STRUCTURE FORMATION OF IRON-CONTAINING DISPERSIONS OF ORGANOMONTMORYLONITE

Abstract

The aim of the work is to study the processes of structure formation of organomontmorillonite in iron-containing dispersions by studying the rheological and colloid-chemical properties of such systems. To modify the surface of montmorillonite, a cationic surface-active substance, a quaternary ammonium salt, hexadecyltriammonium bromide, was used. With the help of X-ray diffraction analysis, we confirmed the penetration of molecules of surface-active substances into the interlayer space of the mineral and its increase to 1.86 nm during the modification mineral surfactant/ cation exchange capacity (S/CEC)=1. The analysis of the results of rheological studies showed that the changes in the characteristics of montmorillonite dispersions depending on the concentration of surfactants are extreme and reach a maximum (6.7 Pa) at the degree of modification of the mineral S/CEC=0.3. The high values of ultimate shear stress confirm the formation of a continuous network between the mineral particles with an "edge–face" orientation. When the surfactant content in the system increases, the ultimate shear stress of the suspension gradually decreases and reaches practically zero values. These results lay the foundation for determining the optimal parameters for the synthesis of iron-containing dispersions based on organomontmorillonite. nZVI was obtained by its reduction on the solid surface of organomodified montmorillonite from a solution of iron(II) sulfate salt. X-ray diffraction data confirmed the fixation of nZVI on the surface of organophilized montmorillonite. Analysis of the results of rheological studies showed that changes in the characteristics of dispersions of iron-containing material based on organomontmorillonite depending on the content of nZVI are extreme and reach a maximum at (6.8 Pa) when the iron content in the sorbent is 0.01 mass fraction in the solid phase of the sorbent. When the content of nZVI is increased to 0.05 mass fraction of the solid phase of the sorbent, it is possible to obtain dispersions with high values of ultimate shear stress (3.3 Pa) and clearly expressed hysteresis loops, which indicates the formation of thixotropic structures and confirms the possibility of its use in permeable reaction barriers. Experimental data confirm that with an increase in the content of nZVI above 0.1 mass fraction in the samples, the ultimate stress and plastic viscosity decrease, which leads to the failure of the suspensions. These results lay foundation for determining the optimal parameters of sorbents synthesis and regulation of their properties by changing the hydrophilic-hydrophobic balance of source systems.