Qiuyun Zhang

Photocatalytic Ozonation of Dimethyl Phthalate over TiO2 Prepared by a Hydrothermal Method

TiO2 catalyst was prepared by two kinds of different methods. The photocatalytic activity of TiO2 prepared by the hydrothermal method is 2.5 times higher than that by sol-gel in degradation dimethyl phthalate (DMP). The combined photocatalysis with UV irradiation and ozonation (TiO2/UV/O3) process considerably improved mineralization and degradation of dibutyl phthalate compared to combined photocatalysis with UV irradiation (TiO2/UV) process, combined ozonation with UV irradiation (UV/O3) process and ozonation alone (O3) process. DMP can be quickly mineralized in TiO2/UV/O3, its mineralization process followed Langmuir-Hinshelwood model. Its rate constant k is 0.42 mg/ (L•min) and Langmuir adsorption coefficient K is 0.0417 L/mg.

Catalytic ozonation of dimethyl phthalate over cerium supported on activated carbon

Cerium supported on activated carbon (Ce/AC), which was prepared by dipping method, was employed to degrade dimethyl phthalate (DMP) in water. The mineral matter present in the activated carbon positively contributes to its activity to enhance DMP ozonation process. A higher dipping Ce(NO(3))(3) concentration and calcination process increase its microporous volume and surface area, and decreases its exterior surface area. The catalytic activity reaches optimal when 0.2% (w/w) cerium is deposited on activated carbon. Ce/AC catalyst was characterized by XRD, SEM and BET. The presence of either activated carbon or Ce/AC catalyst considerably improves their degradation and mineralization in the ozonation of DMP. During the ozonation (50mg/h ozone flow rate) of a 30 mg/L DMP (initial pH 5.0) with the presence of Ce/AC catalyst, TOC removal rate reaches 68% at 60 min oxidation time, 48% using activated carbon as catalyst, only 22% with ozonation alone. The presence of tert-butanol (a well known OH radical scavenger) strongly inhibits DMP degradation by activated carbon or Ce/AC catalytic ozonation. TOC removal rate follows the second-order kinetics model well. In the ozonation of DMP with 50mg/h ozone flow rate, its mineralization rate constant with the presence of Ce/AC catalyst is 2.5 times higher than that of activated carbon, 7.5 times higher than that of O(3) alone. Ce/AC catalyst shows the better catalytic activity and stability based on 780 min sequential reaction in the ozonation of DMP. Ce/AC was a promising catalyst for ozonizing organic pollutants in the aqueous solution.

Catalytic ozonation of p-chlorobenzoic acid by activated carbon and nickel supported activated carbon prepared from petroleum coke

The aim of this research was to investigate catalytic activity of petroleum coke, activated carbon (AC) prepared from this material, Ni supported catalyst on activated carbon (Ni/AC) in the ozonation of aqueous phase p-chlorobenzoic acid (p-CBA). Activated carbon and Ni/AC catalyst were characterized by XRD and SEM. The presence of petroleum coke did not improve the degradation of p-CBA compared to ozonation alone, but it was advantageous for p-CBA mineralization (total organic carbon, TOC, reduction), indicating the generation of highly oxidant species (*OH) in the medium. The presence of either activated carbon or Ni/AC considerably improves TOC removal during p-CBA ozonation. Ni/AC catalyst shows the better catalytic activity and stability based on five repeated tests during p-CBA ozonation. During the ozonation (50 mg/h ozone flow rate) of a 10 mg/L p-CBA (pH 4.31), it can be more mineralized in the presence of Ni/AC catalyst (5.0 g/L), TOC removal rate is over 60% in 60 min, 43% using activated carbon as catalyst, only 30% with ozonation alone.

Equilibrium, kinetics and thermodynamic studies for sorption of chlorobenzenes on CTMAB modified bentonite and kaolinite.

The sorption of chlorobenzenes (CBs) by cetyltrimethylammonium bromide (CTMAB) modified bentonite and kaolinite was investigated. The sorption isotherms for CBs were nearly linear, suggesting that sorption could be described by a distribution process. The distribution coefficient (K(d)) was primarily affected by the amount of sorbed surfactant. The organic carbon normalized sorption coefficient (K(oc)), however, was particularly dependent on arrangement of the surfactant cations. The K(d) of CBs was larger for CTMAB-bentonites than that for CTMAB-kaolinites, while the case for K(oc) was opposite. Thus, the clay mineral structure and morphology had a considerable influence on the surfactant arrangement, which was responsible for the partitioning of CBs. The sorption of CBs onto both CTMAB-bentonites and CTMAB-kaolinites followed pseudo-second-order kinetics. The intra-particle diffusion model for sorption was also investigated and compared to identify sorption mechanism. The sorption of CBs both on CTMAB-bentonites and CTMAB-kaolinites was exothermic in nature and accompanied by an increase in entropy and a decrease in Gibbs energy in the temperature range of 15-35 degrees C. The results indicated that CBs strongly interacted with CTMAB modified bentonite and kaolinite.

Catalytic Ozonation for the Degradation of P-Chlorobenzoic Acid in Aqueous Solution by Ni Supported Activated Carbon

Catalytic ozonation of p-chlorobenzoic acid (p-CBA) in aqueous solution has been carried out where transitional metal (Ni, Cu, Mn, Co, Fe) supported activated carbon was used as catalysts. Ni supported activated carbon ( Ni/AC) catalyst, which is prepared by the dipping method with an aqueous solution of Ni(NO3)2, shows higher catalytic activity. Activated carbon and Ni/AC catalyst were characterized by XRD, SEM and BET. The presence of either activated carbon or Ni/AC catalyst significantly improves the degradation of p-CBA and TOC removal compared to ozonation alone. Moreover, the Ni/AC catalyst still shows well catalytic activity and stability during p-CBA ozonation after six repetitive uses.