Mixed Ion Solutions Research Articles

Efficient chromium(VI) removal using trioctylmethylammonium salicylate as the carrier in polymer inclusion membranes.

In this study, the ionic liquid (IL) trioctylmethylammonium salicylate (TOMAS) was prepared and incorporated into a polymer inclusion membrane (PIM) based on cellulose triacetate (CTA) as the polymer for the removal of Cr(VI). Various parameters including the effect of membrane composition (plasticizer and carrier concentration) as well as variables affecting both the feed phase and receiving solution have been investigated. Optimal results were achieved with a PIM made of 50% CTA and 50% TOMAS (% in mass) without the addition of any plasticizer. Using this PIM, Cr(VI) was effectively transported from a feed solution consisting of 10mg L-1 Cr(VI) in 0.01mol L-1 NaNO3 at pH = 2, to a receiving solution containing 0.1mol L-1 NaOH. The transport of Cr(VI) was not affected by the presence of other metals, such as Cr(III), Cd(II), Zn(II), Cu(II), and Ni(II), and a selective recovery rate of 93.61% for both single-ion and mixed-ion solutions after 24h of processing was obtained. Finally, the stability of the membrane was also investigated, with a slight decrease in efficiency observed after 5days of reuse.

Thiol-Functionalized Adsorbents through Atomic Layer Deposition and Vapor-Phase Silanization for Heavy Metal Ion Removal.

The removal of toxic heavy metal ions from water resources is crucial for environmental protection and public health. In this study, we address this challenge by developing a surface functionalization technique for the selective adsorption of these contaminants. Our approach involves atomic layer deposition (ALD) followed by vapor-phase silanization of porous substrates. We utilized porous silica gel powder (∼100 μm particles, 89 m2/g surface area, ∼30 nm pores) as an initial substrate. This powder was first coated with ∼0.5 nm ALD Al2O3, followed by vapor-phase grafting of a thiol-functional silane. The modified powder, particularly in acidic conditions (pH = 4), showed high selectivity in adsorbing Cd(II), As(V), Pb(II), Hg(II), and Cu(II) heavy metal ions in mixed ion solutions over common benign ions (e.g., Na, K, Ca, and Mg). Langmuir adsorption isotherms and breakthrough adsorption studies were conducted to assess heavy metal binding affinity and revealed the order of Cd(II) < Pb(II) < Cu(II) < As(V) < Hg(II), with a significantly higher affinity for As(V) and Hg(II) ions. Time-dependent uptake studies demonstrated rapid removal of heavy metal ions from aqueous environments, with Hg(II) exhibiting the fastest adsorption kinetics on thiol-modified surfaces. These findings highlight the potential of ALD and vapor-phase silanization to create effective adsorbents for the targeted removal of hazardous contaminants from water.

Enhanced heavy metal adsorption capacity of surface-functionalized Philippine natural zeolite in simulated wastewater

The adsorption efficiency of surface-functionalized Philippine natural zeolite (PNZ) for heavy metal uptake from single and mixed metal ion-simulated wastewater solution is reported in this work. Atomic adsorption spectroscopy (AAS) findings revealed that NaCl-modified PNZ (MPNZ) exhibited the highest zinc ion adsorption of 99.96 % while PNZ yielded an adsorption of 95.61 %. The adsorption isotherms of raw PNZ and MPNZ both show similar shapes that reflect Type IV adsorption-desorption isotherms with Type H2 hysteresis loop which can be observed for micro-mesoporous materials (pore containing 2–50 nm). An increase in PNZ pore size from 10.11 nm to 13.36 nm for NaCl-PNZ and 15.59 for NaOH-PNZ is observed after alkaline treatment. EDS confirmed the decrease in Si/Al ratio from 4.02 to 3.76, indicative of possible higher negative charge in the PNZ framework which is favorable for an enhanced Coulombic or electrostatic interaction with the cationic heavy metals being detected in this study. MPNZ demonstrated an adsorption capacity of 99.96 % for copper in mixed-ion solution while 88.49 % and 86.67 % were obtained for zinc and nickel, respectively. These values are higher compared to PNZ having only 32.21 % uptake for zinc and 38.00 % for nickel. A hierarchy of the average metal adsorption capacity showed the order: copper > nickel > zinc. Rapid adsorption at the first hour of the adsorption reaction was attained in all solutions while samples with pH 9 exhibited the highest Ni2+ and Zn2+ percent removal. Moreover, the increase in initial solution concentration led to lower adsorption efficiency and the maximum uptake was attained at 100 ppm. The equilibrium data of adsorption and mechanism were suitably described by Langmuir isotherm model. With these, surface functionalization of PNZ has further enhanced its cationic adsorption capacity on heavy metals in both single and mixed-ion solution having promising potential for wastewater remediation.

