Preparation of Al-Si Master Alloy by Electrochemical Reduction of Fly Ash in Molten Salt AIMIN LIU, 1 LIANGXING LI, 1 JUNLI XU, 2 ZHONGNING SHI, 1,3 XIANWEI HU, 1 BINGLIANG GAO, 1 ZHAOWEN WANG, 1 JIANGYU YU, 1 and GONG CHEN 1 1.—School of Materials and Metallurgy, Northeastern University, Shenyang 110004, People’s Republic of China. 2.—School of Science, Northeastern University, Shenyang 110004, People’s Republic of China. 3.—e-mail: znshi@mail.neu.edu.cn An electrochemical method on preparation of Al-Si master alloy was investi- gated in fluoride-based molten salts of 47.7wt.%NaF-43.3wt.%AlF 3 - 4wt.%CaF 2 containing 5 wt.% fly ash at 1233 K. The cathodic products obtained by galvanostatic electrolysis were analyzed by means of x-ray diffraction, x-ray fluorescence, scanning electron microscopy, and energy- dispersive spectrometry. The result showed that the compositions of the pro- ducts are Al, Si, and Al 3.21 Si 0.47 . Meanwhile, the cathodic electrochemical process was studied by cyclic voltammetry, and the results showed the reduction peak of aluminum deposition is at 1.3 V versus the platinum quasi-reference electrode in 50.3wt.%NaF-45.7wt.%AlF 3 -4wt.%CaF 2 molten salts, while the reduction peak at 1.3 V was the co-deposition of aluminum and silicon when the fly ash was added. The silicon and iron were formed via both co-deposition and aluminothermic reduction. In the electrolysis experi- ments, current efficiency first increased to a maximum value of 40.7% at a current density of 0.29 A/cm 2 , and then it decreased with the increase of current density. With the electrolysis time lasting, the content of aluminum in the alloys decreased from 76.05 wt.% to 48.29 wt.% during 5 h, while the content of silicon increased from 15.94 wt.% to 37.89 wt.%. INTRODUCTION Fly ash is a waste solid material that comes from the coal power plant. With the rapid development of the energy and power industry, the amount of fly ash has increased explosively over the last decade. The cumulate fly ash not only takes up quantities of farmland but also seriously pollutes the environ- ment. Currently, the fly ash is mainly used in con- struction and road-building materials, but the economic benefit is unsatisfactory. The fly ash contains large amounts of alumina and silica; for example, the fly ash that comes from the central and western Inner Mongolia areas of China has an alumina content as high as 50%, which is equal to low-grade bauxite. However, as alumina production expands, the bauxite resources cannot meet the sustainable development demands of the aluminum industry. Therefore, the applica- tion of fly ash in primary aluminum production will overcome the shortage of alumina resources, gain great economic benefits and social benefit, and avoid environmental contamination. To date, the alkaline or acid leaching method, acid and alkali combination method, and ammonium sulfate roasting method are the most used methods in the extraction of alumina from fly ash. 1 The alkaline process, mainly including the soda-lime sintering method and limestone sintering method, has disadvantages of high-energy consumption, high cost, and a large quantity of residue. The acid leaching method mainly adopts sulfuric acid or hydrochloric acid for the leaching process of fly ash. However, other elements such as Fe, K, Mg, and Ca were also dissolved into the acid, which increases the difficulty of the extraction of alumina, causes serious corrosion of equipment, has a high cost. The quality of alumina produced by acid and alkali combination method is high, but it has the disad- vantages of long production process, high energy JOM, Vol. 66, No. 5, 2014 DOI: 10.1007/s11837-014-0947-6 Ó 2014 The Minerals, Metals & Materials Society 694 (Published online April 9, 2014)