MTBE adsorption on alternative adsorbents and packed bed adsorber performance

Abstract

Widespread use of the fuel additive methyl tertiary-butyl ether (MTBE) has led to frequent MTBE detections in North American and European drinking water sources. The overall objective of this research was to evaluate the effectiveness of a silicalite zeolite, a carbonaceous resin, and a coconut-shell-based granular activated carbon (GAC) for the removal of MTBE from water. Isotherm and short bed adsorber tests were conducted in ultrapure water and river water to obtain parameters describing MTBE adsorption equilibria and kinetics and to quantify the effect of natural organic matter (NOM) on MTBE adsorption. Both the silicalite zeolite and the carbonaceous resin exhibited larger MTBE adsorption uptakes than the tested GAC. Surface diffusion coefficients describing intraparticle MTBE mass transfer rates were largest for the GAC and smallest for the carbonaceous resin. Pilot tests were conducted to verify MTBE breakthrough curve predictions obtained with the homogeneous surface diffusion model and to evaluate the effect of NOM preloading on packed bed adsorber performance. Results showed that GAC was the most cost-competitive adsorbent when considering adsorbent usage rate only; however, the useful life of an adsorber containing silicalite zeolite was predicted to be ∼5–6 times longer than that of an equally sized adsorber containing GAC. Pilot column results also showed that NOM preloading did not impair the MTBE removal efficiency of the silicalite zeolite. Thus, it may be possible to regenerate spent silicalite with less energy-intensive methods than those required to regenerate GAC.