Salt Recovery Research Articles

A value-sensitive approach for integrated seawater desalination and brine treatment

The transition to seawater desalination integrated with resource recovery, particularly in water- and energy-scarce regions, requires innovative approaches that consider societal benefits and costs. This study goes beyond traditional techno-economic evaluations by employing a Value-Sensitive Design (VSD) approach, which guides the selection of performance indicators and informs the design of technical scenarios for integrated seawater desalination and brine treatment systems. VSD ensures that the scenarios are socially relevant by directly incorporating stakeholder values into the design and assessment process. Four technical scenarios (Sc) were used to evaluate the VSD approach: Sc1) maximum water recovery, Sc2) and Sc3) integrated desalination with brine treatment for maximum resource recovery (using different configurations) and Sc4) electricity-based desalination for chemical recovery. Techno-economic models are implemented using Python to analyse the feasibility and performance of these scenarios. The modelling results indicate that all scenarios achieve zero brine production. However, the trade-offs between resource recovery and greenhouse gas emissions are evident. Increased salt recovery leads to higher CO2 emissions (locally) due to electricity consumption. Scenario 1 minimized electrical energy consumption and emissions while maximizing water production. Scenarios 2 and 3 performed best in water and high-quality salt production. Despite its higher CO2 emissions, Scenario 4 proved most profitable due to the production of chemicals. These findings highlight the importance of tailoring plant designs to regional needs. By providing a comprehensive understanding of trade-offs, the VSD approach fosters stakeholder dialogue and serves as a valuable decision-making tool for designing sustainable desalination systems.

Simultaneous recovery of ammonium sulfate and ice from aqueous solution using eutectic freeze crystallization process

This study investigated the feasibility of eutectic freeze crystallization (EFC) process for ammonium sulfate (AS) salt recovery from 41 wt% AS solution. The EFC experiments were conducted using a 1 L double-jacketed crystallizer coupled with a recirculating chiller under varying freezing time, seed mass and seed size. The EFC process demonstrated successful AS salt recovery and water purification with the highest ice purity attained at 96.28 %. The construction of a binary AS-water phase diagram allowed the determination of the eutectic temperature, which was found to be −19.06 °C at 40 wt% of AS solution. The results indicated that the increase in freezing time enhanced the AS nucleation rate, growth rate, yield and mean product crystal size. The introduction of seeding not only provided well-controlled crystal nucleation and growth during EFC process, but also promoted the formation of larger, well-structured crystals and reduced agglomeration. Overall, the EFC process is a viable and promising option for recovering AS from wastewater, which offers high potential towards achieving zero liquid discharge goal, i.e. a sustainable and efficient approach in managing industrial effluent rich in ammonium and sulfate contaminants.

Formulation and Recycling of a Novel Electrolyte Based on Bio-Derived γ-Valerolactone and Lithium Bis(trifluoromethanesulfonyl)imide for Lithium-Ion Batteries.

This work introduces a novel electrolyte comprising lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt dissolved in bio-based γ-valerolactone (GVL) for lithium-ion batteries (LIBs). Moreover, a simple and sustainable aqueous-based recycling approach for recovering the imide-based lithium salt is proposed. Beyond the sustainable origin of the GVL solvent, this electrolyte exhibits reduced flammability risk, characterized by a flash point of 136°C, along with favorable transport properties (conductivity of 6.2mScm-1 at 20°C) and good electrochemical stability (5.0V vs Li+/Li). Its good compatibility with graphite and lithium iron phosphate electrodes ensures remarkable cycling stability in LIB full-cells after 200 galvanostatic cycles at 1C. Furthermore, the proposed liquid-liquid phase electrolyte recycling method allows for a nearly complete recovery of the LiTFSI salt (97-99%) and the GVL solvent (78%). The feasibility of the recycling process is validated by the reutilization of the recovered LiTFSI salt in electric double-layer capacitors, achieving performances similar to that of the pristine salt with exceptional long-term stability.

