Search

With the growing concern of biofilm-associated infections and drug-resistant bacteria, an increasing interest in developing novel antibacterial agents is an urgent priority. Metal oxide-based polymeric materials are able to distinguish mammalian cells from bacterial cells and thus provide long-term antibacterial growth inhibition. Herein, we report the preparation of MgO, NiO and chitosan-coated metal oxide (CS–MO) nanocomposites via a simple in situ chemistry approach. Fourier transform infrared spectroscopy, X-ray diffraction patterns and X-ray photoelectron spectra results proved the formation of CS–MgO and CS–NiO nanocomposites. Also, the particle sizes were observed to be 18.3 and 25.5 nm for CS–NiO and CS–MgO, respectively. All the samples exhibited antibacterial activities against the Escherichia coli and Staphylococcus aureus strains; however, more effective against S. aureus compared to E. coli. Noticeably, 5 μg/mL CS–NiO comparatively exhibited highest bactericidal capability where E. coli and S. aureus viabilities were reduced to 25–47% after 12 h incubation. After treatment with 15 μg/mL of CS–NiO, ∼98% of S. aureus and 92.3% of E. coli cells were inhibited. [ABSTRACT FROM AUTHOR]

Sun-light driven CoO–CuFe2O4 photocatalyst was fabricated successfully from a layered double hydroxide via a modified co-precipitation and calcination method at 500°C, for the decontamination of azo dye-laden wastewater. The CoO–CuFe2O4 was characterized and the results demonstrated that it is composed of face-centered cubic CoO and cubic spinel CuFe2O4, which has a specific surface area and pore volume of 348.5 m² g–1 and 0.715 cm³ g–1, respectively; and pH point zero charges of 5.8. The photocatalytic activity is enhanced at acidic pH level and achieved ~99.4% decolorization of Eriochrome black T dye (EBT) within 90 min in the presence of 0.05 g of CoO–CuFe2O4. Notably, •OH and •O2− radicals played a role while h+ significantly participated during the EBT photodegradation. Reusability experiments confirm that the CoO–CuFe2O4 possesses high stability and exhibits efficient photocatalytic reusability with almost the same efficiency for degrading EBT dye. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Co–Fe LDH was used as precursor for the preparation of CoO–NiFe 2 O 4 mixed metal oxides catalyst. • CoO–NiFe 2 O 4 accomplished <94% decolorization of azo dye (EB) within 120 min. • Synergistic effects of CoO–NiFe 2 O 4 –photocatalyzed oxidation and Fenton-like reaction is established. • Decolorization efficiency significantly reduced to 19.8% in the alkaline conditions. • OH, O 2 – and photogenerated hole (h+) were responsible for the EB decolorization. Abstract Magnetic CoO–NiFe 2 O 4 catalyst was successfully fabricated from layered double hydroxide through a simple co-precipitation and calcination method, and for the first time applied as a novel Fenton-like catalyst for the decolorization of Eriochrome black T dye (EB). The characteristics results demonstrated that CoO–NiFe 2 O 4 exhibits a broad pore size distribution in the range of 5–40 nm, large specific surface area (363.6 m2 g–1) with the high structural stability and saturation magnetization (83.2 emu g–1), hence, can be easily recycled for five subsequent runs without significant activity loss. The catalytic activity of CoO–NiFe 2 O 4 was systematically evaluated under varying reaction conditions including initial pH, catalyst dosage, initial dye and H 2 O 2 concentrations. Under the optimal conditions, the CoO–NiFe 2 O 4 accomplished ∼87–97% decolorization of EB within 120 min. Here, the possible catalytic mechanism for EB decolorization is proposed and concluded to be multi-process induced by OH, O 2 − or h+ in the Fenton-like system. [ABSTRACT FROM AUTHOR]

Health concerns have been raised over the excessive occurrences of antibiotics such as tetracycline in aquatic environments. Adsorption is a simple and cheap technique for the removal of pharmaceuticals from industrial wastewater. To date, limited information exists on the fate, economical treatment and safe disposal of spent adsorbents in the environment, and this is often considered as the main drawback of adsorption. In this article, an alternative strategy to dispose and reuse spent inorganic adsorbents is proposed. We synthesized CoO/CuFe2O4 mixed metal oxide from layered double hydroxides by a modified co-precipitation and calcination method at 500 °C for 5 h. CoO/CuFe2O4 has a 348.5 m2/g surface area, pH point zero charge of 5.8 and an average pore diameter of 5.8 nm. Results show that the tetracycline removal efficiency at pH 6 reached 96.6% and 84-87.3% in the absence and in the presence of 4 g/L competing ions (Cl− and NO3−), respectively. Moreover, CoO/CuFe2O4 retained stable activities, of about 90%, over five consecutive recycling runs. Spent CoO/CuFe2O4 was reused as a catalyst in the presence of sunlight for degradation of azo dye, and this is the first report of achieving ~ 77% discolouration of eriochrome black T dye using a recycled adsorbent. [ABSTRACT FROM AUTHOR]

• Cost-competitive hybrid (MnFe-LDO–biochar) photocatalyst was successfully prepared. • MnFe-LDO–biochar has a bandgap of 2.85 eV and a high photocurrent response of 3.8 μA. • Large surface area containing mixed metal oxide oxidizing sites of MnFe-LDO–biochar improved its antibiotic degradation. • 50 mg MnFe-LDO–biochar/K 2 S 2 O 8 degraded ∼98 % tetracycline within 60 min upon exposure to a UV light. • MnFe-LDO–biochar performed sufficiently in a wide practical pH without significant leaching. A high-efficiency layered double oxide-biochar hybrid (MnFe-LDO–biochar) catalyst was successfully synthesized by the co-precipitation-calcination process and used to effectively remove tetracycline (TC) pollution. The characterization results verified that MnFe-LDO–biochar possesses a specific surface area of 524.8 m2 g−1, appropriate bandgap (2.85 eV), a high photocurrent response (3.8 μA cm–2), a saturation magnetization of 28.5 emu g−1 and a mixture of interconnected pores. 40 % of TC was removed after 30 min when 50 mL TC solution (20 mg L−1) was treated with 50 mg MnFe-LDO–biochar in the dark and reached ∼98 % degradation rate within 240 min upon exposure to a UV light. Notably, in the presence of H 2 O 2 or K 2 S 2 O 8 , the degradation rate of MnFe-LDO–biochar was shortened to 60 min with an average pseudo-first-order rate constant of 0.0445 min−1. The antibiotic removal rate of the cost-competitive MnFe-LDO–biochar surpassed several reported materials and maintained ∼80 % reuse efficiency after 3rd successive cycles. The TC photodegradation mechanism is multiprocess induced majorly by OH and SO 4 − while h+ and O 2 − contributed partly to the mineralization. This work highlights the powerful synergistic combination of layered double oxide (LDO) and biochar. [ABSTRACT FROM AUTHOR]