Efficient removal of phosphate from aqueous media using magnetic bimetallic lanthanum‑iron-modified sulfonylmethylated lignin biochar

The use of lignin carbon as an adsorbent for the adsorption of phosphates from wastewater is a promising technology. However, most lignin carbon-based adsorbents still suffer from low adsorption efficiency and poor selectivity. Herein, a novel FeLaO3-modified sulfomethylated lignin (SL) biochar adsorbent (FLO@CSL) was prepared for phosphate removal. The development of this adsorbent took into consideration the strong affinity of lanthanum (La) and iron (Fe) (hydro) oxides for phosphate and the excellent carrier properties of lignin-based biochar. As the core of FLO@CSL, FeLaO3 active sites are highly dispersed on the surface of SL biochar. Besides, doping of Fe(III) not only imparts magnetic properties to FLO@CSL, thereby effectively improving the separation efficiency of the adsorbent, but also enhances the phosphate adsorption performance. Performance studies revealed that FLO@CSL exhibits remarkable adsorption selectivity and substantial phosphate-adsorption capacity. Notably, the maximum adsorption capacity was found to be 137.14 mg P g-1. Phosphate adsorption on the FLO@CSL surfaces proceeds via chemisorption in a single layer, and ligand exchange plays an important role in determining the adsorption behaviour. Because of its exceptional selectivity, remarkable adsorption capacity and outstanding magnetic separation efficiency, FLO@CSL is a highly promising adsorbent material for effectively treating phosphates in wastewater.