H2S Uptake Research Articles

Reactive regeneration in novel hybrid solvent: Achieving dual objectives of H2S conversion and absorbent regeneration

In this work, we developed a composite solution (FILs/DFP) using ionic liquids (FILs) and 4-formylmorpholine (DFP) for natural gas desulfurization. Among these, [TND-C][Tf2N]/DFP exhibited an impressive H2S uptake of 3.65 mol/mol and H2S/CO2 selectivity of 25 at 30 °C and 1 bar. The 1H NMR, FTIR, and DFT calculations revealed that the dense hydrogen bonding network and the active sites of tertiary amines in FILs/DFP were the main factors for the efficient uptake of H2S. Furthermore, we propose a viable reaction regeneration strategy at room temperature, successfully addressing the challenges of absorber regeneration, the catalytic activity of the FILs remained above 95 % even after six cycles. Overall, this strategy eliminates the high energy losses of H2S desorption and allows for the recycling of FILs with minimal energy consumption. This simultaneously achieving dual objectives of H2S conversion and absorbent regeneration process shows promising applications in natural gas desulphurization.

Solar-assisted approach for the synthesis of nanoadsorbents for biogas desulfurization using wastes

Minimizing food wastes and finding a second life use for industrial residuals have become some of the top priorities of modern society. This work considers the use of spent eggs and mussels shells, as well as marble dust, as raw sources to develop nanoparticles involving renewable resources in both their preparation and adoption in technological applications. Specifically, Ca/Mg-based nanoparticles were obtained by evaporating such wastes in a physical vapor deposition system using concentrated solar beam and explored as high capacity H2S adsorbents for the purification of biogas. The evaluation of their uptake performance in a fixed-bed configuration indicates that the formation of a thick layer of Ca(OH)2 on very small nanoparticles (<70 nm) inhibits H2S uptake, whereas the presence of Mg phases (dolomite) favors its potentiation. Importantly, the co-evaporation of iron provides an extra amplification of the absorption capacity due to the synergy of the Ca/Mg neutralizing character and the affinity of Fe for sulfur. In the best case, the nanoparticles obtained from mussels and 10 %wt. Fe reached an uptake capacity of 0.92 mg/g. This high yield is attributed to the formation of oxides, such as Ca2Fe2O5, that allow a sulfide to sulfate oxidation-adsorption mechanism.

Enhanced H2S removal from diverse fuels by a coupled absorption and biological process uses CO2 as carbon resource for microbial ecosystem

Physico-chemical methods for H2S removal are costly due to their complex recovery. However, biological processes require carbon source and benign operation for safe H2S removal. Herein, absorption and biological processes were coupled to convert H2S/CO2 into sulfur fertilizer rapidly. Metallic-doped zeolitic imidazolate framework-8 (ZIF-8) was used to absorb H2S & CO2 in the adsorption column, and microbial nutrients solution to desorb/carry H2S/CO2 and feed it into the biological process, with the core aim to the develop rapid H2S/CO2 utilizing microbial ecosystem. The system consisted of adsorption, biological and separation processes. The adsorption system comprised (i) Cu-Zn-ZIF-8@FPUF responsible for H2S absorption and (ii) a specially designed microbial-media solution to desorb/carry absorbed H2S/CO2 stream into the biological process. The biological process was composed of aerobic, anaerobic, and facultative microbial groups, sequentially developing a high-performance microbial ecosystem due to the efficient recycling of metabolites/by-products. Process converted energetic H2S into S0 and SO42- while utilizing CO2 to boost metabolism. During stable operation, H2S bio removal was very competitive with adsorption rates as H2S bioremoval of 3.8 kg/m3/day (100%) was accomplished with maximum CO2 consumption of 60 kg/m3/day (100%). Interestingly, H2S bioremoval was highly correlated with CO2 fixation, as the H2S uptake rate reached 600 mol/h/g dry weight while assimilating 510 mol/h/g protein of CO2. Simultaneous utilization of H2S and CO2 was possible because of the highly efficient microbial ecosystem developed by ten sulfur assimilating microbial groups. OD600 drastically increased from 0.2 to 4.0, due to the efficient channeling of H2S to each microbial cell within the engineered microbial ecosystem. We believe our developed system could be highly useful for cleaning a variety of fuels highly polluted with H2S and CO2.

