Application of BOF Slag/Photochemistry/Electrochemistry on the Degradation of Aquatic Organic Pollutants via Fenton Reaction
Date Issued
2008
Date
2008
Author(s)
Chiou, Chyow-San
Abstract
The application of the Fenton process to decompose organic pollutants has attracted extensive attention due to its satisfactory success. The Fenton reaction reviews that H2O2 reacts with iron salts, which generates strong oxidizing radicals to decompose the organics. Using different types of Fenton reaction to decompose organic target compounds and studying their efficiency is the main purpose of this research. Basic oxygen furnace slag (BOF slag) is one of the solid wastes resulting from the steel making process containing about 12.5 and 4.5 wt.% of FeO and Fe2O3, respectively. Therefore, BOF slag has high potential to be used in the Fenton process as iron source due to the ion abundant iron-containing property, which can thereby achieve the reuse of the wastes and work toward environmental sustainability. This study evaluated the dissolution behavior of basic oxygen furnace slag (BOF slag) and the performance of H2O2 with BOF slag denoted as H2O2/BOF slag process to degrade polyethylene glycol (PEG) in the aqueous solution. A first-order kinetic model with respect to total organic carbon (TOC) was adopted to represent the mineralization of PEG by H2O2/BOF slag process. The experimental results in this study suggested that dosages with 3.98 × 10-4 mole min-1 L-1 H2O2 and 15 g L-1 BOF slag loading in the solution at pH 2 provided the optimal operation conditions for the mineralization of PEG yielding a 75.5% treatment efficiency at 100 min reaction time. The H2O2/Fe2+ ratio was then determined to be 13.5 : 1. Photo-Fenton reaction initiated by the UV irradiation with H2O2/Fe3+, denoted as UV/H2O2/Fe3+, to decompose di-n-butyl phthalate (DBP) in the aqueous solution. The concentration of total organic carbon (TOC) was chosen as a mineralization index of the decomposition of DBP by the UV/H2O2/Fe3+ process. A second-order kinetic model with respect to TOC was adequately adopted to represent the mineralization of DBP by the UV/H2O2/Fe3+ process. The experimental results of this study suggested that the dosages with 4.74 × 10-5 mol min-1 L-1 H2O2 and initial Fe3+ loading concentration of 4.50 × 10-4 mol L-1 in the solution at pH = 3.0 with 120 μWcm-2 UV (312 nm) provided the optimal operation conditions for the mineralization of DBP (5 mg L-1) yielding a 92.4% mineralization efficiency at 90 min reaction time. In an electro-Fenton reactor, oxygen and Fe3+ were reduced into H2O2 and Fe2+ by applying appropriate working electrode voltage in aqueous solution. Reactive black 5 (RB5) dye was chosen as the target compound to evaluate the efficiency of electro-Fenton reaction in this study. The results revealed that an optimal decoloration efficiency of RB5 (ηRB5) was achieved at the working electrode voltage of –550 mV/(Ag/AgCl), and the ionic strengths of KNO3 and of the solution is 0.1 mol L-1 and 20 mg L-1, respectively. Furthermore, when Fe3+ in the reaction solution was substituted by Cu2+, about the same ηRB5 can also be achieved. A first-order kinetic model was adopted to describe the decoloration of RB5 by the electro-Fenton process. The mineralization efficiency of RB5 used the previous three types of Fenton reaction following the sequence: Photo-Fenton > BOF-Fenton > Electro-Fenton. The Electro-Fenton reaction doesn’t possess the ability to mineralize RB5, it just only can decompose RB5 and achieve decoloration. Both of BOF-Fenton and Photo-Fenton can mineralize RB5, in terms of the quantity of H2O2 to mineralize one gram RB5, BOF-Fenton and Photo-Fenton need 101.5 g and 8.2 g H2O2, respectively. The mineralization efficiency of Photo-Fenton is far better than BOF-Fenton.
Subjects
Fenton reaction
BOF slag
photo-Fenton
electro-Fenton
mineralization
SDGs
Type
thesis
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