Adsorption Of Zinc Ions Research Articles

A Study of Zn2+ ions adsorption by native and chemically modified pea (Pisum sativum) pods

The paper deals with a study of Zn2+ ions adsorption by native and modified fine-cut pea (Pisumsativum) pod shells. The sorption material under study was treated using 1%, 2% and 3% NaOH or H2SO4 solutions. Isotherms of Zn2+ ions adsorption by native and treated pea pod shells were plotted and calculated using the Langmuir, Freundlich, Tyomkin, and Dubinin-Radushkevich models. It was determined that the isotherm of zinc ions adsorption by native shells of pea pods is most accurately described by the Langmuir model, by modified shells – by the Freundlich model. According to the values of the adsorption energy and the Gibbs energy, the adsorption is a physical process. The paper provides data on the degree of crystallinity, elemental analysis, and IR spectra of native and treated pea pods.

Investigation of the adsorption of copper and zinc ions by sorbents based on plant waste – cake and husk of sunflower seeds

Investigation of the adsorption of copper and zinc ions by sorbents based on plant waste – cake and husk of sunflower seeds. Nowadays water bodies contain a huge amount of pollutants that are products of human activity. Heavy metals exceeding the maximum permissible concentrations (MPC) are among the most common pollutants in wastewater. The most popular and effective ways to reduce the concentration of heavy metal ions in wastewater are sorption methods of purification. Therefore, there is an urge to create new adsorbents that have a lower price than existing on the market, as well as are effective and environmen-tally friendly. The aim of this work is to study the adsorption activity of waste based on husk (SH) and cake (SC) of sunflower seeds in relation to copper and zinc ions. The maximum degree of extraction using SH reaches (88 ± 3.43) % for Cu 2+ and (81.4 ± 5.53) % for Zn 2+ . Grinding the SH leads to an increase in the extraction degree up to (93 ± 2.57) % for Cu 2+ and to (89 ± 2.35) % for Zn 2+ . In the case of SC, the maximum extraction degree reaches (72 ± 4.98) % for Cu 2+ and (80 ± 3.07) % for Zn 2+ . Sorbents were modified in order to increase the extraction degree. The degree of extraction of Cu 2+ and Zn 2+ ions by SH carbonated coal reaches (95±2,29)% for Сu 2+ and (96±3,41)% for Zn 2+ . In the case of SC carbonated coal, the extraction degree reaches (93±2,98)% and (35±4,24)% for Cu 2+ and Zn 2+ respectively. The extraction degree of Cu 2+ and Zn 2+ ions by acid-treated SH and SC carbonated coals reaches 100%. As a result of studying the kinetics of the processes under study, it was found that the in-teraction is described by a pseudo-second order model in the case of the adsorption of: 1) Cu 2+ and Zn 2+ on the SH; 2) Cu 2+ on the SC. For the adsorption of Zn 2+ on the SC the pseudo-first order fits better. In the case of modified sorbents, the process is described by a pseudo-second order model for the adsorp-tion of : 1) Сu 2+ and Zn 2+ by acid-treated SH carbonated coal; 2) Сu 2+ and Zn 2+ by SC carbonated coal; 3) Zn 2+ ions by acid-treated SC carbonated coal; 4) Сu 2+ ions by SH carbonated coal. The pseudo-first order model describes the adsorption of Zn 2+ ions by HS carbonated coal and Сu 2+ ions by acid-treated CS carbonated coal. Key words: sunflower husk, sunflower cake, adsorption, copper ions, zinc ions, kinetics.

