Hoi nghi Khoa hoc ky niem 35 ndm Vien Khoa hoc vd Cong nghe Viet Nam - Hd Noi 10.2010<br />
<br />
<br />
PHAN UNG QUANG OXY HOA DI THE HQfP CHAT SUNFUA XUC<br />
TAC BOI A 1 ( I I I ) - T E T R A S U L F O P H T H A L 6 C Y A N I N E TREN S'xOj<br />
<br />
Le Thanh Minh'. Phan Thanh Thao', Phan Minh Tan^<br />
'institute of Chemical Technology<br />
^Department of Science and Technology of Hochiminh City<br />
Email: minhlethanh2002(^yahoo.com<br />
Tom tat:<br />
Nghien cieu dieu che vd tinh chdt ciia phuc Al(III)-tetrasulfophthalocyanine cd<br />
dinh tren chdt mang silica bien tinh da duac md td. Nhieng tinh chdt ciia vdt lieu<br />
mdi ndy duac xdc dinh bdi cdc ky thuat phdn tich nhiet (TGA), phdn xg khuyech<br />
tdn (DRS) vd BET. Phdn icng oxy hda hap chdt sunfua trong dung dich nude bdng<br />
oxy xuc tdc bdi vdt lieu ndy duac thuc hien. Kd qud cho thdy vdt lieu cd khd ndng<br />
xuc tdc tdt cho phdn ung oxy hda sunfua khi duac chieu sdng bdi dnh sdng khd<br />
kiin. Phdn tich sdc ky ion cho thdy sdn phdm ciia qud trinh oxy hda sunfua bao<br />
gdm cdc ion sunfat, sunfit vd thiosunfat.<br />
Abstract:<br />
The preparation and properties of a phthalocyanine-silica, where the<br />
phthalocyanine is covalently bonded to an inorganic netM'ork, are described. The<br />
properties of this new material were determined by TGA, UV-VIS, BET technique.<br />
Oxidation of inorganic sulfide in water by molecular oxygen was studied under<br />
visible light irradiation in the presence of immobilized Al(III)-<br />
tetrasulfophthalocyanine (AlTSPc) on silica gel. The hybrid catalyst exhibited a<br />
good capacity for uptake of sulfide ions from water. Ionic chromatography<br />
analysis showed that sulfite, thiosulfate and sulfate were the reaction products.<br />
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85<br />
Tieu ban: Moi tru&ng vd Ndng luang ISBN: 978-604-913-013-7<br />
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1. INTRODUCTION<br />
The photocatalytic properties of metallophthalocyanine (MPcs) are of interest in recent<br />
decades. Under the illumination of visible light, MPcs have proved to be highly promising as<br />
photosensizers due to their intense absorption in the red region of visible light. High triplet<br />
state quantum yields and long-lifetimes are required for efficient sensitization and these<br />
criteria may be fulfilled by the incorporation of a diamagnetic metal such as zinc, aluminum,<br />
silicon into the pbthalocyanine compounds [1]. Aluminum tetrasulfophthalocyanine (AlTSPc)<br />
complexes have attracted a great deal of interest because of their appreciably long triplet<br />
lifetime. This is a great advantage since the number of diffusional encounters between the<br />
triplet excited state of AlTSPc and ground state molecular oxygen increase. The result of that<br />
is singlet oxygen as a strong oxidative agent produced.<br />
Water soluble complexes of AlTSPc display a high photo-catalyst under visible light<br />
irradiation. The immobilization of pbthalocyanine by covalent bonding to catalytically inert<br />
surfaces, such as silica gel, is a prospective approach to achieve heterogeneous catalysts<br />
exhibiting well-defined dispersions of the active component. The aim of this paper is to study<br />
the preparation of AlTSPc complexes supported on silica gel carrier and use as catalyst in the<br />
oxidation of the sulfide anion.<br />
2. EXPERIMENTAL<br />
2.1 Materials and methods<br />
- AlTSPc was synthesized in Institute of Chemical Technology as literature [6].<br />
- Na2S.9H20, SOCI2, Zn(CH3COO)2, dimethylformamide (DMF) N,N-dimethyl-p-<br />
phenylendiamin.2HCl, 3-aminopropyltriethoxysilane, xylene were purchased from Merck.<br />
C2H5OH, (NH4)2HP04, FeCl3, toluene, ether were purchased from Shanghai Chemicals.<br />
Si02 (60-200 Mesh-Merck) was dried in vacuum (100 mmHg) at 200°C for 4 hours.<br />
- The UV-VIS diffuse reflection absorption spectra of solid catalysts were recorded on a<br />
UV-VIS Spectrometer V530 (Shimadzu). The BET surface area and pore size distributions<br />
of the materials were determined by nitrogen adsorption at 77K, with a NOVA 2200<br />
instrument. Elemental analysis for carbon, hydrogen, nitrogen and sulfur was done by<br />
Element Analyzer YEAl 12. Thermal gravimetric analysis measurements were made in air<br />
with a heating rate of lO^C min"', from 25 to 1000 °C by DTG-60 (Shimadzu). Light<br />
intensity was measured with a silicon photodiode (Voltcraft MS-1300). The pH of reaction<br />
was controlled by pH meter (pH controller 500-Hanna).<br />
- Sulfide concentration was measured by photometric method on DR/2000 equipment<br />
(Hach). This method was based on photometric color measurement of methylene blue<br />
compound produced from the reacfion of sulfide, N,N-dimethyl-p-phenylenediamine.2HCl<br />
and FeCl3 at a wavelength of 750nm [8].<br />
- Degree of loading of the Si02 surfaces by the covalently bonded AlTSPc was indirectly<br />
