The objective of this study was to determine the effect of advanced oxidation process with the use of Fenton’s reaction on the effectiveness of anaerobic treatment of wastewaters originating from the wood industry that were characterized by a high concentration of formaldehyde. Experiments were established to analyze changes in COD content and in the concentration of formaldehyde in treated wastewaters, additional analyses were carried out to assay quantitative and qualitative changes in the biogas produced. The first stage of the experiment involved analyses of the effectiveness of the tested wastewaters treatment only in the process of methane fermentation. At the second stage of the experiment, the biological process was preceded by chemical pre-treatment of wastewaters with Fenton’s reagent. The conducted study proved that the investigated variants of chemical pre-treatment of wastewaters had a significant effect on increasing the total biogas production. In contrast, no significant effect of the applied technology was demonstrated on changes in the concentration of the analyzed contaminants in the treated wastewaters.
In this study, the combined effect of Zr and Si on isothermal oxidation of Ti for 25 and 50 h at 820°C, which is the temperature related to exhaust valves operation, was investigated. Si addition into Ti-5mass%Zr alloy led to a distribution of silicide Ti5Si3 phase formed by a eutectic reaction. The Ti sample containing only Zr showed more retarded oxidation rate than Ti-6Al-4V, the most prevalent Ti alloy, at the same condition. However, while a simultaneous addition of Zr and Si resulted in greater increase of oxidation resistance. The oxide layer formed after the addition of Zr and Si comprised TiO2, ZrO2, and SiO2.
The decomposition of hydrocarbons using combined advanced oxidation methods is largely considered owing to abundant production of OH radicals and the potential economic advantages. In this study, the synergetic effect of ozonation on photocatalytic oxidation of chloroform and chlorobenzene over expanded graphite-TiO2&ZnO Nano composite was investigated. The effect of introduced ozone concentration and residence time was also examined on removal efficiency. The results showed that the removal efficiency was significantly enhanced by the combined system resulting from the additional oxidation process causing active species to be increased. Increasing the introduced ozone concentration which generates more reactive compounds had a greater effect on the removal efficiency than that of residence time. However, from the mineralization point of view, the residence time had a dominant effect, and the selectivity towards CO2 was dramatically declined when the flow rate increased. Based on these results, the combined system is preferred due to higher removal efficiency and complete mineralization.
Dye wastewater is one of typically non-biodegradable industrial effluents. A new process linking Fenton’s oxidation with biological oxidation proposed in this study was investigated to degrade the organic substances from real dye wastewater. During the combination process, the Fenton’s oxidation process can reduce the organic load and enhance biodegradability of dye wastewater, which is followed by biological aerated filter (BAF) system to further remove organic substances in terms of discharge requirement. The results showed that 97.6% of chemical oxygen demand (COD) removal by the combination process was achieved at the optimum process parameters: pH of 3.5, H2O2 of 2.0 mL/L, Fe(II) of 500 mg/L, 2.0 h treatment time in the Fenton’s oxidation process and hydraulic retention time (HRT) of 5 h in the BAF system. Under these conditions, COD concentration of effluent was 72.6 mg/L whereas 3020 mg/L in the influent, thus meeting the requirement of treated dye wastewater discharge performed by Chinese government (less than 100 mg/L). These results obtained here suggest that the new process combining Fenton’s oxidation with biological oxidation may provide an economical and effective alternative for treatment of non-biodegradable industrial wastewater.
In spite of the fact that in most applications, magnesium alloys are intended for operation in environments with room temperature, these alloys are subject to elevated temperature and oxidizing atmosphere in various stages of preparation (casting, welding, thermal treatment). At present, the studies focus on development of alloys with magnesium matrix, intended for plastic forming. The paper presents results of studies on oxidation rate of WE43 and ZRE1 magnesium foundry alloys in dry and humidified atmosphere of N2+1%O2. Measurements of the oxidation rate were carried out using a Setaram thermobalance in the temperature range of 350-480°C. Corrosion products were analyzed by SEM-SEI, BSE and EDS. It was found that the oxide layer on the WE43 alloy has a very good resistance to oxidation. The high protective properties of the layer should be attributed to the presence of yttrium in this alloy. On the other hand, a porous, two-layer scale with a low adhesion to the substrate forms on the ZRE1 alloy. The increase in the sample mass in dry gas is lower than that in humidified gas.
The photochemical degradation of the sulfadiazine (SDZ) was studied. The photochemical processes used in degradation of SDZ were UV and UV/H2O2. In the experiments hydrogen peroxide was applied at different concentrations: 10 mg/dm3 (2.94*10-4 M), 100 mg/dm3 (2.94*10-3 M), 1 g/dm3 (2.94*10-2 M) and 10 g/dm3 (2.94*10-1 M). The concentrations of SDZ during the experiment were controlled by means of HPLC. The best results of sulfadiazine degradation, the 100% removal of the compound, were achieved by photolysis using UV radiation in the presence of 100 mg H2O2/dm3 (2.94*10-3 M). The determined rate constant of sulfadiazine reaction with hydroxyl radicals kOH was equal 1.98*109 M-1s-1.
