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Lead removal from water solutions by natural and Fe(III)-modified zeolite encapsulated with alginate
No full textIn presented paper removal of lead ions from water solutions by the natural and Fe(III)-
modified zeolite encapsulated with alginate was investigated. Experiments were performed for
the initial lead concentrations in the range from 330 to 3100 mgPb(II)/dm3 and for three
temperatures: 25, 40 and 60oC. Results showed increase of adsorbed amount of lead with
increasing temperature and the initial lead concentrations. Much better removal of lead was
obtained with Fe(III)-modified zeolite encapsulated with alginate. The maximal removed
amounts of lead obtained for highest initial concentration were: 103, 113 and 124 mg/g for NZA
and 137, 153 and 173 mg/g for FeA at 30, 40 and 60oC, respectively. Obtained results were
fitted with Freundlich and Langmuir model, and for all temperatures the best fits were obtained
with Freundlich model (R2>0.97)
Effects of structural and textural grain characteristics on leaching of sulphide minerals from a polymetallic concentrate by sodium nitrate and sulphuric acid solution
No full textIn this paper, the influence of structural and textural characteristics of sulfide minerals on their leaching from a polymetallic concentrate by sulfuric acid and sodium nitrate solution is presented. The starting material was Pb-Zn-Cu sulphide polymetallic concentrate enriched during the flotation of a polymetallic ore in the "Rudnik" flotation plant (Rudnik - Serbia). Leaching experiments were carried out in a closed glass reactor, which provides stable hermetic conditions and allows heating at constant temperature. Chemical, XRD, qualitative and quantitative microscopic and SEM/EDX analyses were used to characterizes samples of the polymetallic concentrate and leach residue. It was determined that chalcopyrite, sphalerite, galena, pyrrhotite and quartz were present in the polymetallic concentrate. The content of sulphide minerals was 69.5%, of which 60.9% occurred as liberated grains: 88.3% of chalcopyrite, 59.3% of sphalerite, 25.1% of galena and 51.6% of pirrhotite. The rest of chalcopyrite, sphalerite, galena and pirrhotite grains were in the forms of inclusions, impregnations, and simple and complex intergrowths. During the leaching process by sodium nitrate and sulphuric acid solution, it was shown previously that the leaching rate of sulphide minerals decreased with time while a part of the sulphide minerals remained in the leach residue. After leaching at 80 degrees C for 120 min, the yields were 69.8, 82.7 and 67.1% for Cu, Zn and Fe, respectively. Lead, in the form of insoluble anglesite, remained in the leach residue. In addition to the anglesite, unleached sulfide minerals and quartz, elemental sulfur was found in the solid residue. The content of sulphide minerals was 35% of which 33.7% minerals occur independently. In specific, 54.7% of chalcopyrite, 31.9% of sphalerite, 8.2% of galena and 37.6% of pyrrhotite appear as separate grains with highly corroded surfaces. Therefore, the structural assembly of sulphide grains in the polymetallic concentrate is favourable and it is not the reason for the observed decrease in the leaching rate in the final process stages. The obtained findings may be explained by the presence of elemental sulphur that is formed during the reaction and precipitated at the grain surfaces, thus creating a diffusion barrier for the leach solution
In vitro investigation of electrophoretically deposited bioactive hydroxyapatite/chitosan coatings reinforced by graphene
No full textGraphene (Gr) and natural polymer chitosan (CS) were introduced to hydroxyapatite (HAP) to produce a three-component composite coating, which was fabricated by cathodic electrophoretic deposition on Ti substrates in an ethanol suspension. These HAP/CS/Gr coatings were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and electrochemical measurements and found that the graphene into HAP/CS composites significantly improves their morphology, thermal stability, and bioactivity. Both HAP/CS and HAP/CS/Gr composite coatings are classified as non-cytotoxic when tested against healthy peripheral blood mononuclear cells (PBMC), while antibacterial activity against Staphylococcus aureus and Escherichia coil could not be verified
To what extent do soft mechanical activation and process parameters increase the efficiency of different zeolite/phosphate rock fertilizer mixtures? (vol 23, pg 1, 2017)
No full textDissolution of copper from smelting slag by leaching in chloride media
No full textLeaching of copper smelting slag in chloride media was studied. The lixiviants used were aqueous solutions of hydrochloric acid (0.5-2.0 M HCl) as well as hydrogen peroxide and hydrochloric acid (0.5-3.0 M H2O2, 1.0 M HCl). The maximum final copper extraction from the slag of 73% was attained with 3 M H2O2, at room temperature after 120 minutes of reaction. At the same time, 55% of the iron from the slag was also dissolved. The copper extraction increased during the first 60 minutes of reaction and essentially ceased thereafter. Because of a rapid catalytic decomposition of hydrogen peroxide, it should be added continuously to the leach suspension rather than at once at the beginning of the experiment. In fact, it appears that almost complete dissolution of copper from the slag is achievable after about 4 hours of leaching by implementing the method of continuous lixiviant addition. Also, it seems that the final iron extraction could be limited to as low as 20% by using this method
Phase equilibria study and characterization of the alloys in the BiCu0.5Ni0.5 section of the Bi-Cu-Ni system
