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Photovoltaic (PV) panels have a crucial role in coping with the global warming mitigation and the energetic crisis currently affecting the European Community. However, from the circular perspective of end-of-life (EoL) management, there are still big issues to be solved in order to recover materials from this kind of e-wastes. Because of several reasons (e.g. type of embedded materials, illegal shipments, location of manufacturers) EoL businesses do not have the interest in approaching them. This poses a significant environmental concern in terms of their management. This work wants to assess the profitability of a specific PV module recycling plant, by evaluating several market contexts in which multiple scenarios of material price, investment and process costs will be considered. The results for a 3000 tonnes plant show that profitability is not verified in the absence of an avoided landfill cost. Instead, when a value of 200 €/tonnes is applied, the net present value is positive in 35.2% of the scenarios and at 87.6% when a value of 350 €/tonnes is considered. The policy choice of this value requires linking the PV module disposal fee to the circular benefits associated with its recovery.

Purpose This PRISMA-compliant systematic review aims to analyze the existing applications of artificial intelligence (AI), machine learning, and deep learning for rhinological purposes and compare works in terms of data pool size, AI systems, input and outputs, and model reliability. Methods MEDLINE, Embase, Web of Science, Cochrane Library, and ClinicalTrials.gov databases. Search criteria were designed to include all studies published until December 2021 presenting or employing AI for rhinological applications. We selected all original studies specifying AI models reliability. After duplicate removal, abstract and full-text selection, and quality assessment, we reviewed eligible articles for data pool size, AI tools used, input and outputs, and model reliability. Results Among 1378 unique citations, 39 studies were deemed eligible. Most studies (n = 29) were technical papers. Input included compiled data, verbal data, and 2D images, while outputs were in most cases dichotomous or selected among nominal classes. The most frequently employed AI tools were support vector machine for compiled data and convolutional neural network for 2D images. Model reliability was variable, but in most cases was reported to be between 80% and 100%. Conclusions AI has vast potential in rhinology, but an inherent lack of accessible code sources does not allow for sharing results and advancing research without reconstructing models from scratch. While data pools do not necessarily represent a problem for model construction, presently available tools appear limited in allowing employment of raw clinical data, thus demanding immense interpretive work prior to the analytic process.

Inductively coupled plasma mass spectrometry is a powerful analytical technique. Because of its sensitivity, accuracy, multielement capability, high throughput, rapid analysis times and low detection limits, it is able to determine simultaneously long-lived radionuclides at trace and ultra-trace levels as well as isotope ratios. It has been increasingly applied in the framework of rare events experiments like those investigating the nature of dark matter and neutrinos, where the screening and selection of extremely radiopure materials for the experimental apparatus is crucial. Here, the inductively coupled plasma mass spectrometry (ICP-MS) measurements of the chemical purity of a Cs2HfCl6 crystal scintillator used to study α decay of naturally occurring Hf isotopes and its own raw materials are reported. Moreover, in the framework of the GERDA/LEGEND experiment, an overview of the ICP-MS results to monitor the recycling process of enriched germanium scraps is shown. Significant outcomes, such as low detection limits despite the small amount of sample to analyze and fast ICP-MS results, have been achieved in response to the challenges required by modern low background experiments.

Selective hydrogenation of vegetable oils is a significant step in the synthesis of several precursors for the preparation of bioplastics and biodiesel. In this work, a commercial Lindlar catalyst (palladium on calcium carbonate; poisoned with lead) was used as an efficient catalyst in the selective partial hydrogenation of canola and sunflower oils. Different operating conditions (pressure, temperature, and catalyst amount) were tested, and results were achieved by gas chromatography analysis of methyl esters obtained by the transesterification of the triglycerides. The optimized reaction conditions (0.4 MPa, 180 °C, 4 mgcatalyst/mLoil) were determined for the hydrogenation of linoleic acid (C18:2) and linolenic acid (C18:3) with 84.6 and 90.1% of conversion, respectively, into 88.4% relative percentage of oleic acid (C18:1) with low formation of C18:0 (stearic), below 10%, with stability of the catalyst during several cycles with maximum C18:1 relative percentage ranging between 86.6 and 80.7%.

