Treatment of carbocysteine wastewater by bipolar membrane electrodialysis: From lab-to pilot-scale

Abstract

Carbocysteine (H2ccys) wastewater, which contains H2ccys, chloroacetic acid, and ammonium chloride, can pose significant risks to the environment. In this study, a novel strategy was proposed for treating H2ccys wastewater by bipolar membrane electrodialysis (BMED) to realize resource recovery. The migration and coexistence mechanism of organic/inorganic ions in wastewater were investigated in lab-scale experiments. The results indicated that the desirable migration of inorganic ions, such as NH4+ and Cl− ions, in the feed compartment were dominant. The undesirable migration of organic molecules, such as ClCH2COOH and H2ccys, could be managed through precise control of the BMED reaction process. To optimize the energy efficiency and thermal effect occurred in the pilot-scale, a two-stage BMED process was designed for treating H2ccys wastewater. The results revealed that BMED produced 1.33–1.63 M of HCl and 2.62–2.88 M of NH3·H2O, and removed 90 wt% of NH4Cl from H2ccys wastewater. Meanwhile, the thermal effect of the slot at the outermost acid compartment decreased from 3.32 W in the one-stage BMED process to 0.10 W in the two-stage BMED process during the pilot-scale tests. The current efficiency of the two-stage BMED process for the acid/base production and feed desalination in the pilot-scale tests increased and its energy consumption decreased compared with the lab-scale tests. Moreover, the BMED rrecycling route showed that a closed loop can be realized in the treatment of H2ccys wastewater, and its economic assessment showed that applying BMED to the treatment of H2ccys wastewater have economic benefits. These findings illustrated the feasibility of this novel strategy for treating H2ccys wastewater and laid a solid foundation for its industrialization.