Heavy metals retention (Pb(II), Cd(II), Ni(II)) from single and multimetal solutions by natural biosorbents from the olive oil milling operations

In the present paper, the lignocellulosic residues from the olive oil industry in South-East Italy, namely BOP (Biosorbent from Oil Production), were used as sorbents for heavy metals retention (Pb+2, Cd+2, Ni+2) in water and wastewater treatments. To the purpose, thermodynamic and kinetic investigations for single and multispecies systems were carried-out through batch equilibrium isotherms and column dynamic experiments. In the case of batch tests, maximum metals retentions (qmax) in single ion solutions were 22.4 mg/gBOP, 10.5 mg/gBOP, 5.04 mg/gBOPrespectively for Pb+2, Cd+2and Ni+2, lower figures were detected in the case of ternary systems with values exceeding 10.51 mg/gBOP, 5.11 mg/gBOP, 3.81 mg/gBOPrespectively. Further drastic reductions were detected in tap water. Langmuir and Freundlich isotherms led to good correlations of the data in single-ion and ternary solutions in demineralized water. Freundlich isotherms gave better correlation in tap water. In the case of column tests, operating capacities resulted in the same order with Pb+2> Cd+2> Ni+2. After retention, the exhausted metal converted materials were included into cement conglomerates for a possible employment in the building industry applications, thus minimizing their potential environmental impact.