Acidic Streams Research Articles

Flow-electrode capacitive separation of organic acid products and recovery of alkali cations after acidic CO2 electrolysis

Acidic CO2 electrolysis, enhanced by the introduction of alkali cations, presents a strategic approach for improving carbon efficiency compared to processes conducted in neutral and alkaline environments. However, a significant challenge arises from the dissolution of both organic acids and alkali cations in a strongly acidic feed stream, resulting in a considerable energy penalty for downstream separation. In this study, we investigate the feasibility of using flow-electrode capacitive deionization (FCDI) technology to separate organic acids and recover alkali cations from a strongly acidic feed stream (pH ~ 1). We show that organic acids, such as formic acid and acetic acid, are retained in molecular form in the separation chamber, achieving a rejection rate of over 90% under all conditions. Alkali cations, such as K+ and Cs+, migrate to the cathode chamber in ionic form, with their removal and recovery significantly influenced by their concentration and the pH of the feed stream, but responding differently to the types and concentrations of organic acids. The energy consumption for the removal and recovery of K+ is 4 to 8 times higher than for Cs+, and the charge efficiency is significantly influenced by the types of organic acid products and alkali cations. We conduct a series of electrochemical measurements and analyze the impedance spectroscopy, identifying that hindered mass transfer governed the electrode process. Our findings underscore the potential of FCDI as an advanced downstream separation technology for acidic electrocatalysis processes.

Zirconium titanium phosphonates for enhanced lanthanide recovery from acidic wastes

Metal phosphonates show promise for recovery of valuable lanthanide (Ln) elements from acidic waste streams due to their selectivity, high capacity, fast kinetics and chemical stability. To optimise these properties, a balance is needed between free phosphonate groups available to bind Ln and P-O-metal linkages to provide stability. This work demonstrates how astute choice of metal precursors can be used to control the phosphonate structure and maximise both sorption and stability. Relative to single metal zirconium phosphonate, mixed metal zirconium titanium phosphonate sorbents had more free phosphonate groups and greater porosity, increasing Ln capacity by 30 % and the kinetic rate constant by 90 %. Acid stability was also improved upon Ti inclusion. Use of metal propoxide and tert-butoxide precursors were also compared, revealing different reactivities with Zr versus Ti. Specifically, the tert-butoxide precursor increased P-O-Zr linkages and acid stability with Zr, but increased formation of leachable P-O-Na2 groups in the presence of Ti that decreased acid stability. The optimised zirconium titanium phosphonate sorbent used metal propoxide precursors and a Zr:Ti molar ratio of 1:1 to achieve (1) selectivity for Ln over Co, Sr and Cs, (2) sorption capacity of approximately 70 mg Eu/g, (3) fast kinetics with > 99 % sorption in 10 min and (4) retention of 60 % sorption capacity after contact with 5 M nitric acid. The enhanced chemical stability, capacity and kinetics achieved via incorporating Ti drastically improves the practicality of these sorbents for Ln recovery from acidic leachates of magnets, phosphors and other wastes.

(Invited) EDAC Labs: Carbon Removal via Acid-Base Electrochemistry

EDAC Labs(https://edaclabs.com/) uses the electrochemical production of acid and base to decarbonize the world through conventional direct air capture, enabling carbon-negative mining, and by providing technology for other applications such as direct ocean capture, ocean alkalinity enhancement, and enhanced weathering. EDAC Labs’ electrosynthesizer device creates acid and base at reduced energy cost of conventional processes. For conventional direct air capture developers, EDAC Labs provides technology that is low cost and operates at ambient temperature and pressure. For direct ocean capture and ocean alkalinity enhancement developers, EDAC Labs supplies electrochemistry solutions to developers that lower project costs. For metal mines, EDAC Labs provides technology that extracts valuable metals while sequestering carbon to achieve carbon-negative mining. The acid is used to start the recovery of valuable metals from mine tailings, and the base is used to capture CO2 from air. The acid and base streams are then combined to extract metals that can be sold for applications such as batteries, and to create solid carbonates, which permanently store CO2. Figure 1

