Muffle Oven Research Articles

Thermal kinetics of PFAS and precursors in soil: Experiment and surface simulation in temperature-time plane

Per- and polyfluoroalkyl substances (PFAS) are chemically and thermally stable due to the presence of carbon-fluorine (C–F) bond in their molecular structures, hence have been previously formulated as firefighting ingredients. During the firefighting process, however, owing to the high temperature, PFAS can be potentially degraded, particularly for PFAS precursors that contain non-C-F bonds, which is studied herein by exposing PFAS-contaminated soil in a muffle furnace oven. Different temperatures and time intervals are applied to the real soil sample to mimic the firing process and to evaluate the degradation and conversion of PFAS. This thermal treatment can not only degrade precursors (e.g. 6:2 fluorotelomer sulphonate), but also degrade perfluoroalkyl carboxylates (PFCA, e.g. perfluorooctanoic acid PFOA) and perfluoroalkyl sulfonates (PFSA, e.g. perfluorooctane sulfonate PFOS). The concentration dependence of the PFAS on temperature and time is fitted using a 2D Gaussian surface to simulate the complex thermal kinetic, and to compare with the traditional approach such as thermogravimetric analysis (TGA) (1D dependence on temperature only). The 2D simulation can directly visualise the thermal kinetic of individual or sum PFAS in the complex temperature-time plane, which depends on the sample background and particularly on the coexist PFAS precursors. Overall, this study provides a simple approach to monitor and optimise the thermal treatment of the PFAS-contaminated soil.

Potential of Flax Shives and Beech Wood-Derived Biochar in Methylene Blue and Carbamazepine Removal from Aqueous Solutions.

Flax shives and beech wood residues represent biomass streams that are abundant in Northwest Europe. These primary feedstocks were evaluated for their suitability to produce biochar as a low environmental-impact adsorbent. The efficacy of the produced biochars was tested by their adsorption capacity towards methylene blue (MB). A series of adsorption tests with carbamazepine is also presented, focusing on the better performing beech wood biochar. Post treatment of the biochars with citric acid (CA) and oxidation of the surface by heating at 250 °C in a muffle oven were carried out to enhance the adsorption capacities of both flax shives biochar (FSBC) and beech biochar (BBC). The resulting physicochemical characteristics are described. The thermally treated biochars have specific surface areas of 388 m2·g−1 and 272 m2·g−1 compared to the untreated biochars with 368 and 142 m2·g−1 for BBC and FSBC, respectively. CA treatment leads to enhancement of the oxygenated surface functional groups and the adsorption capacities of both studied biochars. The non-linear Langmuir and Freundlich models show the best fit for both the isotherm data for MB and the CMZ adsorption with a good correlation between the experimental and calculated adsorption capacities. The effect of adsorbent dosages and initial concentrations of MB and CMZ on the adsorption efficiency is discussed. It can be concluded that beech biochar is a very promising pollutant adsorbent only requiring a mild, low-cost, and low-environmental impact activation treatment for best performance.

Extraction and Characterization of Biogenic Silica Obtained from Selected Agro-Waste in Africa

Increased amounts of available biomass residues from agricultural food production are present widely around the globe. These biomass residues can find essential applications as bioenergy feedstock and precursors to produce value-added materials. This study assessed the production of biogenic silica (SiO2) from different biomass residues in Africa, including cornhusk, corncob, yam peelings, cassava peelings and coconut husks. Two processes were performed to synthesize the biogenic silica. First, the biomass fuels were chemically pre-treated with 1 and 5% w/v citric acid solutions. In the second stage, combustion at 600 °C for 2 h in a muffle oven was applied. The characterization of the untreated biomasses was conducted using Inductively coupled plasma—optical emission spectrometry (ICP-OES), thermal analysis (TG-DTA) and Fourier-transform infrared spectroscopy (FTIR). The resulting ashes from the combustion step were subjected to ICP, nitrogen physisorption, Energy dispersive X-ray spectroscopy (EDX) as well as X-ray diffraction (XRD). ICP results revealed that the SiO2 content in the ashes varies between 42.2 to 81.5 wt.% db and 53.4 to 90.8 wt.% db after acidic pre-treatment with 1 and 5 w/v% acid, respectively. The relative reductions of K2O by the citric acid in yam peel was the lowest (79 wt.% db) in comparison to 92, 97, 98 and 97 wt.% db calculated for corncob, cassava peel, coconut husk and cornhusk, respectively. XRD analysis revealed dominant crystalline phases of arcanite (K2SO4), sylvite (KCl) and calcite (CaCO3) in ashes of the biomass fuels pre-treated with 1 w/v% citric acid due to potassium and calcium ions present. In comparison, the 5 w/v% citric acid pre-treatment produced amorphous, biogenic silica with specific surface areas of up to 91 m2/g and pore volumes up to 0.21 cm3/g. The examined biomass residues are common wastes from food production in Africa without competition in usage with focus application. Our studies have highlighted a significant end-value to these wastes by the extraction of high quality, amorphous silica, which can be considered in applications such as catalyst support, construction material, concrete and backing material.

