A novel polyaniline-modified CNT and graphene-based nanocomposite (2.32–7.34 nm) was prepared and characterized by spectroscopic methods. The specific surface area was 176 m²/g with 0.232 cm³/g as the specific pore volume. The nanocomposite was used to remove zinc and lead metal ions from water; showing a high removal capacity of 346 and 581 mg/g at pH 6.5. The data followed pseudo-second-order, intraparticle diffusion and Elovich models. Besides this, the experimental values obeyed Langmuir and Temkin isotherms. The results confirmed that the removal of lead and zinc ions occurred in a mixed mode, that is, diffusion absorption and ion exchange between the heterogeneous surface of the sorbent containing active adsorption centers and the solution containing metal ions. The enthalpy values were 149.9 and 158.6 J.mol⁻¹K⁻¹ for zinc and lead metal ions. The negative values of free energies were in the range of −4.97 to −26.3 kJ/mol. These values indicated an endothermic spontaneous removal of metal ions from water. The reported method is useful to remove the zinc and lead metal ions in any water body due to the high removal capacity of nanocomposite at natural pH of 6.5. Moreover, a low dose of 0.005 g per 30 mL made this method economical. Furthermore, a low contact time of 15 min made this method applicable to the removal of the reported metal ions from water in a short time. Briefly, the reported method is highly economical, nature-friendly and fast and can be used to remove the reported metal ions from any water resource.

This paper considers the synthesis of a novel nanocomposite based on reduced graphene oxide and oxidized carbon nanotubes modified with polyaniline and phenol-formaldehyde resin and developed through the carbonization of a pristine aerogel. It was tested as an efficient adsorbent to purify aquatic media from toxic Pb(II). Diagnostic assessment of the samples was carried out through X-ray diffractometry, Raman spectroscopy, thermogravimetry, scanning and transmission electron microscopy, and infrared spectroscopy. The carbonized aerogel was found to preserve the carbon framework structure. The sample porosity was estimated through nitrogen adsorption at 77 K. It was found that the carbonized aerogel predominantly represented a mesoporous material having a specific surface area of 315 m²/g. After carbonization, an increase in smaller micropores occurred. According to the electron images, the highly porous structure of the carbonized composite was preserved. The adsorption capacity of the carbonized material was studied for liquid-phase Pb(II) extraction in static mode. The experiment results showed that the maximum Pb(II) adsorption capacity of the carbonized aerogel was 185 mg/g (at pH 6.0). The results of the desorption studies showed a very low desorption rate (0.3%) at pH 6.5 and a rate of about 40% in a strongly acidic medium.

В статье представлена технология получения нанокомпозитного аэрогеля на основе окисленных углеродных нанотрубок (о-УНТ) и восстановленного оксида графена (в-ОГ), модифицированных полианилином и фенолформальдегидной смолой. Получение аэрогеля осуществлялось в автоклаве высокого давления в среде сверхкритического флюида – изопропанола. Комплексная диагностика синтезированного нанокомпозита осуществлялась методами сканирующей и просвечивающей электронной микроскопии, инфракрасной спектроскопии, рентгеновской дифрактометрии, спектроскопии комбинационного рассеяния. Параметры пористого пространства оценивали по адсорбции азота. Полученные электронные изображения свидетельствуют о том, что УНТ выступают в качестве структурообразователя, препятствуя агломерации графеновых листов. Также следует отметить, что в образцах обнаружены частицы полианилина сферической формы. Установлено, что нанокомпозитный аэрогель является мезопористым материалом с удельной поверхностью 289 м²/г. Проведено сравнение инфракрасных и Раман-спектров, а также рентгеновских дифрактограмм исходных материалов со спектрами аэрогеля. Согласно полученным результатам, нанокомпозит содержит совмещенные пики всех исходных материалов. После сушки в среде сверхкритического изопропанола сохраняется упорядоченная структура углеродного каркаса. Электронодонорные кислород- и азотсодержащие группы, которые идентифицируются по данным инфракрасной спектроскопии в составе композита, могут являться активными центрами для адсорбции ионов тяжелых металлов благодаря возможности формирования координационных связей. Сорбционная способность материала оценивалась на примере сорбции ионов тяжелых металлов, а именно – свинца, из модельных водных растворов. Для определения времени сорбции и механизма поглощения были проведены кинетические исследования адсорбции в ограниченном объеме. Обнаружено, что 99% загрязнителя сорбируется в первые 15 мин с достижением адсорбционной емкости равной 350 мг/г. С помощью моделей псевдо-первого и –второго порядка, модели Еловича и внутридиффузионных моделей установлен предполагаемый механизм адсорбции. Для цитирования: Кузнецова Т.С., Бураков А.Е., Пасько Т.В., Буракова И.В., Дьячкова Т.П., Меметова А.Е. Физико-химические и сорбционные свойства нанокомпозитного аэрогеля на основе модифицированных углеродных нанотрубок и графена. Изв. вузов. Химия и хим. технология. 2023. Т. 66. Вып. 3. С. 66-76. DOI: 10.6060/ivkkt.20236603.6726.

