The effect of sodium alkyl sulfates (C8–C16) on the electrokinetic properties of hematite

• 2 different specimens of reagent-grade sodium decyl sulfate.
• 3 different specimens of iron oxide.
• 4 different specimens of SDS, all reagent-grade.
• 5 different surfactants (octyl-, decyl-, dodecyl-,tetradecyl-, and hexadecyl sulfate).

The effect of anionic surfactants on the ζ potential of hematite dramatically changes with increase of the chain length from C8 to C16. Sodium octyl sulfate did not shift the IEP of hematite at concentration as high as 10−3 M while sodium hexadecyl sulfate induced sign reversal of the ζ potential to negative over the entire studied pH range (down to 3) at concentration as low as 10−4 M. Various batches of reagent-grade sodium dodecyl sulfate had different effects on the ζ potential of hematite over the pH-range 6–10. The discrepancies are interpreted in terms of impurities present in reagent-grade SDS at various concentrations.

The electrokinetic properties vary from one specimen of reagent-grade SDS to another, probably due impurities of these reagents.Figure optionsDownload as PowerPoint slide