Selective Decolorization of Methylene Blue from Methyl Orange in Heterogeneous Fenton-like Reaction

Selective decolorization of mixed dyestuffs was realized by heterogeneous catalyst. A series of Cu/Fe@biochar composites containing different amounts of copper and iron were fabricated and all exhibited excellent catalytic performance in the degradation of methyl orange and methylene blue. The composite containing the highest metal component with 294.44 mg/g iron and 16.22 mg/g copper could decolorize 97.35% methyl orange in 60 min and 100% methylene blue in 10 min when the composite loading amount was 100 mg/L with 64 mM H2O2 in a 500 mg/L dyestuff solution at pH 3.0. In a solution containing methyl orange and methylene blue both in 200 mg/L and 100 mg/L the composite could decolorize almost 100% methylene blue in 10 min with 48 mM H2O2 while 74.9% methyl orange was left. Investigation revealed that methyl orange was mainly degraded on the catalyst surface and methylene blue in the solution. The selectivity was related to competitive adsorption and phase where dyestuff was degraded and depended on the performance of catalyst. Factors influencing degradation would also impact selectivity. This finding might be viable in application to reuse dyeing wastewater.