H2S Adsorption Capacity Research Articles

Novel Amine Modified Nanoporous SBA-15 Sorbent for the Removal of H2S from Gas Streams in the Presence of CH4

A new sorbent has been developed by grafting Hexamethylenetetramine on a mesoporous molecular sieve (SBA-15) by wet impregnation method. This sorbent (Hexamine/SBA-15) has been characterized using N2 physisorption, X-ray diffraction (XRD) at low angles (2θ°) and FT-IR. To investigate the H2S removal capacity of this adsorbent from 9000 ppm H 2S balance CH4-containing gas mixtures, the breakthrough tests have been performed on a fixed-bed flow system. SBA-15 without amine loading showed a very low H2S adsorption capacity (0.015 mmol-Sulfur/g-sorbent) and saturation capacity (0.032 mmol-Sulfur/gsorbent). The results show that after the amine loading, hexamine is dispersed inside the mesochannels of mesoporous SBA-15. Effects of the amine loading and sorption temperature on the sorption behavior of this developed sorbent have also been studied. Increase of amine loading enhances the H 2S sorption on this sorbent, When Hexamine was 50wt%, the removal performance was optimum(qb= 0.9 mmol/gsorbent).With increase in temperature, both the breakthrough capacity (qb) and the saturation capacity (qs) decrease. High sorption capacity is observed at low temperature (T=22℃, qs= 1.9 mmol/g-sorbent) which provides a promoting effect in removal of H 2S from gas mixtures streams on the developed Hexamine/SBA-15 sorbent. This developed sorbent is regenerated easily at 100°C, and shows very good stability. The breakthrough capacity decreased from 0.9 mmol. g -1 for the first cycle to 0.75 mmol g -1 for the second cycle and 0.74 mmol g -1 for the third cycle. Although the breakthrough capacity decreased about 83 % of the first breakthrough tim, H2S can be recovered.

Iron Oxide/Polymer‐Based Nanocomposite Material for Hydrogen Sulfide Adsorption Applications

AbstractThe processing of iron oxide nanoparticles derived from spray flame synthesis for specific adsorption applications is described. After the as‐prepared particles proved the ability for H2S removal in pure gas treatment, two different nanoparticle‐based composite materials were prepared. While impregnation of activated carbon with the as‐prepared nanoparticles showed the expected increase in H2S adsorption capacities, a significant enhancement in desulfurization performance was observed for a novel iron oxide nanoparticle composite material. H2S adsorption was tested in fixed‐bed breakthrough curve measurements. The H2S removal efficiency of the novel material under ambient conditions indicates highly promising properties for potential use in industrial and air pollution control applications.

Zinc (hydr)oxide/graphite oxide/AuNPs composites: Role of surface features in H2S reactive adsorption

Zinc hydroxide/graphite oxide/AuNPs composites with various levels of complexity were synthesized using an in situ precipitation method. Then they were used as H2S adsorbents in visible light. The materials’ surfaces were characterized before and after H2S adsorption by various physical and chemical methods (XRD, FTIR, thermal analysis, potentiometric titration, adsorption of nitrogen and SEM/EDX). Significant differences in surface features and synergistic effects were found depending on the materials’ composition. Addition of graphite oxide and the deposition of gold nanoparticles resulted in a marked increase in the adsorption capacity in comparison with that on the zinc hydroxide and zinc hydroxide/AuNP. Addition of AuNPs to zinc hydroxide led to a crystalline ZnO/AuNP composite while the zinc hydroxide/graphite oxide/AuNP composite was amorphous. The ZnOH/GO/AuNPs composite exhibited the greatest H2S adsorption capacity due to the increased number of OH terminal groups and the conductive properties of GO that facilitated the electron transfer and consequently the formation of superoxide ions promoting oxidation of hydrogen sulfide. AuNPs present in the composite increased the conductivity, helped with electron transfer to oxygen, and prevented the fast recombination of the electrons and holes.

