Adsorption Of Hydrogen Sulfide Research Articles

Municipal waste conversion to hydrogen sulfide adsorbents: Investigation of the synergistic effects of sewage sludge/fish waste mixture

Mixtures of sewage sludge and fish waste of various compositions were prepared and pyrolyzed at 950°C in an inert atmosphere. On the pyrolyzed samples an activation with CO2 was carried out at 850°C. The materials were used as H2S adsorbents at ambient conditions. Initial and spent samples were characterized using thermal analysis, XRD, XRF, SEM/EDX, sorption of nitrogen and surface pH measurements. An enhancement in the H2S removal capacity on the composite samples was linked to the synergistic effects of chemical composition. The adsorbents’ surface reactivity was linked to the presence of Na, K, Ca, Mg and Fe in various configurations. Activation had a detrimental effect on the composites’ performance as adsorbents of H2S. The sludge component provides an active iron phase, which is important for hydrogen sulfide oxidation. Potassium and sodium polysulfides and iron sulfite, sulfate, sulfide are the products of reactive adsorption. The strongest synergistic effect was found for the composite with the lowest content of the fish component. With an increase in the content of the fish waste this effect diminishes owing to the reactions of alkaline metals with silica during pyrolysis.

Effect of Reduced Graphite Oxide as Substrate for Zinc Oxide to Hydrogen Sulfide Adsorption

ZnO(산화아연)와 rGO(환원 흑연산화물, reduced graphite oxide)로 구성된 복합체를 제조하여 중저온 영역(300-500 ℃)에서 H₂S(황화수소) 흡착실험을 수행하였다. rGO에 붙어있는 수산화기, 에폭시기, 그리고 카르복실기와 같은 산소를 포함하는 관능기들이 H₂S흡착에 미치는 영향을 조사하기 위해서 다양한 특성분석(TGA, XRD, FT-IR, SEM, 그리고 XPS)을 실시하였다. GO(흑연산화물, graphite oxide)를 rGO로 환원시키기 위해서 마이크로파 조사법을 사용하였다. 마이크로파 조사법에 의한 환원공정에서는 온화한 환원분위기를 조성하여 rGO 표면에 상당량의 산소 관능기들이 남아있는 것을 확인하였다. 이러한 관능기들은 나노 크기의 ZnO가 2D rGO 표면에 균일하게 부착되도록 유도하여 고온 영역에서도 ZnO의 응집 및 소결이 일어나는 것을 방지하는 효과가 있다. 이로 인해 ZnO/rGO 복합체는 순수한 ZnO와 비교하여 3.5배 정도의 흡착량을 보여주었다.

Ethane Steam Reforming over a Platinum/Alumina Catalyst: Effect of Sulfur Poisoning

In this study we have examined the adsorption of hydrogen sulfide and methanethiol over platinum catalysts and examined the effect of these poisons on the steam reforming of ethane. Adsorption of hydrogen sulfide was measured at 293 and 873 K. At 873 K the adsorbed state of hydrogen sulfide in the presence of hydrogen was SH rather than S, even though the Pt:S ratio was unity. The effect of 11.2 ppm hydrogen sulfide or methanethiol on the steam reforming of ethane was studied at 873 K and 20 barg. Both poisons deactivated the catalyst over a number of hours, but methanethiol was found to be more deleterious, reducing the conversion by almost an order of magnitude, possibly due to the co-deposition of sulfur and carbon. Changes in the selectivity revealed that the effect of sulfur was not uniform on the reactions occurring, with the production of methane reduced proportionally more than the other products, due to the surface sensitivity of the hydrogenolysis and methanation reactions. The water-gas shift reaction was affected to a lesser extent. No regeneration was observed when hydrogen sulfide was removed from the feedstream in agreement with adsorption studies. A slight regeneration was observed when methanethiol was removed from the feed, but this was believed to be due to the removal of carbon rather than sulfur. The overall effect of sulfur poisoning was to reduce activity and enhance hydrogen selectivity.

Adsorption of Hydrogen Sulphide on the Zeolite type A Synthezied from Iraqi Kaoline

Three types of zeolite A were prepared from Iraqi kaoline which are 3A, 4A and 5A by ion exchange method .They were characterized by XRD and atomic absorption techniques .They were used as adsorbents to examine their applicability for H2S adsorption .The adsorption process was performed in a static form and constant volume system which constructed from stainless steel .The effect of zeolite type and temperature on the adsorption properties of H2S at -5 , 25 and 55 oC was studied .The zeolite type 5A has the highest adsorption value (79.384 µmol/g ) and the three types may be arranged in a sequence toward H2S adsorption as 5 A> 4A>3A .The amount of H2S adsorbed increased as temperature decreased from 55 to -5 for all samples. Langmuir , Frendlich and Toth isotherm equations model were applied for the adsorption data in order to determine the affinity and the heterogeneity of the three adsorbents. The heterogeneity parameters of the model equation applied indicated that 5A sample was more heterogeneous compared to other zeolite types.

