Optimization and hexavalent chromium removal from aqueous solution using zero valent iron nano particles

Mining and industrialization are among the most common human activities that discharge heavy metals to the water bodies. Those released heavy metals have healthy problems for humans. Water pollution by heavy metals, particularly hexavalent chromium [Cr (VI)], poses severe risks to human health and impact the environment due to its toxicity and persistence. This study investigates the removal of Cr (VI) from aqueous solution using green synthesized zero-valent iron nanoparticles (ZVI NPs) derived from Croton macrostachyus leaf extract. The basis behind choosing ZVI NPs lies in their high surface reactivity, eco-friendliness, and strong reduction potential for Cr (VI). Batch adsorption experiments were optimized using Response Surface Methodology (RSM) based on Central Composite Design (CCD). The optimal conditions were pH 6, ZVI NP dose 0.4 g, contact time 72 min, and temperature 40 °C, achieving a maximum removal efficiency of 95.5%. Adsorption behavior followed Langmuir isotherm (RL = 0.08) and pseudo-second-order kinetics, indicating monolayer chemisorption. The point of zero charge (pH = 6) was determined to support the working pH conditions. While the method is promising for Cr (VI) removal, future studies should explore scale-up feasibility and long-term stability. This green approach demonstrates potential for sustainable wastewater treatment.