Adsorption behavior of hydroxypropyl guar gum onto montmorillonite and reducing adsorption in the reservoir

Hydroxypropyl guar gum (HPG) is a kind of thickener commonly used in the field of oilfield chemistry. The adsorption behavior of HPG onto Montmorillonite (Mt) was investigated in this article. The maximum adsorption amount of HPG on Mt. was 3.6 mg/g at the HPG concentration of 2 g/L. The effect of pH, temperature, salts, alcohols and hydrolyzed polyacrylamide (HPAM) on adsorption behavior was revealed. The results showed that adsorption capacity increased with pH ranging from 3 to 13. The adsorption capacity was slightly influenced at temperature from 20 °C to 60 °C. The adsorption amount decreased at the presence of NaCl, KCl, CaCl2 or MgCl2, while it increased with addition of Na2SO4 or Na3PO4. The adsorption capacity was found no change at the presence of monobasic alcohol, while it significantly increased with the increasing concentration of polybasic alcohol. The adsorption density reduced with the addition of HPAM. Scanning electron microscope (SEM) and X-ray Diffraction (XRD) confirmed that adsorption behavior occurred on the exterior surface of Mt. Besides, the adsorption was attributed to Van der Waals' forces and electrostatic interaction. The Fourier Transform infrared spectroscopy (FTIR) showed that adsorption behavior occurred on Mt. surface via physisorption rather than chemisorption. The adsorption behavior of HPG on Mt. surface obeyed the Langmuir adsorption isotherm which showed that the adsorption was monolayer adsorption. The adsorption mechanism would be characterized as exterior surface adsorption, physical adsorption and monolayer adsorption.