Yalei Zhang

Fe2O3-Pillared Rectorite as an Efficient and Stable Fenton-Like Heterogeneous Catalyst for Photodegradation of Organic Contaminants

An efficient Fe(2)O(3)-pillared rectorite (Fe-R) clay was successfully developed as a heterogeneous catalyst for photo-Fenton degradation of organic contaminants. X-ray diffraction analysis and high-resolution transmission electron microscope analysis clearly showed the existence of the Fe(2)O(3) nanoparticles in the Fe-R catalyst. The catalytic activity of the Fe-R catalyst was evaluated by the discoloration and chemical oxygen demand (COD) removal of an azo-dye rhodamine B (RhB, 100 mg/L) and a typical persistent organic pollutant 4-nitrophenol (4-NP, 50 mg/L) in the presence of hydrogen peroxide (H(2)O(2)) under visible light irradiation (lambda > 420 nm). It was found that the discoloration rate of the two contaminants was over 99.3%, and the COD removal rate of the two contaminants was over 87.0%. The Fe-R catalyst showed strong adsorbability for the RhB in the aqueous solution. Moreover, the Fe-R catalyst still showed good stability for the degradation of RhB after five recycles. Zeta potential and Fourier transform infrared spectroscopy were used to examine the photoreaction processes. Finally, a possible photocatalytic mechanism was proposed.

Photocatalytic degradation of Bisphenol A (BPA) using immobilized TiO2 and UV illumination in a horizontal circulating bed photocatalytic reactor (HCBPR)

Photocatalytic degradation of Bisphenol A (BPA) in the presence of titanium dioxide (TiO(2)) and ultraviolet (UV) illumination was performed in a self-designed horizontal circulating bed photocatalytic reactor (HCBPR). TiO(2) catalyst was immobilized on the surface of polyurethane foam (PF) cubes via microwave-assisted liquid phase deposition. The effects of initial BPA concentration, initial pH, TiO(2) dosage and temperature on BPA photodegradation were investigated in order to obtain the optimum operational conditions. The results reveal that the BPA degradation efficiency can be effectively improved by increasing pH from 3.4 to 12.3 or decreasing the initial BPA concentration from 50 to 10 ppm. The optimum TiO(2) carrier dosage (the ratio of the volume of PF carriers to the effective reaction volume of HCBPR) was about 1%. Besides, the effect of temperature on BPA photodegradation was found to be unremarkable in the range of 21.2-30.5 degrees C. Total organic carbon (TOC) was used to evaluate the mineralization of BPA during the photodegradation process. Under the optimum conditions, 95% removal of TOC and 97% removal of BPA can be achieved after 6h of UV radiation, which demonstrates the high photodegradation efficiency of BPA in HCBPR.

The effect of bacterial contamination on the heterotrophic cultivation of Chlorella pyrenoidosa in wastewater from the production of soybean products.

This study examined the impacts of bacteria on the algal biomass, lipid content and efficiency of wastewater treatment during the heterotrophic cultivation of Chlorella pyrenoidosa. Our results showed that soybean-processing wastewater can enhance the accumulation of lipids in algal cells and thus raise the lipid yield in the pure culture. The bacteria coexisting with algae improved the degradation of total nitrogen (TN), total phosphorus (TP), glucose and chemical oxygen demand (COD). Although the biomass productivity of algae was not significantly affected, the total algal lipid content and lipid production rate were slightly reduced when bacteria coexisted with algae. The difference in the compositions of the medium is presumed to be the main contributing factor for the variation in total lipid content in presence and absence of bacteria. The TN, TP, and COD decreased during the assimilatory process undertaken by C. pyrenoidosa, and the removal efficiency of TN by bacteria depended on the type of nitrogen species in the medium. Additionally, the apparent interaction between the bacterial and algal cultures varied with the changes in experimental conditions. Algae could compete with bacteria for the carbon and energy sources, and inhibit the growth of the bacteria in the presence of high organic matter concentration in the medium.

