Degradation of Tolonium Chloride Dye by Phosphate Ion in Aqueous Acidic Solution: Kinetic Approach

Abstract

The degradation of tolonium chloride (TC+) dye by phosphate ion (PO43-) in an aqueous acidic solution was studied using spectrophotometric analysis at 301 K, I= 1.0 M, [TC+]= 1.5 × 10-5 M, [H+]= 1.0×10-3 M, and ʎmax 600 nm. To determine the potency and rate of the reactant species, an aqueous acidic medium was employed. The reaction's direction and tendency were predicted using a thermodynamic analysis at an interval of 5.0 K and a temperature range of 301-321 K. Without the presence of intermediate complex/free atoms formation, a reaction that produced phenyl sulphoxide, phenylamine, and HPO32- as products of the reaction was obtained with a molar ratio of 1:1 for both reactants. First-order tolonium chloride reactivity was found in the reaction and first-order for the phosphate ion, resulting in a second-order reaction overall. The reaction process accelerated as the concentration of hydrochloric acid rose. The response time decreased with an increase in ionic strength concentration and added Ca2+ and Cl- did catalyze the reaction positively. A straight line that went through the origin was produced by plotting 1/ko vs PO43- concentration. The spectroscopic analysis showed no discernible shift from λmax of 600 nm. Additionally, an increase in temperature accelerated the reaction process. The reaction has a negative free energy change, G (-3.13–1.12 KJ/mol) which indicates that it is spontaneous and that the reactants have more free energy than that of the products. While the enthalpy of activation, H is positive and indicates that the reaction was endothermic and followed an associative path, the entropy of activation, S, is also negative (-7.45–1.10 KJ/mol), indicating that the reaction is less disordered. Due to the added ions catalysis and absence of free atoms during the course of the reaction, an outer-sphere mechanism was suggested for the reaction.