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Clean water production from plastic and heavy metal contaminated waters using redox-sensitive iron nanoparticle-loaded biochar

Environmental Research 2023 22 citations ? Citation count from OpenAlex, updated daily. May differ slightly from the publisher's own count.
Zahid Ahmad Ganie, Nitin Khandelwal, Aniket Choudhary, Gopala Krishna Darbha

Summary

Researchers developed a biochar material loaded with iron nanoparticles that can simultaneously remove nanoplastics and heavy metal ions from contaminated water. The material achieved over 90 percent removal across a range of water conditions and worked effectively in both batch and continuous-flow tests. The study presents a practical, low-cost approach for cleaning up water polluted with both plastic particles and toxic metals.

The unceasing release of tiny plastics (microplastics and nanoplastics) and their additives, like metal ions, into the aquatic systems from industries and other sources is a globally escalating problem. Their combined toxic effects and human health hazard are already proven; hence, their remediation is requisite. This study utilised the nano-zerovalent iron-loaded sugarcane bagasse-derived biochar (nZVI-SBC) for simultaneous removal of Nanoplastics (NPs) of different functionality and size along with metal ions (Ni, Cd, AsO, and CrO). Batch and column experiments were conducted, and the results showed an efficient removal of contaminants with maximum sorption of carboxylate-modified NPs of size 500 nm (q = 90.3 mg/g) among all three NPs types. Significant removal was observed in Cd in case of cations and CrO in case of anions with q = 44.0 and 87.8 mg/g, respectively. Kinetics and the isotherm modelling better fitted the pseudo-second-order kinetic model and Sips isotherm model, respectively for both NPs and metal ions. The designed material worked well in pH range of 4-8, ionic strength 1-20 mM and in complex aqueous matrices, with >90% removal. FTIR, zeta potential and the imaging analysis of the reaction precipitates confirmed the electrostatic attraction, pore retention and complexation as the potential mechanisms for removing NPs, whereas, XPS studies confirmed the reduction co-precipitation and surface complexation as the possible mechanism for removing metal ions. High values of attachment efficiency factor calculated from colloidal filtration theory (CFT) validated the experimental results and justified the high sorption of carboxylate modified 500 nm NPs particles. The synthesized material successfully removed both NPs of varying size and functionality and metal ions simultaneously with significant efficacy in complex environmental samples proving the broad applicability of material in realistic environmental conditions and different types of water treatment processes.

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