Upcycling spent bleaching clay into clay/carbon composites for adsorptive removal of Pb(Ⅱ)

Spent bleaching clay (SBC) is a by-product of refining edible oil. The adsorbed oil in SBC can be recycled into aromatics via catalytic pyrolysis, whereas the solid product is a biological carbon-rich clay (PBC). In order to achieve the value-added utilization of PBC, an effective method was developed to prepare clay/carbon adsorbent (SBC/C–S) with high adsorption performance, and its adsorption capability was evaluated by adsorbing Pb(Ⅱ) from simulated Pb(Ⅱ)-contaminated wastewater. PBC was activated with sulfuric acid after pyrolysis to produce SBC/C–S, while the clay structure maintained the major mineral structure. The formed carbon layer primarily contributed to the microporous structure and active sites on surface, which was conducive to the efficient Pb(Ⅱ) adsorption. The adsorption thermodynamics and kinetics of SBC/C–S were studied via fitting different mathematical models, and the results matched well with pseudo-second order and Freundlich models. The adsorption mechanism of SBC/C–S might be electrostatic attraction or chemical complexation. The adsorption capacity of SBC/C–S reached 315.60 mg/g, much higher than that of fresh and H 2 SO 4 activated bleaching clays (69.03 and 295.28 mg/g). Therefore, SBC/C–S is a potential adsorbent with great reusability for Pb(Ⅱ) removal from industrial wastewater, which achieves the recycling and effective utilization of waste material.