Optimization of Progressive Freeze Crystallization Process by Response Surface Methodology for the Treatment of Electroplating Wastewater for Copper (II) Sulphate Recovery

<p style="line-height:200%;text-align:justify;text-indent:0cm;text-justify:inter-ideograph;"><span style="line-height:200%;" lang="EN-US">For the copper-containing electroplating wastewater generated by a semiconductor company, the recovery of copper salts by progressive freeze crystallization and its process parameters were experimentally optimized and studied. Based on the results of single-factor experiments, according to the principles of Box-Behnken Design experimental design for response surface methodology to investigate the effects of coolant temperature, agitation rate, and freezing time on salt removal and optimize process parameters. The optimization results of the response surface method showed that the optimal conditions were when the coolant temperature was -8°C, the stirring rate was 264 r</span><span style="font-family:Symbol;line-height:200%;" lang="EN-US">×</span><span style="line-height:200%;" lang="EN-US">min<sup>-1</sup>, and the freezing time was 78 min. Three validation experiments were conducted under optimum conditions, and salt removal was obtained as 60.13 ± 4.10%, which is more in line with the predicted values. Treatment of copper-containing electroplating wastewater using tertiary freezing under response surface optimized experimental conditions. At this time, the total ice rate of the wastewater was about 65.00%, and the conductivity was also concentrated from 2.17 mS</span><span style="font-family:Symbol;line-height:200%;" lang="EN-US">×</span><span style="line-height:200%;" lang="EN-US">cm<sup>-1</sup> of the raw water to 2.99 mS</span><span style="font-family:Symbol;line-height:200%;" lang="EN-US">×</span><span style="line-height:200%;" lang="EN-US">cm<sup>-1</sup> with a total concentration ratio of 1.38. In addition, a higher concentration of concentrated liquid was obtained in the third freezing, while a crystalline salt precipitated from the bottom of the reactor. The precipitate was analyzed mainly as copper sulfate pentahydrate using XRD, XRF, EDS, and other characterization techniques.</span><span lang="EN-US"> Theoretical calculations show that pre-cooling of raw wastewater reduces energy consumption by up to 20.40%.</span></p>

Hydrodynamic solar-driven interfacial evaporation - Gone with the flow

Evaporation has been one of the most classic desalination processes on the Earth. When we try to use the power of water flow itself, the evaporation process can perform even better. Here, we report a hydrodynamic solar-driven interfacial evaporation process which water evaporation rate can achieve 6.58 kg·m-2·h-1 (over 100 times higher than natural evaporation). A waterwheel-structure solar interfacial evaporator was designed and assembled by printed filter papers. The evaporator can both rapidly distribute solution on the evaporation interface and be hydraulically driven to rotate continuously to improve the evaporation rate by water flow. The hydrodynamic solar-driven interfacial evaporation process successfully overcomes the problem of slow diffusion of water vapor, but also realizes the day-and-night operation of process and the self-cleaning of salt fouling. Apart from the application in solar desalination, the developed evaporator has great potentials in vapor production and salt recovery for industrial use.

Sustainable recovery and reutilization of molten salt from magnesium salt slag via supergravity separation

Magnesium salt slag is generated during the refining of crude magnesium and usually contains a large amount of soluble chloride salts, which will cause serious environmental problems. In this study, a new method was proposed for sustainable recovery and reutilization of molten salt from magnesium salt slag via supergravity separation. The phase transformation of molten salt with temperature was studied. The molten salt was in a fully molten state at 800–750 °C, while the NaCl precipitated at 750–700 °C, meantime combined with MgCl2 and tightly encapsulated the fine MgO particles. Therefore, recovery of molten salt was conducted at 800 °C enhanced by supergravity separation, where the molten salt and MgO-rich particles were efficiently recovered within 5 min with high recovery rates of 98.9 % and 99.5 %, respectively. Moreover, the recovered molten salt removed 98.6 % of oxide inclusions in the crude magnesium refining process. Meanwhile, the fine MgO-rich particles with w(MgO)=76.3 % and 1–10 µm was recovered from the magnesium salt slag, where the leaching amount of Cl- was decreased to 0.586 g/L, which was below the Chinese standard for chlorine ion content in solid wastes. Therefore, this manuscript provided a novel process for recovering molten salt from magnesium salt slag without additives and secondary pollution, meanwhile reducing the generation of solid waste and hazards.

