Development, characterization and evaluation of the efficiency of cost-effective medium for the removal of Pb2+, Cd2+ and Ni2+ from aqueous systems, as a novel, eco-friendly solution for wastewater ...remediation were done. The precursors for low-cost adsorbent were lignocellulosic raw materials (sweet/sour cherry kernels), as industrial byproducts and components of organic solid waste. Activated carbon synthesis was carried out by thermochemical conversion (H3PO4, 500 °C) in the complete absence of inert atmosphere. Characterization of the activated carbon was performed by elemental analysis, FTIR, SEM, EDX and BET. BET surface area corresponds to 657.1 m2 g−1. The evaluation also included the influence of pH, contact time, solute concentration and adsorbent dose on the separation efficiency in the batch operational mode. The equilibrium and kinetic studies of adsorption were done. The maximum adsorption capacity of the activated carbon for Cd2+ ions was calculated from the Langmuir isotherm and found to be 198.7 mg g−1. Adsorption of Pb2+ and Ni2+ were better suitable to Freundlich model with the maximum adsorption capacity of 180.3 mg g−1 and 76.27 mg g−1, respectively. The results indicate that the pseudo-second-order model best describes adsorption kinetic data. Based on desorption study results, activated carbon was successfully regenerated with HNO3 for 3 cycles. In order to provide the results for basic cost-effective analysis, competing ion-effects in a real sample have been evaluated.
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•Pb2+, Cd2+ and Ni2+ removal on cherry kernels activated carbon were studied.•Low-cost activation develops large pore volume with 657.1 m2 g−1 surface area.•The sorption capacity with 171.4 mg g−1 mainly depends on the surface chemistry.•The produced adsorbent could be applied into wastewater treatment.•Our approach was simple and inexpensive.
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The purpose of this paper is to determine the temperature fields in the workpiece and the tool in the ironing process using an integrated approach that includes laboratory experiments and numerical ...modelling. An originally developed model device for ironing sheet metal strips, which was previously shaped by U-bending, was used for the experimental research. Thermocouples were installed in the device at the position close to the contact surface with the workpiece. The device was mounted on a hydraulic press that enables maximum ironing speeds of v = 4,17 mm/s. In order to determine the temperature fields at higher ironing speeds, a series of numerical experiments was performed at identical speeds as in the experiments (0,33 mm/s and 4,17 mm/s) and at higher speeds (100 mm/s, 1000 mm/s and 10000 mm/s). Good matches of the experimental and numerical results at lower speeds were obtained, so the numerical estimates at higher speeds were valid for the analysis and conclusions. With the increase of the ironing speed, a trend of temperature increase is evident. The maximum temperature of 166 degreesC at ironing speed of 10000 mm/s that corresponds to manufacturing of 250 cans per minute is significantly lower than the critical melting temperature of the tin coating.
Dissecting a human cadaver is an irreplaceable practice in general training of medical students. Cadavers in anatomy laboratories are usually preserved in formalin, an embalming fluid whose basic ...component is formaldehyde (FA). The aim of this study is to assess the cancer risk of employees and students that are exposed to FA based on the results of three monitoring campaigns, as well as to suggest permanent solutions to the problem of FA exposure based on the results obtained. Three sampling campaigns of formaldehyde concentration in indoor environments were conducted at five different locations at the Anatomy Department of the Faculty of Medicine with the purpose of assessing permanent employees’ and medical faculty first year students’ exposure to FA. Indoor air was continuously sampled during 8 h of laboratory work and analyzed in accordance with the NIOSH Method 3500. Exceeding of the 8 h time-weighted average (8 h TWA) values recommended by Occupational Safety and Health Administration (OSHA) of 0.75 ppm was recorded in 37% of the samples during the three-month monitoring campaign. Cancer risk assessment levels for permanent employees were in the range from 6.43 × 10−3 to 8.77 × 10−4, while the cancer risk assessment levels for students ranged from 8.94 × 10−7 to 1.83 × 10−6. The results of the research show that cancer risk assessment for employees is several thousand times higher than the limit recommended by the EPA (10−6) and point to the importance of reducing exposure to formaldehyde through the reconstruction of the existing ventilation system, continual monitoring, the use of formaldehyde-free products, and plastination of anatomical specimens.
Knowing the material properties is of a crucial importance when planning to manufacture some structure. That is true for the steel structures, as well. Thus, for the proper planning of a certain ...steel part or a structure production, one must be aware of the properties of the material, to be able to make a qualified decision, which material should be used. Considering that the manufacturing of steel products is constantly growing in various branches of industry and engineering, the problem of predicting the material properties, needed to satisfy the requirements for the certain part efficient and reliable functioning, becomes an imperative in the design process. A method of predicting four material properties of the two stainless steels, by use of the artificial neural network (ANN) is presented in this article. Those properties were predicted based on the particular steels’ known chemical compositions and the corresponding material properties available in the Cambridge Educational System EDU PACK 2010 software, using neural network module of MathWorks Matlab. The method was verified by comparing the values of the material properties predicted by this method to known values of properties for the two stainless steels, X5CrNi18-10 (AISI 304), X5CrNiMo17-12-2 (AISI 316). The difference between the two sets of values was below 5% and, in some cases, even negligible.
