Lanthanum compounds-modified rectorite composites for highly efficient phosphate removal from wastewater

Abstract The development of a facile method to fabricate eco-friendly and efficient adsorbents for removing phosphate from wastewater is urgently needed. In this study, a low-cost, eco-friendly, and high-performance composite, with highly dispersed lanthanum compounds (lanthanum oxynitrate and lanthanum oxycarbonate) on the two-dimensional (2D)-layered rectorite (REC) nanoclay, was synthesized via a one-pot calcination method. Lanthanum compounds-modified rectorite composite (La-REC) was analyzed to confirm the combination between lanthanum compounds and the surface of REC. La-REC perfectly followed the Langmuir-Freundlich model and exhibited a superior adsorption capacity of 147.6 mg P/g for phosphate, higher than that of both REC and La(OH)3. More importantly, it demonstrated high performance for phosphate adsorption within pH ranging from 4.0 to 7.0, and showed a high adsorption selectivity toward phosphate among coexisting ions during the adsorption process. La-REC could efficiently remove phosphate from real wastewater. Furthermore, lanthanum compounds and REC nanoclay had a synergistic effect of increasing the phosphate uptake. The mechanism of phosphate removal by La-REC was investigated, including ligand exchange, electrostatic attraction, complexation, and precipitation. Overall, La-REC provides feasibilities to synthesize the low-cost, eco-friendly, and high-performance adsorbents for phosphate removal, which can offer potential applications in phosphate adsorption for practical pollutant purification.