Natural bentonite (30 g) was dispersed in 0.8 dm3 of deionized
water and then, DAH-bentonite prepared by adding 1,6-diamino
hexane 1.5 times of the cation exchange capacity of bentonite and
stirred for 24 h. After this treatment, the solid phase was separated
by filtration, then washed with deionized water. Finally, it was
crushed, ground, sieved through a 63 mm size sieve and the
samples were collected from under the sieve and dried in an oven
at 70 8C for 24 h prior to the use.