Adsorption and hydroponics experiments were conducted to study the role of citric acid on the phytoremediation of heavy metal contaminated soil. The results show that addition of citric acid decreased the adsorption of both lead and cadmium, such an effect was bigger for cadmium than for lead. The decrease in the adsorption of Pb and Cd was mainly due to a decrease of pH in the presence of citric acid. The presence of citric acid could alleviate the toxicity of Pb and Cd to radish, and stimulate their transportation from root to shoot. The studies of heavy metal forms using sequential extraction demonstrated that lead was mainly existed as FHAC (a lower bioavailable form) in the root, while FHCl was the dominant form in the leaf. The addition of citric acid to the soil changed the concentration and relative abundance of all the forms. The detoxifying effect of citric acid to Pb in shoots might result from the transformation of higher toxic forms into lower toxic forms. Cadmium was mainly present as FNaCl, therefore, it had higher toxicity than lead. The addition of citric acid increased the abundance of FH2O＋FNaCl, indicating that citric acid treatment could transform cadmium into more transportable forms.

Titanium dioxide/bentonite clay nanocomposite prepared by acid-catalyzed sol-gel method was used as photocatalyst in the reaction of cationic azo dye decomposition in water. The incorporation of TiO2 was confirmed by powder X-ray diffraction (XRD) and X-ray photoelectron spectrometer (XPS). The photocatalytic activity of those nanocomposite photocatalysts was much higher than that of the pure titanium dioxides. The nanocomposite created a kinetic synergy effect in Cationic Red GTL (GTL) disappearance with an increase of the rate constant by a factor of 2.57 for neat TiO2 (P-25). The photo-activities were greatly dependent on the solution pH, and it was more effective for GTL to be degraded under alkaline condition. That was likely to contribute for the acid-base equilibria on the surface of the nanocomposite. Results also indicated that the proper addition of hydrogen peroxide could improve the decolorization rate, but the excess hydrogen peroxide could quench the formation of •OH.

A novel tri-primer polymerase chain reaction method (TP-PCR) was developed for the construction of a fused fpg gene, in which no endonuclease and ligase were used. Instead, two templates and three specifically designed primers were applied. Results showed that pheB and gfp genes, which encodes the catechol 2, 3-dioxygenase and the green fluorescent protein (GFP), respectively, were successfully fused into an fpg gene through the rapid TP-PCR system, indicating that TP-PCR method could be a useful tool for DNA fragment fusion in which no proper endonuclease sites were available.

This study focused on the appropriate catalyst preparation and operating conditions for maximizing catalytic reduction efficiencyof nitrate into nitrogen gas from groundwater. Batch experiments were conducted with prepared Pd and/or Cu catalysts with hydrogen gas supplied under specific operating conditions. It has been found that Pd-Cu combined catalysts prepared at a mass ratio of 4:1 can maximize the nitrate reduction into nitrogen gas. With an increase in the quantityof the catalysts, oth nitrite intermediates and ammonia can be kept at a low level. It has also been found that the catalytic activity is mainly affected by the mass ratio of hydrogen gas to nitrate nitrogen, and hydrogen gas gauge pressure. Appropriate operating values of H2/NO3-N ratio, hydrogen gas gauge pressure, pH, and initial nitrate concentration have been determined to be 44.6g H2/g N, 0.15atm, 5.2(-), 100mgL-1 for maximizing the catalytic reduction of nitrate from groundwater.

In this paper, silica gel supported titanium dioxide particles (TiO2/SiO2) prepared by acid-catalyzed sol-gel method was as photocatalyst in the degradation of acid orange 7 (AO7) in water under visible light irradiation. The particles were characterized by X-ray diffraction, BET specific surface area determination, and point of zero charge measurement. The supported catalyst had large surface area, high thermal stability and good sedimentation ability. The photodegradation rate of AO7 under visible light irradiation depended strongly on adsorption capacity of the catalyst, and the photoactivity of the supported catalyst was much higher than that of the pure titanium dioxides. The photodegradation rate of AO7 using 31% TiO2/SiO2 particles was faster than that using P-25 and TiO2 (Shanghai) as photocatalyst by 2.3 and 12.3 times, respectively. The effectof the calcination temperature and the TiO2 loading on the photoactivity of TiO2/SiO2 particles was also discussed.