Papers by Keyword: Pretreatment

Abstract: Spent catalysts contain metals that have a high added value. From all metals, lanthanum has attracted a lot of attention due to the growing demand in the high-tech. The spent catalyst of the hydrotreatment unit is a material composed of lanthanum-enriched matrix of amorphous aluminosilicates. The experiment was carried out with a spent catalyst with a constant particle size of 90 μm. The treatments were obtained applying of two level factorial design to investigate the effect of following factors: temperature (20 - 60 °C), nitric acid concentration (3 - 6 M), leaching time (1 - 4 h) and percent solids (10 - 20 %). The research is carried out in two steps process: pretreatment of the catalyst and leaching with nitric acid. The leaching results show a yield of lanthanum of 99.44% using the following conditions: temperature (20 °C), nitric acid concentration (3M), leaching time (1 h), percent solids (20%) and 300 rpm. The principal analysis of the spent catalyst was carried out using the X-Ray Fluorescence (XRF) technique, 3.08%, while the percentage of lanthanum recovery in the extract, washing and refining was carried out using the Inductive Coupling Plasma (ICP) technique.

Abstract: Wood is widely used in a construction both in the form of integral components and as a part of various products or wood filled composites. However, while using wood in the production of building materials, it is necessary to consider a set of factors, as along with the valuable properties (low average density, ease of handling, etc.) it has a number of negative qualities, which complicate production of construction materials of desirable quality. The results of researches of thermal modification of wood raw materials in production of construction materials are provided in the article. It is established that as the result of change of chemical composition of thermo wood treated at temperatures of 453 K - 493 K, the water carrying out function of material decreases, despite considerable reduction of density. Besides in case of increase in the heat treatment value of wetting angle grows by 25%, and equilibrium humidity of wood decreases. Thus, the results of the conducted researches give the chance to obtain the environmentally friendly wood filled construction materials with low water absorption and hygroscopicity that allows assuming a possibility of creation of materials with the raised operational characteristics.

Abstract: Intensive cutting down of trees to replenish the reserves of business wood exhausts wood stocks in traditional logging areas, leads to the decrease in the areas of forest plantings.\, and ecological disruption. Now there are real opportunities to reduce the consumption of traditional forest resources thanks to fuller use of forest products, low-grade wood, and waste of sawmilling and a woodworking for the production of composite materials. In this regard the results of the research on the possibility to use low-grade wood for production of composite materials are given in this work. At the same time a natural filler is subjected to preliminary high-frequency plasma processing. It is established that this type of processing of wood raw materials leads to improvement of its separate properties: wettability of material and adhesion to cement knitting increases. At the same time the increase in wettability of wood samples is directly proportional to the capacity and duration of high-frequency plasma processing. It is proved that preliminary modification of wood filler during production of cement wood results in the increase in its durability during operation in dry conditions.

Abstract: A sulphide concentrate containing 31.4% total sulphur (in which 30.7% was sulphidic), 31.8% iron, 8.0% arsenic, 18.5 g/t gold and 32.9 g/t silver finely disseminated in pyrite and arsenopyrite as the most essential components was subjected to microbial pretreatment to expose the precious metals from the sulphide matrix. Three different types of microbial cultures were tested for their ability to oxidize the sulphides and to expose the precious metals for the subsequent chemical leaching: mesophilic chemolithotrophic bacteria with a temperature optimum for their growth and activity at about 32 – 37°C, moderate thermophilic bacteria with the relevant optimum at 53 – 59°C, and hyperthermophilic archaea at 75 – 84°C. The microbial pretreatment of the concentrate was carried out in reactors with mechanical stirring and enhanced aeration by air enriched in CO_2. It was found that sulphide oxidation of about 40 – 45 % was sufficient for achieving gold extraction higher than 90% during the subsequent leaching of the pretreated concentrate by different gold-solubilizing reagent (cyanide, thiourea, thiosulphate). The highest rate of sulphide oxidation was achieved by a mixed culture of hyperthermophilic archaea at 82°C but at relatively low pulp densities (within 7 – 9%). At higher pulp densities (within 10 – 25%) the highest rates were achieved by means of moderate thermophilic bacteria at 57 – 59°C.

