Sintesis dan Karakterisasi Zat Warna Kuning Goethite (α-FeOOH) berbahan Pasir Besi Alam

—Goethite yellow dye (α-FeOOH) is an inorganic synthesis product with natural iron sand as the basic material. Pure natural iron sand contains magnetic particles oxidized to produce Fe 3+ ions which can be used as starting materials for FeOOH compounds. Synthesis was carried out by coprecipitation method with NaHCO 3 as coprecipitation agent. The variation of the mass of iron sand is aimed at knowing the optimal comparison of the use of iron sand, H 2 SO 4 , and HNO 3 . The optimum ratio obtained between the mass of iron sand, H 2 SO 4 and HNO 3 is 3:10:10. Variations of pH synthesis were carried out at pH 2, 3, 4, 5 and 6 to produce a yellow color with different brightness. The pH causes the yellow color to get darker. The brightest yellow color was obtained at pH 2 synthesis. Characterization was carried out with DRUV-Vis to see the absorption wavelength, FTIR spectrophotometer to see the product's functional groups and XRD to see the crystal structure of the product.