The adsorption of tungsten(VI) on activated carbon from 1.0 M Na(H)Cl solution
The adsorption of tungsten(VI) onto activated carbon has been investigated as a function of pHc in the range 2.0-6.5 at constant ionic strength (1 M NaCl) and temperature (25°C). The tungsten concentration was varied from 5 × 10-4 to 2 × 10-2 M. Adsorption is very strong at pHc < 4.5 and depending on equilibrium conditions, loadings of ∼ 2.8 mM WVI per g activated carbon can be obtained. Computer treatment of distribution data led to an adsorption model, similar to that proposed (J. J. Cruywagen and H. F. de Wet, Polyhedron 1988, 7, 547) for molybdenum(VI), comprising mainly dimeric species and small amounts of monomeric species. The chemisorption is explained in terms of complexation of tungsten(VI) with basic oxygen atoms at the surface of the activated carbon. Adsorption constants of tungsten and molybdenum correlate well with complex formation constants of tungsten and molybdenum with oxalate and citrate. © 1988.