Selective Adsorption of Platinum from Mixed Solutions Containing Base Metals Using Chemically Modified Activated Carbons

Abstract:

Bituminous coal was activated by using steam at 750°C in a furnace. The activated carbon (AC) particles were chemically treated with thiophosphoric and amine type extractants, then characterized and tested for precious metal selectivity in chloride media. The adsorption of anions [PtCl³⁻₄, PdCl²⁻₄] or cations [PtCl⁺, PdCKH₂O)³⁺, Ni(H₂O)⁺, Cu²⁺) on the carbon surface was elucidated by means of complexation and physical adsorption models. Owing to electrostatic repulsion in acidic media (> 1 M HC1), the thio- and amine-treated bituminous ACs did not react with copper and nickel cations. The adsorption rate constant for platinum showed a dependence on solution pH and extractant dosage on the surface of the carbon and was of the order 10^{− 2} min^_1. A three-parameter Toth isotherm best described the adsorption data for single component solutions. Furthermore, platinum adsorption was described by pseudo first order kinetics neglecting the intraparticle diffusivity.