Investigating a Mechanism for Contaminant Uptake by Organically Modified Clays

With freshwater sources decreasing and prevalence of water contamination on the rise, an effective water remediation technique is desperately needed. A thorough body of work on organically modified clay minerals (organoclays)... [ view full abstract ]

With freshwater sources decreasing and prevalence of water contamination on the rise, an effective water remediation technique is desperately needed. A thorough body of work on organically modified clay minerals (organoclays) for remediation of common contaminants from water shows great promise. However, the mechanism by which organoclays take up contaminant is unknown. An understanding of this mechanism is integral for improving and designing organoclays for optimal remediation while reducing material in applied use. In the current study, montmorillonite clay was modified at seven loadings with the surfactant hexadecyltrimethylammonium bromide. Each organoclay was characterized for carbon content (TCN), interlayer spacing (XRD), crystallinity (FT-IR), and thermal stability (TGA). Ethylbenzene uptake was studied for each organoclay by GC-FID and FT-IR to elucidate a mechanism by which organoclays take up contaminant. We propose that initial uptake of contaminant alters the clay interlayer chemical environment, which shifts the equilibrium of contaminant concentration towards the clay interlayer from the water. This contaminant-induced alteration promotes more contaminant uptake (self-amplifying) and is most dramatic at intermediate surfactant loadings (a “Goldilocks effect”).