Cosolvency Effects of Monoethanolamine and Triethanolamine: Implications for the Remediation of Benzene in Groundwater at Sour-Gas Plants

Abstract

Studies were conducted to measure the cosolvency effect of monoethanolamine (MEA) and triethanolamine (TEA) on the aqueous solubility of benzene in support of the remediation of contaminated subsurface environments at gas plants in western Canada. Experiments utilized sodium chloride solutions of the amines in the concentration range of 0–0.065 volume fractions, and non-saline waters in the range 0–1 volume fractions. The measured values of the cosolvency power σ for MEA and TEA, based on the log-linear model, were 1.86 ± 0.05 and 2.21 ± 0.04, respectively. The corresponding values for the semi-cosolvency power σ0.5 were 1.22 ± 0.005 and 1.19 ± 0.005, respectively. It is postulated that the difference in the values of σ and σ0.5 may be linked to cosolvent polarity of the amines in water. In 0.2 Mol/L NaCl saline water, the solubility of benzene increased linearly from 1660 mg/L to 2170 mg/L and 1960 mg/L for cosolvents MEA and TEA (0–0.065 volume fractions), respectively. As evidenced by the measured 30% increase in the solubility of benzene, remediation strategies of groundwater at sour-gas plants should therefore take into account the levels of these amines and their effects on the transport of hydrocarbon contaminants.