Abstract
The efficiency of degradation of an aqueous solution of reactive red 120 dye using Advanced Oxidation Process (AOP) was evaluated. A low pressure UV lamp and a combination of UV/TiO2 were tested using ten different dye concentrations (50 - 500 mg/L) at several retention times (5.2-60 min) a pH of 10.5. The effect of acidic pH (pH = 3) on dye removal efficiency and the Chemical Oxygen Demand (COD) of the treated effluents were also investigated. When the alkaline (pH = 10.5) reactive red 120 dye solutions were treated using a low pressure (380 nm intensity) UV lamp, a maximum degradation efficiency of 27.01% was obtained for the least concentrated dye (50 mg/L) solution and only a degradation efficiency of 0.33% was obtained for the most concentrated (500 mg/L) dye solution. When the alkaline (pH = 10.5) reactive red 120 solutions were exposed to a combination of UV/TiO2, a maximum degradation efficiency of 46.70% was obtained for the lease concentrated (50 mg/L) dye solution after 60 min and only a degradation efficiency of 2.84% was obtained for the most concentrated (500 mg/L) dye solution after 60 min. When the pH of the reactive red 120 dye solution was reduced to 3, a degradation efficiency of 56.45% was obtained for the least concentrated (50 mg/L) dye solution at 60 min and a degradation efficiency of 14.94% was obtained for the most concentrated (500 mg/L) dye solution at 60 min. However, the increase in degradation efficiency obtained in this study does not justify the cost of chemicals added to adjust the pH to 3 before treatment and then to 7 before final disposal. Also, the addition of chemicals (to adjust the pH) increases the COD of the dye solution thereby necessitating a further costly treatment.
Highlights
Textile industries are often considered a pillar in the economic growth of developing countries (Chen et al, 2007)
When the alkaline reactive red 120 solutions were exposed to a combination of UV: TiO2 hν (UV)/TiO2, a maximum degradation efficiency of 46.70% was obtained for the lease concentrated (50 mg/L) dye solution after 60 min and only a degradation efficiency of 2.84% was obtained for the most concentrated (500 mg/L) dye solution after 60 min
The increase in degradation efficiency obtained in this study does not justify the cost of chemicals added to adjust the pH to 3 before treatment and to 7 before final disposal
Summary
Textile industries are often considered a pillar in the economic growth of developing (and developed) countries (Chen et al, 2007). Textile industries are known to utilize huge amounts of water and chemicals in the textile production processes. Numerous amounts of chemicals such as dyes, fixing agents, leveling agents and pH regulators are used during these processes (Ntuli et al, 2009). There is always a portion of dyes that is not fixed to the fabrics during the textile dyeing process and is washed out during the finishing process with the textile effluent (Dyes and Pigments, 2010). Because these effluents are rich in dyes and chemicals
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