Gas Sensing Properties Comparison between SnO2 and Highly Antimony-Doped SnO2 materials

IntroductionGas sensors are widely applied to monitor the combustible and harmful gases which can be detrimental to safety, health and environmental protection. SnO2, a wide gap semiconductor, is one of the most promising gas sensor material because of high chemical stability and low fabrication cost[1].While due to the drawbacks of SnO2 working as gas sensing material, such as low selectivity and high working temperature, doping by noble or transition metals is a particularly efficient way to improve its sensing properties[2]. SnO2 doped by antimony (SnO2/Sb) is a typical n-type oxide material, which has high electrical conductivity and thermal stability.Materials and MethodThe impacts of Sb doping (10 wt.% doping content) on morphology, nanostructure of commercial SnO2 were investigated by scanning electron microscopy (SEM) and x-ray diffraction (XRD) techniques. The samples were added into a composed solution mixed with glycol ether as wetting agent and an acrylic resin, and then screen printed onto alumina substrates, where Au was applied as interdigitated electrodes on front-side, and the back-side was equipped with a heater to provide with working temperature. In the last, the screen-printed films were treated at 180 ˝C in a muffle oven for 12 h in air to obtain the thermal stabilization[3]. The response values (R) were obtained by the equation (1), hence Ra is the resistance while exposed to the dry air, and Rg is the resistance while exposed to target gas, which were measured by home-made gas sensing system. The samples under different temperatures were named as SnO2-x and SnO2/Sb-x (x=300°C, 350°C, 400°C and 450°C). The gas sensing properties dependence of samples on different temperatures under acetone gas condition was clarified, and the relationship between doping and selectivity of samples under different target gases at 350°C were demonstrated. The results about high antimony doping content at different working temperatures and target gas situations were investigated in this work. Results and Conclusions The SEM reveled that antimony doping SnO2 contributed to harshen the surface of SnO2, which is beneficial to increase the specific surface area and the adsorption efficiency to target gases, as shown in Fig. 1.[4]. XRD characterization shows that no other phases such as SnO and Sn3O4 were detected, which means the high purity of the SnO2[5]. Meanwhile, Sb doping did not change the tetragonal structure of SnO2, but it distinctly affected the preferred (110), (101) and (211) orientation growth, which can be detected in Fig.2. Furthermore, the gas sensing properties between pure SnO2 and SnO2/Sb were compared at different working temperatures and under different target gases environment. The measurement results in Fig.3 (a) and (b) demonstrated that the response of SnO2 and SnO2/Sb reached highest value at 350°C. While SnO2 and SnO2/Sb showed abnormal trend at 450°C that is conducive to oxygen atoms insertion into the crystal structure[6]. Specifically, SnO2/Sb showed p-type shape response at 450°C, maybe it is because antimony doping decreased the grain size of SnO2 so that the whole grains were fully depleted. In the beginning of reaction with target gas, the concentration of O2 on the surface of SnO2/Sb decreased and the conductance increased. Whilst, when the depletion zone was smaller than the grain size, the conductance decreased a lot. When stopping injection of target gases, the trend processed reversely [6]. Otherwise, this p-type shape response of SnO2/Sb can only be observed under acetone environment at 450°C, which can be used to distinguish acetone among other gases. From Fig.4 (a) and (b), it can be found that Sb doping facilitated SnO2 the highest response to acetone among H2S, ethylene, ethanol, and CO environments, which means antimony doping can improve the selectivity of SnO2.

