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 PrPO4(s) and Cheralite (CePO4(s)) where Ce is substituted by La and Ca and Xenotime (YPO4(s)) were found as main minerals AlPO4(s) Ca,MgYPO4(s) were also identified.
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•Rare earth recovery from acid mine drainage•Effective process to treat acid mine drainage to concentrate and recover rare earth elements•Integration of selective phosphate precipitation with ion-exchange concentration•Selective separation of rare earth elements from transition elements
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 (60NaCl/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 20bar, provided a rich Mg(II) (8.3gMg(II)/L) and Ca(II) (2.1gCa(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±2gNaCl/L was treated to remove residual Mg(II) (760mg/L) and Ca(II) (415mg/L) by chemical precipitation with Na2CO3 and NaOH before the EDBM unit. Divalent cations free brine containing NaCl (50gNaCl/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 1M NaOH/HCl) at 9V. No substantial effect of initial acid and base concentrations on the overall performance was observed. An energy consumption of 2.6kWh/kg NaOH and current efficiency of 77±3% were calculated.
•NF was used to concentrate and separate Ca–Mg from RO brine for phosphate recovery.•NF permeate stream precipitation treatment was done to remove residual Ca and Mg.•EDBM was applied to produce HCl and NaOH as chemicals for desalination treatments.•Rich Mg and Ca concentrate stream and rich NaCl permeate stream were obtained by NF.•NaOH and HCl up to 1M were obtained at 9V by EDBM using RO divalent free brines.
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 H2SO4 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 Na2SO4 and ii) a solution mimicking AMD from dams, containing Na2SO4 and Fe2+, Zn2+ and Cu2+. 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%).
•Storage of acid mine drainage in dams and open-pits need a treatment.•Acid mine drainage as a potential source for water and chemical valorization•Nanofiltration membranes were used for metal and acid recovery.•Membrane permeances to ion were determined by applying SEDF model.
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 NH4NO3 and NH4H2PO4). 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 NH4NO3. Overall, it was possible to integrate two innovative membrane technologies for the valorisation and concentration of nutrients from ammonia wastewater streams.
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•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.
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.
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•A nitrogen flow analysis was carried out for Spain with the year 2016 as reference.•The largest proportion of losses was associated with air emissions from agriculture and industry.•Results highlight the dependence on products with high N content from third markets.•The efficiency of N use and the impact of current diet on N cycling have been evaluated.•A circular strategy involves recovering the nutrients present in WW and transforming them into fertilisers.
•Hap was obtained by chemical precipitation using concentrated P(V) alkaline brines.•Three stages were identified in the precipitation of phosphate as Hap.•Higher precipitation rate of P(V) was ...obtained at constant pH of 11.5.•Hap with higher degree of crystallinity was formed at higher P(V)0 concentration.•At higher Ca(II) dosing rate, mean size and degree of crystallinity were higher.
In this work, phosphorous recovery as hydroxyapatite (Ca5(PO4)3OH(s)=Hap) from alkaline phosphate concentrates (0.25–1gP–PO43−/L) using calcium chloride (6g/L) in a batch reactor was evaluated. Ca(II) solutions was continuously fed (0.1–0.3mL/min) up to reaching a Ca/P ratio of ∼1.67 (5/3) to promote Hap formation. Hap powders were characterized by structural form (using X-ray diffraction (XRD), laser light scattering (LS) and Fourier transform infrared spectroscopy (FTIR)); textural form (using Field Emission Scanning Electron Microscopy with Energy Dispersive System (FE-SEM/EDS) and Brunauer–Emmett–Teller (BET)) and thermally (using Thermogravimetric Analysis (TGA)/Differential Thermal Analysis (DTA)). When pH was kept constant in alkaline values (from 8 to 11.5), Hap precipitation efficiency was improved. At pH 11.5, higher phosphorous precipitation rate was registered compared to that obtained for pH 8 and 10, but lower degree of crystallinity was observed in the Hap powders. The increase of the total initial phosphate concentration lead to the formation of Hap powders with higher degree of crystallinity and crystal diameter, but also lower mean particle size. As Ca(II) dosing rate increased Hap precipitation rate was higher, and also the mean size and degree of crystallinity of the prepared particles increased.
