Modular connectors are applied by computer users, and they can be metallic secondary sources containing metals such as gold and copper. Because gold is a micro-component, the solution obtained after ...the pin digestion contains a low concentration of gold(III) ions, and efficient and selective sorbent should be used for gold(III) ion recovery. The selective removal of small amounts of gold(III) from 0.001-6 M hydrochloric acid solutions using pure and solvent-impregnated macroporous polystyrene crosslinked with divinylbenzene sorbents (Purolite MN 202 and Cyanex 272) is presented. Gold(III) ions were recovered effectively from the chloride solution after the digestion of the modular connector RJ 45 (8P8C) using Purolite MN 202 after the impregnation process. The dependence of the recovery percentage (R%) of gold(III) on the contact time was determined. The highest value of gold(III) ion sorption capacity (259.45 mg·g
) was obtained in 0.001 M HCl for Purolite MN202 after the Cyanex 272 impregnation. The results can be applied to gold recovery from e-waste. The presented method of gold recovery does not generate nitrogen oxides and does not require the use of cyanides.
This study concerns the fabrication of CTAB- and N,N-dimethyltetradecylamine-grafted zirconia and evaluation of their ability to adsorb vanadium ions. The effectiveness of ZrO2 functionalization and ...the different nature of the modifiers used were confirmed by differences in the porosity (ZrO2: SBET = 347 m2/g; ZrO2-CTAB: SBET = 375 m2/g, ZrO2–NH+: SBET = 155 m2/g), types of functional groups, and isoelectric points (the ZrO2 and CTAB-modified samples have IEPs = 3.8 and 3.9, ZrO2–NH+ has IEP = 7.1) of the prepared adsorbents. The designed materials were tested in batch adsorption experiments involving the removal of vanadium ions from model wastewaters at various process parameters, among which pH proved to be the most important. Based on equilibrium and kinetic evaluations, it was proved that the sorption of V(V) ions followed pseudo-second-order and intraparticle diffusion models, and the data were better fitted to the Langmuir model, suggesting the following order of the sorbents in terms of favorability for V(V) ion adsorption: ZrO2–NH+ > ZrO2 > ZrO2-CTAB. The estimated maximum monolayer capacity of ZrO2–NH+ for V(V) (87.72 mg/g) was the highest among the tested materials. Additionally, it was confirmed that adsorption of V(V) ions onto synthesized materials is a heterogeneous, exothermic, and spontaneous reaction, as evidenced by the calculated values of thermodynamic parameters. The key goals included the transfer of experimental findings obtained using model solutions to the adsorption of V(V) ions from solutions arising from the leaching process of spent catalysts. The highest adsorption efficiencies of 70.8% and 47.5% were recorded for the ZrO2–NH+ material in acidic solution; this may be related to the protonization of –NH+ groups, which favors the sorption of V(V) ions. Based on desorption tests as well as the results of infrared and X-ray photoelectron spectroscopy, irrespective of the process conditions, the physical nature of the adsorbent/adsorbate interaction was confirmed.
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•Surface grafting of zirconia with CTAB and N,N-dimethyltetradecylamine was proved.•Modified ZrO2 adsorbents exhibit enhanced adsorption ability towards V(V) ions.•Maximum monolayer capacity of ZrO2-based adsorbents for V(V) ions is 87.72 mg/g.•Vanadium ions adsorption is heterogeneous, exothermic and spontaneous reaction.•The physical nature of adsorbent/adsorbate interaction was proved.
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The development of high performance, sustainable and inexpensive catalyst for environmental applications is a highly innovative and promising approach to meet the increasing demands ...from society on water treatment and pollution remediation. Carbon microtube (CMT) synthesized from cotton waste was successfully developed by direct pyrolysis of cotton bundle in argon atmosphere in different carbonization temperature (900, 1100, 1300 and 1500 °C). Carbon microtubes have been used for removal of Bisphenol A (BPA) in wastewater and showed the optimum performance for CMT11 and CMT 13. The mechanism involved in this efficient water treatment was ascribed to the strong π-π interaction and hydrogen bonds between CMT and BPA. Given the repeatability, high removal performance and cost effectiveness of the cotton based carbon microtubes when compared to other well-known catalysts such as carbon nanotubes, the carbon microtubes demonstrated great potential as low-cost, sustainable and effective catalyst for wastewater treatment.
