Electrochemical mineralization of sulfamethoxazole by Ti/SnO₂-Sb/Ce-PbO₂ anode: Kinetics, reaction pathways, and energy cost evolution

详细信息    查看全文

• 作者：Hui Lin ; Junfeng Niu ; ^{junfengn@bnu.edu.cn} ; Jiale Xu ; Yang Li ; Yuhang Pan
• 关键词：Electrochemical mineralization ; Sulfamethoxazole ; Ti/SnO2-Sb/Ce-PbO2 electrode ; Mechanisms ; Energy cost
• 刊名：Electrochimica Acta
• 出版年：2013
• 出版时间：1 May, 2013
• 年：2013
• 卷：97
• 期：Complete
• 页码：167-174
• 全文大小：966 K

文摘

Electrochemical mineralization of sulfamethoxazole (SMX) was performed in an undivided cell equipped with a Ti/SnO₂-Sb/Ce-PbO₂ anode and a Ti cathode. The reactions kinetics was determined as a function of applied current density (0.5-40 mA cm^?2), initial SMX concentration (10-400 mg L^?1), initial pH (3-11), and electrode distance (3-20 mm). Degradation of SMX in contaminated lake water was quicker than that in deionized water. The electrochemical degradation of SMX followed pseudo-first-order kinetics. The nearly complete mineralization of SMX (>95 % ) was achieved in 60 min as the current density was higher than 10 mA cm^?2. The major mineralization products in aqueous solution were NH₄⁺ and SO₄^2?. The aromatic intermediates including 3-amino-5-methylisoxazole (AMI), p-benzoquinone (BZQ), and sulfanilic acid (SFN) were analyzed and quantified. A possible electrochemical mineralization mechanism of SMX was proposed. Firstly, the sulfone group or isoxazole aromatic ring was attacked by hydroxyl radical (OH), followed by the formation of sub-structures analogues such as SFN and AMI. Subsequently, the OH attacked the different groups of the sub-structures analogues to release NH₄⁺ and SO₄^2?. Furthermore, successive hydroxylation of the formed aromatic intermediates including BZQ and 3, 4, 5-trihydroxy-5-methylisoxazole occurred. The mineralization of intermediates to CO₂ and H₂O was finally achieved. The nitrogen atom of the isoxazole molecule was converted into NO₃^?, which was then reduced to gas at the cathode. The economic feasibility was evaluated by determining the energy cost. The results showed that the residence time and energy cost of SMX degradation at the optimal conditions from 100 mg L^?1 to 1 mg L^?1 were 32.9-23.0 min and 26.3-46.3 Wh L^?1, respectively. This electrochemical technique is expected to be an interesting alternative for the treatment of SMX in wastewater.