Toward Selective Transport of Monovalent Metal Ions with High Permeability Based on Crown Ether-Encapsulated Metal-Organic Framework Sub-Nanochannels.

Achieving selective transport of monovalent metal ions with high precision and permeability analogues to biological protein ion channels has long been explored for fundamental research and various applications, such as ion sieving, mineral extraction, and energy harvesting and conversion. However, it still remains a significant challenge to construct artificial nanofluidic devices to realize the trade-off effects between selective ion transportation and high ion permeability. In this work, we report a bioinspired functional micropipet with in situ growth of crown ether-encapsulated metal-organic frameworks (MOFs) inside the tip and realize selective transport of monovalent metal ions. The functional ion-selective micropipet with sub-nanochannels was constructed by the interfacial growth method with the formation of composite MOFs consisting of ZIF-8 and 15-crown-5. The resulting micropipet device exhibited obvious monovalent ion selectivity and high flux of Li+ due to the synergistic effects of size sieving in subnanoconfined space and specific coordination of 15-crown-5 toward Na+. The selectivity of Li+/Na+, Li+/K+, Li+/Ca2+, and Li+/Mg2+ with 15-crown-5@ZIF-8-functionalized micropipet reached 3.9, 5.2, 105.8, and 122.4, respectively, which had an obvious enhancement compared to that with ZIF-8. Notably, the ion flux of Li+ can reach up to 93.8 ± 3.6 mol h-1·m-2 that is much higher than previously reported values. Furthermore, the functional micropipet with 15-crown-5@ZIF-8 sub-nanochannels exhibited stable Li+ selectivity under various conditions, such as different ion concentrations, pH values, and mixed ion solutions. This work not only provides new opportunities for the development of MOF-based nanofluidic devices for selective ion transport but also facilitates the promising practical applications in lithium extraction from salt-like brines, sewage treatment, and other related aspects.

Adsorption of Hg2+/Cr6+ by metal-binding proteins heterologously expressed in Escherichia coli

BackgroundRemoval of heavy metals from water and soil is a pressing challenge in environmental engineering, and biosorption by microorganisms is considered as one of the most cost-effective methods. In this study, the metal-binding proteins MerR and ChrB derived from Cupriavidus metallidurans were separately expressed in Escherichia coli BL21 to construct adsorption strains. To improve the adsorption performance, surface display and codon optimization were carried out.ResultsIn this study, we constructed 24 adsorption engineering strains for Hg2+ and Cr6+, utilizing different strategies. Among these engineering strains, the M’-002 and B-008 had the strongest heavy metal ion absorption ability. The M’-002 used the flexible linker and INPN to display the merRopt at the surface of the E. coli BL21, whose maximal adsorption capacity reached 658.40 μmol/g cell dry weight under concentrations of 300 μM Hg2+. And the B-008 overexpressed the chrB in the intracellular, its maximal capacity was 46.84 μmol/g cell dry weight under concentrations 500 μM Cr6+. While in the case of mixed ions solution (including Pb2+, Cd2+, Cr6+ and Hg2+), the total amount of ions adsorbed by M’-002 and B-008 showed an increase of up to 1.14- and 4.09-folds, compared to the capacities in the single ion solution.ConclusionThe construction and optimization of heavy metal adsorption strains were carried out in this work. A comparison of the adsorption behavior between single bacteria and mixed bacteria systems was investigated in both a single ion and a mixed ion environment. The Hg2+ absorption capacity is reached the highest reported to date with the engineered strain M’-002, which displayed the merRopt at the surface of chassis cell, indicating the strain’s potential for its application in practical environments.

Preparation and characterization of P-type zeolite for adsorption of Cr3+, Ni2+, and Co2.

