This study evaluated the individual and interactive effect of phenol and thiocyanate (SCN−) on partial nitritation (PN) activity using batch test and response surface methodology. The IC50 of phenol and SCN− on PN sludge were 5.6 and 351 mg L−1, respectively. The PN sludge was insensitive to phenol and SCN− at levels lower than 1.77 and 43.3 mg L−1, respectively. A regression model equation was developed and validated to predict the relative specific respiration rate (RSRR) of PN sludge exposed to different phenol and SCN− concentrations. In the range of independent variables, the most severe inhibition was observed with a valley value (17%) for RSRR, when the phenol and SCN− concentrations were 4.08 and 198 mg L−1, respectively. An isobole plot was used to judge the combined toxicity of phenol and SCN−, and the joint inhibitory effect was variable depending on the composition and concentration of the toxic components. Furthermore, the toxic compounds showed independent effects, which is the most common type of combined toxicity.
Copper ions were first adsorbed by zeolite 4A synthesized from bauxite tailings, the desorption of Cu(II) using Na2EDTA solutions was performed, and the recycling of zeolite 4A in adsorption and desorption was systematically investigated. It was observed that the Cu(II) removal efficiency was directly dependent on the initial pH value. The maximum removal efficiency of Cu(II) was 96.2% with zeolite 4A when the initial pH value was 5.0. Cu(II) was completely absorbed in the first 30 min. It was also observed that the desorption efficiency and zeolite recovery were highly dependent on the initial pH and concentration of Na2EDTA in the solution. The desorption efficiency and percent of zeolite recovered were 73.6 and 85.9%, respectively, when the Na2EDTA solution concentration was 0.05 mol L?1 and the pH value was 8. The recovered zeolites were pure single phase and highly crystalline. After 3 cycles, the removal efficiency of Cu(II) was as high as 78.9%, and the zeolite recovery was 46.9%, indicating that the recovered zeolites have good adsorption capacity and can repeatedly absorb Cu(II).
Environmental Science and Pollution Research - Accurate and effective determination of the source of heavy metals is essential for the treatment of marine ecological environments. This article... 相似文献
Air–water exchange is an important process controlling the fate of many organic chemicals in the environment. Modeling this process is hampered by the lack of direct observations. Thus, the purpose of this work was to derive direct measurements of the mass transfer coefficients for air–water exchange (vaw) of polychlorinated biphenyls (PCBs) that may be used to check the validity of values derived from tracer gas experiments. vaw values for PCBs were determined using previously published turbulent fluxes divided by the corresponding dissolved phase concentrations. The median vaw values for each homolog decreased with increasing molecular weight and ranged from 0.29 for hexachlorobiphenyls to 2.2 m d?1 for monochlorobiphenyls with a propagated uncertainty of about 70%, lower than in previous studies. Due to relatively low wind speeds and possible sorption of PCBs to colloids, these numbers may be biased low. These field measurements of vaw differ by as much as a factor of 23 from predictions based on the widely-used Whitman two-film model. Therefore a new formulation for the calculation of vaw based on field measurements is needed. This study demonstrates that micrometeorological approaches are a viable option for the measurement of vaw for hydrophobic organics such as PCBs and should be used to generate enough field data on the air–water exchange of hydrophobic organics to allow the development of new predictive models. 相似文献