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• P(DMC-co-AM) HPs was prepared by a green and fast method called PDICP. • AM enhanced mechanical strength of hydrogel particles effectively. • DMC promoted the removal of anionic dyes such as OG. Based on the strategy of copolymerization, methacrylatoethyl trimethyl ammonium chloride (DMC) and acrylamide (AM) copolymer hydrogel particles (PCM HPs) were prepared by precipitated droplets in-situ cross-linking polymerization, to overcome the easily fragile property of pure PDMC HPs and the low adsorption capacity of pure PAM HPs. Corn oil and deionized water were used for the reaction, which would not cause any pollutions; and the preparation process only took 40 s. Through the studies on various feeding ratios of DMC to AM, the hydrogel particles (PCM 5-1 HPs) with the mass ratio of 5:1, showed the best mechanical strength and adsorption capacity. The compression strength of the PCM 5-1 HPs was 207.7 K Pa, and no obvious mechanical loss occurred during five compression-rebound cycles. In addition, the removal ratios of anionic dyes such as amaranth red, orange G, and methyl orange were all higher than 94% (the initial dye concentration was 100 μmol/L and the adsorbent mass was 4 mg); and the adsorption capacity of orange G could reach as high as 992.63 mg/g. Meanwhile, the PCM 5-1 HPs exhibited excellent selective adsorption of anionic dyes in mixed dye solutions. Therefore, the hydrogel particles prepared by the fast and environmental-friendly method had both mechanical strength and ultrahigh adsorption capacity, which verified their practicality in the removal of anionic dyes in sewage. [ABSTRACT FROM AUTHOR]

Capacitive deionization (CDI) is an electrochemical method of removing salt ions from brackish water. A common assumption in CDI is that monovalent ions (e.g., Na+, Cl−) are removed in a 1:1 symmetry on the electrodes. Validation of this assumption with techniques such as ion chromatography is not commonly performed, but is important to better understand how parasitic process, such as faradaic reactions, affect ion removals. In this study, we quantified the removals of Na+ and Cl− as a function of electrode orientation in flow-through CDI. When the cathode was positioned upstream, Na+ and Cl− removals approached a 1:1 symmetry, but when the anode was located upstream, we observed a significant drop in Na+, but not Cl−, removals. We attributed this drop to oxygen reduction reactions at the cathode that competed with Na+ adsorption. Oxidation of carbon in the upstream anode yielded H+ that enhanced the reduction of oxygen to H 2 O 2 at the downstream cathode, which in turn diverted electrons from Na+ adsorption. In the absence of oxygen, Na+ removals increased in the upstream anode orientation and were comparable to Cl− removals, confirming that competition with oxygen reduction reactions was the primary reason for decreased Na+ removal. In the upstream cathode orientation, we show that H 2 O 2 generated at the cathode can be oxidized at the downstream anode, possibly enhancing Na+ removals via internal electron recycling. Salt adsorption capacities calculated using actual ion removals did not always agree with those estimated using changes in solution conductivity, with the largest disagreement observed when conductivity data were corrected for pH changes. Our results highlight that faradaic reactions, particularly oxygen reduction reactions, can contribute to asymmetrical removals of monovalent ions in flow-through CDI. Image 1 • Removal of Na+ and Cl− in flow-through capacitive deionization was studied as a function of electrode orientation. • Positioning the anode upstream led to a signficant decrease in Na+, but not Cl−, removal. • Oxygen reduction reactions at the cathode caused the drop in Na+ removals. • Salt adsorption capacities adjusted for actual ion removals did not always agree with estimates based on changes in solution conductivity. [ABSTRACT FROM AUTHOR]

