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Desorption of hydrolyzed poly(AM/DMDAAC) from bentonite and its decomposition in saltwater under high temperatures

  • Ling Lin EMAIL logo , Xin Li , Chenliang Shi and Yifan Mao
Published/Copyright: October 4, 2019
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e-Polymers
From the journal e-Polymers Volume 19 Issue 1

Graphical Abstract

Abstract

Under harsh conditions, the desorption of polyampholytes from bentonite (Bent) can affect the performance of drilling fluids. To study the desorption of polyampholyte from bentonite, partially hydrolyzed copolymers of acrylamide and diallyl dimethyl ammonium chloride (HPAD), containing carboxyl groups, quaternary ammonium groups and amide groups was synthesized via free radical copolymerization followed by hydrolyzation. The molecular structure of HPAD was characterized by 1H NMR and 13C NMR. The adsorption equilibrium of HPAD on Bent in the presence of 10 wt% NaCl was 106 mg·g–1. The adsorption-desorption behavior of HPAD on Bent was studied using a high pressure and high temperature (HPHT) filtration apparatus, to obtain the filtrate liquid and filter cakes. The content of HPAD in the filtration and the filter cakes was determined via UV and element analysis, respectively. As the temperature increased, the desorption of HPAD from Bent accelerated owing to molecular thermal motion and thermal degradation of the adsorptive groups. Notably, the decomposition rate of the amide group was more than twice that of the quaternary ammonium group. The critical temperature for HPAD desorption was 135°C, as the decomposition of the adsorptive groups became predominant over intensified molecular thermal motion at high temperatures.

Keywords: bentonite; acrylamide; diallyl dimethyl ammonium chloride; desorption; decomposition

1 Introduction

Polyampholytes have broad applications as chemical additives, e.g. filtration reducers, in water-based drilling fluids (1, 2). In mud, both polyampholytes and bentonite (Bent) play as the main components contributing to the viscosity of drilling fluids. Polyampholytes ionize in aqueous solution and adsorb on Bent via both electrostatic attraction and hydrogen bonding (3). This process provides Bent with both electrostatic repulsion and entropic repulsion, which contributes to the colloidal stability of Bent. However, if the amphoteric polymers rapidly desorb from Bent under harsh conditions, the colloidal properties of Bent suffered considerably, resulting in the deterioration of rheological properties of drilling fluids. Therefore, the desorption of polyampholyte from Bent is a crucial factor in the performance of drilling fluid under harsh conditions, especially under high temperature, high pressure and high salinity (3, 4).

Previous research on the adsorption of amphoteric polymers in aqueous solution has mainly focused on the adsorption amount and the conformation of polymer chains, typically at moderate temperatures and in deionized water (5, 6). The adsorption kinetics of polyampholyte on expanded perlite under 25°C to 55°C were described by the pseudo first-order kinetics model (7). The adsorption of polyampholytes or polyacrylamide-based materials on Bent has been studied previously (3,8). Yan and Zhang reported that the adsorption of charged PAMs on montmorillonite and kaolinite followed the order cationic > non-ionic > anionic, and that the desorption of PAMs from clay seemed to be impossible (9).

To the best of our knowledge, the adsorption/desorption of polymers on adsorbents, especially Bent, in aqueous solution at high temperatures has rarely been studied. Wang et al. found that the adsorption of polyvinyl alcohol on Bent increased from 30°C to 60°C (10). This phenomenon may be a result of accelerated adsorption compared with an original low adsorption or the creation of new adsorptive sites on the adsorbent surface (11). Other papers reporting the effect of temperature on the adsorption behavior of polyampholyte have mainly focused on mild temperatures (12, 13). The degradation of polyacrylamide-based polymers under high temperature has been studied by Jiang et al. (14). The authors argued that carboxylic groups of partially hydrolyzed polyacrylamide, which were the hydrolyzation products of amide groups, acted as catalysts of the further hydrolyzation of amide groups under heating.

As the desorption mechanism of polyampholyte has rarely been studied under harsh conditions, this study was aimed at obtaining a quantitative description of the factors that affect the desorption of partially hydrolyzed poly(acrylamide/diallyl dimethyl ammonium chloride) (HPAD) at high temperatures in saltwater. Both molecular thermal motion and adsorptive groups degradation were expected to influence the desorption of HPAD from Bent. The former factor was found to have the greatest influence on HPAD desorption from Bent at temperatures below 135°C, whereas the latter factor became more influential at higher temperatures.

