Synthesis of hydrotalcite using magnesium from seawater and dolomite

Three methods of synthesizing hydrotalcite(HT) have been developed using ma gnesium from seawater and dolomite(MgCa(CO3)(2)). In the first process, 1.0 M Na2CO3 solution was added to calcium ion free artificial seawater contain ing AlCl3 with an initial Mg/Al molar ratio of 2.0 similar to 3.7 until a p H of 10 was obtained. The solution was then continuously stirred for 1 h at 60 degrees C. CO32--HT was precipitated as a single phase, and the initial Mg/Al molar ratio, which each recovery of Mg2+ and Al3+ from the solution was above 98%, was 2.0-2.3. In the second process, a Ca(OH)(2) slurry was a dded to artificial seawater containing AlCl3 with an initial Mg/Al molar ra tio of 1.0 similar to 5.0 until a pH of 10.5 was obtained, and thm was stir red for 1 h at 60 degrees C. HT was also precipitated as a single phase wit h initial Mg/Al molar ratio 2.0 similar to 4.0. The initial Mg/Al molar rat io, which each recovery of Mg2+ and Al3+ from the solution was above 98%, w as 2.2 similar to 3.3, but SO42- and Cl- were contained in the precipitated HT. When HT was produced using initial Mg/Al molar ratio of 3.0 at 25 degr ees C, SO42- and Cl- in the HT were ion-exchanged with CO32- in a 0.05M Na2 CO3 solution for 24 h at 25 degrees C, and SO42- and Cl- content of the HT were decreased to 0.5 and 0.05wt%, respectively. In the third process, dolo mite calcined at 1000 degrees C was added to an AlCl3 solution with an init ial Mg/Al molar ratio of 1.0 similar to 2.0, and the solution was stirred f or 1 similar to 4 h at 25 similar to 90 degrees C. HT was precipitated with the smallest amount of MgO and Mg(OH)(2) when the initial Mg/Al molar rati o was 1.5 and the solution was stirred for 4 h at 90 degrees C.