Removal of roxarsone from aqueous solution by Fe/La-modified montmorillonite

Abstract

Roxarsone is an organoarsenical compound widely used as a feed additive in animal husbandry and might result in the contamination of inorganic arsenic in aquatic environment. Montmorillonite is an economical adsorbent with many advantages. In this study, Fe/La-modified montmorillonite (Fe/La-Mt) was prepared, characterized, and investigated for the removal of roxarsone from aqueous solutions. Brunauer–Emmett–Teller (BET) analysis confirmed the increase in specific surface area and pore volume of montmorillonite after modification. FESEM analysis showed that Fe/La-Mt formed flake structure and the structure was collapsed after being calcined (C-Fe/La-Mt). The adsorption results indicated that the adsorption capacity of Fe/La-Mt onto roxarsone is higher than that of C-Fe/La-Mt. The adsorption process of roxarsone onto Fe/La-Mt and C-Fe/La-Mt can be well described using pseudo-second-order model and interpreted using the Langmuir isotherm. Thermodynamic analysis indicated that the adsorption was a spontaneous and endothermic process. The adsorption capacity reduced slightly when solution pH increased from 2.5 to 8.0. The ion of greatly decreased the adsorption of roxarsone onto Fe/La-Mt. X-ray photoelectron spectroscopy analysis confirmed the loading of arsenic (V) onto the surface of Fe/La-Mt. The high adsorption capacity in a wide pH range demonstrated that Fe/La-Mt can be used potentially for the removal of roxarsone from aqueous solution.

Keywords:

• Adsorption
• Fe/La-modified montmorillonite
• Removal
• Roxarsone

Acknowledgements

This research was partly supported by the NSFC (51578205, 51538012), the Science and Technology Innovation Fund from Beijing Academy of Agriculture and Forestry Sciences (CXJJ201317), and the Program for Cultivating Excellent Talents in Beijing (2013D002020000001).