Synthesis and Characterization of Magnetic Nickel Ferrite-Modified Montmorillonite Nanocomposite For Cu (II) and Zn (II) Ions Removal From Wastewater

For the adsorption of copper (II) and zinc (II) ions from polluted water, an efficient inexpensive nanoadsorbent; nickel ferrite-modified montmorillonite nanocomposite was synthesized by co-precipitation of the mechano-chemically modified montmorillonite with the salts of nickel and iron. The natural MMT, modified MMT, and the synthesized nickel ferrite-modified montmorillonite (NiFe2O4-Mod MMT) nanoadsorbent were characterized by several techniques including Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray, surface area analysis, saturation magnetization, and surface zeta potential. Batch studies were carried out on the effect of various parameters including contact time, nanocomposite dosage, solution pH, metal ion initial concentration, and temperature on the adsorption process to optimize its conditions. The equilibrium state was reached after 60 min and 90 min of reaction for Cu (II) and Zn (II) ions, respectively. The optimum conditions were 0.1 g adsorbent dose, pH 5, 13 mg/L initial metal ion concentration, and 298 K temperature for copper (II) adsorption and 0.1 g adsorbent dose, pH 6, 6 mg/L initial metal ion concentration, and 298 K temperature for zinc (II) adsorption. Among the designed kinetic and equilibrium models, the pseudo-second-order kinetic model and Langmuir adsorption isotherm model have controlled the adsorption process for both metal ions. Furthermore, the adsorption mechanism and the reproducibility of the nanoadsorbent were investigated. The maximum adsorption efficiency was 99.23% and 91.67% of copper (II) and zinc (II) ions, respectively.

Study of adsorption of copper, lead, and zinc in their various chemical forms from the sediments of the Brahmaputra river, Assam, India

AbstractThe natural organic matter and the iron and manganese oxides are potential adsorbing agents of heavy metals in sediments and create a sink for them to control their bioavailability and mobility in the aquatic environment. The salinity and pH of the surrounding water highly affect the fixation of heavy metals on the river sediments. The adsorption of copper, lead, and zinc ions in the Brahmaputra river sediment is analyzed by batch techniques. The parameters controlling these metal ions adsorption are solution pH, contact time, adsorbent amount, and adsorbate concentration. The equilibrium adsorption capacities of the sediment particles of the various sizes (< 53, 53–73, and 74–149 μm) are measured for copper, lead, and zinc ions and extrapolated using linear Freundlich and Langmuir isotherms. The results provide strong evidence to support the hypothesis of adsorption mechanism. It is found that the extent of adsorption is increasing with decreasing particle size, and this may be attributed to the enhancement of the surface area available for adsorption to occur. The sediment is studied for metal speciation, for nine heavy metals, to explain their behavior in the five sequential extraction steps. This is an interesting study as zinc is present in the air, soil, water, and almost all food items, and industries naturally release zinc into the environment.

Super hydrophilic carbon fiber film for freestanding and flexible cathodes of zinc-ion hybrid supercapacitors

The oxygen-enriched super hydrophilic porous carbon fibers film has been synthesized as cathodes of ZHSCs via a facile electrospinning and subsequent nitric acid-treatment process. The prefabricated ZHSCs has a super long-term cycle performance. In particular, this cathode can operate stably under high load, different bending angles and a quasi-solid-state device, which increases its practical application potential. • Oxygen functional groups can improve the performance of carbon cathode. • The zinc-ion hybrid supercapacitors (ZHSCs) provide an ultralong-term lifespan. • The reaction mechanism between Zn 2+ and oxygen functional groups is proposed. • The ZHSCs can operate stably under harsh conditions. Aqueous zinc-ion hybrid supercapacitors (ZHSCs) are considered as promising candidates for flexible wearable energy storage devices. The key challenge is to develop carbon cathodes with high hydrophilicity, good flexibility and cycle stability. This paper reports a facile route to synthesize flexible oxygen-enriched carbon fiber films with super-hydrophilic character. ZHSCs with such carbon fiber cathodes achieve excellent energy and power densities of 97.7 Wh kg −1 /9.9 kW kg −1 with a long-term cycling stability (retention rate of 81% after 50,000 cycles). According to experiment analysis and theoretical simulations, it is discovered that the oxygen-containing functional groups on carbon fibers not only significantly improve their wettability, but also greatly facilitate the chemical adsorption of zinc ions and result in the enhanced capacities. In addition, those cathodes can operate well and stably not only under a high load of 20 mg cm −2 and a bending of 180°, but also in a quasi-solid-state device, promising for wearable electronic applications.

