[Mechanism of MgO/GAC Catalyzed Ozonation of Organic Compounds].

MgO/granular activated carbon (MgO/GAC-1) was prepared via an impregnation method, and its activity in ozonation of diuron and acetic acid was investigated. MgO/GAC-1 was also compared in stability to the same catalyst prepared via precipitation according to the literature (MgO/GAC-2). The results showed that MgO/GAC-1 could increase efficiency of ozonation by 15%-35% in the process of degradation of diuron and acetic acid. When the pH of the solution was neutral or alkaline, MgO/GAC-1 could effectively retard the decrease in pH owing to formation of small molecular organic acids, thus ensuring the efficiency of ozone. When the pH of the solution was acidic, MgO/GAC-1 could increase the pH of the solution to a certain extent, thereby enhancing the efficiency of ozonation. The adjusting effect of pH value is the reason why MgO can significantly improve the efficiency of ozonation, a fact that was ignored in the relevant literature. Although MgO/GAC-1 had a larger specific surface area, MgO/GAC-1 had better activity in ozonation. A recycling test also indicated that MgO/GAC-1 had better stability, showing a good prospect for application.

[Degradation of dimethyl phthalate by Ti (IV)-catalyzed O3/H2O2 under acidic conditions].

The degradation efficiencies of dimethyl phthalate (DMP) by O3, O3/H2O2, Ti(IV)/O3 and Ti(IV)/O3/H2O2 were investigated under acidic conditions. The results indicated that Ti(IV)/O3/H2O2 was the best system with the highest degradation efficiency and mineralization rate of DMP, and the highest utilization rate of ozone at pH 2.8. The apparent rate constants of DMP degradation by O3, O3/H2O2, Ti(IV)/O3 and Ti(IV)/O3/H2O2 under the same conditions were 3.96 x 10(-4) s(-1), 9.54 x 10(-4) s(-1) 1.07 x 10(-3) s(-1) and 6.41 x 10(-3) s(-1), respectively. The ozone utilization rate of Ti(IV)/O3/H2O2 was improved by 6.51% compared with that of ozonation alone. The experimental results showed that the optimized concentrations of Ti(IV) and H2O2 were 1.4 mg x L(-1) and 10 mg x L(-1), respectively. According to the results of gas chromatography-mass spectrometry (GC/MS) and ion chromatography analysis, the possible reaction pathway of DMP degradation by Ti(IV)/O3/H2O2 was proposed and discussed.

Kinetics of Fe(3)O(4)-CoO/Al(2)O(3) catalytic ozonation of the herbicide 2-(2,4-dichlorophenoxy) propionic acid.

The presence of Fe(3)O(4)-CoO/Al(2)O(3) can improve degradation efficiency significantly during the ozonation of the herbicide 2-(2,4-dichlorophenoxy) propionic acid (2,4-DP). The main factors affecting degradation efficiency, such as pH, the catalyst concentration and addition of the scavenger, were investigated. The kinetics of the catalytic ozonation are also discussed. The results indicate that two factors, the oxidation after adsorption of 2,4-DP and the oxidation of hydroxyl radicals (OH), lead to a great enhancement in ozonation efficiency during the catalytic ozonation of 2,4-DP in the presence of Fe(3)O(4)-CoO/Al(2)O(3), in which the oxidation of the OH plays an important role. Under controlled conditions, the apparent reaction rate constants for the degradation of 2,4-DP were determined to be 2.567 × 10(-4)s(-1) for O(3) and 1.840 × 10(-3)s(-1) for O(3)/Fe(3)O(4)-CoO/Al(2)O(3). The results from the analysis of the reaction kinetics using the relative method showed that O(3)/Fe(3)O(4)-CoO/Al(2)O(3) possessed a larger R(ct) (R(ct) is defined as the ratio of the ·OH exposure to the O(3) exposure, R(ct) = ∫C(t)(OH) dt/C(t)O(3)dt) than O(3), indicating that O(3)/Fe(3)O(4)-CoO/Al(2)O(3) produced more hydroxyl radicals.

[Oxidative efficiency of the system of electrolysis coupled ozonation].

The oxidation system of electrolysis coupled ozonation (electrolysis-ozonation) was used to degrade 4-chlorophenol (4-CP), and its mechanism was discussed on the basis of kinetic analysis. The experimental results indicated the electrolysis-ozonation system had a significant synergistic effect during degradation of 4-CP. For example, the electrolysis-ozonation had the 4-CP removal rate of 92.7% and the COD removal rate of 64.9% in 900 s, respectively; while electrolysis alone plus ozonation alone only had the 4-CP removal rate of 69.7% and the COD removal rate of 30.1% under the same conditions. The results of H2O2 concentration analysis and photocurrent test showed that the synergistic mechanism of electrolysis-ozonation included two factors: (1) production of *03- at the cathode; (2) H2O2 generation resulting from reduction of dissolved oxygen. The above two factors led to generation of *OH in system effectively.

