A study of carbon dioxide sequestration has been performed in aqueous electric arc furnace (EAF) and ladle furnace (LF) slag suspensions, in leached hydrated-matrixes, and in leachates to estimate ...their intrinsic sequestration potential at ambient conditions (temperature of 20 ± 1 °C and atmospheric pressure). The CO2 sequestration was tested in aqueous suspensions of steel slags at a liquid-to-solid ratio of 10 kg/kg as well as in leached hydrated-matrixes and leachates isolated from these fresh slag suspensions after three consecutive leachings. The sequestration assays were performed at 20 °C with a flow rate of 5 mL/min of a CO2 concentration of 15.00 vol %. The results have revealed that the CO2 sequestration capacity of the LF slag suspension (24.7 g of CO2/100 g of slag) is 14 times superior to that of the EAF slag suspension. This greater CO2 sequestration capacity of the LF slag suspension may be associated in large part to its higher content of portlandite, which reacts with CO2 relative to the EAF slag suspension. Moreover, the separation of hydrated-matrixes and leachates significantly enhanced the CO2 sequestration capacity of EAF slag while a slight decrease was observed for the LF slags. This may be due to an obstruction of the CO2 binding sites of LF slag hydrated-matrixes following the accumulation of calcium carbonate. Taken together, these results suggest that EAF and LF slags could be used for the CO2 sequestration and given a good yield as well in aqueous suspension as in separated matrixes and leachates.
A study of carbon dioxide (CO2) absorption/desorption has been carried out to estimate the influence of the structural features of distinct amines on their CO2 absorption and regeneration. The ...absorption has been made at two different CO2 flow rates with a series of aqueous 5 wt % ammonia, monoethanolamine (MEA), triethanolamine (TEA), triethylamine, pyridine, pyrrolidine, 2-(2-aminoethylamino)ethanol (AEE), and N-(2-aminoethyl)-1,3-propanediamine (AEPDNH2) solutions, while the CO2 desorption has been performed by heating these solutions. The presence of two or three amino groups in AEE and AEPDNH2, the structure of tertiary amine and alkanolamine, and a nonaromatic ring of pyrrolidine might favor the CO2 absorption, while the structural features of ammonia and pyridine seem to be unfavorable. The tertiary alkanolamine is the most easy to regenerate and looses less of its CO2 loading after regeneration. It appears that AEE and AEPDNH2 would represent interesting compounds which could be used as CO2 absorbents in industrial technologies to prevent CO2 release into the atmosphere.
We report the advances in the principal structural and experimental factors that might influence the carbon dioxide (CO
2
) adsorption on natural and synthetic zeolites. The CO
2
adsorption is ...principally govern by the inclusion of exchangeable cations (countercations) within the cavities of zeolites, which induce basicity and an electric field, two key parameters for CO
2
adsorption. More specifically, these two parameters vary with diverse factors including the nature, distribution and number of exchangeable cations. The structure of framework also determines CO
2
adsorption on zeolites by influencing the basicity and electric field in their cavities. In fact, the basicity and electric field usually vary inversely with the Si/Al ratio. Furthermore, the CO
2
adsorption might be limited by the size of pores within zeolites and by the carbonates formation during the CO
2
chemisorption. The polarity of molecules adsorbed on zeolites represents a very important factor that influences their interaction with the electric field. The adsorbates that have the most great quadrupole moment such as the CO
2
, might interact strongly with the electric field of zeolites and this favors their adsorption. The pressure, temperature and presence of water seem to be the most important experimental conditions that influence the adsorption of CO
2
. The CO
2
adsorption increases with the gas phase pressure and decreases with the rise of temperature. The presence of water significantly decreases adsorption capacity of cationic zeolites by decreasing strength and heterogeneity of the electric field and by favoring the formation of bicarbonates. The optimization of the zeolites structural characteristics and the experimental conditions might enhance substantially their CO
2
adsorption capacity and thereby might give rise to the excellent adsorbents that may be used to capturing the industrial emissions of CO
2
.
A study of carbon dioxide (CO2) and sulfur dioxide (SO2)/CO2 mixtures absorption has been carried out in aqueous 2-(2-aminoethylamino)ethanol (AEE) solution and its blends with N-methyldiethanolamine ...(MDEA) and triethanolamine (TEA) to estimate the influence of SO2, MDEA, and TEA on the CO2 absorption capacity of the AEE. The CO2 absorption loading has been estimated in 15 wt % AEE alone and in the presence of either 5 and 10 wt % MDEA or 5 and 10 wt % TEA solutions with 100 vol % CO2 and 5.03 and 15.02 vol % SO2/CO2 mixtures at a starting temperature of 296 K and flow rates of 3.067, 3.229, and 3.605 L/min, respectively. The results revealed that the presence of SO2 in the gas decreases the CO2 absorption rate and loading in the AEE solution as a function of the concentration of SO2. The additions of 5 and 10 wt % of MDEA and TEA do not seem to influence the CO2 absorption rate in the AEE solution. Moreover, the addition of MDEA increases slightly the CO2 absorption capacity of AEE, while TEA decreases the absorption capacity of AEE in the absence and presence of SO2. These effects were enhanced with increases of MDEA and TEA. Altogether, the results indicated that the blend of 15 wt % AEE + 10 wt % MDEA represents an interesting solvent which could be used as absorbent for the removal of CO2 from emission into the atmosphere by industries.
