Pollution prevention for manufacturing of ammonium chloride : an experimental study of wastewater recycling

An experimental study was performed to assess the feasibility of recovering valuable chemicals from waste streams. The ammonia in the wastewater generated from the NH sub(4)Cl manufacturing could be recovered using an ion-exchange technique. After the ammonia-rich wastewater passed through cation exchange resin, regeneration with HCl was performed. The resultant regenerant solution was composed of NH sub(4)Cl. This spent solution could be recycled into the upstream, i.e., drying process for the NH sub(4)Cl production. However, NH sub(4)Cl concentration in the regenerant solution was so little for drying that the direct recycling of the regenerant solution could not be valid. Therefore, pre-concentration of the regenerant was strongly proposed to increase the NH sub(4)Cl concentration. Typical concentration methods such as reverse osmosis, evaporation and electrodialysis were attempted to select an appropriate method for the pre-concentration. It was found that the electrodialysis was the most effective method to concentrate the regenerant NH sub(4)Cl solution. Since the ammonia concentration in the effluent of ion exchange was negligible, the effluent was able to be reused as process water or discharged directly. This new process makes it possible to recover the valuable material from the wastewater and to improve the effluent water quality. Consequently, it provides an environmentally sound alternative for manufacturing NH sub(4)Cl.