Exceptionally effective H2S absorption and conversion into thiols in novel superbase protic ionic liquids

AbstractWe demonstrate an effective strategy for capture and conversion of H2S in novel superbase protic ionic liquids (SPILs). It is found that the synthesized SPILs with the multiple active sites exhibit the unprecedented H2S uptake via chemical absorption (up to 1.81 mol mol−1 at 298.2 K and 1 bar). More importantly, H2S molecule is activated by these SPILs during the absorption process, so that the activated H2S can be converted further into high value‐added thiols in situ with excellent yields under mild conditions (303.2 K and 1 bar) without any solvents and metallic catalysts. Since H2S‐saturated SPILs can be regenerated by chemical conversion of absorbed H2S into thiols, thereby eliminating the higher input of energy consumption during the process of H2S stripping. This SPIL‐mediated scheme provides an alternative approach for the capture and chemical conversion of H2S.

Hydrogen Sulfide Regulates Irisin and Glucose Metabolism in Myotubes and Muscle of HFD-Fed Diabetic Mice.

Irisin, a novel myokine, is secreted by the muscle following proteolytic cleavage of fibronectin type III domain containing 5 (FNDC5) and is considered a novel regulator of glucose homeostasis. Cystathionine γ-lyase (CSE) produces hydrogen sulfide (H2S) and is involved in glucose homeostasis. We examined the hypothesis that H2S deficiency leads to decreased FNDC5 and irisin secretion, and thereby alters glucose metabolism. High-fat diet-fed mice exhibited elevated blood glucose and significantly reduced levels of CSE, H2S, and PGC-1α, with decreased FNDC5/irisin levels and increased oxidative stress in the muscle compared with those of normal diet-fed mice (control). High glucose or palmitate decreases CSE/PGC-1α/FNDC5 levels and glucose uptake in myotubes. Inhibitors (propargylglycine and aminooxyacetate) of H2S producing enzymes or CSE siRNA significantly decreased levels of H2S and FNDC5 along with PGC-1α; similar H2S-deficient conditions also resulted in decreased GLUT4 and glucose uptake. The levels of H2S, PGC-1α, and FNDC5 and glucose uptake were significantly upregulated after treatment with l-cysteine or an H2S donor. Myoblast differentiation showed upregulation of PGC-1α and FNDC5, which was consistent with the increased expression of CSE/H2S. These findings suggest that the upregulation of H2S levels can have beneficial effects on glucose homeostasis via activation of the PGC-1α/FNDC5/irisin signaling pathway.

Role of Bimetallic Solutions in the Growth and Functionality of Cu-BTC Metal-Organic Framework.

Bimetallic solutions play a vital role in the growth and functionality of copper trimesate (Cu-BTC) metal–organic frameworks (MOFs). The effect of Ag+, Ca2+, Mn2+, Co2+, and Zn2+ on the growth of Cu-BTC was studied by fabricating M-Cu-BTC MOFs at room temperature using bimetallic M-Cu solutions. While Ag+ in the MOF had a rod-like morphology and surface properties, divalent cations deteriorated it. Moreover, unconventional Cu+ presence in the MOF formed a new building unit, which was confirmed in all the MOFs. Apart from Ag and Mn, no other MOF showed any presence of secondary cations in the structure. While Ag-Cu-BTC showed an improved H2S uptake capacity, other M-Cu-BTC MOFs had superior organic pollutant adsorption behavior. Thus, we have demonstrated that the physicochemical properties of Cu-BTC could be modified by growing it in bimetallic solutions.

