Removal of naphthenic acids using adsorption process and the effect of the addition of salt

Abstract

In this study, various types of adsorbents were examined for the removal of Naphthenic acids (NAs) in the preliminary stage of this study. Among them, activated carbon and nickel (Ni) based alumina (Ni-Al₂O₃) possess relatively high adsorption capacity of NAs. The removal of NAs was evaluated comparing the total organic carbon (TOC) of the solution before and after the adsorption process. The effect of Ni loading was investigated using Ni-Al₂O₄ with various nickel loadings. The highest adsorption capacity (20 mg of TOC/1 mg of adsorbent) was belong to Ni-Al₂O₄ with 10.7% Ni loading. By the addition of salt (1500 ppm NaCl) to NAs solutions having concentrations from of 15 to 38 ppm, it was observed that the adsorption decreased dramatically (up to 80%) depending on the concentration of TOC. The kinetics of the adsorption of TOC on Ni-based alumina was also investigated. The decrease of TOC was more that 40% in the first half hour, indicating that adsorption was very rapid in the beginning. The adsorption increased slightly for up to 5 h and then leveled off when the TOC reached to 50% of initial TOC concentration. However, when sodium chloride (NaCl) was added to the solution, the adsorption decreased to almost 9% within the first half hour, reaching to almost 5% after 3 h. These phenomena suggest that the effectiveness of adsorbents may be improved by decreasing the total dissolved salts in tailings pond wastewater.

Keywords:

• Wastewater treatment
• naphthenic acids
• tailing ponds
• adsorption
• desalination

Acknowledgments

Financial support provided by the Canadian Natural Science and Engineering Research Council (NSERC-Engage Grants), Canadian Clean Water Technologies Incorporation (CCWTi), Institute for Sustainable Energy, Environment and Economy (ISEEE), and Centre for Environmental Engineering Research and Education (CEERE) are acknowledged.