The preparation of three novel active and stable magnetic nanocatalysts for the selective liquid-phase oxidation of several olefins, has been reported. The heterogeneous systems are based on the coordination of cis-MoO2 moiety onto three different SCMNP@Si-(L1-L3) magnetically active supports, functionalized with silylated acylpyrazolonate ligands L1, L2 and L3. Nanocatalysts thoroughly characterized by ATR-IR spectroscopy, TGA and ICP-MS analyses, showed excellent catalytic performances in the oxidation of conjugated or unconjugated olefins either in organic or in aqueous solvents. The good magnetic properties of these catalytic systems allow their easy recyclability, from the reaction mixture, and reuse over five runs without significant decrease in the activity, either in organic or water solvent, demonstrating their versatility and robustness.

The circular economy and maximization of environmental sustainability are increasingly becoming the vision and mission of companies competing in present-day global markets. In particular, in the energy sector, the transition from fossil fuels to renewable sources of energy has become the widespread mantra. One typical example is the deployment of devices which produce clean energy, such as solar photovoltaic panels and solar thermal panels, wind generators, tidal stream generators, wave power generators, etc. These are undoubtedly generating clean energy, but their manufacture creates hazardous by-products, the disposal of which results in increased environmental pollution. Chemical Vapor Deposition (CVD) is widely used in manufacturing of solar photovoltaic cells. In these processes, typically, crystalline silicon is precipitated from chlorosilanes, iodides, bromides and fluorides. Polluting by-products include deposition of a silicon film, formation of SiO2 powder and formation of toxic vapors of HF, SiH4 and PH3. Usually, these gaseous products are eliminated in a central scrubber, whose unwanted by-product consists in large quantities of hazardous fluorine-containing sludge. This article concerns an effective and inexpensive detoxification of fluorinated sludge, developed by the authors during research into the sludge collected from the scrubber of a PV cell manufacturing plant located in southern Italy.

The textile industry is a source of significant amounts of cellulosic waste that can be processed into promising sorbents. The aim of study was understanding the adsorption behavior of metal ions on cellulose surfaces obtained from cellulose textile waste of light industry. Previous studies have shown that unmodified cellulose-based ion exchange resins obtained at different pH values were able to remove metal ions from aqueous solution. In present work the cellulose-based ion exchange resins were prepared by H2SO4 hydrolysis of initial waste product with following neutralization up to different pH and drying at 80 °C. Based on the fractional composition of powdered sorbents, the weighted average particle size of the sorbents used is determined: sorbents with pH = 1.5 - 3 ≈ 0.57 mm; sorbents with pH = 5 - 7 ≈ 0.14 mm. The IR analysis of the elemental composition of the particles showed the presence of bound sulfate groups in the powder sorbent with pH = 1.5-3. The results of experiments showed that the modification of the surface of the cellulose waste with sulfuric acid increased the effect of adsorption of Ni, Fe and Pb ions from an aqueous solution. It has been established that the electrostatic interaction between surface functional groups plays a significant role in the adsorption properties of the sorbents obtained. The affinity of sulphonic acid resins for cations generally varies with the ionic size and charge of the cation. This study showed that adsorption capacities of studied metals were in the order of Fe3+

The management of waste from electrical and electronic equipment is always asking for innovative solutions. However, in order to make this business interesting for companies, more information is needed, especially economic data. To this aim, this work discusses the recycling of wasted liquid crystal displays (LCDs), both in technical and economic terms. In addition, a sensitivity analysis has been implemented to justify the soundness of the results and the effect of instability on some critical variables. Results demonstrated as spent LCDs are an interesting field in which to develop circular practices. The economic analysis defines that the recycling of wasted LCDs are profitable in the baseline scenario (134 thousand €) and this is determined mainly by both back cover and valuable printed circuit boards. Additionally, the project is not economically feasible without a disposal fee (−1.7 million €).

