Synthesis and Characterization of Zeolite Y Encapsulated Metal Complexes and Surfactant Modified Zeolite Y for Removal of Pollutants
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Date
2016-05
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Addis Ababa Universty
Abstract
In this study heterogeneous catalysts were synthesized based on the encapsulation of
iron(III), nickel(II) and copper(II) with complexes of N,N′-ethylenebis(salicylimine),
mixed ligands of 2,2'-bipyridine and 1,10-phenanthroline and N,N′-disalicylidene-1,2-
phenylenediamine ligands into zeolite Y supercage using ship-in-a-bottle method of
synthesis. The catalysts were characterized by X-ray powder diffraction, BET surface
area and pore volumes, Fourier transform infrared spectroscopy, electron paramagnetic
resonance, thermo-gravimetric and elemental analysis. Computational studies based on
Density functional theory (DFT) calculation are carried out on both neat complexes as
well as metal complexes encapsulated into zeolite Y to investigate changes in structural
parameters like bond length, bond angle and dihedral angle, energies of the highest
occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO),
global hardness and softness value of the metal complexes upon encapsulation into
zeolite.
The results obtained from the physico-chemical analytical techniques showed that
iron(III), nickel(II) and copper(II) complexes of N,N′-ethylenebis(salicylimine), mixed ligand of 2,2'-bipyridine and 1,10-phenanthroline and N,N′-disalicylidene-1,2-
phenylenediamine ligands were successfully formed into zeolite Y supercage without
affecting zeolite structure and properties of the metal complexes. Moreover, Density
functional theory (DFT) calculations predicted that zeolite encapsulated metal complexes
has higher reactivity compared to respective metal complexes.
The catalysts prepared were found to be very effective in the removal of organic
pollutants (i.e. azo dye, 2-phenyl phenol (OPP) and 4-chloro-3-methyl phenol (PCMC))
from synthetic wastewater. Interactive effects of four factors; initial hydrogen peroxide
(H2O2) concentration, catalyst dosage, temperature and pH on the degradation of selected
organic pollutants were determined. Experimental results showed that lower pH and
higher temperature were optimal for complete removal of organic pollutants using the
prepared catalysts. Moreover, increase in the concentration of hydrogen peroxide (H2O2)
and catalyst dosage, beyond the optimum concentration had a negative effect attributed to
the formation of hydroperoxyl radical (•OOH). This has a lower oxidation potential than
the hydroxyl radical (•OH) and aggregation of catalysts, respectively. The extent of
reusability for the catalytic oxidation of organic pollutants and the possible deactivation
mechanism after successive reuse of each catalyst were studied. The possible
intermediate product, degradation pathway and kinetic studies for oxidation of organic
pollutants were also studied.
Besides ion exchange zeolite have adsorption properties due to its large surface area and
net negative charge. In this study the negative charge and hydrophilic surface properties
of neat zeolite were modified by haxadecyltrimethyl ammonium bromide (HDTMA-Br) surfactant to adsorb both inorganic and organic pollutants simultaneously. The surfactant
modification effect on the surface of zeolite was characterized using X-ray powder
diffraction, FT-IR spectroscopy, scanning electron microscopy, BET surface area and
pore volume, thermo gravimetric analysis, zeta potential and hydrophobicity
measurements. The results of physico-chemical analytical techniques showed that
a bilayer of surfactant-modified zeolite was successfully formed on the external surface
of the zeolite. The surfactant-modified zeolite was investigated for the adsorption of acid
blue dye and Cr(VI) in synthetic wastewater. The effects of adsorbent dosage, pH,
temperature, time and initial pollutant concentrations were investigated in batch
adsorption experiments. The correlation coefficient and the normalized standard
deviation value showed that the experimental isotherm data fitted well to Langmuir and
Freundlich isotherm models for acid blue dye and Cr(VI), respectively. The kinetic
process is well described by pseudo second order kinetic model. The prepared catalyst
and the surfactant modified zeolite showed good catalytic and adsorption capacities for
removal of organic and inorganic pollutants from real tannery wastewater
Description
Keywords
Encapsulated Metal Complexes and Surfactant Modified Zeolite Y