Effects of sodium dodecyl sulfate on the oriented growth of nesquehonite whiskers

Abstract

In this study, nesquehonite MgCO3·3H2O whiskers with long length and high aspect ratio were synthesized through reactive crystallization, in which MgCl2 and Na2CO3 precipitated in the presence of sodium dodecyl sulfate (SDS). The effects of SDS concentration, reactive temperature and reactants concentration were investigated. SEM, XRD and FT-IR were used to character morphology and structure of the products. It was found that the presence of SDS in the mixed aqueous solution was an important parameter for the morphology and size of nesquehonite crystals. The morphology of nesquehonite crystals changed from rod-like to bundle-like with increasing SDS concentration. The average length of nesquehonite whiskers was about 87–180μm while the aspect ratio was 18–45. The longest length reached 250μm and the biggest aspect ratio was about 100. The reactive temperature and reactant concentration also affect the size even the crystal type. It is concluded that SDS was beneficial for oriented growth of one-dimensional nesquehonite whiskers based on the formation process of the nesquehonite whiskers. The possible mechanism of SDS in nesquehonite whiskers precipitation was ascribed to physical adsorption of SDS on the individual amorphous nanoparticles or crystallites. The critical point of oriented growth occurred when the SDS concentration was about 4.33mM.