Performance assessment of alum as coagulant for degradation of disperse dyes from aqueous medium

摘要

ABSTRACT Textile wastewater effluents carry synthetic dyes resulting in potential hazards to the environment; hence such dyes need to be removed from the water bodies. In present research work, disperse dyes were degraded through coagulation using alum (Al2(SO4)3.18H2O) as a coagulant. Four dyes namely coralene navy blue EMRD, coralene red 6B, coralene orange 3R and coralene scarlet RR were used in the present research work and their removal from the wastewater was determined. The effects of initial pH, coagulant dose, initial dye concentration, temperature and time of reaction were tested to maximise decolourisation yield. Results of the experiments showed that the optimum pH for coagulation was 9 for each dye with up to 99% colour removal. By increasing the dose of alum Al2(SO4)3.18H2O, dye decolourisation was increased and maximum dye removal was observed when 1000 ppm of Al2(SO4)3.18H2O was used. When 100 ppm synthetic dye solution was prepared, up to 99% colour removal was achieved at optimal conditions i.e pH?=?9, 1000 ppm of coagulant at 100°C with 50?min reaction time. Coralene navy blue EMRD presented nearly 70% colour removal with lowest dose of alum (200ppm) at 40°C. About 80% dye degradation was observed for coralene orange 3R within 10?min of reaction time. Thus Al2(SO4)3.18H2O was found to be efficient coagulant for the treatment of wastewater containing disperse dyes with about 50% reduction in conductivity and upto 75% removal in TDS of wastewater. Sludge volume settled after 1 hour of reaction time was 140 mL/500 mL. On the basis of obtained results, it was concluded that the wastewater can be treated using Al2(SO4)3.18H2O as coagulant.