Hydrogen Sulfide Removal Efficiency Research Articles

From microbial heterogeneity to evolutionary insights: A strain-resolved metagenomic study of H2S-induced changes in anaerobic biofilms

The hidden layers of genomic diversity in microbiota of biotechnological interest have been only partially explored and a deeper investigation that overcome species level resolution is needed. CO2-fixating microbiota are prone to such evaluation as case study. A lab-scale trickle-bed reactor was employed to successfully achieve simultaneous biomethanation and desulfurization on artificial biogas and sulfur-rich biogas, and oxygen supplementation was also implemented. Under microaerophilic conditions, hydrogen sulfide removal efficiency of 81% and methane content of 95% were achieved. Methanobacterium sp. DTU45 emerged as predominant, and its metabolic function was tied to community-wide dynamics in sulfur catabolism. Genomic evolution was investigated in Gammaproteobacteria sp. DTU53, identified as the main contributor to microaerophilic desulfurization. Positive selection of variants in the hydrogen sulfide oxidation pathway was discovered and amino acid variants were localized on the sulfide entrance channel for sulfide:quinone oxidoreductase. Upon oxygen supplementation strain selection was the primary mechanism driving microbial adaptation, rather than a shift in species dominance. Selective pressure determined the emergence of new strains for example on Gammaproteobacteria sp. DTU53, providing in depth evidence of functional redundancy within the microbiome.

Modelling the removal efficiency of hydrogen sulfide from biogas in a biofilter using multiple linear regression and support vector machines

The main goal of this study is to create a statistical and intelligent model that can forecast the removal efficiency of hydrogen sulfide (H2S) in a fixed bed biofilter. The majority of conventional models employ mathematical principles that necessitate highly technical infrastructure, extremely detailed information on the biofiltration mechanism, and estimation of model input parameters. However, in this study, Multiple Linear Regression and Support Vector Machine methodology were used to reduce the reliance on experimental data. Experimental research was done to determine the effects of three factors on H2S removal efficiency, including the moisture content of the compost used as the biofilter bed, the empty bed residence time in the reactor, and the H2S concentration in the biogas stream input to the biofilter. Experimental findings demonstrated that the biofilter with a moisture content of 6%, and empty bed residence time of 60 s was capable of removing up to 75% of H2S from a biogas stream with H2S inlet concentration of 70 ppm(v). With a Coefficient of Determination between 0.98 and 0.99, the proposed models show excellent ability to predict the H2S removal efficiency. Compared to a Multiple Linear Regression based model, test results from a Support Vector Machine based model showed better agreement with experimental data.

Optimization and Analysis of a Low-Pressure Water Scrubbing Biogas Upgrading System via the Taguchi and Response Surface Methodology Approaches

Biogas upgrading is essential in order to increase the calorific value and improve the quality of raw biogas. This present study aims at investigating the optimum performance of a near atmospheric pressure water scrubbing (NAPWS) system for biogas upgrading while using both the adsorption and absorption techniques. This was achieved through a two-stage process: namely, the Taguchi approach followed by the response surface methodology (RSM). The Taguchi orthogonal array design consisted of 27 runs where the raw biogas pressure (10 - 30 kPa), liquid flow rates (2.6 - 4.2 l/ min.) and variations of the steel wool height (0 - 45.72 cm) in the adsorption column were experimentally studied with respect to the methane (CH4) yield and removal efficiency of hydrogen sulfide (H2S) and carbon dioxide (CO2). From the experiments, the removal efficiency of hydrogen sulfide was greater than 87% with the average bio-methane content of 77.67%. During the second-stage, the analysis of variance (ANOVA) and the RSM were undertaken for optimization of the process parameters. The optimum bio-methane concentration of 84.71 (%v/v) CH4 and 13.31 (%v/v) CO2 was attained at gas pressure of 14kPa, liquid flow rate of 4.2 l/min., and steel wool height at 22.86cm obtained through numerical optimization. These results revealed that the utilization of the Taguchi and the RSM yielded to the best optimal system performance with the liquid flow rate as the most significant factor

