Zhong-Ting Hu

A novel quasi-cubic CuFe2O4–Fe2O3 catalyst prepared at low temperature for enhanced oxidation of bisphenol A via peroxymonosulfate activation

A facile eco-friendly co-precipitation synthesis at low temperature was employed to fabricate CuFe2O4–Fe2O3 for the oxidation of bisphenol A (BPA) via peroxymonosulfate (PMS) activation. The formation mechanism of CuFe2O4–Fe2O3 at low temperature is proposed. The FESEM and BET characterization studies revealed that the CuFe2O4–Fe2O3 catalyst has a quasi-cubic morphology and specific surface area of 63 m2 g−1. The performance of CuFe2O4–Fe2O3 as a PMS activator was compared with those of other catalysts and the results indicated that the performance was in the following order: CuFe2O4–Fe2O3 > CuFe2O4 > CoFe2O4 > CuBi2O4 > CuAl2O4 > Fe2O3 > MnFe2O4. A kinetic model with mechanistic consideration of the influence of pH, PMS dosage and catalyst loading was developed to model the degradation of BPA. The intrinsic rate constant (ki) was obtained from the kinetic study. The relationship between the pseudo first-order rate constant and ki was established. The trend of ki revealed that increasing the catalyst loading decreased the BPA removal rate due to the initial preferential production of the weaker radical (i.e. SO5˙−) for BPA degradation and Fe2+ quenching of SO4˙− at higher catalyst loading. The influence of water matrix species (i.e. Cl−, NO3−, HCO3−, PO43− and humic acid) on the BPA degradation rate was also investigated. The CuFe2O4–Fe2O3 catalyst exhibited excellent stability and can be reused several times without significant deterioration in performance.

Facile room-temperature synthesis of carboxylated graphene oxide-copper sulfide nanocomposite with high photodegradation and disinfection activities under solar light irradiation

Carboxylic acid functionalized graphene oxide-copper (II) sulfide nanoparticle composite (GO-COOH-CuS) was prepared from carboxylated graphene oxide and copper precursor in dimethyl sulfoxide (DMSO) by a facile synthesis process at room temperature. The high-effective combination, the interaction between GO-COOH sheets and CuS nanoparticles, and the enhanced visible light absorption were confirmed by transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermo gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectra (DRS) and Photoluminescence (PL) spectra. The as-synthesized GO-COOH-CuS nanocomposite exhibited excellent photocatalytic degradation performance of phenol and rhodamine B, high antibacterial activity toward E. coli and B. subtilis, and good recovery and reusability. The influence of CuS content, the synergistic reaction between CuS and GO-COOH, and the charge-transfer mechanism were systematically investigated. The facile and low-energy synthesis process combined with the excellent degradation and antibacterial performance signify that the GO-COOH-CuS has a great potential for water treatment application.

Single-crystalline Bi2Fe4O9 synthesized by low-temperature co-precipitation: performance as photo- and Fenton catalysts

Multi-functional, self-assembled mullite bismuth ferrites (Bi2Fe4O9) have been synthesized by a facile co-precipitation method at a low temperature of 95 °C. The Bi/Fe precursor molar ratio and the reaction time were investigated for their influences on the resulting Bi2Fe4O9 nanopads. The Bi2Fe4O9 nanopads were formed via self-assembled crystal growth along the (001) plane, with an average thickness of 170 nm. The most well crystalline nanopads were produced at a reaction time of 36 h, beyond which the nanopads started to dissolve. The produced pure Bi2Fe4O9 nanopads exhibit a high degree of elemental stoichiometry with uniform elemental distribution. The Bi2Fe4O9 exhibits double bandgaps of 1.9 and 2.3 eV, and shows surface area of 5.8 m2 g−1. It can be photoexcited by visible light of up to 656 nm. The Bi2Fe4O9 can be used as a photocatalyst and Fenton catalyst. Its catalytic activities were evaluated using bisphenol A (BPA) as the model pollutant. Under visible-light irradiation from a solar simulator, 34% of BPA could be removed (compared to only ∼3% with Evonik P25) via visible-light photocatalysis. With addition of H2O2 (16 mM), 54% and 73% of BPA could be removed within 1 h via dark Fenton-like and visible-light photo-Fenton reactions, respectively. The Bi2Fe4O9 also exhibits a weak magnetism of 0.99 emu g−1. The multi-functional Bi2Fe4O9 nanopad has the potential to be used for continuous solar catalytic treatment of wastewater over an alternating day/night cycle and is recoverable via magnetically-enhanced gravity separation.