Acid-washed coal fly ash (AW-CFA) was subjected to wet grinding activation followed by hydrothermal crystallization to synthesize P zeolite (FAZ-P). The FAZ-P obtained at 120°C for 24h exhibited a maximum relative crystallinity of 93.15% and was employed for the adsorption of Cr3+, Ni2+, and Co2+ from aqueous solutions. The zeolitization of coal fly ash (CFA) leads to an increase in specific surface area to 44.00 m2/g, resulting in the formation of nano-sized P zeolite crystals with uniformly narrow fissures and sizes within the range of 10-30nm. Adsorption experimental results indicate that FAZ-P exhibits maximum adsorption capacities of 49.03mg/g for Cr3+, 22.20mg/g for Ni2+, and 27.25mg/g for Co2+. The adsorption equilibrium data for both mixed and single-metal ion solutions conform to the Langmuir model, with the affinity sequence for heavy metal ions being Cr3+ > Co2+ > Ni2+. The pseudo-first-order and pseudo-second-order kinetic models effectively described the adsorption behavior of Cr3+, Ni2+, and Co2+. Increasing the initial pH value of the solution significantly enhanced the adsorption capacity of the adsorbent for heavy metal ions. The removal mechanism of metal ions involves both adsorption and ion exchange processes. The thermodynamic parameters indicated that the adsorption process was spontaneous and endothermic.

A multi-channel optical sensing system based on back propagation neural network for mixed ion solution

As one of the mainstream sensing methods in the field, optical sensing has the characteristics of non-contact, anti-interference and fast transmission. The combination of multi-channel sensing and optical detection technology can realize multi-dimensional and multi-parameter detection in real-time. In this paper, we propose a portable multi-channel optical sensing system with compact structure, low cost, low detection limit and strong anti-interference ability for the detection of heavy metal concentration in water environment. A detection system based on back propagation neural network is designed, and a series of algorithms and related optical paths are used to achieve online simultaneous detection and calculation of different ion concentrations in mixed solutions. The neural network algorithm is introduced in the system to reduce the error, and improves the detection efficiency of mixed ion concentration, and further improves the detection performance of the system. It has unique advantages in the field of concentration measurement for mixed ion solutions.

Ammonium phosphomolybdate-modified UiO-66 as an efficient adsorbent for the selective removal of 137Cs from radioactive wastewater

137Cs is a radioactive pollutant in the production of wastewater from nuclear power plants. In this study, a rapid and simple in-situ synthesis new method was employed to prepare a novel AMP-functionalized UiO-66 composite material for the selective capture of 137Cs from low-level radioactive wastewater. Characterization techniques such as SEM-EDS, FTIR, XRD, TG, and BET were used to confirm the successful loading of AMP on the surface of UiO-66. UiO-66/AMP showed a good removal effect in pH4-11. At pH7, the effects of different parameters, such as the initial Cs concentration, the ratio of the amount of adsorbent to the volume of solution, and the adsorption time were investigated. The adsorption efficiency is 96.7%, the maximum adsorption capacity is 94.9 mg/g and has fast adsorption kinetics (90% Cs+ removal within 5 min). The adsorption data conformed to the pseudo-second-order kinetic model and Langmuir isotherm model, suggesting a monolayer homogeneous adsorption process. XPS helps confirm that the adsorption mechanism is the ion exchange between Cs+ and NH4+ ions. Particularly, in the adsorption experiments of 137Cs, UiO-66/AMP demonstrated good selectivity (KdCs: 5.8 × 103 ∼ 1.26 × 104 mL/g) towards trace Cs+ in a mixed ion solution with a molar ratio of 1 (Cs): 2.18 × 1015 (Na): 4.6 × 1014 (K): 2 × 1014 (Mg): 2 × 1014 (Ca), indicating its potential for selective capture of 137Cs from low-level liquid waste (LLLW).

