The encapsulation efficiency of zircon pigments from robust solids to clear solutions

PurposeThis paper aims to systematically demonstrate a methodology to determine the relative and absolute encapsulation efficiencies (alpha(Re) and alpha(Ab)) for thermally- and chemically-robust inorganic pigments, typically like ZrSiO4-based pigments, thereby enhancing their coloring performance. Design/methodology/approachThe authors designed a route, surplus alkali-decomposition and subsequently strong-acid dissolution (SAD2) to completely decompose three classic zircon pigments (Pr-ZrSiO4, Fe2O3@ZrSiO4 and CdS@ZrSiO4) into clear solutions and preferably used inductively coupled plasma-optical emission spectrometry (ICP-OES) to determine the concentrations of host elements and chromophores, thereby deriving the numeric data and interrelation of alpha(Re) and alpha(Ab). FindingsZircon pigments can be thoroughly decomposed into some dissoluble zirconate-silicate resultants by SAD2 at a ratio of the fluxing agent to pigment over 6. ICP-OES is proved more suitable than some other quantification techniques in deriving the compositional concentrations, thereby the values of alpha(Re) and alpha(Ab), and their transformation coefficient K-RA, which maintains stably within 0.8-0.9 in Fe2O3@ZrSiO4 and CdS@ZrSiO4 and is slightly reduced to 0.67-0.85 in Pr-ZrSiO4. Practical implicationsThe SAD2 method and encapsulation efficiencies are well applicable for both zircon pigments and the other pigmental or non-pigmental inhomogeneous systems in characterizing their accurate composition. Originality/valueThe authors herein first proposed strict definitions for the relative and absolute encapsulation efficiencies for inorganic pigments, developed a relatively stringent methodology to determine their accurate values and interrelation.