Enhanced adsorption activity for phosphate removal by functional lignin-derived carbon-based adsorbent: Optimization, performance and evaluation.

Design of carbon-based adsorbents derived from industrial lignin with superior phosphate adsorption performance is of great significance, yet limited researches have been reported. Here, we report a MgO-functionalized lignin-based bio-charcoal (MFLC) as an efficient adsorbent for phosphate removal. The obtained MgO nanoparticles were dispersed homogeneously on MFLC with particle size of 50-100 nm and higher loading content (28.41%). Benefiting from the favorable morphology of MgO nanoparticles, the MFLC exhibits excellent regeneration ability for phosphate adsorption, which can be applied in a wide range of pH values (2-10). The maximum adsorption capacity could reach to 906.82 mg g-1 for phosphate. Interestingly, the MFLC shows extremely high adsorption activity in the low concentration of phosphate (2 mg P L-1), and its phosphate removal efficiency achieves 99.76%. Furthermore, the results also indicated that the higher loading content of MgO together with smaller particle size can effectively enhance the phosphate adsorption activity of MFLC. The adsorption mechanism revealed that the adsorption of phosphate on the surface of MFLC belongs to single-layer chemisorption, and ligand exchange plays a crucial role during adsorption/desorption. This work not only develops a new strategy for the preparation of high-efficiency carbon-based adsorbents, but also facilitates the value-added utilization of industrial lignin.