams feeding the UF stage showed high variability in DOM content and composition. FEEM-PARAFAC analysis allowed the differentiation of seven different organic components. Additionally to the characterization and monitoring of DOM in the full-scale UF stage, a bench scale UF pilot was run to experimentally correlate the impact of water quality with membrane performance. The experiments included testing synthetic solutions of model foulants (synthetic humic acid and bovine serum albumin) and blends of complex waters. To quantify fouling, the total fouling index (TFI) and the hydraulically irreversible fouling index (HIFI) were calculated for each filtration run. According to the results obtained, the correlation plots between the PARAFAC components and the fouling indices pointed at microbial byproducts (C1) and humic-like components (C2, C4, C5) as the ones showing higher correlations. [ABSTRACT FROM AUTHOR]

Fluorescence excitation emission matrix (FEEM) spectroscopy was used to evaluate its applicability as a tool to track dissolved organic matter (DOM) in a drinking water treatment plant (DWTP) that incorporates a conventional line (consisting in ozonation and GAC filtration) and a membrane-based line (consisting in ultrafiltration, reverse osmosis and mineralization) working in parallel. Seven sampling points within the different process stages were characterized monthly during 2014. A global Parallel Factor Analysis (PARAFAC) was used to pull out underlying organic fractions from the fluorescence spectra. Accordingly a five components model was selected to describe the system and the pros and cons of the model were discussed by analysis of the residuals. Among the five fluorescent components, those associated to humic-like matter (C1, C3 and C4) showed a similar season variability in the river water feeding the DWTP (which resembled that of UV 254 and TOC), whereas the two components associated to protein-like matter (C2 and C5) exhibited a different behavior. The maximum fluorescence intensity values (Fmax) were used to quantify DOM removals across the plant. Compared to the conventional line, water from the UF/RO membrane-based line showed between 6 and 14 times lower fluorescence intensity signal for the humic-like components and between 1 and 3 for the protein-like components as compared to the conventional line. The differences in DOM composition due to seasonal variations and along the treatment trains point out the suitability of using fluorescence measurements over other parameters such as UV 254 as a monitoring tool to help optimize operation conditions of each treatment stage and improve produced water quality in a DWTP. [ABSTRACT FROM AUTHOR]

Water scarcity in the Mediterranean basin has been solved by using seawater desalination reverse osmosis technology (SWD-RO). This technology produces brine which is discharged back into the sea resulting in an environmental impact on marine ecosystems. Under the circular economy approach, the aim of this work is to recover resources from NaCl-rich brine (~ 60–70 g/L), e.g. in the form of NaOH and HCl, by integration of two ion exchange-based membrane technologies and quantify the electrical energy consumption. Electrodialysis (ED) incorporating monovalent selective cation exchange membranes as divalent ions purification and concentration of the NaCl present in the SWD-RO brine, was integrated with bipolar membrane ED (EDBM) to produce NaOH and HCl. Current densities of 0.30–0.40 kA/m 2 at two temperature ranges simulating different seawater temperature regimes (15–18 °C and 22–28 °C) were tested and a pure NaCl solution was used as starting concentrate stream. NaCl-rich brines with 100 or 200 g NaCl/L were obtained by ED and then introduced in the EDBM stack producing HCl and NaOH up to 2 M, depending on the initial concentrations. A minimum energy consumption of 1.7 kWh/kg NaOH was calculated when working by EDBM with initial concentrations of 104 g NaCl/L and 0.24 M HCl and NaOH. [ABSTRACT FROM AUTHOR]

• Stringent regulations related to low phosphorous concentrations in wastewater. • Need for seeking alternative sources for phosphrous. • Use of nanofiltration membranes for phosphorous concentration. • Recovery of phosphorous as struvite from secondary treatment effluent. The more stringent regulations related to the reduction of residual phosphorous concentration in treated wastewater and the consideration of phosphorous as a critical raw material are boosting new technologies towards its recovery from waste effluents. The concentration of phosphate in these effluents can be easily increased using nanofiltration (NF) due to its high phosphate rejections (>99%) in order to recover it as a raw material for the fertilizer industry. In this work, different model solutions were used to characterise the transport of phosphate species across a semi-aromatic polyamide membrane (NF270) using the Solution-Electro-Diffusion-Film coupled with reactive transport (SEDFRT) model. Experiments were carried out with waters containing one dominant salt (NaCl or Na 2 SO 4) and one trace salt (dihydrogen or hydrogen phosphate salts) to easily determine membrane permeances to species without simulating the complexity of real solutions. Besides, for the first time the transport of H+ and OH– was also modelled. Results showed a high performance of NF270 when separating phosphate (rejections higher than 90%). Finally, the obtained permeances were used to evaluate the recovery capacity of phosphate as struvite from a model secondary treatment effluent through the SEDFRT model. Results demonstrate the potential of NF as a step forward towards closing the urban phosphorus cycle. [ABSTRACT FROM AUTHOR]