Unlocking Value from Municipal Solid Waste Incineration Ash: Electrochemical and Chemical Approaches for Materials Recovery

Nowadays, in the U.S. more than 6.6 million tons of hazardous solid residue, called municipal solid waste incineration (MSWI) ash is annually generated in waste-to-energy (WTE) plants for producing electricity and reducing landfill volume. This ash cannot be further utilized for beneficial applications, so it is mostly buried and has a negative value with the cost of a disposal fee. Moreover, the economics of MSWI is challenged by the decreasing cost of renewableelectricity. However, WSWI ash represents a unique opportunity for valuable element recovery, with the embodied value ranging from $100-400/tonne. We propose an electrochemical and chemical process for mining MSWI ash that utilizes electricity from the WTE plant toelectrolytically produce acid and base streams for materials recovery and refining. We establish a sequential process of electrochemical extraction and chemical precipitation, and successfully recover Cu, Pb, Zn, Mg, Ca, Fe, Al, with a purified silica co-product. Recovery of >90% of the targeted elements at purities >90% is demonstrated. The industry-scale technoeconomic analysis shows our proposed technology will realize the possibility of extracting the embodied mineral value with net positive returns that significantly exceed the combined value of WTE electricity sales and landfilling cost.

FePO4.2H2O recovery from acidic phosphate-rich waste streams

Phosphorous not only needs to be removed to prevent eutrophication of wastewater effluent receiving surface water bodies, but it also has to be recovered as a scarce finite reserve. Phosphorus chemical precipitation as NH4MgPO4·6H2O, Ca3(PO4)2, or Fe3(PO4)2 ·8H2O is the most common method of phosphorus recovery from phosphorus-rich streams. These minerals ideally form under neutral to alkaline pH conditions, making acidic streams problematic for their formation due to the need for pH adjustments. This study proposes FePO4 .2H2O (strengite-like compounds) recovery from acidic streams due to its simplicity and high efficiency, while also avoiding the need for pH-adjusting chemicals. The effect of initial pH, temperature, Fe (III) dosing rates, and Fe (II) dosage under different oxidation conditions (pO2 = 0.2, 1, 1.5 bar, different H2O2 dosing rates) on phosphorus recovery percentage and product settleability were evaluated in this study. The precipitates formed were analyzed using optical microscopy, SEM, XRD, SQUID, Raman, and ICP. Experiments showed that Fe (III) dosing achieved phosphorus recovery of over 95 % at an initial pH of 3 or higher, and the product exhibited poor settleability in all initial pH (1.5-5), and temperature (20–80 °C) tests. On the other hand, Fe (II) dosage instead of Fe (III) resulted in good product settleability but varying phosphorus recovery percentages depending on the oxidation conditions. The novelty of the study lies in revealing that the Fe (II) oxidation rate serves as a crucial process-design parameter, significantly enhancing product settleability without the requirement of carrier materials or crystallizers. The study proposes a novel strategy with controlled Fe2+-H2O2 dosing, identifying an Fe (II) oxidation rate of 4.7 × 10−4 mol/l/min as the optimal rate for achieving over 95 % total phosphorus recovery, along with excellent settleability with a volumetric index equal to only 8 ml/gP.

Accelerated corrosion of low carbon steel by oscillatory acidic streams generated with a bio-inspired claw device.

