Competitive Adsorption Studies of MgFe2O4-Biochar Nanocomposites for the Removal of Chromium and Nickel Ions in Single and Binary Metal Ion System

The presence of heavy metal ions in water bodies constitutes a significant environmental hazard. The development of sustainable and cost-effective adsorbent materials for their removal is an urgent priority. In alignment with this critical objective, the present study explores the potential of a novel composite material for water remediation. This composite, fabricated from biochar and magnesium ferrite nanoparticles, targets the removal of hexavalent chromium and divalent nickel. While prior research has explored the application of rice husk as an adsorbent, no investigation, to our knowledge, has examined the potential of magnesium ferrite-rice husk composites for this purpose. Initial screening identified the biochar-magnesium ferrite composite (pre-calcination) as the most effective adsorbent. This composite displayed a superior surface area (151 m²/g) compared to calcined magnesium ferrite (91 m²/g) and achieved exceptional removal efficiencies for both chromium (50 mg/g) and nickel (54 mg/g). Optimal chromium removal occurred at pH 1 with a 110-minute contact time, while nickel favored a pH of 6 and the same contact time. The adsorption process was characterized as physisorption and endothermic. Notably, the composite exhibited efficient regeneration (82% for nickel and 90% for chromium) using simple acid/base solutions. The BJH analysis of pore characteristics indicated an average pore diameter of 1.5365 nm and a total pore volume of 0.17 cm³/g. The research findings demonstrate the composite’s effectiveness as a sustainable adsorbent for capturing heavy metal ions from water. Graphical Abstract