Adsorption of gas-phase n-hexane and benzene, toluene, ethyl benzene, and xylene onto compost; kinetics and isothermal studies
Mohammad Mehdi Amin1, Bijan Bina1, Amir Rahimi2, Mohsen Heidari3
1 Environment Research Center, Research Institute for Primordial Prevention of Non-communicable Disease, Isfahan University of Medical Sciences (IUMS), Isfahan, Iran and Department of Environmental Health Engineering, School of Health, IUMS, Isfahan, Iran
2 Chemical Engineering Department, College of Engineering, University of Isfahan, Isfahan, Iran
3 Department of Environmental Health Engineering, Student Research Center, School of Health, Isfahan University of Medical Sciences (IUMS), Isfahan; Department of Environmental Health Engineering, Faculty of Health, Hormozgan University of Medical Sciences, Bandar Abbas, Iran
Department of Environmental Health Engineering, Environment Research Centre, School of Health, Isfahan University of Medical Sciences, Hezar Jerib Ave, Isfahan
Source of Support: None, Conflict of Interest: None
Aims: In this study, the potential capability of compost in the simultaneous adsorption of gas-phase n-hexane and benzene, toluene, ethyl benzene, and xylene (BTEX) was studied.
Materials and Methods: Batch adsorption technique was used to assess the adsorption properties of compost. The pseudo-first and pseudo-second order kinetics were considered in order to identify the possible mechanism of the adsorption process. Moreover, the suitability of the adsorbent was evaluated using Langmuir, Freundlich and The Dubinin-Radushkevich isotherm models.
Results: After 24 h contact time, the adsorption capacity of one g compost was 1.42 mg n-hexane and BTEX for initial concentration of 7.74 mg/l. The adsorption capacities were in order of n-hexane < benzene < toluene < ethylbenzene < xylene. This order is in accordance to the ascending octanol-air partitioning coefficient (K OA ) order of the compounds (the lowest for n-hexane and the highest for xylene). The kinetics data proved a closer fit to the pseudo-second order model, while the isotherm experimental data were a good correlation to both Freundlich and Langmuir models.
Conclusion: The experimental data show that a material with an organic matrix, that is, raw compost, has a higher adsorption capacity for the gaseous compounds with higher K OA . Overall look to the results of this study indicates that although the raw compost could adsorb gaseous n-hexane and BTEX, its capacity may not be sufficient for the continuous removal of VOCs from the air in the compost-based biofilters, in which biodegradation play a key role.