BACKGROUND: Chemical industry wastewater is challenging to treat because of the various chemicals they contain. In this study, the treatment of chemical industry wastewater, which produces a wide variety of chemical aids, such as foam control agents, and silicones used in the textile, food and cosmetics industries, by coagulation combined with Fenton or photo‐Fenton oxidation processes was investigated. In coagulation studies, optimum pH and coagulant dose were determined with polyaluminum chloride (PAC), polyaluminum chloride hydroxide sulfate (PACS) and FeCl₃ coagulants, while Fe²⁺, H₂O₂, pH and oxidation time were optimized in Fenton studies.RESULTS: In the coagulation, higher wastewater treatment was achieved with PAC compared to PACS and FeCl₃ coagulants, and 62.6% chemical oxygen demand (COD) and 44.3% total organic carbon (TOC) removal were obtained at 500 mg L⁻¹ PAC and pH 8. In the coagulation and Fenton oxidation, 92.4% COD, 79.7% TOC, 99.8% turbidity, and 96.7% total soluble solids (TSS) were achieved. The application of photo‐Fenton oxidation instead of Fenton oxidation did not cause a significant change in chemical industry wastewater. The cost of chemical industry wastewater treatment by coagulation and Fenton oxidation was calculated as $19.16 m⁻³, and the cost per kilogram of COD_removed was determined as $2.89 kg⁻¹.CONCLUSION: In chemical industry wastewater treatment, high TSS and turbidity removal can be achieved by coagulation with PAC, and the wastewater load subjected to Fenton oxidation can be reduced. Efficient wastewater treatment was provided by Fenton oxidation after coagulation. The application of the photo‐Fenton oxidation process instead of Fenton oxidation did not show the expected effect. However, toxicity studies should be performed in treated wastewater using coagulation–Fenton oxidation processes in future studies. © 2023 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

The aim of this article was to clarify which type of dye chromophores could be decolorized efficiently with the use of laccase enzyme. For this purpose, enzymatic degradation of different type of dye classes (4 reactive, 2 acid and 1 basic dye) having various chromophore groups was investigated by using commercial laccase from Cerrena unicolor. It was observed that the chromophore structure of dye is very important on enzymatic color removal efficiency. According to the experimental results, it was found that color removal efficiencies (20 mg/L initial dye) were 98.7% for RB220 (0.1 g/L enzyme after 6 h), 95.1% for RB19 (0.1 g/L enzyme after 48 h), 90.8% for AR42 (0.1 g/L enzyme after 48 h) while they were 60.9% for AR114 (0.25 g/L enzyme), 58.6% for RB21 (0.5 g/L enzyme), 39.7% for RR239 (0.25 g/L enzyme) even after seven days. As a result, it can be said that the highest decolorization rate was achieved for the reactive dye having formazan copper complex (RB220) chromophore. On the other hand, the enzymatic degradation of basic dye (BB9) was found to be rather difficult compared to the acid and reactive dyes used in this study and the maximum color removal was 42.8% after seven days.