Chlorination Decoloration of Textile Wastewaters and Dyestuffs-A Kinetic Study
Almost all dyestuffs used for textile processing impose heavy colors on effluents such that they can¡¦t meet effluent regulations. Sodium hypochlorite (NaOCl) has long been used for effluent decoloration by most textile plants. However, despite by the operators¡¦ experience, there is still no scientific method for controlling the dosing rate of sodium hypochlorite. An insufficient dosage may result in an aesthetically and legally unacceptable effluent. Whereas an excessive one may lead to the formation of chlorine-containing organic compounds which are harmful to the aquatic life and may limit the water utilization. It is necessary to develop a control technique for chlorination decoloration of textile wastewaters.
In this study, secondary effluent samples from a textile wastewater plant and synthetic wastewater samples prepared by two azo-type dyestuffs were used for chlorination decoloration tests in a batch reactor with a residual chlorine indicator.
Experimental results indicate that the most economic and effective reaction conditions for decoloration of the test wastewaters were pH = 4 and residual chlorine = 14 mg/L. In the conditions, wastewaters with true color intensity = 1,200 ADMI could be reduced to values less than 400 ADMI within 60 min. Results also confirm that on-line monitoring of residual chlorine concentration in the reacting liquid can be used to achieve a better control of chlorine addition.
Experimental data also indicate that the color removal rate (-dC/dt) was linearly proportional to the color intensity (C) and free hypochlorous acid (HOCl) concentration.
Advisor:Meu-Jiuan Sheu; Ruu-Shyan Huang; Ming-Hsien Chou
School:National Sun Yat-Sen University
School Location:China - Taiwan
Source Type:Master's Thesis
Keywords:kinetic study sodium hypochlorite decoloration textile wastewater
Date of Publication:07/17/2000