Process integration and techno-economic assessment of crystallization techniques for Na2SO4 and NaCl recovery from saline effluents

Saline effluents containing primarily sodium chloride (NaCl) and sodium sulfate (Na2SO4) are generated from common salt production, tannery CETPs, textiles industries, desalination rejects, etc. In this work, experimental studies have been conducted for parametric evaluation of crystallization techniques for selective isolation of Na2SO4 and NaCl from saline effluent. Three crystallization approaches, i.e., evaporation-crystallization, cooling-crystallization, and antisolvent-crystallization, are assessed through parametric studies. A representative saline solution generated from a salt refinery unit is considered for the study. Lab-scale experiments were performed to determine the optimum process conditions for each crystallization process, and their performance was evaluated by estimating the separation efficiency. Chemical, P-XRD, and TGA analyses were performed to characterize the product composition, purity, and hydration state. For selective Na2SO4 recovery, cooling crystallization, and antisolvent crystallization were found suitable over evaporation crystallization. Subsequently, integrated process variants for cooling crystallization and antisolvent crystallization-based separation were developed. A techno-economic assessment (TEA) was performed to compare integrated process variants for the recovery of salts (Na2SO4 and NaCl) and establish the prospective towards commercialization. The parametric evaluation and TEA shows that the combined crystallization technologies can be potential approach to recover added-value products from saline effluents promoting waste to wealth notion.

Design of SWRO Desalination Plant for Nuclear Research Center

Libya has an infinite water resource available inthe coastal towns and cities being located on Mediterranean Sea with 1950km coast. Therefore, the need for desalinatedwater for Nuclear Research Center NRC located in Tajurais currently about 1200 m3/day. To cover the center presentand future water needs for research and developmentactivities, two thermal sea water desalination plants have been assembled in the site. One of the plants uses MultiStage Flash technology and the other one uses Multi EffectDesalination technology with capacity of 1200m/day eachone. Detailed design for 1200m3/day seawater reverseosmosis SWRO unit is carried out using ROSA S oftware to make the technical comparison with other MSF and MEDunits. The unit labeled an S W30XLE-440i by the results ofthe Software is selected since it required the lower feedpressure of 55.5bar and highest salt recovery of 45% with total dissolved solid of 190ppm. From the technical point ofview, the study showed that SWRO required lower seawater inlet flow rate than MSF and MED. The unitsefficiency are 43%, 10.5% and 25% for SWRO, MSF, andMED, respectively. Further the Product quality TDS 190ppm for RO unit is suitable for drinking water, whilethose of MSF and MED 50ppm. Energy consumption asheating steam is not required for the S WRO unit; however,a steam flow rate 7.3m 3/hr is required by MSF and MEDunits. These make SWRO unit friendlier to the environment and most proper technically under these situations.

Enhanced separation of monovalent and divalent ions in high salinity wastewater by selective electrodialysis: Experimental investigation and performance prediction

To fulfill the industrial requirements of salt fractionation and recovery from saline wastewater, a two-chamber selective electrodialysis (SED) stack incorporating commercial monovalent selective anion exchange membranes was employed and investigated in this study. Three different initial concentration ratios of NaCl/Na2SO4, namely 1:1 (10 g/L:10 g/L), 3:1 (30 g/L:10 g/L), and 5:1 (50 g/L:10 g/L) were examined to simulate various scenarios of saline wastewater. The influence of applied current density on membrane selectivity and overall system efficiency was further evaluated. The results indicated that an increase in the NaCl fraction within the feed solution directly correlates with enhanced concentration and purity of Na2SO4 in the product, achieving purities exceeding 92 %. A lower current density contributed to improved concentration and purity of Na2SO4, whereas higher current densities were conducive to augmenting the concentration and purity of NaCl. Additionally, a linear correlation was observed between the volumetric water transport and NaCl migration. Through numerical simulations, the concentrations of Na2SO4 and NaCl in the effluent were predicted, facilitating a comparative analysis with the salt fractionation efficiency of commercial nanofiltration membranes. Subsequent assessments of energy consumption and current efficiency revealed that the SED system ensured high product concentration and purity at reasonably low energy consumption (0.22–0.28 kWh per kg NaCl) alongside a high current efficiency (83–89 %). These findings offer critical insights into the optimization of salt fractionation process and highlight its economic and technical feasibility for the sustainable management of industrial saline wastewater.

