Kinetic characteristics of evaporative crystallization desalination of acidic high-salt wastewater

CLT acid (2-amino-4-methyl-5-chlorobenzenesulfonic acid) is a red organic pigment intermediate, which is widely used in textile printing and dyeing industry, but a large amount of acidic MgSO 4 high-salt wastewater will be generated during the production process. Direct discharge not only wastes sulfates in wastewater, but also damages the environment. In this paper, a new treatment process is developed to separate and recover MgSO 4 from high-salt wastewater by thermal evaporation crystallization method, which realizes the resource utilization and ensures the treatment effect. Through the evaporative crystallization kinetic experiment and the pilot experiment of acidic MgSO 4 high-salt wastewater, the influence of operating conditions on the product crystal size and crystal size distribution was investigated. The results show that the crystal growth is completed when the residence time is 40 min, the stirring speed is 200 r/min, and the seed content is 3 g/L. In industrial production, crystallization and recrystallization should be carried out after removing organic matters. When the concentration ratio is 1.6, the purity of MgSO 4 crystal reach 96 %, and the resources can be maximized. • The crystallization kinetics of MgSO 4 in CTL acid high-salt wastewater was studied. • The optimum operating conditions for the crystallization process of MgSO 4 were determined. • The precipitation amount and purity of MgSO 4 can reach 99 % and 96 % respectively.