In this study, crude multi‐walled carbon nanotubes (MWCNT) was functionalized by a two‐step process; first using strong mixed acids (H2SO4/HNO3) and then treatment with 1,3‐phenylenediamine (mPDA). The equilibrium adsorption of CO2 on pristine MWCNT and amine functionalized MWCNT (MWCNT‐NH2) were investigated. Experiments were preformed via application of volumetric method in a dual sorption vessel at temperature range of 298–318 K and pressures up to 40 bars. The results obtained indicated that the equilibrium uptake of CO2 increased after functionalizing of MWCNT. The increase in CO2 capture by MWCNT‐NH2 was attributed to the existence of great affinity between CO2 molecules and amine sites on this adsorbent at low pressures. The experimental data were analyzed by means of Freundlich and Langmuir adsorption isotherm models. The data obtained revealed a fast kinetics for the adsorption of CO2 in which most of adsorption occurred at initial period of adsorption experiments. This renders MWCNT as a suitable adsorbent for practical applications. Values of isosteric heat of adsorption were evaluated based on Clausius–Clapeyron equation. The results demonstrated that both chemisorption and physisorption played important role in CO2 adsorption on MWCNT‐NH2, whereas the physisorption process was dominant for CO2 adsorption on MWCNT.
12In the present study, multicomponent competitive biosorption of heavy metal from aqueous 13 solution onto pretreated dried Aspergillus niger in batch system was investigated. The 14 adsorption data were fitted to the multicomponent Langmuir, Freundlich, Temkin and Sips 15 equations. We used the genetic algorithm of biosorption in ternary mixture to evaluate the 16 potential effects of each metal in the removal of other metals. In order to take both 17 mechanisms of the cell-surface binding and intra-particle diffusion into account, an 18 alternative model was investigated by combining the pseudo-second-order kinetics model and 19 the intra-particle diffusion model. A model describing the process of biosorption by a single-20 stage batch design was developed and verified based on the Temkin isotherm model. 21 Fundamentally, the outlook from these observations of the experiments that the pretreated 22 dried biomass is a suitable absorbent for the removal of significant amounts of the heavy 23 metal from the effluents of industrial wastewater is promising.24 25
Matérial Institut Lavoisier (MIL)-101, one of
the metal–organic
frameworks containing numerous coordinatively unsaturated sites, as
well as high specific surface area, was synthetized under different
protocols for CO2 adsorption and separation from N2. To improve its CO2 adsorption capacity, different
amounts [10, 25, and 40 wt % of tetraethylenepentamine (TEPA)] were
grafted to the parental MIL-101. Results revealed that TEPA-MIL-101
(40 wt %) showed one of the highest CO2 adsorption capacities
(i.e., 3.76 mmol g–1 at 298 K at 1 bar) among existing
MIL-101 and its modified moieties. This amount was 1.56 times greater
than parental MIL-101 (in spite of having superior textural properties),
which adsorbed 2.41 mmol g–1 CO2 at the
same operational conditions. This can be attributed to the presence
of polar functional groups in the porous structure of MIL-101 that
enhance the interaction between CO2 active sites on the
adsorbent surface. Isosteric heat of adsorption of CO2 and
N2 on TEPA-MIL-101 (40 wt %) were 35 and 18 kJ mol–1, respectively, based on the temperature-dependent
form of the Freundlich model in the Clausius–Clapeyron equation.
Ideal adsorption solution theory (IAST) was used for determination
of CO2/N2 selectivity for a binary gas mixture,
including 15% CO2 and 85% N2 at 298 K and at
1 bar. TEPA-MIL-101 (40 wt %) showed an exceptional CO2/N2 selectivity of 220. Adsorption kinetics study demonstrated
that the Avrami model was the best model for fitting the experimental
data, which denotes that more than one pathway exists in CO2 and N2 adsorption.
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