Specific adsorption of molybdenum (VI) on activated carbon and oxine-impregnated activated carbon

The specific adsorption of molybdenum (VI) on activated carbon (Merck Co. Ltd.) and oxine-impregnated activated carbon (AC(HOx)) was studied by using a column method. The amount of molybdenum (VI) adsorbed on activated carbon and AC(HOx) were remarkably dependent on the value of pH. The optimum pH for the adsorption of molybdenum (VI) from 5.00 x 10-3 M molybdenum (VI) solution was 2.0 for activated carbon and AC(HOx) at the flow rate of 1.0 ml/min. The amount of molybdenum (VI) adsorbed on 5 g of the adsorbents was 1.15 g for activated carbon and 0.56 g for activated carbon impregnated with 0.5 g of oxine. The amounts of other metal ions such as copper (II), which were adsorbed on activated carbon and AC(HOx) at pH 2.0, were very small compared with that of molybdenum (VI). From 1.0 M HNO3 solution, 30 mg and 60 mg of molybdenum (VI) could be specifically adsorbed on 5.0 g of activated carbon and 5.0 g of AC(HOx) respectively, but copper (II), zinc (II), nickel (II), lead(II), manganese (II), cobalt (II), chromium (III), iron (III), and cadmium (II) were not adsorbed. The adsorbed quantity of molybdenum (VI) on activated carbon and AC(HOx) in 1.0 M acids increased in the order HNO3 < H2SO4 < HCl. Chloride and nitrate in concentrations up to 0.20 M showed little effect on the adsorption. (author)