Novel Fe3O4-modified biochar generated from rice husk: a sustainable strategy for strengthening lead absorption in wastewater

Water contamination currently threatens human health, which is still a major environmental issue. Scientists are paying attention, in particular, to lead poisoning of water caused by industrial wastes on a global scale. In order to reduce agricultural waste and promote sustainable development, this study created a straightforward process for using leftover rice husks to create biochar. At first, the rice husk biochar was prepared; then, following the immersion of biochar with precursors of Fe2+ and Fe3+ and precipitation under alkaline condition, the Fe3O4 was formed and laid onto biochar to create another magnetic adsorbent known as ferrous-modified biochar. The success of loading Fe3O4 was confirmed by SEM, XRD, FTIR, and BET measurements. The delivered ferrous-modified biochar has a high surface area and correct functional groups for the adsorption process. In order to remove Pb (II) from wastewater, rice husk biochar and ferrous-modified biochar materials were used. Under optimized conditions, synthesized ferrous-modified biochar has a lead adsorbent effectiveness of 95.0% that is related to varying pathways as co-precipitation reaction, complexation reaction, conjugation adsorption, ion exchange, and Fe-O coordination. The Pb2+ adsorption capacity of modified biochar is three times greater than rice husk biochar with 73.68 mg/g. Another evidence of the ferrous-modified biochar adsorbent's excellent recyclable properties is the remaining lead efficiency, which was over 41.2% even after six recycling cycles. Therefore, by this approach of synthesizing Fe3O4 loaded on biochar, the research provided new opportunities for developing low-cost and highly efficient adsorbent to remove heavy metals from water.