Abstract
This paper aimed to study the effects of natural polysaccharide (gum arabic, GA) on the formation of vaterite calcium carbonate and its stability in aqueous solution. Gum arabic is a macromolecule that has a high molecular weight and is amphoteric in character. A 0, 2.5, 5 or 10 ml of GA solution (30%) was added to the calcium chloride solution with various initial concentrations to prepare the vaterite calcium carbonate. The calcium carbonate particles were characterized using FTIR, XRD, SEM, TEM and DSC-TG as well as calculation of phase contents. The results of XRD and FTIR analysis were showing that the presence of GA during the precipitation changes the behavior of calcium carbonate to form vaterite until at lower dose used. In addition, the molar content of vaterite increased at the expense of content of calcite with increasing the GA dose. There are slightly improvements in the vaterite content by increasing the initial concentration. The formed vaterite calcium carbonates composed of aggregates as broccoli-like or spherical shape and with particle size 1.6 - 2.5 μm in diameter. TEM images showed that these aggregates composed of the sub spherical unit with diameter 15 - 30 nm. The thermal behavior of prepared vaterite was conformed the mineral composition of these phases. The prepared calcium carbonate, which is formed in the presence of different doses of gum, has a stability in the aqueous solutions at different temperatures, as the analyzes indicated that a very small percentage of the vaterite were converted to calcite. The gum arabic prevented or depressed the transformation of vaterite to calcite through capped the surface of particles, i.e. it is more effective in stabilizing the vaterite phase with increasing in initial concentration and time.
Highlights
Calcium carbonate is one of the most important minerals in the earth’s crust [1]
This paper aimed to study the effects of natural polysaccharide on the formation of vaterite calcium carbonate and its stability in aqueous solution
The current study aimed to study the effect of gum arabic on the spontaneous formation of vaterite and on its transformation to the most stable calcite at different initial concentrations of [Ca2+] and at different incubation temperature with Ca2+ CO32− molar ratio 1:2, constant flow rate and stirring
Summary
Calcium carbonate has different phases such as calcium carbonate hexahydrate, calcium carbonate monohydrate, vaterite, aragonite and calcite. These polymorphs have different crystal structure and appearance [2]. It is proved that the additives play an important role on the crystal growth rate, and could prevent the transformation from vaterite to calcite whether organic additives or inorganic additives [4]-[10]. Calcium carbonate nano particles were used in drug delivery and bone substitution [15] [16] [17], whereas vaterite has many properties that make it suitable for preparation of drug delivery carriers [18]. Vaterite has been used for the removal of dyes [19] [20] [21]; for adsorption of phosphate [22]; and metallic ions (Cu2+ and Mn2+) [23]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
