As pollution escalates, water purification is becoming crucial, with adsorption emerging as an efficient technique. This study aimed to evaluate the effectiveness of iron-modified rice husk biochar as an adsorbent for water pollutants. The biochar was produced at a pyrolysis temperature of 500 °C and modified by FeSO₄·7H₂O. Diverse adsorbent dosages were introduced to simulated wastewater containing aldrin, mercury (Hg²⁺), lead (Pb²⁺), and cadmium (Cd²⁺). The solution was agitated for 60 min, then filtered, and the samples were sent for analysis. The results were promising; aldrin had a removal efficiency of 100%. The removal efficiency for Hg²⁺ ranged from 99.80% to 99.96%, for Pb²⁺ from 88.90% to 99.56%, and for Cd²⁺ from 78.90% to 99.98%. The Freundlich adsorption isotherm best described the mono- and quaternary component systems, while the Langmuir isotherm was the best fit for the binary system. Therefore, iron-modified rice husk biochar shows potential as a sustainable and efficient adsorbent for wastewater treatment.

Recent research has explored the potential of rice husk biochar as a low-cost adsorbent for the removal of contaminants from aqueous solutions, including aldrin, mercury (Hg2+), lead (Pb2+), and cadmium (Cd2+). Experimentation involved adding varying doses of biochar to wastewater with different contamination levels, agitating the mixture for 60 min, and filtering the solutions for analysis. The experiment revealed impressive removal efficiencies: 100% for aldrin, 99.92% – 99.99% for Hg2+, 95.90% – 99.52% for Pb2+, and 88.60% – 99.46% for Cd2+. In binary and quaternary mixtures, Hg2+ showed higher removal efficiency than Pb2+ and Cd2+, with the exception of aldrin. The adsorption order was identified as aldrin > Hg2+ > Pb2+ > Cd2+. The Freundlich adsorption isotherm best described heavy metals in the mono and quaternary component adsorption, while the Langmuir adsorption isotherm was a better fit for the binary component. Consequently, the study highlights rice husk biochar as an efficient, sustainable, and environmentally friendly option for wastewater treatment.

Adsorption is one of the most easy-to-operate, less costly, efficient and, most importantly, environmentally friendly methods of removing toxic metals from aqueous environments. We used spent Impra Green Tea Ginseng Flavoured to recover mercury (Hg2+), lead (Pb2+) and cadmium (Cd2+) in binary and ternary systems from greywater. We undertook this study in binary and ternary systems at adsorbent dosages with a corresponding 100 mL varied initial metal concentrations of the greywater. The adsorption efficiency at varied concentrations and dosages in the binary systems by the spent tea waste ranged from 38.5% to 100% for lead, 11.50% to 100% for cadmium and was 100% for mercury. In the ternary system, the adsorption efficiency of toxic metals ranged from 28.91% to 72.85% for cadmium and was 100% for mercury and lead. The maximum adsorption capacity (Qe) for toxic metals in the binary system ranged from 38.46 to 81.97 mg/g for Pb2+ and 12.64 to 56.82 mg/g for Cd2+. The Langmuir adsorption isotherm model was the best fit for the adsorption of toxic metals by Impra Green Tea Ginseng Flavoured. The pH under which the experiments were conducted showed very high removal efficiency for lead and mercury but lower removal efficiencies for cadmium. Spent Impra Green Tea Ginseng Flavoured can be used as an effective and low-cost adsorbent of toxic metals from greywater or wastewater. Based on our findings, further studies should be conducted to determine the effects of varying the contact time, temperature and elevated metal concentrations in the greywater or other wastewater. Significance: This study provides useful information on how spent Impra Green Tea Ginseng Flavoured can be used as an effective and low-cost adsorbent of toxic metals from greywater or wastewater.