Co-pyrolysis of tea waste and metallised plastic waste: Product characterization, kinetic analysis, and activated...

The sustainable valorization of solid wastes into valuable biofuels and advanced materials offers a promising pathway for resource recovery and circular economy. Co-pyrolysis of tea waste (TW) and metallic waste plastic (MWP) is investigated at 550 °C for three different blends (75:25, 50:50, and 25:75). The thermal breakdown of metallic waste plastic, tea waste, and their blends is examined by three distinct types of iso-conversional kinetic models: Ozawa-Flynn-Wall (FWO), Kissinger-Akahira-Sunose (KAS), and TANG. Tea waste pyrolysis produced the maximum output of bio-oil (29.58 wt%) and biochar (31.50 wt%), while MWP produced the highest yield of non-condensable gases (NCG) (70.13 wt%). The biochar produced from MWP has a high calorific value of 30.15 MJ/kg and a carbon content of 70.91 wt%. The bio-oil obtained from tea waste is rich in phenolics, while that from MWP has aliphatic hydrocarbons with higher calorific values and lower oxygen concentration. The bio-oil derived from the TW: MWP (50:50) blend co-pyrolysis had the most acids and alcohols, and enhanced fuel characteristics. With an increase in the MWP percentage in the blend, the carbon and ash content increased in the biochar due to the presence of aluminium and other inorganic substances. The biochar generated from the co-pyrolysis of TW: MWP (50:50) is transformed into activated carbon (AC/TW50:MWP50) and utilised as an effective adsorbent for malachite green dye. A highest adsorption capacity of 182.89 mg/g and removal rate of 90.80% is achieved with AC/TW50:MWP50 towards malachite green dye in wastewater treatment. The high removal rate and adsorption capacity of the AC/TW50:MWP50 are due to its high surface area of 714 m²/g. Overall, this study demonstrates that the co-pyrolysis of TW and MWP is a highly effective, dual-purpose strategy for managing complex solid wastes, generating upgraded biofuels, and synthesizing high-performance adsorbents for environmental remediation.