The results of the research in the field of benzene, toluene, ethylbenzene and xylene isomers (BTEX) concentrations in exhaust gases of spark ignition engines under different operating conditions are ...presented in this paper. The aim of this paper is to gain a clearer insight into the impact of different engine working parameters on the concentrations of BTEX. The experimental investigation has been performed on the SCHENCK 230 W test stand with the controlled IC engine. The engine operating points have been chosen based on the results of a simulation and they are considered as the typical driving conditions according to the New European Driving Cycle. Concentration levels of BTEX compounds in exhaust gas mixtures have been determined by gas chromatography technique by using the combination of Supelcowax 10-Polyethylene glycol column and the PID detector. Based on the experimental research results, the emission model of BTEX compounds has been defined by the simulation of movement of a Fiat Punto Classic passenger car in accordance with the NEDC cycle.
Using the results obtained within the simulation, the official statistics on the number of gasoline-powered cars on the territory of the Republic of Serbia and the European Commission data on the annual distance traveled by car, the amounts of BTEX compounds emitted annually per car have been estimated, as well as the emissions of the entire Serbian car fleet.
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•BTEX emission at characteristic operating points of the driving cycle.•GC analysis of exhaust gases in different operating modes.•The prediction of total emissions based on a limited number of measurements.•Benzene emission of 0.04 g km−1.•The possibility of using the emission model in different driving patterns.
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This paper presents 3D-printed micro-porous structures made of a Cu/PLA composite by using material extrusion 3D printing technology. A metallic filament made of 80% copper and 20% polylactic acid ...(PLA) was used for the 3D printing of the porous samples. We varied printing parameters, aiming to obtain a micro-range porosity that can serve as a water-filtering structure. The produced samples were analyzed from the aspects of dimensional accuracy, level of porosity, and capacity for water flow. Several samples were fabricated, and the water flow was exhibited for the samples with an approximate 100 µm size of the interconnected open porosity. The application of material extrusion 3D printing, as a cost-effective, widely available technology for producing micro-range porous structures, is still challenging, especially for interconnected predefined porosity with metal-based filaments. Our research showed that the optimization of 3D printing parameters can enable the fabrication of copper-based micro-porous structures, but further research is still needed.
The digital printing process contributes to the quality of indoor air through the emission of chemical stressors such as total volatile organic compounds (TVOCs) and suspended particulate matter ...(SPM). The concentration levels of SPM and TVOCs were determined using the gravimetric and gas chromatography method, respectively. The results show that the digital printing machines and the cutting machine do not produce PM
2.5
particles. The significant cumulative mass concentrations of PM
10
suspended particles of 9.91 μg/m
3
for a single-colour digital printing machine, 4.45 μg/m
3
for a four-colour digital printing machine, and 2.02 μg/m
3
for a cutting machine, were detected. By comparing the cumulative values of TVOC concentration levels measured, it can be concluded that the values have been 4 to 12 times higher for the four-colour digital printing machine than for the single-colour digital printing machine. Namely, the TVOC concentration levels measured for the four-colour digital printing machine ranged from 28.69 to 57.30 mg/m
3
, while the values for the single-colour digital printing machine ranged from 2.31 to 13.51 mg/m
3
. Considering the fact that there are no standards of quality of indoor air in printing offices defined in the Republic of Serbia, the results obtained could represent a valid basis and a worthy guideline for the definition of values necessary for the indoor air quality assessment.
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•Electrocoagulation/flotation (ECF) treatment of the printing effluent was applied.•The combinations of electrodes of dissimilar metals were used.•The copper (Cu) was successfully ...removed (95.5%) with aluminum electrodes.•Response surface methodology was used for ECF treatment optimization.•Solidification/stabilization treatment efficiently immobilized Cu in waste sludge.
The electrocoagulation/flotation treatment (ECF) was employed for the reduction of copper from the waste printing developer in a batch study by using four different aluminum and iron electrode combinations with independent ECF parameters such as current density, interelectrode distance and operating time. The individual and interactive effects of the three main independent ECF parameters were studied by using the response surface methodology. Based on the results, parameters for high copper removal efficiency (95.5%) from the waste printing developer by the ECF were: Al(−)/Al(+) electrode combination with an interelectrode distance of 1.0 cm, operating time of 10 min and a current density of 4 mA cm−2. Moreover, the kinetic study of the ECF treatment of waste printing developer demonstrated that the removal of copper follows the pseudo second-order model with current dependent parameters. For immobilization process of copper in waste ECF sludge, the solidification/stabilization (S/S) treatment was conducted with Portland cement, lime, bentonite, and local clay as immobilization agents. The efficiency of the S/S treatment was monitored by applying leaching tests with one extraction fluid during a certain time. Therefore, using ECF and S/S treatments, copper from the printing effluent can be safely disposed into the environment.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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