Preparation Of Prochloraz/Lignin Microcapsules By Ultrasonic Cavitation And Their Application Performance Exploration

Prochloraz(PCZ)is a broad-spectrum and highly effective fungicide,which can be used to control rice blast and wheat scab,etc.,and is widely used as a preservative in the storage and transportation of fruits and vegetables.However,the application of prochloraz is limited becaause of easy decomposition in light,alkaline and strongly acidic conditions.Microencapsulated prochloraz can reduce its photolysis rate and improve the environmental adaptability.Lignin is a kind of macromolecule compound with three-dimensional network structure,.Lignin is a three-dimensional network polymer,which has excellent properties in UV-blocking,oxidation resistance and biocompatibility.It can be used for the wall material of prochloraz microcapsules to improve its photostability and prolong the release rate of prochloraz,as well as enhance the storage and traportation stability and biocompatibility.In this paper,alkali lignin was used as the shell material,and the prochloraz was used as the core material to prepare Prochloraz/AL microcapsules(AL-PCZ)by ultrasonic cavitation.The best preparation process was summerized as following: the concentration of AL was 5 wt%,the mass ratio of AL(aq)to prochloraz was 4:1,the ultrasonic power was 720 W,the ultrasonic time was 3 min,and the concentration of surfactant was 1~3 wt%.The results show that AL-PCZ were uniform spheres with particle size ranging from 150 to 500 nm.The encapsulation efficiency of AL-PCZ was as high as 89.1%,and the loading capacity was 90.5%.The FTIR results indicate that the structure of prochloraz changed little after ultrasound processing and it was successfully encapsulted by lignin.Adding surfactants could reduce the size of the capsules to 170~260 nm and increase the stability of microcapsules suspension.Approximately 87.6% of prochloraz in AL-PCZ retained after 60 h of UV radiation and the photolysis rate was only 25% of the control sample without encapsulation,indicating that lignin provided good UV-blocking property.The sustained release experiments show that the release rate of AL-PCZ was lower than those of control and commercial prochloraz(C-PCZ).The anti-photolysis properties of AL-PCZ was comparable to that of C-PCZ,while its anti-raining and antiseptic performence were superior to C-PCZ.Long-time use of individual pesticide will cause drug resistance and has a limited spectrum of sterilization.The compound of prochloraz and imazalil(IMZ)were used as core material to prepare Prochloraz-Imazalil/Lignin microcapsules(AL-PCZ-IMZ)by ultrasonic cavitation technology.The optimal preparation conditions were summerized as following: the mass ratio of prochloraz and imazalil was 8:2,the ultrasonic time was 1 min,ultrasonic power was 480 W and other conditions were the same as the preparation process of AL-PCZ.The results show that the AL-PCZ-IMZ were uniform spheres ranging from 200~350 nm,and the drug loading capacity and encapsulation efficiency were 69.3% and 60.5%,respectively.The AL-PCZ-IMZ suspension had a better dispersion stability than AL-PCZ and commercial(Prochloraz/Imazalil)products(C-PCZ-IMZ).The FTIR results indicat that the structures of prochloraz and imazalil changed very little after ultrasound cavitation.Lignin was physically coated on the drugs and no obvious reaction occurred.The anti-photolysis and anti-rain scouring performance of AL-PCZ-IMZ were superior to C-PCZ-IMZ and they exhibited a good fresh-keeping effect on bananas.