Compositional effects of rice husk based activated carbon on properties of steel waste derived magnetite nanoparticles

Magnetite nanoparticles (Fe 3 O 4 NPs) are limited by low surface area, fewer functional groups, high agglomeration tendency, and poor dispersibility in aqueous media. In this study, Fe 3 O 4 NPs were functionalized with activated carbon (Fe 3 O 4 @AC) through co-precipitation in compositional weight ratios of Fe 3 O 4 : AC of 1:1, 2:1, 3:1, designated as Fe 3 O4@AC-1, Fe 3 O4@AC-2, Fe 3 O4@AC-3, respectively. Ferric chloride from acid leached iron oxide waste powder was used as a starting material for Fe 3 O 4 NPs, while AC was derived through chemical activation of rice husks with zinc chloride. Materials were characterized by XRD, BET, SEM, TEM, FTIR, SAED, DLS-zeta potential (ZP), UV-vis spectroscopy, VSM, as well as electro-transfer properties using cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Pure Fe 3 O 4 NPs, and the nanocomposites were all polycrystalline with crystallite sizes between 6- 9 nm. The nanocomposites had more functional groups, higher band gap energies, less agglomerated, and better colloidal stability than bare Fe 3 O 4 NPs. The surface area (SA), and microporosity percentages of the nanocomposites decreased in the order Fe 3 O4@AC-1 (440 m 2 /g, 33.25%) > Fe 3 O4@AC-2 (400 m 2 /g, 28.14%) > Fe 3 O4@AC-3 (233 m 2 /g, 10.04%). Saturation magnetization decreased in the reverse order of 66.2 emu/g > 43.8 emu/g > 32.2 emu/g with all materials retaining sufficient magnetic response for magnetic separation applications. Fe 3 O4@AC-1 show properties consistent with suitability for pollutant removal in water. Fe 3 O 4 @AC-2 exhibited superior performance with highest peak currents in CV and lowest charge transfer resistance in EIS, factors typical for electrochemical applications.