Sulfur Nanoparticles Synthesis and Characterization from H2S Gas, Using Novel Biodegradable Iron Chelates in W/O Microemulsion

Sulfur nanoparticles were synthesized from hazardous H2S gas using novel biodegradable iron chelates in w/o microemulsion system. Fe3+–malic acid chelate (0.05 M aqueous solution) was studied in w/o microemulsion containing cyclohexane, Triton X-100 andn-hexanol as oil phase, surfactant, co-surfactant, respectively, for catalytic oxidation of H2S gas at ambient conditions of temperature, pressure, and neutral pH. The structural features of sulfur nanoparticles have been characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), energy dispersive spectroscopy (EDS), diffused reflectance infra-red Fourier transform technique, and BET surface area measurements. XRD analysis indicates the presence of α-sulfur. TEM analysis shows that the morphology of sulfur nanoparticles synthesized in w/o microemulsion system is nearly uniform in size (average particle size 10 nm) and narrow particle size distribution (in range of 5–15 nm) as compared to that in aqueous surfactant systems. The EDS analysis indicated high purity of sulfur (>99%). Moreover, sulfur nanoparticles synthesized in w/o microemulsion system exhibit higher antimicrobial activity (against bacteria, yeast, and fungi) than that of colloidal sulfur

Absorption of hydrogen sulfide into aqueous solutions of ferric nitrilotriacetic acid: local auto-catalytic effects

The rates of reactive absorption of H2S into aqueous solutions of ferric nitrilotriacetic acid, at T=303 K and pH=4.5, studied in a flat-interface stirred cell, appear to be auto-catalyzed by freshly precipitated sulfur particles. These auto-catalytic effects, which are more prominent at higher ferric chelate concentration, seem to involve particle-to-interface adhesion phenomena. A model based on Higbie's penetration theory, which incorporates particle-to-interface adhesion, as well as a growing particle coverage during a liquid element's contact time at the interface, is used to analyze the experimental data. This model gives a reasonable description of the local auto-catalytic effects on the gas absorption rate.© Elsevie

OXIDATIVE ABSORPTION OF HYDROGEN-SULFIDE BY A SOLUTION OF FERRIC NITRILOTRIACETIC ACID COMPLEX IN A COCURRENT DOWN FLOW COLUMN PACKED WITH SMV-4 STATIC MIXERS

The reactive absorption of hydrogen sulfide into a solution of the ferric chelate of nitrilotriacetic acid (NTA) was studied at 13 degrees C in a cocurrent down flow column packed with stainless steel Sulzer SMV-4 static mixers. The concentration of ferric chelate varied from 200 to 30 mol/m(3); the pH ranged from 8.3 to 6.7. Volumetric liquid-phase mass transfer coefficients for H2S (k(L) alpha) could be measured and were correlated by k(L) alpha = 0.0572E(L)(0.55) for 0.060 less than or equal to U-L less than or equal to 0.156 [m/s], 0.59 less than or equal to U-G less than or equal to 2.95 [m/s], and 1.4 x 10(2) less than or equal to E(L) less than or equal to 3 X 10(3) [N/m(2)s], in which E(L) is the liquid energy dissipation factor and U-L and U-G are the superficial liquid and gas velocity, respectively. The k(L) alpha values observed with H2S under reactive conditions appeared to be approximately a factor of 4 higher than those observed for oxygen absorption in the same liquid over the same packing. The cause of the extra volumetric mass transfer obtained with H2S under similar conditions is not well understood yet. The reaction kinetics of hydrogen sulfide with the ferric chelate of NTA was found to be first order in both ferric NTA and H2S for 0.40 <p(A) <0.8 kPa, 0 <C-Fe(III) <200 mol/m(3), and 6.7 <pH <8.2