Removal of dyes from synthetic wastewater by plasmachemical coagulation

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%).