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| Adsorption of Toluene on Different Substrates for Constructed Wetland |
| Received:July 25, 2014 |
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| KeyWord:toluene;constructed wetland;substrate;adsorption |
| Author Name | Affiliation | E-mail | | WANG Yu-jie | School of Environmental and Chemical Engineering, Tianjin Polytechnic University, Tianjin 300387, China | | | TANG Yun-ping | School of Environmental and Chemical Engineering, Tianjin Polytechnic University, Tianjin 300387, China
Tianjin Academy of Environmental Science, Tianjin 300191, China | 13652097098@163.com | | GU Xiu-jun | Tianjin Harbor Economic Area, Tianjin 300460, China | | | LIU Hong-lei | Tianjin Academy of Environmental Science, Tianjin 300191, China | | | SHI Yan | Tianjin Academy of Environmental Science, Tianjin 300191, China | | | DUAN Yun-xia | Tianjin Academy of Environmental Science, Tianjin 300191, China | |
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| Abstract: |
| Constructed wetlands are a low-cost and easy-operation technology for treating low concentration organic substance wastewater. The present study compared the adsorption and removal efficiency of toluene by volcanic, natural zeolite and gravel. The results showed that the equilibrium time of toluene adsorption on three substrates were 12 h. Both Freudlich and linear isotherms could be used to fit toluene adsorption. The adsorption capacities of three substrates for toluene were:natural zeolite≈volcanic > gravel; E(mean free adsorption energy)of toluene for each substrate obtained by Dubinin-Radushkevich equation was less than 8 kJ·mol-1, implying that the toluene adsorption was physical process. With the particle size of substrates increasing, the toluene adsorption by volcanic and zeolite changed little, while that of gravel sharply decreased. The removal efficiency of toluene from water was obviously greater in volcanic and natural zeolite systems than in gravel system. When the Hydraulic Retention Time(HRT) was 2 d, the toluene concentration in the wastewater satisfying the third grade Integrated Wastewater Discharge Standard(GB 8978-1996)(≤0.5 mg·L-1) could meet the first grade standard(≤0.1 mg·L-1) for the volcanic and natural zeolite systems, whereas the toluene removal rate in the gravel system was only 12%~16%. |
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