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| Adsorption characteristics of ciprofloxacin on saline-alkali soil |
| Received:February 17, 2016 |
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| KeyWord:ciprofloxacin;saline-alkali soil;adsorption;pH value;Ca2+ concentration |
| Author Name | Affiliation | E-mail | | BIAN Wei-tao | School of Resource and Environment Science, Jilin Agricultural University, Changchun 130118, China
Key Laboratory of Soil Resource Sustainable Utilization for Jilin Province Commodity Grain Bases, Changchun 130118, China | | | MA Xiu-lan | School of Resource and Environment Science, Jilin Agricultural University, Changchun 130118, China
Key Laboratory of Soil Resource Sustainable Utilization for Jilin Province Commodity Grain Bases, Changchun 130118, China | 1974malan@163.com | | WAN Fu-min | School of Resource and Environment Science, Jilin Agricultural University, Changchun 130118, China
Key Laboratory of Soil Resource Sustainable Utilization for Jilin Province Commodity Grain Bases, Changchun 130118, China | | | ZHANG Li-yuan | School of Resource and Environment Science, Jilin Agricultural University, Changchun 130118, China
Changchun Monitoring Station of National Water Quality Monitoring Network, Changchun 130041, China | | | REN Li-jie | School of Resource and Environment Science, Jilin Agricultural University, Changchun 130118, China
Key Laboratory of Soil Resource Sustainable Utilization for Jilin Province Commodity Grain Bases, Changchun 130118, China | | | WANG Yu-jun | School of Resource and Environment Science, Jilin Agricultural University, Changchun 130118, China
Key Laboratory of Soil Resource Sustainable Utilization for Jilin Province Commodity Grain Bases, Changchun 130118, China | | | GAO Di | School of Resource and Environment Science, Jilin Agricultural University, Changchun 130118, China
Key Laboratory of Soil Resource Sustainable Utilization for Jilin Province Commodity Grain Bases, Changchun 130118, China | |
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| Abstract: |
| Adsorption isotherms, adsorption kinetics and adsorption thermodynamics of ciprofloxacin on a saline-alkali soil were investigated by batch equilibrium studies according to DECD Guideline 106. The effects of pH and Ca2+ concentration on adsorption process were also examined. Results indicated that the adsorption isotherm of ciprofloxacin was well fitted to the Freundlich equation, with correlation constant R2 of 0.981. The kinetics of ciprofloxacin adsorption by saline-alkali soil at different initial concentrations was in accordance with the pseudo-second order kinetic equation, with adsorption constant of 1.17×10-3~5.67×10-3 kg·min-1·mL-1. The whole process of ciprofloxacin adsorption by soil can be divided into two stages:the fast adsorption and the slow equilibrium. The adsorption equilibrium time of ciprofloxacin at initial concentrations of 80 mg·L-1, 100 mg·L-1 and 120 mg·L-1 was 24 h. The equilibrium adsorption ratios were 89.9%, 92.2% and 92.7%, respectively. The ΔH values of -3.585 kJ·mol-1 and negative ΔG values revealed that the adsorption of ciprofloxacin on the saline-alkali soil was a spontaneous exothermic process. The capacity of ciprofloxacin adsorption decreased constantly with increasing pH, and reduced drastically when pH was above 9. At different concentrations of CaCl2 as background solution, the isothermal adsorption curves of ciprofloxacin by saline-alkali soil were well described by the Freundlich equation. The lgKf values decreased with the increase of CaCl2 concentration. The impact of ionic strength on ciprofloxacin adsorption was less when its initial concentrations were lower. |
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