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. 2022 May 19;15(10):3643.
doi: 10.3390/ma15103643.

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

Chunyang Zhang  1 , Xi Wei  1 , Chaocan Zhang  1 , Yinchun Li  1 , Yitian Sheng  1 , Shu Peng  1
Affiliations

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

Chunyang Zhang et al. Materials (Basel). .

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.

Keywords: bentonite; hydraulic conductivity; osmotic pressure; polymer-modified; self-healing; swell index.

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Conflict of interest statement

There are no conflicts of interest to declare.

Figures

Figure 1
Figure 1
Schematic diagram of PMBS preparation.
Figure 2
Figure 2
Diagram of the hydraulic conductivity test configuration.
Figure 3
Figure 3
(a) XRD patterns of different polymer-modified bentonites, (b) XRD patterns of PMB with different content of APAM.
Figure 4
Figure 4
Particle size distribution of different polymer-modified bentonite colloids.
Figure 5
Figure 5
Comparison of the infrared absorption spectroscopy of BT and PMB.
Figure 6
Figure 6
(a) SEM images of BT, (b) and (c) SEM images of PMB, (d) SEM image of PMBS.
Figure 7
Figure 7
The free swell index of PMB with different polymer content.
Figure 8
Figure 8
Change of hydraulic conductivity with respect to APAM content.
Figure 9
Figure 9
Schematic diagram of PMBS impermeability principle.
Figure 10
Figure 10
Osmotic pressure of bentonite colloids with different mass concentrations.
Figure 11
Figure 11
Change in hydraulic conductivity of BS and PMBS under different hydraulic pressure (a) BS, (b) PMB1S, (c) PMB2S, (d) PMB3S, (e) PMB4S, (f) PMB5S.
Figure 11
Figure 11
Change in hydraulic conductivity of BS and PMBS under different hydraulic pressure (a) BS, (b) PMB1S, (c) PMB2S, (d) PMB3S, (e) PMB4S, (f) PMB5S.
Figure 12
Figure 12
(a) The relationship between hydraulic conductivity and time for PMBS with different damage degrees, (b) the change of PMBS with different damage degrees over 120 h.
See this image and copyright information in PMC

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