The influence of modification on structural, textural and adsorption properties of bentonite

Abstract

Natural bentonite clay from the Bogovina locality in Serbia was Na-exchanged and modified using hexadecyll-trimethylammonium bromide as surfactant and organobentonite was obtained. The influence of modifications on the structural, textural and sorption properties of bentonite was investigated. It was estimated that modifications solely replace exchangeable cations in smectite layers, whereas other admixture minerals (quartz, calcite, feldspar) in bentonite remain unaffected. According to X-ray results the modification lead to changes in the smectite structure by either decreasing, for Na-bentonite, or increasing, for organobentonite, the interplanar spacing, d(001). The appearance of three new bands in IR spectra of HDTMA-bentonite comparing to those of raw and Na-bentonite assigned to the methylene vibrations confirmed the embedding of aliphatic cations into smectite structure. In organobentonite a significant change in textural properties was observed. In particular, specific surface area dramatically decreased while originally meso and microporous material became almost completely non-porous. Despite almost insignificant specific surface area the synthesized organobentonite due to gained organophyllity of its surface exhibits exquisite adsorption properties toward investigated textile dyes having adsorption capacity approx. 2 times higher than activated carbon.

Prirodna bentonitna glina sa lokaliteta Bogovina u Srbiji je natrijumski izmenjena i modifikovana heksadeciltrimetil amonijum-bromidom kao surfaktantom, pri čemu je dobijen organobentonit. Ispitivan je uticaj modifikacije na strukturu, teksturalna i adsorpciona svojstva bentonita. Utvrđeno je da primenjeni postupci modifikacije dovode isključivo do izmene katjona u medulamelamom sloju smektita, dok modifikacija ne deluje na druge prateće minerale u bentonitu (kvare, kalcit, feldspat). Uprkos neznatnoj specifičnoj površini sintetizovani organobentonit zahvaljujući novodobijenoj organofilnosti površine pokazuje izuzetna adsorpciona svojstva prema tekstilnim bojama, imajući adsorpcioni kapacitet oko 2 puta veći od aktivnog uglja.