Voltammetric studies of reactive black 5 and its application in wastewater from batik industry

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Date
2014-03
Authors
Zainudin, Nur Syamimi
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Publisher
Universiti Sains Malaysia
Abstract
Azo and reactive dyes are two classes of organic dye mostly used in various applications especially in batik industry. Reactive Black 5 (RB5) dye is categorized in vinylsulphonate azo dye group due to the presence of –N=N- bonds combined with vinylsulphone as the reactive group. The production of carcinogenic aromatic amines, resulted from azo reduction has a significant risk of bioaccumulation in the food chains whereas reactive dyes have a long half-life in environment. Various methods have been used for dye measurements such as a chromatography and capillary electrophoresis (CE) but they are well-known for their complex and high cost instrumentation, high and multiple requirements on chemicals and sample preparation, maintenance and skilled labour. To overcome these problems, the voltammetric technique using Hanging Mercury Dropping Electrode (HMDE) as a working electrode and Britton-Robinson Buffer (BRB) as a supporting electrode was proposed to be developed. This technique was used for investigating the electroanalytical properties and quantitative analysis of RB5 dye at the mercury electrode. The RB5 dye was found to be accumulated and undergone irreversible reduction process at the mercury electrode. The experimental voltammetric parameters were optimized in order to obtain a maximum response which referred to the second reduction peak with analytical validation of the technique for RB5 dye. The optimum parameters for the differential pulse cathodic stripping voltammetry (DPCSV) technique in acidic medium were the BRB at pH 2.5, initial potential (Ei): +250 mV, final potential (Ef): -600 mV, scan rate (v): 5 mV/s, accumulation time (tacc): 80 s, accumulation potential (Eacc): 0 mV and pulse amplitude: 75 mV. In basic medium, the optimum parameters were Ei: -100 mV, Ef: -1000 mV, v: 15 mV/s, tacc: 30 s, Eacc: -100 mV and pulse amplitude: 150 mV in BRB at pH 9.0. Using both optimized parameters, RB5 dye at a concentration of 2 mg/L has produced second reduction peak at -65.50 mV in acidic medium whereas the same peak at -570 mV in basic medium. The limit of detection (LOD) of RB5 dye was approximately 12.15 μg/L and 7.97 μg/L for acidic and basic medium, respectively. The developed technique was applied for the analysis of RB5 dye in batik wastewater samples and the results were compared with those obtained by the UV-VIS Spectrophotometry method. It can be concluded that the developed technique is precise, accurate, rugged, robust, low cost, fast and has potential to be an alternative method for routine analysis of RB5 dye in batik wastewater samples.
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Voltammetric
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