Iron-based Adsorbents Research Articles

Environmental impact and cost analysis of arsenic removal from water using iron-based adsorbents: comparison between natural and commercial materials

Environmental impact and cost analysis of arsenic removal from water using iron-based adsorbents: comparison between natural and commercial materials

Using Iron-Based Adsorbents for the Removal of Inorganic Ecotoxicants from Aquatic Systems

Using Iron-Based Adsorbents for the Removal of Inorganic Ecotoxicants from Aquatic Systems

Insights into the relationship between Nitrilotri(methylphosphonic acid) (NTMP) adsorption and physicochemical properties of iron oxides

Non-reactive phosphorus (e.g., phosphonate) contributes to eutrophication, while little attention has been paid to its control. The iron-based materials are highly efficient in orthophosphate removal from water, while the correlation between their physicochemical properties and selective phosphonate (e.g. Nitrilotri(methylphosphonic acid) (NTMP)) adsorption is still unclear. In this study, Fe3O4 (magnetite), FeOOH (goethite) and Fe2O3 (hematite) with different crystal structures, particle sizes and surface area were synthesized for NTMP adsorption. The physicochemical properties of the three kinds of iron oxides were characterized. The batch experiments were applied to explore the NTMP adsorption and desorption performance. The maximum adsorption capacity of NTMP on Fe3O4, FeOOH and Fe2O3 were 4.14, 1.91 and 0.99 mg-P/g, respectively. Results implied the crystal structure and surface area of iron oxides determined the maximum NTMP adsorption capacity. The NTMP adsorption on the three iron oxides was spontaneous, endothermic and randomness increase. The iron oxides showed high selectivity towards NTMP adsorption in water containing anions, while the co-existing Ca2+ and Mg2+ remarkably increased the adsorption capacity. The successive adsorption-desorption cycles suggested a favorable reusability of the above iron oxides and a high NTMP desorption efficiency. The specific NTMP adsorption capacity followed the sequence of FeOOH > Fe2O3 > Fe3O4, and was highly dependent on surface OH− proportion. The NTMP adsorption mechanism was mainly attributed to inner-sphere complexation. This study provides insights into the iron-based adsorbents design for selective phosphonate adsorption in the future.

Biological arsenite oxidation on iron-based adsorbents in groundwater filters

Iron-based adsorbents are commonly used to remove arsenic (As) from water for drinking water purposes. Here, we study the role of biological As(III) oxidation on iron-based adsorbents in filters and its effect on overall As uptake. A lab-scale filter with iron oxide coated sand (IOCS), a commonly used adsorbent, was operated with water containing As(III) and As(V), while water samples were taken periodically over its height. As(III) oxidation initiated after approximately 10 days and increased to a first order rate constant of 0.09 s−1 after 57 days resulting in full oxidation of As(III) in <50 s. Consequently, the filter shifted from an As(III) to an As(V) adsorbing filter. Oxidation was not observed after inhibiting the microbial activity using sodium azide confirming its biogenic nature. This implies that As(III) oxidizing biomass can grow on iron-based adsorbents in water filters without requiring inoculation. As the experimental conditions were similar to full-scale As treatment plants, we believe that biological As(III) oxidation is widely overlooked in these systems. Occurrence of biological oxidation is, however, beneficial for removal, as at pH <8 the adsorption capacity for As(V) can be up to 10-fold higher than for As(III). With these new insights, arsenic treatment using iron-based adsorbents can be further optimized. We suggest a more robust new design with a biological active As(III) oxidizing top layer and an As(V) adsorbing bottom layer.

Overcoming Fe0/Cr(VI) redox-induced low electron transfer efficiency under neutral pH by iron-based dual active sites-mediated hydrogen atom activation

