Synthesis of optimal carbon dioxide adsorbent using modified multi-wall carbon nanotubes with 1,3-diaminopropane: concerning isotherms and regeneration.

Modification of multi-walled carbon nanotubes by 1,3-diaminopropane to increase CO2 adsorption capacity

Multi-walled carbon nanotubes (MWNTs) were modified by amidoxime group, characterized by fourier transform infrared spectrometer (FTIR). The adsorption experiments of Pb(Pb) on raw MWNTs and amidoxime group modified MWNTs(AO-MWNTs) were studied under different conditions. Results showed that, the adsorption capacities of Pb on raw MWNTs and AO- MWNTs primarily increased with the increasing pH, adsorption temperature and the initial Pb concentration. Under the condition of pH=7 and temperature was 50℃, the adsorption capacities reached the maximum. The adsorption equilibrium of raw-MWNTs on Pb reached balance in about 90min and the AO-MWNTs achieved stable in 60min.The adsorption process of AO-MWNTs could be better described by Freundlich model.

Highly efficient and rapid removal of a toxic dye: Adsorption kinetics, isotherm, and mechanism studies on functionalized multiwalled carbon nanotubes

Adsorption of Nile Blue A from Wastewater Using Magnetic Multi-Walled Carbon Nanotubes: Kinetics and Equilibrium Studies

Introduction The adsorption capacity of activated charcoal was systematically evaluated for five metal ions, lead, thallium, cesium, rubidium and lithium, with particular emphasis on elucidating the underlying adsorption mechanisms and ion selectivity patterns. Methods The surface structure of activated charcoal was characterized using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and temperature-programmed desorption mass spectrometry to identify potential functional groups involved in the adsorption of metal ions. The concentration of metal ions was measured by inductively coupled plasma-mass spectrometer. The effects of adsorption time, pH, and ion concentration were systematically studied. Adsorption kinetics were fitted to the pseudo-first-order and pseudo-second-order models to elucidate the dominant mechanism, representing physisorption and chemisorption, respectively. Adsorption isotherms were fitted to the Langmuir and Freundlich models to evaluate the adsorption capacity and behavior of activated charcoal. Results The surface of activated charcoal contains potential adsorption functional groups, including carboxyl, phenolic hydroxyl, carbonyl, and anhydride. The material exhibits adsorption of lead, thallium, cesium and rubidium ions, while showing no adsorption for lithium ions. Adsorption capacity increased with both pH (ranging from 2 to 6) and metal ion concentration. All adsorption processes followed the pseudo-second-order kinetic model, suggesting that chemisorption is the predominant adsorption mechanism. Adsorption isotherms showed lead, cesium and rubidium ions best fit the Langmuir model, while thallium followed the Freundlich model. Both Langmuir and Freundlich models indicated favorable adsorption under experimental conditions. The experimental adsorption capacity decreased in the order: lead (8.8 mg/g) > thallium (2.7 mg/g) > cesium (1.0 mg/g) > rubidium (0.7 mg/g) > lithium (0.0 mg/g). Discussion This study found that the adsorption capacity of activated charcoal for different metal ions is influenced by factors such as pH and metal ion concentration. As pH increased, the adsorption efficiency improved, suggesting that the highly acidic environment in the stomach (pH ≈ 1.2) may limit its effectiveness in decontamination. Additionally, the study revealed that, under a chemisorption dominated mechanism, the adsorption capacity of activated charcoal follows a consistent pattern with the relative atomic masses of the five metal ions. Conclusions This study systematically evaluates the adsorption of five metal ions by activated charcoal, revealing that adsorption capacity is influenced by pH, ion concentration, and atomic mass, with chemisorption as the dominant mechanism, providing valuable insights for its application in metal ion poisoning treatment.

