Simultaneous removal of metals Cu²⁺, Fe³⁺ and Cr³⁺ with anions SO₄^2- and HPO₄^2- using clinoptilolite

In the present study the effect of SO₄^2- and HPO₄^2- on ion exchange of Cu²⁺, Fe³⁺ and Cr³⁺ on natural clinoptilolite is examined under normality of 0.01 N, temperature of 25 ± 2 °C and pH 2-2.5 after four days of equilibration. It is observed that Cu²⁺ uptake is significantly decreased in the presence of HPO₄^2- and SO₄². The observed effect is less significant for Fe³⁺ and Cr³⁺ in the presence of SO₄^2- and HPO₄^2- respectively. This could possibly be due to the metal-anion complex formation and the nature and charges of the complex species present. Blank solutions show precipitation in the case of Fe³⁺/HPO₄^2- solution, leading in complete removal of Fe³⁺ from solutions. Precipitation along with ion exchange is resulting in higher removal of Fe³⁺ from the solution than ion exchange or precipitation alone. Finally, anion co-removal is significant, reaching 80% for HPO₄^2- ions.