Visible light responsive photocatalytic degradation of pharmaceuticals using La-NiAl-LDH/2D hematene composite: Synergistic effects and mechanistic insights

Organic pollutants in water and wastewater have become a significant environmental issue. The photocatalytic process is a key and cost-effective method within advanced oxidation processes (AOPs) used for water treatment. In this study, we synthesized a 1 % La-NiAl layered double hydroxide (LDH) modified ball-milled hematene (BM-Hm) composite (La-LDH/BM-Hm) as an efficient photocatalyst through a simple co-precipitation-hydrothermal method. X-ray diffraction (XRD) analysis confirmed the successful crystal structure of the La-LDH/BM-Hm composite. Moreover, the morphology of the photocatalyst was assessed by SEM and HRTEM, revealing that La-LDH formed a cohesive composite with hematene nanosheets. The composite exhibited a reduced band gap (2.06 eV) and enhanced charge separation efficiency, as confirmed by UV–Vis DRS and photoelectrochemical analyses. Under optimal conditions, the photocatalytic decomposition efficiency of La-LDH/BM-Hm reached 89.17 % within 120 min. The remarkable synergy within the composite was quantitatively confirmed by a synergy factor (SF) of 7.1, indicating the role of the heterojunction interface, thereby improving photocatalytic performance. The formation of ^•OH radicals was investigated through o-phenylenediamine (OPD) and photoluminescence (PL) analyses. The charge-transfer efficiency of La-LDH/BM-Hm was assessed via photoelectrochemical analysis, and element leaching was quantified after four cycles. The energy consumption for the different concentrations of RIF was calculated, and the results confirmed that the suggested treatment is energy-efficient. Intermediates of RIF generated during the photocatalytic process and their toxicities were analyzed. This research proposes the La-LDH/BM-Hm composite as an effective catalyst for photocatalytic water treatment.