جستجوی مقالات مرتبط با کلیدواژه « هم دما » در نشریات گروه « شیمی »

In this research, the adsorption of nickel ions in the batch system by orange peel carbon has been investigated and the effect of factors such as pH, contact time, initial concentration of nickel in solution, adsorbent amount, and the temperature has been considered. The surface details and functional groups were investigated by SEM and FTIR analyzes, respectively. In the study of the effect of pH, the highest percentage of nickel uptake for orange peel carbon occurred at pH = 6, which is equivalent to 58 mg/g. With increasing the contact time between the adsorbent and the solution and after 210 minutes, the adsorption percentage increased to 98.57%. In the study of the effect of the initial concentration of nickel in the range of 20 to  150 mg/L, the results showed that with increasing concentration, the percentage of adsorption decreased from 98% to 96%, and with increasing the amount of adsorbent from 0.01 to 0.1 g per 25 ml. Nickel solution, the adsorption percentage increased from 90% to 98%. The effect of temperature showed that with increasing the temperature from 25 to 45°C, the percentage of adsorption decreased from 99% to 97.8%. Thermodynamic properties were studied at three temperatures of 25, 35, and 45°C. The negative free energy value of the standard Gibbs (∆ Go) which is equivalent to -121.3 kJ / mol, indicates that the adsorption process is spontaneous and physical. In the kinetic study of the contact time effect, it was observed that the results fit well with the second-order kinetic model with a correlation coefficient of 99%. In investigating the effect of the initial concentration of nickel in solution and fitting experimental data with Langmuir, Freundlich, Temkin, Dubin Radushkovich isotherms, and according to the values ​​obtained at R2, Freundlich's isotherm had the highest compatibility with 100% correlation coefficient.

Cyanide is one of the toxins and different ways to reduce it have been studied. These include ozone oxidation methods, ultraviolet radiation degradation, alkaline chlorination, and hydrogen peroxide degradation. Each of these methods has various disadvantages and advantages, but among them, surface adsorption is an effective and efficient method. On the other hand, zeolites, which are crystalline aluminosilicate and juicy alkali and alkaline earth metals, have the ability to absorb cations and anions. To prepare a cyanide solution, it was used sodium cyanide salt based on the standard method In this work, it has been studied the adsorption of cyanide ion from aqueous solutions using zeolite nanoparticles and the factors affecting on it. In this study, the factors of the effect of the initial pH of the solution, the effect of the initial concentration of the solution, the effect of the adsorbent amount, the effect of the contact time and the effect of temperature on the surface adsorption of cyanide ions with the nano-adsorbent zeolite clinoptilolite were investigated. And after the studies, the optimal and appropriate values for each of the effective parameters pH=6, contact time 40 min, adsorbent dosage 1g/l, temperature 22°C and initial concentration of 150 mg/l. Under these optimal conditions, the highest percentage of anion cyanide uptake was obtained on the nano-adsorbent of zeolite clinoptilolite 85%. The relationship between empirical data and the equation of Langmuir, Freundlich and Tamkin equations was also investigated. The R2 values for Langmuir, Frondelich, and Temkin's alliances were 0.8337, 0.9837, and 0.99, respectively, indicating that there was a greater match between the experimental data and the Temkin temperature than the other two.

In this study, the multi-walled carbonnanotubes (MWCNTs) were functionalized and then were characterized by the several techniques such as :Fourier-transform infrared spectroscopy analysis, X-ray powder diffraction ,scanning electron microscopy, Brunauer-Emmett-Teller and Barett-Joyner-Halenda analysis and particle size analyzer. Then, the functionalized multi-walled  carbonnanotubes were used for removing Cr (III) ions from aqueous media. Several adsorption experiments were carried out for evaluating the adsorption capacity of the synthesized FMWCNTs. For adsorbing Cr (III) ions from aqueous solutions. The experimental results showed that the synthesized FMWCNTs have a good capacity for Cr (III) ions adsorption. The effect of the initial concentration of the sorbate, sorbent dosage, temperature, pH  and contact time on the removal  percentage of Cr ( III) ions on to the FMWCNTs and the adsorption capacity of the prepared adsorbent was studied and the optimum value of each of them was determined.Based on the experimental results, the isotherm models evaluation was also performed and the obtained results revealed that the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models can be used for interpretation the experimental results. Kinetic study showed that the kinetic results of this research can be compared with the pseudo first order, Elovich and intraparticle diffusion kinetic models and selecting ones with the largest R2. In addition, adsorption thermodynamic study ,on the basis of the adsorption capacity dependence on the  temperature,was performed. The obtained results showed that the considered adsorption process at the used temperature range is exergonic G0ad<0 and exothermic H0ad<0 and with a decrease in the randomness (S0ad< 0). Based on the magnitude of H0ad, one can claim that the studied adsorption may be a physical adsorption one.

In this research, adsorption of Zinc ion was investigated at batch system using spirulina microalgae and Magnetic microalgae. The effect of important parameters such as pH of the solution, absorbent contact time, the initial concentration of Zn(II) ion, adsorbent dosage and temperature were investigated on The removal efficiency and  adsorption capacity. Also adsorbent features were studied by using SEM photographs and FT-IR spectroscopy. The maximum Zinc ion adsorption occurred in pH=6. The optimum adsorbent dosages were determined 0.03 g for spirulina microalgae and Magnetic microalgae. So at optimum pH and adsorbents dosage for 150 mg/l initial zinc ion concentration 84.43% and 96.56% of removal efficiency was obtained for spirulina microalgae and Magnetic microalgae, respectively. Removal efficiency increased by increasing contact time between adsorbent and solution and after passing 10 min for spirulina microalgae and Magnetic microalgae reached to equilibrium. Examining kinetic models showed that pseudo-second order kinetic model had best fit for adsorbents. In investigating Zinc ion initial concentration in range of 50-300 mg/l, results showed by increasing initial concentration, efficiency decreased. Also experimental data of spirulina microalgae and Magnetic microalgae solutions had best fit by sips and Langmuir, respectively. Investigating temperature effect showed, by increasing temperature, removal efficiency decreased for spirulina microalgae and Magnetic microalgae. The thermodynamic parameter was studied in 298, 303, 313 and 323 Kelvin.

