The modification of biomass waste by cerium-based MOFs for efficient phosphate removal: excellent performance and reaction mechanism

Abstract

Due to the possibility of causing eutrophication, excessive phosphate discharged into water bodies always threatens the stabilization of aquatic ecosystem. A promising strategy is to remove phosphate from water by the utilization of biomass waste as adsorbents. In this paper, the corn straw (CS) and pine sawdust (PS) are chosen for adsorption; however, the phosphate removal capacities of them are very limited. Considering the high phosphate uptake of trivalent cerium, Ce (III)-based nanoparticles (CD and CT) are selected to be loaded on the biomass by hydrothermal synthesis to obtain four modified materials. CD is metal organic frameworks (MOFs) with Ce5(BDC)7.5(DMF) 4 as its molecular structure, while CT is MOFs derivatives with [Ce (HCOO)]n as its crystal structure. The adsorption capacities of CS-CD, PS-CD, CS-CT and PS-CT reach 181.38, 183.27, 225.55 and 186.23 mg/g. But on account of the different molecular structures, CS-CD and PS-CD achieve great phosphate uptake under wide applicable scope of pH from 2 to 11, whereas CS-CT and PS-CT only under acidic conditions. The analysis of the adsorption mechanism indicates that due to the unsaturated coordination bond of CD, it could remove phosphate through coprecipitation and ion exchange even under alkaline conditions.