In modern society, use of natural resources poses a great challenge. However, the circular economy paradigm has defined a new concept of waste, proposing it as a business opportunity. Of particular interest in this paradigm is ‘waste electrical and electronic equipment’ (WEEE), given its high growth rate, and ‘wasted printed circuit boards’ (WPCBs), which are the most valuable component of WEEE. Although WPCB recycling is currently dominated by large firms, the present work evaluates the economic feasibility of hydrometallurgical processes, as used within small and medium enterprises (SMEs). Discounted cash flow (DCF) is used as a reference methodology and net present value (NPV) is used as an economic performance index. The analysis is conducted on three categories of WPCBs (low-, medium- and high-grade) and 15 categories of e-waste. The results underline the key role played by the market price of Au and Pd, plus the purchase cost of WPCBs. Accordingly, sensitivity, scenario and risk analyses are conducted on these variables and a break-even point (BEP) analysis is used to define the exact values for which economic feasibility is verified. NPV is shown to vary from 6.8 million € for medium-grade WPCBs to 63.0 million € for high-grade WPCBs in a baseline scenario, with a negative (unprofitable) result (NPV of -2.8 million €) for low-grade WPCBs.

The present paper is focused on the extraction of gold from high-grade e-waste, i.e., spent electronic connectors and plates, by leaching and electrowinning. These connectors are usually made up of an alloy covered by a layer of gold, sometimes, in some of them, a plastic part is also present. The applied leaching system consisted of an acid solution of diluted sulfuric acid (0.2 mol/L) with thiourea (20 g/L) as a reagent and ferric sulfate (21.8 g/L) as an oxidant. This system was applied on three different high-grade e-waste, namely: (1) Connectors with the partial gold-plated surface (Au concentration—1139 mg/kg), (2) different types of connectors with some of which with completely gold-plated surface (Au concentration—590 mg/kg), and (3) connectors and plates with the completely gold-plated surface (Au concentration—7900 mg/kg). Gold dissolution yields of 52, 94, and 49% were achieved from the first, second, and third samples, respectively. About 95% of Au recovery was achieved after 1.5 h of electrowinning at a current efficiency of only 4.06% and current consumption of 3.02 kWh/kg of Au from the leach solution of the third sample.

Typical methods for the treatment of waste pickling solutions include precipitation by alkaline reagents, most commonly calcium hydroxide. As a result, large volumes of galvanic sludge form, containing iron, calcium, sulphates, and a relatively small quantity of zinc (&lt, 20%), making Zn recovery not profitable. In summary, state-of-the-art Zn galvanization processes entail the loss of valuable metals and the irrational and expensive handling of spent pickling solutions (SPSs). The resulting conclusion is that there is room for a significant improvement in the way SPSs are treated, with the double goal of enhancing Zn galvanization methods&rsquo, economic viability and achieving a lesser impact on the environment&rsquo, s processes. The experimental results show that it is possible to use SPS as a coagulant to treat the process wastewaters, kept separated, and added with sodium hydroxide. The results in obtaining precipitates with Zn contents higher than 40%, increasing the added advantage of making Zn recovery profitable. The results show the possibility of using SPS as a coagulant in the process of physical-chemical wastewater treatment and sodium hydroxide to obtain a precipitate with a zinc content of more than 40%.

The resistance of steel to corrosion is obtained with a number of industrial processes based on Zn galvanization. However, all these methods bear a relatively high price tag due to the cost of Zinc plates and electrolytes as well as the formation of hazardous wastewaters containing metals and acids. Wastewaters from Zn galvanization may be grouped into two main types: Mix of Rinse Water (MRW) and Spent Pickling Solutions (SPS). Ordinarily, these waters are mixed and sent for treatment by precipitation. As a result large volumes of galvanic sludge is formed, containing iron, calcium, sulphates and a relatively small quantity of zinc (

The article reports the preliminary results obtained in a pilot plant that treats a spent tetramethylammonium hydroxide (TMAH) solution, a typical chemical compound used in the microelectronics industry and massively present in wastewaters. The plant is based on three aerobic bioreactors in series, fed by a real TMAH solution effluent from the semiconductor industry. The plant ran for 14 days in continuous operating mode with a flow rate of 5 L/h; then, the plant switched to batch mode. The microbial population was analyzed to determine if microbial population changes occurred. The results indicated that TMAH degradation only occurred during the batch operation mode. The TMAH reduction was about 80% in the first reactor and complete (100%) in the second and third bioreactors. At the same time, the microorganisms increased their mass by 338%, 58%, and 1% in the first, second, and third bioreactor, respectively. The degradation intermediates confirmed the efficiency of the process and the possible reuse of water, which closes the water loop's circularity. Furthermore, a nitrate concentration of 150–250 mg/L was found in the last two bioreactors: this implies a significant presence of ammonium-oxidizing bacteria. Community genomic analysis was conducted to detect changes in the microbial community due to changes in operating conditions that could cause reactor failure if methylotrophs were washed out or outcompeted by unspecific bacteria.