2 Materials and methods

2.1 Materials and preparation

Acrylamide, NaHSO3, MnCl2, NaOH, methyl orange, indigo carmine, AgNO3, K2CrO4, Na2CO3, NaCl and ethanol were purchased from Chengdu Kelong Chemical Company, China. Diallyl dimethyl ammonium chloride (60 wt% in water) was obtained from Sinopharm Chemical Reagent Company, Shanghai, China. All of these chemicals were analytic reagent and used as received.

Bent was provided by Zhongfei Xiazijie Bentonite Company, Xinjiang, China. Bent was purified according to the following procedure: first, 5 wt% Bent and 0.25 wt% Na2CO3 were added to deionized water, and the mixture was well mixed and hydrated at room temperature for 24 h; second, the mixture was filtered using vacuum pump (15-20 μm pore size filter paper); third, the filtration was centrifugated at 10000 rpm for 20 min, and Bent at the bottom of centrifuge tube was dried at 70°C for 16 h under vacuum (10–3 Torr); finally, dried Bent was ground and sifted with a screen mesh (#100) and then stored in a desiccator until use. The components of Bent are provided in the supporting files, as determined using China’s O&G Industrial Standard SY/T 5163-2010.

2.2 Polymer synthesis

Poly(acrylamide/diallyl dimethyl ammonium chloride) (PAD), was synthesized as follows: first, acrylamide and diallyl dimethyl ammonium chloride were mixed together in deionized water at a molar ratio of 5:1; second, the mixture was purged with N2 for 20 min and the flask was sealed with a rubber plug; third, 0.1 wt% MnCl2 in deionized water and 0.05% NaHSO3 in deionized water were injected into the mixture, respectively, and the flask was heated in water bath at 60°C for 12 h; fourth, the reaction product was precipitated (twice) from water using 200 mL of CH3CH2OH, which changed the polarity of the solution and therefore lowered the solubility of the polymers, and then dried under vacuum over under 60°C for 12 h.

HPAD was prepared by hydrolyzing PAD in alkaline solution (10 wt% NaOH) under 85°C for 16 h. Subsequently, the product was precipitated (four times) from water using 200 mL of CH3CH2OH, and then dried under vacuum (10–3 Torr) at 60°C for 12 h.

2.3 Sample characterization

The cation exchange capacity of the Bent (75.81 cmol/100g) was determined according to China industrial standard SY/T 5395-2016. The content of quaternary ammonium units and carboxyl units in polymers was determined using a titration method in accordance with China Standard GB 12005.6-89. The cationic group content was measured by titrating a 0.05 mol·L−1 AgNO3 solution against an aqueous PAD solution, with K2CrO4 (5 wt% in water) as the indicator. The titration endpoint was characterized by a change of the solution color from bright yellow to brick red. HPAD was assumed to inherit the cationic group content of PAD. The anionic group content was measured by titrating a 0.1 mol·L–1 HCl solution against an aqueous HPAD solution, with a mixture of 0.1 wt% methyl orange and 0.25 wt% indigo carmine as the indicator, and the endpoint was characterized by a color change from yellowish green to French gray. The intrinsic viscosities of polymers were tested in a 1 mol·L–1 NaCl aqueous solution using an Ubbelohde capillary viscometer with a capillary diameter of 0.55-0.60 mm (Shanghai Shenyi Glass Instrument Co. Ltd., China) at 30 ± 0.1°C, according to China Standard GB/T 1632-1993. The infrared transmission spectra (500 cm–1 to 4000 cm–1, 0.25 cm–1 resolution) of the polymers were obtained with WQF-520 FT-IR (Beijing Rayleigh Analytical Instrument Corporation, China). The 1H NMR and 13C NMR spectra (narrow bore, static, relaxation time = 2 s) of the polymers in D2O were recorded using a Bruker AscendTM 400 MHz NMR spectrometer at 25°C. UV-Vis absorption spectra (190-1100 nm, 2 nm bandwith) were collected using an LS6 spectrophotometer (Shanghai INESA Scientific Instrument Co., Ltd, China) at 30°C. After treatment using the “starch – cadmium iodide” method, the amide groups of HPAD exhibited an absorption maximum at 525 nm (15). The linear relationship between the amide group content and the absorbance was used to calculate the concentration of HPAD in aqueous solution. The analysis of elements and function groups on the surface of adsorbed Bent were determined using X-ray photoelectron spectroscopy (XPS, Thermo Scientific Escalab 250Xi) with a Mg Kα X-ray source (1254 eV of photons). The high-resolution scans were performed over the 392-410 eV ranges (N1s spectra) for polymer samples. The software Avantage (Thermo Scientific, America) was used to analyze the obtained XPS spectra peaks.