Efficiently removing hexavalent chromium (Cr(VI)) using iron-based adsorbents under neutral pH conditions continues to pose a challenge. In this study, we constructed nano zero-valent iron (nZVI) supported by carboxylated multi-walled carbon nanotubes (OCNT) composites with iron-based dual active sites through the nitrilotriacetic acid modification (FOC-NA). The acid dissolution experiment, high-resolution transmission electron microscopy (HRTEM), thermogravimetric analyzer (TGA), X-ray photoelectron spectroscopy (XPS), and Raman analysis proved these active sites consisted of iron-carboxylate complex (−COOFe(II)) and OCNT-confined nZVI (Fe0-in-OCNT). The existence of iron-based dual active sites enhanced electron transfer efficiency in Cr(VI) removal under neutral pH conditions. This leaded to a superior adsorption capacity for Cr(VI), as evidenced by a maximum adsorption capacity of 141.29 mg·g−1 at a pH of 6.5. Meanwhile, the formation of a Cr-containing product (−COOFe-O-Cr) on the surface of FOC-NA substantially hindered the re-release of chromium into the environment. Furthermore, this study proposed the significant involvement of active hydrogen atoms (H*) in the reduction of Cr(VI), as confirmed by quenching experiments and analyses using electron spin resonance (EPR), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The formation pathway and energy barrier of H* and the −COOFe-O-Cr complex were analyzed by density functional theory (DFT) calculations. This study provided insights for the rational design of iron-based adsorbents with dual active sites to facilitate the activation of H* for Cr(VI) reduction under neutral pH conditions.

A Review of Theoretical Knowledge and Practical Applications of Iron-Based Adsorbents for Removing Arsenic from Water

Groundwater contamination by arsenic (As) is a serious issue in many countries, particularly in middle- and low-income nations. High concentrations of As in drinking water and groundwater cause serious health problems. Numerous technologies, such as ion exchange, oxidation, coagulation–flocculation, phytoremediation, membrane filtration, and adsorption, have been applied to remove As from the water environment. Among these technologies, adsorption is the preferred method in low- and middle-income countries due to its affordability, high efficiency, and ease of design, operation, and maintenance. Along with this technology, a variety of materials have been developed and investigated for their ability to remove As from water environments, though iron-based adsorbents have been reported to be the most effective. Thus, the aim of this paper is to briefly review the sources of As and the prevalence of As species in water bodies, as well as the currently available technologies for As removal. A detailed analysis of recent studies on iron-based adsorbents used to remove As from aqueous solutions in both laboratory conditions and field conditions is presented.

Adsorption of hydrogen sulfide by iron-based adsorbent derived from fly ash and iron slag.

In this article, an innovative sorbent (Fe-FA) is prepared from fly ash; ferrous sulfate-containing waste slag (FSS), which are industrial wastes; and NaOH by a hydrothermal method at 100°C. As a result, in comparison to several conventional sorbents, such as ZnO, Fe2O3, 13X zeolite, and activated carbon, Fe-FA had the best adsorption performance for H2S adsorption. Fe-FA had not only a higher adsorption capacity (near 150mg/g) but also a longer breakthrough time (near 400min) when gas hourly space velocity was 8000h-1. Then, characterizations of XRD, BET, NH3-TPD, FTIR, and XPS analyzed basic properties of Fe-FA and revealed reasons for the excellent adsorption performance. In general, the excellent adsorption performance of Fe-FA for H2S is mainly due to the high content of iron species (almost 50%) and suitable mesoporous structure in the Fe-FA.

Electrogenerated iron-based adsorbents: A case study of an azo dye removal viewed from a fundamental physico-chemical perspective

The aim of this manuscript was to investigate the electrogeneration of iron-based solids and their use in the adsorption of an azo dye. Experiments of electrochemical generation of iron hydr(oxides) were carried out in a Hoffman cell and in a well-stirred batch reactor at 25 °C. The oxidation of iron metal at the anode and the reduction of water at the cathode were the electrochemical reactions confirmed to occur. A 22 factorial design of experiments was applied to investigate the effect of initial pH and current on the current efficiency for the production of ferrous ion at an electrolyte concentration of 300 g L−1. The current efficiency for Fe2+ was much lower than unity (0.204 ± 0.009) and it was statistically independent of the examined factors (p > 0.05). An approximately 3:1 M mixture of amorphous ferric and ferrous hydroxides was electrogenerated before being possibly converted to dehydrated hydroxides such as magnetite. The iron hydroxides were formed by precipitation reactions of soluble iron species at a rate constant higher than 0.072 ± 0.013 s−1. Additional experiments of electrogeneration of these solid adsorbents at electrolyte concentrations between 250 and 1.5 g L−1 revealed a significant (p ≤ 0.05) decrease in the current efficiency for Fe2+ formation from 0.180 ± 0.006 to 0.118 ± 0.008. Experiments of tartrazine adsorption on the electrogenerated iron oxyhydroxides were carried out batchwise at different initial concentrations of the dye at 25 °C. Electrogeneration of oxyhydroxides and adsorption were described correctly by detailed kinetic models. The crystallinity of the electrogenerated adsorbent was examined by X-ray diffraction analysis, while its specific surface area, pore volume and average pore size were from BET analysis. SEM and EDX analyses were conducted to examine its morphology and elemental composition.