A technique is described for the preparation of a universal composite nanomaterial for effective sorption purification of water from pollutants of different chemical nature. The proposed material is a nanocomposite based on reduced graphene oxide, which is modified with polyaniline as a functional organic component and also includes oxidized carbon nanotubes as a reinforcing agent. The use of polyaniline makes it possible to substantially increase the activity and sorption capacity of the developed graphene material. A number of nanocomposites are developed, the preparation technologies of which differ in the final stage, i.e., the drying of the preliminarily obtained hydrogel. Furthermore, the effect of the additional stage of final sample carbonization is studied. The surface morphology of the materials is examined by scanning electron microscopy. The specific surface area and the parameters of the porous space are determined by nitrogen adsorption. The specific surface area of the materials increases in accordance with the choice of drying technology for the initial hydrogel (drying oven, 80 m²/g → freeze drying, 180 m²/g → supercritical drying, 290 m²/g), increases additionally after the carbonization stage, and reaches a value of about 350 m²/g. The sorption capacities of nanocomposites with respect to organic dyes methylene blue (MB) and sunset yellow (SY) and with respect to heavy metals (for example, zinc ions) are determined. It is found that the sorption value ranges from 1380 to 1800 mg/g for MB, from 159 to 300 mg/g for SY, and from 31 to 230 mg/g for zinc. At the same time, the sample processed under supercritical conditions with subsequent carbonization exhibits the best characteristics.

The paper deals with the development of a graphene-containing sorbent material based on activated rapeseed biochar. The physicochemical properties of the sorbent and features of its morphological structure were determined. The nanocomposite was found to have amorphous properties with a graphene-like structure. The morphological analysis confirmed the formation of internal carbon framework and external three-dimensional multilayer graphene structure, which is excellent for mass transfer between pollutants and adsorbent surface. The research also aimed to determine the important parameters of sorption of organic compounds, i.e. synthetic dyes Congo Red (CR) and Malachite Green (MG), on the developed material from aqueous solutions in a limited volume. According to the kinetic studies, the experimental sorption capacity of the material on MG was 1860 mg⋅g–1 (sorption time – 60 min) and 642 mg⋅g–1 on CR (sorption time – 15 min). The theoretical maximum adsorption capacity of the sorbent calculated by the Langmuir model reached values of 769.23 mg⋅g–1 for CR and 3333.33 mg⋅g–1 for MG. It is found that the extraction of dye molecules is controlled by the second-order reaction according to the pseudo-second-order model and proceeds mainly by a mixed-diffusion mechanism. The activation energy has a value of 0.01 kJ⋅mol–1 for CR molecules and 0.02 kJ⋅mol–1 for MG, confirming the physical mechanism of dye adsorption. The high efficiency of adsorption of organic dyes on graphene-containing sorption material based on activated rapeseed biochar was demonstrated, indicating the feasibility of its practical application in wastewater treatment.

The article proposes a method for producing polyaniline-modified nanocomposite cryogel based on oxidized carbon nanotubes and reduced graphene oxide. Phenol–formaldehyde resin has been used as a crosslinking agent. Cryogel has been obtained by freeze drying in vacuum. Then, the material has been subjected to a post-processing, i.e., the carbonization in a tubular furnace. The obtained nanocomposite has been subjected to the comprehensive diagnostics by the methods of scanning and transmission electron microscopy, IR spectroscopy, X-ray diffraction analysis, and Raman spectroscopy. The parameters of the pore space have been estimated by nitrogen adsorption. It has been found that the carbonized nanocomposite cryogel is a mesoporous material with a specific surface area of 299 m²/g. IR and Raman spectra and X-ray diffraction patterns of the starting materials have been compared with the spectra of the carbonized cryogel. According to the results obtained, the nanocomposite exhibits peaks of all starting materials. The sorption capacity of the material has been evaluated by the example of the sorption of ions of a heavy metal, lead, from model aqueous solutions. Kinetic studies of adsorption in a limited volume have been carried out to determine the mechanism and time of the adsorption. It has been revealed that 99% of the contaminant is sorbed during the first 15 min, while an adsorption capacity of 295 mg/g is reached. The Elovich model, pseudo-first- and pseudo-second-order models, and an intradiffusion model have been employed to confirm the proposed adsorption mechanism.