Purification Effect of Coagulation-sedimentation for NaSCN Concentrated Solution from Two-step Wet Production of Spun Acrylic Fiber

To further purify and recycle the concentrated solution of NaSCN excreted from the nanofiltration membrane in the two-step wet production of acrylic fiber, the coagulation-sedimentation method was applied to the treatment of concentrated solution of NaSCN membrane separation. Different dosages of polyaluminium chloride (PAC), polyacrylamide (PAM), lime milk, etc., and variable initial pH, stirring intensity were tested to analyze the purification effect of concentrated solution of NaSCN membrane separation. The results showed: when the dosage of PAC, PAM, lime milk was 200, 2.5, 25 mg/L separately, initial pH was 7.5, stirring intensity was 80 r/min, velocity gradient (G) was 48.9 s^-1, GT was 58.7×10³, the turbidity and COD_Cr removal rates of the concentrated solution were 85%±2%, 30%±5%, respectively; the SCN^-turnover rate was only 20% under the above conditions, and the recovery rate of SCN^-was more than 75%. It showed that the method was suitable to the pretreatment of the concentrated solution.