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| Adsorption and Desorption of Ciprofloxacin by Surface and Subsurface Soils of Ustic Cambosols in China |
| Received:June 04, 2014 |
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| KeyWord:ciprofloxacin;ustic cambosols;absorption;desorption;pH |
| Author Name | Affiliation | E-mail | | GUO Li | College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China | | | WANG Shu-ping | College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China | wshuping@ucas.ac.cn | | ZHOU Zhi-qiang | College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China | | | DONG Jun-fu | College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China | | | ZHAO Guo-qiang | College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China | |
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| Abstract: |
| The behaviors of antibiotics in soils have received increasing attention. In this study, batch adsorption method was employed to reveal adsorption and desorption of antibiotic ciprofloxacin by two different layer soils of ustic cambosols, 0~20 cm surface and 20~40 cm subsoil, following OECD guideline 106. Results showed that the absorption and desorption processes of ciprofloxacin can be divided into two stages:fast reaction and slow balance, and followed the pseudo-second-order kinetics,with adsorption rate of 0.571 kg·min-1·mg-1. After 24 h the absorption and desorption reached balance. Freundlich model best described all experimental data of adsorption and desorption(P<0.01). The adsorption capacity(Kf) was 672.977 and 693.426 for surface and subsurface soils, respectively. The mechanism of ciprofloxacin adsorption was primarily physical adsorption in soils. There was hysteresis in desorption. Hysteresis index(HI) of ciprofloxacin increased with increasing initial concentration. The HI was greater in 0~20 cm than in 20~40 cm soil layer. In adsorption, lg Kd values increased with pH increasing from 4 to 5 and then reduced with further increase in pH, with absorption peak appeared at pH 5, The lg Kd value at pH 5 was 3.36 for 0~20 cm soil layers and 3.90 for 20~40 cm soil layers. In conclusion, cationic adsorptions might be one of the main sorption mechanisms for ciprofloxacin in two soil layers. |
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