Highly efficient and reversible H2S capture by mercapto carboxylic anion functionalized ionic liquids

Four mercapto carboxylic anion functionalized ionic liquids (MCA-ILs) were designed and applied in H2S uptake. The solubility of H2S in MCA-ILs aqueous solution was measured from 303.2 to 333.2 K and pressure up to 1.0 bar. The reaction equilibrium thermodynamic model (RETM) was applied to fit the experimental data. Impressively, it was found that mercapto carboxylic anion captured H2S through 1:1 and 2:1 M ratio manner, which was supported by the results of RETM and quantum chemistry calculations. Furthermore, the solubility of H2S in 95% [P4444][MSA] could reach up to 0.9 mol/mol ILs and the enthalpy of the reaction was low (–22.21 kJ/mol). Considering the high H2S absorption capacity and low energy consumption of desorption, we believe that MCA-ILs solutions could provide an attractive alternative to be used as absorbent in H2S uptake.

Mechanistic study on H2S and subsequent O2 adsorption on iron oxides and hydroxides

Iron oxides are useful adsorbents for the alternating removal of H2S and O2 from natural gas and biogas. In this context, the present paper aims to elucidate the mechanisms behind the consecutive adsorption of both gases. Three different types of iron oxides/hydroxides were investigated using in-situ infrared and Raman spectroscopy as well as ex-situ X-ray diffraction.The spectroscopic studies confirm that H2S is adsorbed on all kinds of surface sites, particularly at Brønsted and Lewis acid sites. However, on the Brønsted acid sites, H2S undergoes dissociation, leading to the formation of SH−, S2− and H2O. This mechanism substantiates the high H2S uptake capacity of the OH-containing adsorbents. Prolonged H2S adsorption provokes an increasing consumption of the adsorbent, yielding amorphous FeS and elemental sulfur, with hydrogen sulfate and sulfate species also forming as by-products.Furthermore, the subsequent O2 adsorption on the sulfidized samples causes some re-formation of the initial adsorbent with the simultaneous production of elemental sulfur and sulfate entities. As a result of the mechanistic understanding gained in this study, it is concluded that the complete regeneration of the iron substrates is almost impossible due to their substantial degradation, associated with partial conversion into sulfates and the deposition of sulfur.

Adsorption of Hydrogen Sulfide at Low Temperatures Using an Industrial Molecular Sieve: An Experimental and Theoretical Study.

In the work presented herein, a joint experimental and theoretical approach has been carried out to obtain an insight into the desulfurization performance of an industrial molecular sieve (IMS), resembling a zeolitic structure with a morphology of cubic crystallites and a high surface area of 590 m2 g–1, with a view to removing H2S from biogas. The impact of temperature, H2S inlet concentration, gas matrix, and regeneration cycles on the desulfurization performance of the IMS was thoroughly probed. The adsorption equilibrium, sorption kinetics, and thermodynamics were also examined. Experimental results showed that the relationship between H2S uptake and temperature increase was inversely proportional. Higher H2S initial concentrations led to lower breakpoints. The presence of CO2 negatively affected the desulfurization performance. The IMS was fully regenerated after 15 adsorption/desorption cycles. Theoretical studies revealed that the Langmuir isotherm better described the sorption behavior, pore diffusion was the controlling step of the process (Bangham model), and that the activation energy was 42.7 kJ mol–1 (physisorption). Finally, the thermodynamic studies confirmed that physisorption predominated.

Enhanced gas adsorption using an effective nanoadsorbent with high surface area based on waste jute as cellulose fiber

