Usually, the removal of heavy metals by the biomass is mainly attributed to the stable and insolublematrix with active groups (e.g.carboxyl, amino and hydroxyl groups) on the surface of biomass[14,15].
Whereas, many biomass materials often contain few activegroups and exhibit low adsorption capacities when used in asreceivedforms [16].
Chemical modification, a widely used methodto endow materials with desirable properties for certain applica-tions, can be employed to improve the adsorption performanceof biomass [17–20].