STUDIUL LEGITĂȚILOR CINETICE DE TRANSFORMARE A ACIDULUI GALIC PRIN APLICAREA PROCESELOR DE OXIDARE AVANSATĂ ÎN SISTEME MODEL

Abstract

Gallic acid is a naturally occurring phenolic compound. Due to its persistence and potential toxicity, presents environmental challenges. Removal of gallic acid from wastewater, allows recycling and reuse of water in various industrial processes, reducing water consumption and contributing to sustainable practices. As a result, the removal of gallic acid from aqueous model solutions was studied by applying (AOPs): AG/Fenton, AG/Fenton/UV, AG/TiO2/H2O2/UV according to different physicochemical parameters. AOPs have emerged as promising techniques due to their ability to generate highly reactive hydroxyl radicals, initiating the oxidation of GA and leading to its degradation. Based on the results obtained the kinetics degradation of GA (25 mg/L) can be described by pseudo-first-order kinetics. By comparison, it was identified that Fenton reactions offer efficient means for the oxidation of GA, leading to its degradation (50%) and mineralization (30%) after 5 min of reaction. Thus, the best initial operating conditions, for practical purposes, are [H2O2] = 5·10-4 mol/L, [Fe2+] = 1·10-5 mol/L, and pH value 3.0. It was found that the conversion kinetics of GA is carried out at the rate constant (kavg.) is 5.7·10-3 s-1, the reaction rate (Δc/Δtavg.) is 6.7·10-7 mol/Ls-1 during 118 s (τ1/2). During the oxidation of GA by Fenton reactions, various intermediate and byproducts are formed, including: hydroxylation products resulting from the attack of hydroxyl radicals on the aromatic ring; cleavage products such as formic acid, oxalic acid, and acetic acid; carbon dioxide and water: complete mineralization of GA to harmless byproducts, indicating the complete oxidation of the organic substrate.