The adsorption of polymers on Bent under 30°C was tested according to the following procedure: first, a Bent solution and a polymer solution were prepared and aged separately at room temperature for 12 h; second, the two solutions were mixed, and 10 wt% NaCl was added, and the mixture was aged at 30°C in a water bath; third, the mixture was centrifuged at 10000 rpm for 20 min; fourth, the supernatant was treated using the “starch–cadmium iodide” method, and then the polymer content was determined via UV-Vis spectroscopy, as described above; fifth, the precipitated Bent was rinsed with deionized water for three times, and then dried under vacuum (10–3 Torr) at 70°C for 16 h. The weight percentage of carbon (wC) and nitrogen (wN) in the Bent samples (15 ± 2 mg) was tested in a combustion tube on a Vario EL III elemental analysis device (Elementar, Germany) in CHNS mode at 1150°C. The molar ratio of C/N can be calculated as below:

(1)nCnN=wC/12wN/14

The polymer desorption experiments under high temperatures (≥ 100°C) were carried out on a high pressure and high temperature (HPHT) filtrate apparatus (Qingdao Tongchun Company, China) as shown in Figure 1. first, a saltwater mixture containing both Bent and the polymer was prepared following the same steps under 30°C; second, the suspension was transferred to a steel oven with a filter paper (pore size of 1 μm) at the bottom, and the oven was heated to target temperatures in the HPHT filtrate apparatus; third, the bottom valve of the oven was opened every 15 min to collect the filtration, and a filter cake was obtained when all the liquid in the oven was released; fourth, the filter cake was rinsed with deionized water three times at room temperature; fifth, the polymer contents in the filtration and filter cakes were determined according to the adsorption test procedure at 30°C.

Figure 1 Desorption experiments using HPHT filtrate apparatus.
Figure 1

Desorption experiments using HPHT filtrate apparatus.

3 Results

3.1 Molecular structure characterization

The intrinsic viscosity and composition of polymer samples, as determined by viscometry and titration methods, are listed in Table 1.

Table 1

Viscosities and compositions of polymer samples.

Sample[η] (mL·g-1)Carboxyl unit (mol%)Quaternary ammonium unit (mol%)Amide unit (mol%)
PAD432.3010.4889.52
HPAD606.822.0910.4867.43

The amphoteric polymer HPAD was the hydrolyzed product of PAD, and the content of cationic groups was assumed to be equal in these two polymers. The polyampholyte HPAD interacted with Bent via electrostatic attraction and hydrogen bonding, with both quaternary ammonium groups and amide groups acting as the adsorptive groups which interacted with the surfaces and edges of Bent in aqueous solutions.

The synthesis of HPAD was confirmed by the NMR test results as shown in Figure 2.

Figure 2 1H NMR spectrum (a) and 13C NMR spectrum (b) of HPAD.
Figure 2

1H NMR spectrum (a) and 13C NMR spectrum (b) of HPAD.

Signals corresponding to amide groups, carboxyl groups, and quaternary ammonium groups were observed in both the 1H NMR and 13C NMR spectra of HPAD. In addition, although both monomers (acrylamide and diallyl dimethyl ammonium chloride) contained C=C groups, no C=C signals (normally located at 100-150 ppm) were observed in the 13C NMR spectrum of HPAD. These result indicated that HPAD was successfully prepared via free radical polymerization followed by hydrolyzation.

3.2 Adsorption of HPAD on Bent under 30°C

The effect of stirring time and the amount of polymer added on the adsorption of HPAD on Bent at 30°C were studied, as shown in Figure 3.

Figure 3 The adsorption kinetics (a) and thermodynamics (b) of HPAD on Bent at 30°C.
Figure 3

The adsorption kinetics (a) and thermodynamics (b) of HPAD on Bent at 30°C.

