| China is rich in walnut resources with the cultivation area of more than 80 million mu,while the total output of walnut kernel and walnut green husk are 3 million tons,respectively,the first largest walnut producer in the world.A large number of walnut green husk are piled up,which not only waste the resources,but also pollute the environment,while walnut green husk pigment can be used as dye for silk and wool dyeing.In this paper,the drying,pigment extraction and dyeing performance of walnut green husk were studied in order to provide technical support and basic theory for drying and deep processing of walnut green husk.（1）The effects of different drying methods on the quality of walnut green husk were studied.Results showed that it took the shortest time to get constant weight by microwave drying,indicating the fastest drying rate,followed by medium-short infrared wave drying.In addition,contents of total phenols,total flavonoids and quinones in the walnut green husk dried by sun were were significantly higher than other drying methods（p<0.05）,followed by hot air drying at 50°C and medium-short infrared wave drying.The color of walnut green husk powder by hot air drying at 50°C was the lightest,followed by medium-short infrared wave drying.By comprehensive comparison of the five drying methods,the quality of the walnut green husk dried by sun was the best,but affected by the weather easily.In the rainy weather,there was no significantly difference between 50°C hot air drying and medium-short infrared wave drying（p>0.05）.Moreover,the time by medium-short infrared wave drying was only 1/3 of the time by 50°C hot air drying,the medium-short infrared wave drying was more suitable for walnut green husk drying with the higher drying efficiency.（2）The ultrasonic assisted extraction technology of total phenols,total flavonoids and quinones from walnut green husk were studied.When the walnut green husk was crushed to40 mesh,extracted with 10%ethanol（v/v）at the ratio of material-liquid 1:45（w/v）,ultrasonic power of 400 W,ultrasonic frequency of 28 Hz,extraction temperature 60°C for 140 min,the extraction amount of total phenols and total flavonoids in walnut green husk were highest.When the walnut green husk was crushed to 40 mesh,extracted with 50%ethanol（v/v）at the ratio of material-liquid 1:45（w/v）,ultrasonic power of 400 W,ultrasonic frequency of 40 Hz,extraction temperature 60°C for 180 min,the extraction amount of quinones in walnut green husk was highest.（3）The dyeing process of walnut green husk extract,walnut quinone and1,8-dihydroxyanthraquinone on wool were studied.Results showed that the optimum dyeing process of walnut green husk extract included the concentration 250 mg·L-1,pH 4,bath ratio1:60,dyeing at 80°C,pre-mordant dyeing for 60 min,then dyeing with walnut green husk extract for 120 min,the value of△E*was largest.The optimum dyeing process of walnut quinone included the concentration 100 mg·L-1,pH value 4,bath ratio 1:60,pre-dyeing at90°C for 90 min,then dyeing with mordant for 60 min,the value of△E*was largest.The optimum dyeing process of 1,8-dihydroxyanthraquinone included the concentration 100mg·L-1,pH value 4,bath ratio 1:50,one-bath dyeing at 80°C for 70 min,the value of△E*was largest.All the dyed wool demonstrated good colorfastness and good color-fastness.（4）The adsorption kinetics of walnut green husk extraction,walnut quinone and1,8-dihydroxyanthraquinone were studied.Results showed that the dyeing of walnut green extract,walnut quinone and 1,8-dihydroxyanthraquinone were consistent with the quasi-second-order kinetics model,and the adsorption process belonged to chemical adsorption.The dyeing percentage,dyeing rate and dyeing equilibrium adsorption capacity were all increased with the increase of temperature,the semi-dyeing time decreased with the increase of temperature.It was found that the dyeing mechanism of walnut quinone and walnut green husk extract was similar,meaning that walnut quinone played a major role in dyeing wool of walnut green husk extract. |
