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Crystallization characteristics of bioactive polyphosphate glasses
No full textThe essence of this paper is to present the effect of adding TiO2 and SrO to the crystallization characteristics of polyphosphate glasses. The crystallization of glasses has been studied by using DTA, HSM and XRD methods. Sintered phosphate glass-ceramics containing bioactive β-CaP2O6 and β-Ca3(PO4)2 phases were successfully prepared. The increasing presence of Sr (1-5 %), as well as Ti at the expense of phosphate mole fraction in polyphosphate bioactive glass increases the density of these glasses, transformation temperature and resistance to crystallization
Removal efficiency of heavy metal ions from aqueous solution with waste tree biomass hydrochars
No full textIn this study, Paulownia tree leaves hydrochars (PL-HTCs) were used as potential adsorbents for
Zn(II), Cd(II) and Mn(II) ions from aqueous solution and their efficiency was investigated. The
preliminary adsorption results showed that hydrochars had better affinity for Cd(II) than for Zn(II)
and Mn(II) ions removal. In order to improve adsorption capacity, hydrochar obtained at 220°C were
activated with NaOH and further investigated only for Cd(II) removal. Alkali activated hydrochar
(AH-220) has significantly better efficiency (q=24.05 mg/g, E=52.57%) in removing Cd(II) ions than
hydrochar before modification. Adsorption kinetic studies showed that Cd(II) ions sorption at AH-220
surface followed the pseudo-second-order model. This implies that the adsorption process was mostly
controlled by the chemical binding.
Keywords: tree leaves hydrochars, adsorption, heavy metals, kinetic studies
Evaluation of Adsorption Efficiency on Pb(II) Ions Removal Using Alkali-Modified Hydrochar from Paulownia Leaves
No full textIn this study, hydrothermal carbonization (HTC) at five temperatures (180, 200, 220, 240,
and 260 C) was applied to transform Paulownia leaves (PL) into a carbonaceous sorbent of Pb(II)
from aqueous solutions. To enhance the adsorption efficiency of the obtained hydrochar (PH),
subsequent alkali activation was performed using NaOH. Preliminary results of the Pb(II) adsorption
(CPb = 200 mg/L) showed removal coefficients after 48 h of 73.44 mg/g, 82.37 mg/g, and 110.9 mg/g
for PL, PH-220, and MPH-220, respectively. The selected hydrochar (PH-220) and modified hydrochar
(MPH-220) were further investigated by scanning electron microscopy (SEM) and Fourier transform
infrared spectroscopy (FTIR). The results revealed that alkali treatment changed the hydrochar
structure and, thus, improved its adsorption performance. The kinetic parameters showed that
the Pb(II) sorption onto MPH-220 followed a pseudo-second-order model, while the intra-particle
diffusion went through two simultaneous stages. The Langmuir isotherm model best described the
experimental data and indicated the value of 174.75 mg Pb(II)/g as the maximum adsorption capacity.
The two possible mechanisms of Pb(II) binding were complexation and/or Pb- electron interaction.
The obtained results indicate the great potential of MPH-220 for Pb(II) removal from aqueous media
and its potential utilization as an effective adsorbent for wastewater purification
Microstructure assessment of co alloy intended for dentistry
No full textCobalt–chromium–molybdenum (CoCrMo) alloys are known for medical use due to their biocompatibility, corrosion and
wear resistance. The chemical and phase composition, as well as microstructure of the alloy directly affect the mechanical properties. In this investigation, CoCrMo alloy samples were obtained by vacuum precise casting. The procedure of melting and casting process as well as their parameters are given. Molds fabricated of copper, gray iron, steel, ceramics and graphite were used during the casting process. In this way, the cooling rate influence on the obtained microstructure was examined. Besides, different casting temperatures (1400°C, 1450°C and 1500°C) were applied for each kind of mold. After metallographic preparation, the microstructure was examined on the cross section of samples by optical microscopy. The obtained results show that by increasing the cooling rate, the microstructure of samples become finer and more homogeneous
Model Development for Casting Simulation of Railway Aluminothermic Welding
No full textAluminothermic welding has been used to connect railway rails for over a century. This technique has the advantages of flexibility, weld compactness, and simplicity. External energy is not required for the procedure. Exothermic heat is produced by chemical reactions of aluminothermic elements. To create a quality welded connection, the mold and pouring system must provide uniform pouring of hot steel
without turbulence, even heat dissipation or cooling, and an acceptable micro and macro structure of steel free of internal and external faults. The design of the mould was constantly changing, necessitating costly industrial experimentation. As a result, the mould's design was constantly evolving, necessitating the use of costly experimental procedures in industrial settings. The latest iteration of the model the
casting cavity was improved by adding hoes in the sand and putting rails on both sides in order to more aquratly simuate heat transfer. Software programs are emulating conventional casting procedures for thermite steel casting in welded railway connections to save money and effort on costly and timeconsuming industrial testing. For the 49E1 rail, NovaFlow & Solid CV were utilized to simulate casting thermite steel in the mould cavity or weld junction
Exergy analysis of steel manufacturing in the oxygen converter
