Sulfide Removal Research Articles

Enhancement of bio-S0 recovery and revealing the inhibitory effect on microorganisms under high sulfide loading

Biodesulfurization is a mature technology, but obtaining biosulfur (S0) that can be easily settled naturally is still a challenge. Increasing the sulfide load is one of the known methods to obtain better settling of S0. However, the inhibitory effect of high levels of sulfide on microbes has also not been well studied. We constructed a high loading sulfide (1.55–10.86 kg S/m3/d) biological removal system. 100% sulfide removal and 0.56–2.53 kg S/m3/d S0 (7.0 ± 0.09–16.4 ± 0.25 μm) recovery were achieved at loads of 1.55–7.75 kg S/m3/d. Under the same load, S0 in the reflux sedimentation tank, which produced larger S0 particles (24.2 ± 0.73–53.8 ± 0.70 μm), increased the natural settling capacity and 45% recovery. For high level sulfide inhibitory effect, we used metagenomics and metatranscriptomics analyses. The increased sulfide load significantly inhibited the expression of flavin cytochrome c sulfide dehydrogenase subunit B (fccB) (Decreased from 615 ± 75 to 30 ± 5 TPM). At this time sulfide quinone reductase (SQR) (324 ± 185–1197 ± 51 TPM) was mainly responsible for sulfide oxidation and S0 production. When the sulfide load reached 2800 mg S/L, the SQR (730 ± 100 TPM) was also suppressed. This resulted in the accumulation of sulfide, causing suppression of carbon sequestration genes (Decreased from 3437 ± 842 to 665 ± 175 TPM). Other inhibitory effects included inhibition of microbial respiration, production of reactive oxygen species, and DNA damage. More sulfide-oxidizing bacteria (SOB) and newly identified potential SOB (99.1%) showed some activity (77.6%) upon sulfide accumulation. The main microorganisms in the sulfide accumulation environment were Thiomicrospiracea and Burkholderiaceae, whose sulfide oxidation capacity and respiration were not significantly inhibited. This study provides a new approach to enhance the natural sedimentation of S0 and describes new microbial mechanisms for the inhibitory effects of sulfide.

Simultaneous removal of H2S and particulate matter by a multistage dual-flow sieve plate scrubber

In this work, an experimental study has been conducted in a newly designed and developed dual-flow scrubber with three sieve plates for simultaneous removal of hydrogen sulphide and particulate matter (fly-ash) from syngas produced in a gasifier as these impurities of syngas destroy and decrease the efficiency of the downstream processing equipment. The performance of the scrubber at different gas and liquid flow rates in the range of 16.59 × 10−4- 27.65 × 10−4 Nm3/s 20.649 × 10−6-48.183 × 10−6 m3/s has been observed for both the particulate matter and hydrogen sulphide removal along with the effect of inlet particulate loading (15 × 10−3- 25 × 10−3 kg/Nm3) and 100–300 ppm inlet H2S loading. The H2S removal efficiency in the dual-flow wet scrubber increased from 78.88% to 87.45% when the particulate matter loading was increased from zero to 25 × 10−3 kg/Nm3 at 300 ppm inlet H2S concentration for 48.183 × 10−6 m3/s liquid flow rate and 27.65 × 10−4 Nm3/s gas flow rate. The efficiency of the particulate matter is similar to that of the particulate scrubbing in absence of the H2S.

Removal of hydrogen sulfide by metal-free amine-functionalized mesoporous carbon at room temperature: Effect of amines

