Chitosan‐assisted magnetic coconut shell biochar for polystyrene microplastic removal: Mechanism and reusability

Abstract Microplastics presence in the environment has become a serious threat worldwide because of their non‐degradable and toxic nature. We report here the synthesis of a recyclable functionalized magnetic coconut fruit shell biochar (CFS‐MBC) and chitosan‐modified magnetic biochar (CFS‐CSMBC) for polystyrene microplastics (PSMPs) removal from an aqueous medium. The characteristics of CFS‐MBC and CFS‐CSMBC were systematically investigated by using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). In the batch adsorption study, at pH 3, the amount of adsorbent, exposure time 0.6 g and 40 min with PSMPs (80 mg/L concentration) exhibited maximum 91% PSMPs adsorption with CFS‐CSMBC. The experimental findings of adsorption isotherm and kinetics showed a better fit to the Langmuir isotherm and pseudo‐second order models, respectively. Maximum adsorption capacity of 1.98 and 4.75 mg g −1 were reflected with CFS‐MBC and CFS‐CSMBC, respectively. The calculated thermodynamic functions clarified that the PSMPs adsorption phenomenon was spontaneous and exothermic in nature. Reusability investigation reflected that CFS‐MBC and CFS‐CSMBC retained high sorption ability for PSMPs even after five consecutive cycles. Phytotoxicity tests reported that CFS‐MBC and CFS‐CSMBC treated PSMPs solution enhanced growth and biochemical parameters of mustard plants, hence reflecting their practical application prospective. Hence, this study introduces CFS‐MBC and CFS‐CSMBC as an environmental‐benign, highly efficient, multi‐functional and recyclable sorbent for PSMPs removal from aqueous matrices.