Capacitive deionization (CDI) is an emerging technology for energy-efficient water desalination, and attracts more and more attention in recent years. It has been concluded that CDI technology shows competitiveness and perspectives on seawater desalination and wastewater treatment. The ionic adsorption mechanism can be clarified by electric double-layer capacitive adsorption and pseudocapacitive adsorption. The performance of CDI depends on both device and materials. The adsorption capacity and energy efficiency was improved significantly with fast growth of researches on material and novel energy storage techniques. This review summarizes researches on CDI technologies with an emphasis on electrode material design and improved adsorption performance. This review outlines the ion storage mechanisms and electrode materials of capacitive deionization. Unlabelled Image • Electrochemical extraction of ions from seawater/brine was reviewed systematically. • An emphasis on electrode material design thought has been analyzed. • The performance of various extraction devices has been summarized and compared. • Future challenge on this technology has been clarified. [ABSTRACT FROM AUTHOR]

Different plants can be used to prepare nanoparticles. This is termed as green technology. It is one of the best ecofriendly and low-cost method for the preparation of nanoparticles which has no harmful effects. PbO nanoparticles were prepared by green method using leaf extract of Datura Sternum plants. The preparation of Lead oxide was confirmed by color change from colorless to yellowish brown. UV–Visible peak obtained at 250 nm and XRD study clarified the formation of PbO NPs. These PbO nanoparticles were then applied for the preparation of Nano Composite Polymer Membranes (nCPMs). PbO-PVC nCPMs were prepared based on polyvinyl chloride (PVC) polymer and PbO filler with the help of solution casting method, using cyclohexanone as a solvent. Different percentage (5–35%) of filler was used. The physiochemical parameters studied were viscosity, water uptake (WU), perpendicular swelling (DT) in deionized water, density, porosity (ε), morphology, ion adsorption capacity (IAC) and electrical conductivity (σ). The values of all these parameters except viscosity and conductivity were increased on increasing filler percentage. Viscosity of the nCPMs solution was decreased from 171 to 46.21. The conductivity of nCPMs was first increased upto 25% filler and then decreased. The deformation in PVC structure was increased on enhancing PbO amount. The values of Density, porosity, water uptake, DT and IAC were found in range 1.15–5.02, 0.50–0.87, 72.01–141.30, 0.012–0.11, and 3.13 × 107–8.60 × 107 respectively. Unlabelled Image • PbO nanoparticles were prepared by green method and was confirmed by color change from colorless to yellowish brown. The UV-Visible and XRD study clarified the formation of PbO NPs. • PbO-PVC nCPMs (Lead oxide-polyvinyl chloride nanocomposite polymer membrane were prepared using solution casting method and were investigated for physiochemical parameters. • The values of water uptake, perpendicular swelling, density, porosity, ion adsorption capacity, were increased except viscosity and conductivity on increasing filler percentages in the composites. • The deformation in PVC structure was increased on enhancing PbO amount. The values of Density, porosity, water uptake, DT and IAC were found in range 1.15 -5.02, 0.50- 0.87, 72.01-141.30, 0.012-0.11, and 3.13 x 107-8.60 x 107 respectively. [ABSTRACT FROM AUTHOR]

• Freundlich model can well describe the phosphate electroadsorption behavior. • CDI electroadsorption is an endothermic process according to thermodynamics. • pH was determined by water electrolysis and forms transformation of phosphate. • Surface charge can reflect the amount of ions adsorbed by GCS model. The advanced treatment for phosphate (P) has been focused on in the wastewater treatment field in recent years. Developing an innovative P removal technology with high efficiency, low cost, and low energy consumption has become an imperative requirement. Capacitive deionization (CDI) is an emerging environmentally friendly technology for removing charged ions from aqueous solutions. In this study, we investigated the performances of P removal by CDI with homemade activated carbon electrodes. Furthermore, kinetics, thermodynamics and the equilibrium Gouy-Chapman-Stern (GCS) double-layer model were studied to reveal the mechanism of P adsorption. It was observed that the adsorption capacity was positively correlated with the voltage. The pH first increased and then decreased during the adsorption because of water electrolysis and forms transformation of phosphate. The experimental results were validated by pseudo-first-order adsorption kinetics and Freundlich isotherms. The adsorption rate increased with increasing temperature, voltage, and concentration. The adsorption capacity decreased with increasing temperature, and the maximum adsorption capacity was 8.53 mg/g. Thermodynamic analysis confirmed that the electrosorption of P on the activated carbon electrode was an endothermic process, and the high temperature was conducive to reducing the adsorption potential of P on the activated carbon electrode. The theoretical results of the double layer model were in agreement with the experimental data, which showed that the ion adsorption can be reflected by surface charge. This study can help to understand the adsorption mechanism of P on activated carbon electrodes and provide a theoretical basis for the application of P removal by CDI. [ABSTRACT FROM AUTHOR]