Dye Adsorption on Inorganic Matrices as a New Strategy to Gas Capture: Hydrogen Sulfide Adsorption on Rodhamine B Modified Kaolinite

In this communication, the synthesis, characterization, and hydrogen sulfide (H2S) adsorption of Rhodamine B modified kaolinite are reported. The modified matrices were prepared by a cation exchange process. The pure and modified matrices were characterized by X-ray diffractometry, FTIR-spectroscopy, and thermogravimetry. The total amount of adsorbed H2S (gravimetric data) can be described as: pure kaolinite (2.6 mg/g) and Rodhamine B modified kaolinite (10.1 mg/g). So, the H2S adsorption capacity of kaolinite is increased by almost 300% by Rhodamine B modification.

Effects of humidity, O2, and CO2 on H2S adsorption onto upgraded and KOH impregnated activated carbons

In the present work, low grade activated carbon was upgraded by steam activation to improve its surface properties and further impregnated with potassium hydroxide (KOH) to promote the H2S chemisorption for desulfurization applications. The H2S adsorption performance of these prepared samples was tested at ambient temperature under various operating conditions i.e. in the presence of isolated and integrated relative humidity (70%), O2 (2%), and CO2 (40%). It was found that the KOH impregnated activated carbons provide significantly higher H2S adsorption capacity and breakthrough time than the non-impregnated sample. Importantly, the presence of O2 in the gas stream greatly increases the breakthrough time of H2S adsorption, while the presence of humidity significantly increases the H2S adsorption capacity; these positive effects are related to the promotion of H2S oxidation to elemental sulfur and H2S dissociation. In contrast, the presence of CO2 strongly inhibited H2S adsorption due to competitive adsorption and reaction between CO2 and H2S, particularly for the KOH impregnated samples. Nevertheless, it was revealed from the study that the presence of O2 and humidity along with CO2 can efficiently minimize this negative effect; therefore, this highlights the importance of O2 and humidity addition for biogas purification.

Simultaneous Removal of Toluene (Model Tar), NH3, and H2S, from Biomass-Generated Producer Gas Using Biochar-Based and Mixed-Metal Oxide Catalysts

Effectiveness of four catalysts (biochar, activated carbon, acidic surface activated carbon, and mixed metal oxide) was studied for simultaneous removal of toluene, NH3, and H2S from biomass-generated producer gas. NH3 (0.03%), H2S (0.015%), and toluene at a flow rate of 2 mL/h were mixed with a synthetic producer gas composition (H2: 8.5%, N2: 58%, CO: 17%, CH4: 2%, and CO2: 11%) and passed over a catalyst bed in a fixed-bed reactor tube maintained at 800 °C. Results indicate that simultaneous removal of contaminants from producer gas is feasible using biochar-based catalysts. High surface area mixed metal oxides synthesized using microwave and ultrasonication were also effective for simultaneous removal of contaminants. Among the four catalysts, acidic surface activated carbon resulted in the highest toluene removal efficiency of 97.5% and highest breakthrough time of 145 min for NH3. For H2S removal, mixed metal oxides resulted in the highest breakthrough time of 105 min. For simultaneous removal of toluene, H2S and NH3, activated carbon showed good removal capacity (91% toluene removal efficiency; NH3 adsorption capacity of 0.03g-NH3/g-activated carbon; H2S adsorption capacity of 0.008 g-H2S/g-activated carbon), whereas biochar had moderate removal capacity (86% toluene removal efficiency; NH3 adsorption capacity of 0.008 g-NH3/g-biochar; H2S adsorption capacity of 0.008 g-H2S/g-biochar).

Effect of KI and KOH Impregnations over Activated Carbon on H2S Adsorption Performance at Low and High Temperatures

In the present work, commercial-grade activated carbon was modified by steam activation to improve its surface properties for high temperature desulfurization. The modified sample was also further upgraded by impregnating with KOH and KI to promote the chemisorption with of H2S. The H2S adsorption performance was tested under the temperature range of 30–550°C using the temperature program adsorption technique to understand the effect of adsorption temperature on the material adsorption characteristic. It was found that at ambient temperature, the impregnation of activated carbon with KOH can promote the H2S adsorption capacity of activated carbon, whereas the impregnation with KI does not provide a significant beneficial effect. At high adsorption temperature (upto 550°C), both KOH and KI impregnation considerably improve the H2S adsorption performance of activated carbon in terms of the adsorption capacity and breakthrough time. It was revealed from N2 adsorption, SEM and EDS measurement that the chemical reactions between H2S and alkaline compounds (KOH and KI) are promoted at high temperature. Based on all experimental results, the equilibrium adsorption model using the linear isotherm was developed to predict the adsorption behavior of these sorbents in terms of equilibrium isotherm constant and mass transfer coefficient for later scaling-up process.

