Removal Of Polycyclic Aromatic Hydrocarbons From Surfactant Solution By Selective Sorption

Surfactant-enhanced washing has been suggested as an effective and promising technology for the remediation of organic-contaminated soils/sites. However, large volumes of washing effluents containing the surfactant and hydrophobic organic compounds (HOCs) would be generated during the surfactant-enhanced washing process. Recovering and then recycling the washing effluents is required to reduce operating costs and prevent secondary contamination. In this thesis, the technologies for recovering surfactant washing effluents were reviewed. The selective sorption treatment for surfactant solutions recovery was further studied. First, the sorption effectiveness and mechanisms of mixed polycyclic aromatic hydrocarbons (PAHs) onto activated carbons and organo-bentonite in surfactant solutions were investigated. Then, the performance and the mathematical prediction method of the fixed-bed packed with activated carbon for surfactant solutions recovery was studied. The main original conclusions are drawn as follows:(1) Competitive sorption of PAHs onto activated carbon was found in surfactant solutions, which can reduce the sorption capacity of activated carbon for PAHs. The competitive sorption between PAHs occurred on the solid-sorbed surfactant, and the competitive power of PAHs possessed positive correlation with their hydrophobicity.(2) The activated carbon fixed-bed columns can selectively remove phenanthrene from surfactant solutions in a high proportion relative to the sorption losses of the surfactant. The high bed heights and low flow rates both are favorable for fixed bed to achieve higher sorption selectivity, but the influent phenanthrene concentration showed little effect on the selective sorption. Based on the constant-pattern model and the apparent partition coefficient of the HOCs between the solid and aqueous phases, a mathematical method was established to describe and predict the dynamic sorption process of the surfactant and HOCs, which can provide reference for practical application of fixed bed to recover the surfactant washing effluents.