Potential theory of adsorption was used for description of adsorption isotherms of n-butane on microporous active carbon. It was shown that characteristic curve of adsorption can be treated as specific form of thermal equation of adsorption giving the possibility to calculate and predict both equilibrium and thermodynamic characteristics of adsorption in wide range of temperature and relative pressure. The results can be used for the design of adsorption systems and for predicting adsorption equilibrium behavior of binary and/or multicomponent gaseous mixtures on active carbon under wide range of conditions, without time consuming and expensive experimental determination.
This paper presents the feasibility for the removal of methyl orange (MO) dye from aqueous solution using an activated carbon prepared from Prosopis juliflora bark. Batch adsorption experiments were carried out as a function of pH, contact time, adsorbate concentration, adsorbent dosage and temperature. The commonly applicable isotherms namely Freundlich and Langmuir equations are used for the prediction of isotherm parameters. A comparison of linear least-square method and a trial-and-error non-linear method are examined in Freundlich and Langmuir (Four forms) isotherms. The nature of adsorption isotherm feasibility was evaluated with dimensionless separation factors (RL). The dynamics of adsorption process was analyzed with Lagergren’s Pseudo-first order and Pseudo-second order kinetic equations. Thermodynamic parameters like the change in enthalpy (ΔHo), change in entropy (ΔSo) and change in Gibbs free energy (ΔGo) were evaluated and ΔGo shows a negative value whereas ΔHo shows the positive value indicating that the adsorption process was spontaneous and endothermic in nature. The functional group characterization of the adsorbent was done using Fourier transform infrared spectroscopy (FTIR). The thermal stability of activated carbon was analyzed using Thermo gravimetric analysis (TGA) and Differential thermal analysis (DTA).
This paper presents the feasibility of the removal of hexavalent chromium ions from aqueous solutions by using activated carbon prepared from Cajanus Cajan(L) Milsp. It was carbonized and activated by treating it with concentrated sulfuric acid followed by heating for 5 h at 500°C. Batch adsorption experiments were carried out as a function of pH, contact time, initial concentration of the adsorbate, adsorbent dosage and temperature. The experimental data fitted well to the Freundlich isotherm. The thermodynamic parameters such as ΔH°, ΔS°, and ΔG° were calculated, which indicated that the adsorption was spontaneous and endothermic in nature. The adsorbent used in this study was characterized by FT-IR and SEM before and after the adsorption of metal ions. The results indicate that Cajanus Cajan(L) Milsp can be employed as a low cost alternative and commercial adsorbents in the removal of chromium (VI) from water and waste water.
A pseudo-second order rate equation describing the kinetics of the adsorption of 1,2-dichloropropane from aqueous solution onto the activated carbon at different initial concentrations, adsorbent dose, temperature, particle diameter and the rate of stirring have been developed. The rate constant was calculated. The rate constant correlation in a good mixing conditions was described as a function of the temperature.
The results of the studies of bis(1-chloro-2-propyl) ether adsorption from aqueous solution onto AG5 activated carbon were presented here. Dynamic adsorptivity, mass transfer zone and the velocity of the adsorption front of the 10cm adsorption bed depth for the velocity of flow 9 and 25 cm/min were determined. For the regeneration of the adsorption bed, acetone rinsing was used. Total washout of adsorbed bis(1-chloro-2-propyl) ether from the bed was obtained. After the regeneration the adsorbent has not shown deterioration of adsorption properties. To isolate bis(1-chloro-2-propyl) ether from acetone, distillation was used.
