MTE water remediation using Loy Yang brown coal as a filter bed adsorbent

Abstract

The future development of a non-evaporative brown coal dewatering technique called Mechanical Thermal Expression (MTE) will produce large volumes of acidic, salty and organic rich product water. The overall viability of the MTE process will, in turn rely on the availability of a simple and energy-efficient water remediation strategy. Water treatment using the feed coal itself as an adsorbent may provide such an option. In this study a fixed-bed configuration of raw Loy Yang coal was employed. When the adsorbent was first exposed to MTE water, most of the dissolved organic carbon (DOC) and most of the multivalent cations in solution were adsorbed. However, breakthrough of monovalent cations occurred after a volume of MTE water equivalent to just two times the volume of the adsorbent bed itself (2 bed volumes (BVs)) had passed, with only small proportions of Na and K being retained. About 60% (30 mg/g, db) of the dissolved organic carbon (DOC) and about 25% (0.16 mmol/g, db) of the total cations were removed after passing 20 BV of MTE water through the adsorbent bed. This corresponds to an adsorbent requirement that is 1.4% of the amount of coal to be dewatered. Thus, the use of brown coal adsorbent beds may be an effective primary water treatment option. However specific organic and inorganic components are likely to require further reduction prior to discharge to the environment.