Purpose
Heavy metal soluble forms pose a threat to plants, soil microflora, and microfauna. To limit their toxicity and mobility, various immobilizing additives are being developed. The main aim of ...the study was to determine the influence of soil flocculant (cationic polyacrylamide (CtPAM)) on the hexavalent chromium ion reduction and accumulation on the kaolinite surface. In this way, the efficiency of the selected polymer conditioner in the soil remediation was determined.
Materials and methods
The adsorbed amounts of Cr(VI) and CtPAM on the kaolinite surface was determined spectrophotometrically (spectrophotometer UV/Vis) using specific indicators. The structure of electrical double layer formed on the kaolinite surface in the mixed system of cationic polyacrylamide and Cr(VI) ions was described based on the adsorptive measurements, zeta potential measurements, as well as potentiometric titration. The kaolinite aggregation in the presence of CtPAM and/or Cr(VI) ions was determined spectrophotometrically and proved using SEM microscopy. The reduction process of Cr(VI) to Cr(III) occurring in the adsorption layer was determined by diffuse reflectance spectroscopy (DRS).
Results and discussion
The obtained results indicated that cationic polyacrylamide contributes to Cr(VI) reduction to Cr(III) form in the kaolinite suspension. This heavy metal ions are strongly adsorbed by the applied clay mineral, especially at pH 5 (then the Cr(VI)-adsorbed amount equals 5.42 mg/g). The CtPAM addition favors the Cr(VI) ion immobilization on the kaolinite surface. In the conditioner presence, the heavy metal-adsorbed amount is even at 7.34 mg/g. The adsorption of CtPAM and chromium(VI) ions induces changes in the kaolinite surface charge density and electrokinetic potential. What is more, both substances favors the kaolinite aggregation.
Conclusions
Cationic polyacrylamide may be considered a substance reducing the toxicity of chromium(VI) ions in the natural environment and decreasing their availability for soil organisms. It can improve the soil structure (by stimulating aggregation) and reduce environment pollution with heavy metals simultaneously.
Graphical abstract
Removal of chromium(VI) ions and their reduction were studied on the anion exchanger Dowex PSR-2 in the pH range from 1.5 to 10. The parameters of Cr(VI) sorption process on the anion exchanger were ...calculated based on the most popular isotherm models such as: Freundlich, Langmuir, Temkin, and Dubinin-Radushkevich (D-R). The Langmuir isotherm was the most appropriate to describe Cr(VI) sorption. The Cr(VI) uptake by Dowex PSR-2 was found to follow the pseudo-second-order rate kinetics. Reduction of chromium(VI) in the pH range 1.5-10 was observed using the HPLC-ICP-MS (high-performance liquid chromatography-inductively coupled plasma-mass spectrometry) method. Oxidation of tri-n-butyl quaternary ammonium groups during the chromate (VI) removal process was observed.
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•Combustion-synthesized Li-Mn spinel-based cathode nanostructures.•Nanorods resulted in better electrochemical behavior vs. bulk commercial spinels.•Doping with Cu and Αl ions further ...improved the insertion/extraction process of Li.•Exceptional stability obtained at high rates.•Li1.068Al0.099Mn1.901O4 nanostructure showed the highest electrochemical reversibility.
In this work we report the physicochemical and electrochemical properties of Li-Mn spinel-based cathode nanostructures in comparison with the corresponding commercial powder. Well dispersed nanorods (diameter of 17–32nm and average length of 150nm) are formed in the case of pure Li1.276Mn2O4, which result in better electrochemical performance compared with the bulk commercial electrode of lithium-ion batteries. Modifications of the structure via substitution with Cu and Αl ions at the octahedral sites further improve the insertion/extraction process of lithium cation, especially in the case of Li1.068Al0.099Mn1.901O4. Long term stability test at different charge/discharge rates show that this nanostructure has the highest electrochemical reversibility (∼11.5% capacity loss) among the samples studied followed by Li1.281Cu0.086Mn1.914O4 (∼22.5% capacity loss), while the nanostructured Li1.276Mn2O4 and the commercial LiMn2O4 spinel have ∼28.4% and ∼32.4% capacity loss, respectively.
