ABSTRACT
The objective of this study is to investigate the qualitative mechanisms of Zn2+ adsorption on carp biochars (CMBx) produced from dead carp at different temperatures (450-650 °C) and their quantitative contribution. The pseudo second order kinetic model and the Langmuir model could fit the kinetic and isothermal adsorption data well, respectively. The intra-particle diffusion was the main rate-limiting step but not the only rate-limiting step. The maximum adsorption capacity obtained from the Langmuir model for CMB650 was 87.7 mg g-1 which was greater than those of other biochars. Precipitation with minerals, ion exchange, and complexation with functional groups (OFGs) were the main adsorption mechanisms. Quantum chemistry calculations confirmed that the functional groups (e.g., hydroxyl, carboxyl and C[double bond, length as m-dash]C) tended to bind with Zn2+ more strongly than with Ca2+ and Mg2+, because the structure of the complex formed by the former was more stable. The contribution of different adsorption mechanisms varied with the pyrolysis temperature to prepare biochar. With increasing pyrolysis temperature, the contribution of the interaction between Zn2+ and the minerals increased from 46.4% to 84.7%, while that of complexation with OFGs decreased from 41.7% to 4.7%. Overall, the mechanism of Zn2+ adsorption on CMB450 was dominated by complexation with OFGs and exchange with cations (accounting for 73.2%), while the mechanisms on CMB650 were dominated by the interaction with minerals. In view of the total adsorption capacity, 650 °C was the optimized pyrolysis temperature for CMBx preparation and adsorption treatment of Zn-contaminated water. These results are useful for screening effective biochars as engineered sorbents to treat Zn-containing wastewater.
ABSTRACT
OBJECTIVE: To investigate high risk human papillomavirus (HR-HPV) prevalence among married women in Beijing and to study the high risk factors. METHODS: During March 2007 to September 2008, a total of 6185 married women sampled from 137 communities in 12 districts were screened by HR-HPV DNA test and cytological test. The interview was carried out with unified questionnaires. The database was set up and twice entered in EpiData 3.0. After checked up, the data were analyzed in SPSS 15.0. RESULTS: (1) The HR-HPV infection rate was 9.89%. The HR-HPV infection rate of the city zone, the suburb and the exurb were 9.34%, 10.51% and 9.51% (P > 0.05). The HR-HPV infection rate of the native and the outlander were 9.53%, 11.30% (P < 0.05). (2) The age distribution of HR-HPV infection was that the rate was around 10% among 25 to 44 age groups, which was the highest (11.21%) in 30 to 34 age group; then the rate was descended as the age raising, the rate of 50 to 54 age group was the lowest (7.78%). (3) Multiple logistic regression showed that the related risk factors of HR-HPV infection mainly included 1000 RMB and above of family income per person per month, possessing more than 1 sexual partner of her husband, outlander and high levels of education. (4) The prevalence of cervical intraepithelial neoplasia (CIN) in HR-HPV positive group was significantly higher than that in HR-HPV negative group (29.76% vs 3.32%, P < 0.01). CONCLUSIONS: (1) The HR-HPV infection rate among aged 25 to 54 years was 9.9% and there was no significant difference in area distribution. (2) The high risk population which should strengthen screening was the married bearing-age women with high level of family income, outlander, high levels of education and her husband possessing more than 1 sexual partner. (3) HR-HPV infection is the main risk factor for CIN and cervical cancer, while does not provide a causal relationship with them. The high risk population should be checked regularly to understand the development of HR-HPV infection and CIN incidence.