Development of scrubber with nano-TiO2 coated packing for H2S removal

A pilot-scale packed-bed wet scrubber with plastic packing materials was made and experimented to control hydrogen sulfide.TiO2 nanoparticles were coated on the surface of packing to improve the hydrophilicity of scrubbing liquid to form a homogeneous liquid layer on the packing surface. Air flow rate, H2S concentration, and liquid pH were selected to evaluate their effect on scrubber removal efficiency. To evaluate and model the effects of selected variables, two separate sets of experiments were designed and conducted using response surface methodology, central composite design. The former was to model the effects of air flow rate and H2S inlet concentration on removal efficiency at natural liquid pH, and the latter was aimed at total optimization, where all three variables were evaluated. Results showed that TiO2 nanoparticles substantially increased surface hydrophilicity and hydrogen sulfide removal efficiency in natural pH and total optimization by 3.12 % and 3.63 %, respectively. Moreover, air flow rate and H2S concentration had an adverse effect on H2S removal efficiency, while liquid pH positively influenced the efficiency. The optimum removal efficiency for natural pH and total optimizations were 98.83 % and 99.93 %, respectively. The results showed that hydrophilicity of packing materials has a strong effect on hydrogen sulfide removal.

Comparing Hydrogen Sulfide Removal Efficiency in a Field-Scale Digester Using Microaeration and Iron Filters

Biological desulfurization of biogas from a field-scale anaerobic digester in Peru was tested using air injection (microaeration) in separate duplicate vessels and chemical desulfurization using duplicate iron filters to compare hydrogen sulfide (H2S) reduction, feasibility, and cost. Microaeration was tested after biogas retention times of 2 and 4 h after a single injection of ambient air at 2 L/min. The microaeration vessels contained digester sludge to seed sulfur-oxidizing bacteria and facilitate H2S removal. The average H2S removal efficiency using iron filters was 32.91%, with a maximum of 70.21%. The average H2S removal efficiency by iron filters was significantly lower than microaeration after 2 and 4 h retention times (91.5% and 99.8%, respectively). The longer retention time (4 h) resulted in a higher average removal efficiency (99.8%) compared to 2 h (91.5%). The sulfur concentration in the microaeration treatment vessel was 493% higher after 50 days of treatments, indicating that the bacterial community present in the liquid phase of the vessels effectively sequestered the sulfur compounds from the biogas. The H2S removal cost for microaeration (2 h: $29/m3 H2S removed; and 4 h: $27/m3 H2S removed) was an order of magnitude lower than for the iron filter ($382/m3 H2S removed). In the small-scale anaerobic digestion system in Peru, microaeration was more efficient and cost effective for desulfurizing the biogas than the use of iron filters.

Removal of hydrogen sulfide from biogas using activated carbon synthesized from different locally available biomass wastes - a case study from Palestine

ABSTRACT The main aim of this study was to remove hydrogen sulfide (H2S) from biogas by adsorption using synthesized activated carbon prepared using locally available biomass. The effect of the type of precursors, impregnation reagent and bed height was studied in continuous reactors. Three types of biomass wastes (almond shells, eucalyptus and coffee grains) were collected, grinded, sieved, pyrolyzed at 500°C and impregnated with chemical reagents such as potassium hydroxide or zinc chloride. Adsorption tests were performed using a fixed bed filter filled with the produced activated carbon. The highest biochar yield of 36% was obtained eucalyptus followed by almond shells (28.5%) and coffee grains (24%), respectively. The highest adsorption capacity and removal efficiency were obtained with eucalyptus followed by almond shells and coffee grains, respectively. For instance, eucalyptus showed an adsorption capacity of ~690 (mg hydrogen sulfide/g adsorbent) followed by almond (230 mg hydrogen sulfide/g adsorbent) and coffee grains (22 mg hydrogen sulfide/g adsorbent). As an impregnation reagent, potassium hydroxide gave the highest adsorption efficiency and capacity than zinc chloride. Furthermore, the breakthrough time with KOH (180 min) was higher than ZnCl2 (70 min). Increasing the bed height during continuous breakthrough tests increased the adsorption capacity and hydrogen sulfide removal efficiency. The results of this study showed that the adsorption efficiency of the synthesized activated carbon and consequently the hydrogen sulfide removal efficiency could be fine-tuned by selecting an appropriate biomass precursor and proper impregnation reagent.

