Enhanced selective adsorption of low-concentration phosphorus via layered La₂O₂CO₃ with high environmental adaptability

The highly selective deep purification of low-concentration phosphorus has garnered increasing attention. This article employs a novel strategy involving the calcination and reconstruction of Mg/La LDH, leading to the successful preparation of La-based adsorbents (LC-1, LC-2, LC-3). Among them, LC-1, which features a layered La₂O₂CO₃ structure, exhibits excellent phosphorus adsorption performance. At a low dosage (0.1 g/L), it rapidly reached adsorption equilibrium within 100 min, ultimately reducing the phosphorus concentration from 10 mg/L to less than 0.02 mg/L. In the pH 2–13 tests and regeneration tests, LC-1 displays minimal La leaching (<0.04 mg/L) and stability of 10 cycles phosphorus removal (adsorption capacity exceeds 90 mg/g), in contrast to the performance of Mg/La LDH (limited to 5 cycles). LC-1 also has extraordinary environmental adaptability, exhibiting a phosphorus adsorption capacity of over 95.7 mg/g in the presence of interfering anions and humic acid (HA), as well as maintaining a phosphorus adsorption capacity of over 85 mg/g at 5 °C. Analysis suggests that the novel preparation strategy was conducive to forming stable La₂O₂CO₃ species, alleviating metal ion dissolution and optimizing the content and proportion of La³⁺, electrophilic oxygen species (O₂²⁻/O⁻) and interlayer CO₃²⁻. The above are critical factors in controlling the adsorption rate, improving the pH resistance and stability of adsorbents. In summary, La₂O₂CO₃ has not only exhibited outstanding adsorption performance but also boasted a simple preparation strategy, rendering it highly promising for applications in the removal of low-concentration phosphorus.