Study On Adsorption And Release Properties Of Propachlor And Acetochlor On Organic Bentonite

To provide controlled release properties to the formulation containing pretilachlor, organobentonites with different loading levels of dodecyltrimethylammonium chloride （DTMA） and hexadecyl trimethyl ammonium chloride （HTMA） were prepared and used as matrix of pretilachlor formulation. The structure of organobentonites was characterized by FTIR and XRD, and the sorption towards pretilachlor was investigated. The results were utilized to reveal the effects of organobentonites on the release of pretilachlor as well as its mechanism. The main results were showed as followed:1. It was showed that organobentonites with quaternary alkylammonium were of excellent sorption capacity for pretilachlor and greatly reduced its release in water. The results indicated that hydrophobic interaction played a key roll in the sorption and sustained release of pretilachlor, of which an enhancement could be achieved by increasing the alkyl chain length and the loading level of modifying agent. The time taken for50%of active ingredient to be released, T₅₀, from organobentonites with DTMA loading of60,80,100and120%of the cation exchange capacity were12.8,13.0,18.5and26.6times of the value for the formulation without organobentonites, respectively. Those for the release from organobentonites with HTMA of the same loading level were14.4,15.8,18.4and26.4times, respectively. It was found that T₅₀ exhibited excellent linear relationship with the sorption coefficient Kf from Freundlich equation, suggesting the feasibility of regulating pretilachlor release via controlling the structure of organobentonites.2. It was showed that organobentonites that were prepared with hexadecyl trimethyl ammonium chloride （HTMA） and dodecyltrimethylammonium chloride （DTMA） were of excellent sorption capacity for acetochlor and greatly reduced its release in water. It found that the ways of the array of modifiers in the layer space of organobentonite play a main role in process of sorption and release. Within the certain range, the layer space and sorption capacity were increased with increasing the dosage of modifier. The results indicated that the time taken for50%of active ingredient to be released, T₅₀, from organobentonites with HTMA loading of60,80,100and120%of the cation exchange capacity were7.75,6.35,11.05and88.93times of the value for the formulation without organobentonites, respectively. Those for the release from organobentonites with DTMA of the same loading level were2.19,3.13,4.38and23.7times, respectively. It was found that T₅₀ exhibited excellent linear relationship with the sorption coefficient Kf from Freundlich equation, suggesting the feasibility of regulating acetochlor release via controlling the structure of organobentonites.