Faculty of Science, Najran University, Saudi Arabia
Received Date: March 03, 2017; Accepted Date: March 30, 2017; Published Date: Apriil 07, 2017
Citation: El-Mehbad N (2017) Recovery of Phase Transferee Catalysts from Waste-water by Adsorption on Zeolite. J Pet Environ Biotechnol 7:320. doi: 10.4172/2157-7463.1000320
Copyright: © 2017 El-Mehbad N. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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The interaction between zeolite and phase transfer catalysts PTC (cationic surfactants) is of great interest. In this paper, study the influence of various physical and chemical parameters. On the adsorption of PTC on zeolite is compared according their efficiency on removal PTC at constant conditions. The optimum conditions are studied to removal PTC. Thermodynamic of adsorption are calculated to suggest the mechanism of adsorption. The effects of different conditions are studied to investigate degree of removal PTC. Furthermore, the effect of hydrophilic and hydrophobic of PTC on efficiency of adsorption on zeolite is discussed according to thermodynamic adsorption parameters. A dsorption isotherm is studied according Frumkin isotherm. The mechanism of adsorption suggested with respect micellization processes and adsorption at solution/air interface. Furthermore, cross sectional area of phase transfer catalyst affect on degree of its adsorption. The results confirm the effect of pH and chemical structures of PTC efficiency of adsorption by zeolite.
The adsorption of phase transfer catalysts and cationic surfactants on solid surfaces is very important. Such adsorption has been studied to elucidate its mechanism and to determine the significant kinetic and thermodynamic parameters which affect it . The performance of phase transfer catalysts at interface depends on the chemical structure of the molecular and their nature . The technique of phase transfer catalysis provides a method which avoids the use of solvent. The literature on chemistry related to phase transfer catalysis has grown rapidly during the last few years [3-5]. The concept of phase transfer catalysis is not limited to anion transfer system, but is much more general, so that in principle one could also transfer cations, free radicals, whole molecule. Although reactions at phase boundaries, particularly those between organic and inorganic reagents. Menger  has reviewed reactions occurring at phase boundaries in the absence of surfactants or phase transfer agents. Reactions occurring at an interface tend to be rate limited by the amount of interfacial area, as well as to the concentration of reactant species at the interface. However, most two phase reactions involving relatively nonpolar organic species do not precede at useful rates in the absence of a catalyst. Micelle-catalyzed reactions are discussed in detailed [7,8]. It is well to point phase transfer agents are not necessary surfactants, but small quaternary salt like tetra ethyl ammonium bromide which studied in this research. This catalyst is easily removed from the final product by diluting the organic phase with ether and washing with water. So, it is very important to treat this water to remove the used catalyst.
Physical adsorption of phase transfer agents at solid solution interface can involve micelle and hemimicelle formation through association between hydrocarbon chains of the adsorbed molecules . For this reason, the interactions between zeolite and cationicagents are very important. In this paper, the existing data on physical adsorption of cationic agents is studied using zeolite and compare with barite mineral. The measured surface adsorptions have been compared with surface tension measurements and adsorption density by zeolite.
This paper prepares tetra-ethyl-ammonium-bromide (PTC) and confirmed its structure by NMR, IR, and mass spectroscopy. Also study various physical chemical parameters on the adsorption of tetra-ethylammonium- bromide catalysis on zeolite and solution air interface.
Tetra-ethyl-amine was refluxed with bromo-ethane in pure ethyl alcohol ate 35°C. The resulting was recrystalised and purified according Omar et al. with purity about 98.6% . Surface tension was measured using a Du Nouy tensiometer (Kruss type-8451) for various concentrations of the synthesized phase transfer catalysis. Before each measurement, the glass plate was washed by immersion in hot chromic acid followed by washing with doubly distilled water. The accuracy of the surface tension in most cases was about. 0.2 mN/m.
Synthetic zeolite was used as adsorbent . The maximum of the particle size was about 9 um, and BET surface about 2.5 m2/g was determined elsewhere . Determination of the amount adsorbed by determination the concentration of the cationic phase transfer catalysis (PTC) before and after the adsorption by phase titration .
1-Structure confirmation of tetra-ethyl-ammonium bromide
FTIR spectrum of the catalysis showed the absorption bands 750 cm-1 (CH2)n,, 1086 cm (c-n), 1290 CH3 symmetric bending, 1500 CH2 asymmetric bending. FTIR spectrum is shown in Figure 1 and confirmed the functional group.
The HNMR tetra-ethyl-ammonium bromide showed the following bands δ = 3 ppm (N-CH2), δ = 1.5 (CH3) as shown in Figure 2. The Figure 2 confirmed the chemical structure of the synthesized cationic catalysis.
