A comparative study on the efficiency of biochar and iron-modified biochar for Pb-removal from aqueous solutions

Water contamination with potentially toxic elements (PTEs) poses a serious environmental threat. This study explored a sustainable solution for wastewater treatment using biochar derived from sugarcane bagasse. Two types of biochar: regular (BGB) and iron-modified (BGBFe) were tested for Pb(II) removal from contaminated water. Scanning electron micrograph spectra of both types of biochars revealed their porous structure. A batch study was conducted to investigate the efficiency of BGBFe and BGB for Pb(II) removal from aqueous solutions over a time period up to 360 min. The results revealed significant differences. Within the first 3 hours, BGB removed over 70% of lead, whereas, BGBFe’s achieved a lower removal rate of only 27%. This suggests that regular biochar (BGB) is a promising option for short-term lead remediation in water. The iron modification (BGBFe) did not enhance lead removal and may not be a suitable strategy. The kinetics of Pb(II) sorption and desorption were investigated using 6 kinetic models. Based on the highest r2 values and the lowest standard error of estimate ones, the kinetics of Pb(II) sorption on BGB biochar was best fitted by the first-order kinetic model. Similarly, Pb(II) desorption on this biochar followed the same kinetic model; however the first-order kinetic constant was approximately 4 times higher in the first phase than in the second one. In contrast, Pb(II) sorption kinetics on BGB-Fe was better described to the power-function model; while the desorption data was suited to the second-order model. In conclusion, BGBFe is not a suitable additive for treating waters contaminated with Pb(II). Regular biochar could be more helpful; but within a time frame not exceeding 3 h.