No full textTernarni Bi-Cu-Ni sistem je veoma značajan zato što njegove legure pripadaju grupi potencijalnih, naprednih bezolovnih lemnih materijala na bazi Cu-Ni, za primenu na povišenim temperaturama. U ovom radu predstavljeni su rezultati ispitivanja fazne ravnoteže i karakterizacije legura u preseku Bi-Cu0.5Ni0.5 iz ugla bizmuta sa molskim odnosom Cu:Ni = 1:1. Ispitivanja su sprovedena korišćenjem različitih eksperimentalnih metoda - DTA, DSC, SEM-EDS, merenjem tvrdoće i električne provodljivosti, dok je termodinamički proračun urađen u skladu sa CALPHAD metodom primenom PANDAT programa.The Bi-Cu-Ni system is a very significant, because its alloys belong to the group of potential Cu-Ni-based advanced lead-free solder materials for high temperature application. The results of phase equilibria investigation and characterization of the alloys selected in the Bi-Cu0.5Ni0.5 section from bismuth corner with molar ratio Cu:Ni = 1:1, are presented in this paper. The investigations were performed using different experimental methods - DTA, DSC, SEM-EDS, hardness and electrical conductivity measurements, while thermodynamic calculation was done according to the CALPHAD method using PANDAT software
The effect of mechano-chemical activation and surface treatment of limestone filler on the properties of construction composites
No full textThe effect of the combined actions of milling and hydrophobization procedures applied in construction composites synthesis was investigated. The mortars were prepared with cement (CEM I 42.5) and calcite aggregate complying the standard 1:3 mix ratio. The limestone filler (10 wt%) was added to the mixture upon its mechano-chemical activation in an ultra-centrifugal mill. The activation variables (milling time, rotor velocity, sieve mesh size) were altered to achieve the optimal quality of the powder. The treatment was optimized via chemometric tools. The r(2) values (0.955-0.998) of second order polynomial models accurately predicted the output and the Standard score analysis chose the optimal activation parameters: 4.25 min; 48.58 m/s and 80 gm sieve. The selected filler and all three aggregate fractions were coated with stearic acid via dry procedure. The mortar mixes, prepared with uncoated (M1) and coated (M2) aggregate and filler, were cured for a period of 28 days during which compressive strength and water absorption were monitored. The dimensional changes in mortars were estimated via TMA dilatometer measurements. Thermo-analytical methods (DTA/TGA) were applied in the thermal behavior analysis. Mineralogical and morphological changes in the structure of hardened composite were detected by XRD and SEM, respectively. Limestone aggregate led to lower final compressive strengths in mortar, but it produced an infinitesimally small shrinkage at 1000 degrees C. The hydrophobization via stearic acid initiated the decrease in water absorption and formation of needle-like micro-network that filled structural voids reducing open porosity. The assessment of the effects of limestone utilization as a filler and as an aggregate on the mortar performances confirmed that this novel water-repellent composite is applicable in structural design
To what extent do soft mechanical activation and process parameters increase the efficiency of different zeolite/phosphate rock fertilizer mixtures?
No full textIn order to obtain effective mineral fertilizer, different mixtures of phosphate rock (PR) with natural clinoptilolite (Cp) and NH4+ saturated clinoptilolite (NH4-Cp) were subjected to soft mechanical activation. Mean concentrations of P released from mechanically activated (MA) substrates, MACp/PR and MANH(4)-Cp/PR, ranged between 281-3.19 mg L-1 and 202-774 mg L-1, respectively. These are 10 to 15 times higher P concentrations than those released from the corresponding non-activated mixtures. Solution Ca2+, K+, Na+ and Mg2+ concentrations varied according to the composition of the mixtures and the contact time between the two minerals within their optimal values required for plant growth. The obtained results suggest that the efficiency of the NH4-Cp/PR mixtures can be significantly increased by the proposed mechanical activation. Influence of process parameters on the observed concentrations of nutrients was shown using multivariate statistics. The highest fertilization potential demonstrated MANH(4)-Cp/PR mixture with the largest NH4-Cp share and the longest proposed mixing time
Ternary bi-cu-ni alloys - thermodynamics, characterization, mechanical and electrical properties
No full textThe Bi-Cu-Ni ternary system belongs to the group of potential Cu-Ni-based advanced lead-free solder materials for high temperature application. The paper shows results of the thermodynamic calculations using general solution model along the line with the molar ratio of Cu: Ni = 1:1. The experimental part shows thermal, structural, electrical and mechanical properties based on differential scanning calorimetry (DSC), scanning electron microscopy with energy dispersive spectrometry (SEM-EDS), electroconductivity and hardness measurements of the alloys selected in the section from bismuth corner with molar ratio Cu: Ni = 1:1, Cu: Ni = 3:1, and Cu: Ni = 1:3
Evaluation of low-cost sorbents as potential materials for in situ remediation of water contaminated with heavy metals
No full text"The aim of this paper was to examine the possibilities of using various low-cost sorbents as material
for permeable reactive barrier for efficient removing of lead, cadmium, copper and zinc from contaminated
water. Natural zeolite (NZ), iron-modified zeolite (IMZ), apatite, concentrated apatite, kaolin and raw bentonite
were examined. The batch test evaluation was used to investigate capturing of heavy metals from contaminated
water onto sorbents, as well as retention strength of saturated sorbent. The change of pH values during satura-
tion and leaching of heavy metals was performed in a slightly acidic to neutral area, confirming buffering abilities
and environmental acceptability of all investigated sorbents as a material in PRB for protection of groundwater
as the most valuable natural resources. The highest saturation ability towards all examined heavy metals was de-
tested with raw bentonite and IMZ. Leaching of heavy metals at pH=2.94-2.98 was confirmed in all saturated
sorbents, while at pH=6.07-6.46 it was not detected, except of Pb and Cd in raw bentonite. From the obtained
results, the recommendation for selection of sorbent for treatment of water contaminated with lead, cadmium,
cooper and zinc is given