Cation Exchange Properties of Chromium(III) Phosphate

Potentiometric titrations of chromium(III) phosphate have been carried out in the presence of cu²⁺, Zn²⁺, Ni²⁺ and K⁺ ions from aqueous electrolyte solution as a function of concentration in the temperature range 303-323 K. The Cr(III)PO₄ is found to behave as a weak non no functional cation exchanger. pka of the exchanger has been determined and is found to be dependent upon the nature of the cations in the order Ni²⁺ > cu²⁺ = zn²⁺. The uptake of zn²⁺ by the chromium(III) phosphate is also investigated. It has been found that the uptake of zn²⁺ increases with the increase in both the pH (4-7) and temperature (303-327 K). The mechanism of uptake of zn²⁺ ions is found to be an ideal cation exchange.