Showing papers by "Xiaolei Qu published in 2016"

Photochemistry of Dissolved Black Carbon Released from Biochar: Reactive Oxygen Species Generation and Phototransformation.

Abstract: Dissolved black carbon (BC) released from biochar can be one of the more photoactive components in the dissolved organic matter (DOM) pool. Dissolved BC was mainly composed of aliphatics and aromatics substituted by aromatic C-O and carboxyl/ester/quinone moieties as determined by solid-state nuclear magnetic resonance. It underwent 56% loss of absorbance at 254 nm, almost complete loss of fluorescence, and 30% mineralization during a 169 h simulated sunlight exposure. Photoreactions preferentially targeted aromatic and methyl moieties, generating CH2/CH/C and carboxyl/ester/quinone functional groups. During irradiation, dissolved BC generated reactive oxygen species (ROS) including singlet oxygen and superoxide. The apparent quantum yield of singlet oxygen was 4.07 ± 0.19%, 2-3 fold higher than many well-studied DOM. Carbonyl-containing structures other than aromatic ketones were involved in the singlet oxygen sensitization. The generation of superoxide apparently depended on electron transfer reactions mediated by silica minerals in dissolved BC, in which phenolic structures served as electron donors. Self-generated ROS played an important role in the phototransformation. Photobleaching of dissolved BC decreased its ability to further generate ROS due to lower light absorption. These findings have significant implications on the environmental fate of dissolved BC and that of priority pollutants.

Enhanced Adsorption of Hydroxyl- and Amino-Substituted Aromatic Chemicals to Nitrogen-Doped Multiwall Carbon Nanotubes: A Combined Batch and Theoretical Calculation Study.

Abstract: A large effort is being made to develop nanosorbents with tunable surface chemistry for enhanced adsorption affinity and selectivity toward target organic contaminants. Heteroatom N-doped multiwall carbon nanotubes (N-MCNT) were synthesized by chemical vapor deposition of pyridine and were further investigated for the adsorptive removal of several aromatic chemicals varying in electronic donor and acceptor ability from aqueous solutions using a batch technique. Compared with commercial nondoped multiwall carbon nanotubes (MCNT), N-MCNT had similar specific surface area, morphology, and pore-size distribution but more hydrophilic surfaces and more surface defects due to the doping of graphitic and pyridinic N atoms. N-MCNT exhibited enhanced adsorption (2–10 folds) for the π-donor chemicals (2-naphthol and 1-naphthalmine) at pH ∼6 but similar adsorption for the weak π-donor chemical (naphthalene) and even lower adsorption (up to a 2-fold change) for the π-acceptor chemical (1,3-dinitrobenzene). The enhance...

Highly selective hydrodechlorination of 1,2-dichloroethane to ethylene over Ag-Pd/ZrO2 catalysts with trace Pd

Abstract: Gas-phase catalytic hydrodechlorination is one of the most efficient and economic methods for the removal of volatile chlorinated alkanes. Novel Ag-based bimetallic catalysts with high ethylene selectivities were prepared using the co-impregnation method. The catalysts were characterized by X-ray diffraction, UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy and IR spectroscopy of CO adsorption. The catalytic performance, in particular the selectivities of the catalysts was examined on hydrodechlorination of 1,2-dichloroethane. Two supported monometallic catalysts (Ag/ZrO 2 and Pd/ZrO 2 ) were included as comparative catalysts. Ag/ZrO 2 exhibited a low 1,2-dichloroethane coversion and high chloroethylene selectivity for the gas-phase hydrodechlorination of 1,2-dichloroethane, while Pd/ZrO 2 had a high conversion and ethane selectivity. In contrast to monometallic catalysts, Ag-Pd/ZrO 2 with trace Pd had substantially enhanced ethylene selectivity, and the bimetallic catalyst with a Pd loading amount of 0.099 wt.% (denoted as Ag(1.99)-Pd(0.099)/ZrO 2 ) exhibited nearly 100% ethylene selectivity. The excellent ethylene selectivity can be attributed to the highly dispersed metallic Pd in Ag particles of Ag(1.99)-Pd(0.099)/ZrO 2 as evidenced by the IR spectra of CO adsorption. The findings in this study indicate that Ag-Pd/ZrO 2 with trace Pd can be used as promising catalyts for highly effective and selective hydrodechlorination of volatile chlorinated alkanes.

Method for adsorption-removing lead pollution in water body by utilizing magnetic loading manganese dioxide composite material

Abstract: The invention discloses a method for adsorption-removing lead pollution in a water body by utilizing a magnetic loading manganese dioxide composite material. The method utilizes magnetic loading manganese dioxide as an adsorbent to remove lead ions in the water body, and comprises the following steps of (1) synthesizing a magnetic core-shell structure of Fe3O4@SiO2 nano particles; (2) loading the manganese dioxide on the magnetic core-shell structure of Fe3O4@SiO2 nano particles, and obtaining the magnetic loading manganese dioxide composite material MnO2-Fe3O4@SiO2; (3) adopting the magnetic loading manganese dioxide composite material MnO2-Fe3O4@SiO2 as the adsorbent to adsorb the lead ions in the water body. The method provided by the invention adopts the magnetic loading manganese dioxide composite material for adsorption removing the lead ions in the water body, so that the method is simple and convenient to operate, the materials are easy to get, the removing effect is remarkable, and the adsorbent is reproducible and can be recycled.