The introduction of nitrogen can effectively improve the alkalinity of carbon materials, introduce catalytic sites and active oxygen radicals, thus enhancing the desulfurization ability. However, the study on the effect of amine species and loading amount on the desulfurization properties is very limited. In this study, mesoporous carbon materials with large specific surface area and pore volume were prepared. Different amines were selected as impregnating agents to investigate the performance of amine-functionalized carbon catalysts for hydrogen sulfide (H2S) removal under various operating conditions. The synthesized carbon material has a large specific surface area of 989 m2/g, with an average pore diameter of 12.94 nm. The well-developed pores could not only provide the space for the dispersion of amine, but also facilitate the diffusion of H2S and the storage of sulfur products. Amine increase the alkalinity of carbon material and the reactivity of reaction sites located on the carbon skeleton. The desirable catalytic performance of catalysts impregnated by amines should be the compromise among spatial structure of the amine, the surface chemistry and porosity of catalysts. Among them, the polyethylene polyamine impregnated carbon catalyst with a high ratio of secondary and tertiary amine (80.54 %) showed the best catalytic performance of 1.58 g H2S/g-catalyst at 30 °C due to due to suitable steric hindrance and higher stability in the H2S adsorption–desorption cycle. This work further refines the previously proposed reaction mechanism and provides a possibility for the application of carbon-based catalysts with directional introduction of nitrogen elements by impregnation method in the removal of H2S.

Evaluation of commercial moving bed media and sugarcane bagasse as packing material in biotrickling filter for hydrogen sulfide removal

This study compared two biotrickling filter packing materials for hydrogen sulfide removal. Inlet H2S concentrations and empty-bed retention time were tested on the two biotrickling filters. First reactor (BT1) had immobilized sulfur-oxidizing bacteria on commercial moving-bed media, whereas second reactor (BT2) had sulfur-oxidizing bacteria on sugarcane bagasse. The study found that BT1 performed best at 120 s empty-bed retention time, 422.39 g/m3·h hydrogen sulfide loading rate, resulted in 416 g/m3·h hydrogen sulfide elimination capacity. In contrast, BT2 performed best at 180 s empty-bed retention time, 278.77 g/m3·h hydrogen sulfide loading rate, and 273 g/m3·h elimination capacity was achieved. High-throughput sequencing showed Acidithobacillus spp. dominated the sulfur-oxidizing bacteria consortium. Sugarcane bagasse may receive less hydrogen sulfide loading than moving bed medium under optimal conditions, but its low cost and reasonable removal capacity of hydrogen sulfide -containing industrial gases in a biotrickling filter system make it an excellent alternative packing material.

Electric discharge by sulphide shuttling bacteria

AbstractBACKGROUNDIn biodesulphurisation processes, sulphide oxidising bacteria (SOB) convert toxic sulphide to sulphur. Haloalkalophilic SOB are known to anaerobically remove sulphide from solution and release electrons when subsequently exposed to an electrode. This makes SOB able to spatially decouple sulphide removal and current production, thereby acting as sulphide shuttles. Little is known about the kinetics of electron release by sulphide shuttling SOB. To gain more insight into the sulphide shuttling mechanism and electron release, current production of abiotic sulphide and sulphide shuttling SOB was compared.RESULTSSOB communities dominated by Thioalkalivibrio sulfidophilus were incubated with sulphide in batch experiments. After sulphide was removed, SOB were discharged in an electrochemical cell. Anode potential, sulphide load and biomass concentration were varied. Current was produced at potentials of −0.2 V versus Ag/AgCl and higher, and at a potential of 0.1 V a coulombic efficiency of 70% was reached in 30 min. The maximum charge recovered from biologically stored sulphide was 4900 ± 810 mC mgN−1. Discharge kinetics were not affected by biomass concentration or degree of sulphide removal and kinetics of biotic and abiotic current production were similar.CONCLUSIONCurrent production of sulphide shuttling SOB and abiotic sulphide was highly similar. This implies that sulphide shuttling is based on sorption to the biomass, and that shuttled sulphide converts to sulphur directly at the electrode surface. Therefore, the sulphide shuttling strategy is not sufficient to prevent electrode passivation, and different strategies need to be applied in the design of a sulphur‐producing bioelectrochemical desulphurisation process. © 2023 Society of Chemical Industry.