Selective removal of diclofenac from contaminated water using molecularly imprinted polymer microspheres

A molecularly imprinted polymer (MIP) was synthesized by precipitation polymerization using diclofenac (DFC) as a template. Binding characteristics of the MIP were evaluated using equilibrium binding experiments. Compared to the non-imprinted polymer (NIP), the MIP showed an outstanding affinity towards DFC in an aqueous solution with a binding site capacity (Q(max)) of 324.8 mg/g and a dissociation constant (K(d)) of 3.99 mg/L. The feasibility of removing DFC from natural water by the MIP was demonstrated by using river water spiked with DFC. Effects of pH and humic acid on the selectivity and adsorption capacity of MIP were evaluated in detail. MIP had better selectivity and higher adsorption efficiency for DFC as compared to that of powdered activated carbon (PAC). In addition, MIP reusability was demonstrated for at least 12 repeated cycles without significant loss in performance, which is a definite advantage over single-use activated carbon.

Selective trace enrichment of acidic pharmaceuticals in real water and sediment samples based on solid-phase extraction using multi-templates molecularly imprinted polymers

A novel multi-templates molecularly imprinted polymer (MIP), using acidic pharmaceuticals mixture (ibuprofen (IBP), naproxen (NPX), ketoprofen (KEP), diclofenac (DFC), and clofibric acid (CA)) as the template, was prepared as solid-phase extraction (SPE) material for the quantitative enrichment of acidic pharmaceuticals in environmental samples and off-line coupled with liquid chromatography-mass spectrometry (LC/MS/MS). Washing solvent was optimized in terms of kind and volume for removing the matrix constituents nonspecifically adsorbed on the MIP. When 1L of water sample spiked at 1μg/L was loaded onto the cartridge, the binding capacity of the MIP cartridge were 48.7μg/g for KEP, 60.7μg/g for NPX, 52μg/g for CA, 61.3μg/g for DFC and 60.7μg/g for IBP, respectively, which are higher than those of the commercial single template MIP in organic medium (e.g. toluene) reported in the literature. Recoveries of the five acidic pharmaceuticals extracted from 1L of real water samples such as lake water and wastewater spiked at 1μg/L were more than 95%. The recoveries of acidic pharmaceuticals extracted from 10-g sediment sample spiked at the 10ng/g level were in the range of 77.4-90.6%. To demonstrate the potential of the MIP obtained, a comparison with commercial C18 SPE cartridge was performed. Molecularly imprinted solid-phase extraction (MISPE) cartridge showed higher recoveries than commercial C18 SPE cartridge for acidic pharmaceuticals. These results showed the suitability of the MISPE method for the selective extraction of a group of structurally related compounds such as acidic pharmaceuticals.

A new insight on the core-shell structure of zerovalent iron nanoparticles and its application for Pb(II) sequestration

Nanoscale zerovalent iron (nZVI) has shown a high efficacy for removing heavy metals from liquid solution. However, its removal capacity has not been fully explored due to its common shell composition (FeOOH). In this study, a much higher removal capacity of Pb(II) is observed (1667 mg Pb(II)/gFe), which is over 100% higher than the highest removal capacity of nZVI reported before. High-resolution X-ray photoelectron spectroscopy (HR-XPS) reveals that through restricting the dehydration process of Fe(OH)3, nZVI can acquire a unique shell, which is composed of 45.5% Fe(OH)3 and 54.5% FeOOH. The presence of Fe(OH)3 suppresses the reduction of Pb(II), but greatly promotes the co-precipitation and adsorption of Pb(II). Combining the ratio of Fe-released to Pb-immobilized and the result of HR-XPS, a reaction between Fe(0) core, Fe(OH)3, and Pb(II) is proposed. The Fe released from the Fe(0) core leads to the core depletion, observed by transmission electron microscopy (TEM) under high Pb(II) loading. While temperature has little influence on the removal capacity, pH affects the removal capacity greatly. pH<4.5 favors Fe dissolution, while pH>4.5 promotes Pb(II) adsorption. Given the high Pb removal capacity via the Fe(OH)3 shell, nZVI can be used to remedy Pb(II) contamination.

