Yongqing Zhang

Degradation of aniline with zero-valent iron as an activator of persulfate in aqueous solution

Zero valent iron (ZVI) can activate persulfate to generate sulfate free radicals which are a strong oxidant to degrade organic pollutants. The oxidative degradation of aniline in aqueous solution by persulfate activated with zero valent iron was studied under laboratory conditions. Batch experiments were conducted to investigate the effects of different parameters such as pH, ZVI concentration, aniline concentration, persulfate concentration and reaction temperature on aniline degradation. The results showed that aniline degradation increased with increasing temperature. The optimum dosage of ZVI was 0.4 g L−1 and 85% aniline degradation was observed. Maximum aniline degradation was observed at pH 4.0, whereas at pH above or below 4.0, aniline degradation efficiency was decreased. In the persulfate-ZVI system, the apparent energy of activation for aniline degradation was 14.85 kJ mol−1. The existence of persulfate radicals and hydroxyl radicals produced during the degradation of aniline were identified with scavenger ethanol and tert-butyl alcohol. The reaction intermediates nitrobenzene, nitroso-benzene and p-benzoquinone were detected by gas chromatography-mass spectrometry and based on these intermediates obtained a probable pathway for aniline degradation has been proposed.

Microbial removal of NOX at high temperature by a novel aerobic strain Chelatococcus daeguensis TAD1 in a biotrickling filter.

The removal of NO(X) at high temperature by Chelatococcus daeguensis TAD1 in a biotrickling filter was studied. Media components of the recycling liquid were screened using Plackett-Burman design and then were optimized using response surface methodology, which enhanced the efficiency of nitrate removal by TAD1. The optimal medium was used to perform long-term experiments of NO(X) removal in a biotrickling filter under high concentrations of O(2) and NO in simulated flue gas. Results showed that the biotrickling filter was able to consistently remove 80.2-92.3% NO(X) when the inlet NO concentration was 600ppm under the conditions of oxygen concentration ranging between 2% and 20% and empty bed residence time (EBRT) being 112.5s. Analyses by polymerase chain reaction and denaturing gradient gel electrophoresis (PCR-DGGE) indicated that TAD1 was always predominant in the biofilm under a flue gas environment. Overall, the present study demonstrated that utilizing a biotrickling filter inoculated with the aerobic denitrifier TAD1 to remove NO(X) at high temperature was practically feasible.

Hydrothermal Preparation and Characterization of TiO2/BiVO4 Composite Catalyst and its Photolysis of Water to Produce Hydrogen

In the present work, bismuth vanadate composited photocatalysts were synthesized and characterized. X‐ray diffractometry and Raman results showed that the particles were well crystallized, and formed by the complex of monoclinic BiVO4 and TiO2. On electron microscopy, the photocatalyst exhibited high crystallization, agglutination and irregular shape, and was surrounded by numerous TiO2 particles. The study of surface areas showed that the specific surface area of 30‐BiVO4/TiO2 composited was 112 m2·g−1, which was nearly 10 times that of pure BiVO4. The ultraviolet–visible diffuse reflectance spectra indicated the composited photocatalyst were activated in visible light. The activity of photocatalytic water splitting was studied. The results showed that monomer BiVO4 photocatalyst was not able to produce hydrogen under any light source. BiVO4/TiO2 composited photocatalysts, however, were capable of generating hydrogen. Under UV light irradiation for 120 min, 1 g catalyst dispersed in 50 mL deionized water produced almost 1 mL hydrogen, such that the productivity of hydrogen was higher than that of P25‐TiO2. Photocatalytic decomposition of water under visible light also confirmed that the BiVO4/TiO2 composited photocatalyst had the ability of water splitting.

Electron transfer of Pseudomonas aeruginosa CP1 in electrochemical reduction of nitric oxide

This study reports catalytic electro-chemical reduction of nitric oxide (NO) enhanced by Pseudomonas aeruginosa strain CP1. The current generated in the presence of bacteria was 4.36times that in the absence of the bacteria. The strain was able to catalyze electro-chemical reduction of NO via indirect electron transfer with an electrode, revealed by a series of cyclic voltammetry experiments. Soluble electron shuttles secreted into solution by live bacteria were responsible for the catalytic effects. The enhancement of NO reduction was also confirmed by detection of nitrous oxide; the level of this intermediate was 46.4% higher in the presence of bacteria than in controls, illustrated that the electron transfer pathway did not directly reduce nitric oxide to N2. The findings of this study may offer a new model for bioelectrochemical research in the field of NO removal by biocatalysts.

Degradation of p-chloroaniline by FeO3−xH3−2x/Fe0 in the presence of persulfate in aqueous solution

Sulfate radical based advanced oxidation processes are promising techniques for the removal of organic compounds in aqueous solutions. In this study, FeO3−xH3−2x/Fe0 catalyst was prepared and used to activate persulfate (S2O82−) for the degradation of p-chloroaniline (PCA). The results showed that nearly complete degradation of PCA was observed within 1 h in the persulfate-FeO3−xH3−2x/Fe0 system under the following optimized reaction conditions: PCA concentration 0.05 mM, FeO3−xH3−2x/Fe0 1 g L−1, persulfate 2.5 mM and pH 7.0. The PCA degradation was higher under acidic conditions when compared to alkaline conditions. A complete removal of the added PCA (0.05 mM) was achieved within 5 min with the addition of 2.5 mM persulfate and 1 g L−1 FeO3−xH3−2x/Fe0 at pH 3.0. FeO3−xH3−2x/Fe0 catalyst was prepared by the calcination of Fe0 at 200 °C. The morphology of the catalyst was investigated with X-ray diffraction patterns (XRD), Scanning electron microscopy (SEM) and Fourier transform infrared spectra (FTIR). The results demonstrated that the catalyst surface was mainly composed of hematite γ-Fe2O3 and goethite (α-FeOOH).

