Thermodynamics and kinetics of Fe(CN)₆^4- adsorption onto 201×7 resin

To solve the problem of Fe(CN)₆^4- causing "iron poisoning" when cyanide-bearing waster water was treated with an ion exchange method, the adsorption properties of Fe(CN)₆^4- onto 201×7 resin were studied by using the Freundlich adsorption equation, the Langmuir adsorption equation, the pseudo-second order equation and the Fan Shan Yang model from thermodynamics and dynamics. The related thermodynamic constant and the apparent activation energy were calculated. The results show that Fe(CN)₆^4- adsorption onto the resin can occur spontaneously. The process conforms to the Langmuir equation and the pseudo-second order equation. It is controlled by film diffusion at the initial stage, but by gap diffusion at the later stage. Fe(CN)₆^4- exchanging to the stern layer is fixed by resin functional groups strongly leading to "iron poisoning" of the resin for generating Zn₂Fe(CN)₆ and Cu₂Fe(CN)₆ which adhere on the resin during the process of cyanides removed from the loaded resin with H₂SO₄. Fe(CN)₆^4- in cyanide-bearing waster water can be removed by selective precipitation.