Rare earth elements (REEs), independently by the economic value, have a strategic importance and are involved, as critical materials, in the competition for their supply. An innovative process with the introduction of a preliminary physicochemical treatment was proposed. The mechanical activation of waste of fluorescent powders was performed by a vibratory disc mill at different experimental conditions to optimize the process. The mechanical forces induced to the powders cause crystal structure defects with a consequent increase of rare earths leachability. Factorial experimentations and analysis of variance were studied to determine the significant effects of the investigated factors (mechanical activation time, sulfuric acid concentration, pulp density and leaching temperature), especially for terbium dissolution. The preliminary activation allows to increase terbium dissolution of 35%. Then, according to the best conditions the subsequent operations of precipitation and calcination were performed obtaining a purity of 98.3% as rare earth oxides. Based on the experimental results, the flowsheet for rare earths recovery has been proposed and implemented by SuperPro Designer, a simulation software for process analysis and mass-energy balances. Finally, this paper reports a comparison between the present process with the mechanical pre-treatment and the alternative method based on thermal pre-treatment.

Solar energy has contributed significantly to the energy transition towards a low carbon society. Public offices – including universities – are being called to participate in the solar energy transition, as the availability of their rooftops represents an opportunity. The present study aimed at evaluating the economic feasibility of a photovoltaic (PV) plant at the University of L’Aquila, approximately 10 years after an earthquake devastated the region. The reconstruction process is ongoing, and a solar PV plant could potentially move the city in a sustainable direction. The development of sustainability models requires the economic verification of relevant projects and a complete list of indicators for decision-makers. The present work found that a 210 kW PV plant at the University of L’Aquila would reduce emissions by 184.9 t CO2eq/year and generate 1500 € profits for each kW installed; and a 115 kW PV plant would reduce emissions by 101.5 t CO2eq/year and generate profits of 1370 € for each kW installed. The analysis of alternative scenarios gave solidity to the results, confirming the pivotal role of the share of self-consumed energy. Level of insolation and plant size were also found to significantly influence economic performance. Finally, the adoption of a bonus to encourage the production and self-consumption of energy may increase investors’ attention towards environmental issues.

The separation of yttrium and calcium from acid leach liquor obtained from leaching of fluorescent lamp phosphors has been investigated by solvent extraction with D2EHPA and Cyanex 272 in kerosene. The preliminary tests suggested that D2EHPA was more efficient than Cyanex 272 for separation of yttrium. The experimental tests allowed to define the best process conditions, among those investigated, to separate and recover yttrium selectively. The best separation circuit included three-stage cross current extraction with 20%v/v D2EHPA in kerosene (O/A = 1/1, room temperature, 10 min of contact, pH 0.02) and stripping step in counter current with 1.5 M sulfuric acid (O/A = 1/1, room temperature, 30 min of contact). After stripping, yttrium was recovered as oxalate by the addition of oxalic acid. According to the experimental results, a hydrometallurgical process was developed. The final recovery from leach liquor was around 90% and the grade of the final product was 97.5% as hydrated yttrium oxalate. The main impurity was sulfur, 1.28% wt, in addition to traces of other elements such as Si (0.057% wt), Zn (0.015% wt), Eu (0.14% wt) and Fe (0.02% wt).

The paper reports on a possible way to recycle fluid catalytic cracking catalysts (FCCCs), widely used in oil refining operations. This research proposes a novel approach that leads to a near zero-waste process. The spent FCCC was leached by 1.5 mol/L of HNO3, HCl and H2SO4 solutions at 80°C, for 3 h with a solid to liquid ratio of 20 %wt/vol. The leaching yields for cerium and lanthanum were in the range 69-82 %. The solid residues from the leaching stage were used as base material for the synthesis of the zeolites by means of a combined thermal-hydrothermal treatment. The characterization of the zeolites demonstrated that the Na-A phase was predominant over the Na-X phase. The zeolites were tested as sorbent material for CO2 separation from CH4, in order to simulate the upgrading of biogas to biomethane. The maximum adsorption rate of CO2 was 0.778 mol CO2/kg of zeolite at 3 bar, with a resulting CH4 recovery of 62 % and purity of 97 %vol. The zeolites synthesized from spent FCCC represent a feasible solution to recover such industrial waste.