In the adsorption kinetics experiment, the original mixture contained 0.1 wt% HPAD, 1 wt% Bent, and 10 wt% NaCl. The pH of the mixture was approximately 7. As shown in Figure 3a, adsorption equilibrium was reached after 75 min. Therefore, a mixing time of 75 min was used to prepare saltwater mixture for the following adsorption experiments.

Next, the relationship between the concentration of HPAD and its adsorption on Bent at 30°C was determined (Figure 2b) by adding various amount of HPAD to 1 wt% Bent suspension with 10 wt% NaCl. Adsorption equilibrium was observed when the concentration of HPAD reached 0.3 wt%, and the maximum adsorption amount was approximately 106 mg·g–1.

3.3 Desorption of HPAD from Bent at high temperatures

Subsequently, the desorption of HPAD from Bent in the presence of NaCl at high temperatures was studied using an HPHT filtrate apparatus. Before being heated, 0.1 wt% HPAD was allowed to reach adsorption equilibrium on Bent in saltwater mud (1 wt% Bent + 10 wt% NaCl) at 30°C by stirring the mixture for 75 min. After reaching the target temperature, both the filtration and the filter cake were collected to analyze the HPAD contents. The former was assumed to contain HPAD desorbed from Bent, whereas the later was assumed to contain HPAD still adsorbed on Bent; a proportion of decomposed HPAD, in the form of small molecules, could not be detected in either the filtration or the filter cake.

As HPAD is applied as a chemical additive of water-based drilling fluids in the oil and gas industry, it will be subjected to high temperatures, normally ranging from 110°C to 200°C, during drilling engineering (1). Therefore, the temperature of 115-175°C was used in the following desorption experiments. The content of HPAD (CHPAD) in the collected filtration was calculated based on the content of amide groups (Camide group) in the filtration, as determined using UV-Vis spectroscopy, and the molar percentage of amide group in HPAD (Table 1), as follows:

(2)CHPAD=Camide  group0.6743

The content of HPAD in in the filtration at various high temperatures is shown in Figure 4.

Figure 4 (a) Content of HPAD in the filtration at high temperatures; (b) Amounts of HPAD adsorbed on Bent at 175°C (N and C refers to the HPAD content calculated based on wN and wC of the element tests, respectively, as determined by elemental analysis).
Figure 4

(a) Content of HPAD in the filtration at high temperatures; (b) Amounts of HPAD adsorbed on Bent at 175°C (N and C refers to the HPAD content calculated based on wN and wC of the element tests, respectively, as determined by elemental analysis).

The content of HPAD in the filtration first increased and then decreased as the temperature increased, indicating that the total amount of adsorbed HPAD and decomposed HPAD first decreased and then increased. This phenomenon was caused by intensified thermal molecular motion and accelerated decomposition of the adsorptive groups. The former factor contributed to the desorption of HPAD from Bent into the filtration while the latter resulted in the detection of less HPAD in either the filtration or filter cakes. As the temperature rose from 115°C to 135°C, desorption resulting from the disruption of the electrostatic interactions between HPAD and Bent was the predominant behavior and had a much greater effect than the decomposition of the adsorptive groups, resulting in a positive correlation between the HPAD content in the filtration and the temperature. As the temperature increased further to above 135°C, the HPAD content in the filtration decreased because the decomposition of adsorptive groups became more prevalent, leading to a rapid reduction of the polymer content.

The content of HPAD in filter cakes after being heated under 175°C was shown in Figure 4b. The contents of HPAD in the filter cakes were calculated based on the content of carbon and nitrogen in the filter cakes (wN and wC, as determined by elemental analysis) and the weight percentage of carbon and nitrogen in HPAD (49.4 wt% and 12.7 wt%, respectively; Table 2), as follows:

(3)HPADbased  on  C(mg⋅g−1)=wC/0.4941−wC/0.494×100
(4)HPADbased on N(mg⋅g−1)=wN/0.1271−wN/0.127×100
Table 2

Effect of aging on relative contents of chemical groups in HPAD.

Time (min)Aδ3.1/Aδ3.5
151.375
301.048
450.786
900.365

  1. δ3.1 and δ3.5 correspond to H and G (Figure 2a)

Interestingly, the content of HPAD in the filter cakes was almost constant if calculated based on wC, indicating that the carbon-containing groups in HPAD were not readily decomposed by heating. However, if calculated based on wN, the content of HPAD in the filter cakes showed a continuous loss, revealing that the N-based groups were much less stable than alkyl groups. A possible explanation for the difference in behavior is that even the N-based adsorptive groups were decomposed, HPAD chains were still entrapped by adjacent Bent particles and could not be released into the filtration. Furthermore, we can infer that some HPAD decomposed during the original heating process, resulting in the HPAD content in filter cakes calculated based on wN less than that calculated based on wC at 15 min.

