Preparation of Hypophosphorous Acid by Bipolar Membrane Electrodialysis: Process Optimization and Phosphorous Acid Minimization

Abstract

Hypophosphorous acid (H3PO2) is an important chemical product with wide applications in pharmaceuticals and electroless plating. In this study, bipolar membrane electrodialysis (BMED) was used to produce H3PO2 from sodium hypophosphite salt (NaH2PO2) to replace the traditional preparation methods. The BMED process was optimized in terms of current density, NaH2PO2 salt concentration, and initial NaOH concentration of the base solution. The results indicated that low Na+ leakage occurred at lower salt concentrations. Under the optimum conditions, such a BMED system obtained a high concentration of H3PO2, a low Na+ content, and a low energy consumption, equaling to 1.03 mol/L, 670 ppm, and 1.18 kW h/kg, respectively. To minimize the amount of phosphorous acid (H3PO3) generated from H3PO2 oxidation during the BMED process, a nitrogen aeration operation was applied in both the acid and salt chambers, decreasing the HPO3 2– content to 251 ppm, which was 44.1% lower than that without a dissolved oxygen content control strategy. The newly produced H3PO3 during the BMED process was reduced by 96.5%. The obtained results indicated that the BMED process has great potential for application in the production of high-quality H3PO2 from NaH2PO2 in industry.

A Sustainable Electrochemical Method for the Production of Vanadium Pentoxide Using Bipolar Membrane Electrodialysis

“…This phenomenon was abnormal compared with the various BMED studies in the literature. 30,31,33,35,36 Generally, the concentration of acid produced by BMED increased with an increase in current density because the water splitting rate was accelerated at high current density. 30,31,33,35,36 However, in our case, the discrepancy phenomenon is attributed to the competition transport between V 2 O 7 4− and OH − as well as the dissociation balance limitation of the polyvanadate.…”

“…30,31,33,35,36 Generally, the concentration of acid produced by BMED increased with an increase in current density because the water splitting rate was accelerated at high current density. 30,31,33,35,36 However, in our case, the discrepancy phenomenon is attributed to the competition transport between V 2 O 7 4− and OH − as well as the dissociation balance limitation of the polyvanadate. At a low current density of 10−20 mA/cm 2 , there was little amount of water splitting OH − in the salt compartment due to a weak electric driving force.…”

“…Bipolar membrane electrodialysis (BMED), an environmentally friendly technique that enables the conversion of salts into the corresponding acids and bases, creates possibilities for the avoidance of the vanadium ammonium precipitation procedure. By taking advantage of intensive water splitting in the bipolar membrane under a reverse bias, the BMED technique has gained great commercial interest and is widely used for a variety of applications such as acid/base production, − cleaner production, − environmental protection, − and CO 2 reduction, ,− among others. − However, to the best of our knowledge, there are no studies that investigate the preparation of vanadium oxide using the BMED technology. Compared with common inorganic salts, vanadium is a group VB element.…”

Recent Advances in Bipolar Membrane Design and Applications

“…Ammonia and phosphate have been recovered from biological waste using BPMED, − producing phosphoric acid and ammonium hydroxide with high recovery rates (>80%). Hypophosphorous acid, useful for electroless nickel plating, can be extracted from waste plating solutions with high efficiency and economically feasible process costs. , The regeneration of flue-gas desulfurizing agents (alkanolamines) can be conducted using BPMED at process costs competitive with the market value of alkanolamines. − Toxic metal wastes such as chromium and cadmium can be extracted from wastewater and soil, − while textile dyes can be removed from solution via the in situ generation of a dye absorbent, Ni­(OH) x , at the BPM interface, with minimal membrane scaling . Overall, the use of BPMED for waste valorization or removal is versatile, where the number of applications will increase as interest in developing “green”, sustainable chemical processes grows.…”

“…Hypophosphorous acid, useful for electroless nickel plating, can be extracted from waste plating solutions with high efficiency and economically feasible process costs. 200,201 The regeneration of flue-gas desulfurizing agents (alkanolamines) can be conducted using BPMED at process costs competitive with the market value of alkanolamines. 202−205 Toxic metal wastes such as chromium and cadmium can be extracted from wastewater and soil, 206−208 while textile dyes can be removed from solution via the in situ generation of a dye absorbent, Ni(OH) x , at the BPM interface, with minimal membrane scaling.…”