Nanocrystalline magnesium oxide from dolomite via poly(acrylate) stabilized magnesium hydroxide colloids

Abstract

MgO nanoparticles are in high demand, valuable products with specific applications such as a bactericide, catalyst, ceramic material and as an adsorbent. Synthesis of MgO nanoparticles from naturally occurring dolomite is very important for the reduction of their production costs and for the value addition to naturally occurring, impure minerals such as dolomite. Therefore, in this paper, we report on an effective method to synthesize MgO nanoparticles using a novel colloid of poly(acrylate) (PA−)-encapsulated Mg(OH)2 composite, which has been prepared starting from dolomite. The composite is synthesized by adding MgCl2, which was produced using dolomite, to a mixture of poly(acylic acid) (PAA) and NaOH. The composite is heated at 500°C to produce MgO nanoparticles. The Mg(OH)2 mineralized in the composite colloid is brucite nanoparticles with average crystallite size of 5nm. The final product of MgO nanoparticles occurs in the crystalline form of periclase with average crystallite size of 20nm. Incorporated Mg(OH)2 nanoparticles enhance the thermal stability of PA− by 160–200°C. The sedimentation of the Mg(OH)2 colloidal particles, which are stabilized by PA−, is initiated after 18h but it takes 2 weeks for complete sedimentation. On the other hand, the Mg(OH)2 prepared in the absence of PAA/NaOH is completely sedimented after 18h. A portion of 0.100g of synthesized MgO nanoparticles can adsorb over 93% of methylene blue molecules from 5ppm methylene blue aqueous solution at the equilibration of the adsorption, whereas the adsoption of methylene blue by the same amount of 300μm sized MgO particles is very much lower; 35% being the best value when 0.100g is used. The proposed method is of great industrial value due to the potential applications of byproducts in addition to MgO nanoparticles themselves.