Geology and sulphide geochemistry of the Ni-Cu-Co mineralisation of the Espedalen Complex, Norway: Constraints for the distribution of magmatic sulphides within a variably deformed anorthosite suite

The Espedalen Complex is located in the eastern portion of the Jotun–Valdres Nappe Complex, south-central Norway and comprises three main suites (jotunite-charnockite-augengneiss; main anorthosite–ultramafite–norite; and gabbronorite suites) formed between 1520 and 1500 Ma. The anorthosite-ultramafite-norite suite hosts Ni-Cu-Co mineralisations grouped as: i) ‘primary sulphides’ referring to undeformed occurrences with magmatic textures; ii) ‘deformed sulphides’ which include dismembered ore bodies; and iii) ‘remobilised sulphides’ which comprise thin sulphide veinlets indicating remobilisation. The ‘primary sulphides’ characterise the deposits of Dalen, Megrund, Trona, Veslegruva and Melgard, whereas the ‘deformed sulphides’ characterise the deposits of Stormyra, Storgruva, Andreasberg, Niccoline, Gråhøa, Jørstad and Grimstjønna. The largest mineralisations are the Dalen and Stormyra deposits, which host 5.3 Mt @ 0.29% Ni, 0.12% Cu and 0.02% Co, and 1.01 Mt @ 1.09% Ni, 0.48% Cu and 0.04% Co, respectively. This study provides the first systematic characterisation of the different Ni-Cu-Co mineralisations from the Espedalen Complex.Primary sulphides are typically hosted by medium-grained poikilitic olivine-orthopyroxenite, whereas deformed sulphides are hosted within shear zones, commonly within anorthosites. Primary and deformed occurrences comprise disseminated, net-textured and massive sulphides. The disseminated and semi-massive to massive sulphide ores from different localities comprise pyrrhotite and pentlandite with minor chalcopyrite. Post-magmatic sulphide alteration and recrystallisation (notably at Stormyra Deposit) are marked by variable (5 to 30%) development of pyrite, which replaces pyrrhotite-dominated masses. The remobilised sulphide assemblages are associated with retrograde silicates (e.g., chlorite and talc). Overall, primary and deformed sulphides can be divided into three main compositional groups based on metal tenors and the concentration of platinum-group elements (PGE): (i) Stormyra, Andreasberg (both deformed) and Megrund (primary) have the highest Ni and Cu tenors (7 to 8.5% and 3 to 3.5%, respectively) and no IPGE (Ir-group PGE) depletion relative to PPGE (Pt-group PGE); (ii) Dalen, Trona, Melgard (primary), Jørstad, Gråhøa and Grimstjønna (deformed) are similar regarding PGE distribution but have lower Ni and Cu tenors (4 to 5.5% and 1.6 to 3%, respectively); and (iii) Niccoline, Storgruva (deformed) and Veslegruva (primary) have comparable Ni and Cu tenors to group (ii), but are IPGE-depleted relative to PPGE (i.e. fractionated PGE distribution). The tenors vary from 0.3 to 2% Ni and 0.25 to 1.5% Cu in remobilised sulphides. Variations in metal tenors are interpreted to reflect a combination of different, but invariably PGE-depleted, parental magmas and variable R-factor regimes (R-factor varying from 350 to 700) during ore formation. The parental magmas can be modelled as the product of 15% mantle melting followed by approximately 2% crystallisation with sulphide removal, which lead to a PGE-depleted nature. Redistribution of sulphides during deformation of the Espedalen Complex seems to have taken place at large and small scales. Large-scale tectonic displacement has no major geochemical impact, whereas local remobilisation yielded sulphide veinlets with low metal tenors. We support that assessing if other geological domains, previously assigned to the Jotun-Valdres Nappe, are correlated or not with the Espedalen Complex is essential for further expanding this prospective area as these terrains could represent potential targets for Ni-Cu-Co deposits.

