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Modified three-compartment electrodialysis (MTED), a novel process containing intermediate compartment with fluorinated ion exchange membrane, has been applied to the recovery of petroleum sulfonate from petrochemical dispersion. The fluorinated ion exchange membrane has higher degree of crosslinking than heterogeneous ion exchange membrane. The petroleum sulfonate is separated from the petrochemical dispersion during anion migration by the different steric effect of ion exchange membranes. In order to reduce the membrane fouling and increase the current efficiency, the 50 nm ceramic membrane was utilized as the pretreatment of MTED. The result indicated that in total of 99.4 wt% of petroleum sulfonate in the petrochemical dispersion could be recovered at the applied voltage 25 V, flux rate 30 L/h, temperature 40 °C and initial concentration 7.5 wt% (NH 4 ) 2 SO 4 . Simultaneously, the (NH 4 ) 2 SO 4 solution without petroleum sulfonate was received in concentrate compartment of MTED. The results verified the feasibility of MTED on separating the petroleum sulfonate and inorganic salt in petrochemical dispersion, and provided important technical basis for a large-scale procedure of MTED in petrochemical dispersion treatment. [ABSTRACT FROM AUTHOR]

Reverse electro-dialysis (RED) is a potentially available technology to harvest salinity gradient power, which can be extracted from high-salinity wastewater in industrial processes. This study proposes a hybrid RED/ED system to simultaneous osmotic energy recovery and complete desalination in the phenol-containing wastewater treatment process. Experimental investigation on standalone ED system reveals that the high stack resistance, resulting from the salinity difference between both feed streams, accounts for the inefficient desalination performance in early stages, which implies potential implication of RED as a pre-desalination process with natural driving force to reduce the salinity difference. Pre-desalination rate is related to power generation in RED stage and energy saving in ED stage under optimal operation conditions. Compared with artificial seawater, greater power generation is produced by using phenol-containing wastewater as the high-salinity stream. Economic analysis suggests that average power generation and limiting wastewater treatment capacity can provide insightful guidelines for the design and improvement of the hybrid system. Control conditions are listed as a fundamental criterion to search for potentially applicable wastewater systems in the hybrid system. Therefore, hybrid RED/ED system can realize triplex advantages of salinity energy usage, high-valued resource reclamation, and low-energy desalination in high-salinity wastewater treatment processes. [ABSTRACT FROM AUTHOR]

Highlights: [•] The voltage drop follows the orders: U BP-A-C-BP > U BP-A-BP > U BP-C-BP. [•] Concentration follows the orders: C BP-C-BP > C BP-A-C-BP > C BP-A-BP. [•] Current efficiency follows the orders: ŋ BP-A-C-BP > ŋ BP-C-BP > ŋ BP-A-BP. [•] Energy consumption follows the orders: E BP-A-BP > E BP-A-C-BP > E BP-C-BP. [•] It is wise to choose BP-A-C-BP configuration for preparation the succinic acid. [Copyright &y& Elsevier]

Highlights: [•] Regenerating spent acid produced by HZSM-5 zeolite preparation is proved feasible by BMED. [•] The pure sodium hydroxide in the base chamber can be recycled. [•] The recycled acid solution can replace the pure acid solution completely. [Copyright &y& Elsevier]

Abstract: Because of the demand for acid solutions in seawater desalination pretreatment and the difficulty of transporting sulfuric acid or hydrochloric acid, seawater concentrate from an RO system was used as the feed for the production of mixed acid by bipolar membrane electrodialysis (BMED) after the removal of calcium ions and magnesium ions. In this experiment, the feasibility of the process was tested using a laboratory ED-cell with an effective area of 88cm2. Based on the configuration of the BP-C-A-BP, the mixed acid solution was produced in the acid compartment, and the base solution was produced in the base compartment. The results showed that 1mol/L mixed acid and sodium hydroxide could be produced continuously at a constant current density of 57mA/cm2 and a flow rate of 0.30L/h in the continuous-mode BMED. After the production of the acid and base solution, membrane fouling was inspected by measuring the stack resistance and using electron microscopy and surface elemental analysis. No visible fouling deposits on the surface of the CEMs (AEMs) were observed, and there was an increased stack resistance, thus proving that the BMED process for mixed acid production with pretreated RO concentrate is suitable for a long-term run. [Copyright &y& Elsevier]

