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 study the effects of genistein (GEN) on reproductive system in prepubertal male rats. METHODS: Thirty SPF-rated male SD rats were randomly divided into control group (Con group), low-dose group (G1 group) and high-dose group (G2 group), with 10 rats in each group. Corn oil, 150 mg/kg and 300 mg/kg GEN dissolved in corn oil of equal volume were respectively administered every day and weighed the next day. After 6 weeks, the rats were sacrificed, and the testis, epididymis and prostate were dissected, and organ coefficients were calculated. Histopathological changes of testis was observed. The number of sperm was counted and the rate of sperm malformation was calculated. The concentrations of serum testosterone and estradiol were detected by radioimmunoassay. The protein phosphatase 2, regulatory subunit B, gamma (PPP2R2C) protein expression in testicular tissue was detected by immunofluorescence assay. The mRNA and protein expression levels of PPP2R2C and cyclin dependent protein kinases 2 (CDK2) in rat testis were detected by real-time quantitative fluorescence PCR (RT-qPCR) and Western blot, respectively. The protein phosphatase 2A (PP2A) activity in testicular tissue was detected by immunoprecipitation. RESULTS: There were no statistically significant differences in body mass, sperm number, serum estradiol and PP2A enzyme activity among the groups ( P>0.05). The pathological structure of testicular in G2 group was disordered. Sperm abnormality rate in G1 and G2 groups was higher than that in Con group ( P<0.05). Serum testosterone concentration in G2 group was lower than that in Con group ( P<0.05). The expression of PPP2R2C and CDK2 in G2 group was higher than that in Con group ( P<0.05), but the protein level was lower than that in Con group ( P<0.05). PPP2R2C protein was expressed in testicular tissue in each group. CONCLUSION: Long-term exposure to high dose (300 mg/kg) GEN during prepuberty may cause adverse effects on reproductive function in adult male rats. Further investigation is needed to determine whether PPP2R2C-PP2A-CDK2 phosphorylation pathway affects reproductive system in rats.
