1 Department of Building, Civil and Environmental Engineering, Concordia University, Montreal, H3G 1M8, Canada.
2 Department of Building, Civil and Environmental Engineering, Concordia University, Montreal, H3G 1M8, Canada. Electronic address: chunjiang.an@concordia.ca.
3 Department of Chemical and Materials Engineering, Concordia University, Montreal, H3G 1M8, Canada.
4 The Northern Region Persistent Organic Pollution (NRPOP) Control Laboratory, Faculty of Engineering and Applied Science, Memorial University, St. John's, A1B 3X5, Canada.
5 College of Environmental Science and Engineering, North China Electric Power University, Beijing, 102206, China.
6 Faculty of Engineering and Applied Science, University of Regina, Regina, S4S 0A2, Canada.

Oil pollution is one of the major environmental concerns in the petroleum industry. In this study, a cheap food-grade sodium caseinate (NaCas) was used as a pH-responsive washing fluid in the remediation of phenanthrene (PHE) affected peat moss. The effects of environmental factors on the removal of PHE were systematically investigated. The results showed that increasing NaCas concentration and washing temperature improved the PHE mobilization, while high salinity and humic acid dosage displayed a negative effect. The factorial analysis revealed that three individual factors and two interactions exhibited significant effects on the washing performance. Due to the pH-responsive property of NaCas, the turbidity, total organic carbon (TOC), and chemical oxygen demand (COD) of the washing effluent were remarkably reduced by simply adjusting the solution acidity, improving the practical application of such a washing method. Significantly, the toxicity modeling proved that NaCas can reduce the binding energy between PHE and superoxide dismutase (SOD) of the selected marine organism, and thus relieve the toxicity of PHE to the organisms. Given these advantages, NaCas-assisted washing can be a viable option for the remediation of contaminated peat moss.