Reversible Solubilization of Typical Polycyclic Aromatic Hydrocarbons (PAH) by a Gas Switchable Surfactant

Surfactant-enhanced remediation (SER) is one of the most effective remediation methods for polycyclic aromatic hydrocarbons (PAH) contaminated soils. However, mass deployment of SER has been restricted due to the shortage of the separation, recycle technology of the surfactant and its operation costs. This research mainly studied the reversibility of 2-n-lauryl-1,1,3,3-tetramethyl guanidine (DTMG) surfactant and its influence on reversible solubilization of typical PAH. Experimental results showed that the reversibility of the DTMG surfactant is excellent. The critical micellar concentration (CMC), surface tension and pH of DTMG in CO2/N-2 conditions undergo reversible changes promptly. DTMG center dot CO2 shows a strong solubilization capacity for PAH; the apparent solubilities of the selected PAH pyrene, phenanthrene and anthracene in 4 mmol/L of DTMG center dot CO2 solution were about 32.4, 17.1 and 14.6 times higher than in water, respectively. The corresponding molar solubilization ratios were 5.4 x 10(-3), 2.80 x 10(-2) and 1.1 x 10(-3), much higher than those with DTMG. More than 50 % of the PAH in surfactant solutions could be released through gas control at each surfactant concentration, and improved release efficiency was achieved at low surfactant concentrations. In brief, such results in this work introduce a facile method to meliorate the SER technology.