[Display omitted] • Monovalent cation permselective membranes were prepared by the combination of surface-crosslink and inorganic nanomaterial doping. • Two-dimensional MOFs were introduced into the monovalent cation permselective membranes for the first time. • 2D MOF, Zn-TCPP, effectively enhanced the ion transport. • Tremendous permselectivity and permeability were obtained simultaneously. Monovalent cation permselective membranes (MCPMs) manifest remarkable effectiveness and potential in lithium extraction whereas facing the challenge to achieve high permselectivity and high Li+ permeability simultaneously. In this work, Zn-TCPP, a kind of two-dimensional nanosheet with abundant negative charges, was successfully synthesized via surfactant-assisted method and introduced into surface cross-linked SPES membrane to fabricate MCPMs. The physicochemical properties, electrochemical properties and Li+/Mg2+ separation performance of resulted MCPMs were systematically estimated. As ions passing through the membrane, dense PVA/GA crosslinked layer separated Li+ and Mg2+ by pore-size sieving effect. Afterwards, uniformly distributed Zn-TCPP nanosheets with rich negative charges and physically adsorbed water molecules elevated the charge density and water content in the membrane and thus expedited Li+ transporting. Therefore, high Li+/Mg2+ permselectivity (P Mg 2 + Li + = 8.99) and Li+ permeation flux (J Li + = 9.12 × 10−9 mol cm−2∙s−1) were obtained. Furthermore, membrane surface resistance was reduced from 108.99 Ω cm2 to 24.12 Ω∙cm2. This study points out the feasibility of the new method for accelerating monovalent ion transport and alleviating the restriction between ion permeation and permselectivity in selective ion exchange membranes. [ABSTRACT FROM AUTHOR]

In this paper, a novel approach of five-compartment electrodialysis was proposed for the treatment of cyanide from gold mine effluent. Two different processing modes were introduced. In mode 1, the cyanide was removed with homogeneous ion exchange membranes and heterogeneous ion exchange membranes respectively. In mode 2, the recovery of cyanide was achieved with homogeneous monovalent anion exchange membranes (1-AEMs) and cation exchange membranes (CEMs). The applied voltage was optimized to improve the removal and recovery efficiency. In addition, pH variation (the recovery of alkaline solution) was investigated. The results showed that the CN − extraction percent of 87.14% was achieved at 30 V applied voltage with the energy consumption of 8.33 kWhm −3 in mode 2. Meanwhile, the removal rate reached up to 97.90% with homogeneous ion exchange membranes at 38 V applied voltage in mode 1, which was much higher than the case of heterogeneous ion exchange membranes (74.02%). Finally, the recovery of alkaline solution was achieved as above and the recovered alkaline solution could be reused for pH adjustment in ED process. This research provides a new insight into the resource recycling of cyanide from gold mine effluent in industrial application. [ABSTRACT FROM AUTHOR]

Abstract: The feasibility that quaternized chitosan was used as cationic layer for surface modification of two kinds of commercial cation exchange membrane (CEM, one is heterogeneous and the other is homogeneous) to enhance their selectivity was reported in this paper. The membranes before and after modification were characterized by observation of surface morphology and determination of selective separation properties in detail, respectively. Scanning electron microscopy (SEM) displayed the difference of surface morphology induced by modification. The selectivity of membranes toward protons vs. metallic cations was investigated through electrodialysis experiments in binary systems (H+/Zn2+ and H+/Al3+) and tertiary systems (H+/Zn2+/Al3+). The results indicated that the transport of the metallic cations was decreased significantly after surface modification due to the electrostatic and steric barrier created by the thin cationic quaternized chitosan layer. In addition, the contrastive experiments such as the orientation of the modified layer (facing cathode or anode) were also carried out and analyzed tentatively. [Copyright &y& Elsevier]

The spacer geometries have a crucial effect on the hydrodynamics of spacer-filled channels in electrodialysis (ED) process, which are beneficial to mass transfer enhancement. Herein, a three-dimensional, isothermal, and steady flow model was developed by computational fluid dynamics (CFD) to illuminate the impacts of the spacer geometrical configurations on hydrodynamic behaviors in the spacer-filled channel for ED applications. Simultaneously, the finite element analysis method was employed to investigate the effects of spacer geometries on the velocity and pressure profiles. Furthermore, the normalized expenditure (NEXP) was introduced to acquire one comparable cost estimation index, which determined the optimal spacer geometries subserving the efficiency and economic competitiveness of ED process. Theoretical and techno-economic analysis validated that the optimal mesh parameters within the range of the test parameters were a cylindrical mesh, a filament diameter of 0.8 mm, a filament interval of 1.0 mm, a flow attack angle of 30°. Therefore, this work can provide a feasible strategy to visualize and quantitate the hydrodynamics in the spacer-filled channel and insight into the optimization of ED stack, potentially reducing the expenditure related to materials usage, energy consumption and test time. [ABSTRACT FROM AUTHOR]