溶析-蒸发结晶法分离Na2SO4/NaCl混盐OA

With the rapid advancement of industrialization,the annual production of industrial waste salt in China has exceeded 2×107t.One of the key approaches to the resource utilization of industrial waste salt involves the separation,purification,and recovery of inorganic salts such as Na2SO4 and NaCl.An antisolvent-evaporation crystallization salt separation process was developed for the Na2SO4/NaCl mixed salt system.The antisolvent was screened,and the optimal process conditions were determined by exploring the effects of solid-liquid ratio,ratio of salt and mirabilite,antisolvent concentration,and number of antisolvent cycles on the Na2SO4/NaCl mixed salt separation products.Subsequently,this process was applied to the separation of actual industrial waste salts.The experimental results showed that NaOH was the most suitable antisolvent for Na2SO4/NaCl mixed salt separation among the three antisolvents of H2SO4,HCl and NaOH.The optimal operating conditions of this process were as follows:the concentration of antisolvent NaOH solution was 8mol/L,the solid-liquid ratio was 200g/L,the ratio of salt and mirabilite was 3∶7,and the number of antisolvent cycles was 5 times.This process was applied to the separation of Na2SO4/NaCl waste salt obtained from a chemical plant sewage after RO membrane treatment.The purity of Na2SO4 crystal obtained by separation was 94.63％,and the purity of NaCl crystal was 97.83％.In this application,the process yielded a profit of 1945-2465CNY per ton of treated Na2SO4/NaCl waste salt,demonstrating its technical and economic viability.