[Study on adsorption of bisphenol A from aqueous solution on modified activated Carbons].

A commercial activated carbon (WV A1100) was modified with nitric acid, sodium hydroxide and thermal treatment in an atmosphere of N2. Several techniques were used to characterize the physicochemical properties of these materials including BET, XPS, pH(PZC) and Boehm titration. The results indicated that the specific surface area of the W20 remarkably decreased after oxidized by nitric acid. But the amount of surface acidic oxygen-containing functional groups of the oxidized sample increased compared to the W20 and resulting in the points of zero charge (pH(PZC)) changed from 4.95 to 1.50. The changes of surface chemical properties of thermal treatment and sodium hydroxide treatment were opposite to the oxidized sample, as a result, the pH(PZC) of them was changed to near pH 7.0. However, a 43.81% surface area of W20 was also diminished by thermal treatment. Furthermore, the results of BPA adsorption indicated that the oligomerization of BPA on the surface of activated carbon could not be formed through oxidative coupling reactions in the presence of dissolved oxygen. And the data of BPA adsorption on original sample, thermal and sodium hydroxide treatment sample were fitted to the Langmuir isotherm model well. Whereas the Freundlich isotherm model described the adsorptive behavior of the oxidized sample better. In addition, the adsorption capacity of thermal treatment sample was the highest and its saturated adsorption capacity reached 526.32 mg/g. The value was three times higher than that of the oxidized sample. Combined with the results of characterization, it was found that the hydrophobic nature and zero of net charge density of carbon surface were the main factors to affect the BPA adsorption on activated carbons and the adsorption is based on pi-pi theory.

[Ozonation of representative endocrine disruptors (EDs) in water].

The effects of ozone dose, bicarbonate concentration and pH on endocrine disruptors(EDs) removal, such as E1, E2, EE2, DES and 4-n-NP, were investigated through batch experiment. The results indicated that the removal rates were enhanced by increasing ozone dose, and O3 exposures of only 63.6 microg/L were calculated to achieve > or = 92.0% EDs removal efficiency. The presence of bicarbonate (0 - 100 mg/L) inhibited EDs ozonation. Furthermore, the EDs removal rates increased significantly as pH increased. The five apparent rate constants (20 degrees C +/- 0.5 degrees C) of ozone with the five EDs were in the range of (1.67 - 3.89) x 10(6)L (mol s) (-1) at neutral pH (pH approximately 7.0) and (0.93 approximately 1.75) x 10(9) L (mol s)(-1) at basic pH (pH > 10.6). It was indicated that the five EDs were removed rapidly by O3 in water. At the same time, the elementary reaction ozone rate constants (20 degrees C +/- 0.5 degrees C) were calculated, and the reactivity of ozone with ionized EDs [i.e. 1.21 x 10(9) - 3.81 x 10(9) L (mol s)(-1)] was 10(3) - 10(4) times higher than with neutral EDs [i.e. 7.62 x 10(5) - 2.55 x 10(6) L (mol s)(-1)]. The comparative test of EDs ozonation under different water quality conditions indicated that the removal rates of EDs in filtrated water and river water were reduced 26.5% - 50.3% and 57.3% - 72.0% respectively compared with the case using ultrapurified water as the background. It showed that organics in real water would compete with EDs for ozonation.

[Efficiency study on nitrobenzene removal by ozone/zeolite process].

Degradation of nitrobenzene by ozone/zeolite process was investigated in a continuous flow reactor. The results showed that nitrobenzene was degraded by ozone/zeolite process efficiently in comparison to ozone alone. The removal of nitrobenzene was 100% in 7 minutes. The reaction followed pseudo-first-order kinetics. By investigating the effect of scavenger on nitrobenzene removal, it is concluded that nitrobenzene was mainly degraded by hydroxyl radicals in solution. Increasing zeolite dosage and ozone concentration also enhanced nitrobenzene removal. However, there was an optimum removal rate among zeolite dosages. The relationship between the ozone concentrations and the kinetic constants was linear. At the same time, nitrobenzene decomposition was independent of influent nitrobenzene concentration during ozone/zeolite process. Additionally, the degradation rate of ozone/zeolite process was inhibited significantly by increasing ionic strength. When the ionic strength concentration increased from 0 to 1 x 10(-3) mol/L, the removal of nitrobenzene by ozone/zeolite process decreased from 81.2% to 31.6% correspondingly. pH mainly affected the decomposition rate of ozone. As pH decreased, the degradation rate of nitrobenzene by ozone/zeolite process decreased too. Zeolite had a relatively longer lifetime.

[Influence of nanosized TiO2 catalyzed ozonation on the ammonia concentration in Songhua River water].

