Chunli Kang

Photo-Fenton effect of 4-chlorophenol in ice.

The photoconversion of 4-chlorophenol (4-CP) in a simulated sunlight-Fenton system was investigated in ice and aqueous solution. It was found that the hydroxyl radical (OH) had an important effect on the photoconversion of 4-CP in both phases, but the effects of Cl(-), SO4(2-), NO3(-), and HCO3(-) were different. In aqueous solution, the photoconversion efficiency of 4-CP was proportional to the OH concentration, and hence, Cl(-) and HCO3(-) as OH scavengers prohibited the photoconversion; SO4(2-) had little effect; NO3(-) promoted the process under certain conditions owing to OH being generated by the photolysis of NO3(-). In ice, however, the photoconversion efficiency of 4-CP was not proportional to the concentration of OH. The photoconversion efficiency of 4-CP increased with increasing concentrations of all ions, although the OH remained almost constant, only increasing or decreasing slightly. This provides new evidence for the presence of a quasi-liquid layer (QLL). Hydroxylation products were detected in both phases. All photoproducts in aqueous solution contained only a single benzene ring, whereas in ice, dimers were also detected.

Photooxidation of Furfural with Phthalocyanine-sensitized TiO2 Particle Under Xenon Lamp

Copper phthalocyanine was selected as the photosensitizer to sensitizer TiO2 in this experiment with furfural as the target pollutant. The composite catalysts(TiO2/CuPC) obtained showed a great activity under a xenon lamp. By experiments, the optimal preparation conditions of the composite catalysts were set as follows: the CuPC loading mass fraction was 1.5%, the mass fraction of acetylacetone was 0.3%, and the stirring time was 10 h. UV-Vis diffuse reflectance spectra, XRD, and BET were used to characterize the properties of the composite catalysts, which showed that after loading CuPC on TiO2, the composite catalyst retained the same crystal structure as pure TiO2 and the wavelength range of its absorption spectrum was broadened to 600–700 nm while its surface area was smaller than that of the pure TiO2. Under the optimal conditions, 20 mg/L furfural solution was degraded by nearly 90% and TOC by about 70%. When the catalyst was reused 6 times, the activity of the catalyst was still retained by about 75%

Thermodynamic characteristics and mechanisms of heavy metals adsorbed onto urban soil

The thermodynamic characteristics of heavy metals adsorbed onto urban soil and the relative adsorption mechanisms were studied by the batch experiment. The results show that there existed dynamic adsorption-desorption equilibrium processes of cationic and anionic ions of heavy metals onto urban soil, which may have an impact on the pH of the adsorption system. The amounts of heavy metals adsorbed onto urban soil increased with the increase of the equilibrium concentration, but their adsorption amounts were not the maximum adsorption amounts. The higher the pH was, the greater the adsorption capacity of the urban soil at the same equilibrium concentration was, and the adsorption amounts of heavy metals onto urban soil followed the order of Pb>Cu>Cd>Zn>Ni. There were coordination reaction, hydrolysis reaction, exchange reaction in the adsorption processes of heavy metals onto urban soil. With the increase of pH, the influencing degree of pH on the different reactions of heavy metals in the soil increased, meanwhile the effects of other physicochemical properties of soil on the adsorption of heavy metals were weakened.

Remove of heavy metals(Cu2+, Pb2+, Zn2+ and Cd2+) in water through modified diatomite

At present, heavy metal pollution has become a major environmental problem, influencing the survival of human and other creatures. Developing heavy metal ion adsorbents, which are environment friendly, of low cost and good performance is one of the effective means to solve heavy metal pollution. Rich low-grade diatomite mineral, as raw material, was modified with calcium carbonate to improve the adsorption properties of diatomite for heavy metal ions. The effects of dosage(m), pH, adsorbing time(t), temperature(T) and concentration of adsorbent(c) on the removal rate of heavy metal ions(Cu2+, Pb2+, Zn2+ and Cd2+) were studied. The results show that under the suitable conditions, T=15 °C, c=1.5 mmol/L, m=10 g/L, t=60 min, in a weak acid environment, the removal effect of the four kinds of metal ions by modified diatomite is the best.

Effect of root exudates on pentachlorophenol adsorption by soil and its main chemical components

The relationship between root exudates (REs) and the adsorption of organic pollutants has important impacts on phytoremediation of organic contaminated soil. The effect of REs collected from alfalfa (Medicago sativa Linn.) on pentachlorophenol (PCP) adsorption by soil and its main chemical components was investigated. The experimental results indicated that the data of PCP adsorption was fitted to Langmuir equation well. PCP was adsorbed mainly by organic matter and Fe oxides, but inhibited by Mn oxides in soil. The thermodynamic processes of PCP adsorption onto different soil samples were not changed in the presence of REs, but the adsorption amounts of PCP decreased. The effect of REs was functioned through affecting PCP adsorption by the main chemical components of soil, whose influencing degree was related to the adsorption capacities of the soil components for PCP. The decreases of PCP adsorption were induced mainly by the low-molecular-weight REs promoting the organic matter release from the soil sa...