Treatment of leachate from an exploited since 2004 landfill by using two methods of advanced oxidation processes was performed. Fenton’s reagent with two different doses of hydrogen peroxide and iron and UV/H2O2 process was applied. The removal efficiency of biochemically oxidizable organic compounds (BOD5), chemically oxidizable compounds using potassium dichromate (CODCr) and nutrient (nitrogen and phosphorus) was examined. Studies have shown that the greatest degree of organic compounds removal expressed as a BOD5 index and CODCr index were obtained when Fenton’s reagent with greater dose of hydrogen peroxide was used - efficiency was respectively 72.0% and 69.8%. Moreover, in this case there was observed an increase in the value of ratio of BOD5/CODCr in treated leachate in comparison with raw leachate. Application of Fenton’s reagent for leachate treatment also allowed for more effective removal of nutrients in comparison with the UV/H2O2 process.
The study presents fifteen oxygen-bearing secondary minerals of bismuth from the north-eastern part of the Variscan Karkonosze granitoid pluton in the northern zone of the Bohemian massif. The minerals were investigated by optical, electron microprobe, classic chemical, XRD, IR absorption and fluid inclusion methods. The late, very low temperature epithermal solutions most probably caused formation of sillénite, kusachiite, bismoclite, bismutite, beyerite, kettnerite, pucherite, schumacherite, namibite and eulytite. Solutions dominated by supergene (meteoric) waters were the parents for bismite, russellite, koechlinite, ximengite and walpurgite. The paper also contains information on early research on the investigated minerals.
The possibility of producing 3-aminobenzyl alcohol and 3-aminobenzaldehyde by oxidation of 3-aminotoluene with ozone in the solution of acetic anhydrite in the presence of manganese (II) acetate, potassium bromide and sulfuric acid has been shown. The catalytic systems for regulating selectivity and depth of substrate oxidation has been developed. The catalytic system Mn(OAc)₂ – Ac₂0 – H₂SO₄ promotes the formation of alcohol (65.5%) and 3- acetylaminobenzylidendiacetate (20.1%) with the system Mn(OAc)₂ – KBr – Ac₂O – H2SO₄ increases oxidation selectivity on the methyl group to 90.8% producing mainly aldehyde (80.8%) The optimum temperature of selective oxidation of 3– aminotoluene with the ozone – air mixture (30°C) which is much lower than that of oxidation by the known methods (120°-240°C) and the optimum rations of the reagents concentrations: for alcohol synthesis – [ArCH3] : [Mn(OAc)₂] : [H₂SO₄] =1 : 0.2 : 2.5; for aldehyde synthesis –[ ArCH3]: [Mn(OAc)₂] : [KBr] aldehyde synthesis – [ArCH3] : [Mn(OAc)₂] : [KBr] : [H₂SO₄] = 1:0.2:2.5 have been determined.
Advanced automotive fleet repair facility wastewater treatment was investigated with Zero-Valent Iron/Hydrogen Peroxide (Air/ZVI/H2O2) process for different process parameters: ZVI and H2O2 doses, time, pH. The highest Chemical Oxygen Demand (COD) removal efficiency, 76%, was achieved for ZVI/H2O2 doses 4000/1900 mg/L, 120 min process time, pH 3.0. COD decreased from 933 to 227 mg/L. In optimal process conditions odor and color were also completely removed. COD removal efficiency was increasing with ZVI dose. Change pH value below and over 3.0 causes a rapid decrease in the treatment effectiveness. The Air/ZVI/H2O2 process kinetics can be described as d[COD]/dt = −a [COD]tm, where ‘t’ corresponds with time and ‘a’ and ‘m’ are constants that depend on the initial reagent concentrations. H2O2 influence on process effect was assessed. COD removal could be up to 40% (560 mg/L) for Air/ZVI process. The FeCl3 coagulation effect was also evaluated. The best coagulation results were obtained for 700 mg/L Fe3+ dose, that was slightly higher than dissolved Fe used in ZVI/H2O2 process. COD was decreased to 509 mg/L.
Experimental investigations and numerical simulations have been conducted in this study to derive and test the values of kinetic parameters describing oxidation and gasification reactions between char carbon and O2 and CO2 occurring at standard air and oxy-fuel combustion conditions. Experiments were carried out in an electrically heated drop-tube at heating rates comparable to fullscale pulverized fuel combustion chambers. Values of the kinetic parameters, obtained by minimization of the difference between the experimental and modeled values of char burnout, have been derived and CFD simulations reproducing the experimental conditions of the drop tube furnace confirmed proper agreement between numerical and experimental char burnout.