Benzo-15-crown-5 ether supported on multi-wall carbon nanotubes (MWCNTs) by tethered poly(amidoamine) (PAMAM) dendrimers efficiently coordinated methyltrioxorhenium in the selective oxidation of olefins to epoxides. Environmentally friendly hydrogen peroxide was used as a primary oxidant. Up to first and second generation dendrimer aggregates were prepared by applying a divergent PAMAM methodology. FT-IR, XRD and ICP-MS analyses confirmed the effective coordination of methyltrioxorhenium by the benzo-15-crown-5 ether moiety after immobilization on MWCNTs. The novel catalysts converted olefins to the corresponding epoxides in high yield without the use of Lewis base additives, or anhydrous hydrogen peroxide, the catalyst being stable for more than six oxidative runs. In the absence of the PAMAM structure, the synthesis of diols largely prevailed.

Catalysts for selective catalytic reduction are widely used for the reduction of nitrogen oxides into gaseous nitrogen in many industrial applications. These catalysts usually contain titanium, tungsten, and vanadium. Due to the increasing demand, a new strategy for the management of end-of-life catalysts is urgent, in particular for the recovery of valuable metals and the reduction of the material disposed of. Titanium, tungsten, and vanadium shall be recovered and reused for the production of new catalysts or other products, to establish a circular economy approach. In this paper, a systematic review of the main strategies adopted for the management of spent catalysts was proposed and, in particular, an overview of the regeneration and rejuvenation techniques, the current processes for the recovery of such catalysts and the treatments patented. The present study found that among the recycling processes for the extraction of metals, those based on alkaline roasting and/or leaching are the most used: vanadium and tungsten are indeed water-soluble, so that can be easily separated from titania during the leaching stage. Instead, the acid leaching is not developed because of the downstream stages required to separate the three metals from each other. The recovery of the metals is currently negligible at full scale. For this reason, the recovery of titanium, tungsten, and vanadium with high extraction yields and grades shall be pursued in the future at a large scale, and the research shall be oriented towards this scope, whereas landfilling, that is still the main option in the management of this material, shall be penalized with a disposal fee.

The study of the activity of a series of heterogeneous cis-dioxomolybdenum(VI) based catalyst precursors for the hydrogen peroxide promoted oxidation of benzothiophene, 2- and 3-methylbenzothiophene, dibenzothiophene and 4,6-dimethyldibenzothiophene, has been carried out. The last, chosen as model substrates of the common sulfurated derivatives of fuels, have been oxidized in the presence of selected imidazolium based ionic liquids, under extractive oxidative desulfurization conditions. The reactivity of sulfur-containing compounds toward the oxidation to their corresponding sulfones has been evaluated, firstly, for each type of substrate alone, and then applying the optimized procedure to a system formed by all sulfurated substrates. Our aim was to mimic the oxidation of a model diesel oil, under either thermal or microwave assisted heating. Cis-dioxomolybdenum (VI) compounds behaved as very active and stable catalytic systems retaining, in one selected case, the original activity at least for three cycles. Imidazolium ionic liquids played a dual fundamental role not only as extractant and reaction medium but also as stabilizing system for both the oxidant and the catalytic agents. Under optimized microwave-assisted conditions, the quantitative elimination of sulfurated substrates from the model diesel oil, was obtained after only 1 h or 2 h, when [BMIM]OTf or [BMIM]BF4 and [OMIM]BF4, respectively, have been used as ionic liquids.

Silica-coated iron oxide magnetic nanoparticles to be employed as the starting core for easily-recoverable heterogeneous catalysts supports, were synthesized. We tuned both the properties of the magnetic core and of the covering shell, with particular emphasis on the optimization of the silica layer thickness. Afterwards, structural-sensitive techniques (XRD, BET surface area analysis), surface-sensitive techniques (ATR-IR, XPS), imaging (SEM, TEM), elemental analyses (ICP-MS) and magnetization analyses (AGFM), were employed to unravel the features of the synthesized materials. The oxidation of cis-cyclooctene with tert-butyl hydroperoxide in presence of MNPs was used as probe reaction to check the reactivity of the NPs and the effectiveness of the silica shield. The results of these tests showed its chemical inertia confirming the absence of any detrimental iron oxide catalyzed side-reactions or magnetic core modification.