Understanding how humans evaluate credibility is an important scientific question in the era of fake news. Source credibility is among the most important aspects of credibility evaluations. One of ...the most direct ways to understand source credibility is to use measurements of brain activity of humans who make credibility evaluations. This article reports the results of an experiment during which we have measured brain activity during credibility evaluation using EEG. In the experiment, participants had to learn source credibility of fictitious students based on a preparatory stage, during which they evaluated message credibility with perfect knowledge. The experiment allowed for identification of brain areas that were active when a participant made positive or negative source credibility evaluations. Based on experimental data, we modeled and predicted human source credibility evaluations using EEG brain activity measurements with F1 score exceeding 0.7 (using 10-fold cross-validation). We are also able to model and predict message credibility evaluations with perfect knowledge, and to compare both models obtained from a single experiment.
Selection of livestock has not only led to changes in the level of their performance but also modified their behavior. As a result, within a single species, we have to deal with different behaviors ...of different breeds. In our study, we assumed that the different behaviors within a species are due to differences in the morphology and physiology of behavior-related systems. Two breeds of hens were used as a model: the highly reactive, fearful and high-performance Leghorn breed and proactive, unselected Green-legged Partridge breed. The higher reactivity and fearfulness of Leghorn hens in comparison to the Green-legged Partridge breed may be related to the greater number of neurons in the paraventricular nucleus and anterior hypothalamus and the higher content of zinc and iron in the brain, as these elements are involved in neuronal conduction and myelination processes. The reactive behaviours of Green-legged Partridge hens may be associated with the lower number of neurons in the paraventricular nucleus and the anterior hypothalamus and the higher concentration of dopamine and copper ions in the brain. The analyses confirmed the hypothesis of the existence of interbreed differences in the morphology and physiology of behaviour-related systems, which most probably emerged through unintentional and correlated selection towards high production performance. Consequently, attention should be drawn that the selection of a given genotype (breed) towards a specific environment could lead to creation of highly specialised lines that may not achieve homeostasis in every maintenance system.
A new acrylic anion exchanger with both tertiary and quaternary ammonium as well as ketone groups in the structural unit has been prepared by the nucleophilic substitution reaction of aminolyzed ...vinylacetate:acrylonitrile:divinylbenzene copolymer of porosity structure in the swelling state with 2-chloroacetone as a halogenated compound. The new compound exhibits better qualities of strong base exchange capacity than the weak base anion exchangers. The obtained acrylic anion exchanger was used to remove Cr(VI) from the aqueous solution. Batch adsorption studies have been carried out to determine the effect of contact time, concentration of hexavalent chromium in the solution and pH on the sorption capacity. The kinetic parameters were determined on the basis of the static results. The thermodynamic parameters of Cr(VI) sorption process on the anion exchanger were calculated based on the Langmuir and Freundlich isotherms. Sorption was studied in the pH range of 1.5–7 and it was found that it depends on the solution acidity. At the pH values of 3.5 and 7 the anion exchanger exhibited large values of chromium sorption capacity. The speciation of chromium was investigated in the studied pH range by the Diffuse Reflectance Spectroscopy (DRS) method. Reduction of chromium(VI) to chromium(III) under acidic conditions was observed. The performed acrylic strong base anion exchanger is superior compared to the conventional one based on the styrene:divinylbenzene matrix due to its ability for reposition of the long spacer arm for providing exchange sites, hydrophilic character of matrix, and possible hydrogen bonds provided by carbonyl functional groups.
The Plastic Optical Fiber (POF) sensors can be low-cost or cost-competitive solutions to other sensing techniques due to their advantages, such as immunity to electromagnetic interference, ...compactness, lightweight, multiplexing capabilities. Scientists and engineers have already developed POF sensors capable of sensing strain, deflection, pressure, refractive index, and more. These make them suitable for structural health monitoring, medicine, environmental, chemical applications. Real-life implementations are subjected to various external factors, including vibrations, environmental conditions, light source fluctuations, component aging. Such factors may influence the fabricated sensor performance. To compensate for these factors, the academic community has explored solutions that utilize an optical coupler to split the optical signal, which then serves as a reference. For large-scale applications, these increase costs significantly. This research explores the influence of extrinsic losses (introduced by manufacturing procedures) and environmental conditions (ambient temperature) on the transmission capacities of the refractive index (RI) evanescent wave absorption POF sensor. The sensor was fabricated using polishing methods and characterized by means of transmission capacities and RI sensitivity (in the range of 1.3330 – 1.4167) at different fabrication stages and extreme ambient temperatures. The findings presented in this paper will be used for the further development of evanescent wave absorption POF sensors, which can be used e.g. for measuring solution concentration, water contamination, etc.
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