In this study, waste jute as a novel nanoadsorbent in order to provide a unique micro-mesoporous structure has been successfully synthesized and fabricated. We prepared the nanoadsorbent through a simple chemical activation procedure at the different C/KOH ratios (1:1, 1:2, 1:3, and 1:4) and regarding C/KOH ratios utilized named waste jute A, waste jute B, waste jute C, and waste jute D (WJ-A, WJ-B, WJ-C, WJ-D). To evaluate the physicochemical characterization of the nanoadsorbents, FESEM, elemental mapping, BET, CHNS, FTIR, and XRD analyses were investigated. The performance of synthesized nanoadsorbents for CO2, CH4, and H2S adsorption was evaluated at the pressure range of 1 to 35 bar and at the temperature of 25 °C. The empirical models were utilized in order to investigate the behavior of adsorbed gases. The selectivity and stability of gas adsorption were also investigated. The nanoadsorbents provided a large surface area (2584 m2/g), and WJ-D sample created the highest pore volume (1.47 cm3/g). Furthermore, WJ-D sample provided an excellent CO2, CH4, and H2S uptake at both 1 bar (CO2: 9.15, CH4: 4.2, and H2S: 19.08 mmol/g) and 35 bars (CO2: 26.18, CH4: 10.06). The results also demonstrated that the selectivity of WJ-B and WJ-D at the rate of 10:90 and 1 bar was 2.03 and 2.87, respectively. The elemental analysis showed that the synthesized nanoadsorbents (WJ-A, WJ-B, WJ-C, WJ-D) were rich enough in terms of functional groups, which contained 87.38, 89.88, 91.84, and 93.34 wt% C; 0.72, 1.34, 1.90, and 1.78 wt% H; and 0.36, 0.94, 1.20, 0.91 wt% N, respectively. The thermodynamic parameters were also calculated and the results confirmed a physisorption and multilayer for the nanoadsorbents used. The large surface area and the micropore structure created of the synthesized nanoadsorbents together with low cost and availability make them a superior adsorbent, and consequently its application for gas adsorption in a large scale could be mainly considered.

Preparation and characterization of ZnO nanorods grown on Pd-activated polyacrylonitrile (PAN) fiber

Zinc oxide (ZnO) nanorods were synthesized on the surface of polyacrylonitrile (PAN) fiber by electroless reaction, which was pre-activated with palladium (Pd) nanoparticles. Pd-activation process was achieved by a reduction reaction of palladium(II) bis(acetylacetonate), Pd(acac)2 in a dry process, that is to say, Pd(acac)2 molecules sublimated, penetrated into the surface of PAN fiber and spontaneously reduced to Pd nanoparticles at 180 °C under nitrogen atmosphere. The morphology of hexagonal ZnO nanorods grown on the surface of PAN fiber was observed by a field emission scanning electron microscopy (FE-SEM) and their elemental composition was evaluated by an X-ray photoelectron spectroscopy (XPS). X-ray diffraction (XRD) analysis showed that the crystalline structure of ZnO nanorods was wurtzite cryatal structure consisted of hexagonal lattice. Sulfur removal performance of the ZnO nanorod increased with increasing electroless reaction time. The saturated H2S uptake weight was 12.4 wt% of ZnO/PAN fiber prepared at 80 °C for 180 min.

Carbon-Dioxide and Hydrogen-Sulfide Removal from Simulated Landfill Gas Using Steel Slag

Municipal solid waste landfills are a source of major greenhouse gases such as methane (CH4) and carbon dioxide (CO2) and emit a trace amount of hydrogen sulfide (H2S). Recently, steel slag has extensively been used for mineral CO2 sequestration to minimize the CO2 releases to the atmosphere. This study explores the potential of basic oxygen furnace (BOF) steel slag to simultaneously remove CO2 and H2S from landfill gas (LFG). Various batch and column tests were conducted to evaluate the CO2 and H2S removal potential of the BOF slag under various conditions such as moisture content and particle size of the BOF slag. The three different particle sizes of BOF slag (coarse, as-is, and fine) were exposed to continuous flow of a synthetic LFG [50% CO2, 48.25% CH4, and 1.75% H2S by volume (v/v)] in a column reactor to evaluate the effect of particle size on CO2 and H2S removal capacity of the slag. Similarly, the BOF slag was exposed to synthetic LFG as well as 20% (v/v) of H2S alone in batch reactors at varying moisture contents (10%–30% by weight) to evaluate the effect of moisture content on the CO2 and H2S removal capacity of the slag. A significant H2S removal of 27 g H2S kg−1 BOF slag and CO2 removal of 76 g CO2 kg−1 BOF slag were obtained in the batch reactor. The fine BOF slag (<0.106 mm) showed the maximum CO2 removal (300 g CO2 kg−1 BOF slag) and H2S removal (38 g H2S kg−1 BOF slag) upon exposure to continuous synthetic LFG flow in the column reactor. The quantitative X-ray diffraction (QXRD) analysis showed the highest increase in carbon (77.5 g C kg−1 BOF slag) and sulfur (28 g S kg−1 BOF slag) contents in the fine BOF slag, which was consistent with the mass balance of carbon and sulfur from CO2 and H2S uptake in column tests. The major reaction product with H2S was elemental sulfur depicted by the significant increase in the sulfur content in the X-ray fluorescence analysis. The key minerals involved in carbonation reactions were lime, portlandite, and larnite, as these minerals showed significant reduction in weight percentage (100%, 82%, and 80%, respectively) in the QXRD analysis. Overall, BOF slag showed promising results in mitigating CO2 and H2S from LFG.

