Utilizing Waste\nBiomass from Agricultural and Forestry\nSustainable Resources: Biomass Conversion to Functional Adsorbent\nMaterial for Efficient Removal of Total Phosphate in Practical Water

The promotion of the utilization of waste agricultural\nand forestry\nresources (AFRs) as a means of combating environmental pollution represents\nan advanced and necessary development approach with the potential\nto achieve sustainable development. In this work, an advanced adsorbent\nwith a functional Mg–Al bimetallic layer was prepared using\nwaste sawdust biomass (WSD) as a raw material. The layer serves as\nthe primary active component for adsorbing total phosphate from both\nsimulated and real wastewater. The hierarchical structure of the Mg–Al\nbimetallic hydroxide-modified waste sawdust biomass (MA@WSD) has an\nabundance of nanosheets on its surface, providing ample binding sites\nand an enhanced specific surface area of 175.99 m<sup>2</sup>/g. Under\nthe optimal conditions, the maximum removal efficiency toward phosphate\ncan reach 99.99%. The adsorption of phosphate by MA@WSD follows the\npseudo-second order kinetic (PSOK) model, indicating that chemisorption\nis the rate-determining step. Moreover, the thermodynamic data demonstrate\nthe spontaneous nature of the adsorption process, indicating the favorable\ncharacteristics of the developed material. The adsorption mechanism\ncan be summarized as the collaboration of physical adsorption, electrostatic\ninteraction, and chemical adsorption. The results of the regeneration\nprocess indicate that MA@WSD exhibits a retention of 50.3% of its\ninitial adsorption performance following the fifth testing cycle,\nthereby suggesting its potential for comparable reusability. The MA@WSD\nperforms well in adsorbing total phosphate in real river water, and\nthe removal efficiency of MA@WSD is evidently superior to commercial\nactivated carbon, which is at least 70% higher than that of the commercial\nactivated carbon. Besides, the 5-time average removal efficiency toward\ntotal phosphate by MA@WSD is 62.9%, evidently higher than the 29.1%\nof commercially available activated carbon, indicating its potential\nas an alternative for treating phosphorus-containing wastewater. The\nresearch provides theoretical support for harmless treatment, resource\nutilization, carbon sequestration, and emission reduction of waste\nbiomass.