Magnetic Biochar Adsorbent for Adsorptive Removal of Microplastics

Abstract

This study addresses the need for effective removal of microplastic from the aquatic environment through development of an efficient adsorbent derived from coconut husk (CH) waste. In this study, biochar (BC) and magnetic biochar (MBC) adsorbents were produced through process called carbonization and impregnation with iron (Fe). The spectral analysis of the adsorbents revealed the presence of functional groups such as hydroxyl (O–H), alkene (C = C), and carbonyl (C–O). The textural properties analysis showed a sufficiently high specific surface area (S_BET) of 428 and 437 m²/g for the BC and MBC adsorbents, respectively. The adsorbents are composed of high elemental carbon composition (>60%) that will facilitate microplastic binding onto the surface of the adsorbent. The microplastic adsorption measurement study at initial concentration of 50 mg/L with adsorbent dosage of 25 mg and contact time of 8 h shows the adsorption capacity increased with contact time, reaching maximum of ∼23 and ∼10 mg/g for BC and MBC adsorbents, respectively. The adsorption modeling analysis reveals the adsorptions of microplastic by BC adsorbent occur through homogenous monolayer chemical adsorption process, whereas for MBC adsorbent, it is heterogenous multilayer chemical adsorption. The BC adsorbent demonstrated excellent regenerative capability compared to MBC adsorbent after five regeneration cycles, with removal capacity maintained above ∼75%. These findings could demonstrate the promising potential of CH-derived BC as an effective adsorbent for mitigating microplastic pollution.