A Robust and Biocompatible Bismuth Ellagate MOF Synthesized Under Green Ambient Conditions.

The first bioinspired microporous metal–organic framework (MOF) synthesized using ellagic acid, a common natural antioxidant and polyphenol building unit, is presented. Bi2O(H2O)2(C14H2O8)·nH2O (SU-101) was inspired by bismuth phenolate metallodrugs, and could be synthesized entirely from nonhazardous or edible reagents under ambient aqueous conditions, enabling simple scale-up. Reagent-grade and affordable dietary supplement-grade ellagic acid was sourced from tree bark and pomegranate hulls, respectively. Biocompatibility and colloidal stability were confirmed by in vitro assays. The material exhibits remarkable chemical stability for a bioinspired MOF (pH = 2–14, hydrothermal conditions, heated organic solvents, biological media, SO2 and H2S), attributed to the strongly chelating phenolates. A total H2S uptake of 15.95 mmol g–1 was recorded, representing one of the highest H2S capacities for a MOF, where polysulfides are formed inside the pores of the material. Phenolic phytochemicals remain largely unexplored as linkers for MOF synthesis, opening new avenues to design stable, eco-friendly, scalable, and low-cost MOFs for diverse applications, including drug delivery.

Synthesis of novel and engineered UiO-66/graphene oxide nanocomposite with enhanced H2S adsorption capacity

Herein, in order to desulfurize the gas streams and assist in the environmental protection, a novel nanocomposite adsorbent was synthesized. To this end, the Zr-metal organic framework (UiO-66)/graphene oxide (GO) nanocomposites were synthesized by employing different GO contents (3, 7, and 10 wt%) for hydrogen sulfide (H2S) adsorption in a dynamic adsorption system at 30, 40 and 50 °C. The prepared nano-adsorbents were characterized by TEM, SEM, BET, FTIR, and TGA techniques. The H2S absorption capacity of the ZMGO nanocomposites and the pristine UiO-66 were measured. The H2S adsorption results revealed that the adsorption capacities of H2S on the prepared nanocomposites were much better than the pristine UiO-66 adsorbent. The ZMGO-3 nanosorbent resulted in the maximum H2S uptake of 8.7 mmolS/g at 30 °C due to higher surface area and the micropore volume, which was about 3 times higher than that of the UiO-66. Finally, the repeated adsorption/desorption experiments clarified that the adsorption capability of ZMGO-3 was approximately stable along with a 10-15% reduction of the H2S adsorption capacity H2S after 3 cycles.

