Pages: (38-43 )
Abstract
The ability of N2H6SO4 to reduce Cr(VI) in aqueous phase was determined spectrophotometrically at different temperatures (298 – 333K) to study the effect of temperature on reduction while, the effect of pH was studied at pH 3, 5, 7, 9, and 12. The effect of concentration was also considered by varying the concentrations of the reductant (i.e. 4, 6, 8, 10 and 12mg/L) a pH of 5.4 at 298K for 12 minutes with concentration of Cr(VI) set at 10mg/L. The temperature effect showed that the reaction rate increased with increase in temperature. The kinetic results showed that the reaction was pseudo-first order with respect to Cr(VI). The activation entropy obtained from Eyring’s plot was -78.87 J/K/mol which agrees with the formation of a condensed compound. The activation enthalpy was -7.125KJ/mol showing that the reaction was exothermic. The activation energies obtained were 23.50, 24.28, 25.07, 25.47 and 26.26KJ/mol for the respective temperatures of 298, 308, 318, 323, and 333K. This increase in activation energy with increase in temperature implies that bond breakage and product formation was more favourable at lower temperature. The stoichiometry suggested that the Cr(VI) :N2H6SO4 molar ratio was 1 Cr(VI) : 1.45 N2H6SO4, this value was found to be in agreement with the theoretically obtained result. The results of this study show that N2H6SO4 could be use for the reduction of Cr(VI) in polluted environment.
Keywords: Aqueous phase Reduction; Cr (VI); N2H6SO4,