Paraquat release control using intercalated montmorillonite compounds

Abstract

A representative herbicide, paraquat (PQ; 1,1′-dimethyl-(4,4′-bipyridium) dichloride) was intercalated into montmorillonite by solution and solid state reaction methods. In a typical solution process paraquat aqueous solution was mixed with montmorillonite (Kunipia-F) aqueous suspension, which resulted in a paraquat–montmorillonite layer complex with a basal spacing of 1.3 nm. A paraquat–montmorillonite complex was also easily prepared by solid state reaction method. The mixture of paraquat and Na-montmorillonite was ground under ambient temperature. The basal spacing of the mixture increased to 1.3 nm after grinding for 30 min. In order to achieve the pH dependent releasing of intercalated PQ molecules, the PQ–montmorillonite complex was coated with cellulose acetate phthalate. The polymer modified PQ–montmorillonite complex exhibited a strongly suppressed PQ releasing in the acidic pH domain, while an enhanced PQ releasing at the neutral pH range, respectively.