Effect of NaOH concentration and aging time on the properties of synthesized Ca(OH)2 by sol–gel method

Abstract

The sol–gel method is one of the most versatile techniques to produce calcium hydroxide (Ca(OH)2) since it provides a flexible chemical route to synthesize materials with the desired properties. The work aims to investigate the influence of sodium hydroxide (NaOH) concentration and aging time on the properties of the synthesized Ca(OH)2. In the study, Malaysian limestone (CaCO3) from Baling, Kedah was applied as a precursor to synthesized Ca(OH)2 using the sol–gel technique. The synthesis was carried out with varying the NaOH concentration (0.5 M, 1.0 M and 2.0 M) and aging time (12 h, 24 h and 48 h). The synthesized Ca(OH)2 powder was subjected to X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope equipped with Energy Dispersive X-ray Spectroscopy (FESEM-EDX), Fourier Transform Infrared (FTIR) spectroscopy, X-ray Fluorescence (XRF) and Particle Size (PSA) analysis. The results exhibit the existence of calcite and aragonite phases at higher concentrations of NaOH, indicating an incomplete reaction of the hydrolysis process. The particle size of Ca(OH)2 increases as NaOH concentration and aging period increase. At higher concentrations of NaOH, agglomeration of Ca(OH)2 was more likely to occur. These findings suggested the potential use of Malaysian limestone as the precursor for Ca(OH)2 synthesis with desired properties by controlling the sol–gel reactions.