Functionalized carbon nanotubes for hydrocarbon removal from water

The isosteric heat of adsorption was used to study the interaction between hydrogen molecules and the Multi-Walled Carbon Nanotubes (MWCNTs). Characterizations of the MWCNTs sample were carried out based on the N2 adsorption isotherm at 77 K and the images from TEM and HRTEM. Step by step method was used to volumetrically measure hydrogen adsorption isotherms at equilibrium temperature-pressures from 123-310 K and 0-12.3 MPa. Isosteric heats of adsorption at seven excess adsorption amounts and that at zero surface loading were respectively determined by the slopes of the adsorption isosteres and the plot of the temperature dependence of the Henry’s constants. Results show that the limit of the isosteric heat of adsorption at zero surface loading is about and the mean under the experimental condition is about . The values are in the same grade as those of hydrogen on the activated coconut charcoal but smaller than those of hydrogen on the graphitized carbon black P33, the activated carbon AX-21 and the Single-Walled Carbon Nanotubes (SWCNTs). Conclusions are drawn that relatively lower adsorption amounts and the isosteric heat of hydrogen adsorption on the MWCNTs could be ascribed to the small specific surface area and the large mesopores.

Multi-walled carbon nanotubes (MWCNTs) modified by concentrated sulfuric acid/nitric acid (H2SO4/HNO3) and silane coupling agent (γ-aminopropyltriethoxy silane, KH550) was studied by Fourier transform infrared spectrometry (FTIR), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effect of modified MWCNTs on crystallization behaviour and mechanical properties of low density polyethylene (LDPE)/polyolefin elastomer (POE)/MWCNTs composites were investigated. The results revealed that the crystallinity of composites increased with the addition of the raw MWCNTs and MWCNTs which were modified by H2SO4/HNO3 and KH550. The MWCNTs treated by H2SO4/HNO3 had a better dispersion in matrix than raw MWCNTs and it was beneficial to tensile strength. Further modification by KH550 on H2SO4/HNO3 treated MWCNTs could improve the dispersion of MWCNTs in matrix and interfacial adhesion between MWCNTs and matrix, leading to the tensile strength increased by 35.5 % compared to LDPE/POE composite with raw MWCNTs, and modulus at 100% of composites also increased.