3.4 Degradation of HPAD at high temperatures

The degradation of HPAD at high temperatures was examined using 2 wt% HPAD in saltwater (10 wt% NaCl). After stirring for 10 h under 30°C, the mixture was aged at varied temperatures for various time. Subsequently, the polymer was precipitated by adding ethanol and then was dried under vacuum (10–3 Torr) at 60°C for 12 h. Finally, the intrinsic viscosities of the aged HPAD samples were determined. Considering that 135°C was the critical temperature at which the decomposition of HPAD accelerated, the aging temperatures of 115°C, 135°C, and 175°C were investigated (Figure 5).

Figure 5 Intrinsic viscosities of HPAD aged under high temperatures.
Figure 5

Intrinsic viscosities of HPAD aged under high temperatures.

Over 90 min, the intrinsic viscosity of HPAD varied little at 115°C, but it exhibited a decrease at higher temperatures, with almost three-quarters of the initial intrinsic viscosity lost at 175°C. Pronounced decreases in the intrinsic viscosity were observed at 135°C and 175°C, indicating that the decomposition of HPAD in saltwater was accelerated at the temperatures higher than 115°C.

To better understand the degradation of the chemical groups along the chains, IR and 1H NMR analysis of the aged samples were conducted. In the IR spectra (Figure 6a), the band near 2930 cm–1 was attributed to the asymmetric stretching vibration of methyl, methylene and methylidyne groups; the band at 1610 cm–1 was attributed to the C=O of amide groups (16); the bands at 1450 cm–1 and 1405 cm–1 were attributed to asymmetric bending vibrations and symmetric bending vibrations of methyl, methylene and methylidyne groups; the band near 1310 cm–1 was attributed to C–N of five-membered rings. As the treatment temperature increased, the degradation of methyl groups in the five-membered ring became more prominent than the decomposition of other chemical groups.

Figure 6 IR (a) and 1H NMR (b) spectra of HPAD aged under different temperatures (the A-H labels are assigned in Figure 2a).
Figure 6

IR (a) and 1H NMR (b) spectra of HPAD aged under different temperatures (the A-H labels are assigned in Figure 2a).

As shown by the NMR spectra in Figure 6b, the relative contents of chemical groups varied with aging duration. Based on the relative peak areas of G and H, HPAD suffered a higher loss of –CH3 linked to five-membered ring than –CH2– moieties in five-membered rings (Table 2), which is in good agreement with the IR analysis results.

4 Discussion

The desorption of HPAD from Bent can be attributed to two factors: first, molecular thermal movements of the polyampholyte disrupt the electrostatic attraction between the adsorptive chemical groups and the Bent surface; second, the adsorptive groups, including positively charged quaternary ammonium groups and amide groups, are degraded. Assuming that these factors are the cause of desorption, HPAD in the filtration corresponds to the polymers no longer bound to Bent, as calculated based on the content of amide group with an initial HPAD concentration of 0.1 wt%; HPAD in the filter cakes represents the polyampholyte that still adsorbed on Bent, as calculated based on the content of nitrogen with an initial Bent concentration of 1 wt%; and the remainder corresponds to decomposed HPAD that cannot be detected either in the filtrate liquid or on Bent using titration or element analysis methods. To evaluate the contribution of the two factors to the desorption of HPAD from Bent quantitatively, we calculate the percentage of these three kinds of HPAD as below:

(5)HPADdesorbed(%)=HPADdesorbed(mg⋅L−1)HPADoriginal(mg⋅L−1)                         =Camide  group(mg⋅L−1)0.6743×1000mg⋅L−1
(6)HPADadsorbed(%)=Sampleoriginal(g)×wN/0.1271−wN/0.127                        ×Bentoriginal(g)Sampleoriginal(g)×1HPADoriginal(g)                        =wN0.127×11×10.1=10×wN0.127
(7)HPADdecomposed(%)=1−HPADdesorbed(%)                               −HPADadsorbed(%)

The calculated amounts of desorbed HPAD in the filtrate, adsorbed HPAD in the filter cakes, and decomposed HPAD are summarized in Figure 7.

