Clay minerals have obtained considerable attention for slow-release formulation of herbicides to increase weed control efficacy and reduce leaching potential and environmental pollution. This study deals with preparing, characterizing and examining the potentials of modified bentonite, zeoilite and sepiolite in adsorption and release of 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide. The results showed that 2,4-D sorption of the N-cetylpyridinium (NCP)-modified minerals were much higher than those of the unmodified ones. The 2,4-D adsorption capacity of the organo minerals increased with increasing surfactant loading. Desorption isotherms of 2,4-D did not coincide their corresponding sorption isotherms showing hysteresis. The proportion of 2,4-D released from the organo-bentonite, zeolite and sepiolite after seven desorption cycles varied between 29 to 50% of the total retained herbicide respectively. The sorbed 2,4-D on NCP-modified bentonite and zeolite showed gradual release pattern with time making these synthetic organo-minerals suitable candidate for slow release formulation of 2,4-D. Key Words: N-cetylpyridinium, modification, 2,4-dichlorophenoxyacetic acid