Substrate-dependent strategies to mitigate sulfate inhibition on microbial reductive dechlorination of polychlorinated biphenyls

Sulfate widely co-exists with polychlorinated biphenyls (PCBs) at various concentrations in the subsurface environment. Previous studies have suggested that sulfate often hampers microbial degradation of aliphatic chlorinated solvents such as chloroethenes. However, the impact of sulfate on microbial reductive dechlorination of aromatic PCBs and the underlying mechanisms have received limited attention. Likewise, strategies to mitigate such inhibition remain scarce. Here we found that the mechanisms and mitigation strategies of sulfate inhibition on PCB dechlorination were substrate-dependent. Under electron donor-limiting conditions, even a low concentration of sulfate (2 mM) resulted in a decreased PCB dechlorination rate by 88.7% in a co-culture comprising Dehalococcoides mccartyi CG1 and the sulfate-reducing bacterium Desulfovibrio desulfuricans F1, an inhibition which was attributed to the competition for electron donor between sulfate reduction and PCB dechlorination. As expected, re-amendment of 5 mM lactate effectively re-initiated PCB dechlorination. However, in the presence of a higher concentration of sulfate (5 mM), the PCB dechlorination rate in the co-culture was 77.7% lower than in the control, even with excessive electron donor supply. This inhibition was linked to high concentration of sulfide (∼5 mM) produced from sulfate reduction, as suggested by high availability of electron donor, recovery of dechlorination activity after removal of sulfide, and negligible influence of sulfate on PCB dechlorination in the axenic culture of D. mccartyi CG1. Indeed, sulfide (>5 mM) was found to directly suppress expression of PCB-dechlorinating reductive dehalogenase gene. The highest transcriptional level of pcbA1 was 2.9 ± 0.3 transcripts·cell−1 in the presence of ∼5 mM sulfide, which was increased to 37.4 ± 5.0 transcripts·cell−1 when sulfide was removed. Under this scenario, introduction of ferrous salts (5 mM) efficiently alleviated sulfide inhibition on PCB dechlorination. Interestingly, the augmentation of methanogens in the co-culture was also effective in mitigating sulfide inhibition on PCB dechlorination, offering a new approach to protect Dehalococcoides under sulfide stress. Collectively, these findings deepen our understanding of the influence of sulfate on microbial reductive dechlorination of PCBs and contribute to developing appropriate strategies based on geochemical conditions to alleviate sulfate inhibition during bioremediation of PCB-contaminated sites.

Designing Al-SiO2 nanospheres with co-doped Ce/Cd for the removal of 4,6-dimethyldibenzothiophene of fuel oil

Catalytic oxidative coupled in-situ hydrodesulfurization technology as an emerging desulfurization process is applied to the removal of organic sulfides from fuels. In this study, Al-SiO2@Ce/Cd core-shell nanosphere catalysts were prepared by a sol-gel method and a co-impregnation method using silica as the carrier, and were in turn applied for the ultra-deep desulfurization of highly resilient 4,6-DMDBT from diesel oil under visible light irradiation. The prepared photocatalyst were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and Brauner-Emmette-Teller (BET). Characterization results revealed that Al-SiO2@Ce/Cd had a nanosphere structure, and Ce/Cd were successfully loaded on the surface of Al-SiO2. Bimetallic loading helped increase the specific surface area of the SiO2 material, which could anchor more effective metal active sites. The effects of metal doping amount, doping ratio, catalyst dosage, and reaction temperature on 4,6-DMDBT desulfurization were studied. The results showed that 20% Al-SiO2@Ce/Cd achieved 100% desulfurization performance within 30 min at 60 ℃, thus surpassing many state of the art catalysts reported in literature. Al-SiO2@Ce/Cd remained highly active after 10 times successive reuses with rapid recovery by washing and filtering. Organic nitride had a strong inhibitory effect on diesel desulfurization, which was derived from the competitive adsorption of nitride and sulfide on the effective active site of the catalyst. Based on characterization results and desulfurization results, the appropriate reaction mechanism of the catalytic oxidative coupling in-situ hydrodesulfurization of Al-SiO2@Ce/Cd catalysts was speculated.

Polysulfide Concentration and Chain Length in the Biological Desulfurization Process: Effect of Biomass Concentration and the Sulfide Loading Rate.