[CuO-Ru/Al2O3 catalytic ozonation of acetophenone in water].

Two-component CuO-Ru based on active Al2O3 (CuO-Ru/Al2O3) catalyst was prepared by incipient wetness impregnation and used to catalytic ozonation of acetophenone (AP). The results showed that doping Ru could significantly improve the catalytic activity of CuO/Al2O3. For example, the COD removal rates of AP solution after 30 min by ozonation alone, CuO/Al2O3/O3, and CuO-Ru/Al2O3/O3 were 6.3%, 20.0% and 54.0%, respectively. The change of pH almost had no affect on degradation efficiency of AP. However, a comparison of COD removal between ozonation alone and catalytic ozonation indicated that CuO-Ru/Al2O3 catalyst was more suitable for application in neutral or acidic condition. CuO-Ru/Al2O3 catalyst could accelerate decomposition rate of ozone in water, and its decomposition rate constant reached 2.58 x 10(-3) s(-1) while that of ozone alone in double-water was 1.19 x 10(-3) s(-1). The experimental result of t-butanol indicated that CuO-Ru/Al2O3 catalytic ozonation of AP followed a radical-type mechanism.

[Kinetic and mechanism of ozonation of terephthalic acid].

The effect of ozonation of terephthalic acid (TA) was evaluated, and the kinetic and mechanism of this process were also discussed. The rate constants of TA with ozone and OH radicals calculated by the relative method are (0.047 +/- 0.010) L x (mol x s)(-1) and 2.28 x 10(9) L x (mol x s)(-1), respectively. The above result was in accordance with the apparent reaction rate constant of ozonation of TA when the process was controlled by chemical reaction. Intermediates detected by high-performance liquid chromatography (HPLC) and ion chromatography (IC) included benzoic acid, tartaric acid, formic acid and oxalic acid, therefore the possible destruction pathway of ozonation of TA was proposed on the basis of above results.

[Deactivation mechanism of Pt anode in the process of electroxidation of p-chlorophenol].

Deactivation of Pt electrode in the process of electroxidation of p-chlorophenol (p-CP) was investigated using linear sweep voltammetry, LC/MS and spectrum analysis techniques. The experiment results indicated that Pt would lose its electro-catalytic activity soon because polymer formed at the electrode surface. The in-site IR spectra of Pt showed two weak absorption bands appeared at 1 200 and 1 800 cm(-1) during the oxidation of p-CP, which are characteristics of aromatic ether and carbonyl group, respectively. Increasing initial concentration of p-CP and pH value of solution would accelerate the deactivation speed of Pt. Acetonitrile lixivium for deactivated Pt was analyzed by LC/MS, and it was found that the polymers formed at the surface of Pt were some mixed compounds. The mechanism of polymerization includes the following ways: coupling reaction of organic radical each other; substituting reaction of organic radical with p-CP (or intermediates or small polymers).

[Study on the mechanism of ozonation of organic combination with UV radiation].

Nitrobenzene, glycolic acid and acetic acid were selected to be degraded by O3/UV. During the degradation of nitrobenzene by O3/ UV, addition of MnO2, an effective catalyst to decompose H2O2 in water, decreased the degradation efficiency obviously, and the degradation efficiency of O3 /UV was even lower than that of ozonation alone, for example, the TOC removal rates of nitrobenzene by O3 /UV, O3 and O3/UV + MnO2 were 44% , 41% and 39% in 40 minutes, respectively. These results demonstrate that intermediate H2O2 plays an important role in enhancement of degradation efficiency of O3/UV. Furthermore, the characteristic of organic, which acts as promoter or inhibitor in the process of ozonation, also affects the degradation efficiency of O3/UV directly, when glycolic acid, a promoter in ozonation, was degraded, the combination UV radiation with ozonation could remove it efficiency, the removal rate of glycolic acid reached 76% in 30 minutes; however, when acetic acid, an inhibitor in ozonation, was degraded by O3/UV, the removal rate of acetic acid was very low, which was similar with that of ozonation alone.

Removal of terephthalic acid in alkalized wastewater by ferric chloride.

