Enhanced photocatalytic and antibacterial activities of RGO/LiFe5O8 nanocomposites

Ciprofloxacin antibiotic removal from aqueous solutions by ZnO nanoparticles coated on ACA: modeling and optimization

Antibiotics are one of the most widely used drug groups. The presence of antibiotics in urban water sources and sewage creates many environmental and medical risks for humans and other living organisms. In this study, the potential of zinc oxide (ZnO) coated on almond shell activated carbon (ACA-ZnO) in removing ciprofloxacin (CIP) from aqueous solutions was investigated. Almond shell was used to make activated carbon. Zinc oxide nanoparticles were prepared by the sol-gel method, and finally, ZnO nanoparticles were bonded to activated carbon. The effect of independent parameters pH, contact time, adsorbent dose, and initial CIP concentration on CIP removal efficiency using ACA-ZnO was investigated by response surface methodology. Optimal removal was obtained at pH = 5.4, CIP initial concentration = 7.4 mg/L, adsorbent dose = 0.82 g/L, and reaction time = 67.3 min. This study followed a quadratic model (R2 = 0.958). The best model of adsorption isotherm fits with the Freundlich model (R2 = 0.9972) and the maximum capacity was 251.42 mg/g adsorption kinetics, and pseudo-second-order kinetic model (R2 = 0.959). The results of this study showed that ACA-ZnO as an adsorbent is very efficient, without environmental side effect and cost-benefit.

Titanium doped cobalt ferrite fabricated graphene oxide nanocomposite for efficient photocatalytic and antibacterial activities

Dyes and microbes are the main sources of water pollution and their treatment with titanium doped cobalt ferrite nanoparticles (CoTixFe2-xO4 NPs) is highly challenging due to the recombination ability of their electron-hole pairs which could be mitigated by making their composite with graphene oxide (GO). In the present study, titanium doped cobalt ferrite was fabricated on GO (CoTi0.2Fe1.8O4/GO NC) via the facile ultrasonication method and its confirmation was done by various analytical studies. Homogeneous dispersion of spherical CoTi0.2Fe1.8O4 NPs on the GO surface was realized by SEM analysis. Excellent crystallinity was corroborated by XRD while a Zeta Potential value -21.52 mV depicted exceptional stability. The photocatalytic power of CoTi0.2Fe1.8O/GO NC against Congo Red (CR) dye showed 91% degradation efficiency after 120 min visible light irradiation under optimum conditions of pH 9 and dye concentration 1 mg L-1 which was reasonably higher as compared to bare CoTi0.2Fe1.8O NPs (78% degradation efficiency). The improved photocatalytic performance is accredited to its narrow bandgap value (1.07 eV) and enhanced charge separation as indicated by the Tauc plot and Photoluminescence analysis, respectively. Additionally, CoTi0.2Fe1.8O/GO NC could be readily regenerated and reused five times with only ∼2% performance loss. Meanwhile, MICs of CoTi0.2Fe1.8O4/GO NC against P. aeruginosa and S. aureus were 0.046 and 0.093 mg mL-1 while MBCs were 0.093 and 0.187 mg mL-1, respectively. Thereby, optimized NC can open new avenues for the degradation of dyes from polluted water besides acting as a promising antimicrobial agent by rupturing the cell walls of pathogens.

Visible light-driven ZnO/Fe3O4 magnetic nanoparticles for detoxification of diazinon: the photocatalytic optimization process with RSM-BBD model

Today, diazinon is one of the most widely used organophosphorus pesticides, whose widespread use can cause many ecological and biological risks. In this research, a magnetic ZnO/Fe3O4 nanoparticle was used to investigate the photocatalytic degradation of diazinon. Sol-gel synthesis was used to create the nanoparticle, which was then characterized using XRD, FTIR, FESEM, VSM, and XPS techniques. The design of photocatalytic degradation experiments was done using the response surface method and the Box-Behnken design model. The investigated parameters include pH, nanoparticle concentration, diazinon concentration, and irradiation time. The characterization of the ZnO/Fe3O4 nanoparticle showed well-formed crystalline phases and a cubic spinel structure. Additionally, the shape of the nanoparticle is almost uniform and spherical. The FT-IR spectrum also confirmed the presence of all functional groups related to ZnO and Fe3O4 in the ZnO/Fe3O4 nanoparticles structure. The synthesized nanocomposite has superparamagnetic properties and a very small coercive field, making it easily recyclable, according to a VSM analysis. XPS results also showed the presence of Fe (Fe 2p1/2 and Fe 2p3/2), Zn (Zn 2p1/2 and Zn 2p3/2), oxygen (O1s), and weak carbon (C1s) peaks in the ZnO/Fe3O4 structure. The results of the photocatalytic optimization experiments showed that the highest efficiency of diazinon toxin degradation is 99.3% under the conditions of pH 7, diazinon initial concentration of 10 mg/L, nanoparticle concentration of 1 g/L, and a contact time of 90 min. This result is very close to the BBD model's predicted removal efficiency under optimal conditions (100%). As a result, the ZnO/Fe3O4 nanocomposite can produce active free radicals through UV radiation, and these radicals can successfully remove diazinon under actual conditions.

Sunlight powered degradation of pentoxifylline Cs0.5Li0.5FeO2 as a green reusable photocatalyst: Mechanism, kinetics and toxicity studies

The degradation of Pentoxifylline (PXF) was achieved successfully by green energy in a built-in solar photocatalytic system using hybrid LiCs ferrites (Li_0.5Cs_0.5FeO₂) as magnetically recoverable photocatalysts. Kinetics showed a first-order reaction rate with maximum PXF removal of 94.91% at mildly acidic pH; additionally, the ferromagnetic properties of catalyst allowed recovery and reuse multiple times, reducing costs and time in degradation processes. The degradation products were identified by HPLC-MS and allowed us to propose a thermodynamically feasible mechanism that was validated through DFT calculations. Additionally, toxicity studies have been performed in bacteria and yeast where high loadings of Cs showed to be harmful to Staphylococcus aureus (MIC≥ 4.0 mg/mL); Salmonella typhi (MIC≥ 8.0 mg/mL) and Candida albicans (MIC≥ 10.0 mg/mL). The presented setup shows effectiveness and robustness in a degradation process using alternative energy sources for the elimination of non-biodegradable pollutants.

Formation mechanism, degradation behavior, and cytocompatibility of a double-layered structural MAO/rGO-CaP coating on AZ31 Mg

Microarc oxidation coated magnesium attracts increasing attention recently, owing to its excellent anti-corrosion and wear-resistance properties. However, some drawbacks like micropores on the MAO surface reduce the corrosion resistance of the coatings, which requires post treatment. In the present work, a specific double layered structural MAO/rGO-CaP coating was produced to seal the micropores on the MAO coating and further enhance the corrosion resistance. The structure, cytocompatibility, electrochemical properties, and long-term corrosion behavior of the composite coatings were investigated. XRD results show that the coatings are mainly composed of CaHPO₄ (DCP) and Ca₅(PO₄)₃OH (HA). Cytocompatibility evaluation indicates that the rGO in the coating shows no cytotoxicity. Corrosion potential of the bottom MAO coating is enhanced significantly by the rGO-CaP top coatings from -1.58 V to -1.02 V. Long term soaking test reveals that a longer chemical stable coating was produced. The results suggest a potential application of the MAO/rGO-CaP coating in practice.