Removal of hydrogen sulfide (H2S) can be achieved using the sustainable biological desulfurization process, where H2S is converted to elemental sulfur using sulfide-oxidizing bacteria (SOB). A dual-bioreactor process was recently developed where an anaerobic (sulfidic) bioreactor was used between the absorber column and micro-oxic bioreactor. In the absorber column and sulfidic bioreactor, polysulfides (Sx2-) are formed due to the chemical equilibrium between H2S and sulfur (S8). Sx2- is thought to be the intermediate for SOB to produce sulfur via H2S oxidation. In this study, we quantify Sx2-, determine their chain-length distribution under high H2S loading rates, and elucidate the relationship between biomass and the observed biological removal of sulfides under anaerobic conditions. A linear relationship was observed between Sx2- concentration and H2S loading rates at a constant biomass concentration. Increasing biomass concentrations resulted in a lower measured Sx2- concentration at similar H2S loading rates in the sulfidic bioreactor. Sx2- of chain length 6 (S62-) showed a substantial decrease at higher biomass concentrations. Identifying Sx2- concentrations and their chain lengths as a function of biomass concentration and the sulfide loading rate is key in understanding and controlling sulfide uptake by the SOB. This knowledge will contribute to a better understanding of how to reach and maintain a high selectivity for S8 formation in the dual-reactor biological desulfurization process.

Electrochemical Hydrogen Sulfide Decomposition Using Proton Conducting Ceramic for Pure Hydrogen Production

Hydrogen sulfide (H2S) is a substance that occurs during the process of processing sulfur, which is abundant in fossil fuels such as oil and natural gas, into high-quality fuel. Due to its high toxicity, it is classified as harmful industrial waste and removal in the process of discharging is essential. Until now, refiners have used the Claus process and the Wet Sulfuric Acid (WSA) process, which reacts hydrogen sulfide with oxygen to release it in the form of water or sulfuric acid. These processes require a huge amount of heat energy and only aim to remove hydrogen sulfide, so they emit hydrogen atoms contained in hydrogen sulfide in the form of water and sulfuric acid. Because hydrogen is an eco-friendly energy source that has recently been in the spotlight, hydrogen sulfide can be a valuable resource if hydrogen can be extracted from hydrogen sulfide. In this study, an electrochemical process that decomposes hydrogen sulfide and obtains hydrogen from hydrogen sulfide, replacing the conventional hydrogen sulfide removal process was proposed. To achieve this goal, thermodynamics of this reaction was analyzed and a solid oxide electrochemical cell based on proton conducting ceramic was fabricated for operating at high temperature and using perovskite structured electrodes. Experiments were then conducted to decompose hydrogen sulfide using fabricated cells and found that about 40 ppm, 100 sccm of hydrogen sulfide was decomposed at 600 oC by applying 0.5 V, 0.57 mA/cm2. Through this, the feasibility of the process was confirmed, and the durability test and regeneration process of the anode electrode were proceeded to solve degradation caused by sulfur deposits. In this study, a process has been proposed to effectively produce hydrogen of high value as an energy source, as well as to remove industrial waste hydrogen sulfide. It is expected that waste disposal and energy source production can be simultaneously produced in a clean and efficient way if cell performance improvement, removal of sulfur poison, and large systemization are applied to oil refiners' processes.

Treatment of Organic and Sulfate/Sulfide Contaminated Wastewater and Bioelectricity Generation by Sulfate-Reducing Bioreactor Coupling with Sulfide-Oxidizing Fuel Cell.

A wastewater treatment system has been established based on sulfate-reducing and sulfide-oxidizing processes for treating organic wastewater containing high sulfate/sulfide. The influence of COD/SO42- ratio and hydraulic retention time (HRT) on removal efficiencies of sulfate, COD, sulfide and electricity generation was investigated. The continuous operation of the treatment system was carried out for 63 days with the optimum COD/SO42- ratio and HRT. The result showed that the COD and sulfate removal efficiencies were stable, reaching 94.8 ± 0.6 and 93.0 ± 1.3% during the operation. A power density level of 18.0 ± 1.6 mW/m2 was obtained with a sulfide removal efficiency of 93.0 ± 1.2%. However, the sulfide removal efficiency and power density decreased gradually after 45 days. The results from scanning electron microscopy (SEM) with an energy dispersive X-ray (EDX) show that sulfur accumulated on the anode, which could explain the decline in sulfide oxidation and electricity generation. This study provides a promising treatment system to scale up for its actual applications in this type of wastewater.

