Removal of polar and emerging organic contaminants by alternative adsorbents

The removal of polar and ionizable organic contaminants such as the fuel additive methyl tertiary butyl ether (MTBE) and pharmaceutically active compounds from drinking water sources is a challenge for many utilities. Effective treatment technologies are required to effectively remove these contaminants from drinking water. In this study the effectiveness of alternative adsorbents for the removal of MTBE and a mixture of 28 emerging contaminants was evaluated. Furthermore, adsorbent, adsorbate, and background water matrix characteristics that affect the adsorption of the antimicrobial compounds sulfamethoxazole (SMX) and trimethoprim (TMP) were identified.;In the first phase of this research, the MTBE removal effectiveness of activated carbon, a carbonaceous resin, and a silicalite zeolite was compared. 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 natural organic matter (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.;One activated carbon, one carbonaceous resin, and two high-silica zeolites were studied to evaluate their effectiveness for the removal of a mixture of emerging pollutants of concern (EPOCs) from lake water. Adsorption isotherm experiments were performed with environmentally relevant concentrations of the 28 targeted EPOCs (∼200--900 ng/L). Among the tested adsorbents, activated carbon was the most effective, and activated carbon doses typically used for taste and odor control in drinking water (1--10 mg/L) were sufficient to achieve a 2-log removal for most of the tested EPOCs. The results of this study demonstrate that heterogeneity in pore size and shape along with a large pore volume in the 6--9 A size range are important adsorbent characteristics when an effective barrier against a broad spectrum of EPOCs is desired.;Five carbonaceous adsorbents were evaluated to evaluate the pH-dependent adsorption uptake of sulfamethoxazole (SMX) and trimethoprim (TMP). Results indicated that a coconut shell-based activated carbon more effectively removed both antimicrobial compounds from ultra-pure water, Tar River water, and Lake Mead water than coal- and wood-based activated carbons and a carbonaceous resin. TMP and SMX were more effectively removed at solution pHs at which the antimicrobial compounds were primarily present in the neutral form. SMX and TMP adsorption isotherm data at different solution pHs could be effectively normalized by dividing the equilibrium liquid-phase concentration of SMX and TMP by the pH-dependent aqueous solubility provided that the solution pH was within about 2 pH units of the pKa. When the difference between the pKa and pH was larger, where repulsive electrostatic interactions proved to be important, the normalization procedure did not entirely account for the pH-dependence of the adsorption capacity of the ionizable organic compounds.