This study investigated the microstructure and high temperature oxidation properties of Fe-25Cr-20Ni-1.5Nb, HK30 alloy manufactured by metal injection molding (MIM) process. The powder used in MIM had a bi-modal size distribution of 0.11 and 9.19 μm and had a spherical shape. The initial powder consisted of γ-Fe and Cr23C6 phases. Microstructural observation of the manufactured (MIMed) HK30 alloy confirmed Cr23C6 along the grain boundary of the γ-Fe matrix, and NbC was distributed evenly on the grain boundary and in the grain. After a 24-hour high temperature oxidation test at air atmospheres of 1000, 1100 and 1200°C, the oxidation weight measured 0.72, 1.11 and 2.29 mg/cm,2 respectively. Cross-sectional observation of the oxidation specimen identified a dense Cr2O3 oxide layer at 1000°C condition, and the thickness of the oxide layer increased as the oxidation temperature increased. At 1100°C and 1200°C oxidation temperatures, Fe-rich oxide was also formed on the dense Cr2O3 oxide layer. Based on the above findings, this study identified the high-temperature oxidation mechanism of HK30 alloy manufactured by MIM.
The possibility of removing organic compounds from wastewater originating from the photochemical production of printed circuit boards by use of waste acidification and disposal of precipitated photopolymer in the first stage and the UV-Fenton method in a second stage has been presented. To optimize the process of advanced oxidation, the RSM (Response Surface Methodology) for three independent factors was applied, i.e. pH, the concentration of Fe(II) and H2O2 concentration. The use of optimized values of individual parameters in the process of wastewater treatment caused a decrease in the concentration of the organic compounds denoted as COD by approx. 87% in the first stage and approx. 98% after application of both processes. Precipitation and the decomposition of organic compounds was associated with a decrease of wastewater COD to below 100 mg O2/L whereas the initial value was 5550 mg O2/L. Decomposition of organic compounds and verification of the developed model of photopolymers removal was also carried out with use of alternative H2O2 sources i.e. CaO2, MgO2, and Na2CO3·1,5H2O2.
Ductile irons of the type of Si-Mo are characterized by increased resistance to long-term influence of high temperatures and cyclic temperature changes. They are mainly used in castings of combustion engine exhaust piping and other castings utilized at temperatures of up to 850°C. The aim of the study is to verify the mechanical properties of non-alloyed cast iron EN CSN GJS 450, SiMo4-0.5 and SiMo5-1 ductile irons at temperatures of 700 to 800°C, and the extent of their superficial oxidation after longterm annealing at a temperature of 900°C. Via chemical microanalysis the composition of oxidation products in the surface layer was evaluated.
The study of the possibility of removing organic compounds from wastewater originating from the biodiesel puriﬁcation stage by two catalytic processes, HSO5-/transition metal and Fenton method has been presented. The source of the ion HSO5- is potassium monopersulphate (2KHSO5·KHSO4·K2SO4) (Oxone) that may be decomposed into radicals (OH., SO4-., SO5-.) by means of transition metal as Co(II). Different concentrations were used for both compounds and the combination ([Co2+] = 1.00μM/[HSO5-] = 5.00·10-2 M) achieved the highest COD removal (60%) and complete decomposition of the oxidant was veriﬁed for contact times of 45 min. This process has some advantages comparing to the conventional Fenton method such as the absence of the costly pH adjustment and the Fe(III) hydroxide sludge which characterize this treatment process. The Fenton process showed that the combination of [H2O2] = 2.00M/[Fe2+] = 0.70 M was the best and archived COD removal of 80%. The treatments studied in this research have achieved high COD removal, but the wastewater from the biodiesel puriﬁcation stage presents very high parametric values of Chemical Oxygen Demand (667,000 mgO2/L), so the ﬁnal COD concentration reached is still above the emission limit of discharge in surface water, according the Portuguese Law (Decree-Law 236/98). However, both treatments have proved to be feasible techniques for the pre-oxidation of the wastewater under study and can be considered as a suitable pre-treatment for this type of wastewaters. A rough economic analysis of both processes was, also, made.
Surfactants after their use are discharged into aquatic ecosystems. These compounds may be harmful to fauna and flora in surface waters or can be toxic for microorganisms of the activated sludge or biofilm in WWTP. In order to determine effectiveness of different advanced oxidation processes on the degradation of surfactants, in this study the degradation of anionic surfactants in aqueous solution using photolysis by 254 nm irradiation and by advanced oxidation process in a H2O2/UVC system was investigated. Two representatives of anionic surfactants, linear alkyl benzene sulphonate (LAS-R11–14) and ether carboxylic derivate (EC-R12–14E10) were tested. The influence of pH, initial surfactant concentration and dose of hydrogen peroxide on the degradation was also studied. Results show outstanding effectiveness of the H2O2/UVC system in the removal of surfactant from aqueous solutions.