Removal of Cd2+, Pb2+ and Ni2+ from water by adsorption onto magnetic composites prepared using humic acid from waste biomass

Biomass-based humic acid (BHA), which is rich in functional groups, was obtained from waste rice straw by a one-step hydrothermal process. The BHA was then co-precipitated with magnetic nanoparticles (MNP) to produce a new magnetic composite [email protected] for the adsorption of Cd2+, Pb2+ and Ni2+ from water bodies. Experimental adsorption data showed that [email protected] adsorbs heavy metal ions very well, with maximum adsorption amounts (Qm) as high as 290.81, 374.99 and 296.85 mg g−1 for Cd2+, Pb2+ and Ni2+. Addition of BHA to MNPs improves their dispersion and resistance to oxidation in water, provides more adsorption sites and increases the specific surface area. Adsorption mechanism of Cd2+, Pb2+ and Ni2+ by [email protected] is largely chemosorption, which is a spontaneous endothermic process. The [email protected] prepared in this study can be readily separated and recycled from solutions, has good adsorption properties and can be easily regenerated, making it a promising new green adsorbent for removing pollutants from water.