Initial H2S Concentration Research Articles

Parametric investigation and RSM optimization of DBD plasma methods (direct & indirect) for H2S conversion in the air

Hydrogen sulfide (H2S) is known as a harmful pollutant for the environment and human health, and its emission control is a high priority. Non-thermal plasma is an effective technology in this field. In this study, for the first time, the performance of direct and indirect H2S plasma conversion methods was compared, optimized, and modeled with the CCD method. H2S was diluted in zero air, and the study investigated the effect of discharge power, relative humidity, total flow rate, initial H2S concentration, and their interactions. ANOVA results showed that the models for H2S conversion efficiency and energy yield were significant and efficient. The direct method achieved a maximum conversion efficiency of 56 % and energy yield of 3.43 g/kWh, while the indirect method produced 68 % conversion efficiency and 1.59 g/kWh energy yield. According to the process optimization results, the direct conversion method is more optimal than the indirect conversion method due to the presence of active species and high-energy electrons in the plasma treatment, and it is a better choice if there are suitable working conditions.

Noncorrosive Metal Complex Catalysts for Oxidation of Hydrogen Sulfide and Mercaptans in Petroleum Products

High activity of metal complex catalytic systems comprising nitrogenous bases and copper sulfates, acetates, and basic carbonate in oxidation of hydrogen sulfide and light mercaptans with atmospheric oxygen was established. Their activities are close to that observed for the chlorine-containing analogs, while no corrosion effect is exerted. An increase in the initial concentration of H2S has negligible effect on its conversion rate. Mercaptans do not affect the H2S oxidation rate, whereas an increase in the hydrogen sulfide concentration decelerates mercaptan oxidation. This is a diffusion-controlled reaction; hence, intensification of mixing of the catalyst with the hydrocarbons affords a 30–40% increase in the demercaptanization efficiency. The efficiencies displayed in demercaptanization processes by the catalytic systems and by the conventional scavengers neutralizing light sulfur impurities were compared.

A cleaner application on hydrogen sulfide

With the increasing industrial production, there was a significant number of toxic and harmful hydrogen sulfide (H2S) gas generated. Due to the industrial activities, converting H2S gas from the waste of industrial process is environmentally attractive. This paper focuses on the conversion of H2S to elemental sulfur (S°) and other sulfur species (i.e., sulfite ion (SO32-); sulfate ion (SO42-) using Fenton reagent. The effects of some reaction parameters such as Fe2+ ion concentration, amount of hydrogen peroxide (H2O2), reaction time, initial H2S concentration and, liquid-gas ratio on H2S conversion percentage were explored thoroughly. The results revealed that the increase of the Fe2+ ion concentration and H2O2 quantity could promote the conversion of H2S. Besides, the comparable results were recorded for each reaction parameter. An apparent positive effect was observed with increasing the amount of H2O2 on H2S conversion. However, the conversion percentage was decreased while increased in the initial concentration of the H2S in the Fenton reactor. It was well accepted that the main conversion pathway of H2S was hydroxyl radical (•OH). Additionally, the oxidative reaction of H2O2 on H2S is thought another removal pathway. The expected products are sulphuric acid and S°.

Covalent modification of reduced graphene oxide with piperazine as a novel nanoadsorbent for removal of H2S gas

In the present research, piperazine grafted-reduced graphene oxide RGO-N-(piperazine) was synthesized through a three-step reaction and employed as a highly efficient nanoadsorbent for H2S gas removal. Temperature optimization within the range of 30–90 °C was set which significantly improved the adsorption capacity of the nanoadsorbent. The operational conditions including the initial concentration of H2S (60,000 ppm) with CH4 (15 vol%), H2O (10 vol%), O2 (3 vol%) and the rest by helium gas and gas hour space velocity (GHSV) 4000–6000 h−1 were examined on adsorption capacity. The results of the removal of H2S after 180 min by RGO-N-(piperazine), reduced graphene oxide (RGO), and graphene oxide (GO) were reported as 99.71, 99.18, and 99.38, respectively. Also, the output concentration of H2S after 180 min by RGO-N-(piperazine), RGO, and GO was found to be 170, 488, and 369 ppm, respectively. Both chemisorption and physisorption are suggested as mechanism in which the chemisorption is based on an acid–base reaction between H2S and amine, epoxy, hydroxyl functional groups on the surface of RGO-N-(piperazine), GO, and RGO. The piperazine augmentation of removal percentage can be attributed to the presence of amine functional groups in the case of RGO-N-(piperazine) versus RGO and GO. Finally, analyses of the equilibrium models used to describe the experimental data showed that the three-parameter isotherm equations Toth and Sips provided slightly better fits compared to the three-parameter isotherms.