Adsorption prospects of ultrafine, cubic 8 mol.% Y2O3‐stabilized ZrO2 nanoparticles

AbstractYttria‐stabilized zirconia (YSZ), although well known for a lot of excellent engineering applications, has limited footprints in the field of adsorption/dye removal. Through this work, we demonstrate the remarkable efficacy (adsorption capacity ∼550 mg/g) of 8 mol.% YSZ nano‐adsorbents for toxic azo‐dye (e.g., Congo red) removal. The consistency of our adsorption experiments was validated with the help of a series of tests, such as regeneration (via thermal and chemical routes), in real‐life river water, with mixed ion solution, and under varied pH (3–11). Noteworthy is also that the commercial trademark composition (with the same dopant concentration) showed little/no adsorption. Our success of the adsorption experiments is credited to the multitude of factors, namely, size refinement ∼6 nm, retainment of phase‐pure cubicity, and enhanced surface area (155 m2/g), which eventually led to the generation of massive oxygen vacancies on our synthesized doped‐zirconia surfaces.

Preparation of solar photo-thermal driven aerogel and clarification of the mechanism for enhanced uranium adsorption

The oceans contain a significant amount of uranium, a valuable resource for nuclear power and fuel applications. However, current technologies for extracting uranium from seawater have limitations, including low efficiency and high energy consumption. Aerogels are promising materials for uranyl ion adsorption due to their high porosity and abundant active sites. This study presents a novel approach for efficient uranium extraction from seawater using a full-fiber-based PAO/PPy aerogel. This aerogel enables rapid diffusion of uranium and accelerated adsorption in the presence of heat generated by sun irradiation, achieving a high adsorption capacity of 69.66 mg g−1 under 1 kW m−2 in 50 mg L−1 solution. The dynamical and thermodynamic simulations indicate the presence of both chemisorption and physisorption throughout the adsorption process. Additionally, the composite aerogel is demonstrated antifouling performance and excellent selectivity of U(VI) in a mixed ionic solution. The present study offers a novel approach for the rational design of aerogel adsorbents that can effectively extract uranium from seawater in outdoor environments, without the need for additional energy input.

Thermally Reduced Graphene Oxide Membranes Revealed Selective Adsorption of Gold Ions from Mixed Ionic Solutions.

The recovery of gold from water is an important research area. Recent reports have highlighted the ultrahigh capacity and selective extraction of gold from electronic waste using reduced graphene oxide (rGO). Here, we made a further attempt with the thermal rGO membranes and found that the thermal rGO membranes also had a similarly high adsorption efficiency (1.79 g gold per gram of rGO membranes at 1000 ppm). Furthermore, we paid special attention to the detailed selectivity between Au3+ and other ions by rGO membranes. The maximum adsorption capacity for Au3+ ions was about 16 times that of Cu2+ ions and 10 times that of Fe3+ ions in a mixture solution with equal proportions of Au3+/Cu2+ and Au3+/Fe3+. In a mixed-ion solution containing Au3+:Cu2+:Na+:Fe3+:Mg2+ of printed circuit board (PCB), the mass of Au3+:Cu2+:Na+:Fe3+:Mg2+ in rGO membranes is four orders of magnitude higher than the initial mass ratio. A theoretical analysis indicates that this selectivity may be attributed to the difference in the adsorption energy between the metal ions and the rGO membrane. The results are conducive to the usage of rGO membranes as adsorbents for Au capture from secondary metal resources in the industrial sector.

Production of imprinted polystyrene resins for copper ions removal from wastewater

Imprinted resins have attracted much attention for their high contaminant removal and reuse performance. Chloroacetylated polystyrene resins, polyethyleneimine, epichlorohydrin, and Cu(II) were used as support, functional monomer, cross-linker and template, respectively. The ion-imprinted resins (PS-PEI@SIP) and non-imprinted resins (PS-PEI@NIP) were prepared by the combination of amination reactions and surface ion-imprinting technique. The adsorption processes of Cu(II) with PS-PEI@SIP and PS-PEI@NIP followed pseudo-second-order kinetics. The langmuir isothermal adsorption model was consistent with the adsorption curve, indicating that Cu(II) were uniformly adsorbed on the PS-PEI@SIP surface. Thermodynamic experiments showed that the adsorption of Cu(II) by PS-PEI@SIP was a spontaneous process, and high temperature was favorable for adsorption. In addition, the selectivity of PS-PEI@SIP to Cu(II) was confirmed by multi-component competitive adsorption experiments. When Cu(II) mixed with Ni(II), Zn(II) and Cd(II), the selection coefficients of PS-PEI@SIP for Cu(II) were 31.98, 37.19 and 64.27. The results showed that PS-PEI@SIP had high adsorption capacity and good selectivity for Cu(II) ions in mixed ionic solution, and the adsorption capacity was 89.4 mg·g–1. The simulation wastewater dynamic adsorption experiment showed that the PS-PEI@SIP adsorption column could treat 52.8 BV Cu(II) concentration (C＜7.5 mg·g–1), when the influent Cu(II) concentration was 150 mg∙L−1. When 1 mol∙L−1 HCl solution was used for dynamic desorption of PS-PEI@SIP, the desorption rate was more than 92%, indicated that PS-PEI@SIP had good regeneration performance. These results provided basic information for the production of imprinted adsorbent resins.

