Heterogeneously Porous Multiadsorbent Clay–Biochar Surface to Support Redox-Sensitive Nanoparticles: Applications of Novel Clay–Biochar–Nanoscale Zerovalent Iron Nanotrident (C-BC-nZVI) in Continuous Water Filtration

An eco-friendly layered-porous C-BC surface was prepared by intercalating properties of layered bentonite clay (C) having high cation-exchange capacity, with biochar (BC), containing pores and vast functionality, and utilized to support redox-sensitive zerovalent iron (nZVI) nanotrident particles. The synthesized C-BC-nZVI nanotrident was characterized for morphology, porosity, crystallinity, functionality, and suspension stability and then evaluated for various environmental applications such as REE extraction, toxic metal removal, and sorption of dyes. Results show heterogeneous pore distribution on the C-BC-nZVI surface with dispersed-unoxidized 20–30 nm sized nZVI particles. C-BC-nZVI had shown 100% extraction of REEs (La, Ce, and Nd) along with >90% removal of various toxic metals (As, Cd, Cr, Ni, Hg, and Pb). In the dye mixture, the nanotrident showed selective sorption of methylene blue (MB). The impact of environmental complexities on the nanotrident’s reactivity for metals and MB dye was further delineated using CrO₄^2–, Ni²⁺, and MB. Results show no influence of pH and dissolved organic matter (DOM) variation on Ni²⁺ and MB sorption. Further efficient sorption, reduction, and coprecipitation of all the contaminants, i.e., CrO₄^2– (44.3 mg/g), Ni²⁺ (570.5 mg/g), and MB (52.1 mg/g) in groundwater and <10 μg/L release in the elute obtained from the continuous flow column until the breakthrough point confirms the multifunctionality and applicability of the nanotrident in the natural environment.