Low-temperature Bleaching Of Cotton Knitted Fabric With Copper Complex Catalyst

The people's needs for a better life has put forward new requirements for all walks of life,especially for the textile printing and dyeing industry in green manufacturing.The traditional textile printing and dyeing industry is a high-pollution and high-emission industry,therefore,how to transform and upgrade under the requirements of the new era to achieve pollution-free,lowemission and low energy consumption and achieve green manufacturing is the focus of next research.At present,hydrogen peroxide bleaching is the most commonly used bleaching method in cotton fabric pretreatment.The bleached cotton fabric has the characteristics of high whiteness,stable quality and not easy to turn yellow,the bleaching process is pollution-free,so it is suitable for various bleaching processes.However,the traditional bleaching process is often carried out under the environment of high temperature and strong alkali,which not only consumes a lot,but also has unstable quality of cotton fabric,more strength loss and harsh handle.In order to solve these problems,it is crucial to develop a catalyst which can rapidly catalyze the hydrogen peroxide decomposition at low temperature and effectively bleach cotton fabrics.In this paper,the metal complex catalysts with high catalytic activities were prepared by coordinating copper ions with iminodiacetic acid and pyridine derivatives ligands,and the influence of ligands on the catalytic performance was analyzed.Two metal complex catalysts were screened out and their properties in low-temperature hydrogen peroxide bleaching of cotton knitted fabrics were explored.Firstly,the scouring cotton knitted fabric was used as bleaching object to study the bleaching ability of metal complex catalyst.Through single factor optimization experiments,low-temperature bleaching process was obtained:30%H2O2 10 g/L,penetrant agent JFC 2 g/L,scouring agent 2 g/L,metal complex IDA/Cu(?)/4-AmPy 30?mol/L,bleaching at 60?for 60 min.The whiteness of cotton knitted fabrics could reach more than 75%after bleaching by the alkali-free low-temperature process,and the strength loss was small.Secondly,in order to correspond to the actual bleaching process in industry,a low-temperature one-step bleaching process for cotton knitted fabrics without scouring pretreatment was designed.After optimization,the process conditions were obtained as follows:H2O2 8%cloth weight,scouring enzyme 4 g/L,complex 30 ?mol/L,penetrant agent 2.5 g/L,liquor ratio 5:1,bleaching at 70? for 60 min.After bleaching,the cotton knitted fabric featured 75.88%of whiteness,12.30 cm of capillary effect and 93.77%of bursting strength retention rate.Compared with the traditional high-temperature alkalioxygen process,the results showed that the CIE whiteness reached the same level,the capillary effect was greater,and the strength loss was significantly reduced,reflecting the advantages of metal complex catalyst in low-temperature bleaching.In the fourth part of this paper,the bleaching mechanism of the metal complex catalytic system was studied.Through the catalytic oxidation process of sodium lignosulfonate,the decolorization reaction mechanism in the bleaching process was indirectly inferred.The effects of pH,concentration of hydrogen peroxide,catalyst concentration and temperature on the activity of the catalytic system were also investigated,the results showed that the metal complex catalyst could completely decolorize sodium lignosulfonate within 60 minutes at 80 ? and pH 11.Then the effect of ·OH on the reaction activity was investigated by trapping agent experiments.The high valence metal-oxygen active species in the reaction system were further detected by high resolution ion mobility mass spectrometry.The results showed that·OH had little effect on the activity of the reaction,so it was not the main active species.ESI-MS confirmed the existence of Cu(?)=O·,which was supposed to be the main active species in the catalytic system of metal complexes.