2 results
Purification of Iranian bentonite for organoclay synthesis for use in clay–polymer composites
- Faraz Shabani Moghaddam, Hajar Ghanbari, Seyed Mohammad Mirkazemi, Fatemeh Ahmadi
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- Journal:
- Clay Minerals , FirstView
- Published online by Cambridge University Press:
- 29 April 2024, pp. 1-13
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Polymer-based composites modified with organoclay are economically beneficial candidates for a variety of applications. Different types of impurities accompany montmorillonite phases in various bentonites, which impact the quality and cost of organoclays and final composites. To obtain organoclays for clay composite applications, eight Iranian raw bentonites from different geographical locations were selected as the candidates and characterized by X-ray diffraction (XRD). Sample IB was chosen due to its high purity and lower cristobalite content than the other samples. It was purified by centrifugation or sedimentation methods using a sodium hexametaphosphate (NaHMP) dispersant. The cation-exchange capacity (CEC) was measured for bentonite before and after purification by sedimentation, and it showed a significant increase from 6.944 to 12.128 eq g–1, confirming successful purification. Organoclays were prepared using purified bentonite (sedimentation method) with two surfactants (cetyltrimethylammonium bromide and octadecylamine), and the amount of octadecylamine was optimized. Purified bentonite and organoclay were characterized by XRD, scanning electron microscopy (SEM) and X-ray fluorescence. The results indicate that most of the impurities were removed after purification, and the interlayer space of organoclays increased to 35 Å in the optimized sample prepared with an amount of octadecylamine that was twice the CEC in purified bentonite. The prepared organoclay was used to improve low-density polyethylene (LDPE) polymer properties. The clay–polymer composite properties were studied by field emission SEM, thermogravimetric analysis and tensile strength tests. The organoclay was fully dispersed in the LDPE matrix and in the sample with 5 wt.% of organoclay, where Ti (the temperature at which 10% of the sample is decomposed) and T50% (the midpoint of degradation) were 17°C and 13°C greater than those of polyethylene, respectively. Additionally, the sample residue with 5 wt.% of organoclay at 600°C was 43.4%. The tensile strength of polyethylene increased from 8.67 to 9.03 MPa in the sample with 4 wt.% of organoclay.
Optimized purification procedure for Iranian calcium bentonite for producing montmorillonite nanosheets
- Fatemeh Ahmadi, Hajar Ghanbari, Faraz Shabani Moghaddam, Rahim Naghizadeh
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- Journal:
- Clay Minerals / Volume 57 / Issue 2 / June 2022
- Published online by Cambridge University Press:
- 27 October 2022, pp. 120-130
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In polymer composites, montmorillonite nanosheets are crucial as fire retardants, reinforcers, anti-corrosives, detoxifying agents and ultraviolet-protection agents. However, the quality of montmorillonite nanosheets can be improved by optimizing the raw bentonite purification process in which undesirable phases are removed. Optimization of Iranian calcium bentonite purification for nanomontmorillonite synthesis considering various parameters based on various physical approaches to dispersion and ultrasonication was investigated; the calcium bentonite purification was performed using sodium hexametaphosphate followed by either sedimentation or centrifugation, and the nanomontmorillonite synthesis was performed using ultrasonic treatment. The effects of suspension concentration, milling type, pH and centrifugation duration and speed on the separation of various impure phases were evaluated qualitatively and optimized. The raw and purified bentonite and the synthesized nanomontmorillonite were characterized using X-ray powder diffraction, X-ray fluorescence spectroscopy, Fourier-transform infrared spectroscopy and scanning electron microscopy. The cation-exchange capacity was also measured in the raw and purified samples. Optimal experimental conditions in the dispersed samples were achieved at a 2.5 wt.% concentration of bentonite suspension and planetary milling at pH 7. While the ultrasonic treatment was more effective than the dispersion approach for cristobalite elimination, a smaller lateral size of the montmorillonite sheets, optimized at 0.5 wt.% concentration of the suspension, was achieved. The increased cation-exchange capacity after the purification improved the exfoliation and delamination of montmorillonite nanosheets in the presence of cetyltrimethylammonium bromide as the surfactant. The interplanar spacing of (001) planes of 15 Å in raw bentonite shifted to 21 Å and 19 Å in purified and non-purified samples, respectively, after synthesis.