A study of inclusion complexation of liquid non-ionic surfactants, nonylphenol (NP) and nonylphenol 9 mole ethoxylate (NP9EO), with β-cyclodextrin (β-CD), was carried out by mass spectrometry, ...surface tension, and ultraviolet–visible (UV-VIS) and Fourier transform infrared (FTIR) spectroscopies. The inclusion complexation was effectuated by heating at 80
°C and filtration of aqueous NP
+
β-CD and NP9EO
+
β-CD suspensions. The mass spectrometry and surface tension measurements revealed that NP and NP9EO form inclusion complexes with β-CD and β-CD possesses a higher affinity for NP. These results are supported by the data from UV-VIS spectroscopic analyses that have indicated that a three times greater amount of NP is entrapped into β-CD than NP9EO. This phenomenon has been associated with the smaller size and a higher degree of hydrophobicity of NP that favours its entrapment into β-CD as compared to that of NP9EO. At the structural level, the data from FTIR spectroscopic study have indicated that alkyl chains of NP and NP9EO can form van der Waals interactions with the cavity of β-CD. Moreover, NP and NP9EO seem to cause a reorganization of the intramolecular hydrogen bonds and change of the hydration of β-CD, but did not appear to strongly interact with C–C, C–O–C, and OH groups of β-CD. Together these results suggest that the formation of inclusion complexes by NP and NP9EO with β-CD molecules could constitute an effective and advantageous technique to remove liquid non-ionic surfactants from wastewater due to the non-toxic character of β-CD to humans and the environment.
An analysis of carbonation was carried out with the aqueous fresh red mud suspension at a liquid-to-solid ratio of 10 kg/kg, as well as in the leached-hydrated matrixes and leachates isolated from ...this red mud suspension after three successive leachings, to evaluate their intrinsic carbonation potential at ambient conditions (temperature of 20 ± 1 °C and atmospheric pressure). The carbonation assays were performed at 20 °C using a CO2 concentration of 15.00 vol% at a flow rate of 5 mL/min. The red mud matrix has a great leaching capacity of Na−(hydr)oxide, which is the principal hydroxide that seems to be implicated in the carbonation of leachates that have half-carbonation capacity of red mud. Moreover, the carbonation of the red mud suspension also involves a portlandite-containing matrix. The carbonation of the red mud suspension and leachates implicates a complete neutralization of their content in Ca− and Na−(hydr)oxides. Although the leached hydrated-matrixes seem to be partially carbonated, it preserves a carbonation capacity near to that of leachate after three successive leachings. Moreover, three leached hydrated-matrixes and leachates have a carbonation capacity (7.09 g of CO2/100 g of red mud) higher than the carbonation capacity obtained for the red mud suspension, which is evaluated to 4.15 g of CO2/100 g of red mud. Taken together, these results suggest that the carbonation of the red mud may be enhanced by the use of leached hydrated-matrixes and leachates obtained from multiple leaching.
A study was carried out by ultraviolet-visible (UV-vis) and Fourier transform infrared (FTIR) spectroscopies to establish the efficiency of adsorption of fluoxetine hydrochloride (FLU), onto a ...crosslinked β-cyclodextrin-carboxymethylcellulose (β-CD-CMC) polymer. The adsorption was performed in mixtures containing aqueous FLU solution at 20 mg/L and 0.01-0.30 g of the β-CD-CMC polymer, at 25 °C, and atmospheric pressure under stirring. The results have revealed that the adsorption is a rapid process and the polymer possesses a high affinity for FLU with an adsorption capacity of 5.076 mg of FLU/g of polymer. This adsorption may involve the formation of a stable inclusion compound β-CD-CMC/FLU through the penetration of the FLU aromatic ring (A and/or B) into the β-CD cavity, and a physical adsorption with the polymer network. The inclusion compound can be stabilized by the formation of H-bonds between the -CF(3) group of FLU and the 6'-OH group of β-CD, and van der Waals interactions between the FLU aromatic ring and β-CD cavity. The data from a kinetic study have also indicated that the adsorption process was well described by the pseudo-second-order kinetic model, in which the initial adsorption rate and constant were estimated at 1.938 mg/g min and 0.075 g/mg min, respectively. Moreover, the results of adsorption equilibrium fitted the Freundlich isotherm, indicating a multilayer coverage and heterogeneous surface. Together, these results suggest that the adsorption of FLU onto the crosslinked β-CD-CMC polymer could constitute an advantageous technology for removing this commonly used antidepressant drug from wastewater due to the high adsorption capacity of the polymer and non-toxic character of β-CD to humans and environment.
