This article presents a two-step method of iron red synthesis based on waste long-term deposited iron(II) sulfate. The first step is the purification of waste iron sulfate, and then the pigment is synthesized by precipitation using a microwave reactor. The newly developed method of purification allows for quick and thorough purification of iron salt. The use of a microwave reactor in the synthesis of iron red makes it possible to reduce the temperature of the goethite-hematite phase transition from 500 °C to 170 °C and skip the calcination process. A temperature reduction in the synthesis decreases the formation of agglomerates of synthesized materials compared to commercial ones. The results of the research showed a change in the physicochemical properties of the obtained pigments depending on the conditions of synthesis. Waste iron(II) sulfate is a promising raw material for the synthesis of iron red pigments. Laboratory pigments are found to be differ from commercial pigments. The difference in properties speaks in favor of synthesized materials.
Keywords: hematite; iron pigment; iron red; solid waste; waste iron sulfate.