UV/TiO2 ASSISTED PHOTOCATALYTIC DEGRADATION OF SOME SELECTED VAT AND AZO PIGMENTS USING BOX BECKHEN DESIGN
UV/TiO2 ASSISTED PHOTOCATALYTIC DEGRADATION OF SOME SELECTED VAT AND AZO PIGMENTS USING BOX BECKHEN DESIGN
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Date
2014-09
Authors
UKANAH, SULEIMAN PENDO
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Abstract
In this study, photocatalytic degradation has been studied on four water insoluble colorants; two of these are commercial vat pigments; Caledon Khaki 2G (C.I Vat Green 8) and Caledon Green 2G (C.I Vat Green 2) while the other two were azo pigments synthesized in the laboratory in excellent yields via diazotization of p-nitroaniline and coupling with 2-hydroxy-3-naphthanilide and N,N-dimethylaniline respectively. The pigments samples were dissolved in dimethylformamide (DMF) to enhance solute-solvent interaction. The two synthesized azo pigments were characterized by melting point analysis, solubility test, uv-visible spectroscopy, infrared spectroscopy and mass spectroscopy. Suitable experimental design such as Box Beckhen design and multivariate analysis which allows adjustment of factor level to obtain an optimal response in experimental analysis was used for the optimization of colour removal from aqeous solution using UV radiation and TiO2 as photocatalyst. The photodegradation studies were conducted by dissolving 0.1g of each pigment sample in 100ml of DMF contained in four separate volumetric flasks to make a stock solution. Several other concentrations as stipulated by the design of experiment (DOE) were prepared from the stock solution and used in the degradation studies. The photocatalytic degradation study of the dissolved pigments in DMF was then carried out using a laboratory scale photoreactor for both the synthesized azo pigments and commercial vat pigments under UV light as a function of irradiation time, catalyst loading, pigment concentration and pH using titanium dioxide as the photocatalyst. The effects of these various operational parameters were investigated during the process and the extent of colour disappearance was determined using UV-vis Spectrophotometer at the wavelength of maximum absorption of each pigment sample and decolorization performance of over 95% was achieved. The results for the optimization revealed the following optimum conditions for degradation: initial pigment concentration 18.34 mg/L, catalyst loading 1.47 g/L, pH of 8.71 and irradiation time of 88.36 min. for Caledon Khaki 2G. The optimum conditions for the Caledon Green 2G were: initial pigment concentration of 19.13 mg/L, catalyst loading of 1.17 g/L, pH of 8.40 and irradiation time of 81.28 min. For the first synthesized azo pigment (AP1), its optimum conditions for degradation were: initial pigment concentration of 20 mg/L, catalyst loading of 1.53 g/L, pH of 9.38 and irradiation time of 89.29 min. while the optimum conditions of the second synthesized azo pigment (AP2) were; initial pigment concentration of 18.14 mg/L, catalyst loading of 1.50 g/L, pH of 9.85 and irradiation time of 83.46 min. It can be concluded that UV/TiO2 photocatalytic degradation of textile pigments using Box Beckhen design is a viable technique for the treatment of textile waste effluents since it is multivariate in approach which allows adjustment of factor level to obtain an optimal response in experimental analysis.
Keywords: Photocatalytic, UV Irradiation, Titanium dioxide, Azo pigment, Vat
Pigment, Degradation.
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UV/TiO2 ASSISTED PHOTOCATALYTIC DEGRADATION, SELECTED VAT AND AZO PIGMENTS USING BOX BECKHEN