Study of thallium(III) adsorption onto multiwall carbon nanotubes

Study of thallium (III) adsorption onto multiwall carbon nanotubes

ADSORPTION OF CHLOROPHENOL BY ACTIVATED CARBON FROM MIXTURES OF LONG FLAME COAL AND SECONDARY COKING PRODUCTS © V.А. Кucherenko, Doctor of Chemical Sciences, Ju.V. Таmarkina, PhD in Chemical Sciences, V.А. Sabierova, PhD in Chemical Sciences, I.B. Frolova, PhD in Chemical Sciences (L.M. Litvinenko Institute of Physical-Organic and Coal Chemistry of the National Academy of Sciences of Ukraine, 02160, Kyiv, Kharkiv Highway St., 50, Ukraine) The purpose of this work is to evaluate the effect of secondary coking products (SCPs) on the adsorption properties of activated carbons (ACs) from mixtures of SCP and long-flame coal D. AC samples with specific surface area SBET = 885–1173 m2/g were prepared from coal D and mixtures of coal (85 %) and SCP (15 %). Fuses (F), acid tar (AT) of the sulfate department, polymers (P) of the benzene department, cube residue (CR) and coal tar (T) were used, and the corresponding samples are designated as AC(D), AC(F), AC(AT), AC(P), AC(CR), AC(T). The adsorption capacity for 4-chlorophenol (CP) (ACP) was determined at the AC content of 1 g/L (25°C) and the CP initial concentration СCP(0) ≤ 600 mg/L. The CP concentration was determined from the solution optical density at 280 nm (Perkin-Elmer Lambda 20 spectrophotometer). The specific adsorption capacity АCP(S) (mg/m2) was determined by the ratio АCP(S) = ACP/SBET, which is proportional to the concentration of adsorption centers on the AC surface. The degree of CP extraction and the degree of surface coverage were calculated. The CP adsorption kinetics were approximated by pseudo-first order, pseudo-second order and intraparticle diffusion models. The adsorption isotherms were approximated by the Langmuir and Freundlich models. The SCP type was established to have a significant effect on the AC adsorption activity which is expressed by significant differences in the values of adsorption capacity, kinetic characteristics, and isotherm parameters. The CP adsorption kinetics was found to obey the pseudo-second order model (determination coefficient R2 ≥ 0.996) with constants varying from 2,78·10-4 g/mg·min to 6,29·10-4 g/mg·min depending on the SCP type. By comparing the calculations of the kinetics by the pseudo-first order and intraparticle diffusion models, the rate-determining stage was found to be the physical sorption and chemisorption of СP. In the range of equilibrium concentrations of СCP(е) ≤ 350 mg/l, the adsorption isotherms were approximated by the Langmuir model (R2 ≥ 0,994) better than by the Freundlich model (R2 ≥ 0,887). The calculated capacitances of the monolayer for the obtained ACs differ by a factor of ~2 and are in the interval of АCP(L) =214,3 – 414,3 mg/g, Langmuir constants are from 1,89·10-2 l/mg to 5,29·10-2 l/mg. The CP adsorption capacity was found to increase almost linearly with increasing SBET (R2 = 0.931), but the AC(AT) sample sharply drops out of this dependence and shows a 2-fold lower capacity value, which is due to the AT composition. It is determined that the CP capacity and degree of extraction increase in the series of АC(AT) < АC(D) < АC(F) < АC(T) < АC(P) < АC(CR). Judging by the effect on the AC properties, the most effective SCP is the cube residue, which maximally contributes to the formation of adsorption centers being active in relation to CP. The AC(CR) sample exhibits the highest adsorption capacity (414 mg/g), specific capacity (0.353 mg/m2), surface coverage (80.6 %), and initial CP uptake rate. During the first 5 min, AC(CR) absorbs 35.8 % of the CP total amount at CCP(0) = 600 mg/l. The values of this parameter for other samples are lower and range from 11.5 % (AC(AT)) to 29.2 % (AC(P)). Namely SPS composition is concluded to determine the set of chemical reactions forming the AC spatial framework. All SPCs (except acid tar) promote the formation of AC with a higher capacity and an increased adsorption rate, which makes their use promising for improving the ACs adsorption characteristics. Key words: long flame coal, secondary coking product, activated carbon, adsorption, 4- chlorophenol Corresponding author: Таmarkina Ju.V., e-mail: Tamarkina@nas.gov.ua

The sorption behavior of saponin onto clay, paddy, silty loam and sandy soil was thoroughly evaluated in this study. The adsorption kinetic, isotherm and thermodynamic were conducted in batch analysis. Pseudo-first order, pseudo-second order and Elovich kinetic models were applied to evaluate the kinetics of the adsorption. Based on the models, the adsorption of saponin onto soils were mostly governed by physisorption while chemisorption also plays a role in the adsorption process in clay and paddy soil. Mechanism of adsorption was determined by adopting the intraparticle diffusion and Boyd models. The two models concluded that intraparticle diffusion is not the rate-limiting step in saponin uptake in all four soil types. Equilibrium isotherm was evaluated by using Langmuir, Freundlich and Dubinin-Radushkevich isotherm models. The data obeys both Langmuir and Freundlich model, however, Langmuir model tends to overestimate the qe value of the given soil. Clay soil showed highest maximum adsorption, followed by paddy, silty loam and sandy soil. Effects of temperature variation is minimal while variation in pH value was significant where optimum adsorption was achieved at near-neutral pH range. The thermodynamic study showed that the adsorption process was exothermic and spontaneous.