Multi-step biogas quality improving by adsorptive packed column system as application to biomethane upgrading

This study investigates the effect of the specially designed adsorptive packed column system (APCS) in improving the quality of biogas to biomethane purity. The APCS installed with the specially constructed “dispersal star” was operated on biogas from wastewater treatment plant. The four adsorbent packed columns were arranged based on two impregnated and two no-impregnated commercially available active carbons to remove siloxanes, halogenated compounds and volatile organic compounds. The removal performance of ACPS was tested using portable devices along with gas chromatography techniques coupled with different types of detectors. The removal efficiency of total non-silica impurities was obtained at the level of 99.76%, whereas siloxanes were removed entirely. The adsorption affinity of siloxanes in the shape of D4 and D5 was considered by adsorption on high BET surface area adsorbent, while the desulphurisation process was conducted on impregnated active carbons. This study describes the concentrations of silica and non-silica impurities in relation to CHP manufacturers’ limits and biomethane quality. Furthermore, the economical estimation of full-scale APCS was also conducted taking into account the three variants of biogas purity, as well as different types of iron-based adsorbents.

SUSPENSION SORBENTS FOR REMOVAL OF ARSENIC COMPOUNDS AND HUMATES FROM WATER

This paper is devoted to the features of the synthesis and applications of suspension iron(III)-based sorbents in water treatment. The problems of toxic impurities of the drinking water, especially soluble arsenic compounds or different organic disinfection by-products, are very acute not only for Ukraine, but for many other countries too. So, it is very important to find simple and effective method to treat polluted natural waters to the required quality. The comparison of different treatment methods for removal of arsenic compounds and humates was made, as a result of which it was determined that the usage of adsorbents, especially fine particle iron-based sorbents, is very effective in natural organic matter removal and some other pollutants. Fine particle iron-based adsorbents are effective for arsenic removal due to its chemical structure. These materials removed arsenic compounds by chemisorption processes and immobilization of arsenate and arsenite ions in the insoluble form of ferric arsenate. Thus, the aim of the work was to develop the adsorbent for effective removal of arsenic compounds and humates from natural waters. We synthesized 7 suspension iron(III)-based sorbents by homogeneous precipitation from FeCl3 solution by thermal hydrolysis of urea. The efficiency of synthesized samples was checked by adsorption tests (humates and arsenite removal) and capillary suction time test. Iron(III) oxyhydroxide was the main phase of the most effective fine particle adsorbents. Applications on natural water showed that the synthesized iron(III) oxyhydroxide effectively removed arsenic compounds not only from model waters, but also from natural water with reaching of regulatory requirements.

Removal of Cr (VI), As (V), Cu (II), and Pb (II) using cellulose biochar supported iron nanoparticles: A kinetic and mechanistic study

Abstract Magnetic iron-carbon nanoadsorbents synthesized using cellulose biochar as the carbon support have demonstrated great potential for removal of heavy metals (Cr (VI), As (V), Cu (II), and Pb (II)). The effects of initial solution pH, adsorbent dosage, contact time, initial concentration and different iron mass loadings on metal ion adsorption were examined. In an attempt to avoid the capital and operating costs associated with mixing, all the adsorption experiments were conducted under no mixing conditions. Non-linear regression analysis was used to determine kinetic and isotherm parameters. The kinetics of Cr (VI), As (V), and Pb (II) uptake followed pseudo-second order while Cu (II) adsorption best fit pseudo-first order model. Weber intraparticle diffusion model applied to heavy metal uptake revealed multiple rate limiting steps representing different adsorption stages. The adsorption isotherms of all four heavy metals in this study were well fitted by three-, four- and five- parameter models indicating carbon encapsulated iron nanoparticles (CEINPs) possessed a heterogeneous surface. 40 wt% iron loaded CEINPs showed a maximum Langmuir adsorption capacity of 688.6 mg g−1 for the uptake of As (V), a significantly high value when compared to all previously tested iron-based adsorbents in literature. X-ray photoelectron spectroscopy measurements on the CEINPs before and after metal ion adsorption confirmed that heavy metal adsorption process involved interactions with the metallic iron core. Further, a detailed adsorption mechanism for each metal was postulated based on the observed results.