The mass spectrum of the synthesized cationic is more confirmed by mass spectroscopy. The molecular ion peak is at m/z 210 (Figure 3). The surface tension against logarithm of concentration of cationic catalysis is used to determine critical micelle concentration at temperature 30°C. (Figure 4). The maximum surface excess Γmax and minimum surface area Amin were calculated as described elsewhere . These results in Table 1 show large value of surface excess and minimum area, indicating that it adsorbs at solution/air interface. Standard free energies of micellization ΔGmic was calculated according to the following equation:
|Tetra-ethyl-ammonium bromide||Temperature(°C)||(CMC)||A min x 102nm2||Γmaxx 105mol/m2||ΔGmic
Table 1: Surface property of tetra-ethyl-ammonium bromide at 30°C.
ΔGmic = RT ln CMC
The value of ΔGmic is negative, so micellization of the catalysis is spontaneous process. The synthetic solution of tetra-ethylammonium- bromide was prepared and study adsorption of its different concentration. Figure 5 shows the adsorption isotherm cationic catalysis on various concentration of Zeolite at 30°C. This isotherm indicates the adsorption increase slightly and tends to steady stable with different concentration. The author suggests adsorption by ion exchange compatible with Omar et al. . The adsorption of (PTC) can occur at the external surface depends on cross sectional area of its head group approximately 0.45 nm2 and pore area of zeolite.
The adsorption of PTB depends on charge of zeolite surface. Figure 6 shows that, the effect of pH on degree of adsorption PTC. At acidic medium surface of zeolite has positive charge, also cationic catalysis has positive charge. As the results, reduced adsorption of catalysis at higher pH, however, the surface of zeolite acquires negative charge at higher pH. So, the adsorption increases with increase concentration of catalysis. As the results the negatively charged zeolite surface lead to the cationic catalysis adsorbed at its surface forming monolayer. Therefore, the ammonium groups are oriented to the zeolite surface beside adsorption through penetration the pores of zeolite. The value of monolayer is reached at pH 10 forming plateau. Hence, particularly in the pH range from 7-8, the more addition of cationic catalysis via the weaker Vander Waals interactions between the alkyl chains.
The author suggests at pH 8 and at optimum conditions, the cationic catalysis is ionized in water with a positive with its head nitrogen group whereas the zeolite surface has a negative charge, lead to adsorption through vandeer waals force (electros attraction force). In comparison, these results with adsorption of cationic catalysis at solution air interface. The surface excess concentration, Г (mol/m2), and the area per molecule, A (nm2) can be calculated according Rosen. It is clear that, the surface excess concentration increased with increase PTC concentration until CMC (Figure 7). These results confirm the free molecules tend to form micelles and monolayer at CMC. So, the density of adsorption increases until the concentration equal CMC to form monolayer. Furthermore, by increasing the PTC concentrations lead adsorption of another layer with other direction and the surface of zeolite. So, adsorption on zeolite surface is preferable before adsorption of cationic catalysis PTC at solution/air interface. In fact, in the micellar region, the adsorption density not changes because the cationic catalysis tends to form micelle. After CMC, the adsorption density remains stable, so it enhances on degree of adsorption at zeolite surface.
According Frumkin isotherm the result can be analyzed according the following equation:
(1- θ)n exp(-2n θ) = KC
Where the θ is the degree of coverage, a is the lateral interaction coefficient, K is a constant equal to exp (-ΔG0/RT- Ln55.5).
ΔG0 is the standard free energy and c is the equilibrium concentration,
Ln [θ/(1- θ) n] = ln K + 2aθ
Figure 8 shows the isotherm of adsorption isotherm of cationic catalysis. It can calculate the parameters (a) and ΔG°. By put the relation of ln [θ/(1- θ)n] versus θ gives a straight line with a slope equal to 2a and an intercept of ( - ΔG0/RT- ln 55.5) as in Figure 8. I t is found that ΔG° = -26.5 kg/mol, while (a) equal 2.1.
These results confirm that adsorption of cationic catalysis on zeolite takes place though zeolite pores. Otherwise, the remaining molecules adsorbed at zeolite surface depending on the lateral interaction values between cationic molecules. On the other hand, the cationic molecules tend to form hemi- micellization process, and the free molecules migrate from bulk solution to form micelle or adsorb on to zeolite surface by pore penetration or at solid surface. The thermodynamic of physical adsorption of cationic catalysis confirm that free molecules tend to form of hemimicelles, then micelle formation in bulk solution. Hemimicelles are difficult forming at lower pH, so cationic molecule prefers adsorption at zeolite surface rather than adsorption at solution/ air interface.