Combination of sulfide-driven partial denitrification with anammox enhanced by zeolite powder for autotrophic nitrogen and sulfide removal from wastewater

Sulfide-driven partial denitrification and anaerobic ammonia oxidizing (anammox) (SPDA) is a high-efficiency technology to achieve simultaneous nitrogen and sulfide removal. Nitrite accumulation from sulfide-driven partial denitrification is the key to achieve SPDA. Zeolite powder was added to strengthen the competition of anammox bacteria against nitrite. The nitrogen removal rate (NRR) and partial denitrification efficiency in reactor was 5.18 kg-N m−3d−1 and 92.3% during 180 days of operation, higher than those without zeolite powder, indicating an improving contribution of zeolite powder. Metabolomics analysis revealed zeolite powder addition enhanced the metabolisms of amino acids, nicotinate and porphyrin through increasing glutamate content, and improved EPS secretion, heme c content and particle size. Besides, high ammonia enriched by zeolite powder was conducive to improve anammox activity and NRR. This study provides the metabolic insights into the mechanism of zeolite powder enhancing SPDA, which is meaningful towards overcoming the limitations in practical application of SDPA.

Hydrogen sulfide removal from low concentration gas streams using metal supported mesoporous silica SBA-15 adsorbent

The removal of hydrogen sulfide (H2S) from gas mixtures is paramount as it can cause environmental damage, corrosion, and catalyst poisoning even at low concentration levels (100–200 mg/L). In this work, a series of Fe-Cu oxides supported SBA-15 materials were prepared using the wet incipient impregnation method with different Fe and Cu atomic ratios to evaluate the H2S removal performance. It was found that the H2S adsorption capacity generally increases with an increase in the CuO loading, with a Cu-Fe atomic ratio of 1.0:0.3 displaying the highest breakthrough H2S adsorption capacity of 74.08 mg H2S/g-sorbent. Through the XPS results, the adsorbent existed in the form of sulfate, sulfide, and elemental sulfur after reacting with H2S. In particular, it was confirmed that Fe2O3 helps to improve the H2S removal performance by creating an alkaline environment. The material with superior performance showed high capacity at low concentration compared to several published reports.

Sulfur-oxidising ability of bacteria isolated from soil samples in Akure, Nigeria: Site-linked evaluation

Sulfur oxidising bacteria (SOB) are of great importance in the sulfur biogeochemical cycle and removal of undesirable hydrogen sulfide in biogas production. This study evaluated the sulfide oxidising ability of bacteria from different soils using bromocresol purple dye reduction method and spectrophotometry. The study sites were the abattoir, automobile workshop, dumpsite, rhizospheric soil, and sewer disposal sites. Starkey broth was used as a selective culture broth and sodium thiosulfate as an enrichment culture medium, both at pH 8.00. Sulfur ion evaluation was carried out using spectrophotometry at 450 nm wavelength. 16S rRNA sequencing of promising SOB was investigated. The total colony count of sulfur oxidising bacteria able to reduce the bromocresol dye on the sodium thiosulfate agar ranged from 2.00 × 103 cfu/g from the abattoir, dumpsite and sewer disposal sites to 1.50 × 104 cfu/g from the automobile workshop. Paenibacillus ripae and Staphylococcus aureus had the highest sulfur oxidation absorbance of 1.72 and 1.65 with a pH of 5.75 and 5.90 respectively. The pH of the studied bacteria on the sixth day of incubation ranged from 5.69 to 6.03. Bacillus cereus, P. ripae and S. aureus demonstrated most promising potential as sulfur oxidising agents. This work revealed the presence of SOB from different locations with relatively low pH and indicates potential importance of studied bacteria in the removal of hydrogen sulfide in biogas that may not support bio-corrosion.