UV-assisted Catalytic Wet Peroxide Oxidation and adsorption as efficient process for arsenic removal in groundwater

Arsenic is a toxic and carcinogenic element present in groundwater as arsenite, As(III) and/or arsenate, As(V), due to natural lixiviation or because of anthropogenic activities. The World Health Organization threshold in drinking water is 10 μg/L, well below the concentration found in the water resources of numerous populations, as in the Duero basin (Spain). As(V) can be easily removed by adsorption onto iron-based adsorbents, whereas As(III) is harder to remove. Therefore, in this work we propose the use of ilmenite (FeTiO3), a low-cost catalyst, as both photocatalyst and adsorbent in the UV-A assisted Catalytic Wet Peroxide Oxidation process. The main aim of this technology is to oxidize arsenite into arsenate, for its subsequent adsorption onto the Fe sites of the catalyst. This technology has proven to be effective for the oxidation and removal of 10 mg/L As(III) working at 1000 mg/L ilmenite, 60 mg/L H2O2, 0, pH0: 7 and room temperature (25 °C), in both ultrapure water and groundwater collected from Lastras de Cuéllar (Segovia, Spain). Furthermore, we propose a complete kinetic model which comprises the H2O2 decomposition, As(III) oxidation and As(V) adsorption, which is in agreement with the experimental data.

Removal of mercury by magnetic nanomaterial with bifunctional groups and core-shell structure: Synthesis, characterization and optimization of adsorption parameters

In this study, a magnetic nanomaterial CoFe2O4@SiO2@m-SiO2-SH/NH2 with bifunctional groups and core-shell structure was successfully synthesised and employed to remove mercury ions [Hg(II)] for enhancing the corrosion resistance of magnetic iron-based nanomaterials. Furthermore, the grafting conditions were improved for amino (NH2) and thiol groups (SH), while increasing the capacity of iron-based adsorbent. The grafting of NH2 and SH was conducted through a relatively safe, mild and facile hydrothermal method at low temperature (353 K) without using any toxic and harmful solvents. Adsorption-related variables including solution pH, adsorbent dosage, initial concentration (C0) and reaction temperature were studied by response surface methodology analysis, wherein maximum adsorption capacity was used as a response variable. The optimal results indicate that the maximum adsorption capacity of 504.34 mg Hg(II)/g was obtained at a pH of 7.2. The magnetic nanoparticles exhibited high adsorption capacity for Hg(II) ions, i.e., 464.7 mg/g, by pseudo-second-order fitting. In addition, the maximum adsorption capacity calculated from Langmuir fitting was 517.4 mg/g at pH 7. Thermodynamic data showed that the adsorption of Hg(II) was endothermic and spontaneous. Moreover, the adsorption capacity of Hg(II) ions still reached over 300 mg/g after five adsorption–desorption cycles. Finally, the probable adsorption mechanism was discussed.

Facile synthesis of chrysanthemum-like mesoporous α-FeOOH and its adsorptive behavior of antimony from aqueous solution

A chrysanthemum-like mesoporous α-FeOOH was synthesized by hydrothermal method and was applied to remove Sb(V) from Sb(V)-contaminated aqueous solution. XRD, ATR-FTIR, and Raman Spectrum characteristics indicated that the pure α-FeOOH phase had been successfully synthesized. The morphology and pore structure were investigated by FE-SEM and N2 adsorption–desorption isotherms. The Sb(V) adsorption kinetics, isotherms, and mechanism on mesoporous α-FeOOH were studied. The results showed that Sb(V) adsorption on mesoporous α-FeOOH well-fitted pseudo-second-order kinetics and the maximum Sb(V) adsorption capacity of mesoporous α-FeOOH is 102.67 mg·g−1, which is much higher than most of iron-based adsorbents. The negative value of ΔG° and ΔH° indicated that the Sb(V) adsorption process on the mesoporous α-FeOOH was a spontaneous and exothermic. The adsorption mechanism can be attribute to the surface complexation between Sb(V) and the mesoporous α-FeOOH. These findings suggest that the mesoporous α-FeOOH is a potential adsorbent for Sb(V) removal from aqueous solution.

