Preparation of La-doped NiAl-LDH with boosted electron transfer for the enhanced photocatalytic activity of tetracycline: Performance evaluation, degradation pathway, and mechanism insight

Developing a photocatalysis-based system is an effective strategy for removing antibiotics. Herein, La-doped NiAl-layered double hydroxides (LaNiAl-LDH) photocatalyst was synthesized using a chemical co-precipitation-hydrothermal method. The prepared samples were characterized by various advanced analyses and investigated for the photocatalytic degradation of tetracycline (TC). The crystalline phase and functional groups of the synthesized samples were successfully confirmed by XRD and FTIR analyses. By doping La into NiAl-LDH structure, the band gap was reduced from 3.01 eV to 2.57 eV, indicating higher photocatalytic activity of 1% LaNiAl-LDH. The surface morphology of the synthesized samples shows the formation of nanosheets in the structure of LDH. Under the optimum status ([TC]₀ = 10 mg/L, [1% LaNiAl-LDH] = 0.2 g/L, and pH = 6), the photocatalytic activity of 1% LaNiAl-LDH (84.85%) was higher than NiAl-LDH (71.52%) within 90 min reaction. This difference can be attributed to the presence of La sites in 1% LaNiAl-LDH which act as electron-transfer mediators, leading to a significant improvement in the separation of photogenerated charge carriers. The effect of the addition of various scavengers was evaluated. Moreover, using the o-phenylenediamine (OPD), and photoluminescence (PL) analysis, the formation of ^•OH radicals was supported. The higher charge-transfer efficiency of 1% LaNiAl-LDH was confirmed by photoelectrochemical analysis. Furthermore, the reusability, stability, and degradation pathway of the as-synthesized nanocomposite were systematically examined. This work presents guidance for applying doped LDH-based materials in photocatalysis and promising applications in wastewater remediation.