An efficient method for removing hydrogen sulfide from natural gas using supersonic Laval nozzle

A new method was proposed for hydrogen sulfide removal from natural gas through the utilization of supersonic flow in a Laval nozzle. For this purpose, a mathematical model was established for the supersonic non-equilibrium condensation flow of the binary methane-hydrogen sulfide mixture. The condensation parameters were numerically calculated and described in detail, and a sensitivity analysis was carried out to investigate the influence of the inlet parameters on the supersonic condensation flow. The results show that when the inlet temperature and pressure were 290K and 5MPa respectively, and the mole fraction of hydrogen sulfide was 15%, the removal efficiency of hydrogen sulfide was 64.83%, which indicates that the use of supersonic separation technology for this application is indeed feasible. It was also found that with the decrease of inlet temperature or the increase of inlet pressure, the nucleation site moved forward (i.e. closer to the throat), and the maximum droplet radius and liquid mass fraction of hydrogen sulfide increased. When the mole fraction of hydrogen sulfide was less than 5%, however, the liquid mass fraction of hydrogen sulfide was almost zero. Therefore, it appears that using a reasonable hydrogen sulfide fraction, a lower inlet temperature, and a higher inlet pressure can promote the supersonic condensation of hydrogen sulfide in the Laval nozzle and improve the efficiency of the removal process. These results suggest that supersonic separation technology can provide an efficient and environment-friendly way to remove hydrogen sulfide from natural gas, thereby reducing emissions.

Influence of trickling liquid velocity, low molar ratio of nitrogen/sulfur and gas-liquid flow pattern in anoxic biotrickling filters for biogas desulfurization

Hydrogen sulfide has been successfully removed from biogas using anoxic biotrickling filters but an in-depth study of the main operational variables has not yet been carried out. The effect of (i) the empty bed residence time (32–164 s) at a hydrogen sulfide concentration of 2,000 ppmv, (ii) the inlet hydrogen sulfide concentration (2,000–10,000 ppmv), (iii) the trickling liquid velocity (4.8–20.9 m h−1) and (iv) the feed of low nitrogen/sulfur molar ratio (0.334–0.409 mol N-NO3– mol−1 S-H2S) on the hydrogen sulfide removal efficiency have been studied. The BTF (total packed volume of 2.8 L, height/diameter ratio of 9.8) was filled with polypropylene Pall rings (5/8″) and fed continuously with nitrate and a biogas mimic operating in counter-current and co-current flow modes.The maximum elimination capacity was 282.0 gS-H2S m–3 h–1 (RE 97 ± 0.5%) for counter-current flow and 287.5 gS-H2S m–3 h–1 (RE 99 ± 0.4%) for co-current flow mode for an EBRT of 164 s. In addition, in terms of the nitrogen/sulfur molar ratio a higher elemental sulfur production was found in counter-current flow (97.6 ± 2.0%) when compared to co-current flow (87.6±2.8%) since a better depletion of nitrate occurred in co-current flow mode.Finally, three different nitrogen/sulfur molar ratios (0.4, 1.0 and 1.6 mol N-NO3– mol–1 S-H2S) were compared economically. The low and high ratios would involve a nitrate cost of 0.54 and 2.15 € per kg of treated of S-H2S and an elemental sulfur production of 21.5 metric tons and zero production, respectively.

Hydrogen sulfide removal from biogas using chemical absorption technique in packed column reactors.

The toxicity and corrosion potential of hydrogen sulfide in raw biogas underlines the need for biogas purification. Several techniques available for removal of hydrogen sulfide from biogas are out of the reach for common end users due to lack of knowledge, higher running costs, and insufficient operational skills. The present experimental study aims to propagate hydrogen sulfide removal techniques amongst the end users by using a low-cost chemical absorption technique and packed column reactors. Commercial grade chemicals like monoethanolamine, sodium hydroxide, calcium hydroxide, granular activated carbon, and steel wool were used for biogas purification in packed column reactors of 1.2 liters capacity. Hydrogen sulfide removal efficiency up to 92.41% was achievable using single purification columns. The efficiency achieved by using multiple purification column was up to 96.84%. Hydrogen sulfide removal efficiency was calculated for experimental variants like the use of a dedicated purification column, multiple purification columns, flow variations and pressure variations of raw biogas. The data for the frequency of regeneration/replacement of different chemicals was also determined. The simplicity of operation and the use of low-cost reagents in the present study can enable the use of these methods amongst end users of biogas technology for minimizing health hazards and corrosion problems.

