Alternative stepwise adsorption process of environmental waste-based biochar for treating dental wastewater containing lead and chromium

Heavy metals from dental wastewater raised serious environmental health concerns. To address this, an environmental waste-based biochar by eggshell and fly ash was synthesized and characterized. The adsorption characteristics of lead and chromium by biochar were explored and a novel alternative stepwise adsorption process was proposed to improve the removal efficiency. Results indicated that the specific surface area was determined to be 537.6 m2/g. The maximum adsorption capacity for lead and chromium were 149.3 mg/g and 119.0 mg/g, respectively. A theoretical calculation model was developed to predict the concentration of the effluent, followed by experimental validation. The findings indicated that the concentrations of lead and chromium in the effluent remained stable, while the average removal efficiency of lead and chromium increased by 5.56% and 7.02%, respectively, compared to the conventional adsorption method. The calculated values aligned well with the experimental results, demonstrating the success of this innovative adsorption process.