Biogas derived from anaerobic digestion of biological wastes has been extensively used for heating purposes and/or electricity generation. Presence of hydrogen sulfide (H2S) in biogas affects engine performance adversely, thus reducing H2S content is a valuable part in practical application before utilizing biogas. Adsorptive separation is very appealing due to being an economical and effective method including the use of iron oxide based adsorbents. Pelletization of iron oxide adsorbents has never been reported among the adsorbents described to date. Therefore, H2S capture in two iron oxides (ferric oxide (Fe2O3) and magnetite (Fe3O4)) was experimentally investigated to determine technical feasibility of shaping pellets based on active iron oxide sorbent in removing H2S from a simulated gas stream (0.35 vol.% H2S balanced in N2). Many factors affecting the behavior of gas adsorption such as gas in-flow rate, adsorption temperature, binder loadings and textural characteristics were considered. The pellet strengths were also undertaken using a bulk crushing strength analyzer. The results indicated that higher temperature favors the diffusion of H2S molecules from the surface into the bulk of iron oxides. The H2S-sorption capacity of Fe3O4 sorbent was higher than that of Fe2O3 sorbent corresponding with the different pore volume and surface area in each adsorbent. With the same active Fe3O4, the extruded pellet produced with starch binder showed the excellent H2S uptake and crushing resistance. The higher gas in-flow rate had positive impact to contacting efficiency and mass transfer of solid and gas phase. The adsorbed H2S gas can be readily desorbed from the pellets with the desorption temperature below 60°C and the H2S-sorption capacity was consistent over repeated cycles. The pellets can be reused several times for consecutive adsorption/desorption cycles, without loss of performance in a large-scale reactor and therefore represent serious candidates for use in commercial absorbers.

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The effects of current density and Ti particle loading in a plating bath on the morphology and hardness of Ni-Ti composite coatings via an electrochemical-codeposition process were investigated. The Ti-reinforced Ni-matrix composite coatings were codeposited on copper substrates using a Ni-ion electrolytic solution stably suspended with -45 micron Ti particles. Within the current studied range, the coatings' Ti contents are in the range between 46 and 62 at.%. The morphology appeared to vary with current density. Structures of the Ni-Ti composite coatings produced under low current density conditions revealed denser structures, which is in contrast to the more porous structures noted in the coatings produced under high current density. An initial increase of current density from 100 to 150 mA/cm 2 also tends to raise Ti coating content. The reinforcement of Ti particles in the coatings also increased their hardness, which is attributed to the possible role of the embedded Ti particles in hindering matrix deformation. The effect of Ti loading on the coating's Ti contents was not significant under conditions used in the present study.Keywords: electrochemical codeposition, composite coatings, Nickel-Titanium, morphology, hardness Badano wpływ gęstości prądu i zawartości cząstek Ti w kąpieli galwanicznej na morfologię i twardość elektrochemicznie współosadzanych powłok kompozytowych Ni-Ti. Kompozytowe powłoki niklowe zbrojone cząstkami Ti zostały współosadzone na powierzchniach miedzianych z kąpieli elektrolitycznej zawierającej jony Ni i 45 mikronowe cząstki Ti tworzące stabilną zawiesinę. Zawartość Ti wbudowanego w powłoki wahała się w granicach 46-62 at.%. Morfologia powłok zmienia się wraz ze zmianą stosowanej gęstości prądu. W przypadku kompozytowych powłok Ni-Ti wytwarzanych przy niskich gęstościach prądu stwierdzono bardziej zwarte struktury, w przeciwieństwie do bardziej porowatych struktur stwierdzonych w przypadku powłok wytwarzanych przy wysokich gęstościach prądu. Początkowy wzrost gęstości prądu od 100 do 150 mA/cm 2 również powoduje podniesienie zawartości Ti w powłokach. Ze wzrostem zawartości Ti wzrasta również twardość powłoki, co można przypisać roli osadzonych cząstek Ti utrudniających odkształcenie osnowy. W warunkach stosowanych w tej pracy wpływ zawartości Ti w kąpieli na zawartość Ti w powłokach nie był znaczący.

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