Highly efficient recovery and clean-up of four heavy metals from MSWI fly ash by integrating leaching, selective extraction and adsorption

Municipal solid waste incineration (MSWI) fly ash contains significant amounts of heavy metals (e.g., Cd, Cu, Pb and Zn) and is therefore considered to be a hazardous waste requiring proper treatment prior to its disposal. In this work, an integrated hydrometallurgical process for treatment of MSWI fly ash was evaluated. Valuable metals, e.g. Cu and Zn, were first recovered by combining leaching and extraction sequentially. In the next step, the t removal of Cd and Pb from the remaining leachate using four types of iron-based adsorbents was evaluated. The leaching was optimized with respect to pH, leaching time and liquid to solid ratio. A test done under optimal conditions gave metal releases of 100% and 80% for Cu and Zn as well as 100% and 85% for Cd and Pb, respectively. The resulting leachate was contacted with organic phases based on kerosene containing the extractants LIX860N–I for Cu extraction and Cyanex 572 for Zn extraction in two consecutive steps. Efficient extractions were achieved, thus demonstrating that the combination of leaching and extraction can be successfully used for the recovery of Cu and Zn. Adsorption of heavy metal ions on various iron based sorbents to detoxify the aqueous effluent from the extraction showed good removal efficiency (more than 95%) for both Cd and Pb. The results of this study show that the proposed integrated process is a promising tool that can be used in the strategy for metal recovery and detoxification of MSWI fly ash.

Study on iron-based adsorbents for alternating removal of H2S and O2 from natural gas and biogas

This study deals with the development of iron oxide/hydroxide adsorbents for the alternating removal of H2S and O2 from natural gas and biogas. The considered procedure initially implies the chemisorption of H2S. In the second step, O2 is removed by reaction with the H2S-treated substrate accompanied by regeneration of the adsorbent. 35 different iron-based samples were physical-chemically characterized and tested towards H2S/O2 break through behavior and adsorption capacity to evaluate structure-performance correlations. It was derived that high BET surface area, high proportion of meso and micro pores, small average pore diameter, low crystallinity and high number of Bronsted acid sites are crucial properties of the adsorbents. As a consequence, Fe(OH)3 and α-FeOOH revealed highest efficiency for the successive adsorption of H2S and O2, while α-Fe2O3 provided rather low performance.Mechanistic investigations were carried out with α -FeOOH and α -Fe2O3 indicating rapid dissociation of H2S on α -FeOOH, while slow molecular adsorption prevailed on α -Fe2O3. With proceeding H2S exposure, the adsorbents were partially transformed into sulfide and sulfate species with some formation of elemental sulfur. In subsequent reaction with O2, the H2S-exposed samples were re-oxidized under partial restructuring, whereas elemental sulfur and sulfate entities were additionally produced.Finally, the concept of the alternating adsorption of H2S and O2 on best α -FeOOH substrate was technically evaluated in a biogas pilot plant. The investigations showed efficient conversion of H2S for 40–100 h, while subsequent O2 conversion was achieved for ca. 5.5 h.

Comparison of different iron oxide adsorbents for combined arsenic, vanadium and fluoride removal from drinking water

Contamination of groundwater by arsenic due to natural processes is rather common worldwide and hinders its use for drinking water supply. In many cases, arsenic contamination is found together with high levels of vanadium and fluoride. Therefore, more than one type of treatment is required to reduce concentrations of all these contaminants below non-hazardous levels so to make the source drinkable. The present study investigated the uptake capacity of arsenic, vanadium and fluoride by three iron-based adsorbent media differing for particle size, iron content and specific surface. The aim of the treatment was to achieve the maximum allowable concentration set on drinking water by the law. The removal efficiency was evaluated in single and binary contaminated solutions. All the tested adsorbents demonstrated an efficient and rapid removal process of both arsenic and vanadium in the single and binary solutions, with a higher adsorption capacity for vanadium; by contrast, they were unable to achieve an appreciable reduction in fluoride concentration. The particle size showed to have the highest effect on the removal rate. The best kinetic and isotherm models and the related parameters were determined for each condition. In the binary solutions, the presence of vanadium hindered the uptake of arsenic, whereas fluoride did not have any effect. The results obtained showed that the iron-based adsorbents tested in the present study can be successfully applied for the treatment of drinking water contaminated by arsenic and vanadium, whereas a different medium or process needs to be adopted for the removal of fluoride.

