Kinetics of the Oxidation of Hydrogen Sulfide by Atmospheric Oxygen in an Aqueous Medium

Hydrogen sulfide is an important acid rain precursor and this led us to investigate the kinetics of its oxidation in aqueous phase by atmospheric oxygen. The kinetics was followed by measuring the depletion of oxygen in a reactor. The reaction was studied under pseudo order conditions with [H2S] in excess. The kinetics followed the rate law: -d[O2]/dt = k[S][O2]t (A) Where [S] represents the total concentration of hydrogen sulfide, [O2]t is the concentration of oxygen at time t and k is the second order rate constant. The equilibria (B - C) govern the dissolution of H2S; the sulfide ion in water forms different species: H2S K1 HS- + H+ (B) HS- K2 S2- + H+ (C) Where K1 and K2 are first and second dissociation constants of H2S. Although, H2S is present as undissociated H2S, HS- and S2- ions, nature of [H+ ] dependence of reaction rate required only HS- to be reactive and dominant. The rate law (A) on including [H+ ] dependence became Equation (D). -d[O2]/dt = k1K1[H+ ][S][O2]t / ([H+ ] 2 + K1[H+ ] + K1K2) (D) Our results indicate anthropogenic VOCs such as acetanilide, benzene, ethanol, aniline, toluene, benzamide, o-xylene, m-xylene, p-xylene and anisole to have no significant effect on the reaction rate and any observed small effect is within the uncertainty of the rate measurements

Synthesis of N-doped microporous carbon via chemical activation of polyindole-modified graphene oxide sheets for selective carbon dioxide adsorption

A polyindole-reduced graphene oxide (PIG) hybrid was synthesized by reducing graphene oxide sheets in the presence of polyindole. We have shown PIG as a material for capturing carbon dioxide (CO2). The PIG hybrid was chemically activated at temperatures of 400-800 degrees C, which resulted in nitrogen (N)-doped graphene sheets. The N-doped graphene sheets are microporous with an adsorption pore size of 0.6 nm for CO2 and show a maximum (Brunauer, Emmet and Teller) surface area of 936 m(2) g(-1). The hybrid activated at 600 degrees C (PIG6) possesses a surface area of 534 m(2) g(-1) and a micropore volume of 0.29 cm(3) g(-1). PIG6 shows a maximum CO2 adsorption capacity of 3.0 mmol g(-1) at 25 degrees C and 1 atm. This high CO2 uptake is due to the highly microporous character of the material and its N content. The material retains its original adsorption capacity on recycling even after 10 cycles (within experimental error). PIG6 also shows high adsorption selectivity ratios for CO2 over N-2, CH4 and H-2 of 23, 4 and 85 at 25 degrees C, respectively.close9

Graphene-SnO2 composites for highly efficient photocatalytic degradation of methylene blue under sunlight

Graphene sheets decorated with SnO2 nanoparticles (RGO-SnO2) were prepared via a redox reaction between graphene oxide (GO) and SnCl2. Graphene oxide (GO) was reduced to graphene (RGO) and Sn2+ was oxidized to SnO2 during the redox reaction, leading to a homogeneous distribution of SnO2 nanoparticles on RGO sheets. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show uniform distribution of the nanoparticles on the RGO surface and high-resolution transmission electron microscopy (HRTEM) shows an average particle size of 3-5 nm. The RGO-SnO2 composite showed an enhanced photocatalytic degradation activity for the organic dye methylene blue under sunlight compared to bare SnO2 nanoparticles. This result leads us to believe that the RGO-SnO2 composite could be used in catalytic photodegradation of other organic dyes. S Online supplementary data available from stacks. iop.org/Nano/23/355705/mmediaX11124110sciescopu

Environmental applications using graphene composites: water remediation and gas adsorption

This review deals with wide-ranging environmental studies of graphene-based materials on the adsorption of hazardous materials and photocatalytic degradation of pollutants for water remediation and the physisorption, chemisorption, reactive adsorption, and separation for gas storage. The environmental and biological toxicity of graphene, which is an important issue if graphene composites are to be applied in environmental remediation, is also addressed.open11245243sciescopu

Reversible CO2 adsorption by an activated nitrogen doped graphene/polyaniline material

For effective adsorption of carbon dioxide (CO2), we investigate a porous N functionalized graphene adsorbent produced by the chemical activation of a reduced graphene oxide/polyaniline composite. The N-doped graphene composite is microporous with a maximum BET surface area of 1336 m 2 g-1. It shows a highly reversible maximum CO2 storage capacity of 2.7 mmol g-1 at 298 K and 1 atm (5.8 mmol g -1 at 273 K and 1 atm). The N-doped graphene shows good stability during recycling with only an initial decrease of 10% (3-2.7 mmol g -1) in adsorption capacity before attaining a cycling equilibrium. The adsorbance capacity is correlated with N content ?? pore volume or N content ?? surface area. Given that there is no proper correlation parameter, these factors can be used to increase the CO2 adsorption capacity of N-doped graphene materials for practical utility. The as synthesized material also displays selectivity towards CO2 adsorption compared to H2, N2, Ar or CH4. The as formed material shows that graphene can be uniformly N-doped using the presented synthetic method.close9

Highly selective CO2 capture by S-doped microporous carbon materials

S-doped microporous carbon materials were synthesized by the chemical activation of a reduced-graphene-oxide/poly-thiophene material. The material displayed a large CO2 adsorption capacity of 4.5 mmol g-1 at 298 K and 1 atm, as well as an impressive CO2 adsorption selectivity over N2, CH4 and H2. The material was shown to exhibit a stable recycling adsorption capacity of 4.0 mmol g -1. The synthesized material showed a maximum specific surface area of 1567 m2 g-1 and an optimal CO2 adsorption pore size of 0.6 nm. The microporosity, surface area and oxidized S content of the material were found to be the determining factors for CO2 adsorption. These properties show that the as synthesized S-doped microporous carbon material can be more effective than similarly prepared N-doped microporous carbons in CO2 capture.close12

Functionalization of Graphene: Covalent and Non-Covalent Approaches, Derivatives and Applications

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Highly selective CO2 capture on N-doped carbon produced by chemical activation of polypyrrole functionalized graphene sheets

N-doped porous carbon produced via chemical activation of polypyrrole functionalized graphene sheets shows selective adsorption of CO2 (4.3 mmol g(-1)) over N-2 (0.27 mmol g(-1)) at 298 K. The potential for large scale production and facile regeneration makes this material useful for industrial applications.open11171165sciescopu