Critical review of La(III)-based absorbents toward phosphate adsorption from aqueous solutions: mechanisms, adsorbent design, and prospects

Phosphate removal technology has faced significant challenges due to the growing global population and agricultural inputs. Lanthanum-based adsorbents (LBA) have gained attention because of their high efficiency in removing phosphate. While the LBA has been studied since the 1990s, most of the related research has focused on theoretical aspects rather than practical applications. This review will demonstrate the various types of LBA available on the market and how different factors, such as temperature, pH, natural organic matter (NOM), inorganic ions, and initial phosphate concentration, affect the variation in phosphate removal. Additionally, the mechanism of phosphate removal by LBA, including ion exchange, ligand exchange, electrostatic interactions, Lewis acidbase interactions, and H-bonding, will be examined. From the standpoint of practical application, this review thoroughly examines not only the mechanism of phosphate removal by LBA but also the analysis of currently available LBA, determining its potential toxicity to humans and crops, as well as phosphate recovery following adsorbent use. LBA, which can also be used as fertilizer, is efficient at removing phosphate and has low toxicity. However, their efficiency in removing phosphorus is affected by coexisting substances such as pH, temperature, and NOM. We provide suggestions for future directions in LBA research based on the current body of knowledge.