Salinity Control Of Cotton Printing And Dyeing Wastewater And Research On Water Reuse Technology

In traditional cotton dyeing production process, cotton fibers are negatively charged with electricity in dye bath, while most dyes are tending to anionic. With the effect of the electrostatic repulsive force, the dye is restrained. In order to improve the dyeing rate, it must use large amounts of industrial salt or Sodium Sulfate to promote dye, and should use soda for fixation, which cause the production wastewater is high- sodium. It must use membrane technology to built desalination processing but general wastewater treatment process can not do. Therefore, high- sodium increase the difficulty of printing and dyeing wastewater reuse, the reuse rate is also not ideal. In order to achieve salt-free dyeing, based on the concept of cleaner production, this study conducted a test. With the cationic modification of cotton, it connected the positively charged quaternary ammonium to the cotton fiber, which enhanced the combining ability between cotton fiber and reactive dye, and then use alternative alkali for solid color. In this way, it can control the salinity in printing and dyeing wastewater from production source, and reduce the difficulty of water reuse.The main research contents of this paper are:1, analyzing the main source of salt in the traditional dyeing process and the influence of salt on the water recycle process.2, Using the cotton modification to change the surface properties of cotton, and doing many different dyeing experiments. Calculate the pickup rate of dyeing and the fixation rate by determining the absorbance of dyeing wastewater before and after modification. And then, to analysis the dyeing effect.3, On the basis of dyeing on cationic modified cotton, using alternative alkali for color fixing. Using traditional dyeing separately, such as cationic modification technology dyeing and the dyeing with cationic modification and substitution alkali solid color. To calculate the pickup rate of dyeing and the fixation rate through the measuring of the absorbance of different dyeing wastewater. And then, to analysis the dyeing effect.4, Measuring the COD and TDS from three different dyeing waste liquid, exploring the water recycling situation before and after modification by using the TDS accumulation formula.Through the analysis, it can be dyed in no salt conditions after cationic modification, and the pickup rate of dyeing is improved obviously which the tiptop is 99.74%. It can improve the fixation rate by using soda for color fixing, which reduced the COD of mixed wastewater. Because of non-salted accelerating, the TDS of wastewater is 60 percent lower than that of traditional process. And use substitution alkali instead of soda for color fixing, the dosage of substitution alkali is only one-tenth of soda consumption, which can further reduce TDS (salinity of wastewater), and the fertilizer expenses are also reduced. Through the simulation of salt accumulation, using cationic modified-substitution alkali fixation processes, after be treated by Materialized-biochemical treatment from wastewater plant, most of the Production wastewater can be reused without desalinization. Although the recycling rate is 80% to 90%, the limit of salty wastewater accumulated will not exceed production requirement.