Research on the Preparation of Ultramarine Pigments from Palygorskite

Ultramarine is a highly favored blue inorganic pigment. It is non-toxic with a deep color and widely used in architecture, plastics, coatings, fine arts and cosmetics. In this study, ultramarine pigment was synthesized using palygorskite, anhydrous sodium carbonate and sulfur as the raw materials through the high-temperature solid-phase method. The incorporation of palygorskite into the synthesis process greatly improves the reaction efficiency and reduces the amount of sulfur. When the mass ratio of palygorskite, anhydrous sodium carbonate and sulfur is 2:6:3, the resulting ultramarine pigment exhibits optimal chrominance. Notably, this sulfur ratio is substantially lower than that used in conventional processes, highlighting the efficiency and potential environmental benefits of this approach. The XRD, FT-IR, UV visible spectroscopy and SEM reveal that the synthetically produced blue pigments possess a sodalite structure, incorporating S₃^- and S₂^- radicals. Stability assessments indicated a marked improvement in the acid resistance of the dark blue pigment upon modification with dodecyltrimethoxysilane, with no notable color degradation observed in either neutral or alkaline conditions. The refined formulation and synthesis process not only optimize the production of ultramarine pigment, but also pave the way for enhanced durability and broader application prospects in various industries.