Title of Paper:Effects of surfactant concentration on alkyl chain arrangements in dry and swollen organic montmorillonite

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Date of Publication:2013-05-01

Journal:APPLIED CLAY SCIENCE

Included Journals:SCIE、EI

Volume:75-76

Page Number:134-140

ISSN No.:0169-1317

Key Words:Montmorillonite; Organoclay; Solution intercalation; Swelling; Surfactant

Abstract:To investigate the effects of surfactant concentration on alkyl chain arrangements in dry and swollen organic montmorillonite (OMt), Na+-montmorillonite (Na+-Mt) was modified with cationic surfactants with different alkyl chain lengths, including tetradecyl-trimethylammonium bromide (TTAB), cetyltrimethylammonium bromide (CTAB) and steartrimonium bromide (STAB), at a series of concentrations. The properties of dry and swollen OMt were characterized by thermal analysis and X-ray diffraction. Two kinds of novel arrangement of alkyl chains were found for dry CTAB-Mt The surfactant polar head showed two arrangements when the CTAB concentration increased from 0.23 to 0.45 cation exchange capacity (CEC). The arrangement of the paraffin-type bilayer had a larger tilting angle at 1.93 CEC than that of reported research, leading to a maximum d-spacing of 5.81 nm. For swollen CTAB-Mt in the solvent, the d-spacing first increased and then remained constant with increase in the amount of added CTAB. The swelling behavior was proposed, including three distinct stages: solvent-controlling stage, surfactant concentration-controlling stage, and alkyl chain length-controlling stage. The alkyl chain arrangements of dry and swollen OMt were further confirmed by TTAB-Mt and STAB-Mt (C) 2013 Elsevier B.V. All rights reserved.