Adsorption of Hydrogen Sulphide on the Zeolite type A Synthezied from Iraqi Kaoline

Three types of zeolite A were prepared from Iraqi kaoline which are 3A, 4A and 5A by ion exchange method .They were characterized by XRD and atomic absorption techniques .They were used as adsorbents to examine their applicability for H2S adsorption .The adsorption process was performed in a static form and constant volume system which constructed from stainless steel .The effect of zeolite type and temperature on the adsorption properties of H2S at -5 , 25 and 55 oC was studied .The zeolite type 5A has the highest adsorption value (79.384 µmol/g ) and the three types may be arranged in a sequence toward H2S adsorption as 5 A> 4A>3A .The amount of H2S adsorbed increased as temperature decreased from 55 to -5 for all samples. Langmuir , Frendlich and Toth isotherm equations model were applied for the adsorption data in order to determine the affinity and the heterogeneity of the three adsorbents. The heterogeneity parameters of the model equation applied indicated that 5A sample was more heterogeneous compared to other zeolite types.

DFT study on the adsorption and dissociation of hydrogen sulfide on MgO nanotube

The adsorption of a H2S molecule on the surface of an MgO nanotube was investigated using density functional theory. It was found that H2S molecule can be associatively adsorbed on the tube surface without any energy barrier or it can be dissociated into –H and –SH species overcoming energy barrier of 4.03–7.77 kcal/mol. The associative adsorption is site selective so that the molecule is oriented in such a way that the sulfur atom was linked to an Mg atom. The HOMO–LUMO energy gap of the tube has slightly changed upon associative adsorption, while they were significantly influenced by dissociation process. Especially, the highest occupied molecular orbital of the tube shifts to higher energies which can facilitate electron emission current from the tube surface. Also, energy gap of the tube dramatically decreased by about 0.93–1.05 eV which influences the electrical conductivity of the tube.

The mechanism of hydrogen sulfide adsorption on fine rubber particle media (FRPM)

A commercial rubber waste product, fine rubber particle media (FRPM), was found to adsorb hydrogen sulfide (H2S) at 0.12mg H2S/g FRPM of adsorption capacity. Since FRPM seems to be an attractive alternative to treat H2S owing to its economic advantages as well as its physicochemical characteristics, several analyses were conducted to investigate fundamental information, surface properties, and breakthrough characteristics of FRPM as adsorbent. The physical properties of FRPM including composition and surface chemistry were investigated to compare its performance with commonly available commercial H2S adsorbents such as activated carbon and assess the possible adsorption mechanism. The specific surface area of FRPM was less than 1% of activated carbon. FRPM does not have enough surface area supporting a pure physical adsorption of H2S because it is particulate in nature with limited porosity. The adsorption of FRPM to remove H2S was complex mechanism and involved a combination of zinc compounds and carbon black.

Enhanced adsorption of hydrogen sulfide on mixed zinc/cobalt hydroxides: Effect of morphology and an increased number of surface hydroxyl groups

Mixed zinc and cobalt hydroxides were synthesized using a precipitation method and tested as adsorbents of hydrogen sulfide from either dry or moist air. The adsorption capacity increased with an increase in the content of cobalt in the structure of mixed hydroxides. The synergistic effect was demonstrated by a fourfold increase in the amount of hydrogen sulfide adsorbed on the surface of the best performing mixed hydroxide in comparison with the hypothetical mixture of the two hydroxides. The initial and exhausted materials were characterized by FTIR, thermal analysis, potentiometric titration, X-ray diffraction, SEM/EDX, and adsorption of nitrogen. The results obtained suggest that an increase in the content of cobalt results in an increase in amorphicity level and in an increase in the number of hydroxyl groups. These groups, besides providing higher basicity thereby increasing the extent of H2S dissociation in the presence of water, are the main active centers reacting with hydrogen sulfide. Defects in the structure and oxygen vacancies result in the oxidation of some H2S to sulfites and sulfates.