Seventy-six samples of saffron were analysed through inductively coupled plasma-mass spectrometry (ICP-MS) and stable isotope ratio analysis. The dataset was formed by 67 samples harvested in different areas of Italy, Morocco and Iran, and nine samples purchased in the Italian market. For the first time, 42 elements and five stable isotopes (δ13 C, δ15 N, δ34 S, δ2 H and δ18 O) were considered to carry out the discrimination of the samples on the basis of their geographical origin. Combined ICP-MS and isotopic composition data turned out to be a useful tool for the geographical discrimination of saffron among predefined cultivation sites. K, Cr, Mn, Ni, Zn, Rb, Sr, Mo, Cs, Nd, Eu, Pb, δ13 C, δ15 N, δ34 S and δ2 H were identified as the significant variables in geographical discrimination. Moreover, the class models generated for saffron cultivated in two specific areas of Central Italy exhibited 100% specificity for Moroccan, Iranian and commercial samples and a high specificity (83% and 84%) for the saffron samples cultivated in other, although close, Italian sites.

The present paper deals with an innovative scrubber (air pollution abatement) used to remove particulate matter and other pollutants from air. Air pollution abatement scrubbers were placed in different urban areas and in industrial production sites. In particular, the results obtained in one fiberglass production facility showed a reduction in particulate matter of 46.3–99.9% in the size range 0.50–0.00 µm throughout the experimentation period. The aqueous solutions coming from the scrubbers, placed in different sites, were collected, analyzed and treated in order to regenerate the water and make it available for the periodic refilling of the scrubber’s tanks. Coagulation, precipitation, carbon adsorption and Fenton processes were applied in order to design a suitable integrated process able to treat all the samples coming from the scrubbers. The reduction in total suspended solids, total dissolved solids, phenols and chemical oxygen demand was higher than 85% by the Fenton process, demonstrating that water is completely recoverable and reusable. Alternatively, the treated water can be discharged into a surface water body. Based on the results from the experimental campaign, a mobile plant was designed in order to treat such wastewater. Depending on the physicochemical parameters of the wastewater, specific treatments can be chosen and carried out by such mobile plant.

The transport sector has a low penetration of renewable energy, and this presents a serious obstacle to tackling climate change. Biomethane is seen as a decarbonisation solution, but only some European countries have pursued its development. Italy is one of these countries, having released a decree to stimulate development of the sector. The present work considers two typologies of substrate (the organic fraction of municipal solid waste and by-products) used in three sizes of plants (125 m3/h, 250 m3/h and 500 m3/h). A detailed socio-economic analysis is presented and policy implications are provided. The recovery of waste enables the creation of a circular economy, but the economic feasibility of such a model is verified in only some scenarios. A sensitivity analysis on the critical variables is conducted to support investment in this area. The use of green gas is found to be capable of significantly reducing greenhouse gas emissions in the transport sector, but the economic value of any environmental externality is low due to the value of carbon dioxide.

Waste of Electrical and Electronic Equipment (WEEE) is the fastest growing waste stream in Europe. This waste contains a high amount of critical and valuable metals as the rare earths defined critical materials from European Commission (2010) and the precious metals. Exhaust fluorescent lamps are examples of electronic wastes that have important percentages of rare earths elements (REEs). These types of WEEE represent an important secondary source of REEs. Moreover, they are classified as hazardous materials for the presence of mercury and need to be properly handled. Among the most valuable component of WEE there are printed circuit boards (PCBs) for their precious metals content. In the present paper a hydrometallurgical process for the recovery of REEs (yttrium, europium, terbium, gadolinium, lanthanum and cerium) from fluorescent powders and copper, tin, zinc, gold and silver from WPCBs. Hydrometallurgical process for rare earths recovery includes a preliminary roasting, acid dissolution and precipitation of a mixture of REEs oxalates. Alternately, a solvent extraction operation and stripping can be added after dissolution to selective recover rare earths. For the WPCBs treatment, a hydrometallurgical process consisting of two sequential leaching procedures (performed in counter and cross current ways) followed by selective precipitation/reduction of elements of interest from solution has been designed.

