Adsorption of cadmium and aniline of organoclay by HDTMA and CDTEA intercalating

Engineering Consultant, Kelee Environmental Consultant Corporation, 6F.-2, No. 288-8, Sinya Road,

Kaohsiung City 806, Taiwan

E-mail : singsuey@ms28.hinet.net Fax : 886-7-8150816

Department of Civil and Ecological Engineering, I-Shou University, No. 1, Sec. 1, Syecheng Rd.,

Daishu District, Kaohsiung City 840, Taiwan

E-mail : edmywu@isu.edu.tw

Manuscript received online 10 January 2014, revised 28 February 2014, accepted 10 April 2014

Organic cations such as quaternary ammonium cations (QACs) can be used to replace inorganic cations to form an organic-inorganic complex termed organoclay and to modify the clay surface from hydrophilic to hydrophobic. Organoclay can largely improve the sorption of organic contaminants. This study uses carboxydecyltriethylammonium cations (CDTEA) and general QACs, hexadecyltrimethylammonium cations (HDTMA) to modify clays, including Wyoming bentonite and the clay of Ton-Wei series soil and Chang-Bin series soil in Taiwan. The CDTEA cations were synthesized in laboratory scale, and the FTIR spectrum shows the presence of a carboxylic functional group and quaternary ammonium in the product. X-Ray diffraction detected that the clay layer spacing expanded and polymer cations were arranged as overlapping long chain hydrocarbons. Modified clays are observed for sorption of both cadmium and aniline. The adsorption of the cadmium in clay decreased after HDTMA was intercalated due to the occupation of exchange sites. The CDTEA modified clays can provide ligands to increase the adsorption of cadmium; this could be observed on the titration curve of electric potential with two end points. Both HDTMA and CDTEA modified clays are effective in regard to the sorption of aniline. The sorption of aniline in CDTEA clays was lower than that of HDTMA clays due to the polarity of the carboxylic functional group and the modification efficiency and purity of CDTEA. The dual sorption of cadmium and aniline by CDTEA clays showed noncompetitive adsorption, proving that the sorption mechanisms of the two solutes are ion exchange and partition, respectively.