Biomedical subjects

Xin-hua Xu

Publications and source records attributed to Xin-hua Xu.

12 recordsLinked to original sources

PubMed2006

Hg(0) absorption in potassium persulfate solution.

The aqueous phase oxidation of gaseous elemental mercury (Hg(0)) by potassium persulfate (KPS) catalyzed by Ag(+) was investigated using a glass bubble column reactor. Concentration of gaseous mercury and potassium persulfate were measured by cold vapor atom absorption (CVAA) and ion chromatograph (IC), respectively. The effects of pH value, concentration of potassium persulfate and silver nitrate (SN), temperature, Hg(0) concentration in the reactor inlet and tertiary butanol (TBA), free radical scavenger, on the removal efficiency of Hg(0) were studied. The results showed that the removal efficiency of Hg(0) increased with increasing concentration of potassium persulfate and silver nitrate, while temperature and TBA were negatively effective. Furthermore, the removal efficiency of Hg(0) was much better in neutral solution than in both acidic and alkaline solution. But the influence of pH was almost eliminated by adding AgNO(3). High Hg(0) concentration has positive effect. The possible reaction mechanism of gaseous mercury was also discussed.

Journal Article↗

PubMed2006

Structure relationship of nitrochlorobenzene catalytic degradation process in water over palladium-iron bimetallic catalyst.

Two isomers of nitrochlorobenzene (o-, and p-NCB) were treated by a Pd/Fe catalyst in aqueous solutions through catalytic amination and dechlorination. Nitrochlorobenzenes are rapidly converted to form chloroanilines (CAN) first through an amination process, and then rapidly dechlorinated to become aniline (AN) and Cl(-), without the involvement of any other intermediate reaction products. The amination and dechlorination reaction are believed to take place predominantly on the surface site of the Pd/Fe catalysts. The dechlorination rate of the reductive degradation of the two isomers of nitrochlorobenzene (o-, and p-NCB) in the presence of Pd/Fe as a catalyst was measured experimentally. In all cases, the reaction rate constants were found to increase with the decrease in the Gibbs free energy (correlation with the activation energy) of NCBs formation; the activation energy of each dechlorination reaction was measured to be 95.83 and 77.05 kJ/mol, respectively for o- and p-NCB. The results demonstrated that p-NCBs were reduced more easily than o-NCBs.

Catalysis↗

PubMed2005

Pharmacodynamic effects and kinetic disposition of rabeprazole in relation to CYP2C19 genotype in healthy Chinese subjects.

AIM: To investigate whether the pharmacodynamics and pharmacokinetics of rabeprazole are dependent on CYP2C19 genotype status in healthy Chinese Han subjects. METHODS: The CYP2C19 genotype status of healthy Chinese Han volunteers was determined using the polymerase chain reaction-restriction fragment length polymorphism method. Twenty healthy subjects volunteered to participate in the study. There were seven homozygous extensive metabolizers (homEM), six heterozygous extensive metabolizers (hetEM), and seven poor metabolizers (PM). All subjects were Helicobactor pylori-negative, which was determined by sero-logy and 13C-urea breath tests. Rabeprazole (20 mg) was taken orally once daily in the morning for 8 days, and intragastric pH values were monitored for 24 h by Digitrapper pH after day 1 (single dose) and day 8 (repeated dose). Meanwhile, blood samples were collected at various time-points for 24 h after administration. The serum concentrations of rabeprazole were measured using high-performance liquid chromatography. RESULTS: The mean area under the curve (AUC) values for rabeprazole differed among the three different genotype groups, with a relative ratio of 1.0, 1.3, and 1.8 after a single dose and 1.0, 1.1, and 1.7 after repeated doses in the homEM, hetEM, and PM groups, respectively. Mean AUC values for rabeprazole after a single dose and after repeated doses were significantly different between the homEM and PM groups, but not between the homEM and hetEM or hetEM and PM groups. No significant differences in intragastric pH median, pH>4 total time, and pH>4 time percentage of 24 h, were observed among the three different genotype groups after a single dose or after repeated doses of rabeprazole. CONCLUSION: In healthy Chinese Han subjects, the pharmacokinetics of rabeprazole are dependent on a certain degree on CYP2C19 genotype status; however, the acid-inhibitory efficacy of rabeprazole is not influenced significantly by CYP2C19 genetic polymorphism.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed2005

Remediation of Cr(VI) in solution using vitamin C.

