A Dual Function Organoclay Sorbent for Lead and Chlorobenzene

Abstract

AbstractTo demonstrate the concept of organoclays with dual sorptive properties, carboxylic group‐bearing carboxydecyltriethylammonium [(HOOC)C10H20N(C2H5)3]+ cations (CDTEA) were used to substitute exchangeable inorganic cations of montmorillonite. Sorption of Pb2+ and chlorobenzene was examined as a function of pH and over a range of equilibrium concentrations at constant pH. The dual sorptive properties of CDTEA‐montmorillonite were compared with those of its nonfunctionalized analogue, decyltrimethylammonium(DTMA)‐montmorillonite, and with Na‐montmorillonite. The infrared spectra showed bands corresponding to the carboxylic acid group and alkyl chain of CDTEA in CDTEA‐montmorillonite. Titration of CDTEA‐montmorillonite with NaOH indicated the existence of two distinct types of acidity originating from the native acid groups of the clay and the carboxylic groups of CDTEA. Sorption of Pb2+ by CDTEA‐montmorillonite was much higher than that by Na‐montmorillonite. Complete removal of 0.00724 cmol L‐1 (15 mg L‐1) of Pb2+ by CDTEA‐montmorillonite occurred at pH 5 and above, but this was not achieved by Na‐montmorillonite, regardless of pH. Pb2+ sorption by DTMA‐montmorillonite was lower than that by Na‐montmorillonite. These results indicate that Pb2+ is effectively bound to carboxylic groups of CDTEA. Sorption of chlorobenzene by CDTEA‐montmorillonite was comparable to that by DTMA‐montmorillonite. These results indicate that CDTEA‐montmorillonite possesses dual sorptive properties for both heavy metals and organic contaminants. Neither Na‐ nor DTMA‐montmorillonite were effective sorbents for both types of contaminants. The simultaneous removal of Pb2+ and chlorobenzene by CDTEA‐montmorillonite and the non‐competitive nature of the sorption processes each suggest the potential utility of such functionalized organoclays in the treatment of water contaminated by both heavy metals and organic chemicals.