Photocatalytic Degradation of 2,4-Dichlorophenol Using Nanosized Na2Ti6O13/TiO2 Heterostructure Particles

Na2Ti6O13/TiO2 composite particles were synthesized through the hydrolyzation of tetrabutyl titanate in a reverse microemulsion and characterized by thermogravimetry and differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), and scanning electron microscope (SEM). The photocatalytic property of Na2Ti6O13/TiO2 was evaluated by degradation of 2,4-dichlorophenol(2,4-DCP) under 40 W ultraviolet lamp ( nm) irradiation and compared with commercial P25-TiO2 in the same condition. The results showed that the synthesized nanobelts Na2Ti6O13/TiO2 heterostructures had typical width from 80 to 100 nm, with thickness less than 40 nm and length up to 5 μm. Such Na2Ti6O13/TiO2 nanosized particles exhibited better photocatalytic activity than that of P25-TiO2, and the degradation rate of 2,4-DCP with initial concentration of 0.02 g/L reached 99.4% at the end of 50 min.

Degradation of 2,4,6-trichlorophenol and determination of bacterial community structure by micro-electrical stimulation with or without external organic carbon source

This study aimed to investigate the degradation efficiency of 2,4,6-trichlorophenol through a batch of potentiostatic experiments (0.2 V vs. Ag/AgCl). Efficiencies in the presence and absence of acetate and glucose were compared through open-circuit reference experiments. Significant differences in degradation efficiency were observed in six reactors. The highest and lowest degradation efficiencies were observed in the closed-circuit reactor fed with glucose and in the open-circuit reactor, respectively. This finding was due to the enhanced bacterial metabolism caused by the application of micro-electrical field and degradable organics as co-substrates. The different treatment efficiencies were also caused by the distinct bacterial communities. The composition of bacterial community was affected by adding different organics as co-substrates. At the phylum level, the most dominant bacteria in the reactor with the added acetate and glucose were Proteobacteria and Firmicutes, respectively.

Adsorption of Ammonium in Aqueous Solutions by the Modified Biochar and its Application as an Effective N-Fertilizer

Water body contamination by ammonium is of major concern because it poses huge risks and harm to the environment and human health. Biochar derived from waste spruce sawdust was modified by soaking it into HNO3 and Na2CO3 to obtain a low-cost and high-efficiency adsorbent. The factors affecting the removal of ammonium from aqueous solutions, the mechanisms by which ammonium was adsorbed by the modified biochar, and the potential application of the post-adsorption biochar as an effective N-fertilizer were studied. pH and co-existing ions were affirmed to affect the capacity of the modified biochar to adsorb ammonium. The pseudo-second order kinetic model and Freundlich model could best fit the ammonium adsorption data. Cation exchange was the most important mechanism involved in ammonium adsorption by the modified biochar. The high adsorption capacity of the modified biochar makes it a promising alternative adsorbent to remove ammonium from wastewater. Furthermore, the seedling bioassay experiment demonstrated that the post-adsorption biochar can be cycled back directly to the soil as an effective N-fertilizer.

In situ preparation of highly stable polyaniline/W 18 O 49 hybrid nanocomposite as efficient visible light photocatalyst for aqueous Cr(VI) reduction

In the present study, we prepared novel polyaniline supported W18O49 (PANI/W18O49) nanocomposite by in situ oxidative polymerisation method. We herein focused on enhancing the stability and the photocatalytic performance of W18O49. The prepared PANI/W18O49 was thoroughly characterized by FTIR, TEM, XRD, BET, UV-vis DRS and PL. The PANI support presented a great effect on the light harvesting and photo-charge transfer of the W18O49, and the optimum percentage of was found to be 10 wt%. As for treating Cr(VI), the effect of important water quality parameters (such as pH, ions, NOM, DO, temperature and SOAs) on photocatalytic performance was investigated under the visible light irradiation (λ > 420 nm). SOAs were shown to exert a dramatic accelerating influence on Cr(VI) reduction in the system. The obtained 10%-PANI/W18O49 can completely catalytically reduce 1 mM Cr(VI) in the presence of tartaric acid (1:3) within 50 min. Meanwhile, it can be recycled at ten times without any loss of photocatalytic efficiency, indicating the high stability of the as-prepared photocatalyst. The results of the study demonstrate the potential of the new obtained photocatalyst in efficient utilization of solar energy for treating aqueous Cr(VI).

Comparison of Biological Aerobic and Anaerobic Carbon, Sulfur and Nitrogen Removal

Nitrogen Removal Saima Fazal1,2, Shaobin Huang1,2*, Hao Xu1,2, Yongqing Zhang1,2, Waseem Hayat1,2, Xiaodong Du1,2, Fazal Raziq3, Liang Qiao3 and Zahid Ullah4 1School of Environment and Energy, South China University of Science and Technology, Guanzhou, PR China 2Guangdong Ecological Environment Control Engineering Technology Research Center, China 3School of Physics, University of Electronic Science and Technology of China, Chengdu, 610054, China 4Department of Environmental Sciences, Allama Iqbal Open University, Islamabad, Pakistan