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.