A study of adsorption/recovery of nonylphenol 9 mole ethoxylate (NP9EO) on a crosslinked beta-cyclodextrin-carboxymethylcellulose (beta-CD-CMC) polymer was carried out by ultraviolet-visible (UV-vis) ...and Fourier transform infrared (FTIR) spectroscopies. The adsorption was performed in mixtures containing 500 mg of the beta-CD-CMC polymer and aqueous NP9EO solutions at concentrations 12-82 mg/L, whereas the recovery of NP9EO was effectuated by shaking the beta-CD-CMC polymer loaded with methanol. The assays were made at 25 degrees C and atmospheric pressure under agitation. The results have shown that the adsorption is a rapid process and the beta-CD-CMC polymer exhibits a high NP9EO adsorption capacity of 83-92 w% (1.1-6.8 mg NP9EO/g beta-CD-CMC polymer) dependent of the initial NP9EO concentration in liquid phase. This adsorption may involve the formation of an inclusion complex beta-CD-NP9EO and a physical adsorption in the polymer network. The adsorption equilibrium measurements, which were analyzed using the Langmuir isotherm, have indicated a monolayer coverage and the homogeneous distribution of active sites at the surface of the beta-CD-CMC polymer. Moreover, the negative value obtained for the free energy change (-13.2 kJ/mol) has indicated that the adsorption process is spontaneous. In parallel, the beta-CD-CMC polymer exhibited a high NP9EO recovery efficiency of 97 w% that may occur through a decrease of binding strength between beta-CD-CMC polymer and NP9EO. Together, these results suggest that the beta-CD-CMC polymer could constitute a good adsorbent for removing nonylphenol ethoxylates from wastewater due to its high adsorption capacity and non-toxic character of beta-CD and CMC to environment.
This review presents a summary of the main interactions that occur during the carbon dioxide (CO
2) adsorption at the surface of steel slags with basic (CaO, MgO), amphoteric (Al
2O
3, Cr
2O
3, TiO
...2, MnO, iron oxides) and acidic (SiO
2) oxides. The high content of metal oxides in steel slags gives them a great potential to adsorb CO
2, reaching a saturation value of about 0.25
kg of CO
2/kg of slag. CO
2 is physisorbed and chemisorbed on the most of metal oxide types. Generally, the CO
2 physisorption on the basic and amphoteric metal oxides involves an electrostatic interaction between the CO
2 and the cation from the oxides while the CO
2 chemisorption rather implicates the basic sites that acts as the electron donor, and which are associated with O
2− ions localized at surface defects. These interactions result in the formation of carbonates (monodentates or unidentates and bidentates). The affinity of oxides for the CO
2 and the carbonate formation principally depend of the strength and number of basic sites at their surface and varies as following: basic oxides
>
amphoteric oxides
>
acidic oxides. The basic metal oxides generally represent the best electron donors and thus the best CO
2 adsorbents due to the high basicity and their great number of reaction sites. Hence, it appears that the surface structure of basic and amphoteric metal oxides which may favour their interaction with the CO
2, as well as their basicity is the determinant factor contributing to the formation of carbonate species. The molecular analysis of CO
2 adsorption on steel slag metal oxides will provide useful data to identify rate-controlling mechanisms and should be considered for the development of new effective methods for the capture of atmospheric CO
2 emissions released from industries.
We report the advances in the principal structural and experimental factors that might influence the carbon dioxide (CO2) adsorption on natural and synthetic zeolites. The CO2 adsorption is ...principally govern by the inclusion of exchangeable cations (countercations) within the cavities of zeolites, which induce basicity and an electric field, two key parameters for CO2 adsorption. More specifically, these two parameters vary with diverse factors including the nature, distribution and number of exchangeable cations. The structure of framework also determines CO2 adsorption on zeolites by influencing the basicity and electric field in their cavities. In fact, the basicity and electric field usually vary inversely with the Si/Al ratio. Furthermore, the CO2 adsorption might be limited by the size of pores within zeolites and by the carbonates formation during the CO2 chemisorption. The polarity of molecules adsorbed on zeolites represents a very important factor that influences their interaction with the electric field. The adsorbates that have the most great quadrupole moment such as the CO2, might interact strongly with the electric field of zeolites and this favors their adsorption. The pressure, temperature and presence of water seem to be the most important experimental conditions that influence the adsorption of CO2. The CO2 adsorption increases with the gas phase pressure and decreases with the rise of temperature. The presence of water significantly decreases adsorption capacity of cationic zeolites by decreasing strength and heterogeneity of the electric field and by favoring the formation of bicarbonates. The optimization of the zeolites structural characteristics and the experimental conditions might enhance substantially their CO2 adsorption capacity and thereby might give rise to the excellent adsorbents that may be used to capturing the industrial emissions of CO2.
PDF