A mechanical device inspired by the pistol shrimp snapper claw was developed. This technology features a claw characterized by a periodic opening/closing motion, at a controlled frequency, capable of producing oscillating flows at transitional Reynolds numbers. An innovative method was also proposed for determining the corrosion rate of carbon steel samples under oscillating acidic streams (aqueous solution of HCl). By employing very-thin carbon steel specimens (25 μm thickness), with one side coated with Zn and not exposed to the stream, it became possible to electrochemically sense the Zn surface once the steel sample was perforated, thus providing the average dissolution rate into the most relevant pit on the steel surface. Furthermore, a laser light positioned beneath the metallic sample, along with a camera programmed to periodically capture images of the steel surface, facilitated the accurate counting of the number of newly formed pits. The system consisting of the thin steel sample and the Zn coating can be seen as a type of corrosion sensor. Furthermore, the proposed laser illumination method allows corroborating the electrochemical detection of pits and also establishing their location. The techniques crafted in this study pave the way for developing alternative corrosion sensors that boast appealing attributes: affordability, compactness, and acceptable accuracy to detect in time and space localized damage.

Bipolar membrane electrodialysis for nutrient recovery from anaerobic digestion dewatering sidestream

Anaerobic digestion (AD) offers an efficient means for treating sludge generated in wastewater treatment plants (WWTPs), but nutrient-rich AD dewatering sidestream contributes as much as 30 % of the overall nutrient loading of WWTPs. Several electrochemical approaches are being developed as a sidestream treatment strategy to prevent return of nutrients to WWTP headworks and recover them for fertilizer production. One such method is to produce acids and bases, essential chemicals necessary to facilitate nutrient recovery, using bipolar membrane electrodialysis (BMED). In this study we show simultaneous separation of nutrients and production of acid/base streams with an additional consideration for increasing the concentration of ammonium and phosphate in the final product stream by systematically altering compartment flow rates and hence the retention time of each stream. Using a three-compartment BMED system with a synthetic sidestream containing 50 mM NH3-N and 2 mM PO4-P, we achieved up to 80 % ammonia removal (via a cation exchange membrane) and up to 60 % phosphate removal (via an anion exchange membrane) at a productivity of 34.2 L m−2 h−1. Separated ammonia was recovered (>90 %) in a subsequent membrane contactor (MC) that was fed with acid and base streams produced by the BMED unit. A phosphate recovery > 80 % was achieved by chemical precipitation (CP). In a combined BMED-MC-CP process, the concentrated final product contained 333.9 mM NH3-N and 3.1 mM PO4-P with an energy consumption of 8.9 kWh kg−1 N recovered. These results illustrate that the BMED-based treatment train is a promising strategy for nutrient recovery from AD dewatering sidestream.

Biotransformation of maize bran-derived ferulic acid to vanillin using an adapted strain of Amycolatopsis sp. ATCC 39116.

Maize bran, an agro-processing waste residue, is a good source of ferulic acid that can be further valorized for vanillin production. However, extraction of ferulic acid from natural sources has been challenging due to low concentrations and intensive extraction procedures. In the present work, ferulic acid streams (purities ranging from 5% to 75%) extracted from maize bran using thermochemical methods were evaluated for biotransformation to vanillin, employing Amycolatopsis sp. as a whole-cell biocatalyst. Initial adaptation studies were critical in improving ferulic acid assimilation and its conversion to vanillin by 65% and 56%, respectively by the fourth adaptation cycle. The effect of cell's physiological states and vanillic acid supplementation on vanillin production was studied using standard ferulic acid as a substrate in an effort to achieve further improvement in vanillin yield. In the presence of vanillic acid, 18 h cultured cells using 2 g/L of standard and isolated ferulic acid produced vanillin concentrations of up to 0.71 and 0.48 g/L, respectively. Furthermore, intermediates involved in the ferulic acid catabolic pathway and their interrelations were studied using GC-MS analysis. Results indicated that two different routes were involved in the catabolism of standard ferulic acid, and similar metabolic routes were observed for an isolated ferulic acid stream. These findings effectively evaluated isolated ferulic acid for sustainable vanillin production while reducing agro-industrial waste pollution.

Metal-oxide precipitation influences microbiome structure in hyporheic zones receiving acid rock drainage.