Preparation of activated red mud and its application for removal of hydrogen sulfide in air

Red mud is a highly alkaline solid waste from the Bayer process for aluminum production. Red mud reservoirs are usually considered as a potential environmental risk. The treatment of red mud is costly due to the lack of an effective and economical treatment technology. On the other hand, the main components of red mud are Fe2O3, Al2O3, SiO2, and Na2O, which could be employed as a promising precursor for the preparation of various nanomaterials. In this study, we prepared activated red mud by thermal and acid treatment method and applied it for adsorption of H2S in air. The red mud was activated under different temperatures (i.e., 200, 400, 600, and 800 oC for 4 h), types of acid (i.e., H2SO4 and HCl), and acid concentrations (i.e., 0.5, 1.5, and 2.5 M). The produced materials were then applied for H2S removal in air with concentration of 90 – 110 mg/m3 using a fix-bed adsorption column test. Results showed that red mud activated at 800 oC and with 1.5 M H2SO4 solution had the highest adsorption capacity of 29.38 mg/g with an average removal efficiency of 80.2%. The effects of gas flow rate and initial H2S concentration were also investigated, and the highest removal capacity was achieved at an inlet concentration of 100 mg/m3 and flow rate of 1 L/min. Both Langmuir and Freundlich adsorption isotherms were employed for modelling the H2S adsorption by this material and the experimental result was more fitted with the Langmuir isotherm. The thermal desorption and recyclability test were also conducted for evaluating the practical application of activated red mud material and 200 oC was the suggested desorption temperature with 81.7% adsorption capacity recovery.

Rapid photolysis of H2S and the mechanism using high-frequency discharge electrodeless lamp

ABSTRACT In the present study, the H2S photolysis using the self-made high-frequency discharge electrodeless lamp (light distribution was 90% at 254 nm and 10% at 185 nm) was studied and simulated by MATLAB software. Firstly, the effects of the initial H2S concentration, irradiation time, oxygen content and relative humidity on H2S photolysis efficiency were experimentally investigated. The results indicated that the photolysis efficiency decreased from 100% to 90.13% with the increase in the initial concentration from 3 to 30 mg/m3, and the main product was H2SO4. With the relative humidity increased from 0% to 99%, H2S photolysis efficiency was obviously improved under different atmospheres (O2 > air > Ar), indicating the significant effect of relative humidity and oxygen concentration. The simulation results were consistent with the experimental results, indicating the feasibility of the simulation model. Moreover, based on the photoreactions, model simulation and equilibrium analysis of sulphur species, the photodegradation pathway of H2S was further inferred. H2S was oxidized to H2SO4 by O3 and other strong oxidizing radicals excited by 185 nm UV light.

Application of Molybdenum oxide nanoparticles in H2S removal from natural gas under different operational and geometrical conditions

Microporous and nanoporous metal oxides are potential adsorbents for separating H2S from natural gas. Structured porous adsorbents have the potential to improve the energy and production costs in gas separation and catalysis applications by providing higher production rates. Zinc, Manganese, and Iron oxide nanoparticles are among the most potential and most extensively employed materials. Applying this framework, other novel metal oxides have been recognized for separation of H2S from representative H2S/CH4. In the present study, we investigate the performance of Molybdenum oxide nano-particles as an adsorbent for H2S removal and compare it with the performance of zinc oxide nano-particles. The effects of operating conditions such as temperature (65–89 °C), pressure (10–19 bar), initial concentration of H2S in the feed stream (38–73 ppm), and space velocity (0.018–0.045 m s−1) on H2S adsorption from sour gas are evaluated. Our analysis shows that Molybdenum oxide nano-particles have an adsorption capacity of 0.081 and 0.074 g H2S/g Molybdenum oxide in low temperature and low concentration of H2S using non-spherical and spherical Molybdenum oxide sorbent, respectively. Proceeding by two adsorption isotherms, the Langmuir and Freundlich isotherms, analysis of variance displayed that both models can fit the adsorption data of H2S on Molybdenum oxide nanoparticles very well, while the Freundlich isotherm seems to provide R2 value of 0.98–0.99, indicating a better prediction of our experimental data.

