Removal of Pb(II), Cu(II), and Ag(I) from aqueous solutions using biochar derived by P-enriched water hyacinth

A new synthesis was developed to prepare engineered biochar derived from phosphorous-rich water hyacinth. The statistical analysis indicated a significant correlation between P content and the removal rates of Pb (II), Cu (II), and Ag (I), revealing the pivotal role of enrich P in the biochar for heavy metals (HM) removal. SEM-EDX, XRD and FTIR analyses validated the presence of P functional groups on the surface of P-biochar. Batch experiments showed that the strong acidic initial solution negatively affected the adsorption of HM ions, and a similar negative impact was observed during Cu (II) adsorption under the high ionic strength conditions. Competitive adsorption experiment confirmed P-biochar's resilience against competing metal ions during the adsorption of HM ions. Pb (II) and Ag (I) adsorption were primarily governed by precipitation/reduction, along with complexation reactions involving P functional groups. Cu (II) adsorption was dominated by complexation between Cu (II) and P functional groups.