Application of a novel rGO-CuFeS2 composite catalyst conjugated to microwave irradiation for ultra-fast real textile wastewater treatment

Abstract

The disposal of wastewater containing large amounts of dyes is a public health and environmental problem, due to its toxicity into the aquatic biota, the reduction in sunlight penetration, which consequently interference in photosynthetic activity. In the present study a new composite, based on the heterojunction of reduced graphene oxide (rGO) and chalcopyrite (CuFeS2), was developed to treat a real textile wastewater (RW). The efficiency of the composite assisted by microwave irradiation was evaluated to catalyze the decolorization and degradation of RW containing a high concentration of the azo Direct Black 22 (DB22). A small amount (0.5 w/w%) of rGO on CuFeS2 was enough to uplift the efficiency of decolorization to 74 % of DB22 and 97 % TOC in the RW, only in the first min of treatment, and 97 % and 99 %, respectively, at 6 min. The improvement in catalytic activity can be attributed to the dipolar polarization effect, hot spots and the generation of hydroxyl radicals. Additionally, a synergistic effect between the composite and microwave irradiation, assisted by hydrogen peroxide, reduced the RW phytotoxicity, improving the radicle length of Lactuca sativa three times (from 0.87 cm to 2.65 cm with the application of a single minute of treatment). The reduction in phytotoxicity led to an increase in the germination percentage from 36 % to 53 %. Finally, the use of MW irradiation coupled to a novel rGO-CuFeS2 composite, in presence of H2O2 under acid medium, provides a feasible and highly rapid method to treat RW, reducing its phytotoxicity. Capsule: A novel rGO-CuFeS2 catalyst was developed and applied together with microwave irradiation for an ultra-fast degradation treatment (6 min) in real textile wastewater.