Changes of the ammonia concentration in Songhua River water treatment using catalyzed ozonation were investigated. Nanosized TiO2 loaded on haydite, silica-gel and zeolite was prepared as the catalyst. The ammonia concentration increased in the first stage, then decreased. After 30 min reaction, the ultimate concentration was close to the initial concentration in ozonation. In catalyzed ozonation which used TiO2/ haydite or TiO2 /silica-gel as the catalyst, the ammonia concentration also increased primarily and then decreased, but the average concentration was higher than that in ozonation alone. In catalyzed ozonation which used TiO2/zeolite as the catalyst, the ammonia concentration decreased primarily, then increased to a peak value, and decreased again. The removal efficiency was close to 80% after 30 min reaction. Effect of ozone dosage, catalyst dosage and temperature were investigated respectively. Increasing the ozone dosage, the maximum of the ammonia concentration appeared ahead and the average concentration of ammonia decreased either in ozonation or in catalyzed ozonation. Increasing the dosage of TiO2 /haydite or TiO2/silica-gel, the average concentration of ammonia increased. The removal efficiency of ammonia benefited from the increase of TiO2/zeolite dosage, but it was affected little when TiO2/zeolite dosage was above 50 g. When the temperature increased from 10 degrees C to 30 degrees C, the changes of ammonia concentration were not affected in catalyzed ozonation using TiO2/haydite or TiO2/silica-gel as the catalyst. While the increase of temperature yielded an increase of ammonia removal efficiency when using TiO2/zeolite as the catalyst.

[Mechanism of degradation of nitrobenzene by ozone/zeolite process].

Adsorption and desorption of ozone on H-form zeolite was investigated in solution. The results showed that ozone could be adsorbed on H-form zeolite, and finally decomposed. And the process of adsorption and desorption was irreversible. After equilibrium of adsorption and desorption, the relationship of the amount of adsorbed ozone with the influent ozone concentration was linear. However, exchanged H-form zeolite by sodium ion at the concentration of 1 x 10(-3) mol/L did not adsorb any ozone. By investigating the effect of cation and zeolite type on ozone/zeolite process oxidizing nitrobenzene, it was investigated that the nitrobenzene removal rate was significantly inhibited by calcium ion. Additionally, during the ozonation of nitrobenzene by ozone/Na-form zeolite and ozone/NH4-form zeolite process individually, the removal rate of nitrobenzene by ozone/Na-form zeolite process was gradually improved as the sodium ion dissolved in solution. It was verified that cations affected ozone diffusing into the pore of zeolite and then self-decomposition and catalysis decomposition. After dealuminated, the ozone/H-form zeolite process did not show any efficiency on nitrobenzene removal. In the end, ozone also can be adsorbed and decomposed at pH 3.0 in zeolite, which showed that the effect of hydrogen ion was not as well as other cations.

[Degradation of trace nitrobenzene in aqueous solution by ozone with catalysis of nanosized TiO2 supported on haydite].

This paper presented the results of catalytic degradation of nitrobenzene by ozone in the presence of nanosized TiO2 supported on haydite, and evaluated influencing factors and the pathway of degradation. Catalysts were prepared by sol-sel method, and sintered in electrical resistance furnace. The optimum sinter temperature was found for preparing the catalyst. The SEM was also used to characterize the catalyst. When the catalyst was sintered at 700 degrees C, it had the best property of catalysis. The catalytic ozonation of nitrobenzene was first order reaction with respect to the concentration of nitrobenzene, and OH* was the dominating species in the oxidation process. As the dose of catalyst increased, the removing rate of nitrobenzene also increased. The highest ozonation rate of this compound, which is 46.5%, was found when pH value was approximately 10. Besides, the catalyst showed good ability after 3 times repeated uses.

[Degradation of trace nitrobenzene by nanosized TiO2 catalyzed ozonation].

Nanosized TiO2 catalyzed ozonation of trace nitrobenzene in water was carried out in an agitated slurry semi-batch. It demonstrated that removal rate of nitrobenzene with catalytic ozonation increased by 44% than ozonation alone. Effect of heat treatments of TiO2, catalyst mass, the initial concentration of ozone and nitrobenzene, and pH were investigated respectively. TiO2 calcined at 550 degrees C showed the best catalytic activity. In the presence of TiO2 calcined at 550 degrees C, about 56.57% of nitrobenzene in the solution could be ozonated. Both ozone dosage and initial concentration of nitrobenzene exerted a positive influence on the catalytic ozonation. But the increase of the catalyst mass did not yield any significant increase of the nitrobenzene removal. The efficiency of catalytic ozonation was special lower at acid pH than basic pH. It was also observed that both ozonation and catalytic ozonation were significantly influenced by tert-butyl alcohol, which testified that nanosized TiO2 catalyzed ozonation of nitrobenzene follows a radicaltype mechanism.