Methane enrichment of biogas produced from floral waste: A potential energy source for rural India

ABSTRACTBiogas has emerged as a clean and cheap energy source with additional advantages like waste disposal solution and an alternative for fossil fuels. Raw biogas contains methane between 50% and 70% and carbon dioxide between 30% and 50%, along with traces of hydrogen sulfide and moisture. Presence of contaminants like carbon dioxide and hydrogen sulfide in biogas restricts its applications in India for cooking and lighting purpose or at the place of its generation. Thus, for making biogas as a transportable fuel or for other widespread applications, removal of contaminants from biogas becomes a necessary step. Small-scale biogas plants seldom use purification and scrubbing systems because of cost considerations and inadequate knowledge of purification techniques. The present experimental work uses floral waste with alkaline pretreatment as an input substrate, for biogas production in Deenbandhu-type fixed-dome biogas plant, used in rural parts of India. The experimental investigation focuses on methane enrichment of biogas by removal of contaminants like carbon dioxide, hydrogen sulfide, and moisture from biogas, using chemical absorption technique. Packed column reactors arranged in series facilitate biogas purification and scrubbing process at around atmospheric pressure and temperature. The materials used for filling the purification columns include steel wool, silica gel, and different aqueous alkaline solutions of sodium hydroxide (NaOH), calcium hydroxide (Ca(OH)2), sodium carbonate (Na2CO3), and monoethanolamine (MEA). A pedal-operated compressor pressurizes raw biogas and forces it through a series of packed chemical absorption columns for the removal of contaminants. Content analysis of purified biogas and raw biogas contents has been done using gas chromatography. The analysis of purified biogas samples 1 and 2 shows methane enrichment up to 96.91% and 94.16% and the carbon dioxide removal efficiency of 99.85% and 98.86% while hydrogen sulfide removal efficiency of 87.5% and 62.5% for samples 1 and 2, respectively. Purification results for biogas show the potential of the purified gas for applications like running stationery engines or use as a vehicular fuel. The purification and scrubbing technique used in the present work uses low-cost commercial chemicals, and the purification columns comprise 4-in-diameter polyvinyl chloride pipes. Use of the technique on a large scale by common people can further raise the potential of biogas as an energy source with a high heating value for widespread applications. Using floral waste from temples as an input substrate provides an energy-efficient solution for soil and water pollution, arising due to the disposal of the waste into the soil or nearby water resources like a river.

Removal of gaseous hydrogen sulfide using Fenton reagent in a spraying reactor

Removal of gaseous hydrogen sulfide using Fenton solution in a spraying tower was studied systematically. The effects of several key running parameters such as H2O2 concentration, Fe2+ concentration, reaction temperature, solution pH value, hydrogen sulfide concentration and liquid-gas ratio on hydrogen sulfide removal were investigated. Products, free radicals and mechanism of hydrogen sulfide removal were also studied. The results show that an increase in Fe2+ concentration, liquid-gas ratio or solution pH value can increase removal efficiency of hydrogen sulfide. Increasing hydrogen sulfide concentration can reduce removal efficiency of hydrogen sulfide. H2O2 concentration and reaction temperature have double influence on hydrogen sulfide removal removal efficiency. Hydrogen sulfide removal by oxidation of hydroxyl radical (OH) is the main removal pathways. Hydrogen sulfide removal by oxidation of H2O2 and hydrolysis reaction are the secondary removal pathways. The main oxidation products of hydrogen sulfide removal are sulphuric acid and elemental sulfur in solutions.

Comparative study on the removal efficiency of hydrogen sulfide (H2S) using three different packings

