Study On Decolorization Of Printing Wastewater By Iron Chipping

The printing wastewater is one of the hard-deal industrial wastewater in China because its high organic pollutant content, chromaticity, alkalescence and water quality fluctuation. The quantity of the printing wastewater is also large. How to dispose the printing wastewater with economical and effective processing technology has become a universal problem concerned by the environmental protection industry today.This article analyzed the printing production procession, the ingredient, characteristics and harm of the printing wastewater and introduced each kind of processing method applied in the printing wastewater treatment. Since the iron chipping internal electrolysis method has the characteristics of low cost, high decolorization rate and is easy for industrialization, etc, this article put the iron chipping internal electrolysis method forward to process the printing wastewater. Then experimented the iron chipping internal electrolysis method to treat with the simulation printing wastewater whose main compound is the acid red dye. The experimentation used sponge iron and iron sand as padding sperately.Through the experimental study and theoretical analysis, we can draw the following conclusion:1. Static experiment indicated that, the influencing factors to the acid red printing waste water decolorization were the pH value, the residence time, the raw water chromaticity, the iron filings material particle size and its nature. The decolorization effect was more obvious when the pH value was low. The influence of residence time to decolorization rate was also great. When after a certain period of time, the rate no longer changed obviously. Although the higher raw water chroma was, the speed of decolorization was quicker, the decolorization rate got more lower. Comparing with iron sand (d = 1.0 ~ 1.2mm) under the same condition, the effect of decolrtization by sponge iron (d=0.9~ 2.5mm) was more better, but the distinction was unobvious.2. Orthogonal experiment was conducted by changing pH value, reaction time, raw water chroma.The result showed that the influence of three factors from high to low was reaction time, pH value, raw water chroma3. In the dynamic experiment, the filtering rate influence was remarkable. 94.6% color removal efficiency could be achieved with sponge iron as filter sand at 5 m/h filtration rate and pH5.0, while for high filtration rate(10 m/h), it was only 86.6%.It also dropped fom 90.4% to 76.7% by iron sand. We can found that the decolorization by sponge iron was more efficient than that by iron sand. To higher waste water chroma, internal electrolysis by sponge iron can get about 80% decolorization rate.4. Deactivation in the internal electrolysis could not be avoided. In later period of the experiment, the deactivation by iron sand was more serious and the decolorization rate dropped more than 40%. While the sponge iron could maintain high efficiency.5. Through the contrast experiment by sponge iron and iron sand,we can draw a conclusion that: Decolorization effect used by sponge iron was more better than by iron sand, and the influence of deactivation in sponge iron was milder than iron sand.