Preparation of activated carbon from peanut shell with KOH activation and its application for H2S adsorption in confined space

Hydrogen sulfide (H2S), as a major air pollutant, poses a serious threat to people`s health, especially in confined spaces. In this study, a porous carbon filter was developed by impregnating a copper on activated carbon derived from peanut shell biomass. The carbonization temperature can significantly affect the texture properties of activated carbon, and the optimized temperature was 450 ℃. The optimal activated carbon sample (SBET = 1523.2 m2/g, Vmicro = 0.533 cm3/g) was prepared at a carbonization temperature of 450℃ and KOH activation at 750 ℃. The best adsorption performance was obtained with a copper impregnated optimal activated carbon (Cu/PAC-450) filter, and the maximum adsorption capacity was found to be 97.63 mg/g. As the initial concentration of H2S increased, the adsorption efficiency decreased. Adsorption isotherm and kinetic studies showed that Langmuir isotherm model was the best-fitted model for the adsorption of H2S on Cu/PAC-450 filter, with a correlation coefficient of 0.9627. The adsorption kinetic process followed the pseudo first order model, and the adsorption mechanism was controlled by intraparticle diffusion along with film diffusion model. The used Cu/PAC-450 filter can be successfully regenerated, which showed good reusability. The Cu/PAC-450 has a very broad prospect for use in household appliances (such as refrigerator, air conditioner, microwave oven, etc.) for indoor air purification. Therefore, this study is expected to expand the utilization of agriculture waste for the indoor air purification.

Experimental Analysis and Model Validation on the Performance of Impregnated Activated Carbons for the Removal of Hydrogen Sulfide (H2S) from Sewage Biogas

Organic waste exploitation is crucial for waste emissions restraint in air, soil and water. This type of waste can be exploited to produce biogas, a valuable fuel exploitable for energy purposes. A circular approach for energy production is much cleaner and more sustainable than the traditional linear approach. In this work, organic waste was used for biogas production to feed a highly efficient solid oxide fuel cell power generator, which requires an ultra-purified fuel. Commercial sorbents were experimentally studied in conjunction with a dynamic adsorption model to predict the breakthrough time and organize the material change-over. In the presence of 0.1% oxygen in the gas mixture, AirDep® CKC showed a marked increase in the adsorption capacity (from 3.91 to 84.87 mg/g), overcoming SulfaTrap® R8G (49.91 mg/g). The effect of several operating parameters on adsorption capacity was evaluated: inlet H2S concentration, filter geometry and gas mixture velocity. Experimental data revealed that adsorption capacity increases with initial H2S concentration, following the typical trend of the Langmuir isotherm. Model simulations were in good agreement compared to experimental results, with an average relative error lower than 7%. A sensitivity analysis on the adsorption capacity was accomplished considering parameters from operational and empirical correlations.

Removal of hydrogen sulfide on activated carbon supported ionic liquids

In this study, ionic liquid loaded activated carbon was applied as the adsorbent for hydrogen sulfide (H2S) removal under the anaerobic conditions in a fixed bed. The effects of activated carbon substrate, ionic liquid, initial H2S concentration and flow rate on the adsorption process were systematically studied. The experimental results show that the activated carbon named AC-1 having higher surface area and micropore volume is more suitable as the support for ionic liquid. Amongst three ionic liquids studied, the 1-ethyl-3-methylimidazolium acetate loaded activated carbon exhibites the highest H2S sorption capacity performance. As a results of the superior performance of the 1-ethyl-3-methylimidazolium acetate loaded activated carbon, further tests and characterizations were performed on the sorbent. The breakthrough capacity of 1-ethyl-3-methylimidazolium acetate sorbent is two times greater than pure activated carbon. In addition, it is confirmed that increasing H2S concentration enhances H2S adsorption capacity, and the adsorption capacity of H2S decreases significantly with increasing gas flow rate.