The Effects on Solubility of PCP by Sunflower (Helianthus Annuus) Root Exudates in Different Environmental Conditions

The characteristics of sunflower ( Helianthus annuus ) root exudates and their effects on solubility of PCP in different environmental conditions were investigated by the indoor simulation cultivating methods. The results indicated that contents of high-molecular-weight and polarity fractions were very high; the biodegradating percentage increased with time elapsed, and the biodegradating percentage reached 56.50% on the 5th day. Root exudates can enhance solubility of PCP. The effects on solubility of PCP by root exudates obtained in different conditions were different obviously. There were the greatest values in the effects of solubilization of root exudates obtained at experimental illumination times and temperatures to PCP; the effects on solubility of PCP by root exudates obtained at experimental illumination intensities and gradient of KH2PO4 nutrition were very complex; the effects of solubilization of root exudates obtained at Pb contamination to PCP increased with increasing concentration of Pb.

Hydrothermal in situ synthesis of Rb and S co-doped Ti-based TiO2 sheet with a thin film showing high photocatalytic activities

TiO2 is considered as one of the most promising semiconductor photocatalysts used to degrade organic pollutants. Element doping has a good effect on improving the properties of TiO2. Herein, by using Rb2SO4, we explored the in situ synthesis of Ti-based TiO2 sheets with a thin film through a hydrothermal reaction. Then, the photocatalyst was successfully fabricated by calcination. All samples were characterized by FT-IR, XRD, SEM, XPS, PL and UV-vis DRS measurements. The results indicate that the S doping together with surface hydroxyl groups lead to the band gap narrowing. S and a trace amount of Rb element can enable the formation of uniform microspheres on the surface of the Ti plate and the major phase transformed from titanium to anatase. The band gap absorption extended from 400 nm to 600 nm. The photocatalytic properties were investigated by performing the degradation of methyl orange (MO) and 4-chlorophenol (4-CP) in the aqueous solutions under UV and simulated sunlight. In the series of TiO2 photocatalysts, Rb/S/TiO2-48 shows the best photocatalytic efficiency and good photocatalytic performance on recycling. Interestingly, when H2O2 was added to the MO aqueous solution, a synergistic effect of the TiO2 thin film and H2O2 on degrading the pollutant was observed.

Adsorption of Basic Dyes Using Walnut Shell-based Biochar Produced by Hydrothermal Carbonization

Hydrothermal carbon(HC) was prepared from walnut shells, which are abundant in Northeastern China. The prepared HC was used as a precursor to produce nitric acid modified carbon(MC). The hydrothermal carbonization included dehydration and decarboxylation processes wherein the hemicellulose was completely decomposed and the cellulose was partly decomposed, with some oxygen-containing functional groups being produced. The aromaticity, specific surface area and pore content of the HC increased, but its polarity decreased. With 6 mol/L nitric acid and a modification time of 15 min, the specific surface area and pore content decreased, but the proportion of oxygen-containing functional groups on the surface increased significantly, thereby improving the dye adsorption performance. The adsorption of methylene blue and malachite green was best described by the pseudo-second-order kinetic and Langmuir isotherm models. The adsorption capacity of MC was determined to be much larger than that of HC.

The photoconversion of gamma-hexachlorocyclohexane under UV irradiation in water, snow and ice

The photochemistry of organic pollutants has received increasing attention in ice and snow. In this work, the photoconversion of gamma-hexachlorocyclohexane (γ-HCH) under UV irradiation was investigated in water, snow and ice. The photoconversion rate, products and mechanisms were inspected, and the effect of inorganic ions (NO2(-), NO3(-), HCO3(-) and Fe(2+)) was discussed. The results showed that γ-HCH could be photoconverted in water, snow and ice, with the photoconversion rate being fastest in snow, and slowest in ice. All photoconversion could be described by the first-order kinetics model. In water, snow and ice, the common photoproducts of γ-HCH were alpha-hexachlorocyclohexane (α-HCH) and pentachlorocyclohexene. α-HCH was generated by a change in the bonding of a chlorine atom in γ-HCH; pentachlorocyclohexene was generated by the removal of a molecule of chlorine hydride from a molecule of γ-HCH. Different concentrations of NO2(-), NO3(-) and HCO3(-) all inhibited the photoconversion of γ-HCH, and the inhibition effect decreased with increasing concentrations of NO2(-) and NO3(-), but increased with the increasing concentrations of HCO3(-). Different concentrations of Fe(2+) promoted the photoconversion of γ-HCH in water and ice, but had little effect in snow.

Studies on the Properties of Root Exudates and Their Effects on Solubility of Pentachlorophenol (PCP)

The properties of plant root exudates and their effects on the water solubility of PCP were investigated in this paper. The results showed that the hydrophobic and the high-molecular-weight fractions of sunflower( Helianthus annuus ) root exudates were more than those of lucerne( Medicago sativa ) root exudates. With time elapsed, the biodegradation rate of lucerne root exudates was higher than sunflower root exudates. The UV adsorption value of root exudates decreased with increasing wavelengths, and the adsorption value of sunflower root exudates were higher than lucerne root exudates. Root exudates may enhance the water solubility of PCP. The solubilization of PCP increased with increasing concentrations of root exudates, and there was excellent linearity between them. The solubilization of sunflower root exudates was stronger than that of lucerne root exudates. Root exudates may enhance water solubility of organic pollutants, because they belong to surface active substance; and the solubilization mechanism was partition effect whose intensity closely correlated with hydrophobic components in the high-molecular-weight fractions of root exudates.