Study of loading isothiazolinone based biocide and release profiles from mesoporous silica matrices

Abstract

Silica mesoporous materials were proposed as new hosts for stabilizing isothiazolinone-based biocides. We synthesized two types of porous matrices: SBA-15 silica and mesocellular siliceous foam (MCF). The physicochemical properties of the silicas (structure, textural properties) are evaluated in order to determine their ability to encapsulate, stabilize and subsequently release, a commercial biocide used for latex preservation (CMIT/MIT). CMIT/MIT consists of an aqueous solution of the active ingredients CMIT (5-chloro-2-methyl-4-isothiazolin-3-one) and MIT (2-methyl-4-isothiazolin-3-one), present in a CMIT/MIT: 3/1 weight ratio. The two matrices were loaded with different biocide concentrations by using the traditional incipient wetness impregnation method. N2 adsorption, SEM and FTIR analyses showed that the biocide can be encapsulated within silica frameworks and preserved its original structure. Release tests in aqueous media indicated that the CMIT/MIT concentration in the leaching solution depends on the matrix nature, being the smaller values obtained when ordered matrices were used. Desorption experiments indicated that the biocide delivery in aqueous media could be delayed by increasing the pH of test solutions. Results showed that biocide encapsulation allows maintaining a long-lasting release, preserving the biocide activity even under conditions of temperature and pH at which decomposition and hydrolysis of non-supported CMIT is observed.