Mathematical Modeling and Mechanism of VUV Photodegradation of H2S in the Absence of O2

The existence of H2S has limited the biogas energy promotion. The traditional photodegradation of H2S is usually conducted in the presence of O2, yet this is unsuitable for biogas desulfurization which should be avoided. Therefore, the ultraviolet degradation of H2S in the absence of O2 was investigated for the first time in the present study from a mathematical point of view. Light wavelength and intensity applied were 185 nm and 2.16 × 10−12 Einstein/cm2·s, respectively. Firstly, the mathematical model of H2S photodegradation was established with MATLAB software, including the gas flow distribution model and radiation model of photoreactor, kinetics model, mass balance model, and calculation model of the degradation rate. Then, the influence of the initial H2S concentration and gas retention time on the photodegradation rate were studied, for verification of the mathematical model. Results indicated that the photodegradation rate decreased with the increase in initial H2S concentration, and the maximum photodegradation rate reached 62.8% under initial concentration of 3 mg/m3. In addition, the photodegradation rate of H2S increased with the increase in retention time. The experimental results were in good accordance with the modeling results, indicating the feasibility of the mathematical model to simulate the photodegradation of H2S. Finally, the intermediate products were simulated and results showed that the main photodegradation products were found to be H2 and elemental S, and concentrations of the two main products were close and agreed well with the reaction stoichiometric coefficients. Moreover, the concentration of free radicals of H• and SH• was rather low.

Remoción de ácido sulfhídrico por microorganismos sobre lodos activados en aguas residuales de la industria alimenticia

La importancia del siguiente trabajo radica en implementar un tratamiento de remoción de H2S con un bajo impacto ambiental. El objetivo fue el de evaluar microorganismos eficientes para la remoción de ácido sulfhídrico sobre lodos activados de las aguas residuales industriales. Se construyó un biofiltro con microorganismos eficientes, lodo activado y material filtrante. Se inocularon durante tres semanas en lodos 21 litros de microorganismos eficientes activado, controlando parámetros como pH, temperatura, humedad, oxígeno y luz solar, garantizando las condiciones aptas de desarrollo de bacterias fotosintéticas, ácido lácticas y levaduras. El muestreo del agua residual se realizó en la caja de revisión más cercana al punto de descarga al alcantarillado de La Ibérica, y para su análisis a la salida del biofiltro, tomando una muestra con tres repeticiones cada semana, durante 21 días, para conocer la concentración inicial, intermedia y final de H2S y el porcentaje de remoción alcanzado en el tratamiento. Los resultados de la investigación dictaminaron que los microorganismos eficientes aumentaron la carga microbiana de los microorganismos endógenos en el lodo, consiguiendo un mejor crecimiento de la biopelícula y logrando la reducción de la concentración de H2S de 3,68 mg/L a 0,45 mg/L, alcanzando un porcentaje de remoción del 70,35%. El presente trabajo analiza que a mayores tiempos de retención se da una mejor actuación de microorganismos eficientes en el tratamiento. La utilización de microorganismos eficientes en la remoción de H2 S, resulta rentable por sus tiempos cortos de actuación y bajos costos de aplicación.

Parametric study of sweetening process of sour gas by Molybdenum oxide nanoparticles

