engleski

Thermokinetic study of magnesium hydroxide obtained from seawater

Magnesium hydroxide (Mg(OH) 2 ) is a very important inorganic compound with good physical and chemical properties. It has wide application in many fields, such as flame retardant in polymers, special ceramics, wastewater treatment, in the paper industry, as a catalyst, additive. Magnesium hydroxide can be produced by different methods such as precipitation, solvothermal and hydrothermal methods, microwave methods, electrochemical methods, the sol-gel method, dehydratation and hydration of commercial forms of Mg(OH) 2 and MgO, and the use of dolomite or sea water[1-2]. The precipitation crystallization method is the most economic one for industrial continuous production, having a simple process and low energy consumption [3]. In this paper magnesium hydroxide has been obtained from seawater by a well-known industrial process [4] which involves the chemical reaction between magnesium ions of seawater with dolomite lime to produce the magnesium hydroxide precipitate. Furthermore, the precipitate was modified by ultrasound of high intensity. The purpose was to obtain magnesium hydroxide with high purity and reduced particle size without agglomeration. The precipitated magnesium hydroxide is characterized by the particle size distribution determined by the laser scattering method in the range of 20 nm to 200 mm, and by the SEM/EDS analysis. Likewise, in order to investigate the effect of particle size on the thermal stability, thermokinetic study of magnesium hydroxide samples was performed by non-isothermal thermogravimetry in an inert atmosphere at different heating rates. The obtained data were used for the kinetic analysis of the degradation process. Kinetic analysis was performed using the isoconversional Friedman method in combination with the multivariate nonlinear regression method. Kinetic analysis revealed the complexity of the thermal degradation process for both investigated samples. Likewise, for each degradation stage of investigated samples, kinetic parameters (activation energy, pre-exponential factor and kinetic model) were calculated and compared.

Magnesium hydroxide,

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