New approach for inert filtering media modification by using precipitates of deironing filters for underground water treatment.

The anthracite granules were coated with iron oxide by a solution combustion synthesis method in a muffle furnace oven. As for iron precursor, an iron-containing precipitate of water treatment plants was used. The influence of four different reducing reagents on surface phase composition and properties of the modified materials was investigated. Obtained samples were investigated using different diffraction and spectroscopic methods. Using the solution combustion synthesis method, anthracite granules formed fine dispersed and crystalline structures of iron oxides on their surface with the iron content up to 40.7wt%. This had a positive effect on the catalytic capacity of the material for deironing of underground water as well as for the increase in specific surface area. The catalytic properties of the obtained samples and the effectiveness of deferrization of groundwater were investigated. The use of tested materials makes it possible to reduce of catalytic layer height of the filter media from 50 to 20cm for the filtration rate 12m/h and enhance the treatment efficiency during the first start-up of filters after regeneration up to 3 times.

Gas Sensing Properties Comparison between SnO2 and Highly Antimony-Doped SnO2 Materials

Introduction Gas sensors are widely applied to monitor combustible and harmful gases which can be detrimental to safety, health and environment. SnO2, a wide gap semiconductor, is the most promising gas sensor material because of high chemical stability and low fabrication cost[1].While due to the drawbacks of SnO2 working as gas sensing material, such as low selectivity and high working temperature, doping by noble or transition metals is a particularly efficient way to improve its sensing properties[2]. SnO2 doped by antimony (SnO2/Sb) is a typical n-type oxide material, which has high electrical conductivity and thermal stability. Materials and Method The impacts of Sb doping (10 wt.% doping content) on morphology, nanostructure of commercial SnO2 were investigated by scanning electron microscopy (SEM) and x-ray diffraction (XRD) technique. The samples were added into a composed solution mixed with glycol ether as wetting agent and an acrylic resin, and then screen printed onto alumina substrates, where Au was applied as interdigitated electrodes on front-side, and the back-side was equipped with a heater to provide with working temperature. In the last, the screen-printed films were treated at 180 °C in a muffle oven for 12 h in air to obtain the thermal stabilization[3]. The response values (R) were obtained by the equation (1), hence Ra is the resistance while exposed to the dry air, and Rg is the resistance while exposed to target gas, which were measured by home-made gas sensing system. The samples under different temperatures were named as SnO2-x and SnO2/Sb-x (x=300°C, 350°C, 400°C and 450°C). The gas sensing properties dependence of samples on different temperatures under acetone gas condition was clarified, and the relationship between doping and selectivity of samples under different target gases at 350°C were demonstrated. The results about high antimony doping content at different working temperatures and target gas situations were investigated in this work. Results and Conclusions The SEM reveled that antimony doping SnO2 contributed to harshen the surface of SnO2, which is beneficial to increase the specific surface area and the adsorption efficiency to target gases, as shown in Fig. 1.[4]. XRD characterization shows that no other phases such as SnO and Sn3O4 were detected, which means the high purity of the SnO2[5]. Meanwhile, Sb doping did not change the tetragonal structure of SnO2, but it distinctly affected the preferred (110), (101) and (211) orientation growth, which can be detected in Fig.2. Furthermore, the gas sensing properties between pure SnO2 and SnO2/Sb were compared at different working temperatures and under different target gases environment. The measurement results in Fig.3 (a) and (b) demonstrated that the response of SnO2 and SnO2/Sb reached highest value at 350°C. While SnO2 and SnO2/Sb showed abnormal trend at 450°C that is conducive to oxygen atoms insertion into the crystal structure[6]. Specifically, SnO2/Sb showed p-type shape response at 450°C, maybe it is because antimony doping decreased the grain size of SnO2 so that the whole grains were fully depleted. In the beginning of reaction with target gas, the concentration of O2 on the surface of SnO2/Sb decreased and the conductance increased. Whilst, when the depletion zone was smaller than the grain size, the conductance decreased a lot. When stopping injection of target gases, the trend processed reversely [6]. Otherwise, this p-type shape response of SnO2/Sb can only be observed under acetone environment at 450°C, which can be used to distinguish acetone among other gases. From Fig.4 (a) and (b), it can be found that Sb doping facilitated SnO2 the highest response to acetone among H2S, ethylene, ethanol, and CO environments, which means antimony doping can improve the selectivity of SnO2.

