Removal of dyes from synthetic wastewater by plasmachemical coagulation

Abstract

The Plasmachemical Coagulation (“Plasmacoagulation”) process is designed for the first time in this study to resolve 3 main problems associated with chemical coagulation processes which are effectiveness of the pollutants removal, excessive coagulant use and sludge disposal1. The complete removal of dyes through this process was investigated. For this purpose, amaranth red was used as target pollutant and 100 mg.L−1 of this azoic dye was treated by coagulation with 3 coagulants (aluminum sulfate, aluminum chloride and commercial Nalco®) and the best conditions (pH and coagulant dosage) were determined by jar-test procedure at ambient temperature. The same solution was also treated by plasma using gliding electric discharge2 for various treatment times (i.e. 0, 5, 10, 15, 20 and 30 min) and post-discharge treatment times (0, 5, 10, 15, 20, 35, 50, 65, 80 and 95 min). Individual treatments achieved maximum dye reduction of 94.38% (aluminum sulfate), 98.23% (aluminum chloride) and 97.4% (Nalco®); but large volumes of sludge were formed (8%, 23% and 15% for each coagulant respectively) and plasma exposure removed only 41.5% and 95 min. post-discharge treatment did not improved this removal to more than 5%. Plasmacoagulation optimized the process to complete bleaching of dye effluents (99% of dye removal) with 5 min. plasma treatment, reasonable consumption of coagulants and quantity of obtained sludge (1%).