Co-pyrolysis of textile dyeing sludge with waste cooking oil: a dual-waste management approach for producing efficient dye adsorbent

Abstract

The textile industry plays a crucial role in the global economy but also generates hazardous wastes like Textile Dyeing Sludge (TDS), which is challenging to manage due to its high ash content. This study explores the co-pyrolysis of TDS with Waste Cooking Oil (WCO), a carbon-rich secondary waste, to improve the properties of TDS and convert it into an adsorbent. An 80:20 mass ratio of TDS: WCO blend was pyrolyzed at 500 °C, and derived biochar was evaluated for methylene blue dye removal. The thermogravimetric analysis results clearly revealed synergy between TDS and WCO, which helped in enhancing the carbonization process. FTIR analysis confirmed the degradation of surface functional groups and the formation of more aromatic and hydrophobic structures after pyrolysis, which enhance adsorption. The blended biochar showed superior adsorption properties with an adsorption capacity of 141 mg/g and removal efficiency of ~91%. Isothermal data for biochar derived from blended sample showed that it fits both Langmuir and Freundlich models well (R² ≈ 0.98), indicating the presence of both homogeneous and heterogeneous sites. This study suggests co-pyrolysis of TDS and WCO as a promising dual waste management solution, producing low-cost, eco-friendly adsorbents suitable for textile wastewater treatment, supporting circular economy and sustainable development goals.