In this work, the single species and competitive (multispecies) adsorption of pyridine, phenol, and p-nitrophenol present in aqueous solution on multiwalled carbon nanotubes (MWCNTs), and nitrogen-doped carbon nanotubes (CNx) were studied. The physicochemical properties of MWCNTs and CNx were related to their capability for the adsorption of the organic molecules. Adsorption isotherms were developed at 25 °C, at pH 7 and 10. All compounds were favorably adsorbed on both materials, with differences in the adsorption capacities. The CNx phenol adsorption capacity outperformed that of MWCNTs; however, CNx demonstrated a lower adsorption capacity for pyridine and p-nitrophenol than MWCNTs. The adsorption capacities for each material could be associated with the particular adsorption mechanisms that control the adsorption of the organic molecules. Based on the results, it is proposed that three mechanisms might be responsible for the adsorption of the organic molecules: hydrogen bonding, π-π interactions, and electron-donor reactions. The prevalence of any of the specific mechanism depends on the geometry of the carbon nanotubes, the size and shape of the organic target molecules to adsorb, and the presence of other organic molecules in solution. The aqueous chemistry of the adsorbates at the solution pH during adsorption, played a relevant role during adsorption as well. The differences in nanotube selectivity were attributed to the presence of oxygen and nitrogen in the adsorbent structure.

This study used multi-walled carbon nanotubes (MWCNTs) to remove humic acids (HA) in water. Experimental results showed the adsorption data fit pseudo-second order model well. The adsorption capacity of CNTs increased with increasing initial concentration of HA until reaching a stable capacity at 80 mgl-1 of HA. The capacity also increased with decreasing pH values in solution. Statistical paired T test showed the adsorption capacity at 40°C was significantly larger than those at 10°C and 25°C. The adsorption capacities after 24 h contact time at 10, 25, and 40°C were 58.6, 60.5, and 84.7 mgg-1, respectively. Three common sorption isotherm models, including the Langmuir, Freundlich, and DubininRadushkevich (D-R) models, were employed to fit the isotherm data. Results showed the theoretical saturation capacity (Qmax) in the Langmuir model increased with increasing temperature and the capacity constant (Kf) in the Freundlich model also increased with increasing temperature. The intensity constants (n) implied HA is favorably adsorbed onto CNTs. The maximum HA adsorption capacity (qmax) in the D-R model increased with increasing temperature. All the three models suggested the adsorption process is endothermic. The extremely low values (0.4-0.5 kJ mol-1) of mean sorption energies (E) calculated from the D-R model suggested the adsorption of HA by MWCNTs is physical nature.

The surfactant, sodium dodecylbenzenesulfonate (NaDDBS) and coupling agents, γ-aminopropyltriethoxy sliane (KH550) and isopropyl dioleic(dioctylphosphate) titanate (NDZ101) were used to treat multiwalled carbon nanotubes in this work. The effects of surface modification of multiwalled carbon nanotubes on crystallization behavior, mechanical properties, and electrical properties of low density polyethylene/polyolefin elastomer/multiwalled carbon nanotubes composites were studied. The results showed that NaDDBS, KH550, and NDZ101 had a favorable effect of improving the dispersion of multiwalled carbon nanotubes, but it cannot improve the interfacial interactionbetween multiwalled carbon nanotubes and the matrix. The improvement in dispersion favored the crystallization behavior and mechanical properties. Modified multiwalled carbon nanotubes had a better acceleration nucleation effect than raw multiwalled carbon nanotubes on low density polyethylene/polyolefin elastomer blends at low content (≤1 wt%). The tensile strength of low density polyethylene/polyolefin elastomer/multiwalled carbon nanotubes composites with modified multiwalled carbon nanotubes increased with lower multiwalled carbon nanotubes content (≤1 wt%), and KH550 and NDZ101 led low density polyethylene/polyolefin elastomer/multiwalled carbon nanotubes composites to possess a higher tensile strength than that of NaDDBS with 1 wt% content. NaDDBS, KH550, and NDZ101 had a minor influence on the dielectric properties of the composites and even caused a decrease in the dielectric loss of composites with 10 wt% multiwalled carbon nanotubes content.