Microwave heating system for CuFe2O4/rGO/PMS enhanced catalytic-oxidative pre-treatment, water, and salt recovery from reverse osmosis reject of textile industry effluent

Microwave (MW) heating mechanism was investigated for reverse osmosis (RO) reject management of real textile effluent, i.e., pre-treatment, water, and salt recovery. For pre-treatment, microwave-induced catalytic degradation (MICD) enhanced with CuFe2O4/rGO for PMS activation was applied for organics degradation. The synthesized CuFe2O4/rGO (average particle size ∼16.44 nm) was characterized for XRD, SEM with EDAX, FTIR, VSM and TGA. MICD (1 g/L catalyst (80 %:20 %), 400 mg/L PMS, 90℃ MW temperature, 450 W MW power, and pH 11.32) showed 100 % color, 80.4 % TOC, and 91.1 % COD reduction within 16 min of MW irradiation. Radical quenching studies and EPR analysis revealed that SO4•− and ⦁OH were the dominant reactive species followed by non-radical O21. Recyclability study of CuFe2O4/rGO showed 72 % color, 65 % TOC, and 71.4 % COD removal after 5 cycles. XRD and FTIR of reused CuFe2O4/rGO hold similar crystallinity and structural properties as fresh catalyst. ATR-FTIR spectrum of before and after degradation of RO reject showed considerable degradation of organic dye molecules. Subsequently, the MW heating system was optimized for water recovery (110℃ MW temperature, 700 W MW power, and 100 mL reject volume), showing 100 % water recovery within 6 min, and its characterization showed a high distillate purity. NaCl and Na2SO4 salts were recovered under different MW operating temperatures, exploiting solubility equilibrium, and characterized for XRD, SEM with EDAX, and PSA.

A comprehensive assessment of the economic and technical viability of a zero liquid discharge (ZLD) hybrid desalination system for water and salt recovery

Brine, a by-product of desalination and industrial facilities, is becoming more and more of an environmental issue. This comprehensive techno-economic assessment (TEA), focusing on the technical and economic aspects, investigates the performance and viability of a novel hybrid desalination brine treatment system known as zero liquid discharge (ZLD). Notably, this research represents the first instance of evaluating the feasibility and effectiveness of integrating three distinct desalination processes, namely brine concentrator (BC), high-pressure reverse osmosis (HPRO), and membrane-promoted crystallization (MPC), within a ZLD framework. The findings of this study demonstrate an exceptional water recovery rate of 97.04%, while the energy requirements stand at a reasonable level of 17.53 kWh/m3. Financially, the ZLD system proves to be at least 3.28 times more cost-effective than conventional evaporation ponds and offers comparable cost efficiency to alternatives such as land application and deep-well injection. Moreover, the ZLD system exhibits profitability potential by marketing both drinking water and solid salt or solely desalinated water. The daily profit from the sale of generated water varies from US$194.08 to US$281.41, with Greece and Cyprus attaining the lowest and highest profit, respectively. When considering the sale of both salt and water, the profit rises by 8% across all locations.

Unraveling wheat’s response to salt stress during early growth stages through transcriptomic analysis and co-expression network profiling

