Photocatalytic Degradation of Toxic Phenolic Compound and Bacterial Inactivation by Ternary Li doped Zn_0.5Ni_0.5Fe₂O₄

Abstract

Conventional methods are inefficient to treat water contaminated with persistent organic contaminants. To decontaminate bacteria and 2,4,5‐trichlorophenol (TCP) contaminated water, a heterogeneous photocatalysis‐based advanced oxidation process was applied in this study. A Li‐doped ternary Zn0.5Ni0.5Fe2O4 (ZNF) photocatalyst (Li/ZNF) was synthesized via a facile co‐precipitation technique and characterized. The Li/ZNF has a sufficient specific surface area (69.8 m2.g−1), and an appropriate bandgap of 2.89 eV. Under optimal conditions, 10 mg of Li/ZNF photocatalyst degraded 80 % of 50 mg L−1 TCP in 6 h at pH 3 in the presence of 4 mM H2O2. After use, the Li/ZNF photocatalyst was magnetically separated and reused numerous times, with an efficiency of 66 % after the fifth reuse cycle. In the antibacterial time‐kill assay, 15 and 25 mg of Li/ZNF inhibited 1×107 CFU.mL−1 of S. Aureus and E. coli bacteria after 60 min of UV exposure, respectively.

Bismuth-based nanostructured photocatalysts for the remediation of antibiotics and organic dyes

“…Doping of Bi-based nanostructured materials: To improve the electrical, optical, and magnetic properties of the host materials, doping (rare earth elements, metal, or non-metal ions) is a common technique [ 20 , 72 , 104 , 110 , 144 – 150 ]. Doping reduces the bandgap energy, introduces intermediate energy levels to overcome constraints, creates trap sites to capture photogenerated charge carriers, and increases the absorption of visible light.…”

“…Additionally, after doping, oxygen vacancies or/and surface defects are created without destroying the crystal structure (though it might be distorted), effectively separating photogenerated carriers. Doping with metallic (Mg, Ag, Ni, Fe, Li, Co, and Ni) and non-metallic ions (F, C, N, and O), can introduce an intraband close to the conduction band of the host material, enhancing charge carrier dynamics [ 20 , 146 ].…”

“…However, it barely absorbs 4–5% of the ultraviolet light in the solar spectrum due to its broad bandgap of 3.2 eV, which limits the use of visible light. Because of this, the potential photocatalytic use of TiO 2 is constrained and the photocatalytic effectiveness is reduced [ 19 – 20 25 ]. Table 1 compares some of the salient characteristics of some of the bismuth-based photocatalysts with some of the typical metal oxide-based photocatalysts.…”

“…The term "photocatalysis" refers to chemical reactions that use light and a photocatalyst (basically a semiconductor). A few of the requirements that an effective photocatalyst system should satisfy include high sunlight absorption, an appropriate gap (1.5-2.8 eV), long-term charge carrier separation, high phototransporter mobility, appropriate physical and chemical properties, sufficient band alignment to meet the kinetic requirements of the target reaction, and anti-corrosion stability in reactive environments [18][19][20].…”

“…One of the main barriers preventing photocatalysis from being used in practical applications is the lack of suitable semiconductor photocatalysts. The commonly used nanometre-sized photocatalysts are metal oxides or sulfides (binary compounds: TiO 2 , CuO, CdS, MoO 3 ; ternary compounds: Bi 2 Mo 3 O 12 , ZnFe 2 O 4 ; quaternary compounds: Ni 0.5 Zn 0.5 Fe 2 O 4 , Bi 4 Nb x Ta 1−x O 8 I) [19][20][21][22][23][24][25][26]. Because of its distinct features, TiO 2 is the most extensively investigated photocatalytic semiconductor.…”