silica ratio
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Abstract In this paper, the size screening method and X-ray fluorescent spectroscopy were used to analyze low-grade bauxite samples from Darling Range, Australia. The results showed that the Av Al / Re Si(available alumina to reactive silica ratio) of samples JDB225 and JDB364 increased by 34.5% (8.7% to 11.7%) and 11.2% (8.9% to 9.9%); the available aluminum increased by 11.2% (27.8% to 30.9%) and 4.9% (30.9% to 32.4%) respectively. In screening, the optimum particle sizes of the two samples were 4 mm and 2.8 mm respectively. The results show that the best screening particle size can be determined by the size screening method, which can achieve the optimal combination of available aluminum grade, Av Al / Re Si and mass recovery rate, so as to significantly improve the grade and Av Al / Re Si of low-grade bauxite.

The research aims to assess the claystone exposed in the Nfayil Formation (Middle Miocene) for Portland cement (P.C.) manufacturing based on mineralogy and geochemistry. The importance of the study is to avoid the miming of the agricultural soils that are mining now for the cement industry. Claystones of Nfayil Formation and the limestone of the Euphrates Formation were used to design the raw mixture as clay to limestone (1:3). The chemical composition (%) of the designed mixture was calculated using the Alligation Alternative Method (A.A.M.) as CaO (65.52), MgO (1.05), SiO2 (21.65), Al2O3 (7.43), Fe2O3 (2.62), Na2O3+K2O (1.52) and SO3 (0.26), which are suitable for P.C. The lime saturation factor (LSF = 92.8), silica saturation factor (SSF = 0.87), alumina ratio (AR = 2.8), silica ratio (SR = 2.16), and calcium to silica (CS = 3.04) of the planned mixture are all within the permissible range. A clinker was successfully manufactured as composed mainly of belite, alite, aluminate, and ferrite.

Cement industry is seeking alternative raw material and process to reduce the energy consumption and environmental impacts from conventional cement manufacture. This paper describes process of belite cements synthesis. Geothermal sludges, an undesired waste from Dieng Geothermal Power Plant as amorphous silica source and calcium hydroxide were used to form belite cement at elevated temperatures. Experimental results showed that principal phase of belite cement (larnite or β-Ca2SiO4) was formed at temperature as low as 800 °C. Thus, the geothermal silica is shown to be very promising starting material for the low-temperature production of belite cement.

<p>Optimizing steroid and triterpenes isolation from red algae <em>Eucheuma cottonii</em> was done using column chromatography by varying of column diameter (1, 1.5 and 2 cm) and a ratio of sample : silica (1:50, 1:100, and 1:150). Active compound of <em>E. cottonii</em> was extracted by maceration with methanol. Then, the extract was hydrolyzed using HCl 2 N and partitioned with petroleum ether. The extract after partitioned was separated using wet column chromatography. The result of separation was monitored using analytical thin layer chromatography (Analytical TLC) and identified using FTIR. The best separation was aimed using diameter column 1 cm and a ratio of sample : silica 1:150. Based on FTIR analysis, the steroid from extract had a functional group –OH, –C–H, C=O, -C(CH₃)₂, and C-OH alcohol and the triterpenoid from extract had a functional group –OH, C–H, C=O, C=C, -C(CH₃)₂ and C-OH alcohol.</p><p>Keywords: <em>E. cottonii</em>, column chromatography, steroid, triterpenoid, column size, sample : gel silica ratio</p><p> </p><p> </p><p><span>Optimasi isolasi senyawa steroid dan triterpenoid dalam alga merah <em>Euchema cottonii</em> telah dilakukan menggunakan kromatografi kolom dengan variasi diameter kolom (1; 1,5; dan 2 cm) dan rasio sampel : silika (1:50; 1:100; dan 1:150). Ekstraksi senyawa aktif pada <em>E. cottonii</em> dilakukan dengan maserasi menggunakan pelarut metanol. Ekstrak pekat metanol dihidrolisis menggunakan HCl 2 N dan dipartisi dengan petroleum eter. Hasil pemisahan dimonitoring menggunakan KLTA dan diidentifikasi menggunakan FTIR. Hasil penelitian menunjukkan pemisahan kromatografi kolom terbaik diperoleh dengan variasi diameter 1 cm dan variasi rasion sampel : silika 1:150. Hasil analisis senyawa steroid memberikan informasi gugus –OH, –C–H, C=O, -C(CH₃)₂, dan C-OH alkohol, sedangkan senyawa triterpenoid memberikan informasi gugus –OH, –C–H, C=O, C=C, -C(CH₃)₂ dan C-OH alkohol.</span></p><p><span><span>Kata Kunci: <em>E. cottonii</em>, kromatografi kolom, steroid, triterpenoid, ukuran kolom, rasio sampel : silika gel</span></span></p>