In streams receiving acid-rock and mine drainage, the abundant precipitation of iron minerals can alter how groundwater and surface water mix along streams (in what is known as the "hyporheic zone") and may shape the distribution of microbial communities. The findings presented here suggest that neutral pH streams with large, well-mixed hyporheic zones may harbor and transport diverse microorganisms attached to particles/colloids through hyporheic pore spaces. In acidic streams where metal oxides clog pore spaces and limit hyporheic exchange, iron-oxidizing bacteria may dominate and phylogenetic diversity becomes low. The abundance of iron-oxidizing bacteria in acid mine drainage streams has the potential to contribute to additional clogging of hyporheic pore spaces and the accumulation of toxic metals in the hyporheic zone. This research highlights the dynamic interplay between hydrology, geochemistry, and microbiology at the groundwater-surface water interface of acid mine drainage streams.

Separation of rhodium from iridium through synergistic solvent extraction

There are currently few effective processes for the solvent extraction of rhodium from hydrochloric acid streams, and none that allow rhodium to be selectively extracted over iridium. Realizing this goal could allow rhodium to be recovered earlier in a typical platinum group metal (PGM) refining flowsheet and reduce the environmental impact of PGM refining. In this work, we show that a synergistic combination of a tert-alkyl primary amine LA and various inner-sphere ligands L can be used to recover rhodium via the complex [RhCl5L].HLA2. Although we show that rhodium is extracted by several extractant combinations, it is only readily stripped from the amine/amide synergistic mixture. As this extraction relies on the inner-sphere coordination of the amide to the metal, this process also demonstrates a route to obtain preferential extraction of rhodium over more inert iridium chloridometalates under industrially relevant conditions.

Shrinking pupal cocoons of Rhyacophila lezeyi (Trichoptera, Rhyacophilidae) in a highly acidic stream during the summer season

Shrinking pupal cocoons of Rhyacophila lezeyi were often found during summer in Shibukuro Stream, a highly acidic mountain stream in northern Japan (pH = 2.82 on average). We performed both field surveys and laboratory rearing experiments to clarify the mechanisms of R. lezeyi cocoon shrinkage. The R. lezeyi cocoon shrinkage proportion increased in years with high stream water temperatures and was related to water temperatures before and after pupation at the study site. Approximately 90% of the prepupae and pupae inside the shrinking cocoons died during the rearing experiment, implying that cocoon shrinkage caused by high water temperature strongly influenced R. lezeyi pupal survival. Laboratory experiments showed that R. lezeyi’s pupal cocoon membranes were semi-permeable and that the cocoon fluids were always hyperosmotic, indicating that water molecules can continuously enter the cocoon fluids from the stream water until the turgor of the cocoon wall is reached. However, the shrinking cocoons showed lower fluid volume and higher osmolarity than the normal turgescent cocoons. The reduction of osmotic gradient across the membrane during decreased stream flow due to less precipitation and/or the damage to the cocoon membrane and pupal body from high and fluctuating water temperatures and low pH are possible mechanisms for R. lezeyi pupal cocoon shrinkage.

Catalytic upcycling of waste bisphenols via tandem amination-ammonolysis to high value diamines

Hydrogenated methylene dianiline (H12MDA) is a valuable precursor for thermoplastic polyurethane. Traditionally, H12MDA is obtained by hydrogenation of methylene dianiline (MDA). However, the route from aniline to MDA produces large acidic waste streams linked to the nitration of benzene and the HCl-catalyzed reaction with formaldehyde, as well as a poor selectivity for the 4,4′-isomer in the condensation reaction with formaldehyde. Herein, we report a green and efficient amination process for synthesis of H12MDA starting from (waste) bisphenols. Palladium on moderately acidic catalyst supports (carbon, Al2O3, ZrO2) provided excellent yields of H12MDA (>97%) in short reaction times (3 h) at 200 °C, with limited addition of H2 and NH3. It was found that the reaction partially proceeds via a secondary amine intermediate. A high dispersion of palladium is essential to achieve high yields of the desired H12MDA. Finally, the use of polycarbonate as an alternative feedstock for H12MDA was demonstrated via a tandem ammonolysis-amination process.

