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.