Batu kapur merupakan bahan tambang yang ketersediaannya sangat melimpah di Indonesia terutama daerah Sumatera Barat. Batu kapur disintesis untuk pembuatan filler Precipitate Calcium Carbonat. Hasil penelitian yang telah dilakukan terhadap filler Precipitate Calcium Carbonat dari batu kapur berdasarkan hasil analisis X-RD, FTIR dan SEM-EDX, dapat disimpulkan bahwa senyawa hasil sintesis dari CaO batu kapur adalah Precipitate Calcium Carbonat dengan jenis kristal aragonit dan kalsit. Sementara uji BET menunjukan luas permukaan spesifik filler Precipitate Calcium Carbonat dengan nilai 7,315 m2/g. Permukaan Plastik ramah lingkungan dengan penambahan filler Precipitate Calcium Carbonat dikarakterisasi menggunakan AFM didapatkan nilai Rq 0,43 µm.

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In this study, CaO/SiO2 composites were prepared from rice husk silica (RH-SiO2) and limestone from a local company. The composites with different mass ratios of CaO to SiO2 (1:1, 1:2, 1:3, 1:5, and 1:10) were synthesized using the sol-gel technique and characterized using XRF, XRD, and SEM. The composites were then used as catalysts for the transesterification of palm oil, with the main purpose to investigate the effect of catalyst compositions on the percentage of conversion of the oil.  The results of XRD and SEM confirm the existence of RH-SiO2 as an amorphous material, and CaO as crystalline material, while the composites are a mixture of amorphous and crystalline phases. The catalysts were then used in transesterification experiments and the percentage of oil conversion was calculated.  To confirm the successful conversion of palm oil into fatty acid methyl esters, the products of the reactions were analyzed using GC-MS. The experimental results demonstrated that the composites prepared exhibit catalytic activity, with the highest conversion (60%) achieved using the catalyst with the CaO to SiO2 ratio of 1:3.