Effects of temperature and surfactant concentration on the structure and morphology of calcium carbonate nanoparticles synthesized in a colloidal gas aphrons system

Abstract

Calcium carbonate (CaCO3) has a long history of application in various fields such as polymer, paper, biomedicine, and healthcare. Some applications depend highly on its characterization. In this work, CaCO3 particles were synthesized at various temperatures and surfactant concentrations by a new method, so-called colloidal gas aphrons (CGAs) system. (CGAs is the name for certain microbubbles with a special structure that was introduced for the first time by Sebba). Then, the synthesized particles were characterized. Conventional techniques such as Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM) have been employed to distinguish between morphology and crystalline structure of generated particles. Experimental results demonstrated that the temperature and surfactant concentration have opposite effects on the structure of synthesized CaCO3 particles. An increase in the surfactant concentration led to a shift in the calcite cubic particles with an average 2.5 μm size to spherical particles with 200 nm diameter. The experimental data also showed that increasing the concentration of surfactant from 100 mg/l to 600 mg/l in the CGA system resulted in a phase shift from calcite to vaterite particles. Moreover, analyzing the effect of temperature showed a new phenomenon: increasing the temperature from 25 °C to 75 °C resulted in the generation of rod-like aragonite particles when surfactant concentration was low (100 or 200 mg/l) but was not observed in higher concentrations (400 or 600 mg/l) of the same surfactant. However, an increase in the temperature and concentration of surfactant resulted in production of finer particles.