Density functional theory studies of the adsorption of hydrogen sulfide on aluminum doped silicane

First principles total energy calculations have been performed to study the hydrogen sulfide (H2S) adsorption on silicane, an unusual one monolayer of Si(111) surface hydrogenated on both sides. The H2S adsorption may take place in dissociative or non-dissociative forms. Silicane has been considered as: (A) non-doped with a hydrogen vacancy, and doped in two main configurations; (B) with an aluminum replacing a hydrogen atom and (C-n; n = 1, 2, 3) with an aluminum replacing a silicon atom at a lattice site. In addition, three supercells; 4x4, 3x3 and 2x2 have been explored for both non-doped and doped silicane. The non-dissociative adsorption takes place in geometries (A), (C-1), (C-2) and (C-3) while the dissociative in (B). Adsorption energies of the dissociative case are larger than those corresponding to the non-dissociated cases. In the dissociative adsorption, the molecule is fragmented in a HS structure and a H atom which are bonded to the aluminum to form a H-S-Al-H structure. The presence of the doping produces some electronic changes as the periodicity varies. Calculations of the total density of states (DOS) indicate that in most cases the energy gap decreases as the periodicity changes from 4x4 to 2x2. The features of the total DOS are explained in terms of the partial DOS. The reported charge density plots explain quite well the chemisorptions and physisorptions of the molecule on silicane in agreement with adsorption energies.

Effect of active zinc oxide dispersion on reduced graphite oxide for hydrogen sulfide adsorption at mid-temperature

Composites of Zinc oxide (ZnO) with reduced graphite oxide (rGO) were synthesized and used as adsorbents for hydrogen sulfide (H2S) at 300°C. Various characterization methods (TGA, XRD, FT-IR, TEM and XPS) were performed in order to link their H2S adsorption performance to the properties of the adsorbent's surface. Microwave-assisted reduction process of graphite oxide (GO) provided mild reduction environment, allowing oxygen-containing functional groups to remain on the rGO surface. It was confirmed that for the ZnO/rGO synthesize using the microwave-assisted reduction method, the ZnO particle size and the degree of ZnO dispersion remained stable over time at 300°C, which was not the case for only the ZnO particles themselves. This stable highly dispersed feature allows for sustained high surface area over time. This was confirmed through breakthrough experiments for H2S adsorption where it was found that the ZnO/rGO composite showed almost four times higher ZnO utilization efficiency than ZnO itself. The effect of the H2 and CO2 on H2S adsorption was also investigated. The presence of hydrogen in the H2S stream had a positive effect on the removal of H2S since it allows a reducing environment for ZnO and ZnS bonds, leading to more active sites (Zn2+) to sulfur molecules. On the other hand, the presence of carbon dioxide (CO2) showed the opposite trend, likely due to the oxidation environment and also due to possible competitive adsorption between H2S and CO2.

Hydrogen sulfide adsorption on nano-sized zinc oxide/reduced graphite oxide composite at ambient condition

This paper presents new insights on the synthesis of nano-ZnO on reduced graphite oxide (rGO) composite via a microwave-assisted route and its use as a potential sorbent to adsorb hydrogen sulfide (H2S) at ambient conditions. Depending on the synthesis methods, the nano-sized ZnO on rGO presents different characteristics, in particular the degree of nano-ZnO dispersion on the surface of the rGO. Microwave-assisted reduction was able to offer a mild reduction to the oxygen-containing functional groups attached on the surface of graphite oxide (GO). Those oxygen-containing functional groups provide the bridge and the terminal groups between zinc oxide and the rGO surface. Because those functional groups act as anchor sites for metal ions, it was possible to achieve uniformly distributed nano-sized ZnO particles on the surface of the rGO sheets. In addition, they accelerate oxygen activation for H2S adsorption. H2S adsorption tests at ambient conditions were conducted. The 1-D carbon nanotubes (CNTs) had been used for reference in order to investigate the functionality of 2-D rGO substrate. Also, the effects of the different synthesis methods (microwave vs. reflux) were evaluated for H2S adsorption. The adsorption capacity increased dramatically for the microwave-assisted composite compared to the composite manufactured using the reflux method.

