Mineralization of Quinoline by BDD Anodes: Variable Effects and Its Effluent Characteristics

C R Wang,X G Ma,H Li,J Wang,S Z Zhang

doi:10.1155/2015/617850

C R Wang, X G Ma + Show 3 more

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https://doi.org/10.1155/2015/617850

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Abstract

BDD anodes were selected for quinoline mineralization and influence of operating parameters, such as current density, initial quinoline concentration, supporting electrolyte, and initial pH was investigated. Based on the consideration of quinoline removal efficiency and average current efficiency, at initial quinoline concentration of 50 mg L−1and pH of 7, the optimal condition was confirmed as current density of 75 mA cm−2, electrolysis time of 1.5 h, and Na2SO4concentration of 0.05 mol L−1by orthogonal test. At different electrolysis time, its effluent characteristics were focused on. The biodegradability (the ratio between BOD5and COD) was enhanced from initial 0.02 to 0.57 at 90 min. The specific oxygen uptake rate was used to assess effluent toxicity, and the value gradually reduced with decreasing effluent organic concentration with mean value of 5.51, 4.19, and 2.20 mgO2 g−1MLSS at electrolysis time of 15, 30, and 45 min, respectively. Compared with control sample (prepared with glucose), the effluent of quinoline mineralization showed obvious inhibition effect on microorganisms at electrolysis time of 15 min, and then it was significantly faded at 30 min and 45 min.

Highlights

Quinoline, as a typical heterocyclic aromatic hydrocarbon, is mainly derived from coal coking and coal gasification
The results showed that, with increasing of current density, removal efficiency of quinoline and Total organic carbon (TOC) significantly increased
The reason that, with increasing current density, the higher the concentration of ∙OH produced by boron-doped diamond (BDD) anodes, the more the quinoline oxidized by ∙OH was confirmed, but when current density was high enough, removal efficiency of TOC was more slowly enhanced than degradation rate of quinoline, which resulted from that in the mineralization process of quinoline; it transferred to other intermediate products; as a consequence, the concentration of quinoline decreased, but these intermediate products had not been further mineralized

Summary

Introduction

As a typical heterocyclic aromatic hydrocarbon, is mainly derived from coal coking and coal gasification. Electrochemical oxidation using boron-doped diamond (BDD) appears to be the most suitable technology because of its extremely wide potential window and very low background current [3,4,5]. It has been used for the degradation of different organic pollutants, such as phenol and its derivatives [6,7,8,9], oxalic and oxamic acids [10], salicylic acid [11], sulfanilic acid [12], carmoisine [13], tetrahydrofuran [14], and phenanthrene and cyclodextrin [15]. The above organics degrading by BDD anodes mainly focused on the following four aspects: (1) investigating variable effects; for example, Rabaaoui and Allagui discussed the variable effects of salicylic acid oxidation by BDD anodes in the pH range 3.0–10.0 and different current density and focused on the oxidation products [11]; (2) identifying oxidation pathway; for example, Zhu et al investigated the oxidation mechanisms of p-substituted phenols at BDD anodes [16]; (3) exploring degradation kinetics; for example, Dıaz et al discussed the kinetics of electrooxidation of ammonia, nitrites, and COD from aquaculture saline water system using BDD anodes and found that the ammonia removal was described by a second-order kinetics, while COD and nitrite removal followed zeroth-order kinetics [17]; (4) comparing the organics removal efficiency between BDD anodes and other electrode materials; for example, Bagastyo et al investigated the electrochemical oxidation of reverse osmosis concentrate on Ti/Pt-IrO2, Ti/SnO2-Sb, and BDD anodes and Journal of Chemistry found that dissolved organic carbon removal was enhanced at BDD anodes in the presence of SO42− [18]

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