Simultaneous removal of sulfide and bicarbonate from synthetic wastewater using an algae-assisted microbial fuel cell

ABSTRACT The anaerobic digestion (AD) process is one of the most practiced technologies for the remediation of organic waste and maximization of energy recovery in terms of biogas or biomethane. The presence of other gaseous components in biogas, e.g. CO2 and H2S, often makes its direct application in engines and electricity production unsuitable. This work aimed to develop and utilize an algae-assisted microbial fuel cell (AMFC) for the purification of biogas by removing both CO2 and H2S and simultaneous bioelectricity generation. In addition to biogas clean-up, elemental sulfur recovery and CO2 utilization for algae cultivation add value to the proposed AMFC process. Experiments were performed with both sulfide and bicarbonate in their dissolved form, in the respective anodic and cathodic chambers of the AMFC. The sulfide concentration was varied from 100 to 800 mg/l and the AMFC exhibited a sulfide removal efficiency exceeding 97% at all concentrations tested. The process efficiency dropped, however, at sulfide concentrations above 300 mg/l in terms of both sulfide removal and power output. The AMFC performed best at 400 mg/l sulfide by exhibiting a power density of 24.99 mW/m3 and sulfide removal efficiency of 98.87%. The system exhibited columbic efficiency (CE %) in the range of 7.85–80%. The total alkalinity representing CO2, carbonate and bicarbonate levels in the algae-based system was reduced by 49.54%. The electrical energy recovered from the AMFC was 0.1 kWh/m3 and the total energy recovery, which is the sum of the electrical and algal lipid energy, amounted to 7.25 kWh/m3.

Development of microbial enrichments for simultaneous removal of sulfur and nitrogenous metabolites in saline water aquaculture.

The aim of the study was to develop microbial enrichments from the nitrifying microbial consortia and the environment for simultaneous removal of ammonia, nitrate, and sulfide in aquaculture systems at varied salinities. Sulfur and nitrogen metabolites are the major factors affecting the farmed aquatic animal species and deteriorate the receiving environments causing ecological damage. The present study reports the development of microbial enrichments from the nitrifying microbial consortia and the environment. The enrichments used thiosulfate or thiocyanate as an energy source and simultaneously removed sulfur, ammonia, and nitrite in spiked medium (125mg/l ammonia; 145mg/l nitrite). Further, the microbes in the enrichments could grow up to 30g/l salinity. Metagenomic studies revealed limited microbial diversity suggesting the enrichment of highly specialized taxa, and co-occurrence network analysis showed the formation of three micro-niches with multiple interactions at different taxonomic levels. The ability of the enrichments to grow in both organic and inorganic medium and simultaneous removal of sulfide, ammonia, and nitrite under varied salinities suggests their potential application in sulfur, nitrogen, and organic matter-rich aquaculture pond environments and other industrial effluents.

Effect of chemical composition of coal ash used to prepare granulated coal ash on the removal of hydrogen sulfide from water.

Granulated coal ash was prepared by mixing coal ash derived from a coal electric power plant and blast furnace cement, to remove hydrogen sulfide from aquatic environment. In this study, we investigate the effects of the composition of the coal ash used to prepare the granulated coal ash on its hydrogen sulfide removal performance. Manganese, magnesium, and calcium contents in the granulated coal ash were found to be the major factors in controlling the rate of hydrogen sulfide removal. The kinetics of hydrogen sulfide removal by the granulated coal ash were expressed as a first-order equation with a rate constant of 0.0081- 0.080 h-1 . The rate constant for hydrogen sulfide removal obtained in this study corelated well with the manganese content in the granulated coal ash. The increasing surface pH attributed to the hydrolysis of calcium and magnesium on the surface of the granulated coal ash slightly increased the hydrogen sulfide removal rate.