Removal of Zinc(II) Ions from Wastewater Using Natural Zeolites

The kinetics of the adsorption of zinc(II) ions by natural zeolites was studied using pseudo-first and pseudo-second-order kinetic models. The objects of study were zeolites mined in East Transbaikalia. The X-ray phase analysis and IR spectroscopy data confirmed that natural zeolite-containing rock samples have the following composition: calcium heulandite Ca[Al2Si7O18]⋅6H2O and impurity rocks, namely, sanidine KAlSi3O8 and cristobalite SiO2. The dependence of the adsorption value on zeolite grain size was studied. It was shown that the adsorption value increases 3.8 times and reaches 0.075 mol/g as the grain size decreases from 5 to 0.1 mm. The kinetic study of zinc(II) ions adsorption was performed at pH 5.0–5.4 in the temperature range of 298–318 K. In a zeolite–zinc sulfate aqueous solution system, the adsorption equilibrium time was 120 min. It was shown that the zinc(II) ions adsorption rate decreases under the temperature increase. It was established that the kinetics of zinc(II) ions adsorption is best described by a pseudo-second-order model, the correlation coefficient values varying in the range of 0.998–0.999. The highest adsorption rate constant value of 0.446 g/(mmol⋅mm) corresponds to the temperature of 298 K. It was shown that zeolites demonstrate the highest adsorption value towards heavy metal ions at the temperature of wastewater. The proof-of-principle studies were performed to establish the feasibility of the recovery of copper(II), nickel(II), and zinc(II) ions from wastewater produced by galvanic manufacture using the studied minerals. The treatment process was performed under the conditions determined as optimal for model solutions. The efficiency of heavy metal ions removal was 85–89%.

Synthesis and characterization of magnetic activated carbon from Ceiba pentandra fiber for zinc ion removal

One of the heavy metals contained in the electroplating industrial wastewater is zinc. Adsorption is found to be one of the most effective methods for zinc ion removal from aqueous solution due to low cost and simple to operate. The main purpose of this study was to use cotton (Ceiba pentandra) fiber as a precursor to developing a magnetic activated carbon (MAC) for zinc ion removal. The activation process was carried out using potassium hydroxide (KOH) by conventional heating using a tubular furnace at a temperature of 500°C for 2 hours under a stream of nitrogen (N2), while the magnetization process was carried out using co-precipitation method. The adsorption of zinc ion onto MAC was recorded to be 96% at a solution pH of 5 and contact time of 180 min. The adsorption of zinc onto AC is fitted well by the Freundlich isotherm model, while the zinc-MAC system is described well by the Langmuir isotherm model. Meanwhile, the pseudo second order kinetic model is suitable for AC and MAC. Owing to low cost and high efficiency, MAC prepared from Ceiba pentandra fiber can be used as an effective adsorbent for zinc ion removal from industrial wastewater.

Adsorption affinity of Zn (II) ions for nanostructured zirconium phosphate/silica or titania composites

The paper presents the kinetics of Zn (II) ions adsorption as well as its dependence as a function of pH on nanostructured zirconium phosphate and its composites with silica and titania. The nanostructured zirconium phosphate-containing composites were obtained by mechanical processing in the Pulverisette-7 (Fritsch Gmbh) mill. The obtained composites were characterized by a heterogeneous surface coverage of silica gel or titanium oxides. Zinc ions adsorption studies on these adsorbents showed practically complete removal of Zn (II) from aqueous solutions with an initial concentration of < 0.0001 mol/dm3 and a pH > 4 within 10 min.

