Characterization of Liquid Products Obtained from Hot Water-Drying Treatment of Low Rank Coal and Their Ability of Cr(VI) Reduction

Liquid products produced in a hot water drying (HWD) process of Beluga low rank coal were characterized by GC/MS, HPLC, GPC, TOC measurement and cyclic voltammetry. The Beluga coal was treated at three different temperatures, namely 270, 300 and 330°C. The ability of the liquid products to reduce Cr(VI) was investigated by analyzing the solution containing the liquid and Cr(VI), using Fluorescence Spectrometry. With increasing treatment temperature TOC concentration of the liquid products became larger. The liquid product at 270°C contained acetic acid, acetic acid-methyl ester and oligomer. The oligomer mass was found to be 1,600∼3,400. The liquid product at 300 and 330°C contained catechol and phenol, and the liquid product at 330°C contain more catechol groups. The reduction behavior of both liquids obtained above 300°C was similar to that of catechol in cyclic voltammetry. All liquid products reduced the Cr(VI) to Cr(III), and their reduction ability became stronger with decreasing pH. For a solution containing high Cr(VI) concentration (2.7x10-2 mol/dm3) the liquid obtained at 330°C successfully reduced Cr(VI) to a concentration below the allowed level at pH 2. It was found by fluorescence spectroscopy that Cr(VI) was reduced due to catechol groups in the liquid products.