Use of mufla oven calcination method in oil quantification of chia seeds

Chia (Salvia hispanicaL.) is an annual herbaceous plant considered as natural omega-3 fatty acids source. To quantify this oil in seeds, a time-consuming method involving financial costs with chemical reagents is used. The objective of this work was verifying existence of correlation between the quantification of oil in chia seeds by means of the Soxhlet method with the ash mass of these seeds obtained by calcination in a muffle oven. For this, samples of chia seeds and the oil quantified by Soxhlet were collected. The same samples were calcined in ash. The simple correlation test was performed, obtaining linear regression. To method validation, a completely randomized design experiment was carried out. The treatments were to quantify the oil by the Soxhlet method and calcination in the muffle using the equation obtained. The objective was to verify the existence of correlation between the oil content of chia seeds, obtained by the Soxhlet method with ash content obtained after burning in the muffle and, therefore, the validation of this method of determination. There is a significant positive correlation between the oil content obtained by Soxhlet method and the ash mass of chia seed. By equation Y = -2.5319x + 16.518, it was noted that it is feasible to quantify the oil content

Facile preparation of high conductive silver electrodes by dip-coating followed by quick sintering.

With polyol-synthesized silver nanoparticles (AgNPs) as raw materials, the silver electrodes with high conductivity were fabricated via a dip-coating method followed by sintering process, and the effects of the dip-coating and sintering process on the conductivity and surface roughness of silver electrodes were investigated in detail. The silver film with a thickness of 1.97 µm and a roughness of about 2 nm can be prepared after dip-coating at a pulling rate of 500 µm s−1 for 40 coating times. The non-conductive dip-coated silver films are transformed into conductive silver electrodes after conventional sintering in a muffle oven, infrared sintering and microwave sintering, respectively. Compared with high sintering temperature and long sintering time of conventional sintering and infrared sintering, microwave sintering can achieve quick sintering of silver films to fabricate high conductive silver electrodes. The silver electrodes with a sheet resistance of 0.75 Ω sq−1 and a surface roughness of less than 1 nm can be obtained after microwave sintering at 500 W for 50 s. The adjustable dip-coating method followed by quick microware sintering is an appropriate approach to prepare high conductive AgNPs-based electrodes for organic light-emitting diodes or other devices.

Modified activated carbon for deironing of underground water

Successful water treatment is one of the most important aspects for a healthy human life and environmental protection. This study deals with the investigation of a modified catalytic material that is used in water treatment as one of the most promising filter media for water deironing. The activated carbon granules were coated with iron oxide by solution combustion synthesis (SCS) method in a muffle furnace oven. We investigated obtained samples using different diffraction and spectroscopic methods. The elemental composition of the surface and phases of produced materials and the results of comparative analysis with initial samples of the raw material used for the underground water deironing were presented. Using the SCS method, active coal granules were modified with a formation of fine dispersed and crystalline structures of magnetite on their surface. This had a positive effect on the catalytic capacity of the material for deironing of underground water as well as for the specific surface area increase. The residual concentration of total iron in the first portions of the filtrate when using modified samples was almost 3 times lower than for initial material.