BackgroundSoil salinization is one of the vital factors threatening the world’s food security. To reveal the biological mechanism of response to salt stress in wheat, this study was conducted to resolve the transcription level difference to salt stress between CM6005 (salt-tolerant) and KN9204 (salt-sensitive) at the germination and seedling stage.ResultsTo investigate the molecular mechanism underlying salt tolerance in wheat, we conducted comprehensive transcriptome analyses at the seedling and germination stages. Two wheat cultivars, CM6005 (salt-tolerant) and KN9204 (salt-sensitive) were subjected to salt treatment, resulting in a total of 24 transcriptomes. Through expression-network analysis, we identified 17 modules, 16 and 13 of which highly correlate with salt tolerance-related phenotypes in the germination and seedling stages, respectively. Moreover, we identified candidate Hub genes associated with specific modules and explored their regulatory relationships using co-expression data. Enrichment analysis revealed specific enrichment of gibberellin-related terms and pathways in CM6005, highlighting the potential importance of gibberellin regulation in enhancing salt tolerance. In contrast, KN9204 exhibited specific enrichment in glutathione-related terms and activities, suggesting the involvement of glutathione-mediated antioxidant mechanisms in conferring resistance to salt stress. Additionally, glucose transport was found to be a fundamental mechanism for salt tolerance during wheat seedling and germination stages, indicating its potential universality in wheat. Wheat plants improve their resilience and productivity by utilizing adaptive mechanisms like adjusting osmotic balance, bolstering antioxidant defenses, accumulating compatible solutes, altering root morphology, and regulating hormones, enabling them to better withstand extended periods of salt stress.ConclusionThrough utilizing transcriptome-level analysis employing WGCNA, we have revealed a potential regulatory mechanism that governs the response to salt stress and recovery in wheat cultivars. Furthermore, we have identified key candidate central genes that play a crucial role in this mechanism. These central genes are likely to be vital components within the gene expression network associated with salt tolerance. The findings of this study strongly support the molecular breeding of salt-tolerant wheat, particularly by utilizing the genetic advancements based on CM6005 and KN9204.

Financial sustainability of circular innovations in SMEs. A case study from the fashion industry in Italy

Circular actions cannot be considered sustainable if their financial benefits are not demonstrated. While the environmental benefits of the circular economy have been widely studied, sustainable development from a financial point of view has been much less studied. In this paper we assess the financial benefits of circular innovations applied in the fashion industry that have been previously assessed as sustainable using the Life Cycle Assessment. The focus is on two innovative processes such as salt recovery and tannin baths reuse that reuse water, chemicals and raw materials in an Italian small company operating in the tanning industry. A cost benefit analysis was carried to evaluate the net contribution of these actions to the operating margin. Then we model a forward-looking cash flow projection in order to determine the fundamental value of circular investments. Through these practices, the company achieved an increase in operating profitability above 30% and the 10-year value of the salt recovery is 159,061.40 euros, while the reused tanning water equals just over one million euros. The results show unexpected and strong financial benefits that can leverage similar initiatives that would advance resource equity and finally promote a real and convenient industrial dedication to environmental guardianship.

Towards a zero liquid discharge process from brine treatment: Water recovery, nitrate electrochemical elimination and potential valorization of hydrogen and salts

This research addresses the issues related with treatment and valorization of brines and nitrate decontamination of surface and ground waters. The objective was to approximate to zero liquid discharge (ZLD) minimizing the environmental impact of brines of an electrodialysis reversal water treatment plant (EDRWTP) as an example. The innovative in flow process was developed from lab to pre-industrial scale and joined several main concepts: ion-exchange equilibrium for softening or demineralization of brines; reversed osmosis to recover suitable water and to enrich the waste in nitrate for efficient electrochemical reduction of NO3− to N2; valorization of subproducts by direct use or by precipitation; and assessment of the whole process by measuring in-line several parameters. The achieved softening was around 98 % and the recovered water from this current by reversed osmosis was 75 %. The brine of this step (25 %) contained around 1500 mg/L of nitrate and it was treated by electrochemical reduction with a Bi/Sn cathode providing a gas current of 60 % of initial nitrate reduced to N2, O2, H2O, NH3 and at least 97 % of H2. The aqueous current contained around 40 % of initial nitrate as ammonium and nitrite lower than 50 and 5 mg/L, respectively. Hypochlorite was added to this last current for oxidizing ammonium and nitrite to N2 and nitrate, respectively, being nitrate and ammonium lower than 50 and 5 mg/L, respectively. After the obtained water was demineralized and conducted to the EDRWTP inlet. The recovery of insoluble salts as calcium carbonate, reuse of saline solutions for the regeneration of process resins and the potential use of hydrogen generated as a by-product during the electrochemical reduction are other possible utilities.

