Reactive dyes are the largest group of dyes used in textile industry and difficult to eliminate by conventional wastewater treatment plants.Different kinds of physicochemical processes are being used for the degradation of reactive dyes.These techniques were used to decolorize and degrade dyes. Unfortunately, most of them were frequently plagued mainly due to process inefficiencies and persistence in nature.The textile effluent containing reactive dyes are potentially toxic and mutagenic compounds.Therefore, in the present study different techniques for dye degradation and decolouration were studied.The techniques used were electrochemical, sonoelectrochemical, thermal pressure hydrolysis, photocatalysis, and sono-photocatalysis.
In each method, effects of different operational parameters were investigated on dye degradation.The results demonstrated that sonoelectrochemical degradation was three times more effective than the individual effects of ultrasonic and electrochemical treatment.In hydrolysis process it has been found that hydrolysis of RB 19 was enhanced at high temperature (120 °C) and pressure (2 atm) as compared to normal conditions of temperature and pressure.Further enhancement in dye degradation was observed when optimum amount of hydrogen peroxide oxidant was used at high temperature and pressure.In sonophotocatalysis process the rate of RB 19 degradation under UV light and TiO2 catalyst was found to be maximum under acidic conditions with 300 mgL-1 TiO2 and 100 mgL-1 dye concentration.The further increase in the degradation of RB 19 was achieved by combing photocatalysis and ultrasonic process.The dye degradation mechanism for different techniques resulted in the formation of small molecular weight products e.g. acetic acid, benzoic acid, oxalic acid, etc.All these techniques were found to follow first order reaction with successful reduction in half life. It is concluded that sonoelectrochemical degradation technique was found to be more efficient as compared to other treatment techniques in term of dye decolorization, degradation, reduction of TOC, half life and electrical energy consumption.
Source: Maria, Siddique (2011) Degradation of Industrial Organic Compound-RB 19. PhD thesis, COMSATS Institute of Information Technology, Islamabad