Purification of Coal-Bed Methane Produced Water by Zeolite Membranes

Abstract

Abstract This paper reports a new method for purification of coal-bed methane (CBM) produced water by reverse osmosis (RO) through molecular sieve MFI zeolite membranes. The desalination on the zeolite membrane can be thought of as an ion sieving process — the uniform zeolitic pore size (dia. ~0.56nm for MFI) is sufficient for transport of water molecules (dynamic size ~0.29nm) but is small enough to reject hydrated ions and large organic molecules by size exclusion. In this study, the MFI zeolite membranes were used for desalinating a CBM produced water from Farmington, NM, which contained total dissolved salts (TDS) of ~1.86×104 ppm. The effect of dissolved organics on the desalination efficiency was examined by comparing RO performance for 0.10M KCl solutions with and without dissolved toluene, which was used as a simulator of dissolved organics. The zeolite membrane showed an overall salt rejection of 83.5% for the CBM produced water with organics removed by pretreatment. Experimental results also show that the dissolved toluene affected the ion rejection and water flux only slightly. Due to its extraordinary chemical and structural stabilities, the MFI zeolite membrane may offer an alternative method to treat the organic-containing, high TDS CBM produced water for beneficial use.