The integration of up-concentration processes to increase the efficiency of primary sedimentation, as a solution to achieve energy neutral wastewater treatment plants, requires further post-treatment ...due to the missing ammonium removal stage. This study evaluated the use of zeolites as a post-treatment step, an alternative to the biological removal process. A natural granular clinoptilolite zeolite was evaluated as a sorbent media to remove low levels (up to 100mg-N/L) of ammonium from treated wastewater using batch and fixed bed columns. After being activated to the Na-form (Z-Na), the granular zeolite shown an ammonium exchange capacity of 29±0.8mgN-NH4+/g in single ammonium solutions and 23±0.8mgN-NH4+/g in treated wastewater simulating up-concentration effluent at pH=8. The equilibrium removal data were well described by the Langmuir isotherm. The ammonium adsorption into zeolites is a very fast process when compared with polymeric materials (zeolite particle diffusion coefficient around 3×10−12m2/s). Column experiments with solutions containing 100mgN-NH4+/L provide effective sorption and elution rates with concentration factors between 20 and 30 in consecutive operation cycles. The loaded zeolite was regenerated using 2g NaOH/L solution and the rich ammonium/ammonia concentrates 2–3g/L in NaOH were used in a liquid-liquid membrane contactor system in a closed-loop configuration with nitric and phosphoric acid as stripping solutions. The ammonia recovery ratio exceeded 98%. Ammonia nitrate and di-ammonium phosphate concentrated solutions reached up to 2–5% wt. of N.
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•A natural zeolite was evaluated to recover ammonium in column experiments.•Loaded zeolite was regenerated and rich concentrates were used in a LLMC system.•Hollow fibre liquid-liquid membrane contactors were used to produce liquid fertilizers.•The closed-loop configuration allowed recovery ratios of ammonia higher that 98%.•Concentrated solutions reached up to 2–5% wt. of N.
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•SED is an efficient separation technology for metallurgical process waters.•Recovery of Cu(II) and Zn(II) from metallurgical steams containing As(V).•Monovalent/divalent ion ...separation using AEM-MCV-CEM configuration.•Product streams contained 80, 87 and 95% of the initial Cu(II), Zn(II) and As(V).•A Cu/Zn-rich stream with a purity of both cations of 99.8% was obtained.
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 (H2AsO4−), while Cu(II) and Zn(II) are mainly present as cationic species although partially complexed as neutral complexes (CuSO4 and ZnSO4). 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 CuSO4+ZnSO4. 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.
•A biogas deep treatment was installed and operated at pilot-scale in a WWTP in Spain.•The H2S adsorption mechanism on the iron adsorbent was oriented to oxidation to S(s).•Siloxane D4 was ...responsible of the adsorption breakthrough on the activated carbon.•The integration of biogas treatment and fuel cell systems is technically possible.•Cascade configuration reduces operation cost compared to stand alone sorption systems.
Biogas from anaerobic digestion is a powerful renewable fuel that can be used as a feedstock for fuel cell systems. A biogas deep treatment was installed and operated at pilot plant level in a Waste Water Treatment Plant (WWTP) in Spain in order to demonstrate the integration opportunities with Solid Oxide Fuel Cell (SOFC) technologies. The three-stage polishing system based on adsorption consisted of: (i) a regenerable iron-based adsorbent unit to remove H2S, (ii) a biogas drying unit to remove moisture and (iii) an activated carbon unit to remove the remaining trace components (siloxanes, linear and aromatic hydrocarbons). The biogas entering the polishing system was previously treated in a biotrickling filter for primary H2S abatement. Removal efficiencies on the iron-based adsorbent were over 99% and adsorption capacity was calculated to be of 21%wt. An adsorption mechanism for H2S chemisorption oriented to oxidation to elemental sulphur rather than to crystalline FeS(s) was proposed and could explain the low efficiency of the regeneration process. The remaining contaminant traces were efficiently removed in the drying and activated carbon unit and concentration levels below 0.1mg/Nm3 were obtained. A roll-up phenomenon with siloxane D4, which was responsible of adsorption breakthrough on the activated carbon filters, was postulated; and leaded to an overall adsorption capacity of 2%wt. The economic assessment concluded that the cascade configuration of an upstream H2S abatement followed by downstream adsorption technologies, compared to stand-alone adsorption systems, divides the overall treatment cost by three; increasing the profitability of biogas-powered fuel cell projects.
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).
•Selective precipitation and ion-exchange process integration for Zn and Cu recovery.•Fe (>99%) and Al (>90%) were removed as hydroxylsulphates in the precipitation step.•Zn separation by Lewatit VP 1026 resin (>96% extraction, CF = 10) at pH > 2.5•Lewatit TP 207 resin was used for Cu separation (>99% extraction, CF = 40) at pH > 3.•On-site/off-site managements were proposed for non-ferrous metallurgical plants.
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