Zinc ion adsorption by soils of the Republic of Udmurtia

Zinc ion adsorption by soils of the Republic of Udmurtia

Adsorption of zinc and copper (II) ions from aqueous solution using modified nano bentonite: equilibrium, kinetics, and thermodynamic studies

ABSTRACT In this research, modified Nanobentonite was prepared by calcination of bentonite for adsorption of zinc and copper ions. Nanobentonite particles were characterized by the EDX method, FTIR, and SEM. Adsorption efficiency, thermodynamic properties, and initial concentrations were studied. FTIR result showed sodium chloride affects the bentonite structure. According to the results, the rate of Zn2+adsorption at the chemical adsorption step is higher than the rate of adsorption of Cu2+. The amount of enthalpy and entropy are uniformly reduced when the Cu2+ and Zn2+ ions are adsorbed. The adsorption of Cu2+ ions is two-step and was occurring through an alternating ion-exchange mechanism.

Adsorption of Zinc(II) and Chromium(III) Ions by Modified Zeolites

The results of a study of the adsorption of zinc(II) and chromium(III) ions by zeolites modified by HCl are presented. According to the data of elemental analysis and electron spectroscopy, the zeolites contain at least 75% heulandite in their composition. The removal of aluminum ions from the tetrahedral framework of the sorbent formed by AlO4 and SiO4 occurs upon modifying the zeolites by HCl. This leads to the destruction of the main component, heulandite, and compaction of the silicate layer. The time of establishment of adsorption equilibrium in the zeolite–aqueous solution system is 90 min. The isotherms of adsorption of zinc(II) ions are obtained in a temperature range 298–318 K at pH 5.6–5.8. It is shown that the adsorption of zinc(II) ions increases with growing temperature. The isotherms of adsorption of chromium(III) ions are obtained in a temperature range 298–318 K at pH 7.6–7.9. It is found that the adsorption of chromium(III) ions decreases with increasing temperature. The differential heats of adsorption are calculated based on the isosteres of adsorption. The increase in the adsorption of chromium(III) ions is accompanied by a decrease in the differential heat of adsorption from 36.9 to 26.8 kJ/mol. This may be associated with the nonuniformity of the surface of the adsorbent, due to what the metal ions are adsorbed on less active regions of the surface as far as the growth in the saturation of more active sites. The change in the differential heat of adsorption of zinc(II) ions with the growth in the degree of filling of the surface has a nonmonotone character. In the region of low degrees of filling of the surface, the differential heat of adsorption decreases, and then increases, which is probably determined by polymolecular adsorption presuming the presence of an adsorbate–adsorbate interaction. The efficiency of treatment of industrial wastewaters of the electroplating industry in the case of the use of the modified zeolites is over 97%.

Dual role of silatranized Schiff base as a fluorimetric probe and a linker to functionalize graphene oxide for the selective detection and adsorption of zinc ions

Herein, a Schiff base probe possessing flexible ONNO architecture has been designed and explored for the analysis of metallic species. Simple protocols are illustrated for the syntheses of Schiff base probe (P), a silatranyl incorporated Schiff base probe (P-Silt) and graphene oxide functionalized with Schiff base probe (P@SiO2@GO) for the recognition and adsorption of zinc ions. The Schiff base probe P was derived from the condensation reaction of N-(2-hydroxyethyl)ethylenediamine and 2-hydroxy-4-methoxybenzophenone. It was then derivatized to its silatranyl counterpart (P-Silt) to incorporate a hydrolyzable cage for linking probe P on the surface of graphene oxide. The silatranyl derivative P-Silt displayed a selective spectrofluorimetric signal for zinc ions due to chelation-enhanced fluorescence effect (at 453 nm) which enabled the detection of zinc ions upto 7.09 nM (LOD). In addition, P linked graphene oxide P@SiO2@GO was utilized for the selective removal of zinc ions and proved as a highly efficient adsorbent (Qm = 88.34 mg g−1) even in the presence of co-existing ions. It can be re-used as a sorbent for SPE cartridges up to four cycles with 100% efficiency.

Optimal conditions for adsorption of zinc from industrial wastewater using groundnut husk ash.