Figure 7 Calculated amounts of desorbed HPAD, adsorbed HPAD and decomposed HPAD at 175°C.
Figure 7

Calculated amounts of desorbed HPAD, adsorbed HPAD and decomposed HPAD at 175°C.

When the saltwater mixture containing HPAD and Bent was heated under 175°C, Bent-adsorbed HPAD experienced an accelerated desorption and decomposition, as the amount of HPAD adsorbed on Bent was much lower than the amount of desorbed HPAD in the filtration. The difference between the amounts of these two kinds of HPAD became smaller over time, indicating that the content of desorbed HPAD in the filtration declined more rapidly at such a high temperature. However, a steady increase in the calculated percentage of decomposed HPAD was observed. At approximately 30 min, the amounts of decomposed HPAD and desorbed HPAD were approximately equal. Therefore, we can infer that before 30 min, the intensified thermal motion of HPAD dominated the desorption process, whereas the accelerated degradation of adsorptive groups became more important at longer times.

It should be noted that the percentages of desorbed HPAD in the filtration and adsorbed HPAD in the filter cakes (Figure 7) were calculated based on the content of amide groups and the content of N respectively. However, if the content of adsorbed HPAD in the filter cakes was calculated based on the C content, the trend should be quite different, according to the data in Figure 4a. We still use the content of N to calibrate the content of HPAD in the filtration and filter cakes as both types of adsorptive groups in HPAD contain N.

We calculated the nC/nN of HPAD in filter cakes under 175°C based on wC and wN values determined by element analysis, as shown in Figure 8a.

Figure 8 (a) The C/N (in molar ratio) of HPAD in filter cakes under 175°C; (b) N-based groups in HPAD aged at 175°C, as determined using XPS.
Figure 8

(a) The C/N (in molar ratio) of HPAD in filter cakes under 175°C; (b) N-based groups in HPAD aged at 175°C, as determined using XPS.

As the heating time increased, the nC/nN ratio increased from the initial value of 4.52. Acceleration was observed after 60 min, indicating that N-based groups, namely quaternary ammonium groups and amide groups, underwent enhanced decomposition at 175°C. The nC/nN ratio of aged HPAD samples revealed that the loss of N-based groups HPAD in saltwater at 175°C was considerably greater than the loss of alkyl groups. Considering that these two types of N-based groups acted as the adsorptive groups, HPAD lost its capacity to adsorb on Bent.

These result was in good agreement with the recognized fact that alkyl groups are much more stable than amide groups and quaternary ammonium groups under high temperatures. The degradation of –CH3 linked to the five-member rings likely accounted for the decrease in the C content, in accordance with the 1H NMR spectrum in Figure 6b. Combined with the drop in the HPAD content in the filtration, as calculated based on amide groups, the huge loss (50%) of N content likely corresponds to the decomposition of amide groups rather than quaternary ammonium groups.

To obtain a better understanding of the degradation of N-contained groups, a series of XPS measurements were carried out and the result are summarized in Figure 8b.

The N content of HPAD in the filtration originated from either quaternary ammonium groups or amide groups. Based on the amide groups in XPS spectra (14), the amount of amide groups decreased continually with increasing heating times, whereas the content of quaternary ammonium groups steadily increased. At 15 min, –N+ in the five-member ring accounted for approximately 13 mol%, corresponding well with the data in Table 1, while –N+ accounted for more than 25 mol% at 90 min. Thus, amide groups decomposed much faster than the positively charged groups, indicating that the latter is more likely to act as the adsorptive groups under heating. In aqueous solution, the degradation of amide groups could experience a self-acceleration process, as the pKa of H2O increased at higher temperatures (17, 18).

