Cation exchange properties of heat-treated Australian brown coal: influences of pre-exchanged calcium ions

摘要

Loy Yang brown coals, Australia, with pre-exchanged calcium ions (Ca-LY) or without pre-exchanged calcium ions (LY) were heat-treated at a desired temperature between 50 and 400 degreesC and their exchanged amounts of Co2+ or Mg2+ were measured as a function of pH of the aqueous solution. The exchanged amount of divalent cations for Ca-LY heat-treated at 50 degreesC was larger than that for LY heat-treated at the, same temperature over the whole pH range. In the low pH region between 2 and 4.5, the exchanged amount of divalent cations for LY heat-treated above 250 degreesC was almost zero, while that for Ca-LY heat-treated at the higher temperature such as 300 degreesC was 0. 1 -0.3 mmol g(-1). These results were discussed based on the amounts and the types of the carboxyl groups present on the heat-treated brown coal surfaces. (C) 2001 Elsevier Science B.V. All rights reserved. [References: 24]