Academic Editor: Joseph J. Received 20 Nov Revised 04 Jan Accepted 04 Jan Published 04 Mar Abstract In this study two solid supports, silica and florisil, were impregnated with crown ether dibenzocrown-6 and Fe III ions and their efficiency was compared in the adsorption process of As V from aqueous solutions. Introduction It is known that groundwater contains different contaminants.
Materials and Methods 2. Impregnation of the Solid Supports Silica and florisil were impregnated with crown ether dibenzocrown-6 and Fe III ions using the dry method. Results and Discussion 3. Table 1. Figure 1. Figure 2. IR vibrational spectrum of studied adsorbents material. Figure 3. Figure 4. Figure 5. Influence of the contact time on the adsorption capacity of the impregnated silica a and on the impregnated florisil b. Table 2.
Kinetic parameters for As V adsorption onto studied material. Figure 6. Pseudo-first-order kinetic plots for silica a and florisil b at the adsorption of As V. Figure 7. Pseudo-second-order kinetic plots for silica a and florisil b at the adsorption of As V.
Figure 8. Arrhenius plot of As V adsorption onto impregnated silica and florisil. Table 3. Figure 9. Temperature effect on the adsorption of As V onto impregnated silica and florisil. Figure Adsorption isotherm of As V onto impregnated silica and florisil. Langmuir isotherm for As V adsorption on impregnated silica and florisil. Freundlich isotherm for As V adsorption on impregnated silica and florisil. Table 4. Parameters of Langmuir and Freundlich isotherms for the adsorption of As V onto impregnated silica and florisil.
References D. Bakker, G. Amy, and J. Mukherjee, M. Sengupta, M. Hossain et al. View at: Google Scholar C. Iesan, C. Capat, F. Ruta, and I. Makavipour and R. Hao, M. Han, C. Wang, and X. Fan, T. Sun, H. Xu, Y. Yang, Q. In case of silica samples, the isotherms are characteristic for isotherms of type IV and a H1 hysteresis loop.
Type IV isotherms occur on porous adsorbents possessing pores in the radius range of approximately 15— angstroms A. The slope increase at higher elevated pressures indicates an increased uptake of adsorbate as the pores are being filled. Type H1 hysteresis loops are typical for adsorbents with well-defined structures and narrow pore size distributions.
This type of isotherms presents a hysteresis loop which is specific for mesoporous materials which present a capillary condensation. The increase in the N 2 adsorbed volume is higher in the region of 0. The macropores volume of silica materials is very limited as shown by the plateau achieved for N 2 adsorption isotherms at relative pressure between 0.
The samples with florisil present a type IV isotherm and a H3 hysteresis loop. Type H3 loops are usually given by aggregates of plate-like particles or adsorbents containing slit-shaped pores [ 7 , 21 — 25 ]. Table 1 summarizes the physical characteristics of the materials after impregnation and it can be noticed that the impregnated silica presents a higher surface area and porosity than the florisil sample. For this reason, it is expected that the impregnated silica will develop a higher adsorption capacity in the removal process of As V from aqueous solutions.
The florisil and silica impregnated with crown ether and Fe III ions were subjected to the FTIR analysis in order to prove that the impregnation occurred. It is more obvious in case of the silica adsorbent. In case of silica, the impregnation process obviously suggests a higher quantity of crown ether and Fe III ions than in case of florisil. Therefore, the FTIR analysis suggests also that the impregnated silica is possible to develop a higher adsorption capacity. The surface morphology and the EDX quantification of the obtained material are presented in Figure 3.
The spherical shape of the micron sized silica particle presents a higher aggregation following surface treatment. Also it can be observed that the coating process with Fe III ions is inside the pore in case of silica rather than homogenous coating like in the case of florisil. Figure 4 presents the dependence of the adsorption capacity on the removal of As V from aqueous solutions for impregnated silica and florisil versus the S : L ratio. Influence of the S : L ratio on the removal of As V from aqueous solutions for impregnated silica and florisil.
Increasing the amount of impregnated silica used for removing As V from aqueous solutions leads to decreasing of the adsorption capacity because the adsorption capacity is in relation to the amount of adsorbent used. In the same time, the removal degree of As V from aqueous solution is not influenced by the amount of impregnated silica used in the adsorption process. In contrast to silica, the adsorption capacity for florisil remains almost constant for the S : L ratio used, but the As V removal degree increases with the increasing of the S : L ratio.
In order to obtain both higher adsorption capacity and higher removal degree, the optimal S : L ratio used for future experiments is 0. For the kinetic studies, the influences of the contact time on the adsorption capacity of the impregnated silica and florisil were studied Figure 5. The data showed that the adsorption capacity for both materials increases with increase of time till they reach the equilibrium at minutes.
The increase of the adsorption capacity with the time increasing in case of silica is very obvious; in case of florisil, this increase is not significant. The adsorption capacity of both of the studied materials increases with the temperature increasing indicating an endothermic nature of As V adsorption process. Influence of the contact time on the adsorption capacity of the impregnated silica a and on the impregnated florisil b.
The experimental data were fitted with the pseudo-first-order Figure 6 and the pseudo-second-order Figure 7 kinetic models. The following equation defines the two kinetic models:. The values of constants, together with the regression coefficients R 2 obtained in all the cases, are summarized in Table 2. Pseudo-first-order kinetic plots for silica a and florisil b at the adsorption of As V.
Pseudo-second-order kinetic plots for silica a and florisil b at the adsorption of As V. The low correlation coefficients obtained for the pseudo-first-order kinetic model for impregnated silica and florisil as well as the difference between the experimental and the calculated adsorption coefficient show that it is not appropriate to fit the experimental data with this kinetic model.
