Preparation of magnesium oxychloride (Mgx(OH)yClznH2O) from Aydıncık/İçel dolomites

The purpose of this doctorate study is to produce the precipitated calcium carbonate (PCC), magnesium oxide (MgO) and magnesium chloride (MgCl2) from dolomite ore (CaMg(CO3)2) collected from Aydincik/Icel region via hydrometallurgical and pyrometallurgical processes. Then, Magnesium Oxychloride (MOC, Mgx(OH)yClznH2O) was produced as a result of the complex reaction between MgO, MgCl2 and H2O in various molar ratios. The characteristic properties of products obtained from each stage were determined using XRF, XRD, SEM, FTIR, particle size distribution, wet chemical analysis and whiteness methods. At the first stage, influences of particle size, acid/dolomite ratio, stirring speed, reaction time and temperature on the dissolution of dolomite ore in HCl were investigated. The reaction order and rate constant of dissolution reaction were determined using fractional life method. CO2 released during the dissolution reaction was collected and stored in a gasometer tank in order to use in the following stage. In the carbonation stage, effects of Mg(OH)2 amount, reaction temperature and time, CO2 flow rate and Mg2+/Ca2+ ratio were investigated in order to precipitate Ca2+ ions as PCC in the solution obtained from the leaching stage. It was revealed that more specific experimental conditions are needed to produce PCC having pure aragonite crystals in comparison with the pure calcite production. Mg2+ rich solution was obtained via solid/liquid separation for the use in the pyrohydrolysis process MgCl2 and MgO particles were produced via controlled evaporation and pyrohydrolysis processes from Mg2+ rich solution. In the pyrohydrolysis process, effects of experimental stages, reaction time and temperature on the production of MgO were revealed. Chlorine gas released in this process was recovered as HCl in the condensation unit. MgO particles obtained from each experiment were identified as periclase mineral. However, two stage pyrohydrolysis process should be conducted in order to produce nano MgO particles. At the final stage, influences of MgO/MgCl2 and H2O/MgCl2 blends prepared in various molar ratios on the structure and physical properties of MOC cement were investigated. The strength of MOC cement prepared at the best conditions against the water was improved with phosphoric acid (H3PO4) addition. Moreover, expanded perlite or vermiculite in various ratios was mixed with the MOC cement. Therefore, bulk density and thermal conductivity coefficient properties of the MOC cement were decreased. As a result, it was demonstrated that MOC cement, used in the construction industry in recent years, can be produced from dolomite ore. Furthermore, PCC, MgO, CO2 and MgCl2 used in many industrial applications were obtained as by-products.