Abstract The purpose of this work is to study the application of nano-molybdenum oxide adsorbent in gas sweetening process. Experiments were made to evaluate the operating and geometrical parameters in the adsorption process. The process performance of H2S removal from methane gas on molybdenum oxide nanoparticles was defined as the ratio of final concentration of H2S on the initial concentration of H2S. The effects of operating conditions such as operating temperature, pressure, the size of nanoparticles, the amount of H2S concentration in feed stream, feed superficial velocity, and the bed length were studied in this paper. Different temperature values (65, 75, 85, 87 and 89 °C) and pressure values (10, 13, 16 and 19 bar) were applied on the adsorption bed with 19 cm length and 10 cm diameter. Two types of spherical and cylindrical nanoparticles were applied and the effect of different adsorbents diameters (54, 58, 73, 77 and 83 nm) on the process quality (C/C 0 ) was investigated. Also, the effect of initial concentration of H2S in the feed gas stream was surveyed. The optimum operating conditions for spherical and cylindrical types were the same, 16 bar and 85 °C. The adsorption capacity of 0.22 g H2S/g MoO2 and 0.19 g H2S/g MoO2 was achieved at the optimum conditions using nano-spherical and nano-cylindrical MoO2 sorbent, respectively. Applying in our study two adsorption isotherms, the Langmuir and Freundlich isotherms, analysis of variance displayed a high coefficient of determination (R2) value of 0.989 for the Freundlich isotherm, indicating the satisfactory adjustment of the experimental data. The results can be interesting for related industries and can be applicable in process optimization.

Performance of Paracoccus pantotrophus for H2S removal in biotrickling filter

Paracoccus pantotrophus NTV02 (PCP), a novel strain of sulfur oxidizer isolated from a full-scale leather industry wastewater treatment plant, was used for hydrogen sulfide (H2S) removal from synthetic biogas in a biotrickling filter system. Its growth and sulfur oxidation activity were initially evaluated in batch reactors with the culture media containing 10 g/L thiosulfate and varying glucose concentrations (0.5–2.0 g/L) prepared in 52 mM phosphate buffer (pH 8). Its maximum growth rate (0.57 ± 0.00 h−1) was observed at 1 g/L glucose, while the maximum sulfate production rate (159.21 ± 2.48 mg/L·h) was found at 0.5 g/L glucose. The replacement of fresh nutrient containing-recirculation medium every 48 h, and pH adjustment (pH 8.0) every 24 h was the optimum practice for H2S removal in the biotrickling filter operation. At the optimum operation, H2S was removed up to 96% when the initial H2S concentration was in the range of 150–400 ppmv.

Design of a MT-DBD reactor for H2S control**Supported by programs of Research on the Technology and Equipment of Gaseous Pollutant Removal from the Emission of Household Garbage (15DZ12055904) and Jointly Decomposition of Odorous Compounds by Dielectric Combined with Excimer Ultraviolet Emission (21577023).

This study aimed to discuss the removal of hydrogen sulfide (H2S) with non-thermal plasma produced by a multilayer tubular dielectric barrier discharge reactor, which is useful in the field of plasma environmental applications. We explored the influence of various factors upon H2S removal efficiency () and energy yield (Ey), such as specific energy density (SED), initial concentration, gas flow velocity and the reactor configuration. The study showed that we can achieve of 91% and the best Ey of 3100 mg kWh−1 when we set the SED, gas flow velocity, initial H2S concentration and layers of quartz tubes at 33.2 J l−1, 8.0 m s−1, 30 mg m−3 and five layers, correspondingly. The average rate constant for the decomposition of hydrogen sulfide was 0.206 g m−3 s−1. In addition, we also presented the optimized working conditions, by-product analysis and decomposition mechanism.

Modeling of CO2 injection into aquifers containing dissolved H2S

In this paper, analytical one-dimensional modeling of CO2 injection into aquifers which contain dissolved H2S is presented. When CO2 is injected into such aquifers, the H2S initially dissolved in the brine will be exsolved and released into CO2 plume. It was shown that depending on reservoir pressure and temperature as well as on initial concentration of H2S the leading edge of CO2 plume may contain 100% H2S which is in free phase. The highly toxic nature of H2S gas suggests the need to account for dissolved H2S in aquifers when establishing risk assessment, monitoring, and management strategies at CO2 storage sites.