ABSTRACTTo improve the removal efficiency on hydrogen sulfide (H2S), a biofilter was developed and was made of polyvinyl chloride (PVC) pipes. The effects of three different packings (i.e., packing A, packing B, and packing C), containing different proportions of activated carbon, sawdust, wormcast, perlite, and pig manure compost, based on different biofilter parameters on H2S removal efficiency, were investigated. With the extension of running time, the H2S removal rate of packing A reached up to 90.12%, that of packing B reached a peak at 92.96%, and that of packing C was highest at 87.21%. The contribution rate of each packing at the bottom of the device was significantly greater (p < 0.01) than that of other parts, and those of the top of the devices were all greater than those of the middle of the devices. The H2S removal rate increased with greater filler layer height. The removal rate of group B increased first with humidity, and then declined, with the optimal humidity level for the removal of H2S 50–65% in this study. With the prolongation of the run, the pH of packing A was reduced from 7.1 to 5.91, while the pH of packing B and C remained within the range of 6.53–7.10. An increase was found in the number of bacteria and fungi over time. The count of bacteria in packing B and C and following a decreasing order was bottom > middle > top, whereas that for fungi was the opposite. In conclusion, it is thought that packing B (comprising wormcast + sawdust + activated carbon) is more efficient in the removal of H2S than the other packings and may thus be utilized in biofilters. These results hope to provide useful information for future related research on the removal efficiency of H2S using packings.Implications: Wormcasts use as biological filter packing to remove H2S is limited and needs yet to be explored. A comparative study on the removal efficiency of H2S using three packings showed the packings that included wormcast were more efficient than others, and showed the combined features of physical absorption and biological removal with long sustainability and good efficiency, although these were largely influenced by environmental factors and nutrient content for the microorganisms. In summary, wormcast could be utilized in biological filters in the future in related research beacuse of its good efficiency and low cost.

Influence of non-wetting, partial wetting and complete wetting modes of operation on hydrogen sulfide removal utilizing monoethanolamine absorbent in hollow fiber membrane contactor

Hydrogen sulfide is a highly poisonous acidic gas which is regarded as one of the major causes of corrosion and odorous problems. For this reason, the efficient separation of hydrogen sulfide from various gaseous streams is mandatory. This paper aims to evaluate the removal of hydrogen sulfide pollutant from hydrogen sulfide/methane gaseous flow using monoethanolamine liquid absorbent inside the hollow fiber membrane contactor. As the novelty, a mechanistic modelling and a two dimensional numerical simulation are developed under non-wetting (0% wetting of membrane pores), partial wetting (50% wetting of membrane pores) and complete wetting (100% wetting of membrane pores) modes of operation to predict the effects of various operational parameters such as module length, tortuosity and porosity of membrane, initial concentrations of hydrogen sulfide and monoethanolamine on the removal of hydrogen sulfide. The results of mechanistic model prediction under non-wetting mode are in an excellent agreement with the experimental data with average absolute relative error less than 5%. On the basis of the results, monoethanolamine provides the highest hydrogen sulfide sequestration while being used under non-wetting mode of operation in comparison with partial wetting and complete wetting conditions. Membrane pore wettability has a detrimental influence on the removal efficiency of hydrogen sulfide due to creating a considerable mass transfer resistance along the way of hydrogen sulfide gas transport inside the membrane contactor.

Identification of a yeast strain able to oxidize and remove sulfide high efficiently.

Hydrogen sulfide is a common odor gas of volatile sulfur-containing compound. The emission of hydrogen sulfide in the waste gas from industrial processing and agricultural operations could cause air pollution to the surrounding environment. The aim of this study was screening and isolation of wild yeast strains from the sludge of sewage pool in the fishmeal processing plant to remove hydrogen sulfide odor. A yeast strain ZJY-7 was obtained. Its hydrogen sulfide removal efficiency was 97.1%. The morphology studies were investigated using microscope and scanning electron microscope. The yeast isolate was then identified by biochemical tests using API 20 C AUX strip and sequencing 26S rDNA genes. Both biochemical tests analysis and the molecular identification indicated that the yeast isolate ZJY-7 was Candida tropicalis ZJY-7. The NCBI GenBank accession number is KX259479. Batch tests showed that the yeast strain tolerated up to 300mg/l of dissolved S2- concentration. The yeast also tolerated a wide pH range (2.5-9.0). The optimal initial sulfide concentration of C. tropicalis ZJY-7 on sulfide oxidation and sulfate generation was 200mg/l, and at initial pH value 6. The highest accumulated sulfate was 91.8mg/l at 48h. These results broadened the range of sulfide-oxidizing organism and new application of C. tropicalis on the control of hydrogen sulfide odor pollution. The yeast may have potential to be used in bioreactor for removal of hydrogen sulfide gas.