In this study dependences of the adsorption equilibrium of 1,2-dichloropropane in aqueous solution for six activated carbons (A, AG, AG5, DTO, WD-ekstra, CWZ-22) and four polymeric adsorbents (XE-563, XE-572, XE-340, XE-348) were presented. All the adsorption isotherms onto activated carbons were described by the Freundlich equation. To analyze the isotherms on the polymeric adsorbents the Langmuir-Freundlich equation was used. It was found that in the low range of the concentrations the adsorptive properties of the activated carbons are reduced in the following direction DTO>WD-ekstra>CWZ-22>AG>A>AG5. Reducing the adsorptive properties of the polymeric adsorbents states was carried out in the following order: XE-340> XE-572>XE-563>XE-348. The adsorbents XE-340, XE-572 and XE-563 have much more higher adsorptive properties than the applied activated carbons. Lower adsorptive properties of XE-348 are the result of its high surface polarity.
Microporous carbon molecular sieves of extremely narrow pore size distribution were obtained by carbonization of a novel raw material (Salix viminalis). The precursor is inexpensive and widely accessible. The pore capacity and specific surface area are upgradable by H3PO4 treatment without significant change of narrowed PSD. The dominating pore size indicates that these molecular sieves are a potential competitor to other nanoporous materials such as opened and purified carbon nanotubes.
Adsorption experiments of nitric oxide in nitrogen carrier gas were held on activated carbon in a fixed bed flow system. Breakthrough curves describing the dependence of exit concentrations of nitric oxide on time were matched with theoretical response curves calculated from the linear driving force model (LDF). The model assumes Langmuir adsorption isotherm for the description of non-linear equilibrium and overall mass transfer coefficient for mass transfer mechanism. Overall mass transfer coefficients were obtained by the method of least squares for fitting numerically modelled breakthrough curves with experimental breakthrough curves. It was found that LDF model fits all the breakthrough curves and it is a useful tool for modelling purposes.
We carried out fixed-bed column adsorption of metanil yellow from simulated wastewater on NATPAAC derived from oil palm fruit mesocarpfibre so as to determine the adsorption capacity, qe, of the carbon under the effects of inlet concentration, Co, carbon bed height, H and dye solution flow rate, Q. Our results indicate that the optimum qe was 15.982 mg/g by Co 25 mg/L, H 4.1cm and Q 8 mL/min. In the study, qe was observed to decrease with increase in Co and Q. The optimum bed height was 4.1cm. Our experimental data were modelled by applying Thomas and Yoon-Nelson kinetic models. Correlation coefficient, R2 values (generally above 0.85) show that the two kinetic approaches provide an effective model of the experimental data. We conclude that oil palm fruit mesocarpfibre has potential as a precursor for production of carbon for acid-dye removal from wastewater.
Activated carbons from biomass material of giant knotweed Reynoutria sachalinensis (F. Schmidt ex Maxim.) Nakai were obtained. Use of this plant for manufacturing activated carbon has not been studied yet. Therefore, the first activated carbons of giant knotweed origin are described. Both physicochemical (by steam and CO2) and chemical (by KOH) activation methods were applied. Influences of temperature (500, 600, 700 and 800°C), burn-off [10, 25 and 50 wt. % (daf)] and KOH concentration on pores surface area and volume distribution of the obtained activated carbons were explored. Porosity of the elaborated sorbents was determined by benzene and carbon dioxide sorption measurements. Sorbents obtained by steam activation were micro- and mesoporous with surface area and volume of pores increasing with temperature and burn-off to V = 0.351 cm3 g-1 and S = 768 m2 g-1 at 800°C at 50% burn-off. Carbon dioxide activation resulted with notably microporous activated carbons with porous texture parameters also increasing with burn-off to V = 0.286 cm3 g-1 and S = 724 m2 g-1 at 50% burn-off. The highest BET surface area of 2541 m2 g-1 was achieved when chemical (KOH) activation was performed using KOH to char ratio 4:1.
