Optimization of Ex-Situ Washing Removal of Polycyclic Aromatic Hydrocarbons from a Contaminated Soil Using Nano-Sulfonated Graphene

Ex-situ soil washing technology offers advantages such as speed and efficiency of remediation and range of application and has been developed to conform with legal requirements and best management practices in USA and some European countries. In this study, nano-sulfonated graphene (SGE) was used as a washing agent to evaluate different processing (washing) parameters for the ectopic leaching removal of polycyclic aromatic hydrocarbons (PAHs) from a coking plant soil. X-ray photoelectron spectroscopy (XPS) and fourier transform infrared spectroscopy (FTIR) were used to analyze the characteristics of the SGE tested. The results showed that SGE had a strong adsorption capacity for PAHs through the role of pi-pi, H-pi, and anion-pi interactions. The washing parameters, an SGE concentration of 2 000 mg L-1, a liquid/soil (L/S) ratio of 10:1, and 4 cycles of successive washing, were set to arrive to the optimum condition for achieving more than 80% of PAH removal. Under the optimum condition, the PAH removal rate decreased with increasing ring numbers. After one washing cycle at SGE concentration of 2 000 mg L-1 and L/S ratio of 10:1, the PAH removal rate of the SGE tested was much higher than that of Tween 80 (TW80) or methyl-beta-cyclodextrin (MCD) (P < 0.01). Therefore, SGE is a promising material for the nanoremediation of PAH-contaminated soils.