Article pubs.acs.org/EF
Characterization of “Chailings”: A Char Created from Coal Tailings Priscilla Tremain,† Jafar Zanganeh,† Lyndal Hugo,‡ Shane Curry,‡ and Behdad Moghtaderi*,† †
Newcastle Institute for Energy and Resources, Chemical Engineering, The University of Newcastle, Callaghan, New South Wales 2308, Australia ‡ BDM Resources, Hamilton, New South Wales 2303, Australia ABSTRACT: Coal tailings are a waste product of the coal mining process and consist primarily of gangue mineral matter and fine coal particles. In this study, coal tailings sourced from two Australian coal mines (Mine A and Mine B) were subjected to a slow pyrolysis process at temperatures of 400−800 °C to create char hereafter known as “chailings”. Chailings were originally conceptualized based on the concept of biochar and are a novel waste management strategy for coal tailings. Several methods were used to characterize chailings and quantify the effect of different pyrolysis conditions. X-ray diffraction (XRD) and X-ray fluorescence (XRF) techniques identified the primary mineral constituents as silica (i.e., quartz) and aluminosilicates (i.e., kaolinite or illite). Clear morphologic changes were observed via optical and scanning electron microscopy (SEM) for increasing pyrolysis temperature, with evidence of swelling and devolatilization apparent at high temperatures (>600 °C). Proximate analyses indicated near complete devolatilization was apparent at 800 °C for both mines, with thermogravimetric analysis (TGA) revealing that peak devolatilization occurred at 455 °C for Mine A and 467 °C for Mine B. A substantial increase in surface area with increasing pyrolysis temperature was observed for Mine A chailings from 2.7 m2/g at 400 °C to 75.3 m2/g at 800 °C, because of the presence of microporosity, while Mine B chailings decreased from 2.4 m2/g at 400 °C to 1.2 m2/g at 800 °C, which was attributed to macroporosity and aggregation of particles. Properties of high-temperature (>600 °C) chailings, namely, surface area, porosity, and pH offer promise for future investigations regarding the application of chailings to soil.
1. INTRODUCTION
biochars have been shown to possess, while also making use of a current waste product of the coal mining industry. A considerable number of biomass feedstocks have been used for the production of biochar including poultry manure,5−7 biosolids8,9 and agricultural/green waste.10−14 Numerous studies have been conducted in recent years into the production5,11−15 and performance of biochar as a soil ameliorant,5−8,10,16−23 with general consensus that positive outcomes can be attained through biochar application at varying rates. However, the economic viability of biochar to potential consumers is currently jeopardized by its relatively high cost and difficulty associated with attaining a sustainable biomass feedstock for large-scale biochar production. In contrast, the vast availability of coal tailings and its status as a waste product make it both a reliable and economically viable feedstock for the production of chailings. This study hypothesizes that the production of chailings can concomitantly reduce coal mine waste and provide a sustainable char feedstock for application to soils to benefit agriculture and mine site rehabilitation. In this paper, we present the fundamental characteristics of chailings as a foundation for future studies on the suitability of chailings for soil application. Chailings produced from two different tailings sources under different operating conditions were characterized via methods including proximate and ultimate analyses, pH, electrical conductivity (EC), thermogravimetric analysis (TGA), Brunauer−Emmett−Teller (BET) adsorption, scanning electron microscopy (SEM), optical microscopy, X-ray
Waste and land management are ever-present issues in modern society. These challenges are commonly faced by coal mining companies, in particular, when dealing with coal tailings. Coal tailings are the fine (
