The effect of different molecular weight of poly(ethylene glycol) on the electrokinetic and rheological properties of Na-bentonite suspensions

In this study, the effect of monoethylene glycol (MEG) and different molecular weight of poly(ethylene glycol) (PEG) solutions (PEG200, PEG400, PEG600, PEG1000, PEG3350 and PEG8000) on the electrokinetic and rheological properties of Na-bentonite suspensions were investigated in the polymer concentration range of 1 × 10−5 to 1 × 10−1 M. The physicochemical properties of Na-bentonite such as chemical composition, cation exchange capacity, density, particle size distribution and specific surface area were determined to characterize the clay sample. Na-bentonite did not have an isoelectric point value in the pH ranges of 1.75–11.56 and it had a negative surface charge in studied pH ranges. The zeta potential values of clay–polymer suspensions were less negative at high concentrations (at 1 × 10−1 M and 1 × 10−2 M) and at higher molecular weights of polymer in the suspensions. The suspensions exhibited Bingham flow behavior. Some peak position variations were observed in the FTIR spectra of Na-bentonite interacted with PEG molecules when it was compared with purified Na-bentonite and pure polymer spectra.