Zinc is a toxic metal ion and is of importance in water and wastewater because it causes dizziness as well as lethargy when ingested by man. In the current study, the groundnut husk ash was investigated as a potential adsorbent for adsorption of zinc(II) ions from industrial wastewater. Groundnut husk ash was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and proximate analysis to identify the presence of the functional groups, surface morphology and the carbon content in the adsorbent respectively. To optimize the process parameters affecting the percentage removal of zinc(II) onto groundnut husk ash, the central composite design was used. The result of the optimization study showed an optimal percentage removal of 80.00%, with the optimal conditions of 1400μm, 100min, 25°C, 40mg/l and 20mg for particle size, contact time, temperature, initial zinc concentration and adsorbent dosage respectively. The equilibrium data showed a better fit for Langmuir isotherm, when compared to Freundlich, Temkin and Dubinin-Radushkevich isotherms, with R2 of 0.965. The adsorption kinetics was best described by pseudo-second-order kinetics with R2 of 0.987. The thermodynamic study, on the other hand, showed a negative value of enthalpy change(∆H = - 27.021), indicating an exothermic as well as a spontaneous reaction, with the degree of spontaneity of the reaction ranging from - 55.487 ≤ ∆G ≤ - 56.427, which showed a corresponding increase in Gibb's free energy (∆G) with an increase in temperature.

Regression models of zinc ion adsorption from aqueous solutions on zeolite from Kholinski deposit, modified with with a sulphur-containing polymer

This article presents regression analysis results of experimental data obtained from a study of the sorption of zinc ions from standardised aqueous solutions using zeolite (clinoptilolite type, Kholinski deposit) modified with a sulphur-containing polymer. Differences in the IR spectra of the modified zeolite were registered before and after sorption of Zn 2+ from an aqueous solution. The effect of the following technological parameters on the adsorption capacity of the modified zeolite was studied: pH, initial concentration of Zn ions in solution, temperature and sorption time of the studied zinc ion extraction. It was shown that the adsorption activity of the modified zeolite of the Kholinsky deposit cannot be approximated by the classical Freundlich and Langmuir equations, since the Zn (II) ion sorption mechanism is complexly coordinated. It was found that the Freundlich equation describes only 40% of the experimental data on the adsorption of zinc ions by a modified zeolite, while the Langmuir equation describes 71%. Accordingly, regression analysis was used to process the measurement results. The found nonlinear regression models reliably describe the observed patterns of sorption and desorption. Kinetic curves of the solution at different temperature conditions are described by exponential models. Adsorption activity toward zinc ions of activated carbon-, as well as natural- and modified-zeolite sorbents was studied. The comparison revealed significant advantages on the part of the modified zeolite: modification of the zeolite surface with a sulphur-containing polymer made it possible to increase its sorption ability by 4.5 times compared to natural zeolite and 9 times compared to activated carbon.

Efficiency of zinc ions (II) adsorption using activated carbon from palm kernel shell

The adsorption of wastewater from various industrial sources is important and one of the dangerous challenges the environment. This study focuses on the investigation of the efficiency of zinc ions adsorption by using activated carbon in synthetic wastewater. Activated carbon was prepared from palm kernel shells that were obtained from Songkhla province, Thailand. Activated carbon was prepared from palm kernel shells containing sodium chloride as a catalyst at the ratio 1:0, 1:1 and 1:2 (w/w), respectively. Activated carbon was calcined at 700 °C for 2 h. Next, it was washed with hot distillate water until pH = 7. After that, it was dried at 105 °C for 24 h. Iodine number was analyzed by using CHNS/O analyzer. The concentration of solution was examined by using atomic absorption spectrophotometer (AAS). The prepared activated carbon was characterized by thermogravimetric analysis (TGA), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), X-ray fluorescence spectrophotometer (XRF), X-ray diffractometry (XRD) and Fourier-transform infrared spectroscopy (FTIR). For the pure activated carbon, it was noteworthy that the major components were O (37.25%), N (30.95%) and C (26.54%), whilst a minor content was H (2.23%), C (1.73%) and Si (0.76%). This result was strongly consistent with the XRF analysis. The ratio of activated carbon to sodium chloride 1:2 (w/w) exhibited the highest iodine number (180.95±10.82 mg/g). The factors of adsorption including initial concentration (20-150 ppm) and adsorption time (2-10 h.) The result showed that the optimum conditions of adsorption containing concentration were 65 ppm and adsorption time was 10 h. The efficiency of adsorption was 69.73 %.