The present paper describes the experimental tests for the recycling of fluid catalytic cracking catalysts (FCCCs). The process aims at the recovery of cerium (Ce) and lanthanum (La) as well as the reuse of the leaching solid residue that represents the actual problem in terms of global amount landfilled every year. Landfilling is still the main choice for the handling of such catalysts. This novel process proposes an alternative recycling approach that leads to the production of synthetic zeolites, that have several industrial applications. FCCC was leached by 1.5 mol/L of HNO3, HCl and H2SO4 solutions at 80 °C, for 2 h with a solid to liquid ratio of 20 %wt, and the two rare earth elements were recovered by precipitation with an overall yield in the range 70–80%. The solid residues from the leaching stage were used as the base material for the synthesis of the zeolites by means of a combined thermal-hydrothermal treatment. The characterization of the zeolites demonstrated that the Na-A phase was predominant over the Na-X phase. The zeolites were tested as sorbent material for CO2 separation from CH4, in order to simulate the upgrading of biogas to biomethane. The maximum adsorption rate of CO2 was 0.778 mol CO2/kg of zeolite at 3 bar, with a resulting CH4 recovery of 62% and 97 %vol as purity. Since the results in adsorption of CO2 were not satisfying, the same zeolites were used to remove heavy metals from a synthetic wastewater solution containing three metals. Equilibrium and kinetic models were also developed in order to describe the adsorption process. The maximum adsorption load was calculated by the Langmuir isotherm and resulted to be 24–32 mg/g for Ni, 52–60 mg/g for Zn and 122–181 mg/g for Cu. The results also showed that the kinetics of the adsorption process is almost fast, as after 1 h at least 95% of zinc and copper were removed, whereas the kinetics of nickel was slower for all the three zeolites. As a conclusion, the zeolites are more efficient in metal adsorption than CO2 capture, but other applications will be tested in the future.

The paper is focused on the study of hydrometallurgical processes for recovery of rare earths (RE) from fluid catalytic cracking catalysts (FCCC). According to the experimental results two processes were proposed: in the first one RE were recovered as double sulfates by selective precipitation with sodium hydroxide after leaching with sulfuric acid. The second approach consisted of dissolution of powder by acids, solvent extraction by (2-ethylhexyl)phosphoric acid (D2EHPA), stripping and precipitation of RE oxalates using oxalic acid. Experiments showed that solvent extraction was found to be beneficial in terms of achieving improved final products quality with greater purity (∼98%).

The present paper deals with the optimization of an industrial plant that treats waste solutions coming from different manufacturing processes. In particular, an extensive experimental work was carried out to understand whether some streams could be diverted from the distillation column in order to recover solvents, suitable as secondary fuel. Experimental tests, including four full factorial designs, optimized the consumption of reagents in the Fenton process: the specific consumptions were 0.65 g L−1 of H2O2 and 0.42 g L−1 of FeSO4·7H2O, when treating the evaporated fractions from multiple-effect evaporator, concentrator and dryer, diverted from the distillation column. The application of the Fenton process increased the abatement of the chemical oxygen demand (COD) and the oxygen uptake rate (OUR). The optimization of the feed entering the distillation column led to a water content lower than 5%vol in the distilled fraction: hence, such solvents could be used as additional fuel in a dual-fuel boiler. The economic analysis showed that it could be possible to save around 420,000 € y−1.

This article describes the improvement of wastewater treatment in a fertilizer plant located in Central Italy (municipality of Vasto). In this facility, water is used for the removal of dust and fluorinated gases from the air. The resulting wastewater contains fluorides and phosphates in hazardous forms. Its treatment ordinarily does not result in a Zero-Liquid Discharge (ZLD) process. To achieve this purpose, several reagents were tested, focusing on the correlation linking pH, type of reagent and the effect on the separation of fluorides and phosphates from the wastewater. It was eventually found, and explained with a model, that hydrated lime at pH = 12 was so effective as a precipitating agent that phosphate and fluoride separation reached a value of 99.9%, thus allowing for reuse of the water in the plant process. Furthermore, phosphates and fluorides precipitated in a non-hazardous form, so that the material could also be recycled. In synthesis, wastewater treatment of the fertilizer plant was upgraded so that it became a ZLD process coupled with the recovery and recycling of fluorides and phosphates.

