Contact time (min)

q(mg/g)

Pb(II)

Cd(II)

Zn(II)

15 30 45 60 75 90

0.910 0.964 0.976 0.988 0.996 1.000

0.735 0.768 0.808 0.821 0.895 0.903

0.184 0.836 2.140 3.450 4.751 5.403