Synthesis of ZIF-8/Fly Ash Composite for Adsorption of Cu2+, Zn2+ and Ni2+ from Aqueous Solutions.

In this study, fly ash (FA) coated with ZIF-8 (ZIF-8/FA) nanocomposite was first synthesized by taking 2-methylimidazole and zinc nitrate hexahydrate as reactants and then used as an adsorbent for adsorption of copper, zinc, and nickel ions from aqueous solution. The characteristic of FA and ZIF-8/FA samples were analyzed based on the data from scanning electronic microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, grain size analyzer and N2 adsorption-desorption isotherm. The results showed that ZIF-8 deposited on the FA evenly. The average crystallite size of ZIF-8 on the surface of FA is 15.85 nm. The specific surface area of FA was increased from 1.8 to 249.5 m2/g. The adsorption efficiency of the ZIF-8/FA nanocomposite for the removal of heavy metal ions from aqueous solution was optimized in terms of different parameters such as pH, adsorbent dosage, and contact time. It was shown that the saturated adsorption amounts of the obtained composite for adsorption of Cu2+, Zn2+, and Ni2+ are 335, 197, and 93 mg·g−1. ZIF-8/FA had better stability and more mesoporous volume than that of ZIF-8 and exhibited higher rate for adsorption of heavy metal ions from aqueous solution than FA and ZIF-8, suggesting an adsorption synergy between ZIF-8 and FA. The adsorption mechanism of heavy metal ions by ZIF-8/FA includes surface adsorption, pore adsorption, and ion exchange. The obtained ZIF-8/FA nanocomposite can solve the encountered problems of FA for low adsorption and the difficult recycling of ZIF-8 for their small size, high cost, and poor stability.

Heavy Metal Removal from Industrial Wastewater and Runoff Discharge Using Modified Diatomite as Filtration Medium

The adsorption of copper and zinc ions onto the modified diatomite with sodium hydroxide and manganese oxide (Mn-DM) was studied in isotherm batch solutions. The analysis of Cu (II) and Zn (II) results showed the effect of contact time and adsorbent dosage on the adsorption process performed in solutions with individual and combined metal ions, allowing observations of the selectivity and preference of modified diatomite in capturing Cu (II) and Zn (II). The paper also analysed the effect of supplementing peat on the adsorption process, at various ratios to the modified diatomite, to obtain the optimised filter composition with highest adsorption efficiency. The obtained data was used to model the kinetics of the adsorption processes for both metal ions.

Investigating the zinc ion adsorption capacity of a chitosan/β-cyclodextrin complex in wastewater

To decrease the amount of Zn2+ in industrial waste water, in this study, β-cyclodextrin (β-CD) was first modified and then used to obtain a β-cyclodextrin polymer (β-CDP). The effects of reaction temperature and reaction time of β-CD with citric acid (CA), polyethylene glycol 400 (PEG-400), and disodium hydrogen phosphate (NaH2PO4) on the amount of β-CDP produced were investigated. The results showed that at a reaction temperature of 145 °C and a reaction time of 4.5 h, 6.58 g of β-CDP was produced. Then, chitosan (CTS) was crosslinked with β-CDP using glutaraldehyde to prepare a chitosan/β-cyclodextrin (CTS/β-CDP) complex. The mass ratio of CTS to β-CDP, reaction temperature, reaction time, and amount of added glutaraldehyde were used as the main variables to examine the Zn2+ adsorption rate and adsorption capacity of the composites prepared in this study. The optimum experimental conditions were as follows: a mass ratio of 3:10, a reaction temperature of 80 °C, a reaction time of 90 min, and 2 mL of glutaraldehyde. Under these optimal conditions, the adsorption amount and adsorption rates of Zn2+ using CTS/β-CDP complex were respectively 97.70 mg·g-1 and 78.92%.