Electrochemically Mediated Ammonia Removal and Recovery from Wastewater Using Functional Membranes

Wastewater treatment plants (WWTPs) typically use anaerobic digestion (AD) to treat sludge, but ammonia produced during AD process returns to the headworks of WWTPs. The amount of ammonia in the liquid stream produced after dewatering the stabilized sludge, commonly referred to as dewatering sidestream, could contribute as high as 20% of the overall ammonia loading to WWTPs. Several sidestream treatment technologies are being developed not only to prevent additional ammonia inputs to WWTPs, but also to valorize ammonia for fertilizer production. Electrochemically mediated processes can achieve this goal in two simultaneous steps: (1) ammonium separation from wastewater through a cation-exchange membrane and (2) ammonium-to-ammonia conversion for its recovery by membrane stripping. Although electrochemical reactions in electrodialysis or flow-electrode capacitive deionization have been shown to drive the separation and increase the solution pH, an acid solution must be externally fed in the subsequent stripping process. Here, we demonstrated the use of bipolar membrane electrodialysis (BMED) to separate ammonium while simultaneously producing acid and base streams. Using a three-compartment BMED cell (effective repeating unit area = 29.2 cm2) with a synthetic sidestream containing 50 mM total ammonia nitrogen (TAN), we achieved TAN removal up to 80% with energy consumption less than 10 kWh kg−1 N at a productivity of 34.2 L m−2-repeating unit membrane area h−1 (LMH). The separated ammonia was recovered (>90%) in a subsequent membrane contactor that was fed with acid and base streams produced from the BMED cell. We specifically focused on increasing TAN concentration in the final product stream by changing relative flow rate of acid/base streams, which allowed for concentrating TAN nearly 8 times greater than the feed. These results show the use of BMED coupled with membrane stripping enables ammonia recovery without the need for chemical inputs, representing a promising sidestream treatment technology.

A New Acidity-Based Approach for Estimating Total Dissolved Solids in Acidic Mining Influenced Water

In natural waters, total dissolved solids (TDS) are usually estimated from electrical conductivity (EC) by applying a conversion factor (f). However, defining this conversion factor for mining influenced water is more complex since this type of water is highly mineralized and has complex chemical matrices. So, the present work aimed to establish a new conversion factor to estimate TDS from the classic parameters usually analyzed for the hydrochemical characterization of these contaminated waters. A total of 121 mining influenced water samples were collected in three mining areas representing pollution scenarios, such as acidic streams, acidic lagoons, and pit lakes. The parameters analyzed were pH, EC, sulfate, acidity, and TDS. The statistical analysis showed that TDS and acidity are related, with a high and significant correlation (r ≥ 0.964, ρ < 0.001), suggesting that this parameter could be an appropriate indicator to estimate the TDS. Moreover, although acidity analysis also involves laboratory work, the time and effort required are considerably less than the gravimetric determination of TDS. Hierarchical cluster analysis applied to these samples allowed the definition of seven classes, and their specific fmedian was calculated employing TDS/Acidity. Then, seven conversion factors were obtained for mining influenced water based on sulfate concentration and acidity degree.