PERFORMANCE OF SODIUM-IMPREGNATED ACTIVATED CARBONS TOWARD LOW AND HIGH TEMPERATURE H2S ADSORPTION

In the present work, the H2S adsorption performance of several activated carbon–based sorbents was studied using the temperature program adsorption technique under the temperature range of 30°–550°C. The activated carbons applied in this study include (i) commercial-grade activated carbon, (ii) the commercial-grade activated carbon modified by steam activation to enhance higher specific surface area, and (iii) the activated carbon impregnated with alkaline compounds (i.e., NaOH and Na2CO3). It was found that the impregnation of activated carbon with NaOH and Na2CO3 can efficiently promote the H2S adsorption capacity of activated carbon in the range of temperatures studied. At 30°C, the Na2CO3-impregnated sample showed better adsorption capacity than the NaOH-impregnated sample, whereas their adsorption performance was almost identical at higher adsorption temperatures. Interestingly, although the activated carbon modified by steam activation showed better surface properties than commercial-grade activated carbon, its H2S adsorption capacities were relatively lower. This could be due to the loss of potassium from activated carbon during the modification by steam activation.

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.

Effectiveness and mechanisms of hydrogen sulfide adsorption by camphor-derived biochar

The characteristics and mechanisms of hydrogen sulfide (H2S) adsorption on a biochar through pyrolysis at various temperatures (100 to 500°C) were investigated. The biochar used in the current study was derived from the camphor tree (Cinnamomum camphora). The samples were ground and sieved to produce particle sizes of 0.4 mm to 1.25 mm, 0.3 mm to 0.4 mm, and <0.3 mm. The H2S breakthrough capacity was measured using a laboratory-designed test. The surface properties of the biochar were characterized using pH and Fourier-transform infrared spectroscopy (FTIR) analysis. The results obtained demonstrate that all camphor-derived biochars were effective in H2S sorption. Certain threshold ranges of the pyrolysis temperature and surface pH were observed, which, when exceeded, have dramatic effects on the H2S adsorption capacity. The sorption capacity ranged from 1.2 mg/g to 121.4 mg/g. The biochar with 0.3 mm to 0.4 mm particle size possesses a maximum sorption capacity at 400°C. The pH and FTIR analysis results showed that carboxylic and hydroxide radical groups were responsible for H2S sorption. These observations will be helpful in designing biochar as engineered sorbents for the removal of H2S. Implications: This paper studies the potential of biochar derived by camphor to adsorb hydrogen sulfide at environmentally sustainable temperatures. The different sizes of the biochars and the different temperatures of pyrolysis for the camphor particle have a great impact on adsorption of hydrogen sulfide.

Preparation of ZnO/SiO2 gel composites and their performance of H2S removal at room temperature

ZnO/SiO2 gel composites with different active component loading were prepared by sol–gel method combined with ambient drying process, followed by thermal treatment. The gel composites were characterized by scanning electron microscopy (SEM), nitrogen adsorption, X-ray diffraction (XRD), FTIR and X-ray photoelectron spectroscopy (XPS), and their performances for H2S removal were evaluated by dynamic testing at room temperature. The as prepared materials exhibited high surface area with multimodal pore size distributions in micropore and mesopore region. The porous properties were significantly influenced both by the ZnO loading ratio and the treated temperature. The gel composites showed a high performance for H2S removal, with the highest H2S adsorption capacity of 96.4mg/g for the sample treated at 400°C with 30wt% ZnO. Both physisorption and the active phase reactivation governed the H2S removal process. It needs to optimize the composites’ porous structure and active component loading amount.

