Supercritical Carbon Dioxide Drying of Methanol−Zinc Borate Mixtures

Abstract

Supercritical carbon dioxide (CO 2 ) drying of zinc borate species was investigated to evaluate possible chemical alterations in the product during the drying. Methanol-wetted zinc borates produced either from borax decahydrate and zinc nitrate hexahydrate (2ZnO · 3B 2 O 3 · 7H 2 O) or from zinc oxide and boric acid (2ZnO · 3B 2 O 3 · 3H 2 O) were dried by both conventional and supercritical carbon dioxide drying methods. Zinc borate samples dried by both techniques were characterized using analytical titration, X-ray powder diffraction (XRD), thermo gravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, elemental analysis, and scanning electron microscopy (SEM). It was found that while zinc borate obtained from zinc oxide and boric acid did not have any chemical interaction with CO 2 , carbonates were formed on the surface of zinc borate obtained from borax decahydrate and zinc nitrate hexahydrate. The main factor for the carbonate formation during supercritical CO 2 drying is anticipated as the structural differences of zinc borate species. CO 2 is a nonpolar solvent, and it does not usually react with polar substances unless water is present in the medium. While 2ZnO · 3B 2 O 3 · 3H 2 O had three bound OH groups, 2ZnO · 3B 2 O 3 · 7H 2 O had five bound OH groups and one mole of water of crystallization. It is proposed that the water of crystallization reacts with CO 2 forming carbonic acid. Then, carbonic acid, which is stronger than boric acid, substitutes borate ions from their zinc salts.

A Novel Synthesis of Zinc Borates from a Zinc Oxide Precursor via Ultrasonic Irradiation

“…Ultrasonic irradiation produced a uniform particle size distribution with particle sizes between 130 nm and 506 nm, in contrast to hydrothermal synthesis. 22 The sub-micron particle size was observed because of the agglomeration effects of Van der Walls forces between the nanoscale zinc borates 1 . A thorn-like particle morphology was observed for specia) b) Fig.…”

“…Additionally, zinc borates are used as an additive in the polymer, coating and pigment industries due to their smoke suppressing and anticorrosive properties. [1][2][3][4][5][6][7][8] Because of their potential use in many industrial applications, in the last decade, several studies were carried out to produce zinc borate from different precursors and using a variety of methods. Sawada et al studied the synthesis of ZB in a two-step reaction of zinc oxide (ZnO) and boric acid (H 3 BO 3 ) at 60 °C for 1.5 h to form crystals, followed by heating to 90 °C for 4 h to enhance crystal growth.…”

Effect of Magnesium Borates on the Fire-Retarding Properties of Zinc Borates

“…Zinc borate is an important inorganic hydrated borate that finds applications ranging from polymers to paints for various purposes, such as a flame retardant or corrosion inhibitor, depending on the type of zinc borate [14]. Zinc borate is a multifunctional fire retardant containing different proportions of zinc and boric oxides [15].…”

An accelerated and effective synthesis of zinc borate from zinc sulfate using sonochemistry

“…Zinc borate (ZB) compounds are used in a wide range of applications in plastics, ceramics, electrical insulation, wood, wire, cement, pharmaceuticals, paint, and rubber (Ata et al, 2011;Chen et al, 2009;Gao and Liu., 2009;Gönen et al, 2009;Gürhan et al, 2009;Igarashi et al, 2004;Nies and Campbell, 1980;Schubert et al, 2002;Yumei et al, 2006). Zinc borates can be used as non-flammable and fire retardant additives in PVC, halogenated polyester and nylon, as combustion retardants and corrosive inhibitors, in the manufacture of refractory plastic materials, in electric/electronic materials, in the textile and paper industries and as a fungicide/insecticide in wood accessories (Gürhan et al, 2009;Schubert et al 2002).…”