Resource utilization of swine sludge to prepare modified biochar adsorbent for the efficient removal of Pb(II) from water

Nowadays lead pollution in water becomes more challenging since the emission of automobile exhaust dust and the wastewater of several lead-manufacture industries. In this study, piggery sludge was utilized to prepare biochar and modified with thiourea to achieve highly efficient wastewater Pb(II) removal. The physical-chemical properties of modified biochar (MBC) were analyzed by X-ray diffraction (XRD), scanning electric microscope (SEM), X-ray photo X-ray photoelectron spectroscopy (XPS) and Zeta potential. Also adsorption isotherm and kinetics of MBC were studied to measure the adsorption capacity of Pb(II) onto biochar. According to the result, the maximum adsorption capacity can reach 145 mg/g and the adsorption reaction rate constants is about 0.0115 g/(mg∙h), which is about 5–8 times higher than that of biochar in other experiments. In order to investigate the mechanism of Pb(II) removal on MBC, FTIR and XPS analysis suggested that surface functional groups such as C–O, CO as well as CS, C–S and RSO3- introduced by modification can adsorb Pb(II) by coordination and ion-exchange. Thiourea modification provided additional functional groups so that modified biochar is able to perform better by chemical and physical adsorption.