# Optimization for the COD reduction and thermodynamics research of coal-series kaolin

Authors
• 1 Southwest University of Science and Technology, Key Laboratory of Solid Waste Treatment and Resource Recycle Ministry of Education, Mianyang, 621010, China , Mianyang (China)
• 2 Wuhan University of Technology, School of Resource and Environment Engineering, Wuhan, 430070, China , Wuhan (China)
• 3 Yichang Huilong Science and Technology Co., Ltd, Yichang, 443004, China , Yichang (China)
Type
Published Article
Journal
Environmental Earth Sciences
Publisher
Springer-Verlag
Publication Date
Jun 12, 2019
Volume
78
Issue
12
Identifiers
DOI: 10.1007/s12665-019-8363-4
Source
Springer Nature
Keywords
Coal-series kaolin is the product of seam deposition in coal-accumulating basin, and may always contain reducing substances. The reducing substances such as carbon matter and pyrite could cause relatively high chemical oxygen demand (COD) of the raw kaolin, resulting in low quality kaolin products. In this study, narrow range classification and calcination were investigated to evaluate decreasing COD on coal-series kaolin from the Hubei Province. The kaolin and roasting products were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF) and thermogravimetry–differential scanning calorimetry (TG-DSC) analyses. The results showed that the COD value in kaolin ore (19,252 µg/g) was largely concentrated in the size fraction of – 150 to + 60 μm. The optimum conditions for reducing COD were identified to be – 74 to + 60 μm at a roasting temperature of 450 °C, and the COD value decreased from 27517 to 585 µg g−1. Moreover, the COD value and Ea showed linear correlation (R2 = 0.932) among different particle sizes, and G(α) = 1-1-α1212\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\left[ {1 - \left( {1 - \alpha } \right)^{{\frac{1}{2}}} } \right]^{{\frac{1}{2}}}$$\end{document} could be regarded as the most possible mechanism function for the thermal decomposition of coal-series kaolin.