Free-standing large-mesoporous silica films decorated with lanthanum as new adsorbents for efficient removal of phosphate

Nowadays, the problem of phosphorus pollution is serious, and it is extremely urgent to deal with the eutrophication of water bodies caused by phosphorus pollution. In order to promote the governance of this problem, free-standing large-mesoporous silica films were successfully prepared using cellulose nanocrystals (CNCs) as templates with evaporation-induced self-assembly (EISA) method, followed by the removal of CNCs by pickling method using sulfuric acid solution. After decoration with biocompatible lanthanum oxide, the novel phosphate adsorbents (La-MSF-x) possessed the superior adsorption performances with high phosphate adsorption capacities (up to 49.98 mg g⁻¹) in experiments. The silica film possessed unique large mesopores with a pore size of approximately 21.07 nm. Moreover, the film adsorbents were used as the host to solve the dilemma of difficult recycling of the powder materials. The results of SEM, FTIR, XRD and XPS analysis of La-MSF-5-P after phosphate adsorption demonstrated that multi-adsorption mechanisms could explain the process of phosphate adsorption. And the formation of “rod-like” randomness crystal LaPO₄ precipitation was the dominant pathway in the adsorption process. Thus these lanthanum-doped large-mesoporous silica films with enhanced performance have great potential in water quality protection.