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

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 r^recycling 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.