Sustainable innovative method to synthesize different shades of iron oxide pigments

• Published in: Dyes and pigments 2017-02, Vol.137, p.403-409
• Main Authors: Mariani, Filipe Quadros, Borth, Ketlyn Wolfart, Müller, Marcelo, Dalpasquale, Mariane, Anaissi, Fauze Jacó
• Format: Article
• Language: English
• Subjects: Colloidal stability; Dispersion in white paint; Iron oxide pigments; Three colors
• ISSN: 0143-7208; 1873-3743
• DOI: 10.1016/j.dyepig.2016.10.024

The iron oxide pigments (IOPs) were synthesized using citrus pectin as a colloidal template that allows the generation of different shades of pigment. The innovation is that the same batch generates different colors for the hematite phase function of calcination temperature (300, 600 and 1000 °C) determined by thermal analysis. This sustainable innovative method (SIM) does not produce waste, requires a quantity of water proportional to the volume of the prepared colloid, and does not involve filtration, purification or grinding. The use of the inorganic salt precursor, iron sulfate, was evaluated as an important iron source and their influence on the pigment color. Six IOPs were prepared; iron (II) sulfate generated the IOP-II300 (yellow), IOP-II600 (red) and IOP-II1000 (purple); while iron (III) sulfate produced IOP-III300 (yellow), IOP-III600 (red) and IOP-III1000 (violet). The IOPs were characterized by their thermal behavior, structural and morphological properties, electronic and vibrational spectroscopy. The colloidal stability was determined by electrophoretic mobility and the dispersions optimized to the ideal pH. Dispersion tests were conducted on commercial white paint (water-based), and colorimetric profile (CIEL*a*b*) evaluated microscope slides coated with pigmented paint. A molecule of the citrus pectin responsible for complexing iron ions through the formation of molecular entanglements called egg box. The calcination at three temperatures produces pigments with different colors related to the particle size. [Display omitted] •A new synthesis method has been used to produce iron oxide pigments.•Environmentally friendly, sustainable and does not generate waste.•The same gel precursors can be synthesized different colors of iron oxide pigments.