Sensitive and simple multi-ion detection using organic nanocrystal enrichment in paper analytical devices

Microfluidic paper analytical devices (μPADs) are among the most promising platforms for heavy metal ion analysis. On the other hand, achieving simple and highly sensitive analysis of μPADs is challenging. In this study, we developed a simple enrichment method for sensitive multi-ion detection utilizing water-insoluble organic nanocrystals accumulated on μPAD. By combining the enrichment method with multivariate data analysis, three metal ion concentrations in the ion mixtures were simultaneously quantified with high sensitivity owing to the sensitive responses of the organic nanocrystals. In this work, we successfully quantified Zn2+, Cu2+, and Ni2+ at 20 ng L−1 in the mixed ion solution using only two dye indicators with a larger sensitivity improvement than those reported in previous studies. Interference studies revealed possibilities for a practical application in real sample analysis. This developed approach also can be used for other analytes.

Insight into the gallium selectivity mechanism of in-suit ion-imprinted material in multi-ion systems

In order to confirm the selectivity and mechanism of self-synthesized imprinted materials (Ga-IIP-PP) for Ga ions in mixed solutions, the adsorption experiments of bimetallic and polymetallic systems, material characterization (SEM-EDS, XPS) and Density Functional Theory (DFT) calculations were applied to examine and reveal the selective adsorption performance and mechanism of Ga-IP-PP for Ga ions. The results showed that Ga-IIP-PP exhibited excellent selectivity for Ga ions in both Ga/Al binary system and multi-ion systems, and the adsorption efficiency of Ga ions is more than 70 %. XPS analysis indicated that the phenolic hydroxyl groups in the imprinted cavity were the main adsorption sites, and the superior selectivity of the imprinted material for Ga ions derived from the stronger complexation of the imprinted sites to Ga(III), stronger electrostatic attraction of Ga-IIP-PP to Ga(III) and the high matching degree of the imprinted cavity to Ga(III). In addition, the binding energy (Ead), Molecular Electrostatic Potential (MEP), total electron density, Mulliken charge and Frontier Molecular Orbitals (FMOs) analysis of the Ga-IIP-PP + Ga(III)/Al(III) system pointed to more electron exchange, larger absolute value of binding energy, higher electron cloud overlap, and larger orbital energy gap (Egap) between Ga-IIP-PP and Ga ions, which confirmed a stronger adsorption affinity of Ga-IIP-PP for Ga ions than Al ions.

Heavy metal ions incorporated within strippable PVA-TTA polymeric matrix detected by colorimetry and vibrational spectroscopies

We report the synthesis and characterization of a novel strippable polymeric matrix of polyvinyl alcohol (PVA) aqueous solutions embedded with 2-thenoyl trifluoroacetone (TTA) organic ligand for decontamination of heavy metal ions. The TTA-containing polymeric matrix was applied to several contaminated surfaces comprising various concentrations of UO22+, Cu2+, Fe3+ and Cs+ contaminants. Except for Cs+, the contaminants were found to interact with the ligand contained in the polymeric matrix, accompanied by a consequent indicative strong color change, specific to the metal contaminant. The dried coating is easily exfoliated leaving the surface decontaminated. ATR-IR and Raman spectroscopies were also applied, showing a clear spectroscopic signature of each metal contaminant, in particular when contained in a mixed ion solution. All in all, the utilization of vibrational spectroscopies is shown to provide important complementary detection signatures that are otherwise vague when surfaces comprising trace amounts of contaminants, lacking color responsive behavior, are involved.