The role of copper during the growth of stoichiometric Cu2ZnSnS4 by successive ionic layer adsorption and reaction method

The synthesis and characterization of Cu2ZnSnS4 (CZTS) thin films prepared on glass/CdS substrates by the successive ionic layer adsorption and reaction (SILAR) method are presented. The effect of copper concentration and atmosphere annealing on the properties of CZTS thin films were studied by means X-ray diffraction (XRD), Raman spectroscopy, Scanning Electron Microscopy (SEM), X-ray photoelectron spectroscopy (XPS), optical spectroscopy and current-voltage curves. The XPS depth profiling data revealed that a minima copper concentration in cationic solution is required to start the adsorption of zinc and tin ions at the CdS surface. The use of 0.001–0.002 M copper concentration allows the adsorption of zinc and tin ions in a suitable quantity inducing the formation of stoichiometric and polycrystalline CZTS thin films. Furthermore, it was found that above of this copper concentration, the segregation of Cu2S phase occurs, even when it is ten times smaller than Zn and Sn concentrations. Otherwise, the sulfurization process doesn't imply a significant change on the structural and chemical properties, as if it does in the optical and electrical properties. This suggests that the excess of Na2S used in the anionic solution is enough to compensate the loss of sulfur during the thermal annealing. The optical band gap energy and the electrical conductivity of these films were evaluated in the range of 1.41–1.53 eV and 10−1 Ω cm−1, respectively. All results suggested that this material is suitable for being applied as an absorber layer in photovoltaic solar cells.

Исследование адсорбции ионов цинка кислотомодифицированными опилками акации ушковидной (Acacia auriculiformis)

Исследована адсорбция ионов Zn2+ нативными и модифицированными в слабоконцентрированных (1-3 %) растворах H2SO4 опилками акации ушковидной (Acacia auriculiformis). Изотерма адсорбции ионов цинка нативными опилками акации относятся к изотермам I типа, согласно классификации ИЮПАК и L типу, согласно классификации Гильса. Максимальная сорбционная емкость опилок акации по ионам цинка составляет 7.5 мг/г. С целью увеличения сорбционных показателей, исследуемые опилки обрабатывались слабоконцентрированными растворами серной кислоты при 20оС в течение 5 ч. С увеличением концентрации раствора серной кислоты сорбционная емкость опилок поионам цинка увеличивается. Обработка опилок 3%-ным раствором H2SO4 способствует увеличению максимальной сорбционной емкости по ионам Zn2+ c 7.5 до 36.5 мг/г. Полученные изотермы адсорбции обрабатывалась с помощью моделей Ленгмюра, Фрейндлиха, Дубинина-Радушкевича и Темкина. Определены уравнения регрессии и коэффициенты аппроксимации, а также термодинамические параметры процессов (энергия сорбции и энергия Гиббса). Изотерма адсорбции нативными опилками наиболее адекватно описывается моделью Темкина, модифицированными – моделью Фрейндлиха. Значения энергии адсорбции менее 8 кДж/моль и энергии Гиббса в пределах от -4 до 0 кДж/моль сви-детельствуют о протекании самопроизвольной физической адсорбции. Получены кинетические зависимости процессов адсорбции ионов цинка нативными и модифицированными опилками акации. Обработкой кинетических зависимостей в рамках диффузионной модели Бойда рассчитаны коэффициенты Био для исследуемых процессов, значения которых соответствуют протеканию процессов смешанной диффузии, то есть лимитирующими стадиями процессов адсорбции являются, как внешняя, так и внутренняя диффузия.