Effect of Na₂CO₃ Roasting Activation on Acid Leaching Property of Fly Ash

Abstract

By using high-alumina fly ash as raw material, a process was proposed for activating the fly ash with Na₂CO₃ calcination and extracting aluminum from activated clinker with sulfuric acid leaching. The feasibility of roasting process of activated fly ash by Na₂CO₃ was discussed based on thermodynamic analysis. The experimental results showed that Na₂CO₃ gradually reactes with mullite over 700 K to produce NaAlSiO₄. The optimal process conditions for the activation stage are: a material ratio of 1:1 between sodium carbonate and fly ash, a calcination temperature of 900 °C, and a calcination time of 2.5 hours. Under these conditions, the leaching rate of aluminum is 90.3%. By comparing the SEM and XRD analysis of raw and clinker materials, it could be concluded that the mullite phase of fly ash is almost completely destroyed and transformed into sodium aluminosilicate with good acid solubility.

Keywords

fly ash / calcination activation / acid leaching / aluminum

References

[1] Liang L. BP Releases the Statistical Report on World Energy 2022[J]. World Petroleum Industry, 2022, 29(04): 78

[2] Liu CL. Fundamental Applied Research on the Separation of Alumina and Silica from High Alumina Fly Ash[D], 2019, Beijing: University of Chinese Academy of Sciences (Institute of Process Engineering, Chinese Academy of Sciences)

[3] Zheng FW. Study on the Leaching Process and Kinetics of Aluminum and Iron from Fly Ash[D], 2018, Kunming: Kunming University of Science and Technology

[4] Pan JH. Study on the Enrichment, Extraction, and Mechanism of Occurrence of Rare Earth Elements in Coal Fly Ash[D], 2021, Xuzhou: China University of Mining and Technology

[5] Xu DH. Fundamental Research of Extracting Alumina from High-Alumina Coal Fly Ash Using NH ₄ HSO ₄/H ₂ SO ₄ Mixed Solution[D], 2017, Beijing: University of Chinese Academy of Sciences (Institute of Process Engineering, Chinese Academy of Sciences)

[6] Bhangare RC, Tiwari M, Ajmal PY, et al. Distribution of Natural Radioactivity in Coal and Combustion Residues of Thermal Power Plants[J]. J. Radioanal Nucl. Chem., 2014, 300: 17-22

[7] Lei XF, Qi GX, Sun YI, et al. Removal of Uranium and Gross Radioactivity from Coal Bottom Ash by CaCl₂ Roasting Followed by HNO₃ Leaching[J]. J. Hazard Mater., 2014, 276: 346-352

[8] Whiteside M, Herndon JM. Coal Fly Ash Aerosol: Risk Factor for Lung Cancer[J]. J. Adv. Med. Med. Res., 2018, 25(4): 1-10

[9] Wei LH, Ye NJ, Zhu CF, et al. Effects of Air Exposed Coal Fly Ash on Groundwater Contamination[J]. J. Geol., 2013, 19(4): 683-691

[10] Gong X, Yao H, Zhang D, et al. Leaching Characteristics of Heavy Metals in Fly Ash from a Chinese Coal-fired Power Plant[J]. Asia-Pacj J. Chem.Eng., 2010, 5(2): 330-336

[11] Jiao FC, Zhang L, Dong ZB, et al. Study on the Species of Heavy Metals in Msw Incineration Fly Ash and Their Leaching Behavior[J]. Fuel Process. Technol., 2016, 152: 108-115

[12] Hao YY, Hao F, Chen JF, et al. The Impact of Power Plant Fly Ash Storage on Water Environment and Prevention Measures[J]. Shanxi Water Conservancy, 2010, 26(11): 19-21

[13] González A, Navia R, Moreno N. Fly Ashes from Coal and Petroleum Coke Combustion: Current and Innovative Potential Applications[J]. Waste Manage Res., 2009, 27(10): 976-987

[14] Jin SS, Yang JL, Li P. Evolution of Pore Structure and Fractal Dimension of Fly Ash Cement Mortar[J]. Concrete, 2020(7): 99–102

[15] Dai YL, Sun SW, Liu YT, et al. The Current Research Status of Comprehensive Utilization of Fly Ash in the Cement Industry[J]. Anhui Construction, 2019, 26(10): 198-201

[16] Wang YJ, Li Z Qin Y, et al. Effect of Replacement Rate of Recycled Coarseaggretrate on Compressive Strength of Concrete[J]. Concrete, 2018, (12): 27–30

[17] Xue SH. The Method of Lime Sinter Process to Produce Aluminum[D], 2010, Xi’an: Xi’an University of Architecture and Technology

[18] Zhang ZY, Qiao XC, Yu JG. Aluminum Release from Microwave-Assisted Reaction of Coal Fly Ash with Calcium Carbonate[J]. Fuel Process. Technol., 2015, 134: 303-309

[19] Chen YX, Yang G, Zhao B, et al. Alumina Extraction from High-Alumina Fly Ash by Soda Lime Low Calcium Sintering[J]. Light Metal, 2018, (12): 12–15

[20] Shemi A, Ndlovu S, Sibanda V, et al. Extraction of Aluminium from Coal Fly Ash: Identification and Optimization of Influential Factors Using Statistical Design of Experiments[J]. Int. J. Miner. Process, 2014, 127: 10-15

[21] Aphane ME, Merwe EM, Frederic J, et al. The Effect of Sulphuric Acid Concentration on The Removal of Reactive Aluminium from South African Coal Fly Ash[J]. World of Coal Ash Conference in Nasvhille, 2015, 5(7): 5-7

[22] Zheng ML. Aluminum Extraction from Coal Fly Ash and Preparation of Adsorbent with the Acid Leaching Residue[D], 2021, Dalian: Dalian University of Technology

[23] Wang F, Ma HW, Xu JM, et al. Sintering Reaction of Nepheline Syenite: Thermodynamic Analysis and Experimental Study[J]. Mod. Geol., 2006, 20(4): 657

[24] Molina A, Poole C. A Comparative Study Using Two Methods to Produce Zeolites From Fly Ash[J]. Miner. Eng., 2004, 17(2): 167-173