The effectiveness of vitamin C in treating Cr(VI)-contaminated water is being evaluated. Cr(VI) is an identified pollutant of some soils and groundwater. Vitamin C, an important biological reductant in humans and animals, can be used to transform Cr(VI) to essentially nontoxic Cr(III). The removal efficiency was 89% when the mass concentration of vitamin C was 80 mg/L in 60 min, and nearly 100% Cr(VI) was removed when the mass concentration was 100 mg/L. Our data demonstrated that the removal efficiency was affected by vitamin C concentration, the reaction temperature and the dissolved oxygen concentration. The reaction mechanism of Cr(VI) by vitamin C was presented. Our study opens the way to use vitamin C to remediate Cr(VI)-contaminated soils and groundwater.

Ascorbic Acid↗

PubMed2005

Study on US/O3 mechanism in p-chlorophenol decomposition.

Study on the effects of sonolysis, ozonolysis and US/O3 system on the decomposition of p-chlorophenol in aqueous solutions indicated that in the cases of US/O3 system, individual ozonolysis and sonolysis, the decomposition rate of p-chlorophenol reached 78.78%, 56.20%, 2.79% after a 16-min reaction while its CODcr (chemical oxygen demand) removal rate was 97.02%, 62.17%, 3.67% after a 120-min reaction. The decomposition reaction of p-chlorophenol follows pseudo-first-order kinetics. The enhancement factors of p-chlorophenol and its COD(cr) under US/O3 system reached 63% and 237% respectively. The main intermediates during the decomposition include catechol, hydroquinone, p-benzoquinone, phenol, fumaric acid, maleic acid, oxalic acid and formic acid. The decomposition mechanism of p-chlorophenol was also discussed.

Chlorophenols↗

PubMed2005

Fe salts as catalyst for the wet oxidation of o-chlorophenol.

Catalytic wet air oxidation (CWAO) of o-chlorophenol in wastewater was studied in a stainless steel autoclave using four different Fe catalysts in the temperature range of 100-200 degrees C. Experimental results showed that high rate of o-chlorophenol and COD(Cr) (Chemical Oxygen Demand, mg/L) removal by CWAO was obtained at relatively low temperature and pressure. The catalysts Fe2(SO4)3, FeSO4, Fe2O3 and FeCl3 all exhibited high catalytic activity. More than 93.7% of the initial COD(Cr) and nearly 100% of o-chlorophenol were removed at 150 degrees C after 150 min with FeSO4 as catalyst. The CWAO of o-chlorophenol was found to be pseudo-first order reaction with respect to o-chlorophenol, with activation energy of 75.56 kJ/mol in the temperature range of 100-175 degrees C.

Catalysis↗

PubMed2005

Enhanced catalytic degradation process of o-nitrochlorobenzene by palladium-catalyzed fe0 particles.

Over Pd/Fe bimetallic catalyst, o-nitrochlorobenzene (o-NCB), at a concentration of 20 mg/L in aqueous solutions, is rapidly converted to o-chloroaniline (o-CAN) first, and then quickly dechlorinated to aniline(AN) and Cl-, without other intermediate reaction products. The aminated and dechlorinated reactions are believed to take place on the surface site of the Pd/Fe. The o-NCB removal efficiency and the next dechlorination rate increase with an increase of bulk loading of palladium and catalysts addition due to the increase of both the surface loading of palladium and the total surface area. These results indicate that reduction, amination and dechlorination of o-NCB by palladium-catalyzed Fe0 particles, can be designed for remediation of contaminated groundwater.

Catalysis↗

PubMed2004

Treatment of chitin-producing wastewater by micro-electrolysis-contact oxidization.