Introduction of new nanomaterials with conductivity, salt adsorption capacity (SAC) and rate (SAR) exceeding that of carbon electrodes may greatly improve capacitive deionization of water. However, those materials show a different electrochemical behavior, which must be studied and optimized for practical use. Here, effects of operating conditions on desalination performance of pre-conditioned Ti 3 C 2 T x -MXene-based electrodes in a symmetric membrane capacitive deionization (MCDI) system were investigated. Specifically, influences of discharge potential, half-cycle length (HCL), and flow rate were systematically studied. Results showed different degrees of performance dependence on operating conditions. For instance, lower discharge potentials increased SAC and SAR by 152%. However, longer HCL increased SAC by 32% while decreasing SAR by 54%. Finally, faster flow rates decreased both SAC and SAR by 20%. Desalination performances of symmetric pre-conditioned MXene and activated carbon cloth (ACC) electrodes were gravimetrically and volumetrically compared in MCDI system. Pre-conditioned MXene electrodes gravimetrically performed 30% lower than ACC due to their notably higher density. Yet, pre-conditioned MXene electrodes volumetrically outperformed ACC by 162%. Results suggest that although MXenes offer high electrochemical activity and hydrophilicity, making them promising candidates for CDI applications, the strong dependence of desalination performance of MXenes on operating conditions requires in-depth understanding and warrants further research. Unlabelled Image • Pre-conditioned MXene outperforms ACC by 162% due to bulk volume ion storage. • Pre-conditioned MXene MCDI system has shown steady SAC for 100 cycles. • Lower discharge potentials enable more effective ion deintercalation. • Improved ion deintercalation leads to up to 152% increase in SAC and SAR. • Longer half-cycle length increases SAC by 32% and decreases SAR by 54%. [ABSTRACT FROM AUTHOR]

• Fe 3 O 4 @β-CD-CDI was synthesized by coordination interaction between Zn ions and β-CD-CDI ligands. • This composite had a satisfactory removal efficiency for BPA. • The polymer layer was introduced to enhance the structure stability. • The magnetic core facilitates easy separation and recycling. • The composites can as heterogeneous catalyst to removal BPA through Fenton-like reaction. Herein, we report a novel magnetic bifunctional β-cyclodextrin nanocomposite (Fe 3 O 4 @β-CD-CDI) based on metal coordination, which may be used for adsorption and degradation of persistent organic pollutants in aqueous solution. More importantly, N , N '-carbonyldiimidazole (CDI) functionalized β-CD ligand (β-CD-CDI) was assembled on the surface of Fe 3 O 4 by Zn-N interaction. The results of kinetic and isothermal adsorption model investigation indicated that the adsorption rate and capacity of Fe 3 O 4 @β-CD-CDI were better than other materials, suggesting the effective accessibility of adsorption sites. We further confirmed that Fe 3 O 4 @β-CD-CDI can be used as heterogeneous catalyst to remove BPA through Fenton-like reaction in the presence of hydrogen peroxide (H 2 O 2). Moreover, the material effectively alleviated the secondary pollution owing to the existence of β-CD inner cavity. This study indicated that the magnetic Fe 3 O 4 @β-CD-CDI material has great potential applications in wastewater purification containing persistent organic pollutants. [ABSTRACT FROM AUTHOR]