Catalyst-anchored secondary polymerization for highly permeable acid-resistant nanofiltration membrane preparation

Nanofiltration (NF) is considered a competitive technique for acidic stream treatments. However, poorly reactive acid-resistant monomers normally cause thick and uneven separation layers with ultra-low permeability. Herein, catalyst-anchored secondary polymerization is employed after the interfacial polymerization (IP) reaction between trimesoyl chloride (TMC) and 3-aminobenzenesulfonamide (ABSA) to fabricate an extremely acid-resistant NF membrane. Acylation catalysts in ethanol are grafted on the nascent layer by reacting with residual acyl chloride groups to enhance the monomer reactivity, while the ethanol-induced nascent layer structure regulation greatly improves the surface uniformity. Benefiting from the improved self-inhibition effect and optimized phase integrity of the modified IP process, the resulting acid-resistant membrane has unprecedented water permeance (up to 31.4 Lm−2h−1bar−1), desirable Na2SO4 rejection (92.8%), high dye/H+ selectivity and impressive acid stability (20 wt% of H2SO4 for 50 days), outperforming almost all advanced acid-resistant NF membranes. Our work provides a versatile approach for the synthesis of high-performance specialty membranes.

A Review of Opportunities and Methods for Recovery of Rhodium from Spent Nuclear Fuel during Reprocessing

Rhodium is one of the scarcest, most valuable, and useful platinum group metals, a strategically important material relied on heavily by automotive and electronics industries. The limited finite natural sources of Rh and exponentially increasing demands on these supplies mean that new sources are being sought to stabilise supplies and prices. Spent nuclear fuel (SNF) contains a significant quantity of Rh, though methods to recover this are purely conceptual at this point, due to the differing chemistry between SNF reprocessing and the methods used to recycle natural Rh. During SNF reprocessing, Rh partitions between aqueous nitric acid streams, where its speciation is complex, and insoluble fission product waste streams. Various techniques have been investigated for Rh recovery during SNF reprocessing for over 50 years, including solvent extraction, ion exchange, precipitation, and electrochemical methods, with tuneable approaches such as impregnated composites and ionic liquids receiving the most attention recently, assisted by more the comprehensive understanding of Rh speciation in nitric acid developed recently. The quantitative recovery of Rh within the SNF reprocessing ecosystem has remained elusive thus far, and as such, this review discusses the recent developments within the field, and strategies that could be applied to maximise the recovery of Rh from SNF.

Modulating Anion Nanotraps via Halogenation for High-Efficiency 99TcO4-/ReO4- Removal under Wide-Ranging pH Conditions.

Efficient and sustainable methods for 99TcO4- removal from acidic nuclear waste streams, contaminated water, and highly alkaline tank wastes are highly sought after. Herein, we demonstrate that ionic covalent organic polymers (iCOPs) possessing imidazolium-N+ nanotraps allow the selective adsorption of 99TcO4- under wide-ranging pH conditions. In particular, we show that the binding affinity of the cationic nanotraps toward 99TcO4- can be modulated by tuning the local environment around the nanotraps through a halogenation strategy, thereby enabling universal pH 99TcO4- removal. A parent iCOP-1 possessing imidazolium-N+ nanotraps showed fast kinetics (reaching adsorption equilibrium in 1 min), a high adsorption capacity (up to 1434.1 ± 24.6 mg/g), and exceptional selectivity for 99TcO4- and ReO4- (nonradioactive analogue of 99TcO4-) removal in contaminated water. By introducing F groups near the imidazolium-N+ nanotrap sites (iCOP-2), a ReO4- removal efficiency over 58% was achieved in 60 min in 3 M HNO3 solution. Further, introduction of larger Br groups near the imidazolium-N+ binding sites (iCOP-3) imparted a pronounced steric effect, resulting in exceptional adsorption performance for 99TcO4- under super alkaline conditions and from low-activity waste streams at US legacy Hanford nuclear sites. The halogenation strategy reported herein guides the task-specific design of functional adsorbents for 99TcO4- removal and other applications.

