Sulfur Nanoparticles Synthesis and Characterization from H2S Gas, Using Novel Biodegradable Iron Chelates in Aqueous Sur
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1103-MM01-03
Sulfur Nanoparticles Synthesis and Characterization from H2S gas, using Novel Biodegradable Iron Chelates in Aqueous Surfactant systems Aniruddha Subhash Deshpande1, Ramdas B. Khomane1, Bhalchandra K. Vaidya1, Renuka M. Joshi1, Arti S. Harle2, and Bhaskar D. Kulkarni1 1 Chemical Engineering and Process Development Division, National Chemical Labrotary, Dr. Homi Bhabha Road, Pashan, Pune, 411008, India 2 Center for Material Characterization Division, National Chemical Labrotary, Dr. Homi Bhabha Road, Pashan, Pune, 411008, India ABSTRACT Sulfur nanoparticles were synthesized by catalytic oxidation of hazardous H2S gas using novel biodegradable iron chelates in aqueous surfactant systems at ambient conditions of temperature, pressure and neutral pH. Fe3+-malic acid chelate (0.05M aqueous solution) was studied in different aqueous surfactant systems (e.g. CTAB 0.01M, SDS 0.1M, Tween-80 (Polyoxyethylene 20 sorbitan monoleate) 0.01M). The structural features of sulfur nanoparticles have been characterized by XRD, TEM, DLS, EDS. TEM analysis shows that the morphology of sulfur nanoparticles synthesized in aqueous surfactant systems of CTAB, Tween-80 and SDS showing nearly uniform in size (average particle size 7nm, 12nm, 15nm respectively) and DLS analysis shows the monodispersity of the synthesized nanoparticles. Moreover, sulfur nanoparticles synthesized in aqueous surfactant systems exhibit higher antimicrobial activity (against bacteria, yeast and fungi) than that of sulfur synthesized in only aqueous phase. INTRODUCTION Sulfur finds extensive technological applications [1-5]. Sulfur nanostructures are also used modification of carbon nanostructures [6,7], in synthesis of sulfur nanowires with carbon to form hybrid materials with useful properties for gas sensor and catalytic applications [8], Metal-sulfur compounds like ZnS, CdS, which play important role in nonlinear optical and electroluminescent devices respectively. Recently, Guo et al. [9] reported the synthesis of monoclinic sulfur nanoparticles using the mixture of two reverse microemulsion systems. The catalytic conversion of H2S gas to elemental sulfur can be achieved by various chemical [10-13] and biological [14, 15] means. Nagal [16] has reported the gas desulfurization based on liquid redox chemistry, as follows
↔HS L → S ↓ + 2H ↑ + 2Fe
H2S(g) + H2O(l) H2S(l) + 2Fe3+
(1)
2 (l)
n-
(l)
0
+
2+
Ln-(l)
(2)
Where ‘L’ denotes an organic ligand, which are usually a polyaminocarboxyllic acid [17] and ‘n’ denotes the charge on the organic ligand. Since the active ferric chelate is converted to inactive ferrous chelate, the later component has to be regenerated by oxidation according to the reactions
½ O2 (g) + H2O (l)
↔½O
(3)
2 (l)
2 Fe2+ Ln- (l) + ½ O2 (l) + H2O (l)
→ 2 Fe
3+
Ln- (l) + OH –
(4)
At present, use of iron chelates has been extensively commercialized in Lo-CAT, Sulferox process, [18]. However, these chelating agents [e.g. EDTA, DTPA, CDTA, etc.] have very low rate of biodegradation and therefore cause environmental
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