DETERMINAÇÃO DE METAIS EM BEBIDAS LÁCTEAS

The search for healthier, innovative and practical products has moved the exponential growth of the dairy industry. Various foods have in their composition additives to enhance color, smell, texture and ensure greater durability. Rigorous quality control for the detection of contaminants and other potentially toxic and carcinogenic substances is essential for the industry. The objective of this work was to quantify the levels of lead, cadmium and chromium metals, which present a higher toxic potential in relation to health, which ends up affecting the children in a more significant way. The digestion method was used in a muffle oven. All three analyzed brands showed high levels of chromium and cadmium and absence of lead. The X mark showed the highest levels of these metals, followed by the Z mark, and the Y mark the lowest concentrations, but all with values above that established by the legislation. Therefore, all the analyzed brands presented positive results

Highly nonlinear varistors fabricated by hot-dipping tin oxide thin films in Ta2O5 powder at different temperatures

This work proposed a smart approach to fabricate highly nonlinear SnOx-Ta2O5 thin film varistors. During processing, tin oxide films in nanoscaled thickness were firstly deposited onto electrically conducting silicon wafers through radio frequency magnetron sputtering a sintered tin oxide ceramic target; and then, the obtained films were hot-dipped in Ta2O5 powder in a Muffle oven for 60min at different temperatures. With the hot-dipping temperature increased from 300 to 800°C, the nonlinear coefficient of the samples increased first and then decreased, reaching the maximum of 16.8 at 600°C, which is a record in all the reported SnO2-based varistors and comparable with those of the most extensively investigated and commonly commercially applied ZnO-based ceramic varistors. Correspondingly, the leakage current decreased first and then increased, obtaining the minimum of 4.1mA/cm2. Besides, the breakdown electric field increased first and then decreased, presenting the maximum of 0.0313V/nm. Such nanoscaled thin film varistors would be promising in electrical and electronic devices working in low-voltage.

Preparation and Characterization of Pb(Zr,Ti)O<sub>3</sub> Obtained by the Pechini Method

The aim of this work was to synthesize lead zirconate titanate, Pb(Zr0.52Ti0.48)O3 (PZT) via Pechini method, to characterize the polymeric precursor through differential thermal analysis and thermogravimetric analysis, as well as to characterize the PZT powder through x-ray diffraction and scanning electron microscopy with energy-dispersive spectroscopy. In this work, the metallic precursors used during the PZT synthesis were titanium IV isopropoxide, zirconyl nitrate and lead nitrate; citric acid and ethylene glycol were used as chelating and polymerizing agents, respectively. The polymeric precursor was calcined at 800°C for two hours in a muffle oven. The main results showed that the polymeric precursor undergoes decomposition at approximately 316°C and PZT is crystallized around 722°C. It was confirmed that the PZT powder has chemical composition in the morphotropic phase boundary and its morphology consists of agglomerates of particles. Finally, it was proved that the PZT powder is crystalline, with the predominance of the tetragonal phase.

Porous g-C 3 N 4 with enhanced adsorption and visible-light photocatalytic performance for removing aqueous dyes and tetracycline hydrochloride

Abstract Porous g-C3N4 samples were obtained by simply calcining bulk g-C3N4 in static air in a muffle oven. The photocatalytic performance of these samples was evaluated through the removal of aqueous organic dyes (methylene blue and methyl orange) and tetracycline hydrochloride under visible-light irradiation (λ > 420 nm). Compared to bulk g-C3N4, porous g-C3N4 exhibited much better capability for removing these contaminants, especially under visible-light irradiation, due to the enlarged specific surface area and more efficient separation of photogenerated charge carries. In particular, porous g-C3N4 obtained by calcining bulk g-C3N4 in air at 525 °C showed the highest visible-light-driven catalytic activity among these samples. Superoxide radical anions (·O2−) were found to be the primary active species responsible for photodegradation.