The use of ozone in a continuous cyclical swing mode regeneration of Fe-EDTA for a clean biogas process from a swine farm waste

Hydrogen sulfide in biogas causes environmental problem such as acid rain, therefore several methods are employed in the process to eliminate hydrogen sulfide in biogas. A process for hydrogen sulfide removal in clean biogas production has been examined at a swine farm. Ferric chloride – Ethylenediaminetetraacetic acid solution was used to oxidize hydrogen sulfide to elemental sulfur and ozone was used in the regeneration of ferrous ion to ferric ion. The experiments were conducted using 2 bubbling columns with the same diameter and height, which were 52 mm and 610 mm, respectively. The process was run in a continuous cyclical swing mode. The flow rate of biogas was fixed at of 0.5 L/min and hydrogen sulfide concentrations in the biogas were in the range of 4000–5000 ppm. The initial pH of the Ferric chloride – Ethylenediaminetetraacetic acid solution was varied from 6.5 to 9. Experimental results in the hydrogen sulfide removal part, indicated that Ferric chloride – Ethylenediaminetetraacetic acid solution achieved a maximum 99.5% hydrogen sulfide removal efficiency at pH 8, with a criteria that hydrogen sulfide in the biogas must be less than 100 ppm. In the regeneration part, the regeneration of ferric ion from ferrous ion using ozone in air stream was successfully obtained. The regeneration of ferric ion from ferrous ion was completed within 10 min and the pH turned to pH 8. The regenerated Ferric chloride – Ethylenediaminetetraacetic acid solution was reused several times and still showed high ability for hydrogen sulfide removal. The key parameter, that had to be monitored, was pH, which was relevant to ferrous precipitation. The goal of the process was achieved since hydrogen sulfide was reduced to not exceed 100 ppm, without altered methane concentration in the biogas. Ozone was successfully applied in a continuous cyclical swing mode for the first time in the hydrogen sulfide removal in the biogas production.

In situ Removal of Hydrogen Sulfide During Biogas Fermentation at Microaerobic Condition.

In this paper, rice straw was used as a raw material to produce biogas by anaerobic batch fermentation at 35°C (mesophilic) or 55°C (thermophilic). The hydrogen sulfide in biogas can be converted to S0 or sulfate and removed in-situ under micro-oxygen environment. Trace oxygen was conducted to the anaerobic fermentation tank in amount of 0.5, 1.0, 2.0, 3.0, 4.0, 5.0, or 10.0 times stoichiometric equivalence, respectively, and the control experiment without oxygen addition was carried out. The results showed that the initial H2S concentrations of biogas are about 3235 ± 185mg/m3 (mesophilic) or 3394 ± 126mg/m3 (thermophilic), respectively. The desulfurization efficiency is 72.3% (mesophilic) or 65.6% (thermophilic), respectively, with oxygen addition by stoichiometric relation. When the oxygen feeded in amount of 2∼4 times, theoretical quantity demanded the removal efficiency of hydrogen sulfide could be over 92%, and the oxygen residue in biogas could be maintained less than 0.5%, which fit the requirement of biogas used as vehicle fuel or combined to the grid. Though further more oxygen addition could promote the removal efficiency of hydrogen sulfide (about 93.6%), the oxygen residue in biogas would be higher than the application limit concentration (0.5%). Whether mesophilic or thermophilic fermentation with the extra addition of oxygen, there were no obvious changes in the gas production and methane concentration. In conclusion, in-situ desulfurization can be achieved in the anaerobic methane fermentation system under micro-oxygen environment. In addition, air could be used as a substitute oxygen resource on the situation without strict demand for the methane content of biogas.

Nonaqueous System of Iron-Based Ionic Liquid and DMF for the Oxidation of Hydrogen Sulfide and Regeneration by Electrolysis.