Non-dispersive solvent extraction as an alternative for sulfuric acid and copper recycling from membrane distillation concentrate of gold mining wastewater

The wastewater from the pressure oxidation process is a complex stream enriched in sulfuric acid and dissolved metallic species, conventionally treated by neutralization, a technique that does not allow for by-product recovery. Previous studies focused on water recovery from the wastewater by membrane distillation and the concern related to concentrate production after water is recovered is now addressed by using hollow-fiber membrane contactors in non-dispersive solvent extraction processes intended for sulfuric acid and copper recycling. Tris(2-ethylhexyl)amine (TEHA), Aliquat 336, and Lix 84-I were used as extractants, the first two for acid recovery and the latter for copper. It was investigated the contribution of different organic phases flow rate (4–12 cm3/s), organic phase composition (5–15 wt%), and temperature (30–60 °C) on the performance of hollow fiber membrane contactors, with an in-depth disclosure of mass transfer phenomena limiting the extraction efficiency. For both acid and copper recovery, a reduction in viscosity forces prevails over the decrease in inertial forces, improving the flow regime. Even so, the predominant mechanism was the diffusive transport of both solutes into the fluid, across the membrane pores, rather than being carried along by the aqueous phase flow. The acid and copper recovery from membrane distillation concentrate achieved values greater than 91%, which represents an acid stream containing 5.86 g-H2SO4/L and an aqueous copper solution with a concentration of 269.0 mg/L, both at high purity. It was discussed different opportunities for their reuse within the gold ore processing circuit and challenges related to their external commercialization. Preliminary economic analysis suggested that the mineral acid would present slightly higher costs than currently practiced (0.54 US$/kgH2SO4; market prices: 0.03–0.11 US$/kgH2SO4), although the operational costs related to copper were comparable with market prices (11.58 US$/kgCu; market prices: 10.31 US$/kgCu). In a broad context, the opportunity for acid and sulfuric acid recycling has the potential to extend sustainability in the mining sector.

Bipolar Membrane Capacitive Deionization for pH-Assisted Ionic Separations

Selective ionic separations represent an increasingly important technical area for the strategic interests of the U.S. economy─for example, securing critical minerals and materials and circular economy aspirations that include recovering organic acids from processed biomass. This work disseminates bipolar membrane (BPM) capacitive deionization for selective ionic separations from multicomponent, ionic species mixtures. The selective separations are guided by the Pourbaix diagram and acid–base equilibria principles. BPM capacitive deionization was demonstrated to generate alkaline or acidic process streams depending upon the location of the BPM in the electrochemical cell. The role of system operating parameters, such as the cell voltage, residence time, and feed concentration on effluent stream pH was studied. It was observed that the pH adjustment in BPM-CDI/MCDI (MCDI, membrane capacitive deionization) was more sensitive to the cell voltage when compared to the process stream residence time and salt feed concentration. The BPM-MCDI gave over 6 times higher percentage of copper(II) removal when compared to sodium ion removal from brine mixtures. Finally, BPM-MCDI demonstrated over 40% greater removal for copper ions from brine mixtures and fivefold higher removal for itaconic acid from brine mixtures when benchmarked against a traditional flow-by-MCDI setup.

Bio-functional collagen/casein/chitosan scaffolds regulated porous TFC membrane for acid recovery

Applications of environmentally friendly and low-cost biomaterials for membrane preparation offer unparalleled advantages over traditional synthetic polymer membrane. Herein, a novel collagen/casein/chitosan composite material was designed to synthesize TFC membrane for acid recovery from acidic waste stream. A vacuum filtration method was used to precious adjust the thickness of the functional layer while glutaraldehyde was adopted as crosslinking agent to preserve surface charge property of anion-exchange membranes (AEM) at acidic conditions. The electrostatic interactions and hydrogen bonding of these biopolymers endowed the TFC membrane with enhanced stability. At optimized conditions with 0.15 mL collagen/casein/chitosan composites decoration, the TFC membrane with a functional layer thickness of around 628.4 nm exhibited an excellent acid permeance (UH+ = 0.034 m h−1) and a high H+/ Fe2+ separation factor up to 33.8. This facile strategy provides a useful guideline for constructing highly efficient TFC membrane for acid recovery and broadens the application of biomaterials for membrane application at harsh environments.