5 Conclusion

In this study, a polyampholyte, HPAD, comprising quaternary ammonium groups, carboxyl groups and amide groups was synthesized via free radical copolymerization followed by hydrolyzation using NaOH. The thermal stability and the adsorption of HPAD on Bent in the saltwater were studied. The maximum adsorption of HPAD on Bent was around 106 mg·g–1 with 0.3 wt% HPAD and 1 wt% Bent in saltwater. Increasing temperature stimulated the desorption of HPAD from Bent in saltwater through increased molecular thermal motion and enhanced thermal degradation of adsorptive groups. At temperatures below 135°C, the former factor dominated the desorption of HPAD, whereas the latter became more influential at higher temperatures. At higher temperatures, the positively charged quaternary ammonium groups were better adsorptive groups because the amide groups were more prone to decomposition. As the desorption mechanism of HPAD at 115-175°C has been clarified, the next step of our research is to study the conformation of polyampholyte on Bent and enhance the adsorption temperature to over 200°C. Researchers dealing with the development of polyampholyte-based additives resistant to high temperatures (> 150°C) for drilling ultra-deep wells may benefit from this study.

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Abbreviations

Bent

bentonite

Camide group

content of amide groups

C HPAD

content of HPAD

HPAD

hydrolyzed poly(acrylamide/diallyl dimethyl ammonium chloride

HPHT

high-pressure and high-temperature

nC

molar percentage of carbon

nN

molar percentage of nitrogen

PAD

poly(acrylamide/diallyl dimethyl ammonium chloride)

wC

weight percentage of carbon

wN

weight percentage of nitrogen

Acknowledgement

This research was funded by the National Natural Science Foundation of China (41702391) and the Young Scholars Development Fund of SWPU (201599010037).

  1. Author contributions:

    Design of the study: L.L.; The execution of the study: L.L. X.L. C.S. and Y.M.; The data analysis L.L. and X.L.; The writing of the manuscript: L.L. and X.L.

  2. Conflicts of interest:

    The authors declare no conflict of interest.

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Received: 2019-07-05
Accepted: 2019-08-03
Published Online: 2019-10-04

© 2019 Lin et al., published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 Public License.

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https://doi.org/10.1515/epoly-2019-0056
Keywords for this article
bentonite; acrylamide; diallyl dimethyl ammonium chloride; desorption; decomposition
Creative Commons
BY 4.0