Hydrogen Sulphide and Carbonyl Sulphide Removal from Biogas for Exploitation in High-Temperature Fuel Cells

Fuel cells powered by biogas for decentralised cogeneration of heat and power are an attractive alternative to combustion technologies. However, biogas contains sulfur-based compounds (H2S, COS, DMS, siloxanes), which are harmful to fuel cells. This work was carried out in the framework of the European project Waste2Watts, involving the laboratories of Politecnico di Torino, ENEA, and PSI. The aim is to design and test a flexible and cost-effective cleaning unit to remove impurities for the use of biogas in high-efficiency fuel cell systems. The focus is on small- to medium-sized farms for which deep cleaning of biogas by adsorption materials is a suitable techno-economic solution to avoid intensive gas processing treatments. The ability of commercial adsorption materials (activated carbons, metal oxides, and metal hydroxides) to remove hydrogen sulphide and carbonyl sulphide was tested under different biogas compositions (oxygen and humidity). After evaluating the results, three plant configurations were proposed to optimally utilise the potential of the sorbents. Indeed, the RGM3 sorbent has proven to be an effective solution for removing H2S and COS under humid conditions (50% RH), whilst R7H and R8C sorbents are better suited for removing H2S and COS, respectively, in dry biogas conditions.Graphical abstract

Hydrogen sulfide removal from normal heptane using zinc oxide, silicon dioxide and zeolite 13X: adsorption capacity, kinetics, selectivity, breakthrough and regeneration.

This article focuses on the H2S adsorption from normal heptane (nC7) as synthetic natural gas liquids (NGL) using ZnO, SiO2 and zeolite 13X in static mode. Results of the isotherm and kinetics of the investigated adsorbents for H2S adsorption under ambient condition showed that ZnO had the highest H2S adsorption capacity between 260 and 700 mgH2S.g-1 in the initial concentration range of 2500 and 7500 ppmH2S with an equilibrium time of less than 30 minutes. Additionally, the ZnO selectivity was greater than 3.16. In continued, H2S removal from nC7 with ZnO was examined in dynamic mode. The H2S breakthrough time for ZnO reduced from 210 to 25 minutes as weight hourly space velocity (WHSV) was increased from 5 to 20 h-1 at 30 bar. Also, the breakthrough time at 30 bar was about 2.5 times greater than that at atmospheric pressure. Furthermore, H2S/CO2 mixture (i.e., 1000 ppmH2S + 1000 ppmCO2) caused the H2S breakthrough time to increase approximately by 1.11-fold. Alternatively, the ZnO regeneration conditions with hot stagnant air were optimized at different initial H2S concentrations (1000 ~ 3000 ppmH2S) using the Box-Behnken design. For instance, ZnO contaminated with 1000 ppmH2S was regenerated with an efficiency of more than 98 % for 160 minutes at 285 °C.

Study on the performance of anodic desulfurization and cathodic denitrification coupled electricity generation in microbial fuel cell

Sulfide autotrophic denitrification microbial fuel cell was set up and the two reaction processes of desulfurization in anode chamber and denitrification in cathode chamber were separated to study nitrogen and sulfur removal effect and electricity generation capacity. The results showed that simultaneous desulfurization in anode chamber and nitrate removal in cathode chamber was feasible. The removal load of sulfide and nitrate almost increased with the increase of their concentrations under the experiment operation conditions. Higher sulfide concentration in a certain range was beneficial to generate electricity. The change of nitrate concentration in the cathode chamber had less effect on sulfide removal efficiency and electricity production performance of microbial fuel cell, which was mainly depended on the influent sulfide concentration in the anode chamber. The maximum sulfide and nitrate removal loads were 0.36 kg∙m−3∙d−1 and 0.07 kg∙m−3∙d−1 respectively, with a maximum power density of 144.03 mW∙m−3. The external resistance affected the quantities and varieties of reaction products in the anode chamber and the cathode chamber. Lower external resistance was beneficial to improve the efficiency of nitrate removal in the cathode chamber. The microbial community structure of the anode chamber in sulfide autotrophic denitrification MFC was similar to that of sulfide autotrophic denitrification SBR, whose main functional bacterial genera were Clostridium, Thiobacillus and Rhodobacteraceae. However, the functional bacteria in the cathode chamber were completely different, whose dominant bacteria included Thiobacillus, Bacillus, Flavobacteriaceae, Acinetobacter, Sphingomonas and Paracoccus. The research results provided a new idea and method for the sulfur- and nitrogen-containing wastewater treatment.