Recycling wool-dyeing effluents after renovation through photocatalysis with Cu-Fe bimetallic-grafted polytetrafluoroethylene fiber complex and H2O2

Abstract

A Cu-Fe bimetallic-poly acrylic acid-grafted polytetrafluoroethylene (PTFE) fiber complex (Cu-Fe-PAA-g-PTFE) was prepared as an effective heterogeneous photo-Fenton catalyst for oxidative treatment and recycling of acid dye effluents from dyeing of wool fabric. Important factors affecting acid dye degradation, namely catalyst loading, H2O2 concentration, solution pH, and dye concentration, were examined to optimize the photo-Fenton process conditions for the treatment of acidic dyeing effluents. Three acid dyes were used for the coloration of wool fabrics by a regular exhaustion process. The resulting wool-dyeing effluents were then treated using the optimized photo-Fenton process. The impact of recycling on the quality of the dyed wool fabric was also investigated. A photo-Fenton reaction system consisting of Cu-Fe-PAA-g-PTFE and H2O2 successfully degraded the acid dyes in water. Complete decoloration and a relatively high TOC (total organic carbon) removal percentage were achieved in 4.0 h under ultraviolet radiation for real wool-dyeing effluents when 7.0 g/l Cu-Fe-PAA-g-PTFE and 7.0 mmol/l H2O2 were used. The number of recycled effluents was found to be highly determined by their quality and dyeing properties of the acid dyes used. The dyeing quality was not affected for three successive cycles. However, lighter shades, significant color differences, and deteriorated fastness were observed for dyed wool fabrics in the fourth dyeing cycle, possibly because of an increase in the residual TOC value of the renovated effluents. Further TOC reduction of the treated effluents is therefore needed for their repeated reuse in more than three dyeing cycles.