Investigations on adsorptive removal of PVC microplastics from aqueous solutions using Pinus roxburghii-derived biochar

This study investigates the adsorption mechanisms of pine bark biochar (BC) and modified pine bark biochar (MBC) in the removal of polyvinyl chloride (PVC) microplastics from aqueous solutions, with a significant focus on resource recovery from pine residues which is one of the key Himalayan Forest byproducts. The research findings highlighted the optimal adsorption capacity of biochar at 131.5 mg/g achieved after 6 h of contact time, with a pH of 10 and a PVC microplastic concentration of 200 mg/L. The primary mechanisms of PVC microplastic adsorption involved ion exchange and physical adsorption, driven by forces such as Vander-Waals, London forces, and electrostatic forces. Thermodynamic analysis showed the exothermic nature of the PVC and BC/MBC interaction, with spontaneous adsorption occurring within the temperature range of 10 to 40 °C. Isotherm and kinetic models fit well with Temkin model and PSO kinetics, as indicated by R² values exceeding 0.9. Particularly, MBC exhibited superior removal efficiency and adsorption capacity compared to its precursor, reaching an optimum adsorption capacity of 156.08 mg/g with a removal efficiency of 78%, surpassing the performance of BC. This research contributes valuable insights into potential applications of BC for PVC removal and underscores the effectiveness of MBC in achieving enhanced adsorption outcomes.