Heat impact and soil colors beneath hearths in northern Sweden

The archaeological remains of Sami hearths in boreal and subarctic areas of northern Sweden are common finds. Greater understanding of the effects of heat on soil coloration will facilitate interpretation of the main purpose of these hearths, for example as heat sources or for cooking or other processing, and whether they were used seasonally for long or short periods of time. We therefore studied effects of heat on the coloration of natural B-horizons beneath traditional Sami hearths using three approaches: firing with dry pine wood in experimental hearths and measuring the temperature at various levels beneath the hearths; laboratory heating of B-horizon soils at different temperatures (200–900 °C) in a muffle oven and; measuring soil color changes in terms of RGB-values, and comparing the experimental results with soil profiles beneath real hearths used by nomadic Sami reindeer herders in northern Sweden. The study shows that the temperature reached beneath hearths strongly depends on the type of fuel used and the length of firing. The temperature can rise rapidly in upper layers of the soil but it takes considerable time for heat to penetrate 20 cm below the hearth surface. Our experimental firings, for 10 h on three consecutive days and for 72 consecutive hours, resulted in bowl-shaped areas of discoloration, with strong red coloration (rubification) towards the edges and dark grey/brown discoloration in the middle of the hearths in both tests. After laboratory heating, soil samples darkened during temperatures of 200–300 °C, and rubification at 250–350 °C depending on the amount of humus in the soil. The RGB analysis showed a steady increase in rubification from 300 °C, peaking at 750–800 °C. We believe that the rubification is caused mainly by transformation of iron compounds to maghemite and hematite and that the quantity of hematite is determined by temperature and not by time.Excavations of ancient hearths also revealed examples of bowl-shaped discoloration in B-horizons deeper than 20 cm. These discolorations had a rather uniform red tone with no dark areas. This suggests that the darker areas, probably colored by reduced iron and not by charred particles, could have been altered over time. The main conclusion is that rubification in B-horizons beneath hearths can arise after a relatively short period of firing but-bowl shaped areas of deep coloration can only arise, in boreal and subarctic areas, when hearths have been fired heavily and continuously for long periods of time, indicating winter use.

Recovery of Co, Mn, Ni, and Li from spent lithium ion batteries for the preparation of LiNixCoyMnzO2 cathode materials

Cathode materials of spent lithium ion batteries (LIBs) were recycled in an environmentally responsible manner to synthesize LiNixCoyMnzO2 cathode materials for LIBs. N-methyl-2-pyrrolidone as ultrasonic solvent was chosen to separate the cathode active materials from the Al foil under ultrasonic treatment for 3min at room temperature. The cathode active materials were calcined at 750°C for 4h in a muffle oven to eliminate carbon and polyvinylidene fluoride. The composition and morphology of the directly dismantled cathode materials, cathode active materials, calcination products, and leach residues were characterized by X-ray diffraction and scanning electronic microscopy. The proportion and element distributions were determined by inductively coupled plasma atomic emission spectroscopy and energy-dispersive X-ray spectrometry. The results showed that carbon and polyvinylidene fluoride in the cathode active materials were converted into volatile components, and small amounts of Co3O4 and Al2O3 were generated during the calcination stage; the residual calcination products could be dissolved to achieve 100% dissolution rate during the microwave digestion. The preparation of LiNixCoyMnzO2 cathode materials for LIBs appears to be effective with the simultaneous recovery of the mixed metal Co, Mn, Ni, and Li ions from spent LIBs.

Growth and Biochemical Composition of Navicula sp. Cultivated at Two Light Intensities and Three Wavelengths

Many studies have reported that the exposure of microalgae cultures to red light increases the production of carbohydrates, while blue light promotes the production of protein. There are several studies about Navicula, however there are few, if any, studies of the combined effects of wavelength and light intensity on the biochemical composition of this genus In this study we evaluated the combined effect of three wavelengths: white (400-750nm), blue (430-480nm), and red (650-750nm), at two light intensities (50 and100 μmol/m2/sec) on the growth and biochemical composition of Navicula sp. cultured on a laboratory scale. The experiment was carried out under controlled conditions utilizing a factorial design 2x3 (light intensity and wavelength) with white light as the control. The cell concentration was measured daily. Dry biomass of filtered cells was incinerated at 450ºC in a muffle oven. The biochemical content was measured using micro methods. The cell concentration was higher with white light at both intensities (291,875 and 90,938 cells/mL at 50 and100 μmol photon/m2/sec, respectively). Microalgae grown under blue wavelengths at 100 μmol photon/m2/sec had the highest dry biomass (1607 pg/cell). The highest percentage of protein was obtained under the blue light (22.83%), carbohydrates under the white light (4.13) and lipids under the red light (35.25%) all these results were observed under the low light intensity (50 μmol photon/m2/sec). The highest cell concentration and growth rate was observed under the low light intensity the largest proportions of which were proteins produced under the blue light. Lipid composition was not affected by light intensity or wavelength.