The technique of micro-electrolysis-contact oxidization was exploited to treat chitin-producing wastewater. Results showed that Fe-C micro-electrolysis can remove about 30% COD(cr), raise pH from 0.7 to 5.5. The COD(cr) removal efficiency by biochemical process can be more than 80%. During a half year's operation, the whole system worked very stably and had good results, as proved by the fact that every quality indicator of effluent met the expected discharge standards; which means that chitin wastewater can be treated by the technique of micro-electrolysis, contact oxidization.

China↗

PubMed2004

Catalytic dechlorination of o-chlorophenol by nanoscale Pd/Fe.

Transformation of chlorophenols by nanoscale bimetallic particles represents one of the latest innovative technologies for environmental remediation. Nanoscale Pd/Fe bimetallic particles were synthesized in the laboratory for treatment of o-chlorophenol. Most of the nanoscale particles are in the size range of 20-100 nm. BET specific surface area of the nanoscale Pd/Fe particles is 12.4 m2/g. In comparison, a commercially available Fe powder( < 100 mesh) has a specific surface area of just 0.49 m2/g. Batch experiments demonstrated that the nanoscale Pd/Fe bimetallic particles can effectively dechlorinate o-chlorophenol. Dechlorination efficiency is affected by the mass fraction of Pd in the bimetal, nanoscale Pd/Fe mass concentration and mixing intensity.

Catalysis↗

PubMed2004

[Dechlorination of p-dichlorobenzene by metallic catalytic reduction technology].

Pd/Fe bimetallic catalysts were synthesized by chemical deposition and used to dechlorination treatment of p-DCB. Batch experiments demonstrated that the Pd/Fe bimetallic particles can effectively dechlorinate p-DCB. Dechlorination efficiency accounted for more than 90% at Pd weight ratio (Pd to Fe) 0.02% and metal to solution ratio about 4g/74mL in 90min. Dechlorination ratios were affected by reaction temperature, initial pH, Pd ratio and the addition of Pd/Fe. Chlorobenzene represented stable partially dechlorinated intermediates in the generation of benzene.

Catalysis↗

PubMed2003

2-Chlorophenol oxidation kinetic by photo-assisted Fenton process.

Experimental data are presented to test and validate a kinetic model for the oxidation of 2-chlorophenol wastewater by photo-assisted Fenton process. The data showed that this process had produced good effects under acidic conductions. Up to 90% 2-chlorophenol was removed after 90-minute reaction time with H2O2 of 25% COD(Cr, in), while in UV/H2O2 system only 16.8% 2-chlorophenol was removed after one hour treatment. The optimal pH in this reaction occurred between pH 3.0 and pH 4.0. The reaction kinetics for photo-assisted Fenton process experimented in this research was investigated. Kinetic models were proposed for the treatment of 2-chlorophenol wastewater. The reaction was found to follow the 2nd order. The equations of reaction kinetics are as follows: -d[RH]/dt = K(RH) [RH] [H2O2]0 exp(-K(H2O2) t); -d[COD(Cr)]/dt = K(COD(Cr)) [COD(Cr)] [H2O2]0 exp(-K' t). The prediction of the models was found to be in a good agreement with experimental results, thus confirming the proposed reaction mechanism.

Chlorophenols↗

PubMed2002

[Instant repair of soft tissue defect of limb by simple skin traction technique].

OBJECTIVE: To summarize the application of simple skin traction technique in repair of soft tissue defect of limb. METHODS: From 1999, 42 cases of soft tissue defect of limbs were repaired by simple skin traction technique instantly; the defect area ranged from 2.5 cm x 2.0 cm to 8.0 cm x 6.5 cm. RESULTS: The soft tissue defect less than 8.0 cm can be sutured instantly. All of the wound achieved primary healing without infection and necrosis of skin edge, the circulation and sensation of limbs were normal; healing time was 10 days to 16 days, 12.8 days on average. Thirty-two cases were followed up for 6 months; the shape and function recovered well. CONCLUSION: Simple skin traction technique is a good option to repair the soft tissue defect of limbs.

Adolescent↗