A IMPROVED PROCESS FOR PRODUCING LOW-CY ANIDE CONTENT DRINKABLE WATER FORM HIGM-CYANIDE CONTAINING WASTE WATER DISCHARGED FROM COKE OVEN PLANTS

摘要

2,0; (iv) the mix is calcined at a temperature upto 950°C, preferably at 700-800°C, for 3 to 5 hours; (v) the calcined mix containing sodium chromate formed by reaction between the fines and alkali is cooled in natural air for 15 to 20 hours; (vi) the cooled mix is leached out with hot water at 50-80°C; characterised in that (a) the leached out dilute solution of sodium chromate in water is. concentrated by heating at 50-80°C to increase the concentration of sodium chromate in the solution to 8-10 mg/1; (b) 1 part by volume of concentrated solution of sodium chromate in water and 1 part by volume of sulphuric acid of strength 97-99% are added separately to 500 parts by volume of waste water containing 1 mg/1 cyanide, discharged from coke oven plants; and (c) the mixture is agitated thoroughly for 1 to 3 hours till the cyanide content of the waste water reduces to 0.2 mg/1.