Catalytic thermal treatment (Thermolysis) process of tannery wastewater for the removal of chemical oxygen demand and color

Abstract

The aim of present research work is to treat the tannery wastewater (TWW) using catalytic thermal treatment process. The treatment of TWW was done on the basis of removal of COD and color in a batch system. All the experiments have been carried out in a batch system. Effect of various process parameters such as pH (2–9), thermolysis time (0–6 h), temperature (55°C–95°C), catalyst loading (Cw) (1–6 g/L), and two types of catalysts (copper sulfate and copper oxide) was studied on the removal efficiency of COD and color from wastewater. Copper sulfate was found to be a better catalyst as compared with copper oxide during thermolysis for TWW. The observed results exhibited that maximum COD removal of 71.36% and color removal of 77.56% were achieved using copper sulfate at the optimized conditions of pH of 4, catalyst loading of 4 g/L, temperature of 95°C, and thermolysis time of 6 h. Kinetic study followed the first order kinetics model and it was observed that the COD reduction was found to be two steps (fast and slow steps) mechanisms. The observed higher values of rate constant (k1) showed that rate of reaction was fast in the first step of thermolysis. Initial pH played an important role in COD removal. The settling rate of the slurry was good and strongly affected by pH values. It has been observed that treated wastewa-ter provided the best (fastest) filterability at the pH 12. The energy consumption was found to be 2,619 kWh/kg of COD removal under the optimized process conditions. Overall, it can be said that thermolysis process can be employed for the treatment of industrial wastewater. © 2021 Desalination Publications. All rights reserved.