Study on Preparation of Polymer-Modified Bentonite and Sand Mixtures Based on Osmotic Pressure Principle

Abstract

Polymer-modified bentonite and sand mixtures (PMBS) are widely used in the engineering field due to their low cost and low permeability. In this study, different ionic types of polyacrylamides were used to modify bentonite to improve its swelling properties and impermeability. The physicochemical properties of polymer-modified bentonite were characterized by X-ray diffraction, particle size distribution, IR spectroscopy, SEM, and free swell index (FSI) to further demonstrate the successful organic modification of bentonite. To investigate the impermeability mechanism of PMBS from the perspective of osmotic pressure, the colloidal osmotic pressure of bentonite and hydraulic conductivity were compared. The results showed that anionic polyacrylamide (APAM) had the most obvious improvement on the swelling properties of bentonite, and 3% APAM increased the FSI of bentonite from 15 mL/2 g to 41 mL/2 g. With the increase in polymer dosage, the colloidal osmotic pressure of bentonite increased and the hydraulic conductivity of PMBS decreased significantly. The interior of PMBS is equivalent to a highly concentrated bentonite–sand–water system. When the colloidal osmotic pressure in the restricted space is higher than the external hydraulic pressure, it will prevent infiltration from occurring. When the external hydraulic pressure exceeds the high concentration of bentonite colloid osmotic pressure, the hydraulic conductivity may increase rapidly. Therefore, the impermeability of PMBS depends on the colloidal osmotic pressure of bentonite. Finally, it was confirmed that PMBS had a self-healing capacity by simulating damage to PMBS.

Effect of low-temperature plasma-treated bentonite on rubber compounds properties

“…In the first region, ranging from 4000 to 3000 cm -1 , the bands correspond to valence vibrations involving changes in bond lengths of structural OH-groups associated with octahedral cations, as well as water molecules linked through hydrogen bonds. The second region, spanning from 1400 to 400 cm -1 , contains absorption bands specifically characteristic of the silicate structure [13][14][15]. The sharp band observed at 3620 cm -1 corresponds to the typical OH stretching region of structural hydroxyl groups for dioctahedral smectites.…”

A Study on the Impermeability of Nanodispersible Modified Bentonite Based on Colloidal Osmotic Pressure Mechanisms and the Adsorption of Harmful Substances

“…Based on Ozhan [ 24 ], modified bentonite containing cationic polyacrylamide can lower hydraulic conductivity from 3.4 × 10 −10 m/s to 5.4 × 10 −11 m/s. Zhang [ 25 ] verified that the anionic polyacrylamide-modified bentonite reduced hydraulic conductivity from 3.91 × 10 −10 to 2.12 × 10 −11 m/s. A skeleton created by sand in the BS enhanced the structural durability of the impermeable layer, facilitating its long-term use [ 26 ].…”