A theoretical analysis of the role of defects in the adsorption of hydrogen sulfide on graphene

Density functional theory studies are reported to analyze the interaction between hydrogen sulfide (H2S) and graphene. The electron-ion interactions have been modeled using ultrasoft pseudopotentials and the exchange-correlation energies have been approximated by the method of the generalized gradient approximation in the parameterization of Perdew-Burke-Ernzerhof. Three graphene structures, one intrinsic and two with defects (vacancy and sustitution), and four H2S concentrations have been studied. The optimal geometries, binding energies, density of states (DOS) and charge density were obtained. In order to study the adsorption process three high symmetry sites were considered, namely, top, bridge, and center. The preferential adsorption structure corresponds to the center site in a physical way. The DOS of graphene-H2S systems shows a metallic behavior which coincides with the behavior of the isolated graphene. The geometrical structure of the graphene and the hydrogen sulfide remains unchanged.

Kinetics and mechanisms of hydrogen sulfide adsorption by biochars

Three different biochars as cost-effective substitutes for activated carbon (AC) were tested for their hydrogen sulfide (H2S) adsorption ability. The biochars were produced from camphor (SC), bamboo (SB), and rice hull (SR) at 400°C by oxygen-limited pyrolysis. The surface area (SA), pH, and Fourier transform infrared spectras of the biochars and AC were compared. The maximum removal rates and the saturation constants were obtained using the Michaelis–Menten-type equation. The three biochars were found to be alkaline, and the SAs of the biochars were much smaller than that of the AC. The H2S breakthrough capacity was related to the local pH within the pore system of the biochar. The order observed in terms of both biochar and AC adsorption capacity was SR>SB>SC>AC. SR efficiently removed H2S within the inlet concentration range of 10–50μL/L. Biochars derived from agricultural/forestry wastes are a promising H2S adsorbent with distinctive properties.

ZnO Nanocluster as a Potential Catalyst for Dissociation of H2S Molecule

Adsorption of hydrogen sulfide (H2S) on the external and internal surface of Zn12O12 nanocluster was studied by using density functional calculations. The results indicate that the H2S molecule is physically adsorbed or chemically dissociated by the nanocluster. It was found that the H2S molecule can dissociate into –H and–SH fragments, suggesting that the nanocluster might be a potential catalyst for dissociation of the H2S molecule. Also, dissociation of H2S to S species in internal surface of the Zn12O12 nanocluster is energetically impossible. The HOMO–LUMO energy gap of H2S dissociation configuration is changed about 27.68 %, indicating that the electronic properties of the nanocluster by dissociation process have strongly changed.

Adsorption of H2S molecules by cucurbit[7]uril: an ab initio vdW-DF study

Among the cucurbit[n]urils, much attention has been devoted to CB[7] for its intermediary cavity size as well as the significant negative charge density of carbonyl-fringed portals which assists the binding of other species. Adsorption of hydrogen sulfide by CB[7] was studied using ab initio van der Waals density functional (vdW-DF) calculations, involving a full geometry optimization. The encapsulation of up to five H2S molecules inside the cucurbit cavity, with a binding energy of about −0.10 eV per H2S, makes cucurbit[n]urils attractive as a suitable adsorption medium. Furthermore, calculations show that H2S molecules can be adsorbed on the sidewall of the CB[7] with a larger binding energy (−0.31 eV). We also address the role of vdW forces for the system under study and the obtained results revealed that the inclusion of dispersion interactions slightly affects the binding properties of the interacting molecules. In addition, the binding nature of the energetically favorable systems in ambient conditions have been investigated with ab initio MD simulations adopting the vdW-DF method. Our ab initio vdW-DF findings afford evidence for a realistic benchmark for the applicability of these novel nanostructures for H2S adsorption and elimination from various media.

First principles calculation of adsorption for H2S on Fe(100) surface

In contrast to the results of sulfur atom adsorption, the adsorption of hydrogen sulfide on the Fe(100) surface has been studied using first principles method, which is based on the density functional theory (DFT). The structures, electronic properties were calculated by the generalized gradient approximation (GGA) for the coverage of 0.25 monolayer (ML). The results show that the H2S adsorbed on B2 site is stable and the adsorption energy is -1.23 eV and the structure of H2S is little changed. While the density of states (DOS) for the adsorption of hydrogen sulfide in the most unstable state after the adsorption at B1 and most stable adsorption at the site of B2 are analyzed. We have compared, under same conditions, the electronic properties of the sulfur atoms of the adsorbed hydrogen sulfide and a single sulfur atom adsorbed on Fe(100) surface. The adsorption effect is very weak for sulfur atoms in adsorbed hydrogen sulfide. At the same time, the density of states for the adsorption of Fe(100) surface was studied comparatively, and we found that the sulfur atom adsorption on Fe(100) showed a series of peaks that have discrete distributions generated by ferrous sulfide. It shows that the adsorption is given by sulfur atoms instead of molecules of hydrogen sulfide.