Experimental and modeling study on room-temperature removal of hydrogen sulfide using a low-cost extruded Fe2O3-based adsorbent

In order to prevent corrosion and catalyst deactivation, commercial adsorption processes for hydrogen sulfide (H2S) removal operate at relatively high temperature (350–450 °C) by ZnO adsorption. This paper reports firstly data from experimental and modeling studies of the dynamic performance of a low-cost extruded Fe2O3 -based adsorbent for H2S removal at room temperature. The H2S adsorbent containing iron (III) oxide (Fe2O3) and bentonite was prepared by hydrothermal-precipitation method and the material has been characterized by several techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), and low temperature N2 physical adsorption. The Fe2O3-based extruded adsorbent was used in a continuous fixed-bed column experiments to evaluate the efficiency for removal of H2S under the effect of various process parameters including the bed depth, the flow rate and the initial H2S concentration. The results showed that the total H2S uptake slightly increased with increasing the bed depth and the initial H2S concentration, and decreased with increasing the flow rate. In the modeling part, the dynamics of the adsorption process was modeled by two adsorption models namely, Thomas model and BDST (bed depth service time) model. The kinetic parameters obtained from the models were used to predict the breakthrough time for a larger column which contained the adsorbent about 40 times more than that in the mini column experiments. The Thomas model was the suitable model for prediction of 10 % C0 breakthrough time with an error about 4 %.

Gas-phase removal of hydrogen sulfide using iron oxyhydroxide at low temperature: Measurement of breakthrough curve and modeling of sulfidation mechanism

Abstract With the aim of removing hydrogen sulfide (H2S) from a gaseous phase around room temperature, we studied the performance of an iron oxyhydroxide (ferrihydrite) adsorbent by measuring a packed bed breakthrough curve (BTC) in a constant gas flow. We determined the amount of H2S adsorbed on the adsorbent by integrating BTCs measured under different experimental conditions. These conditions included the initial concentration of H2S, the superficial gas velocity and the temperature of the packed bed. Under the experimental conditions, it was found that the amount of H2S adsorbed was almost unchanged by the superficial gas velocity, whereas the adsorbed amount depended on the initial concentration of H2S and temperature. To solve the mass transfer equations in the packed bed, we developed a model considering such parameters as the kinetic constant of the sulfidation reaction, the intragranular diffusivity of H2S, and the number density of active sites on the adsorbent. By fitting the calculated BTC to the measured BTC under one of the experimental conditions, the set of parameters could be estimated. Using the same set of estimated parameters, we calculated the BTCs under the other experimental conditions. As a result, we confirmed that the calculated BTC coincided with the BTC measured under a different initial H2S concentration and gas velocity. We also found that the number density of the active sites increased with increases in temperature.

Photolysis of low concentration H2S under UV/VUV irradiation emitted from high frequency discharge electrodeless lamps

The photolysis of low concentration of H2S malodorous gas was studied under UV irradiation emitted by self-made high frequency discharge electrodeless lamp with atomic mercury lines at 185/253.7nm. Experiments results showed that the removal efficiency (ηH2S) of H2S was decreased with increasing initial H2S concentration and increased slightly with gas residence time. ηH2S was increased dramatically with relative humidity from<5% to 43% while the concentration of oxygen in gas environments affected the removal of H2S. The mechanisms for direct and indirect photolysis (generation of ozone) were illustrated by the experimental results on photolysis of H2S under argon environments and ozonation of H2S under air environments, respectively. The overall ηH2S by photolysis is higher than the combination of ηH2S by direct photolysis and ozonation, suggesting that hydroxyl radical-mediated indirect photolysis played an important role during photolysis processes. The main photolysis product was confirmed to be SO42- with ion chromatograph.

Kinetics of hydrogen sulfide decomposition in a DBD plasma reactor operated at high temperature

The present study investigates the kinetics of hydrogen sulfide (H2S) decomposition into hydrogen and sulfur carried out in a nonthermal plasma dielectric barrier discharge (NTP-DBD) reactor operated at ∼430 K for in situ removal of sulfur condensed inside the reactor walls. The dissociation of H2S was primarily initiated by the excitation of carrier gas (Ar) through electron collisions which appeared to be the rate determining step. The experiments were carried out with initial concentration of H2S varied between 5 and 25 vol% at 150 mL/min (at standard temperature and pressure) flow rate in the input power range of 0.5 to 2 W. The reaction rate model based on continuous stirred tank reactor (CSTR) model failed to explain the global kinetics of H2S decomposition, probably due to the multiple complex reactions involved in H2S decomposition, whereas Michaelis-Menten model was satisfactory. Typical results indicated that the reaction order approached zero with increasing inlet concentration.