The values obtained for the pseudo-second-order kinetic model fit better the experimental data and represent the adsorption process of As V onto impregnated silica and florisil. Comparing the values for silica and florisil, it can be concluded that the adsorption process of As V on silica went much better than that on florisil.
To calculate the activation energy of the adsorption of As V on impregnated silica and florisil, the Arrhenius equation was used with the rate constant from the pseudo-second-order kinetic model:. The activation energy calculated was These values suggest that the adsorption of As V onto impregnated silica is a chemical sorption in comparison to the adsorption process onto impregnated florisil that is a physisorption.
These conclusions suggest also that the impregnated silica could develop a higher maximum adsorption capacity than the impregnated florisil in the removal process of As V from aqueous solutions.
The thermodynamic studies were made to illustrate whether the adsorption process is a spontaneous process or not. Therefore, the equilibrium constant K c is defined as follows [ 31 ]:. Temperature effect on the adsorption of As V onto impregnated silica and florisil. In case of impregnated florisil, the adsorption process is spontaneous only at higher temperature.
The adsorption process of As V removal by impregnated silica and florisil is presented in Figure The adsorption capacity increases with the increase of the equilibrium concentration of As V onto the impregnated materials till it approaches a constant value at the highest equilibrium concentration.
It can be noticed that the impregnated silica develops much higher adsorption capacity in the removal process of As V from aqueous solutions than the impregnated florisil.
These results are in accordance with the conclusions raised from the characterization of the obtained materials and the conclusion raised from the activation energy.
To describe the equilibrium nature of the As V adsorption process onto impregnated silica and florisil, the Langmuir and Freundlich isotherm models were used.
Table 4 presents the parameters of Langmuir and Freundlich isotherms for the adsorption of As V onto impregnated silica and florisil. Parameters of Langmuir and Freundlich isotherms for the adsorption of As V onto impregnated silica and florisil. Comparing the regression coefficient of the two isotherms, the Freundlich isotherm has a lower value than the Langmuir isotherm for both used materials.
This suggests that the Langmuir model was more favorable, including the fact that a low difference between the q m ,exp and q m ,calc was observed. The Langmuir model describes an adsorption over a homogeneous surface and that all adsorption sites are energetically equivalent and do not affect the adsorption of molecules on an adjacent site [ 6 , 33 ].
The present study showed that the adsorption efficiency of silica and florisil in the removal process of As V from aqueous solutions was increased by impregnation of the solid support with crown ether and loaded with Fe III ions. The kinetic studies revealed that the adsorption process of As V onto the studied materials followed the pseudo-second-order kinetic model.
The equilibrium data were fitted with Langmuir and Freundlich isotherm, the best correlation being obtained by the Langmuir one. The characterization analysis together with As V adsorption tests suggested that the impregnation process in case of silica solid support was more obvious than in case of florisil which leads to an excellent adsorption performance of As V when the silica solid support was used.
The use of silica impregnated with crown ether and Fe III as adsorbent, in the removal process of As V from aqoueous solutions, represents an efficient method, because a good efficiency and selectivity of As V removal from aqueous solutions containing trace concentration is obtained. The authors declare that there is no conflict of interests regarding the publication of this paper.
Read article at publisher's site DOI : Materials Basel , 14 13 , 02 Jul Int J Mol Sci , 20 7 , 31 Mar To arrive at the top five similar articles we use a word-weighted algorithm to compare words from the Title and Abstract of each citation. Molecules , 18 10 , 16 Oct Int J Mol Sci , 22 19 , 03 Oct Home Chromatography Gas Chromatography. Florisil Discussions about GC and other "gas phase" separation techniques.
Does anyone use this and why? Most of my samples would be essential oils or essential oils in hexane. Florisil cleanup and fractionation helps to confirm the ID of a compound if using a fractionation step, but is normally used to eliminate interferences from the matrix.
ECDs are prone to both positive interferences, from other electronegative compounds in the same retention window, and negative interferences from signal supression caused by hydrocarbons.
Heavy oils will also cause retention time shifts that may make confirmation of identity difficult. Getting rid of matrix interferences will make for a much happier analyst! The cartridge type are quick, easy and inexpensive. In contrast to silica, the adsorption observed that the coating process with Fe III ions is inside capacity for lorisil remains almost constant for the S : L the pore in case of silica rather than homogenous coating like ratio used, but the As V removal degree increases with the in the case of lorisil.
In order to obtain both higher studied solid supports were impregnated with crown ether adsorption capacity and higher removal degree, the optimal and loaded with Fe III ions.
S : L ratio used for future experiments is 0. As V Adsorption 3. Kinetic Studies. Comparing the values for silica and lorisil, it can be aqueous solutions for impregnated silica and lorisil. To calculate the activation energy of the adsorption impregnated silica and lorisil were studied Figure 5. If the equilibrium constant changing with the temper- 3. Figure 9: Temperature efect on the adsorption of As V onto impregnated silica and lorisil.
In case 3. Equilibrium Studies. Table 3: hermodynamic parameters. To describe the equilibrium nature of the As V adsorp- Figure Freundlich isotherm for As V adsorption on impreg- tion process onto impregnated silica and lorisil, the Lang- nated silica and lorisil. Hao, M. Han, C. Wang, and X. Conclusions [6] H.
Fan, T. Sun, H. Xu, Y. Yang, Q. Tang, and Y. Glocheux, A. Albadarin, J. Negrea, M. Ciopec, L. Lupa et al. Alexandratos, C. Stine, R. Sachleben, and B. Duman and E. Also is achieved a residual concentration of As V under the [11] P. Mohapatra, D.
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