Abstract: The herbicide of alachlor was incorporated into the channels of MCM-41-type mesoporous silica (M41) by using an impregnation method. Surface hydrophobic modification of the assembly of alachlor-MCM-41 (Ach/M41), via a gas-solid reaction with 1,1,1,3,3,3-hexamethyldisilazane (HMDS), gave rise to an efficient sustained-release system (Ach/TMS-M41). The resulting Ach/TMS-M41 not only retained high alachlor loading capacity but also possessed prolonged alachlor release time. The characterization results of XRD, nitrogen adsorption/desorption, FT-IR, and TG analysis showed that the M41 retained its structural integrity during the alachlor-loading process and alachlor was dispersed completely in the channels of MCM-41 with a mass ratio of alachlor [m (alachlor)/m(alachlor-MCM-41)] as high as 0.381 g·g-1 (mass fraction 27.6%). The release properties of Ach/M41 and Ach/TMS-M41 in water were investigated. 62% and 38.1% of alachlor were released from Ach/M41 and Ach/TMS-M41 ofter 6 days, respectively, which indicated that hydrophobic modification of MCM-41 was conducive to sustained-release of alachlor. Furthermore, the framework of the mesoporous silica protected the encapsulated alachlor against ultraviolet light irradiation.

Key words: MCM-41, Hydrophobic modification, Alachlor, Herbicide, Sustained release