Pre-deposition of iron-based adsorbents on the removal of humic acid using ultrafiltration and membrane fouling

The effect of three iron-based adsorbents pre-depositing on ultrafiltration membrane for humic acid (HA) removal and membrane fouling was investigated. The result showed that pre-depositing adsorbents on membrane could not only reduce membrane fouling but also enhance HA removal. The flux was related to the adsorbent dosage and the optimal dosage for predeposition was 35.0g/m2. The dissolved organic carbon (DOC) removal of HA was 38.3%, 67.3% and 41.1% respectively when pre-deposited 35.0 g/m2 FeOxHy, MnFe2O4 and Fe3O4 on membrane. Different adsorption effect of adsorbents on HA contributed to increasing of the flux at different level. Zeta potential of three adsorbents all decreased after adsorbed HA. The adsorption capacity of the three adsorbents was FeOxHy > MnFe2O4 > Fe3O4. Atomic Force Microscopy (AFM) measurement showed the thickness of pre-deposition layers formed by different adsorbents was different. The scanning electron microscope (SEM) detection showed the morphology and compactness of pre-deposition layers formed by different adsorbents was different.

Biogenic iron oxides for phosphate removal

ABSTRACTBiogenic iron oxides (BioFeO) formed by Leptothrix sp. and Gallionella sp. were compared with chemically formed iron oxides (ChFeO) for their suitability to remove and recover phosphate from solutions. The ChFeO used for comparison included a commercial iron-based adsorbent (GEH) and chemically oxidized iron precipitates from groundwater. Despite contrary observations in earlier studies, the batch experiments showed that BioFeO do not have superior phosphate adsorption capacities compared to ChFeO. However, it seems multiple mechanisms are involved in phosphate removal by BioFeO which make their overall phosphate removal capacity higher than that of ChFeO. The overall phosphate removal capacity of Leptothrix sp. deposits was 26.3 mg P/g d.s., which could be attributed to multiple mechanisms. This included adsorption on the solid phase (6.4 mg P/g d.s.) as well as removal via precipitation and/or adsorption onto suspended complexes released from the BioFeO of Leptothrix sp. (19.6 mg P/g d.s.). Only a very small part of phosphorus (0.3 mg P/g d.s.) was retained in the Leptothrix sp. sheats during bacterial growth. Deposits of Gallionella sp. had an overall phosphate removal capacity of 39.6 mg P/g d.s. Significant amounts of phosphate were apparently incorporated into the Gallionella sp. stalks during their growth (31.0 mg P/g d.s.) and only one-fifth of the total phosphate removal can be related to adsorption (8.6 mg P/g d.s.). Their overall ability to immobilize large quantities of phosphate from solutions indicates that BioFeO could play an important role in environmental and engineered systems for removal of contaminants.

APPLICATION OF IRON-BASED ADSORBENT (FEOOH) TO REMOVE HYDROGEN SULFIDE (H2S) FROM BIOGAS

Biogas generated during the anaerobic digestion of piggery wastes is considered as one of the renewable energy sources. This biogas is methane-rich, based on a typical composition of 60 - 70 % methane (CH4). However, trace amounts of undesirable compounds, such as hydrogen sulfide (H2S) is also present, which hinder their use as it is very toxic and corrode the equipment. In this study, a lab-scale adsorption system was conducted to removal H2S from biogas collected at Thanh Hung pig farm (Thanh Oai district, Hanoi). The initial biogas contained high CH4 concentration of 72 %, and the H2S concentration was about 1995 ppm. The iron-based adsorbent (FeOOH) with the particle size of 0.50-1.18 mm was used for H2S purification. The system was operated continuously at various biogas flow rates from 0.5 to 3 L/min. Breakpoint of FeOOH appeared after 1,038 min. The adsorption capacity was estimated up to 0.18 g H2S/g FeOOH. A longer empty bed contact time increased the amount of H2S that was adsorbed up until the time of breakpoint. During operation, the temperature in the air and in biogas was varied insignificantly in the range of 29 to 32 oC. However, the humidity was much different between in the ambient air (56 %) and in biogas (87 %). In conclusion, FeOOH has high capacity for H2S purification to produce high quality purified biogas with H2S concentration of below 100 ppm which could be used for electrical generation.