DEGRADATION OF RHODAMINE B IN AQUEOUS SOLUTION BY FENTON-LIKE OXIDATION

摘要

The degradation of Rhodamine B - a basic dye - present in aqueous solution in the concentration range of 2.09 × 10~(-6) - 2.09 × 10~(-5) mol dm~3 has successfully been accomplished by Fenton-generated hydroxyl radicals. The present work is aimed at studying the degradation kinetics and the effects of various parameters such as initial dye concentration, concentration of ferrous sulfate as well as hydrogen peroxide on the extent of the oxidation of the dye. The degradation was found to occur in two steps: initial rapid reaction period followed by a slow rate of oxidation. Too high a concentration of H_2O_2 was found to be detrimental as it retarded drastically the rate of degradation; hence, identification of the optimum H_2O_2 and FeSO_4 concentration is extremely important for the successful implementation. The results indicate that an aqueous dye solution of 2.09 × 10~(-5) mol dm~(-3) can be most effectively degraded at a dye: Fe~(2+): H_2O_2 molar ratio of about 1:3.44:42.2 at a pH of around 2.6 and at a temperature of 299 K. The rate equation for the dye degradation is given by: -d [dye]/dt = k [dye]~(1.05)[Fe~(2+)]~(0.44)[H_2O_2]~(0.38) where, k = 17(dm~3)mol~(-1))~(0.824)s~(-1) at 299 K Dissolved electrolytes like salts of chloride and bromide retarded the degradation rate markedly, whereas SO_4~(2-) or ClO_4~- were found to be benign. About 99% removal of color was achieved in 3 hours at a pH of 2.6 ±0.1 and at 299 K, that corresponds to about 86% reduction of the initial COD. The results might find application for designing treatment systems for wastewater containing Rhodamine B.