# Separation of Conospheres from Lignite Fly Ash Using Acetone-Water Mixture
## 2 Materials and Methods  
The fly ash used in this work was class C fly ash taken from a lignite coal-fired power plant in Mae Moh, Lampang, Thailand. The bulk density of the fly ash was 1.3 g/cc, and the apparent density was 2.48 g/cc. The chemical compositions of fly ash are given in Table 1. The lime content of the fly ash sample was 1.43%; this slight amount can result in high alkaline solutions. Prior to cenosphere separation, the fly ash sample was oven-dried at 105 \({}^{\circ}\)C for 24 h. The separation of cenospheres was performed through the wet separation process sink-float method. The medium used to separate the cenospheres from fly ash was a mixture of acetone and water. The acetone (RCI Labscan Limited, 99.5%)-water mixture was prepared by mixing in different proportions, and the liquid contents were varied in terms of the acetone/water ratio as follows: 100:0, 80:20: 50:50, 20:80, and 0:100% \(\psi\)/\(\psi\). When water is mixed with acetone at different volume percentages, basically the density of the mixture decreases from 1.00 g/cc based upon the principle of an acetone-water mixture that behaves as a non-ideal solution [38]. The extent of the density decrease is directly dependent on the  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{3}{*}{**Acetone/Water Ratio (\% \(\psi\)/\(\psi\))**} & \multicolumn{5}{c}{**Percentage of Cenosphere Recovery (\%)**} \\ \cline{2-7}  & \multirow{3}{*}{**Calculated Density of Acetone–Water**} & \multicolumn{5}{c}{**Fly Ash/Medium Ratio**} \\ \cline{3-7}  & & **12.5 (Freshly Prepared)** & **12.5 (Used)** & **15 (Freshly Prepared)** & **15 (Used)** & **1:0 (Freshly Prepared)** & **1:10 (Used)** \\ \hline
100.0 & 0.79 & 0.01 \(\pm\) 0.001 & 0.01 \(\pm\) 0.001 & 0.03 \(\pm\) 0.004 & 0.02 \(\pm\) 0.002 & 0.02 \(\pm\) 0.003 & 0.03 \(\pm\) 0.003 \\
80.20 & 0.85 & 0.02 \(\pm\) 0.001 & 0.04 \(\pm\) 0.001 & 0.06 \(\pm\) 0.002 & 0.04 \(\pm\) 0.003 & 0.  
volume percent of acetone added in the mixture. Accordingly, in this study, the density of the mixtures with different acetone contents mixed with water was calculated (see the values in Table 1). The experiments were performed to determine the cenosphere recovery yield under the specified conditions: while the ratios of acetone and water were varied, the solid/liquid ratio was held fixed. The fly ash/medium ratios selected in this study were 1:2.5, 1:5, and 1:10 g/mL. Total volume per batch was 200 mL. While adding fly ash into the mixing container, manual stirring was applied immediately and continuously. The mixture was stirred for 10 min before leaving it for sedimentation, as the particles lighter than the medium density would float to the top surface and the heavier particles would sink. The recovery process to collect the floater part was done by stirring and settling repeatedly. Cenospheres were collected every two hours or two times during the four-hour period by carefully skimming off the floating layer into the receiving container. This collected part was drained through the vacuum filter and dried in the oven at 105 \({}^{\circ}\)C for 24 h. The percentage of cenosphere recovery was calculated by the following equation:  
\[\textit{Percentage of cenospheres recovery}\ (\%)=\frac{\textit{Weight of floating particles}}{\textit{Weight of total fly ash}}\times 100. \tag{1}\]  
The collected cenospheres were characterized for their physical properties and chemical composition and through mineralogical and morphological studies. Particle size and distribution were determined by laser particle size analyzer (Malvern Mastersizer 2000). Density was examined with an ultrapvcnometer (Ultrapycometer 1200e) in a helium gas atmosphere. Chemical composition by means of oxide percentages of cenospheres was also determined by microenergy dispersive X-ray fluorescence (EDXRF) (EDAX model: ORBIS PC) using a 2-mm beam diameter for the bulk of the cenosphere sample and a 30-\(\upmu\)m beam size on each particle (varying in sizes of 50, 100, 150, 200, 250, 300, 350, and 400 \(\upmu\)m).