Effect of process conditions on generation of hydrochloric acid and lithium hydroxide from simulated lithium chloride solution using bipolar membrane electrodialysis

A feasibility study was carried out on generation of hydrochloric acid and lithium hydroxide from the simulated lithium chloride solution using EX3B model bipolar membrane electrodialysis (BMED). The influence of a series of process parameters, such as feed concentration, initial acid and base concentration in device component, feed solution volume, and current density were investigated. In addition, the maximum achievable concentrations of HCl and LiOH, the average current efficiency, and specific energy consumption were also studied and compared in this paper to the existing literature. Higher LiCl concentrations in the feed solution were found to be beneficial in increasing the final concentrations of HCl and LiOH, as well as improving current efficiency while decreasing specific energy consumption. However, when its concentration was less than 4 g/L, the membrane stack voltage curve of BMED increased rapidly, attributed to the higher solution resistance. Also low initial concentration of acid and base employed in device component can improve the current efficiency. Increasing of the initial concentration of acid and base solution lowered energy consumption. Moreover, a high current density could rapidly increase HCl and LiOH concentration and enhance water movements of BMED process, but reduced the current efficiency. The maximum achievable concentration of HCl and LiOH generated from 130 g/L LiCl solution were close to 3.24 mol/L and 3.57 mol/L, respectively. In summary, the present study confirmed the feasible application for the generation of HCl and LiOH from simulated lithium chloride solution with BMED.

Recovery of Biologically Treated Textile Wastewater by Ozonation and Subsequent Bipolar Membrane Electrodialysis Process

The Bipolar Membrane Electrodialysis process (BPMED) can produce valuable chemicals such as acid (HCl, H2SO4, etc.) and base (NaOH) from saline and brackish waters under the influence of an electrical field. In this study, BPMED was used to recover wastewater and salt in biologically treated textile wastewater (BTTWW). BPMED process, with and without pre-treatment (softening and ozonation), was evaluated under different operational conditions. Water quality parameters (color, remaining total organic carbon, hardness, etc.) in the acid, base and filtrated effluents of the BPMED process were evaluated for acid, base, and wastewater reuse purposes. Ozone oxidation decreased 90% of color and 37% of chemical oxygen demand (COD) in BTTWW. As a result, dye fouling on the anion exchange membrane of the BPMED process was reduced. Subsequently, over 90% desalination efficiency was achieved in a shorter period. Generated acid, base, and effluent wastewater of the BPMED process were found to be reusable in wet textile processes. Results indicated that pre-ozonation and subsequent BPMED membrane systems might be a promising solution in converging to a zero discharge approach in the textile industry.