An Evaluation of Various Carbonaceous and Synthetic Adsorbents for the Treatment of Sulfolane

Sulfolane (2,3,4,5-tetrahydrothiophene-1,1-dioxide) is an industrial solvent used in a variety of applications including in synthetic chemistry, electric and electrical circuit processing, and in the oil and gas industry.The most popular application of sulfolane is for the extraction of aromatic hydrocarbons and sweetening of natural gas in which sulfolane is mixed with alkanolamines (such as diisopropanolamine) as well as other organic substances.Improper handling, storage, and disposal of pure sulfolane solvent and sulfolane-containing wastes have created contaminated sites where the concentration of sulfolane can be hundreds of mg/L.Sulfolane is miscible with water, non-volatile, does not adsorb to mineral surfaces to an appreciable extent, and does not biodegrade quickly under conditions where nutrients and oxygen are limited.As such, once sulfolane is released into the subsurface it will travel long distances and create large contamination plumes that can be difficult to contain and mitigate.Sulfolane in groundwater systems and private wells have been detected in Canada, the US, Australia, and other countries.While sulfolane's toxicity and the risk that it can pose to human health are not thoroughly understood, residences whose drinking water wells containing detectable levels of sulfolane (0.01 mg/L -1 mg/L) have been put under water advisories.Therefore, there is an urgent need to develop treatment technologies capable of cleaning up sulfolane-contaminated sites and removing sulfolane from drinking water to protect water resources and human health.The overall objective of this research was to investigate the adsorption of sulfolane on a wide variety of natural and synthetic adsorbents, including sand, iron oxide, aluminum oxide, eight types of granular activated carbons (GAC), Ambersorb 560, Optipore L493, silica gel, zeolite, and silica gel.The removal of sulfolane by these materials were iii investigated by employing synthetic solutions and authentic groundwater samples spiked with 1 -500 mg/L of sulfolane.In some experiments, the solution also consisted of either diisopropanolamine or benzene (i.e., co-contaminants).A pre-screening test indicated that GACs, Ambersorb 560, and Optipore L493 possessed the highest sulfolane adsorption capacity.These materials were tested further in a series of experiments that aimed to examine the kinetics of sulfolane adsorption, adsorption isotherm, and effects of cocontaminants and other water chemistry conditions on the adsorption.It was observed that while the adsorption capacity of GACs and Ambersorb 560 were comparable, the adsorption equilibrium was established much faster on GACs (less than 24 hours) than on Ambersorb 560 (over 10 days).It was also observed that sulfolane adsorption was influenced by major divalent cations in groundwater (e.g., calcium, and magnesium) and dissolved organic carbon.Additionally, it was observed that diisopropanol amine and benzene inhibited sulfolane adsorption, although the degree of inhibition varied among adsorbents.Overall, the research suggests that the treatment of sulfolane by adsorption is a feasible approach for the treatment of contaminated groundwater by pump and treat (i.e., ex situ treatment).Although the research focused particularly on treating sulfolanecontaminated source zones where the concentration of sulfolane and other co-contaminants can range from a few mg/L to up to a few hundred mg/L, the knowledge generated can be relevant to the treatment of water systems with low contamination levels (i.e., less than 1 mg/L).Another objective of this research was to develop a simple, robust, and sensitive method for the analysis of sulfolane in aqueous solution based on prepping samples by isotopic dilution and liquid-liquid extraction, followed by analysis by Gas-Chromatography Mass List of Acronyms and AbbreviationsAC Activated carbon AS Ambersorb OP Optipore AL Amberlite DIPA Diisopropanolamine LD Lethal dose MDL Method detection limit MQL Method quantification limit GC Gas chromatograph LC Liquid chromatograph MS Mass spectrometry FID Flame ionization detection eCD Electron capture detection UV Ultraviolet UHPLC Ultra-high performance liquid chromatograph IC Ion chromatograph BTEX Benzene, toluene, ethylbenzene and xylene