Soft templating production of porous carbon adsorbents for CO2 and H2S capture

We report the influence of structural features on the properties of porous carbonaceous materials obtained using soft-templating coupled with hydrothermal carbonisation. Our results demonstrate that using d-glucose with Pluronic P123 results in a more homogeneous particle size distribution of carbon spheres compared with d-fructose. The textural properties of the carbon materials, both surface area and pore volume, have improved when the carbonisation temperature was increased from 550 °C to 900 °C, while the amount of CC bonds was also increased. Physical activation with CO2 was found to open the pores and thereby improve textural properties, including total pore volume, micropore volume, and surface area. Concomitantly, the CO2 and H2S uptake also underwent significant enhancement, achieving a maximum CO2 adsorption capacity of 8.37 mmol/g at 0 °C and 1 bar, and ca. 6 mmol/g at room temperature and 1 bar. The same samples showed about 25.7 mmol/g adsorption capacity for H2S at room temperature and atmospheric pressure, with approximately 32% process efficiency.

Interlayer-Confined Cu(II) Complex as an Efficient and Long-Lasting Catalyst for Oxidation of H2S on Montmorillonite

Removal of highly toxic H2S for pollution control and operational safety is a pressing need. For this purpose, a montmorillonite intercalated with Cu(II)-phenanthroline complex [Cu[(Phen)(H2O)2]2+ (Mt-CuPhen) was prepared to capture gaseous H2S under mild conditions. This hybrid material was simple to obtain and demonstrated an outstanding ability to entrap H2S at room temperature, retaining high efficiency for a very long time (up to 36.8 g of S/100 g Mt-CuPhen after 3 months of exposure). Sorbent and H2S uptake were investigated by elemental analysis, X-ray powder diffraction measurements, diffuse reflectance (DR) UV–Vis and infrared spectroscopy, thermal analysis and evolved gas mass spectrometry, scanning electron microscopy equipped with energy-dispersive X-ray spectrometer, and X-ray absorption spectroscopy. The H2S capture was studied over time and a mechanism of action was proposed. The entrapping involves a catalytic mechanism in which [Cu[(Phen)(H2O)2]2+ acts as catalyst for H2S oxidation to S0 by atmospheric oxygen. The low cost and the long-lasting performance for H2S removal render Mt-CuPhen an extremely appealing trap for H2S removal and a promising material for many technological applications.

Effective adsorption of hydrogen sulfide by intercalation of TiO2 and N-doped TiO2 in graphene oxide

In this research, hydrogen sulfide was adsorbed onto the TiO2/graphene oxide (TiO2/GO) nanohybrids. In this regard, the band gap energy of the TiO2 nanoparticles was altered through nitrogen doping which influence the chemical properties of the metal oxides. The nanoadsorbents were characterized before and after adsorption of H2S. The effect of the temperature (200−220 °C) on the H2S adsorption capacity was examined. The results showed that the increase in the temperature had a positive effect on the adsorption of H2S for all of TiO2/GO hybrid nanoadsorbents. The optimum breakthrough capacities for 5%TiO2/GO, 10 %TiO/GO and 5%N-TiO2/GO was obtained at 220 °C as 0.25, 0.20 and 0.17 gS/g sorbent, respectively. The 5%N-TiO2/GO was found to be the best nanoadsorbent due to its lower band gap, higher surface area, synergic effects and presence of active sites of N-TiO2 over the nanoadsorbents. The H2S uptake capability of the 5%N-TiO2/GO nanoadsorbent was reduced to about 30–60 % after 2 regeneration cycles due to the chemisorption.

A sustainable design of ZnO-based adsorbent for robust H2S uptake and secondary utilization as hydrogenation catalyst