Characterization of adsorption removal of hydrogen sulfide by waste biocover soil, an alternative landfill cover

Landfill is an important anthropogenic source of odorous gases. In this work, the adsorption characteristics of H2S on waste biocover soil, an alternative landfill cover, were investigated. The results showed that the adsorption capacity of H2S increased with the reduction of particle size, the increase of pH value and water content of waste biocover soil. The optimal composition of waste biocover soil, in regard to operation cost and H2S removal performance, was original pH value, water content of 40% (w/w) and particle size of ≤4mm. A net increase was observed in the adsorption capacity of H2S with temperatures in the range of 4–35°C. The adsorption capacity of H2S on waste biocover soil with optimal composition reached the maximum value of 60±1mg/kg at oxygen concentration of 10% (v/v). When H2S concentration was about 5% (v/v), the adsorption capacity was near saturation, maintaining at 383±40mg/kg. Among the four experimental soils, the highest adsorption capacity of H2S was observed on waste biocover soil, followed by landfill cover soil, mulberry soil, and sand soil, which was only 9.8% of that of waste biocover soil.

Removal of Carbonyl Sulfide Using Activated Carbon Adsorption

Wastewater treatment plant odors are caused by compounds such as hydrogen sulfide (H2S), methyl mercaptans, and carbonyl sulfide (COS). One of the most efficient odor control processes is activated carbon adsorption; however, very few studies have been conducted on COS adsorption. COS is not only an odor causing compound but is also listed in the Clean Air Act as a hazardous air pollutant. Objectives of this study were to determine the following: (1) the adsorption capacity of 3 different carbons for COS removal; (2) the impact of relative humidity (RH) on COS adsorption; (3) the extent of competitive adsorption of COS in the presence of H2S; and (4) whether ammonia injection would increase COS adsorption capacity. Vapor phase react (VPR; reactivated), BPL (bituminous coal-based), and Centaur (physically modified to enhance H2S adsorption) carbons manufactured by Calgon Carbon Corp. were tested in three laboratory-scale columns, 6 in. in depth and 1 in. in diameter. Inlet COS concentrations varied from 35 to 49 ppmv (86–120 mg/m3). RHs of 17%, 30%, 50%, and 90% were tested. For competitive adsorption studies, H2S was tested at 60 ppmv, with COS at 30 ppmv. COS, RH, H2S, and ammonia concentrations were measured using an International Sensor Technology Model IQ-350 solid state sensor, Cole-Parmer humidity stick, Interscan Corp. 1000 series portable analyzer, and Drager Accuro ammonia sensor, respectively. It was found that the adsorption capacity of Centaur carbon for COS was higher than the other two carbons, regardless of RH. As humidity increased, the percentage of decrease in adsorption capacity of Centaur carbon, however, was greater than the other two carbons. The carbon adsorption capacity for COS decreased in proportion to the percentage of H2S in the gas stream. More adsorption sites appear to be available to H2S, a smaller molecule. Ammonia, which has been found to increase H2S adsorption capacity, did not increase the capacity for COS.

Studies on H2S Adsorption and Carbon Deposition over Mo-Ni/Al2O3 Catalysts

The influence of molybdenum on the CO2 reforming of methane, simultaneous sulphur poisoning and carbon formation over alumina-supported Ni catalysts was studied. A series of Ni/Al2O3 catalysts modified by Mo was prepared to enable the effect of molybdenum content on H2S adsorption and the catalytic properties of the solids to be studied. The atomic Mo/Ni ratio in such catalysts varied in the range 0.01–1.00 while the Ni content was maintained constant at 3.3%. The catalysts were characterized by TPR, hydrogen adsorption and TEM methods. The H2S adsorption capacities of the catalysts were determined at 923 K employing a mixture consisting of 50 ppm H2S in a hydrogen stream. The results obtained indicate that the Mo promoter had a very favourable influence on the sulphur resistance of the Ni-based catalyst and led to a reduction in the rate of carbon deposition and the formation of graphitic species over the same.

