Chemical Science International Journal

This paper examines the equilibrium removal of Zinc, Copper, Nickel and Cobalt ions from aqueous solutions by cation exchange resins synthesized using orange mesocarp extract. The percentage metal ion exchange of Carboxylated-Toluene Di-isocyanate Orange Mesocarp Extract Resin (CTOR) increased with increase in pH of the solution phase, while that of Sulphonated-Toluene Di-isocyanate Orange Mesocarp Extract Resin (STOR) was relatively uniform with increase in solution pH. The results also showed maximum ion exchange of 61.48%, 67.24%, 69.82% and 78.96% for Zn²⁺, Cu²⁺, Ni²⁺ and Co²⁺ ions respectively for CTOR, while 78.10%, 83.98%, 88.00% and 93.80% for Zn²⁺, Cu²⁺, Ni²⁺ and Co²⁺ ions respectively for STOR using 50mg/L metal ion solution at 29°C. It was found that the uptake of Zn²⁺, Cu²⁺, Ni²⁺ and Co²⁺ ions by CTOR and STOR is related to the dissociation power of the exchangeable hydrogen and in sequence similar to the ionic radii of the metal ions. Thermodynamic parameters were evaluated and values obtained show that the ion exchange process was spontaneous, exothermic and of low entropy value, suggesting strong interaction between the metal ions and the exchange sites. These findings can serve as parameters for designing ion exchange treatment systems for heavy metal-contaminated wastewater.