Nanoporous multilayer graphene oxide membrane for forward osmosis metal ion recovery from spent Li-ion batteries

The recovery of Li and rare metals from the spent electrodes of Li-ion batteries (LIBs) is becoming increasingly important. Herein, nanoporous multilayer graphene oxide (NMG) membranes were fabricated via the confined thermal annealing method to achieve Li-ion selectivity. A graphene oxide (GO) membrane was prepared by coating the membrane with an aqueous layer of GO liquid crystal via the scalable bar coating method, followed by hot-pressing. The influence of the GO interlayer spacing and nanopore presence on the ion separation performance was investigated. The NMG membrane shows different ion permeance phenomena depending on ion concentration. The permeation rate of divalent ions (Co, Ni, Mn) through the NMG membrane was faster than that of Li ions in solution with low ionic strength, whereas the membrane was Li-ion selective in mixed ionic solutions or at high ionic strength. This result indicates that electrostatic interaction by oxygen groups is important at low ionic strength, but size exclusion by interlayer spacing and adsorption by nanopore is critical at high ionic strength. The ion permeation mechanisms were further examined based on molecular calculations, which revealed that the binding energies between the divalent ions and nanopores or basal plane of graphene were high, resulting in slow ion permeation. When the NMG membrane was combined in a forward osmosis system, Li-ion can be separated continuously from the mixture solution simulated from the spent Li-battery electrode. This approach shows the high potential of nanoporous multilayer graphene membrane for Li extraction in particular with dense pore structure and around 7 Å of d-spacing.

Palladium Recovery from Aqueous Solution By Electrodialysis

In this work, we investigate the potential of Electrodialysis to increase the palladium concentration stage in Pd recycling to ensure a maximum recovery rate. We further explore and discuss optimization of Electrodialysis process design.PGMs are in high global demand, driven mainly by their use in autocatalysts. However, the European Commission classifies PGMs as Critical Raw Materials, and the primary production of PGMs is covered to a large extent by South Africa and Russia (ca. 85%). As a result, the PGM market is in continuous deficit. Furthermore, the recycling input rate of End-of-life products containing PGMs is estimated at 21% in Europe, which is largely insufficient to meet the EU demand. At the same time, recovery rates are low, and significant amounts of metals are lost in bi-products and residuals.Palladium containing End-of-life products are typically leached in aqua regia (hydrochloric and nitric acid) before elemental separation. The separation methods are chemical intensive and do not allow for a 100 % recovery rate. However, with Pd being a critical raw material, recovering even very dilute concentrations is relevant.We investigate the potential of Electrodialysis to increase the palladium concentration stage in industrial draw solution after the chemical separation of PGMs. The only consumable required by the process is electricity. We evaluate the viability of the process and investigate the most beneficial process conditions that ensure the highest recovery rate and energy efficiency.In Electrodialysis, anion and cations-exchange membranes are stacked alternatingly between two electrodes. When a current is drawn, the cations will move towards the cathode, passing the cation-exchange membrane and vice versa for the anions. Since the membranes are selective for either anions or cations, they strongly retard the passage of the opposite ion. Therefore, cations and anions are accumulated in every second compartment, while every other chamber is desalinated.In Electrodialysis, the current density is proportional to the sum of the ion fluxes and their charges. Due to boundary layer effects at the membrane surfaces causing depletion of ions, the resistance, and specific power consumption will increase with increasing current density. We investigate the optimal operating current for an industrial mixed-ion solution containing dilute concentrations of Pd (~1200 mg/L) by doing amperodynamic sweeps and recording current-voltage curves. We then test the desalination performance of the ED stack with two different commercially available anion-/cation-exchange membrane pairs. Membrane properties are a crucial factor for ED performance. To increase the concentration stage of a target ion (Pd), the ability of the membrane to exclude water from transporting through it is of paramount importance. Therefore, we compare two types of membranes with different hydrophobicity and discuss the influence of water transport on ion permselectivity. The ion permselectivity of the ED stack is evaluated based on irreversible thermodynamics, taking into account the transport numbers for ions and water. Mass transport of ions and water will depend both on membrane properties and process design.The flow rate and the applied current density are the dominant performance parameters concerning the process design. The flow velocity is limited by the pressure drop through the electrochemical cell, while the current density determines the energy efficiency to a large extent. Therefore, we vary those two parameters to investigate their effect on the system performance.Within three hours of Electrodialysis, we increased the Pd concentration in an industrial multi-component solution by more than 60 %. However, the decrease on the desalinated side was higher than the increase on the concentrated side, suggesting that some Pd is stuck in the membrane. We conclude that ED is a promising technology for Palladium recovery, justifying large room for future research and development of membranes and operational design.

