Enhancing the photocatalytic elimination of acephate residues using Ni0 doped and diatomite-supported NiO: optimization, pathway, and toxicity

Abstract

NiO nanoparticles were synthesized and modified with Ni⁰ in the form of Ni/NiO blend and supported on a porous diatomite substrate, forming hybrid structures of NiO/D and Ni@NiO/D with enhanced photocatalytic performances. The obtained structures were applied for the effective oxidation of acephate pesticides under visible light. The obtained results demonstrated enhancement in the catalytic performance of Ni@NiO/D compared to NiO, Ni/NiO, and NiO/D structures. The full oxidation of AC (50 mg L⁻¹) was determined after 40 min using Ni@NiO/D at doses of 0.5 g L⁻¹. Moreover, the complete mineralization of AC molecules over Ni@NiO/D was detected after 70 min, considering the complete removal of TOC and the detection of essential inorganic anions (NO₃⁻ (7.6 × 10⁻⁵ mol L⁻¹), SO₄²⁻ (1.7 × 10⁻⁵ mol L⁻¹), and PO₄³⁻ (5.4 × 10⁻⁵ mol L⁻¹)). The oxidation pathway was illustrated by considering the estimated intermediates and the detection of hydroxyl radicals as main oxidizing species. The toxicity of untreated AC solutions and degraded intermediates was analyzed by assessing their inhibitory effect on Vibrio fischeri. Samples that underwent partial oxidation during their initial examination exhibited a greater degree of toxicity (65.3% inhibition) compared to AC. Nevertheless, a sample subjected to an 80 minute treatment exhibited neglected toxicity (1.4% inhibition). The combination of the diatomite substrate and Ni⁰ doping enhanced the adsorption and photocatalytic properties of NiO.