Waste management and salt recovery from solid residue of tannery common effluent treatment plant

ABSTRACT The considerable amount of solid residue generated by the common effluent treatment plant (CETP) of tanneries needs adequate treatment and reclamation before ending up in the environment as solid waste. A sustainable process aiming at tannery CETP waste minimisation and its reuse for sodium chloride salt recovery is presented. The integrated approach consists of dissolution, decolorisation, filtration, evaporation, and crystallization as unit operations. Lab-scale parametric studies have been undertaken to investigate the effects of various parameters at different process stages on product (sodium chloride) yield and quality. The developed process resulted in the recovery of 93% NaCl, having a purity of ∼98.5%. The optimised operating conditions were tested on a bench-scale system (15 kg batch scale of solid residue) deploying solar energy for evaporation-crystallization, and process feasibility was established. An economic analysis was performed, and the techno-economic feasibility was demonstrated to produce 15,733 tons per annum (TPA) of NaCl from 20,000 TPA of solid residue. The techno-economic analysis favours the treatment of tannery CETP waste with the method specified. The proposed scheme can tackle waste management and reuse the recovered product in the tanning process.

Multicomponent steady-state modeling, performance optimization and prediction of cleaning frequency for treatment of cellulosic manmade fibre industry stream using polysodium 4- styrenesulfonate (PSS) incorporated nanofiltration membrane

Effect of polysodium 4-styrenesulfonate (PSS) in the skin layer on performance of nanofiltration (NF) membrane was analyzed for treatment of saline stream from manmade fiber industry. The NF membrane with 0.05 % (w/w) PSS concentration in aqueous phase had better hydrophilicity (contact angle: 330) and water flux of 27 L.m−2.h−1 along with significant salt rejection (Na2SO4: 90 %, CaSO4: 85 % and NaCl: 80 %) at transmembrane pressure 8.3 bar and crossflow rate 100 L.h−1. A long-term study with the wastewater showed that the intermittent cleaning of the membrane every 6 h led to 16 L.m−2.h−1 average permeate flux and sulfate rejection above 95 %.A two-component, steady-state model was used to quantify the performance of the selected membrane. Based on the fouling study, a semi-empirical theory was proposed to identify the cleaning frequency. The theory developed is useful for the operation, maintenance and recovery of the divalent salts from reject stream of such industry.

A novel combined process for enhancing soluble salt recovery and reducing pollutant diffusion in municipal solid waste incineration fly ash

There is a limited body of research on the recovery of soluble salts from municipal solid waste incineration fly ash (MSWI-FA), with challenges stemming from the effective management of residual heavy metals and dioxins. In this investigation, we propose using water-washing treatment for fly ash dechlorination and using CO2 aeration carbonation combined with ceramic membrane filtration to recover soluble salt resources from fly ash. This study investigated the impact of combined processes on fly ash soluble salt recovery, carbon dioxide capture and sequestration, heavy metal removal, and dioxin diffusion reduction. The findings revealed that the combined process can significantly enhance the rate of carbonation and the removal of heavy metals. Specifically, the removal rates of Pb and Zn reach 100%. The resulting CaCO3 precipitation particle size is smaller, averaging only approximately 4 μm, with greater surface porosity, higher heavy metal and dioxin content, and dioxin toxic equivalents as high as 8.11 ng TEQ/kg. Moreover, the dioxin content in the recovered mixed salt decreased, and its dioxin toxic equivalent was only 3.228.11 ng TEQ/kg. Consequently, the combined process of CO2 aeration combined with ceramic membrane filtration was used in conjunction to significantly reduce pollutants (heavy metals and dioxins) in the MSWI-FA recovered salt. This approach enhances the recyclable resource utilization of MSWI-FA and reduces the risk of pollution dispersal during MSWI-FA disposal and resource utilization.