PPy-Modified Prussian Blue Cathode Materials for Low-Cost and Cycling-Stable Aqueous Zinc-Based Hybrid Battery

Prussian blue analogs are promising cathode materials in aqueous ion batteries that have attracted increasing attention, but their low specific capacity and limited cycling stability remain to be further improved. Effective strategies to optimize the electrochemical performance of Prussian blue cathode materials are the aspects of electrolyte and structure modification. In this work, Na2MnFe(CN)6@PPy nanocubes were prepared by a simple co-precipitation method with PPy coating. Compared with the uncoated electrode material, the discharged capacity of the Na2MnFe(CN)6@PPy cathode material is raised from 25.2 to 55.0 mAh g−1 after 10 cycles in the Na-Zn hybrid electrolyte, while the capacity retention is improved from 63.5% to 86.5% after 150 cycles, indicating higher capacity and better stability. This work also investigates the electrochemical performances of Na2MnFe(CN)6@PPy cathode material in hybrid electrolyte of Li-Zn and K-Zn adjusted via different mixed ion solutions. The relevant results provide an innovative way to optimize advanced aqueous hybrid batteries from the perspective of cycling stability.

The effect of carbonization temperature on the capacity and mechanisms of Cd(II)-Pb(II) mix-ions adsorption by wood ear mushroom sticks derived biochar

Heavy metals often coexist in contaminated environmental media, and competition between heavy metals for adsorption sites influences the absorption capacity of biochar. In this study, the adsorption mechanism of pyrolytically modified wood ear mushroom sticks (250, 450, and 650 °C) as a new bio-adsorbent for single-ion and mixed-ion solutions Cd2+ and Pb2+ Biochar adsorption experiments showed that the adsorption abilities of Cd2+ and Pb2+ increased with increasing WMBC (wood ear mushroom sticks biochar) pyrolysis temperature. According to the Langmuir model, the maximum adsorption capacity of Cd2+ and Pb2+increased with higher pyrolysis temperature, being 29.84, 39.08, 46.16 mg·g−1and 124.3, 186.8, 234.2 mg·g−1, respectively for three different pyrolysis temperatures 250, 450, and 650 °C. WMBC exhibited a stronger adsorption ability for Pb2+ than for Cd2+. Competition between the two heavy metals severely inhibited the adsorption of Cd2+. Based on X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and Fourier transform infrared spectroscopy (FTIR) analyses, the dominant interaction mechanisms were determined to be complexation, ion exchange, precipitation, and C–π interaction. The results suggest WMBC shows promise as a novel, cheap, and effective adsorbent that can be used to remove both Cd2+ and Pb2+ pollutants from environmental media.

Ion-Selective Adsorption of Lead by a Two-Dimensional Terbium Oxalate Framework

Abstract Advances in hazardous metal ion removal are essential for wastewater clean-up to tackle the global water shortage crisis. Here, we report a Pb-selective adsorbent using a Tb oxalate framework (TOF) synthesized by a one-pot hydrothermal method. The TOF has a two-dimensional sheet structure, in which the interlayer space functions as an ion exchangeable site. Sorption tests using a mixed-ion solution containing Pb2+, Cd2+, Mn2+, Co2+, Ni2+, Cu2+, Na+, K+, Mg2+, and Ca2+ showed that the TOF has high selectivity for Pb2+ among other metal ions. The saturated adsorption capacity of the TOF for Pb2+ was 276 mg g−1, which is higher than that of conventional adsorbents. Furthermore, the TOF exhibited reversible Pb2+ adsorption/desorption and could be used for at least three cycles. The results showed that TOF has excellent potential as an adsorbent for removing Pb2+, and because of its reusability, it is also a promising material for wastewater clean-up.