• A biocharcoal-based electrode was used to improve Cl− and Cr3+ removal. • The adsorption and regeneration performance of the KOBC15 were analyzed and evaluated. • Optimization of operation parameters for the CDI system was performed. Red oak biocharcoal, a novel electrode material that is inexpensive and highly conductive, was used for capacitive deionization (CDI) to simultaneously remove Cl− and Cr3+ from leather processing wastewater. The results showed that both the carbonization temperature and time played important roles in reducing the resistivity (ρ) of biocharcoal. Additionally, at 1000 °C and 3 h, the ρ value was reduced from 4.68 to 1.19 Ω·cm after the addition of Fe 2 O 3. KOH impregnation enhanced the desalination capacity of the biocharcoal electrodes by increasing the specific surface area and hydrophilicity. Under the optimal operating parameters (voltage of 1.8 V, flow rate of 10 ml/min and electrode spacing of 2 mm), the KOBC15 electrode exhibited a maximum adsorption capacity of 13.79 mg/g. After 10 cycles of CDI system operation, the removal rates of Cl− and Cr3+ reached 86.7% and 100%, respectively, in simulated leather processing wastewater. This work provides new ideas and methods for the treatment of high-salinity wastewater. [ABSTRACT FROM AUTHOR]

Manganese-zinc chloride waste liquor (MZCWL) produced during cobalt smelting is a significant source for the preparation of high-purity manganese sulfate. The key to recover manganese from MZCWL is the separation of Zn(II). Conventional methods for zinc removal are unsatisfactory due to similar physicochemical properties of zinc and manganese. In this study, a complexation ion-exchange approach was developed to selectively extract and separate zinc from MZCWL. Theoretical analysis suggested that zinc existed as non-cationic chloride complexes (ZnCl 2 0, ZnCl 3 −, and ZnCl 4 2−) under a high chloride concentration. They can be adsorbed by an anion-exchange resin, while manganese still existed in the form of divalent cation. Herein, D201 resin was used to selectively adsorb zinc from MZCWL. The adsorption was significantly affected by chloride concentration, contact time, resin dosage, and temperature. Moreover, the Langmuir isotherm model fitted the adsorption best with a maximum zinc adsorption capacity of 158.98 mg·g−1 at room temperature. In addition, SEM-EDS and Raman analysis further revealed that Zn(II) was adsorbed by D201 resin in the form of zinc chloride complexes. This work provides an alternative and feasible approach for the separation of zinc from chloride medium. Unlabelled Image • The species of Zn(II) under varying chloride concentrations were clarified. • Zn(II) adsorption by D201 resin was related to monolayer uniform adsorption and controlled by chemisorption. • The adsorption efficiency of Zn(II) by D201 resin reached 99.93% under the optimal condition. • Zn(II) was adsorbed on the D201 resin in the form of ZnCl 4 2−. • Zn(II) could be readily eluted from the loaded resin by deionized water. [ABSTRACT FROM AUTHOR]

• Graphene oxide was used for adsorption of diesel from oil-water emulsion. • A high capacity of 1335 mg/g was achieved. • Adsorption capacity increased under increasing salinity, tested up to 100 g/L NaCl. • Adsorption showed extremely rapid kinetics reaching 90% of capacity within 4 min. • Fixed-bed column tests demonstrate compact adsorption system with good regeneration. Large quantities of oily wastewaters are produced globally from oil extraction and refining industries containing low concentrations of dissolved and finely emulsified oils. These waters are difficult to treat within a small footprint as often necessary, especially on offshore sites, and often contain high salinity making many treatment methods ineffective. In this study the use of graphene oxide (GO) as an adsorbent is investigated using diesel as a representative oil. GO demonstrated a high adsorption capacity of 1335 mg/g according to the Freundlich isotherm and based on theoretical surface area was likely due to limited multi-layer adsorption. Increasing salinity to 1% increased adsorption capacity by 75%, remaining constant thereafter, confirming the suitability for the material for saline produced water remediation. Adsorption was extremely rapid, reaching more than 90% of the equilibrium capacity within 4 min, and was represented best by a pseudo-second order kinetic model. Fixed bed column tests confirmed the ability for excellent removal capacities under a short contact time and good regeneration, indicating the potential of GO for industrial oil-water emulsion separation applications. Based on careful analysis of isotherm and kinetic data, in conjunction with theoretical considerations, a rapid multi-layer physisorption mechanism, influenced by GO agglomeration, is proposed. [ABSTRACT FROM AUTHOR]