Adsorption Characteristics of Alkaline Activated Carbon Exemplified by Water Vapor, H2S, and CH3SH Gas

Activated carbon adsorption is an widely used process in environmental engineering. Alkaline impregnated activated carbon has been used to enhance the adsorption capacity for odorous compounds from gas streams. This study investigated the physicochemical and adsorption characteristics of one virgin and four alkaline-impregnated activated carbon samples. The four alkaline additives were NaOH, Na2CO3, KOH, and K2CO3 and the impregnated activated carbons were referred to as NaOH-IAC, Na2CO3-IAC, and KOH-IAC, K2CO3-IAC. The specific surface area, micropore area, and micropore volumes were reduced in the impregnated activated carbon systems. The adsorption capacity of H2S and CH3SH increased. This indicated that the physical properties were not the predominant influence on adsorption behavior. The impregnated activated carbons were ranked NaOH Na2CO3 KOH K2CO3 for H2S adsorption. The NaOH-IAC demonstrated 3.2 and 2.2 times the adsorption capacity for H2S and CH3SH, respectively, compared to the virgin AC sample. Increasing the vacuum and immersion duration increased the alkaline quantity of NaOH impregnated on activated carbon. The NaOH-IAC50 (50 mg NaOH/g carbon) sample performed the best. It had 6.9 times the adsorption capacity of the virgin AC. The humidity that coexisted in the H2S and CH3SH gas streams enhanced the H2S and CH3SH adsorption capacity of NaOH-IAC. At 50% relative humidity and 50 ppm H2S, the NaOH-IAC sample exhibited the maximum adsorption capacity for H2S. This carbon attained 30.3 times more capacity than the virgin AC.

Vapor adsorption on coal- and wood-based chemically activated carbons: (III) NH3 and H2S adsorption in the low relative pressure range

NH3 and H2S adsorption studies on coal- and wood-based chemically activated carbons were carried out at room temperature using a gravimetric adsorption technique. The adsorption capacity of NH3 and H2S in the very low relative pressure range was independent of the surface area development. Activated carbons with lower surface area generally adsorbed more of these vapors than those with higher surface area. This can be attributed to the presence of smaller average micropore sizes and a greater number of active adsorption sites on the low surface area chemically activated carbons.

Development of adsorbent/catalyst from municipal wastewater sludge

The objective of this research work is to investigate the possibility of using sewage sludge as a source to produce adsorbent for odorous gas removal. The basic method of adsorbent preparation is pyrolysis in nitrogen gas. The effects of heating temperature and resident time are investigated. Treatments such as drying in air at low temperature and soaking in chemicals prior to pyrolysis are attempted. The prepared adsorbents are characterized by an automatic surface area porosimeter in terms of BET surface area, pore size distribution. The highest BET surface area achieved is 309 m2/g, where the sludge is soaked in 5M zinc chloride solution and dried at low temperature before heating to 650°C for two hours. Laboratory tests at 17.5 ppm H2S concentration show that the sludge-derived adsorbent has an H2S adsorption capacity 25% that of a commercial activated carbon (Calgon IVP 4×6) over 15 hours of duration.

Development of adsorbent/catalyst from municipal wastewater sludge

The objective of this research work is to investigate the possibility of using sewage sludge as a source to produce adsorbent for odorous gas removal. The basic method of adsorbent preparation is pyrolysis in nitrogen gas. The effects of heating temperature and resident time are investigated. Treatments such as drying in air at low temperature and soaking in chemicals prior to pyrolysis are attempted. The prepared adsorbents are characterized by an automatic surface area porosimeter in terms of BET surface area, pore size distribution. The highest BET surface area achieved is 309 m2/g, where the sludge is soaked in 5M zinc chloride solution and dried at low temperature before heating to 650°C for two hours. Laboratory tests at 17.5 ppm H2S concentration show that the sludge-derived adsorbent has an H2S adsorption capacity 25% that of a commercial activated carbon (Calgon IVP 4x6) over 15 hours of duration.

Comparison of field and laboratory H2S adsorption capacity of activated carbon

A comparison study on fixed-bed H2S adsorption capacity of a commercial activated carbon both in the laboratory and in the field was conducted. Pure H2S gas at an inlet concentration of 10 000 ppm was used for the laboratory test, while the field activated carbon was subjected to adsorption of sewage gas with H2S concentrations ranging from 0.1 to 28 ppm with an average concentration of 5.3 ppm. The carbons were tested under gas/carbon contact times of 1, 2, 3, and 4 s. Based on the results obtained at a carbon/gas contact time of 3 s and a H2S breakthrough concentration of 1 ppm, the H2S adsorption capacity of the field activated carbon was found to be only 30% of that in the laboratory. It is possible that the adsorption of other sewage volatiles has resulted in a significant decrease in the activated carbon's H2S removal efficiency.