Nanostructured hexahedron of bismuth ferrite clusters: delicate synthesis processes and an efficient multiplex catalyst for organic pollutant degradation

A novel bismuth ferrite, with the simultaneous formation of nanostructured clusters and controllable morphologies, was fabricated using a delicate synthesis process. By carefully controlling all processes from co-precipitation at a low temperature in water to hydrothermal treatment in methanol/water co-solvent system, nanostructured bismuth ferrite clusters with controllable morphologies composed of small bismuth ferrite crystals (∼25 nm) could be obtained. The fast crystal growth of the bismuth ferrites has been successfully hindered and a relatively pure mullite (Bi2Fe4O9) structure of the nanostructured bismuth ferrite clusters could be obtained. Their morphologies could be cube-, cuboid- and plate-like shapes with a side length of ∼400 nm, a height of ∼600 nm and a thickness of ∼80 nm. The resulting nanostructured bismuth ferrite clusters show good crystallinity, uniform elemental distributions, high chemical stability, good dispersity, reusability, and a narrow bandgap of ∼2.1 eV. They have remarkable multiplex catalytic activities in the degradation of methyl orange (MO) through visible-light photo-Fenton oxidation, dark Fenton-like reaction and solar photocatalysis. Under visible-light illumination, 99% of MO could be removed in 80 min. Without illumination, 96% of MO could be removed in 4 h. A plausible mechanism of the multiplex catalytic activities is proposed.

Controllable mullite bismuth ferrite micro/nanostructures with multifarious catalytic activities for switchable/hybrid catalytic degradation processes

In this work, controllable preparation of micro/nanostructured bismuth ferrites (BFOs) were used to investigate multifarious heterogeneous catalyses, including Fenton/Fenton-like reaction, photocatalysis, photo-Fenton oxidation, and peroxymonosulfate (PMS) activation. Results showed that BFO can be used asa novel catalyst to activate switchable catalytic degradation of organic matters. Additionally, a novel catalytic system for degradation of organic pollutants, which integrating all-above heterogeneous catalyses is denoted as BFO/H2O2/PMS hybrid reaction, is introduced for the first time. BFO/H2O2/PMS system effectively degraded>99% for both methyl orange (MO) and sulfamethoxazole (SMX) within 60min, which shows better efficiency than above BFO-driven catalyses. The major SMX degradation pathway in BFO/H2O2/PMS system is proposed via detecting intermediates using LC/MS/MS. It was found that catalytic activities of BFOs are in the order of BFO-L (co-precipitation, micro/nanosize, single crystals exposing facet (001))>BFO-H (hydrothermal, nanocluster with a higher surface area than other BFOs)>BFO-C (fabricated using calcination process, microsize), which demonstrated that crystallographic orientation is more significant in heterogeneous catalyses than specific surface area at micro/nanoscale. Besides, the required H2O2 consumption for achieving 99% TOC removal was identified in BFO-driven photo-Fenton oxidation. The other effects on degradation efficiency, such as H2O2 dosage and pH, were investigated as well. In Fenton/Fenton-like reaction, reaction conditions suggested are ∼61.5mM H2O2 dosage and pH≥4.5 to avoid quenching of HO into HO2 by excessive H2O2 and Fe leaching.

Supermagnetic recyclable Bi/Fe-based nanomaterial with multiple functionalities and its potential practical application in environmental decontamination

O and inorganic compounds have been widely used as corrosion inhibitors in metal or metallic-alloys. Research has shown that some of the compounds used are toxic and harmful to human health and the environment. Therefore, green chemicals are used as a substitute for the toxic chemicals. In this research, adsorption and thermodynamics of corrosion inhibition on mild steel has been carried out in Citric acid and Formic Acid solutions using Tamarindus indica. The inhibitive properties of ethanolic extracts of Tamarindus indica on mild steel in Formic and Citric acid solutions were investigated using the weight loss techniques. Mild steel was immersed in three different concentrations of the two acids (formic and citric acid) in blank, 0.1 g/100 ml and 0.3 g/100 ml concentrations of the extract. All these three different concentrations were studied within the temperatures of 30oC and 45oC. The results obtained illustrate that the inhibition efficiency increases with increase in concentration and temperature. Increase in inhibition efficiency with increase in temperature suggests the mechanism to be chemisorption. The optimum inhibition efficiency was 78.3 in 3 g/100 ml of citric acid at 45oC (318K). The heat of absorption was found to be positive, hence endothermic. Adsorption studies were carried out using Temkin, FloryHuggins, and Langmuir isotherms. From the results obtained, the data fits the Langmuir adsorption isotherm.