Study On Ecological Technology Of Phosphorus-free Decolorization And Bleaching Of Purple Cashmere

After entering the new century,the living standards of the people have increased year by year,especially for the demand of high-end textile products.Cashmere products are deeply loved by the Chinese people because of their unique style that other textile products cannot match.The output of purple cashmere accounts for the largest proportion of cashmere production.At present,the pigment in purple cashmere fiber is removed by decolorization to achieve the whiteness of white cashmere.The process of decolorization of purple cashmere fiber:metal ion pretreatment?oxidative decolorization?reduction and decolorization.The colored cashmere decolorization process generally uses phosphorus-containing substances as hydrogen peroxide stabilizer,which has high wastewater treatment cost and serious environmental pollution.In view of the problems existing in the traditional decolorization process,this paper uses the non-phosphorus substance as a hydrogen peroxide stabilizer in the process of decolorization of purple cashmere,and optimizes the decolorization process of purple cashmere.Firstly,polyaspartic acid and its derivatives are used as hydrogen peroxide stabilizers in the application of purple cashmere bleaching.The polystyosic acid amide?PSI?is synthesized by heat-shrinking with L-aspartic acid as a raw material,and then hydrolyzed under alkaline conditions.Finally,the pH of the solution is adjusted to neutral drying with polyacid to obtain polyaspartic acid?PASP?.PSI is modified under alkaline conditions to synthesize urea/polyaspartic acid?PASP/Urea?,salicylic acid/polyaspartic acid?PASP/Salicylic acid?,citric acid/polyaspartic acid?PASP/Citric acid?.The molecular weight of these materials and the chelation property to Fe²⁺were studied and applied to the decolorization of purple cashmere.The results showed that:citric acid/polyaspartic acid?PASP/Citric acid?is suitable for application in the bleaching of purple cashmere,which can meet the whiteness of white cashmere.The optimum synthesis process is as follows:synthesis temperature 260?,synthesis time 2.5h,catalyst 9%sodium sulfite dosage?owf?,molar ratio of PASP to modifier citric acid 1?1.50.The obtained product had a molecular weight of 80 kDa and a chelate value of Fe²⁺390 mg/g.The conditions for oxidative decolorization of purple cashmere are as follows:oxidative decolorization temperature 65?,hydrogen peroxide usage 68 ml/L,stabilizer dosage 16 g/L,decoloring solution pH=9.5,reaction time 2h.With this process,the whiteness of the bleached purple cashmere can reach 52.3%,the strength of the single fiber is 9.80 cN with soft handle.Secondly,urea-citrate as a hydrogen peroxide stabilizer is used in the bleaching of purple cashmere.Urea-citric acid urea was synthesized by a solvent method using urea and citric acid as raw materials.The synthesis temperature,synthesis time,monomer ratio and ethanol+water ratio were studied by single factor experiment to synthesize urea-citric acid urea suitable for purple cashmere bleaching.The synthesis process is that the molar ratio of citric acid to urea is 1?2.5,the reaction time is 180 min,the reaction temperature is 50?,and the ratio of ethanol to water is 80?20.The conditions for the oxidative decolorization of purple cashmere were as follows:urea-citrate urea dosage18g/L,amount of hydrogen peroxide 68 ml/L,oxidation-temperature 60?,oxidative decolorization pH=10.0,decolorization time 2h.The decolorized fiber has a fiber whiteness of 51.23%and a single fiber strength of 9.78 cN,and has a good hand feeling.The decolorization wastewater has a B/C value of 2.89 and is biodegradable.Finally,sodium citrate is used as a hydrogen peroxide stabilizer in the decolorization of purple cashmere.Sodium citrate has good water solubility and good metal chelation.It is often used instead of sodium pyrophosphate to make phosphorus-free washing products in the washing industry.Using sodium citrate as a hydrogen peroxide stabilizer,based on the traditional decolorization process,the single factor analysis was performed on the amount of ferrous sulfate,the amount of hydrogen peroxide,the oxidative decolorization pH and the amount of sodium citrate.Orthogonal experiments were used on the basis of single factor Optimize the process conditions,comprehensively consider the amount of ferrous sulfate 4.5 g/L,the amount of hydrogen peroxide 70.4 ml/L,the oxidative decolorization pH value 9.5,the amount of sodium citrate 16.9 g/L,and the oxidation temperature 65?.The decolorization effect under the best experimental conditions was verified.The fiber whiteness was 51.18%,and the fiber strength was9.77cN.The B/C value of the decolorized wastewater is 2.74,and the biodegradability is good.Among them,urea-citric acid as a hydrogen peroxide stabilizer has the best comprehensive application effect in the purple cashmere decolorization experiment,which reduces the production cost and reaches the experimental idea of phosphorus-free decolorization.