Articles in the same Issue

  1. Special Issue: Polymers and Composite Materials / Guest Editor: Esteban Broitman
  2. A novel chemical-consolidation sand control composition: Foam amino resin system
  3. Bottom fire behaviour of thermally thick natural rubber latex foam
  4. Preparation of polymer–rare earth complexes based on Schiff-base-containing salicylic aldehyde groups attached to the polymer and their fluorescence emission properties
  5. Study on the unsaturated hydrogen bond behavior of bio-based polyamide 56
  6. Effect of different nucleating agent on crystallization kinetics and morphology of polypropylene
  7. Effect of surface modifications on the properties of UHMWPE fibres and their composites
  8. Thermal degradation kinetics investigation on Nano-ZnO/IFR synergetic flame retarded polypropylene/ethylene-propylene-diene monomer composites processed via different fields
  9. Properties of carbon black-PEDOT composite prepared via in-situ chemical oxidative polymerization
  10. Regular articles
  11. Polyarylene ether nitrile and boron nitride composites: coating with sulfonated polyarylene ether nitrile
  12. Influence of boric acid on radial structure of oxidized polyacrylonitrile fibers
  13. Preparing an injectable hydrogel with sodium alginate and Type I collagen to create better MSCs growth microenvironment
  14. Application of calcium montmorillonite on flame resistance, thermal stability and interfacial adhesion in polystyrene nanocomposites
  15. Modifications of microcrystalline cellulose (MCC), nanofibrillated cellulose (NFC), and nanocrystalline cellulose (NCC) for antimicrobial and wound healing applications
  16. Polycation-globular protein complex: Ionic strength and chain length effects on the structure and properties
  17. Improving the flame retardancy of ethylene vinyl acetate composites by incorporating layered double hydroxides based on Bayer red mud
  18. N, N’-sebacic bis(hydrocinnamic acid) dihydrazide: A crystallization accelerator for poly(L-lactic acid)
  19. The fabrication and characterization of casein/PEO nanofibrous yarn via electrospinning
  20. Waterborne poly(urethane-urea)s films as a sustained release system for ketoconazole
  21. Polyimide/mica hybrid films with low coefficient of thermal expansion and low dielectric constant
  22. Effects of cylindrical-electrode-assisted solution blowing spinning process parameters on polymer nanofiber morphology and microstructure
  23. Stimuli-responsive DOX release behavior of cross-linked poly(acrylic acid) nanoparticles
  24. Continuous fabrication of near-infrared light responsive bilayer hydrogel fibers based on microfluidic spinning
  25. A novel polyamidine-grafted carboxymethylcellulose: Synthesis, characterization and flocculation performance test
  26. Synthesis of a DOPO-triazine additive and its flame-retardant effect in rigid polyurethane foam
  27. Novel chitosan and Laponite based nanocomposite for fast removal of Cd(II), methylene blue and Congo red from aqueous solution
  28. Enhanced thermal oxidative stability of silicone rubber by using cerium-ferric complex oxide as thermal oxidative stabilizer
  29. Long-term durability antibacterial microcapsules with plant-derived Chinese nutgall and their applications in wound dressing
  30. Fully water-blown polyisocyanurate-polyurethane foams with improved mechanical properties prepared from aqueous solution of gelling/ blowing and trimerization catalysts
  31. Preparation of rosin-based polymer microspheres as a stationary phase in high-performance liquid chromatography to separate polycyclic aromatic hydrocarbons and alkaloids
  32. Effects of chemical modifications on the rheological and the expansion behavior of polylactide (PLA) in foam extrusion
  33. Enhanced thermal conductivity of flexible h-BN/polyimide composites films with ethyl cellulose
  34. Maize-like ionic liquid@polyaniline nanocomposites for high performance supercapacitor
  35. γ-valerolactone (GVL) as a bio-based green solvent and ligand for iron-mediated AGET ATRP
  36. Revealing key parameters to minimize the diameter of polypropylene fibers produced in the melt electrospinning process
  37. Preliminary market analysis of PEEK in South America: opportunities and challenges
  38. Influence of mid-stress on the dynamic fatigue of a light weight EPS bead foam
  39. Manipulating the thermal and dynamic mechanical properties of polydicyclopentadiene via tuning the stiffness of the incorporated monomers
  40. Voigt-based swelling water model for super water absorbency of expanded perlite and sodium polyacrylate resin composite materials
  41. Simplified optimal modeling of resin injection molding process
  42. Synthesis and characterization of a polyisocyanide with thioether pendant caused an oxidation-triggered helix-to-helix transition
  43. A glimpse of biodegradable polymers and their biomedical applications
  44. Development of vegetable oil-based conducting rigid PU foam
  45. Conetworks on the base of polystyrene with poly(methyl methacrylate) paired polymers
  46. Effect of coupling agent on the morphological characteristics of natural rubber/silica composites foams
  47. Impact and shear properties of carbon fabric/ poly-dicyclopentadiene composites manufactured by vacuum‐assisted resin transfer molding
  48. Effect of resins on the salt spray resistance and wet adhesion of two component waterborne polyurethane coating
  49. Modifying potato starch by glutaraldehyde and MgCl2 for developing an economical and environment-friendly electrolyte system
  50. Effect of curing degree on mechanical and thermal properties of 2.5D quartz fiber reinforced boron phenolic composites
  51. Preparation and performance of polypropylene separator modified by SiO2/PVA layer for lithium batteries
  52. A simple method for the production of low molecular weight hyaluronan by in situ degradation in fermentation broth
  53. Curing behaviors, mechanical properties, dynamic mechanical analysis and morphologies of natural rubber vulcanizates containing reclaimed rubber
  54. Developing an epoxy resin with high toughness for grouting material via co-polymerization method
  55. Application of antioxidant and ultraviolet absorber into HDPE: Enhanced resistance to UV irradiation
  56. Study on the synthesis of hexene-1 catalyzed by Ziegler-Natta catalyst and polyhexene-1 applications
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  58. Desorption of hydrolyzed poly(AM/DMDAAC) from bentonite and its decomposition in saltwater under high temperatures
  59. Synthesis, characterization and properties of biomass and carbon dioxide derived polyurethane reactive hot-melt adhesives
  60. The application of a phosphorus nitrogen flame retardant curing agent in epoxy resin
  61. High performance polyimide films containing benzimidazole moieties for thin film solar cells
  62. Rigid polyurethane/expanded vermiculite/ melamine phenylphosphate composite foams with good flame retardant and mechanical properties
  63. A novel film-forming silicone polymer as shale inhibitor for water-based drilling fluids
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  65. Effect of salt and temperature on molecular aggregation behavior of acrylamide polymer
  66. Dynamics of asymmetric star polymers under coarse grain simulations
  67. Experimental and numerical analysis of an improved melt-blowing slot-die
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