Coagulation of Sulfur Dye with Inorganic Coagulants

Abstract

In order to obtain basic data for the treatment of waste water from sulfur dye-dyeing process, the coagulation of sulfur dye solution was investigated by using (1) A12(SO)s. n H20, (2) FeC13.6 H20 and (3) FeSO e7 H20-Ca(OH)2 as coagulants. Sulfur Black B (C.1. Sulfur Black 1) was used after purification by means of dialysis with cellophane membrane. Satisfactory coagu1ation of the dye was observed by dosage of 10N30 mg/1 of these coagulants as metal ion. The optimum pH ranges in the cases of coagulants (1) and (2) were 5N6, and that of coagulant (3) was 9xvlO. Among the inorganic salts probably contained in ordinary waste water, the coexistence of NaCl and Na2SO4 showed relatively small effects on the dye coagulation. The coexistence of Na2COs increased the amounts of the coagulant (1). required for coagulation and Na2S20s protected the dye from coagulation with the coagulant (2) in acid solution. The coagulation in alkaline solution with the coagulant (3) was not appreciable affected by the salts described above. In case of (3), the effect of anionic surfactant of less than 80 mg/l on the coagulation was negligible.