Study On The Adsorption And Sustained-release Performances Of Activated Carbon Fiber To Metalaxyl And Hymexazol

Sustained-release preparation for pesticide has such advantagesas lower poison, better and longer effect and smaller impact onenvironment. In particularly, the absorbing preparations which canbe easily produced and industrialized by simple production linesand which have low costs and short recycle enjoy an excellentprospect. Both metalaxyl and hymexazol are low in poison andresidues, pollution-free, and odorless; however, they are easily to beevaporated and their effect cannot last long; therefore, if they aremade into sustained-release preparation, they can both prolongtheir effective duration and reduce the pesticides’ pollution onenvironment. This thesis, having used activated carbon fiber as theloading property, explores its absorption of metalaxyl andhymexazol as well as its function in sustained release. The thesisdiscusses on the pesticide-loading feature of activated carbonfibers that differ in their surface areas as well as the factors whichinfluence the process of its absorption. Based on the research above, the thesis furthers its study on the pesticide-loadingmechanism in terms of its dynamic and thermodynamic featuresand its sustained-release function.The research results are as follows:(1) The activate carbon fiber that has the largest surface arealoaded the largest amount of both these two kinds of pesticides.According to the physical analysis, activate carbon fibers mostlydepend on their micro-hole to absorb, and their pesticide-loadingcapability is related to both their surface areas and the intrinsicfeature of pesticides.(2) The dynamic and thermodynamic study on activate carbonfiber’s absorption of metalaxyl shows that the carrier’s pesticide-loading amount increases as the temperature of the solution rises,with the solution’s initial saturated concentration of10mg/ml; thepseudo-second-order model can better describe the absorbingprocess; and Langmuir isotherm equation can better fit theconsequence of the absorption.(3) At room temperature, the activate carbon fiber’s absorptionof hymexazol reaches its top when the solution’s PH value is6.0andand the absorbing time is2hours; and the solution’s initialconcentration is12mg/ml; pseudo-second-order model can betterillustrate the process that activate carbon fiber absorbs hymexazol The absorption is mainly chemical, while some of it is physical.(4) Producing pesticide-loading mechanism by using activatecarbon fiber to absorb metalaxyl and hymexazol has better effect onthese two pesticides’ sustained release. Metalaxyl’s sustained-release can last for over26days, while the sustained-release ratecan be up to70%. The sustained-release speed of these twopesticides is relevant to their released amounts, temperature, andpH value. As the temperature rises, their release amounts increase;hymexazol’s releasing effect is better when pH is or above7.0; andmetalaxyl’s releasing effect is better when the pH is6.0(5) The release kinetics of both metalaxyl and hymexazol can bedescribed by Ritger-Peppas model; their release can be explainedby and highly relevant to Fick Diffusion Mechanism.