Terephthalic acid, which is a main component in alkali-decrement wastewater, is efficiently removed using ferric chloride in high pH solutions. About 90% removal of terephthalic acid is achieved at pH between 8 and 11. Especially, the removal reached 94.3% at pH 11. However, as the pH increased from pH 12 and 13, the low removal of terephthalic acid were found. The increasing ferric chloride dosage had a dramatic positive impact on the achieved removal of terephthalic acid. Further increase in the ferric chloride dosage did not produce better removal rate. The increase of terephthalic acid concentration also led to the increase of ferric chloride dosage in order to get the same removal of terephthalic acid. There was approximately a negative linear relationship between terephthalic acid concentration and removal of terephthalic acid. Compared with other coagulants, it can be seen that ferric chloride is more effective in a high pH solution and the amount of ferric chloride required is also less as compared with aluminum chloride, magnesium chloride and calcium chloride. Our results clearly showed that terephthalate anions strongly binds to positive Fe(OH)(3) flocs and forms insoluble complexes, probably through a mechanism involving electrostatic attraction. The electrostatic attraction may be particularly useful means of purifying wastewater in high pH solutions.

[Study on dechlorination of p-chlorophenol by Ni/Fe bimetallic particles].

Dechlorination property of p-chlorophenol (p-CP) by Ni/Fe bimetallic particles was studied in this work. The experimental results show that adsorbed hydrogen atom is the main reductive agent for dechlorination of p-CP and chemical reaction at the surface of catalyst is the rate-determing step in this process. The catalyst with mass ratio of 2.96% Ni had the largest specific surface area and also had the highest dechlorination efficiencies (64% in 90 min) under the same conditions. The apparent kinetics of p-CP dechlorination by Ni/Fe was the first order reaction and apparent rate constant (kappa) was proportional to the specific surface of catalyst. The apparent rate constant per specific surface area (kappa') was also calculated (7.61 x 10(-4) min(-1) m(-2)). Temperature was also an important parameter in this system. The dechlorination efficiency was proportional to temperature when it is below 43 degrees C, when temperature exceeded 43 degrees C, increasing temperature had inverse effect on dechlorination efficiency.

[Reductive dechlorination of atrazine by Ni/Fe bimetallic particles].

Dechlorination of atrazine under acidic conditions was studied by using Fe and Ni/Fe bimetallic particles respectively for the confirmation of the catalytic role of Ni/Fe. Effect of pH value, Ni/Fe proportion and dosage of metal powder were discussed as well. The results indicated that Ni/Fe bimetallic particles was very effective for dechlorination of atrazine, with the dechlorination efficiencies above 90% by using 1.22% (W/W) Ni/Fe at pH value of 2.0 in 30 minutes, very superior to Fe particle with the dechlorination efficiencies only 22.21% in 90 minutes under the same conditions. By the comparison of the surface morphology of both Fe and Ni/Fe and experimental results, catalytic mechanism of Ni/Fe bimetallic particles was also proposed.

Rapid treatment of atrazine-contaminated water by nickel/iron bimetallic system.

The utility of nickel/iron in the remediation of atrazine-contaminated water was investigated. The experimental results showed that nickel/iron had effective catalytic activity in dechlorinating atrazine under acidic conditions. The dechlorination reaction approximately followed the first-order kinetics under the experimental conditions (nickel/iron: 1.0 g/250 ml; C(atrazine) = 20.0 mg/L), the reaction rate increased with decreasing pH value of the reaction solution and increasing the proportion of Ni : Fe within 2.95%. For condition with 2.95% nickel/iron, the reaction rate constants were 0.07518 (R = 0.9927), 0.06212 (R = 0.9846) and 0.00131 min(-1) (R = 0.9565) at pH = 2.0, 3.0 and 4.0, respectively. HPLC analysis was used to monitor the decline of atrazine concentration.

Characteristics of MnO2 catalytic ozonation of sulfosalicylic acid and propionic acid in water.

The characteristics of different types of MnO(2) catalytic ozonation of sulfosalicylic acid (SSal) and propionic acid (PPA) have been investigated in this paper. The experimental results show the dependence of catalytic activity of MnO(2) on organic compounds and the pH of solutions, but it is independent on the type of MnO(2). For example, three types of MnO(2) have not any catalytic activity when ozonation of PPA under the condition of this experiment. All MnO(2) catalytic ozonation of SSal at pH=1.0 have a greater total organic carbon removal than ozonation alone has, however, at pH=6.8 and 8.5, catalytic efficiency is not observed. Furthermore, the batch experimental results indicate that there are no direct relationship between the activity of metal oxide catalytic decomposition of ozone and that of its catalytic degradation of organic compounds.