Confined La(2)O(3) particles in mesoporous carbon material for enhanced phosphate adsorption

Novel phosphate adsorbents with confined La(2)O(3) inside mesoporous carbon were fabricated by the solid-state grinding method using pristine mesoporous carbon material CMK-3 (PCMK-3) and oxidized CMK-3 (OCMK-3) as the matrixes (denoted as La(2)O(3)@PCMK-3 and La(2)O(3)@OCMK-3). Compared with pure La(2)O(3), La(2)O(3)@PCMK-3 and La(2)O(3)@OCMK-3 exhibited higher normalized phosphate adsorption capacity, indicative of efficient loading of La(2)O(3) inside the mesopores of the carbon materials. Furthermore, La(2)O(3) loading led to substantially enhanced phosphate adsorption. The adsorption capacities of La(2)O(3)@OCMK-3 samples were higher than those of La(2)O(3)@PCMK-3 samples, possibly owing to the oxygen-containing groups forming in OCMK-3 during HNO(3) oxidation, which enhanced the dispersion of La(2)O(3) in the mesopores of OCMK-3. The adsorption capacities of La(2)O(3)@PCMK-3 and La(2)O(3)@OCMK-3 increased with the La(2)O(3) loading amount. Phosphate adsorption onto La(2)O(3)(14.7)@PCMK-3 followed the pseudo-second-order kinetics with respect to correlation coefficient values (larger than 0.99). As pH increased from 3.4 to 12.0, the phosphate adsorption amounts of La(2)O(3)(14.7)@PCMK-3 and La(2)O(3)(15.7)@OCMK-3 decreased from 37.64 mg g(−1) and 37.08 mg g(−1) to 21.92 mg g(−1) and 14.18 mg g(−1), respectively. Additionally, La(2)O(3)@PCMK-3 showed higher adsorption selectivity towards phosphate than coexisting Cl(−), [Formula: see text] and [Formula: see text]. The adsorbent La(2)O(3)(14.7)@PCMK-3 remained stable after five regeneration cycles.