科研之友
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摘要
The analysis by FT-IR, GPC and functional groups content tests indicated that carboxymethylated lignin (CML) had higher molecular weight, lower polydispersity, less phenolic hydroxyl and more carboxyl content than those of alkali lignin (AL). In order to investigate the feasibility of using CML to disperse avennectins particles in aqueous suspension, the adsorption isotherm, kinetics and thermodynamics of CML on avennectins particles surfaces were studied by batch equilibrium experiments. The results showed that the adsorption of CML was fitted to Langmuir isotherm equation, and the saturated adsorption amounts and Langmuir constants decreased with temperature increasing. The maximum saturated adsorption amount was 9.569 mg/g, and 0<RL<1 indicated that the adsorption process was feasibility. The adsorption process followed the pseudo-second-order kinetic model with the entire adsorption, and the adsorption rate constants increased with temperature increasing. The equilibrium adsorption time was approximately 60 min. The thermodynamic parameters were obtained as ΔGad<0, ΔHad<0 and ΔSad>0. This indicated that the adsorption was a spontaneous, exothermic and entropy process. Theoretically, high temperature was not beneficial to the adsorption process. The values of ΔHad=-5.18 kJ/mol implied that Van der Waals forces were responsible for the binding of CML with avennectins. The values of Ea=14.23 kJ/mol indicated that the adsorption process was physical adsorption. The SEM showed that abamectin particle surface was smooth without hole structure. Abamectin particles adsorbed by CML could prevent particle from aggregation effectively, and increase physical stability of abamectin SC. The adsorption characteristics study demonstrated that CML was able to form stable adsorption on avermectin particles surfaces, and eligible to be used as a suspending agent in avermectin suspension.
