Yean Ling Pang

Synthesis, characteristics and sonocatalytic activities of calcined γ-Fe2O3 and TiO2 nanotubes/γ-Fe2O3 magnetic catalysts in the degradation of Orange G

In this work, γ-Fe2O3 and TiO2 NTs/γ-Fe2O3 composites with good magnetism and sonocatalytic activity were prepared by a facile polyol method and utilize the principle of isoelectric point method, respectively. The structural and magnetic features of the prepared calcined γ-Fe2O3 and composite catalysts were investigated by transmission electron microscopy (TEM), powder X-ray diffraction (XRD), surface analysis, UV-Vis diffuse reflectance spectra (UV-Vis DRS), vibrating sample magnetometry (VSM) and zeta potential analysis. The effects of calcination temperature on γ-Fe2O3 phase variation, physical properties and sonocatalytic properties were investigated. The porosity, specific surface area, band gap energy and sonocatalytic activity of γ-Fe2O3 were gradually decreased with calcination temperature increased. TiO2 NTs/γ-Fe2O3 with appropriate composition and specific structural features possess synergetic effects such as efficient separation of charge carriers and hydroxyl radicals produced by heterogeneous fenton and fenton-like reactions. This enhanced the sonocatalytic activity for the degradation of Orange G under ultrasonic irradiation. The sonocatalytic reactions obeyed pseudo first-order kinetics. All these information provide insight into the design and development of high-efficiency catalyst for wastewater treatment.

A comprehensive review on state-of-the-art photo-, sono-, and sonophotocatalytic treatments to degrade emerging contaminants

Emerging contaminants (ECs) are commonly originated from personal care products, cosmetics, pharmaceuticals, pesticides, dioxins, polycyclic aromatic hydrocarbons (PAHs), and alkylphenolic compounds. Due to the huge development of these industries, these ECs have been constantly detected in wastewater, groundwater, and surface water in hazardous quantity. The discharge of these ECs into the environment causes considerable non-esthetic pollution and could be a great threat to the entire ecosystem. The common wastewater treatment plants (WWTPs) which consist of biological, physical, and chemical treatments such as activated sludge, filtration, adsorption, and coagulation are found to be ineffective for desired removal of ECs. In turn, various emerging advanced oxidation processes (AOPs) such as ultrasonic and ultraviolet irradiation with or without the presence of catalyst have raised great attention due to their great potential in remediation of ECs. This paper presents a critical review on types, recent occurrence, sources, environmental impacts, and emerging treatment methods applicable to treat ECs. The current research and applications of ultrasonic, ultraviolet, and combination of both irradiations to treat ECs in wastewater are particularly reviewed. The effect of key parameters on photo-, sono- and, sonophotocatalytic degradation of ECs are commendably accessed such as ultrasonic power, ultrasonic frequency, light intensity, ultraviolet wavelength, solution pH, oxidizing agents, chemical additives, catalyst dosage, and modification of catalyst. The possible reaction mechanisms of ECs degradation process and kinetic model study are also elucidated in detail. Lastly, future research directions and conclusions are proposed to strengthen the understanding on their fate in water. All this information is vital to predict the negative impacts of ECs on the receiving environment effectively.

In situ reactive extraction of Jatropha curcas L. seeds assisted by ultrasound: Preliminary studies

ABSTRACT Esterification is required to reduce the high free fatty acid (FFA) content of crude Jatropha oil to below 3% prior to transesterification. In this study, raw decorticated Jatropha seeds were employed as the feedstock in in situ reactive extraction assisted by ultrasound in the presence of sulfuric acid (H2SO4) as a catalyst. Extraction efficiency, esterification efficiency, and fatty acid methyl ester (FAME) yield were optimized as a function of ultrasonic pulse mode, amplitude, and H2SO4 amount. The optimum extraction efficiency of 83.96%, esterification efficiency of 71.10%, and FAME yield of 38.58% were achieved at a pulse mode of 5 s on/2 s off, an ultrasonic amplitude of 60%, and an H2SO4 amount of 5 mL in reaction time of 150 min.

Sonocatalytic degradation of Rhodamine B in the presence of iron-doped TiO2 nanotubes: Characterizations and reaction kinetic studies

Fe-doped titanium dioxide nanotubes (TiO2 NTs) were synthesized through hydrothermal synthesis technique. The influences of iron doping on the microstructures, phase composition and optical properties of Fe-TiO2 were analyzed by the methods of transmission electron microscopy (TEM), X-ray diffraction (XRD) and nitrogen adsorption-desorption. The results showed that Fe3+ was successfully introduced into the nanotubes. Fe3+ doping could significantly enhance the sonocatalytic activity of TiO2 due to higher specific surface area and more active surface oxygen vacancies. Two kinetic models that were Langmuir-Hinshelwood (L-H) mechanism and apparent first-order reactions were proposed. It was found that the reactions were fitted to the latter kinetic model as L-H model may not be valid when the reaction intermediates effects prevail. The apparent first-order reaction rate constants of the degradation of catalyzed reaction were higher than that obtained without catalyst. The calculated activation energy value f...