Synthesis and Characterization of Prussian Blue and Oxide Red Pigments from Metal Waste

In fulfilling its pigment material needs for industrial purposes, Indonesia still relies on imports, whose value continues to rise. This shows that the abundance of local raw materials has not been utilized optimally. Iron, as one of the pigment materials, can be obtained from the refining of metal waste. One of the metal wastes with a high Fe content (up to 97.11% w/w) is used in the manufacture of dishwashing wire. The manufacture of pigments from metal waste has the potential for sales value and commercial-scale development. The pigments synthesized are Prussian blue (iron (III) ferrocyanide or Fe 4 [Fe(CN) 6 ] 3 ) and oxide red (iron (III) oxide or Fe 2 O 3 ). Iron recovery is carried out using the leaching method with acids, specifically HCl and H 2 SO 4 . After the iron is dissolved in the acid and the dregs are filtered, the process continues with the oxidation stage, using H 2 O 2 as the oxidizing agent. The precipitation stage is carried out using NaOH and K 3 Fe(CN) 6 . After undergoing filtration and washing, the pigment is heated in an oven until a crystalline powder is obtained. Prussian blue and oxide red pigments were successfully synthesized, with coloring tending towards a Prussian blue hue. This is because the synthesized Prussian blue is more easily dispersed in CMC solution than the oxide red pigment. Several samples were found to change their tendency to oxidize red after sieving >90 mesh, indicating the influence of grain size on pigment mixing. FTIR testing revealed the presence of CN, Fe-O, and Fe-CN functional groups, confirming the presence of these groups in the pigment. This finding was reinforced by EDX testing, which showed the presence of Fe, C, N, and O atoms. From the SEM test of the pigment sieving >90 mesh, irregular angular crystal particles were produced with a size of 0.9-23.6 µm.