Low sulfur capacity and low regeneration performance are the long-time problems in the industrial application of ZnO-based adsorbents for ambient H2S removal. However, no efficient approach has been reported up to now to simultaneously solve these two problems. With the increasingly stringent environmental regulations in China, a robust but sustainable ZnO-based adsorbent is strongly desired. Herein, we constructed such an adsorbent for the first time by introducing cobalt species into ZnO/SiO2 to form a heterostructured ZnO-Co3O4/SiO2 nanocomposite. For comparison, Co doped ZnO/SiO2 and Zn doped Co3O4/SiO2 were also fabricated. According to the breakthrough tests with initial H2S partial pressure of 57 Pa, the heterostructured ZnO-Co3O4/SiO2 adsorbent exhibited highest sulfur capacity of 188.4 mg S/g sorbent at breakthrough level of 1%, the corresponded partition coefficient (at 0.57 Pa, 303 K) was 10.3 mol. kg−1. Pa−1. The introduced Co species not only improved the dispersion of ZnO nanograins, but also served as active sites for reacting and oxidizing H2S molecular. It also found that the formed ZnO-Co3O4 heterostructure could boost the hydroxylation of H2O, which provided an alkali environment for H2S dissociation. More meaningfully, this exhausted sorbent could be secondarily utilized as catalyst for carbonyl sulfide (COS) hydrogenation and exhibited 100% COS conversion even at a temperature lower than 200 °C, which was almost 3.3 times the conversion achieved by a commercial Co-Mo/Al2O3 catalyst (30%). This study will provide a new idea for rational design of metal oxide-based adsorbents to avoid causing secondary pollution by the spend adsorbents.

Tuning the ZnO-activated carbon interaction through nitrogen modification for enhancing the H2S removal capacity

Herein, an unusual strategy is reported to enhance the H2S uptake capacity by varying the ZnO-support interaction and controlling the acid-basic environment of the pore channel; this is in place of the generally reported method of decreasing ZnO nanoparticle size and optimizing their porosity. With this regard, coal based activated carbon (AC) is selected as the support and the interaction with ZnO is tuned by introducing N species on AC surface through a soft nitriding strategy. Our strategy is confirmed to be prospective based on the fact that the N-modifying AC supported ZnO adsorbent show a maximum breakthrough sulfur capacity (BSC) of 62.5 mg S/g sorbent, two times larger than that without N-modification (30.5 mg S/g sorbent). The enhanced BSC is attributed to the introduced N species, which not only increases the basicity of the water film condensed in the pores, promoting the dissociation of H2S and H2O, but also influences the electronic structure of ZnO, accelerating the rate of lattice diffusion during in sulfidation process. It is also found that the high BSC of sorbent with N modification is related to the doped N concentrations, ZnO dispersion and the material porosity. This paper provides a new insight for designing supported ZnO based adsorbents.

New adsorbents from maize cob wastes and anaerobic digestate for H2S removal from biogas

Two activated carbons (ACs) were prepared by physical activation of Maize Cob Waste (MCW) with CO2, during 2 and 3 h (MCW(PA)2h and MCW(PA)3h, respectively). Two other ACs were prepared by chemical activation: a) MCW(LD) – MCW was impregnated with anaerobic liquid digestate (LD) and carbonized under N2 atmosphere; and b) CAR-MCW(LD) – previously carbonized MCW was impregnated with LD and carbonized under N2 atmosphere. All ACs were fully characterized for textural and chemical properties, and then used in dynamic H2S removal assays from real biogas samples. Regarding H2S removal, the ACs that were physically activated behaved much better than the impregnated ones: MCW(PA)3h and MCW(PA)2h showed H2S uptake capacities of 15.5 and 0.65 mg g−1, respectively, while MCW(LD) and CAR-MCW(LD) showed values of 0.47 and 0.25 mg g−1, respectively. This may indicate that textural properties (surface area and microporosity) are more important than mineral content in H2S removal. Effectively, both surface area and micropore volume were much higher for the samples of MCW(PA)3h (SBET = 820 m2 g−1 and Vmicro = 0.32 cm3 g−1) and MCW(PA)2h (SBET = 630 m2 g−1 and Vmicro = 0.21 cm3 g−1) than for the ACs that were chemically activated (SBET = 38.0 m2 g−1 and Vmicro = 0.01 cm3 g−1 for MCW(LD); SBET = 8.0 m2 g−1 and Vmicro = 0.01 cm3 g−1 for CAR-MCW(LD)). High oxygen content in MCW(PA)3h favoured the catalytic oxidation reaction of H2S, promoting its removal. The use of MCW as precursor and LD as activating agent of the ACs may contribute for the integrated management of maize wastes and to diversify the applications of anaerobic digestate.