Covalently doping polyaniline-based photothermal fabric for continuous recovery of salt and freshwater from seawater via solar-driven interfacial evaporation

Herein, we present a new three-step route to prepare a covalently doped polyaniline (PANI) -based photothermal fabric with high evaporation capacity. In which, polyacrylamide (PAM) was covalently grafted onto the cotton yarns coupling with poly(glycidyl methacrylate) via electron beam irradiation induced co-graft polymerization as primary graft layer, while PANI was subsequently grafted onto the primary graft layer in situ, which was pre-functionalized by 2-(4-aminophenyl)ethylamine, as secondary graft layer. It has been found that the PAM-doped PANI-based photothermal fabric achieved high evaporation rate 1.60 kg m−2 h−1 from pure water, 1.54 kg m−2 h−1 from 3.5 wt% NaCl solution, and 1.49 kg m−2 h−1 even in 10 wt% NaCl solution under 1 sun irradiation. Furthermore, the evaporation-induced salt crystallization did not appear on the surface of fabric, but preferentially occurred on the area of supporting platform off the fabric. This characteristic endowed the doped fabric with average recovery rate of freshwater at 1.54 kg m−2 h−1 and salt at 0.03 kg m−2 h−1 from simulated seawater. This work provides a novel strategy to the enhancement of conductive polymer based photothermal materials via covalently doping, which could popularize the application of solar-driven evaporation to resource recovery from saline waters.

Redox flow deionization using Prussian blue and functionalized ion exchange membrane for enhanced selective ion recovery

Flow electrode capacitive deionization (FCDI) is a newly developed water treatment technology that offers better performance than the original, solid electrode capacitive deionization (CDI). By eliminating the need for discharging process, FCDI provides much higher desalination capacity with a continuous desalination operation. Along with applications for salt removal, selective removal and recovery of specific ions are also prominent features of FCDI technology. Characteristics of electrodes and ion exchange membranes play a crucial role in controlling the selectivity of ions in an FCDI system. In this study, we demonstrated selective and continuous ion recovery by combining redox-active Prussian blue as flow electrodes and functionalized ion exchange membranes in FCDI configuration. Prussian blue selectively absorbs monovalent Na+ ions from Na+/Ca2+ mixtures through intercalation reaction, in which a smaller Stokes radius of Na+ ion is more favored to fit in the crystal lattice. Furthermore, such selectivity is much more enhanced through functionalization of a cation-exchange membrane (CEM) with polymer multilayers. A layer-by-layer method was used to deposit poly(allylamine hydrochloride) (PAH) and poly(styrene sulfonate) (PSS) on the CEM. Results showed that polymer multilayers changed the CEM from divalent to monovalent ion-affinity due to different ion sizes and charge density. The combination of Prussian blue and functionalized CEM raised the selectivity for sodium around 17 times compared to a control system (0.2 to 3.35). We believe that our approach can provide insight into various areas including resource production, recovery, removal of toxic ions, and material recycling using an FCDI system.

Optimized improvement of double-stage solar AES saline wastewater treatment system based on performance simulation and exergy analysis

Being an innovative, clean and high-efficiency double-stage solar air evaporating separation (AES) saline wastewater treatment system, it enables the full recovery of clean water and salt from saline wastewater. Nevertheless, there are still possibilities for optimized improvement in various aspects. Therefore, in this work, a well-established and accurately system simulation model is constructed, comprehensive performance is intensively analyzed, and different optimization and improvement methods are designed. Results demonstrate that among three potential improvements, “Improvement of three-stage switching operation” brings little effect, while “Improvement of distribution relationship” can effectively improve system adaptability to weather, particularly under overcast weather conditions. Moreover, “Improvement of regenerator” improves overall performance (gained output ratio (GOR), evaporation efficiency (EE) and overall system efficiency (ηsys), which are 20.11 %, 11.01 %, and 8.55 % higher than original system, respectively). Furthermore, the exergy analysis concludes that simultaneous implementation of “Improved distribution relations” and “Improved regenerators” is preferable. This improvement enhances system weather resilience and wastewater recycling capabilities in one fell swoop. This improved system can achieve an average GOR, ηsys and system exergy efficiency (ηex) of 2.588, 63.92 % and 2.849 %, respectively, throughout total summer months. Consequently, the best system improvement method is combining “Improvement of distribution relationship” with “Improvement of regenerator”.