Catalytic Oxidation Of Lignin By Copper Complex And Its Performance In Bleaching Cotton Fabrics

With the development of modern society,green production and lifestyle are gradually infiltrating into the economic development.In the textile industry,it is necessary to build a green and environmental friendly ecological production system to reduce the large pollution,emissions,and energy consumption of conventional bleaching methods,so as to promote the progress of production in the direction of sustainable development.The bleaching process of cotton fabrics is mainly based on hydrogen peroxide(H₂O₂)to construct a corresponding bleaching system.Hydrogen peroxide has strong oxidation and adaptability,and can be used for bleaching cotton fabrics in the process of dyeing process,steaming process and cold padding process.At present,the cotton fabric treated by the hydrogen peroxide bleaching process has the characteristics of high whiteness value,stable quality and color,and less pollution.However,the bleaching process still has disadvantages such as large consumption of water and heat,high temperature and strong alkali required for reaction conditions,large damage to the fabric,and poor hand feeling.At the same time,the removal mechanism of lignin,pigment and other impurities in the bleaching process is imperfect,which is also a major obstacle to the research of new bleaching systems.Therefore,the research on the removal mechanism of lignin and other impurities and the research on the bleaching process in a short time have very important industrial application value.Aiming at the above problems,this thesis designed and researched the catalytic oxidation performance of copper complex catalysts with hydrogen peroxide on lignin and its model compound,and the chemical bond breaking mechanism.At the same time,the bleaching system constructed in the research was used to bleach cotton knitted fabrics and cotton woven fabrics.The representative experimental results are as follows:1.Use copper sulfate pentahydrate(CuSO₄·5H₂O)to provide divalent copper ions(Cu²⁺),and combine it with iminodiacetic acid(IDA)and 4-dimethylaminopyridine(4-DMAP)to construct biomimetic enzyme complex catalyst.The metal complex catalyst is combined with hydrogen peroxide to construct a biomimetic catalytic system.The catalytic system for the catalytic oxidation of lignin and lignin model compound:1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)propane-1,3-diol was studied.It was found that the target substrate could be catalyzed and oxidized efficiently by the catalytic system.In addition,the color of the lignin solution undergoes an obvious decolorization reaction,gradually changing from brownish yellow to colorless and transparent.Under the action of the copper-oxygen active substance contained in the catalytic system,the chemical bonds gradually break,such as C-C and C-O.Then generate small aromatic molecules that can be oxidized again,and finally mineralize.2.In order to study the bleaching effect of the catalyst on cotton knitted fabrics,a new catalytic bleaching system was constructed by combining the catalytic system with the hydrogen peroxide bleaching system,and a small-scale bleaching experiment was performed on the bleaching system with the aid of a computer-controlled dyeing prototype.The bleaching effect of the bleaching system on cotton knitted fabrics was discussed from factors such as time,temperature,concentration of catalyst,concentration of H₂O₂,concentration of scouring enzyme and penetrant.Condition after optimization:temperature is 90°C,bleaching time is 10 min,concentration of copper complex catalyst is 30?mol/L,concentration of hydrogen peroxide is 8%(o.w.f),concentration of scouring enzyme is 4 g/L,concentration of penetrant is 2 g/L.The bleaching results showed that in a short time of 10 minutes,the CIE whiteness of the cotton knitted fabric reached about 73%,the gross effect value reached about 16.95 cm,and the burst strength retention was better,which was greatly improved compared to the alkaline oxygen process.The copper-oxygen active material has higher selectivity to impurities.After catalytic bleaching,the fiber is smoother and less rough,and the crystallinity of the fabric is improved,which is greatly improved compared to the alkaline oxygen bleaching process.3.In order to study the applicability of the catalytic bleaching system,the bleaching effect of scouring cotton woven fabrics was studied.Experimental conditions after regulation:temperature is 90°C,concentration of copper complex catalyst is 10?mol/L,concentration of hydrogen peroxide is 3%(o.w.f),time is 20 min.The whiteness value of the bleached fabric is about 81%,the gross value is about 8.5 cm,and it has relatively good bursting strength.The SEM and XRD test results show that the surface of the cotton woven fabric after bleaching is relatively smooth,the impurity particles and roughness are obviously reduced,and the XRD diffraction peaks are basically not offset relative to the original fabric,and the diffraction peak intensity is not weakened.Compared with hydrogen peroxide bleaching treatment,the bleaching effect is greatly improved.