Effect of inoculum sources on the anaerobic digestion of rice straw

The aim of this study was to evaluate the effect of different inoculum sources on the rice straw anaerobic digestion. Six different digestates (DM, SM, CM, MS, AGS and PS) were applied as inoculums and their effects were evaluated in batch reactors. The results indicated that digested manures were more suitable than sludge. Reactors inoculated with digested manures achieved higher, biogas production and lignocellulose degradation. The better adaptability of digested manures had relationship with its higher cellulase and xylanase activities and sufficient nutrients content. DM had the best effect among all three digested manures. Reactors inoculated with DM achieved the highest biogas production (325.3 mL/g VS) and enzymes activities. The synergism between cellulase and xylanase activities played an important role in lignocellulose degradation.

Sorption of carbamazepine from water by magnetic molecularly imprinted polymers based on chitosan-Fe3O4

A novel magnetic-molecularly imprinted polymer (MMIP) based on chitosan-Fe₃O₄ has been synthesized for fast separation of carbamazepine (CBZ) from water. During polymerization, the modified chitosan-Fe₃O₄ was used not only as supporter but also as functional monomer. The properties of obtained MMIP were characterized by scanning electron and transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectra, thermo-gravimetric analysis and so on. The sorption equilibrium data was well described by Freundlich isotherm model and the increase in the temperature generated an increase in the sorption amount, indicating endothermic nature of adsorption process. Sorption kinetics followed the pseudo-second-order model. The feasibility of selective sorption of CBZ from real water by the MMIP was analyzed by using spiked real water samples. The result showed that the sorption capacity of MMIP has no obvious decrease in different water samples whereas there was obvious decline in the sorption amount of the MNIP.

Hierarchically structured α-Fe2O3/Bi2WO6 composite for photocatalytic degradation of organic contaminants under visible light irradiation

The α-Fe2O3/Bi2WO6 composite with a sphere-like hierarchical structure assembled by nanosheets was synthesized by a one-step hydrothermal route without any templates or surfactants. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectrum (UV–vis DRS), Fourier transform infrared (FT–IR) spectrum, X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmet–Teller (BET) analysis. The BET specific surface area of the hierarchically structured α-Fe2O3/Bi2WO6 composite is 61.7 m2 g−1, which is much higher than that (3.5 m2 g−1) of the pure Bi2WO6. The hierarchically structured α-Fe2O3/Bi2WO6 composite exhibited a strong adsorption capability and a higher visible light photocatalytic activity than the pure Bi2WO6 for the photocatalytic degradation of acid red G dye or Rhodamine B (RhB) dye in aqueous solution under visible-light irradiation (>420 nm). The composite still showed the high photocatalytic activity after four reaction cycles. On the basis of the experimental results and calculated energy band positions, the enhanced photocatalytic activity of the composite can be attributed to the hierarchical structure and the coupling effect of α-Fe2O3 and Bi2WO6 in the composite.

High-yield reduction of carbon dioxide into formic acid by zero-valent metal/metal oxide redox cycles

A strategy for reduction of CO2 is described that produces formic acid from CO2 (ca. 80% formic acid yield) via the oxidation of a zero-valent metal under hydrothermal conditions. The oxidized metal can be regenerated using glycerin, which produces lactic acid. Hydrogen production is demonstrated through metal oxidation in the presence of CO2 with zero-valent Fe, Mn, Zn, and Al metals under hydrothermal conditions, where it is found that a maximum hydrogen formation yield of ca. 99.4% was achieved. The metals, once oxidized, could be readily reduced (ca. 100% for Fe) to their zero-valent state by contact with glycerin. The results demonstrate that a carbon cycle can be driven by the oxidation and reduction of commonly available metals.