Adsorptive removal of 2-, 3- and 4-chlorophenol from aqueous solutions by granular activated carbon was studied. The influence of different experimental parameters like initial concentration, carbon dosage and pH on the adsorption of monochlorophenols were evaluated. The influence of type of acid and base used for water acidification or alkalization was also tested. The results indicate that acidic pH is favorable for the adsorption of chlorophenols; however the type of acid or alkali used for the change of pH has a little influence and did not significantly affect the adsorption efficiency. The pH played an important role in the adsorption kinetics of chlorophenols at pH values above the pKa values of the compounds, while little influence on adsorption rate was observed if pH was decreased below the pKa values
PL
Zbadano absorpcję 2-, 3- i 4-chlorofenolu z wody na granulowanym węglu aktywnym. Sprawdzono wpływ różnych parametrów na adsorpcję, takich jak stężenie początkowe adsorbatów, ilość węgla aktywnego czy pH roztworu, jak również wpływ rodzaju kwasu i zasady użytych do zakwaszenia lub alkalizacji środowiska. Uzyskane rezultaty pokazują, że adsorpcja chlorofenoli zachodzi o wiele lepiej w kwaśnym środowisku, natomiast rodzaj zastosowanego kwasu lub zasady do zmiany pH nie wpływa znacząco na efektywność adsorpcji. pH odgrywa natomiast istotną rolę w przypadku kinetyki adsorpcji chlorofenoli na węglu aktywnym zwłaszcza w pH powyżej wartości ich pKa, natomiast w środowisku o pH poniżej wartości pKa chlorofenoli wpływ ten jest znikomy
Removing organic substances from wastewater is a complex problem. Different methods are used for this purpose. Recently, much attention has been given to the application of sorption and advanced oxidation processes (AOPs), which contribute also to the regeneration of activated carbon. The analysis presented in this paper focused on determining the influence of Cu(II) and Fe(II) ions adsorbed on activated carbon on the efficiency of oxidation of phenol by means of H2O2, Fenton's reagent Fe2+/H2O2 and 1:1 HNO3 solution exposed to 2450 MHz microwaves, and, accordingly, the influence of Cu(II) and Fe(II) ions on the sorptive capacity of regenerated activated carbons. The results show that the chemical regeneration of activated carbon using AOPs resulted in partial oxidation of the adsorbed organic substance. The presence of Cu(II) or Fe(II) ions increased the regeneration efficiency. Using nitric acid to oxidize adsorbed phenol brought about a dramatic decline in the sorptive capacity of activated carbon with respect to this substance and an increase in the sorptive capacity of carbon with respect to metal ions. A serious drawback of this method, however, is that the oxidation of adsorbed phenol caused a significant loss of mass of activated carbon regardless of the oxidizing agent used.
PL
Usuwanie zanieczyszczeń organicznych ze ścieków jest złożonym problemem wymagającym stosowania różnych metod. Coraz częściej rozważa się możliwość wykorzystania do tego celu procesu sorpcji i metod pogłębionego utleniania (AOPs), co jednocześnie skutkuje regeneracją węgla aktywnego. W prezentowanej pracy prowadzono badania wpływu zaadsorbowanych na węglu aktywnym jonów Cu(II) i Fe(II) na skuteczność utleniania fenolu z wykorzystaniem H2O2, reakcji Fentona Fe2+/H2O2 oraz roztworu 1:1 HNO3 w obecności mikrofal 2450 MHz, a tym samym wpływu na zdolność sorpcyjną zregenerowanych węgli aktywnych. Wykazano, że chemiczna regeneracja węgla aktywnego z wykorzystaniem metod AOP skutkuje częściowym utlenieniem zaadsorbowanej substancji organicznej. Obecność jonów Cu(II) lub Fe(II) zwiększa skuteczność regeneracji. Wykorzystanie kwasu azotowego do utleniania zaadsorbowanego fenolu skutkuje drastycznym obniżeniem zdolności sorpcyjnych węgla aktywnego względem tej substancji i wzrostem zdolności sorpcyjnych względem jonów metali. Niestety negatywnym skutkiem procesu utleniania zaadsorbowanego fenolu, niezależnie od zastosowanego czynnika utleniającego, jest znaczący ubytek masy węgla aktywnego.
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