REMOVAL OF COLOR FROM REACTIVE YELLOW X-R WASTEWATER BY MAGNESIUM HYDROXIDE COAGULATION PROCESS

This article studied removal of color from reactive yellow X-R wastewater by magnesium hydroxide coagulation process，and discussed the influences of pH values，coagulant dosages and different mixing conditions on color removal efficiency． The floc formation of dye wastewater was monitored by the intelligent Particle Dispersion Analyzer ( iPDA) ，and further the effects of different stirring conditions on growth characteristics of floc and coagulation process were also discussed． The experiment results showed that the maximum removal of chrominance ratio appeared when pH of the solution was enhanced to 12. 0． The optimum magnesium ion dose was 216，144 mg /L for pH level reached to 11. 5 and 12. 0，respectively． The coagulation performance was better when rapid stirring speed at 200 r /min for 40 s，and low stirring speed at 40 r /min for 10 min． Stirring condition was essential for coagulation process． Increasing the stirring speed and time would have a negative impact on the floc formation and growth． Based on the changes of zeta potential，charge neutralization and adsorption were proposed to be the main coagulation mechanisms．