To improve the hydrogen sulfide removal efficiency with the application of an iron-based imidazolium chloride ionic liquid (Fe(III)-IL) as desulfurizer, Fe(II) and N,N-dimethylformamide (DMF) are introduced to Fe(III)-IL to construct a new nonaqueous desulfurization system (Fe(III/II)-IL/DMF). Following desulfurization, the system can be regenerated using the controlled-potential electrolysis method. The addition of Fe(II) in Fe(III)-IL is beneficial for the hydrogen sulfide removal and the electrochemical regeneration of the desulfurizer. The addition of DMF in Fe(III/II)-IL does not change the structure of Fe(III/II)-IL but clearly decreases the acidity, increases the electrolytic current, and decreases the stability of the Fe-Cl bond in Fe(III/II)-IL. Fe(III/II)-IL/DMF can remove hydrogen sulfide and can be regenerated through an electrochemical method more efficiently than can Fe(III/II)-IL. After six cycles, the desulfurization efficiency remains higher than 98%, and the average conversion rate of Fe(II) is essentially unchanged. No sulfur peroxidation occurs, and the system remains stable. Therefore, this new nonaqueous system has considerable potential for removing H2S in pollution control applications.

Estimation of hydrogen sulfide removal efficiency with granulated coal ash applied to eutrophic marine sediment using a simplified simulation model

Hydrogen sulfide generated in eutrophic marine sediment is harmful for living organisms. It is therefore necessary to remove hydrogen sulfide from the sediment to restore benthic ecosystems. Previous studies revealed that granulated coal ash, which is a by-product of coal thermal electric power stations, could remove and oxidize hydrogen sulfide. In this study, we propose a simplified simulation model to estimate the hydrogen sulfide removal efficiency of granulated coal ash. Hydrogen sulfide concentrations in eutrophic marine sediment pore water with and without the application of granulated coal ash were calculated by the proposed model, and the outputs were compared with semi-field or field observation data. The model outputs reproduced the observed data well. Using the proposed model outputs, we suggest an optimum application dosage of granulated coal ash for remediating eutrophic marine sediment.

킬레이트 착화학반응에 의한 음식물폐기물 혐기소화가스 중 황화수소의 제거와 황회수 및 경제성평가

Several experiments have been done to investigate the removal of hydrogen sulfide (H2S) synthetic gas from biogas streams by means of chemical absorption and chemical reaction with 0.1-1 M Fe/EDTA solution. The roles of Fe/EDTA were studied to enhance the removal efficiency of hydrogen sulfide because of oxidizing by chelate. The motivation of this investigation is first to explore the feasibility of enhancing the toxic gas treatment in the biogas facility. The biogas purification strategy affords many advantages. For instance, the process can be performed under mild environmental conditions and at low temperature, and it removes hydrogen sulfide selectively. The end product of separation is elemental sulfur, which is a stable material that can be easily disposed with minor potential for further pollution. As the Fe-EDTA concentration increased, the conversion rate of hydrogen sulfide increased because of the high stability of Fe-EDTA complex. pH as an important environmental factor was 9.0 for the stability of chemical complex in the oxidation of hydrogen sulfide.

Development of a two-phase bioreactor for the biological removal of hydrogen sulfide from biogas

In this study, a two-phase bioreactor, consisting of an anaerobic absorption column and an aerobic biofilter, was constructed and utilized to determine the removal efficiency of high strength hydrogen sulfide from biogas. A microbial strain of sulfur oxidizing bacteria (SOB), Acidithiobacillus thiooxidans, isolated from earthworm casts was inoculated in the aerobic biofilter. Initially, an inlet concentration of hydrogen sulfide supplied to the two-phase bioreactor was 180ppm, and overall removal efficiencies of hydrogen sulfide were 30 to 60% due to low cell density and activity of the SOB in the bioreactor. As bioreactor operation continued, microbial activity and bioreactor performance increased with sharply decreasing pH levels from 6.3 to 1.5. During the same operational period, the optical density (OD600) increased from 0.05 to 0.4, indicating that the SOB was in an experiential growth stage at the low pH condition. The overall removal efficiency of hydrogen sulfide was found to be greater than 97% from day 8, and the high removal efficiency maintained. On day 30, the inlet concentration of hydrogen sulfide was increased to 400ppm, and the removal efficiency did not decline, showing that the activity of the SOB was high enough to handle the high loading rate of hydrogen sulfide. An interesting finding of the study was that the activity of the SOB strain used in this study was not affected at the extremely low pH values, and no chemical additives were required to maintain the pH. Dissolved oxygen concentrations in the anaerobic column and the aerobic biofilter were maintained at 2 and 8mg/L, respectively. Consequently, the two-phase bioreactor showed advantages over conventional biofilters for the treatment of high strength hydrogen sulfide from biogas.