Adsorption kinetics of sodium dodecyl sulfonate onto hematite

The adsorption kinetics and conformation change of sodium dodecyl sulfonate(SDS) onto Fe₂O₃-coated crystal sensors were studied by quartz crystal microbalances with dissipation(QCM-D). The results show that the adsorption of SDS onto Fe₂O₃ surfaces is a rapid adsorption process. The p H value has a great influence on the adsorption of SDS. When the p H value increases,the viscoelasticity of the adsorption layer improves,the stability of the adsorption layer deteriorates,and thus the recovery of hematite flotation gradually decreases. There is only one adsorption stage which is best fitted by the pseudo-first order model without any change in conformation in the p H range of 3 to 9. At the p H values of 10 and 11,the adsorption of SDS markedly increases and the recovery of hematite flotation also recovers. There are two distinguishable adsorption stages with the first adsorption stage best-fitted by the pseudosecond order model and the second adsorption stage by the Elovich equation. The adsorption layer also experiences an obvious conformation change as the adsorption continues.