Aims: To investigate the distribution of a polymicrobial community of biodegradative bacteria in (i) soil and groundwater at a former manufactured gas plant (FMGP) site and (ii) in a novel SEquential REactive BARrier (SEREBAR) bioremediation process designed to bioremediate the contaminated groundwater. Methods and Results: Culture-dependent and culture-independent analyses using denaturing gradient gel electrophoresis (DGGE) and polymerase chain reaction (PCR) for the detection of 16S ribosomal RNA gene and naphthalene dioxygenase (NDO) genes of free-living (planktonic groundwater) and attached (soil biofilm) samples from across the site and from the SEREBAR process was applied. Naphthalene arising from groundwater was effectively degraded early in the process and the microbiological analysis indicated a dominant role for Pseudomonas and Comamonas in its degradation. The microbial communities appeared highly complex and diverse across both the sites and in the SEREBAR process. An increased population of naphthalene degraders was associated with naphthalene removal. Conclusion: The distribution of micro-organisms in general and naphthalene degraders across the site was highly heterogeneous. Comparisons made between areas contaminated with polycyclic aromatic hydrocarbons (PAH) and those not contaminated, revealed differences in the microbial community profile. The likelihood of noncultured bacteria being dominant in mediating naphthalene removal was evident. Significance and Impact of the Study: This work further emphasizes the importance of both traditional and molecular-based tools in determining the microbial ecology of contaminated sites and highlights the role of noncultured bacteria in the process. [ABSTRACT FROM AUTHOR]

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. Unlabelled Image • Acidic mine waters as a potential source for chemicals recovery • Nanofiltration membranes for acid recovery and metal concentration • A numerical algorithm as a design tool for NF based separation processes • Use of Solution–Electro–Diffusion model to predict nanofiltration performance • Dependence of membrane permeances to species on solution composition [ABSTRACT FROM AUTHOR]

• Nanofiltration membranes for acid recovery and metal concentration from acidic streams. • Need of resistant nanofiltration membranes in acidic media. • Evaluation of ceramic (TiO 2) and polymeric (MPF–34) acid-resistant membranes. Acid-resistant ceramic and polymeric nanofiltration (NF) membranes have been identified as relevant materials for sustainable management of acidic streams. NF properties such as a high passage of single-charged ions and high rejection of multi-charged ions make NF membranes suitable for acid recovery and metal concentration. In this work, the performance of two acid-resistant membranes: TiO 2 ceramic and MPF–34 (proprietary layer) was tested with solutions mimicking acidic mine waters. Model solutions were composed by Al(III), Fe(III), Ca(II), Cu(II), Zn(II) and rare earth elements (REEs(III)) such as La(III), Dy(III), Sm(III), Nd(III), Pr(III) and Yb(III). The effect of acidity (from pH 1.5 to 1.0), Al(III) (from 0.6 to 1.8 g/L) and Fe(III) (from 0.5 to 2.1 g/L) concentrations was studied. Both membranes allowed the transport of H+ (negative rejections were obtained), but exhibited differences related to the metallic ions transport. While MPF–34 presented metal rejections around 80% and independent on the concentration of the major components (Al(III) and Fe(III)), the TiO 2 membrane provided a sequence of rejection values from 5 to 30%, with highest values for trivalent transition metals. These differences in the sequence of rejections suggested that the chemical properties of the TiO 2 layer played a relevant role, and that they could only be explained by dielectric effects. From the observed rejections, it was estimated that MPF–34 provided concentration factors for metals up to 4.2 and <1 for the H 2 SO 4. [ABSTRACT FROM AUTHOR]

• Zn(II) and Cu(II) were valorized from non-ferrous hydrometallurgy streams by SED+IX. • Arsenic(V) separation from Zn(II) and Cu(II) acidic effluents was conducted by SED. • Selective separation of Zn(II) from Cu(II) using impregnated IX resins was done. • Lewatit VP OC 1026 resin showed better Zn(II)/Cu(II) separation than Purolite S960. • By IX resins it was possible to concentrate Zn(II) 30 and Cu(II) 23 times. The main challenge for copper smelters is to ensure product quality under the constant increase in impurities (As, Se, Mo, Co, Zn, Sb, and Pb) in copper ores that has occurred over the years. The presence of toxic elements, such as As(V), in acidic streams rich Cu(II) and Zn(II) (pH 2.0–2.5) limits the valorisation of both metals. In this study, a novel combination of the following two ion-exchange-based processes were proposed: i) membrane selectrodialysis (SED) for the selective separation of Zn(II)/Cu(II) from As(V) and ii) solvent-impregnated ion-exchange (IX) resins for the selective separation of Zn(II) from Cu(II). The selective separation of As(V), which is present in solution as H 3 AsO 4 /H 2 AsO 4 –, is achieved using a combination of monocharge and non-monocharge selective cation-exchange membranes to avoid the co-precipitation of As(V) when IX resins are used for Cu(II)/Zn(II) recovery. This combination of processes represents the novelty of the present study since it could be used in hydrometallurgical industries to remove As(V) and, at the same time, to valorize two value-added metals [Cu(II) and Zn(II)]. At the moment, only single-stage processes have been proposed. Using SED, a Cu(II)/Zn(II)-rich stream [97 ± 2% Cu(II) and 82 ± 3% Zn(II)] was obtained, and 60 ± 4% of As(V) was removed from the initial feed stream. Then, the separation of Zn(II) from Cu(II) was proposed using Lewatit VP OC 1026 resin at pH = 2.2 and 4.3, respectively. In this IX resin process, it was possible to recover 70 ± 3% of Zn(II) and 98 ± 2% of Cu(II) and to concentrate Zn(II) and Cu(II) around 30- and 23-times, respectively. [ABSTRACT FROM AUTHOR]