活性炭による溶存硫化水素の酸化と保持

活性炭を用いた溶存硫化物の酸化処理促進技術は，酸化処理後の硫黄形態やその存在比，および酸素消費量について，まだ十分に明らかにされていない。そこで，溶存硫化物の酸化前後の形態と酸素消費量を明らかにするために，バイアル瓶を用いたバッチ式の酸化処理実験を行った。その結果，活性炭の触媒作用によって硫化水素イオンは，硫酸イオン，チオ硫酸イオンに酸化されて溶存していることが確認できた。次に，X線光電子分光分析装置を用いて，活性炭表面にある元素とその電子状態を分析した結果，活性炭に保持された硫黄成分は，元素状硫黄であることが示唆された。また，酸化処理前後の硫黄と酸素の化学量論について計算した結果，それぞれ84％と82％の物質収支を推定することが出来た。さらに，酸化後の硫黄成分の生物毒性について調べた結果，硫化水素イオンは活性炭を用いた酸化により，毒性の低い酸化物になっていることを確認した。

Reactive adsorption of hydrogen sulfide on visible light photoactive zinc (hydr)oxide/graphite oxide and zinc (hydr)oxychloride/graphite oxide composites

Composites of zinc (hydr)oxide and graphite oxide (GO) with 2, 5, and 20wt.% of the GO component were obtained by precipitating zinc hydroxide from zinc chloride with dispersed GO present in the solution. The materials were evaluated as adsorbents of hydrogen sulfide at ambient conditions. The surface properties of the initial and exhausted samples were studied by FTIR, XRD, SEM/EDX, TEM, nitrogen adsorption, potentiometric titration, microcalorimetry, and thermal analysis. The adsorption capacity increases with an increase in the content of GO in the composites studied. The lower adsorption capacities measured for the samples with 2 and 5wt.% of graphite oxide are linked to the zinc (hydr)oxychlorides phase present in these composites. The heats of H2S adsorption on the zinc (hydr)oxide and its composites were measured in nitrogen and in air flow. The results indicate that highly energetic adsorption centers are formed on the composite surfaces. Exposure to visible light decreases the H2S adsorption capacity. This behavior is linked to photoactivity that leads to the reduction of the composite and formation of sulfur and sulfites/sulfates. These processes involve active centers, OH groups, which react with hydrogen sulfide.

Research on Hydrogen Sulfide Adsorption by Oil Shale and its Spent Char

Huadian oil shale and its spent char were selected to explore the adsorption properties of oil shale and oil shale char. A bench-scale adsorption system was established for capturing hydrogen sulfide in this test. What’s more, the nitrogen adsorption isotherms test was made in automatic and rapid specific surface-area-analyzer of American’s Gemini2380, which found the adsorption curve and desorption loop of the modified oil shale and oil shale char. Meanwhile, the experiment calculated and analyzed the specific surface area and pore size distribution of samples with BJH theory. The result shows that the adsorption capacity of oil shale char is greater than oil shale. The rougher the pore structure of the adsorbent samples the greater the pore volume, the larger the specific surface area, the better the adsorption effect of H2S.

Reactive adsorption of hydrogen sulfide by promoted sorbents Cu‐ZnO/SiO2: active sites by experiment and simulation

In the Cux‐Zn(1‐x)O/SiO2 sorbents for ultradeep adsorptive removal of H2S from gaseous fuel reformates for fuel cells at room temperature, Cu promoter sites significantly increase sulfur uptake capacity of the sorbents. We report characterization of the family of Cux‐Zn(1‐x)O/SiO2 sorbents for reactive adsorption of H2S using X‐ray diffraction (XRD), Brunauer‐Emmett‐Teller (BET) surface area analysis, electron spin resonance (ESR), ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy (DRS) and calculations by the density functional theory (DFT). Both the supported ZnO phase and Cu promoter sites in the Cux‐Zn(1‐x)O/SiO2 sorbents are nano‐dispersed, as shown by XRD. The Cux‐Zn(1‐x)O/SiO2 sorbents contain Cu promoter as the Cu2+ site of octahedral geometry, as found by the complementary ESR and UV–vis DRS. Mechanism of the promoter effect of the Cu2+ site in the Cux‐Zn(1‐x)O/SiO2 sorbents in reaction with H2S is proposed based on DFT calculations. Copyright © 2012 John Wiley & Sons, Ltd.