Extraction of vanadium from stone coal by roasting in a fluidized bed reactor

In order to improve leaching efficiency of vanadium pentoxide (V2O5) from stone coal and to reduce its connected environmental pollution, this article investigated the oxidizing roasting of stone coal in a laboratory fluidized bed reactor to optimize the roasting method and conditions. The examined parameters included reaction temperature, reaction time and amount and mixing method of additive. The removal of Cl from the generated effluent gas was implemented using CaO as the adsorbent, and comparison was made between the fluidized bed roasting and static roasting in a muffle oven. The results show that the fluidized roasting is more favorable to leach V2O5 from stone coal, which can shorten roasting time for reaching the maximal leaching rate, while the realized leaching rate is also higher. Comparing the mixing method applied to stone coal and additive, the impregnation method of additive on stone coal not only increased the leaching rate and shortened the roasting time for reaching the maximal leaching rate, but also reduced the amount of additive required. Adding CaO in stone coal roasting sharply decreased the content of Cl-containing gases in flue gas, which can greatly alleviate the possible environmental pollution. The optimal conditions for fluidized bed roasting were found to be impregnating 6wt.% additive on coal, adding 3wt.% CaO and performing roasting at 800°C for 0.75h.

Lab-Scale Investigations During Combustion of Agricultural Residues and Selected Polish Coals

Abstract Preliminary lab-scale investigations were conducted on slagging abatement in biomass-firing by fuel mixing. Three agriculture biomass fuels and olive cake were used in the experiments. Polish lignites and bituminous coals were examined as anti-sintering additives. The effects of chlorine release, potassium retention and ash sintering were examined by heating samples of biomass fuels and additives in the muffle oven and, next, firing them in the laboratory down-fired furnace at the temperature in the range of 800-1150ºC. The obtained slag samples were analysed on: chlorine and potassium content, sintering tendency and crystalline components. Among the examined coals lignite from Turów mine and bituminous coal from Bolesław Śmiały mine appeared to be the most effective in potassium retention in aluminosilicate and chlorine release from slag. Possibly the major factor of these coals which reduced ash sintering was relatively high content of kaolinite

New method for sintering silica frits for capillary microcolumns

One of the main steps in the manufacture of robust and efficient packed capillary microcolumns for electro- and capillary chromatography is the generation of porous devices to retain the packed beds. Frits based on sintered silica particles have been found to give the best results in terms of mechanical resistance and efficiency. The conventional procedure to produce these kinds of frits consists in a radial heating of the packed material with either a flame or an electrical resistance, but the frits thus obtained have many drawbacks as a result of the procedure rather than the silica per se as the base material. In the present work we investigated a new approach to produce silica-based retaining devices involving the frontal exposure of a short silica-particle bed packed at the end of a capillary tube. The capillary is radially insulated and frontally exposed to the heat of a muffle oven, generating a transfer of heat that is not radial but rather throughout the capillary axis. This procedure resulted in substantial advantages: an improved radial homogeneity, a protection of the external polyimide, and a generation of extremely short (400–600μm) frits that were highly permeable and avoided bubble formation.

Thermal and hydrometallurgical recovery methods of heavy metals from municipal solid waste fly ash

Heavy metals in fly ash from municipal solid waste incinerators are present in high concentrations. Therefore fly ash must be treated as a hazardous material. On the other hand, it may be a potential source of heavy metals. Zinc, lead, cadmium, and copper can be relatively easily removed during the thermal treatment of fly ash, e.g. in the form of chlorides. In return, wet extraction methods could provide promising results for these elements including chromium and nickel. The aim of this study was to investigate and compare thermal and hydrometallurgical treatment of municipal solid waste fly ash. Thermal treatment of fly ash was performed in a rotary reactor at temperatures between 950 and 1050°C and in a muffle oven at temperatures from 500 to 1200°C. The removal more than 90% was reached by easy volatile heavy metals such as cadmium and lead and also by copper, however at higher temperature in the muffle oven. The alkaline (sodium hydroxide) and acid (sulphuric acid) leaching of the fly ash was carried out while the influence of temperature, time, concentration, and liquid/solid ratio were investigated. The combination of alkaline-acidic leaching enhanced the removal of, namely, zinc, chromium and nickel.