No full textIn oxygen converters, molten iron from the blast furnace is refined with steel waste under oxidizing conditions [1]. The injected oxygen passes into the iron melt, after which it reacts with the impurities. Analysis of exergy losses clearly indicates the place of energy losses in the observed process, so a detailed analysis can influence the improvement of a complex process [2]. Exergy losses occur due to technological imperfections such as heat dissipation or friction and system irreversibility according to the second law of thermodynamics [3]. The concept of exergy can be used for a better understanding of the feasibility of a process, as well as for the techno-economic analysis of the process at different variations of input/operating parameters. In this work througtful calculation of exergy oxygen convertor was done. According to the obtained data, out of a total of 972.2 MJ of thermal energy, which is released by exothermic reactions in the refining process, 817.5 MJ is pure exergy and can be used, the rest is anergy that arises due to irreversibility
Priprema i primena aktiviranog zeolita kao donora u poljoprivredi
No full textZeolite is a natural mineral that is mainly used as an adsorbent of heavy metals and radioactive elements from the soil. By activating zeolite from natural mines in the Kopaonik area, it was determined that the activated zeolite becomes a calcium and magnesium donor. Calcium and magnesium are two elements necessary for plant growth. This patent application describes how zeolite is activated and how it is applied in agriculture as a calcium and magnesium donor
Biosorption of brilliant green using Myriophyllum spicatum immobilized in alginate beads
No full textOver the past few decades, synthetic dye pollution of water has emerged as one of the most significant environmental
problems [1]. The toxic cationic dye brilliant green (BG), is commonly used in the dyeing of textiles, rubber, paper, printing,
and other dye-based industries [2]. Cationic dyes are more poisonous than anionic dyes. Even at modest concentrations (1
mg/L), cationic dyes, like BG, can be extremely harmful to human health [3]. To protect the environment, it is essential to
remove this dye from wastewater [4]. For the removal of dyes from the effluents, a number of methods of treatment have
been applied, including adsorption, oxidation-ozonation, biological treatment, coagulation-flocculation, and membrane
process [5]. Biosorption has been shown to be an efficient, affordable technique for removing synthetic dyes from
wastewater, particularly when using biowaste and agricultural byproducts as the biosorbent [6]. In this study, biosorbent
prepared from submerged aquatic weed Myriophyllum spicatum immobilized in alginate beads MsA was used for removal
of toxic dye, brilliant green, from aqueous solutions in batch system. Before and after BG biosorption, different functional
groups present on MsA beads were examined using Fourier transform infrared spectroscopy (FTIR) analysis. The functional
groups involved in the biosorption process were: carboxyl, carbonyl and hydroxyl. Three reaction and one diffusion based
kinetic models were applied on kinetic data removal BG on MsA. Kinetic modeling confirms the pseudo second-order model
by showing that chemisorption, which involves ionic interactions, is the rate-limiting phase [7]. Intraparticle diffusion is not
a sole rate-controlling step and biosorption process might be of complex mechanism included of both surface biosorption
and intraparticle diffusion. The adsorption capacity was 19.7 mg/g. These findings support the use of cost-effective and
sustainable immobilized cosmopolitan invasive aquatic weed for the decolorization of industrial wastewater
Application of Natural Polymer and Metal Oxide Composite for Removal of Arsenic (V) Ions from Aqueous Solutions
No full textIn this study, iron oxide nanoparticles immobilized within alginate gel exhibited promising potential for the removal of arsenic (V) ions. The preparation of the polymer-oxide composite was achieved by the ionic crosslinking of an alginate/iron oxide solution with a calcium (II)ions solution. The maximum amount of arsenic adsorbed by the investigated composite under the experimental conditions was slightly above 26 mg/g in 120 min. The results indicated that arsenic adsorption by this composite material follows a fast kinetic profile, adhering to a pseudo-second-order model. The adsorption process occurs in multiple stages, as suggested by the Weber-Morris model, with external diffusion dominating initially, followed by intraparticle diffusion. Importantly, the results confirmed that the use of alginate gel does not significantly impact the adsorption process, preserving the adsorption capacity of the metal oxides. Overall, the investigated composite successfully removed arsenic (V) from the solution, addressing a critical issue in water treatment.
(1) (PDF) Application of Natural Polymer and Metal Oxide Composite for Removal of Arsenic(V) Ions from Aqueous Solutions. Available from: https://www.researchgate.net/publication/378821317_Application_of_Natural_Polymer_and_Metal_Oxide_Composite_for_Removal_of_ArsenicV_Ions_from_Aqueous_Solutions [accessed Mar 12 2024].
Modified hybrid cellulose membrane for Nickel(ii) ions removal from industrial wastewater
No full textNickel pollution of water induces several problems for the environment. The purpose of this paper was to
investigate the adsorption of Ni2+ ions on fabricated biomembranes. The proposed adsorbent was prepared
from epoxy and amino-functionalized waste cellulose fibers, able to participate in cross-linking with amino
acid lysine - wCell/Mn-Fe_LDH. The prepared material underwent preliminary structural characterization
by Fourier-transform infrared spectroscopy. In a batch system, the influence of pH, contact time,
temperature, and initial concentration on adsorption efficiency was investigated. The effectiveness of the
membrane was demonstrated by acceptable adsorption capacities of 40.49 mg g-1 obtained for Ni2+ at 45°C.
The kinetic study, using the Weber-Morris model, indicates intraparticle diffusion as the rate limiting step.
Adsorption mechanism physisorption was proposed based on thermodynamic behaviors. The outcomes
demonstrated that environmentally friendly sustainable technology has been successfully developed