In this research, extraction and purification of molybdenum from a leach solution of molybdenite dissolution was performed. Cationic polyelectrolytes were used for the first time in this study for selective recovery of molybdenum. For this purpose, some water-soluble coagulants of KlarAid PC products were employed and the experimental results in terms of recovery percentages, optimum value of needed polyelectrolyte and their performance were investigated. In order to evaluate the extraction and purification process, the precipitated molybdenum compounds were studied by ICP-OES, XRD, FTIR, and SEM. The results showed that about 88% of molybdenum could be recovered in one step with a final estimated purity of 100%. Afterward, a relatively pure MoO3 product with a layered-structure was successfully synthesized by a simple heat treatment. Finally, the results showed that the proposed novel method, polyelectrolyte extraction (PX), could be an efficient alternative to other processes (i.e. ion exchange resins and solvent extraction) for selective recovery of metals from acid solution.

Tetramethylammonium hydroxide (TMAH) is widely used as a solvent in the semiconductor industry. After the photo-impression process, it is necessary to remove the photoresist (PR) layer from the surface of the circuits, for this purpose, a TMAH solution is usually used. This chemical compound is highly toxic and corrosive and cannot be discharged into the environment. This study was carried out in collaboration with LFoundry (SMIC group), in order to prove the feasibility of biodegradation under aerobic conditions, using microorganisms coming from the LFoundry&rsquo, s wastewater treatment plant (WWTP) at different operating conditions. The feed composition was modified in order to add a small but increasing amount of TMAH and PR. The aim was to verify if the increase of TMAH concentration was harmful to bacteria. The feed stream, containing TMAH and PR, was the only carbon source for the metabolism of the aerobic microorganisms. The results of this study demonstrated an effective biological degradation of TMAH and showed a total removal efficiency of more than 99.3%, with a final concentration of 7 mg/L. Moreover, the kinetic parameters of the Monod model were also calculated. The results obtained from the experimental campaign were used to design a pilot plant that will treat around 25 L/h of waste TMAH/PR solution.

The present lab-scale experimental study presents the process of leaching waste printed circuit boards (WPCBs) in order to recover gold by thioureation. Preliminary tests have shown that copper adversely affects gold extraction; therefore an oxidative leaching pre-treatment was performed in order to remove base metals. The effects of sulfuric acid concentration, hydrogen peroxide volume and temperature on the metal extraction yield were studied by analysis of variance (ANOVA). The highest copper extraction yields were 76.12% for sample A and 18.29% for sample D, after leaching with 2M H2SO4, 20 ml of 30% H2O2 at 30°C for 3h. In order to improve Cu removal, a second leaching was performed only on sample A, resulting in a Cu extraction yield of 90%. Other experiments have shown the negative effect of the stirring rate on copper dissolution. The conditions used for the process of gold extraction by thiourea were: 20 g/L thiourea, 6g/L ferric ion, 10 g/L sulfuric acid, 600 rpm stirring rate. To study the influence of temperature and particle size, this process was tested on pins manually removed from computer central processing units (CPUs) and on waste CPU for 3½ h. A gold extraction yield of 69% was obtained after 75% of Cu was removed by a double oxidative leaching treatment of WPCBs with particle sizes smaller than 2 mm.

The present paper deals with experimentation of ZrO2 and Al2O3-supported catalysts for conversion of naphthalene, chosen as tar model compound of pyrolysis or gasification syngas. In particular, the reforming capacity of active metals and promoters such as Co, Ni, Fe, Cr, Ce and Pt was tested in a fixed bed reactor at temperature from 400 to 900 °C. As regards ZrO2-supported catalysts, the best results were achieved by the Ni/Fe/Pt catalyst with 96% naphthalene conversion, 78% and 280% as CO and H2 production yield at 800 °C. Regarding Al2O3-supported catalysts, they were more active on average than the zirconia ones, achieving a very good performance even at 500 °C (90–100% naphthalene conversion, 30–40% CO yield and 300–350% H2 yield at 550 °C). Influence of different amounts of alumina, montmorillonite and carbon on carrier composition as well as pellets’ size were also studied. Both zirconia and alumina catalysts showed deactivation at higher temperatures due to coke deposition, resulting in a strong H2 production drop. Regeneration of catalysts by O2 and steam as well as activation by H2 were also studied. The activated catalyst was able to convert more than 99% naphthalene at 450 °C with a CO and H2 production yield of 26% and 420%, respectively.