Removal of polypropylene nanoplastics from aqueous solution by biochar derived from Date palm fibers: Kinetics and isotherms studies

Abstract

In this work, activated carbon (AC) derived from powder of date palm fibers (DPF) was examined as an adsorbent for removing polypropylene nanoplastics (PPNPs) from aqueous solutions. The adsorbent was characterized using XRD, FT-IR, and SEM analyses. Affecting parameters on removal efficiency in a batch reactor, such as contact time, concentration of PPNPs and amount of adsorbent, were evaluated and optimized. Equilibrium and kinetic studies are performed to understand adsorption mechanisms. In the batch system, 30 mL of polypropylene suspension (5-40 mgL-1) was added to Erlenmeyer flask. First, different amounts of AC adsorbent were added to the container, then microplastic was added to the reactor. The mixture was shaken on a shaker for four hours at 25oC. The flask was removed from the shaker, the concentration of PPNPs in the supernatant was measured, and a settling time of 30 min was obtained. A control suspension system without PPNPs nanoplastics (with biochar and without PPNPs) was also performed to evaluate carbon particle interference by turbidity measurements. Our results showed that kinetic data were consistent with the pseudo-second-order kinetic model. Equilibrium data for the adsorption of PPNPs on biochar represented by the Langmuir isotherm model is better than the Freundlich isotherm model.