Abstract: This work provides an overview of organosilane metal pretreatments with a focus on water-based systems. Furthermore, this work aims to point out the key notes for organosilane technology to be fully transferred to industry.

Abstract: Cutting tools of WC-Co are widely used in cutting field. Nevertheless, its wear resistance and lifetime are not qualified for the high performance cutting. Therefore, diamond films are deposited on WC-Co substrates to overcome its disadvantages. In this paper we investigate the effects of the pretreatment on substrates and as-deposited WC-Co samples by using a hot filament chemical vapor deposition (HFCVD) reactor. Prior to deposition, the WC-Co substrates were submitted to surface roughening by Murakami reagent and to surface binder removal by Caro’ acid with varied durations. Surface roughness R_a determined by AFM varied from 110 to 279 nm. The diamond films are characterized by scanning electron microscopy (SEM) and Raman spectroscopy, whose results present a sharp peak at 1336 cm^-1 indicating sp³ diamond. The adhesion between the diamond films and substrates was evaluated by pull-off tests with the highest adhesion strength is 26.92 MPa. Cracked interface is characterized between diamond films and substrates, using SEM and energy dispersive spectroscopy (EDS) to analyze the adhesion performance.

Abstract: Zirconium based metal pretreatments have become widely used in recent years as a substitute for phosphate deposition on steel alloys and for chromate on aluminum alloys in industrial applications. The choice of a zirconium based intermediate layer follows from its ecologic sustainability − decreased water and energy consumption, vehicle weight reduction, and low byproduct generation during processing. Here we describe our investigations of a characterization method of converted metal oxide thin films deposited by a plasma method. The thin film composition was characterized by Rutherford Backscattering Spectroscopy (RBS) and Energy Dispersive Spectroscopy (EDS) before and after conversion by a zirconium-based pretreatment, revealing the formation of zirconia after treatment. The corrosion mechanism of the deposited metal oxide films was investigated using electrochemical analysis, confirming the susceptibility of the film to corrosion and the applicability of corrosion investigations. The results pointed to a better performance of the RBS in comparison to EDS.

Abstract: As the fossil resource supply situation become more serious and the increasingly serious environment problems, the development of new carbon resource utilization has become an urgent task. Plant cellulose is the most abundant natural resource, which is renewable, nontoxic and degradable, has been paid much attrition by researchers of many countries. This paper reviews recent progress in plant cellulose extract and modification, especially in chemical modification of cellulose derivatives. And the article described cellulose modification technology about pretreatment. The applications of modified cellulose in the field of environmental protection, pharmaceutical, paint and other industries introduced as well. Finally, the current research hotspots of cellulose modification technology were prospected.

Abstract: Aluminum dross is the staple solid waste in electrolytic aluminum industry. Taking full advantage of the aluminum dross is of great significance for controlling environmental pollution and saving resource. In this work, brown fused alumina is successfully prepared using aluminum dross as raw material through different pretreatments for aluminum dross. The results show that the brown fused alumina product is comprised of α-Al₂O₃ (ca.95%), NaCl (ca.1~3%) and CaF₂ (ca.1~3%), and contents of the other components are as follows: MgO 0.33%, SiO₂ 1.12%, Fe₂O₃ 0.41%, CaO 0.58%, TiO₂ 0.13%, K₂O 0.05%, Na₂O 0.87% and V₂O₅ 0.92%. This quality of the resulting brown fused alumina can fully meet the national standards of China (GB/T 2478-2008).

Abstract: Black tilapia (Oreochromis mossambicus) fish skins are good alternatives sources of gelatin. Vast variations in extraction procedures affect the properties of fish gelatin such as yield and gel strength. Thus, this study explores the effect of pretreatment durations on the properties of black tilapia skin gelatin. Gelling properties such as gel strength (bloom value) of the gelatin samples had been determined. Highest gel strength had been detected for gelatin treated at 24 h (390.1 g), followed by 16 h (287.1 g) and 8 h (141.2 g). In contrast, gelatin treated at 24 h indicates lower yield on wet weight basis (14.12 %) than those treated at 16 h (14.96 %) and 8 h (16.90 %). The possible interactions and characteristics between the functional groups in the gelatin samples have also been perceived via Fourier Transform Infrared Spectroscopy (FTIR) analysis.