determined by measuring the content of aluminum analyzed by AAS method After The sample<br />
was treated with H2SO4 (98%)/H202 andfiirthertreated with UV for 90 minute at 90°C.<br />
2.2 Preparation of Al-phthalocyanine-tetrachlorosulfonyl (AIPC-SO2CI): A suspension of<br />
AlTSPc (0.25g, 0.3mmol) in SOCI2 (10ml) was refluxed in a 250ml flask under an<br />
atmosphere of dry nitrogen. After 12 hours, excess SOCI2 was removed by distillafion. Dried<br />
toluene (20ml) was added and removed through distillation. This operation was repeated three<br />
times to eliminate the last traces of SOCI2. Then the solid was washed three times with ether<br />
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86<br />
Hoi nghi Khoa hoc ky niem 35 ndm Vien Khoa hoc vd Cong nghe Viet Nam - Hd Noi 10/2010<br />
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and dried at 80"C for 10 hours. AIPCSO2CI was obtained as a dark blue powder (0.22g, 80%).<br />
IR (KBr, cm"'): 1626 (VC=N), 1320 (VC-N), 1187 (vas(s=0)), 1023 (vs(s=o)), 837 (VCH aromatic), 743<br />
(vcH aromatic), 692 (vso). Electronic absorption (DMF, X^ax, nm): 685; 616; 362.<br />
2.3 Immobilization AlPcS02Cl on modified Si02: Immobilization AIPCSO2CI on modified<br />
Si02 was carried out through two steps: Surface modification of Si02 and Immobilization<br />
AIPCSO2CI on modified Si02<br />
- Surface modification of Si02 (Si02-NH2): The silica species was fimctionalized with 3-<br />
aminopropyl groups on the surface as follows: Si02 (5g), dried xylene (40 ml) and 3-<br />
aminopropyltriethoxysilane (2.5 g, 11 mmol) were charged in a 250ml three necked flask<br />
equipped with a magnetic stirrer, reflux condenser and thermometer. The mixture was refluxed<br />
for 24b. The product was filtered and washed thoroughly with acetone. The solid was dried<br />
under vacuum at 80°C for lOh. Modified Si02 was obtained as a light yellow power (4.8 g).<br />
- Immobilization AIPCSO2CI on modified-Si02 (AlTSPc-Si02): A suspension of AIPCSO2CI (0.1 g,<br />
0.12mmol) and modified silica gel (2g) in pyridine (10ml) were charged in a 250ml three necked<br />
flask and heated to reflux under an atmosphere of dry nitrogen for 24b. The mixture was filtered<br />
and the solid obtained was washed with water, DMF and ether by tum. Then the solid was dried<br />
in vacuum at 80°C for 12h. AlTSPc-Si02 was obtained as a green power.<br />
2.4 Catalytic oxidation of sulfide anion:<br />
The photochemical reaction was carried out in a Pyrex glass made reactor thermostated at<br />
32°C. The irradiafion source was halogen lamp (125W-220V) with the light intensity of<br />
250mW/cm^. The aqueous suspension containing catalysts (22nmol AlTSPc) and 500ml of<br />
Na2S solution (lOOppm) in an aerated aqueous medium was stirred by magnic stining. At<br />
certain intervals of irradiation, the small aliquots of suspension were withdrawn, filtered and<br />
measured the concentration of sulfide. The pH was adjusted by HCl 0.05M or NaOH 0.05M<br />
solution. For investigating the autooxidation of sulfide in the presence of oxygen, no catalyst<br />
was employed as the following above.<br />
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3. RESULTS AND DISSCUSION<br />
3.1 Covalent linkage of complexes onto supports and characterization of the hybrid<br />
materials<br />
Textural characteristics of Si02 and Si02-NH2 are listed in Table 1. A decrease of specific<br />
surface area and average pore diameter as well as a decrease of the mesoporous volume upon<br />
modification indicate a successful covalent linkage of organic groups to the silica surface.<br />
Furthermore, the values of the BET parameter (CBET) decrease from starting Si02 to modified<br />
Si02, suggesting a decrease in the average polarity of the surface as a result of the grafting of<br />
organic functionalities [9].<br />
The supported catalysts have also been characterized by a dynamic method of nitrogen<br />
physical adsorption. Nitrogen adsorption isotherm analysis indicated that materials retained<br />
their mesoporous morphology after grafting of phtbalocyanines. The surface areas and<br />
mesoporous volumes lightly decreased after anchoring of pbthalocyanine molecules. The<br />
higher values of BET parameter of AlTSPc-Si02 as comparing to those of Si02-NH2 (Table.<br />
1) suggests an increase in the average polarity of the surface as a result of the grafting of<br />
phtbalocyanines containing polar substituents on the periphery of the molecules [9].<br />
Tieu ban: Moi truong vd Ndng luong ISBN: 978-604-913-013-7<br />
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Table 1: Texture parameters of the supports<br />
<br />
TGA<br />
Surface Volume Pore<br />
Materials area of pores diamete CBET<br />
Temp* Loss Mass Temp Loss Mass<br />
(m'/g) (cm^/g) r(A)<br />
CQ (%) CQ (%)<br />
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Si02 514.27 0.858 87.28 95.80 - - - -<br />
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Si02-NH2 304.42 0.589 72.97 42.39
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