Shaobin Huang

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.

Experimental and modeling study on nitric oxide removal in a biotrickling filter using Chelatococcus daeguensis under thermophilic condition

In this study, the development of a thermophilic biotrickling filter (BTF) system to inoculate a newly isolated strain of Chelatococcus daeguensis TAD1 for the effective treatment of nitric oxide (NO) is described. It was successfully started up in 35days and effectively removed NO from the oxygen contained simulated gas at 50°C. A mathematical model based on the mass transfer in gas-biofilm interface and chemical oxidation in gas phase was developed. Steady-state experimental data under different inlet NO concentration and empty bed retention time (EBRT) condition were used to verify the proposed model. The model can well reproduce the experimental results and the sensitivity analysis demonstrates that the model is not dependent on the accuracy of the parameters excessively.

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.

Microbial fuel cell-based biosensor for toxic carbon monoxide monitoring

This study presents an innovative microbial fuel cell-based biosensor for carbon monoxide (CO) monitoring. The hypothesis for the function of the biosensor is that CO inhibits bacterial activity in the anode and thereby reduces electricity production. A mature electrochemically active biofilm on the anode was exposed to CO gas at varied concentrations. A proportional linear relationship (R2 = 0.987) between CO concentration and voltage drop (0.8 to 24 mV) in the range of 10% and 70% of CO concentration was observed. Notably, no further decrease of voltage output was observed by with further increasing CO concentration over 70%. Besides, the response time of the biosensor was 1 h. The compact design and simple operation of the biosensor makes it easy to be integrated in existing CO-based industrial facilities either as a forewarning sensor for CO toxicity or even as an individual on-line monitoring device.

Synthesis and Performance of Iron Oxide-Coated Ceramsite in a Biotrickling Filter for Nitric Oxide Removal under Thermophilic Conditions

A novel medium consisting of iron oxide-coated porous ceramsite (modified ceramsite) was investigated for NO removal under thermophilic conditions in this study. We used a surface coating method with FeCl3·6H2O as the modifier. When ceramsite was calcined for 4 h at 500 °C, the surface pH value decreased to 3.46, which is much lower than the isoelectric point of ceramsite, ensuring its surface was electropositive. The surface of modified ceramsite changed from two- to three-dimensional and exhibited excellent adsorption behavior to assist microbial growth; the maximum dry weight of the biofilm was 1.28 mg/g. It only took 8 days for the biofilter constructed from the modified ceramsite to start up, whereas that packed with commercial ceramsite took 22 days. The NO removal efficiency of the biofilter did not decrease apparently at high NO inlet concentration of above 1600 mg/m3 and maintained an average value of above 90% during the whole operation period. Additionally, the morphological observation showed that the loss of the surface coating was not obvious, and the coating properties remained stable during long-term operation. The maximum NO inlet loading of the biotrickling filter was 80 g/(m3·h) with an average removal efficiency of 91.1% along with a quick start-up when using the modified ceramsite filler. Thus, modified ceramsite can be considered a very effective medium in biotrickling filters for NO removal.