Throughout the years, humans have entered the environment with potentially hazardous wastes such as heavy metals and radioactive substances, so that it has a direct impact on human health and existing ecosystems. Hence, the investigation on the necessary strategies to control and eliminate these hazards has been the goal of various researches. In this study, the elimination of cobalt 60 radionuclides was investigated due to their abundance in the wastewaters of nuclear industries such as spent fuel reprocessing plants and nuclear power plants. Thus, novel surface-modified hematite nanoparticles (α-Fe2O3 NPs) were prepared by hydrothermal method at 250 °C and using iron(III) chloride hexahydrate (FeCl3.6H2O) and oleic acid (C₁₈H₃₄O₂) as raw materials for the removal of cobalt-60 radiostations from aqueous solutions. The synthesized α-Fe2O3 NPs were characterized by XRD, FT-IR, SEM, TEM, and BET. According to the results, the synthesized nanocrystals were more (90%) of nanorods 60-30 nm, along with irregular hexagonal nanoscale particles at a thickness of 40- 100 nm distributed among them.  The specific surface area was determined 31.29 m2/g and the effect of some variables such as pH, adsorbent weight, initial concentration of cobalt-60 radio cations, temperature, and contact time was significant on the absorption process. The optimized condition for cobalt-60 removal from aqueous solution was obtained in 25±1 °C , initial radio cation concentration of 1 mg/L, pH 6.5, contact time of 2 h, and nano α-Fe2O3 sorbent concentration of 20 mg/L. On the other hand, the Redlich-Peterson isotherm model was suitable for describing homogenous cobalt-60 adsorption with the maximum uptake capacity 142.86 mg/g at 25±1 °C. In contrast, analysis of experimental data showed that the cobalt-60 adsorption onto the synthesized nano α-Fe2O3 well fitted the Ho model as linear pseudo-second-order kinetics. Therefore, it can be concluded that the synthesized novel surface-modified α-Fe2O3 NPs is an effective, promising, and environment-friendly adsorbent with high capability in the removal of cobalt-60 radionuclides from aqueous solutions such as wastewaters.

Cobalt-aluminum layered double hydroxide was successfully prepared by mechano-chemical method. It was synthesized in a mortar by manually grinding the hydrated cobalt and aluminum nitrate salts with sodium hydroxide. According to FT-IR, XRD and BET, the synthesized sample showed characteristic of layered double hydroxides. The as-prepared Co-Al-LDH exhibited a high adsorption activity to the Methyl Orange dye. Batch adsorption experiments were carried out at room temperature under various conditions such as contact time, adsorbate mass and pollutant concentration. Langmuir and modified Freundlich isotherms were also used to investigate adsorption. The results of isotherm studies showed that adsorption of dye onto LDH fits to the modified Langmuir equation with sorption capacity of 656.96 mg/g.

Zinc oxide ZnO is one of the most widely used semiconductor metal oxides with extensive applications in the manufacture of optical instruments do to its unique properties. The specificity of the films prepared by the use of this material depends directly on its deposition conditions. In this work, during the preparation of ZnO films by the pulsed laser deposition method, we fixed the volume and pressure parameters and considered the temperature factor as a varied factor by cooling down the substrate temperature to investigate the effect of thermodynamic parameters. The results of UV-visible absorption spectroscopy, microscopic and SEM images of the samples indicate that the quality of the films improves effectively under stable thermodynamic conditions.

In this study, release mechanism of cisplatin anti-cancer drug inside Single-Walled Carbon NanoTube (SWCNT) through Ag-nanowire diffusion and also, the effects of nanotube diameter and temperature on the rate of release process was investigated via Molecular Dynamics (MD) simulation. The results showed that the van der Waals interaction between the Ag-nanowire and the SWCNT act as the driving force for the drug release which the highest of the release rate of cisplatin was observed in the body temperature and in the SWCNT with a larger diameter. Finally, the kinetics of drug release is fast and not related to the structural parameters of the nanotube and temperature, significantly

The utilization of polymer-clay composites as adsorbents in the remediation of polluted water has been the subject of many recent research studies. In the present work, poly(acrylic acid) –bentonite (PAA-Bentonite), was synthesized and its chromium ion adsorption performance was investigated. The adsorption behavior of the composite towards chromium from aqueous solution was studied under varying conditions such as initial concentration of chromium (5–500 mg/L) and contact time (30–1440 min). Experimental equilibrium data were fitted to Langmuir and Freundlich isotherm models by non-linear regression method, however, the adsorption equilibrium data were well interpreted by the Langmuir model. The maximum capacity of PAA-Bentonite toward chromium was 29.55 mg/g at 25 °C, which was much higher than that of the Bentonite (1.3 mg/g). The maximum chromium removal efficiency of 85 % was achieved by the composite at 25°C with 30 min contact time for an initial metal concentration of 50 mg/L. The adsorption kinetics followed both pseudo first-order and pseudo second-order models.The results showed the high potential of PAA-Bentonite composite for the removal of chromium ions from aqueous solution.