Involving Ion Exchange Research Articles

Adsorption Behavior and Mechanism of Methylene Blue, Crystal Violet, Eriochrome Black T, and Methyl Orange Dyes onto Biochar-Derived Date Palm Fronds Waste Produced at Different Pyrolysis Conditions

This study investigated the impact of pyrolysis conditions on physical characteristics of date palm fronds biochars and their performances for aqueous uptake of anionic dyes—methyl orange (MO) and Eriochrome Black-T (EBT)—and cationic dyes—methylene blue (MB) and crystal violet (CV). Detailed characterization of the biochars revealed the formation of oxygen functionalities (C=O, C-O-C, and C-O), improved surface characteristics (surface area and pore volume) and high ash content at higher pyrolysis temperature and time. Biochar-derived date palm with a high surface area of 431.82 m2/g and a pore volume of 0.134 cm3/g was obtained at pyrolysis temperature and time 700 °C and 4 h, respectively. For all the four investigated dyes, the adsorption isotherm was mainly described by Redlich–Peterson isotherm model (R2 > 0.95), while the adsorption kinetics well-fitted the pseudo-second order model. The biochar yielded fast dyes adsorption with maximum adsorption capacity for MB, EBT, MO, and CV dye of up to 206.61, 309.59, 163.132, and 934.57 mg/g at 200 mg/L dye concentration, respectively. The adsorption of cationic dyes was pH-independent indicating the involvement of pi–pi and chemical interactions. However, the uptake of the anionic dye was favorable at acidic conditions and was dominated by electrostatic interactions involving ion exchange and chemical reactions. The produced biochars exhibited excellent surface characteristics and enhanced adsorptive performance relative to other similar adsorbents. Thus, the direct pyrolysis of date palm fronds’ waste is a sustainable and economical approach of converting a huge quantity of wastes into excellent adsorbent for effective remediation of dye-contaminated water and wastewater.

Efficient extraction of slowly-released Cr(vi) from nano-sized ion channels in Cr(vi)–ettringite from reduced chromite ore processing residue

Complete extraction of Cr(vi) from rCOPR which involved ion exchange in ion channels of Cr(vi)–ettringite, formation and growth of nano-CaCO3.

Recovery of gold through adsorption onto sericin and alginate particles chemically crosslinked by proanthocyanidins

The recovery of gold from wastewater has been encouraged in the last years due to this metal high cost, elevated demand, and low availability. Sericin and alginate particles chemically crosslinked by proanthocyanidins (SAPAS) were successfully used in this study for this purpose. The maximum adsorption capacity predicted by the Dubinin-Radushkevich model was 237.60 mg/g at 303 K. The thermodynamic parameters revealed that the process is spontaneous, endothermic and also governed by entropic changes. The characterization of SAPAS before and after gold adsorption (SAPAS-Gold) suggested that the uptake of this metal involves ion exchange and subsequent reduction. The thermogravimetric analysis showed that elemental gold may be recovered from SAPAS surface by the incineration process. Alternatively, both the reuse of SAPAS and the efficient recovery of gold (84.389 ± 2.103%) is possible by employing the desorption process with thiourea (0.5M)/hydrochloric acid (2M) solution.

2D Resistive Switching Based on Amorphous Zinc–Tin Oxide Schottky Diodes

AbstractA room‐temperature‐processed resistive switching Schottky diode that can be operated in two distinct modes, depending solely on the choice of device initialization mode, is presented. Electroforming in the diode's reverse polarity leads to an abrupt filamentary switching with inherently long data retention at the expense of rectification. After this electroforming process, the devices may work in either a bipolar or unipolar manner with a resistance window of at least two orders of magnitude. Device initialization in the forward direction shows a smooth area‐dependent switching over two orders of magnitude, which conserves the current rectification and allows for analog control over the resistance states (dependence of device history and applied voltage stimuli). This secondary mechanism involves ion exchange or charge trapping at the Schottky interface without a contribution from the bulk (hence, it is termed 2D), which is reported for the first time for an amorphous oxide semiconductor switching matrix.

Efficient removal of uranium (VI) by 3D hierarchical Mg/Fe-LDH supported nanoscale hydroxyapatite: A synthetic experimental and mechanism studies

Abstract 3D hierarchical Mg/Fe-LDH supported nanoscale hydroxyapatite materials (Mg/Fe-LDHs@nHAP) were facilely synthesized by the ultrasound-assisted synthesis method. Various techniques for characterization, such as X-ray diffraction (XRD), Fourier transformed infrared (FT-IR), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) surface area measurements, disclosed that Mg/Fe-LDHs@nHAP composites had hierarchical layered structure with large BET surface area (231.4 m2/g) as well as plentiful phosphate-containing and hydroxyl-containing groups. The results of batch adsorption experiments showed that U(VI) removal by Mg/Fe-LDHs@nHAP composites was less influenced by other coexisting ions, suggesting the high selectivity of U(VI) by Mg/Fe-LDHs@nHAP composites. The pseudo-second-order models and intra-particle diffusion model can well represent the removal kinetics of U(VI) on Mg/Fe-LDHs@nHAP, and the maximum U(VI) capture capacity of Mg/Fe-LDHs@nHAP reached 845.16 mg/g calculated by Langmuir model at pH = 6.0 and 298 K. The regeneration experiment demonstrated that Mg/Fe-LDHs@nHAP composites held good stability and reusability for extraction of U(VI). The removal mechanisms of U(VI) on Mg/Fe-LDHs@nHAP involved ion exchange, surface complexation and dissolution-precipitation by XPS, EDX and FT-IR spectra investigation. According to the XRD analysis, the absorbed U(VI) was finally formed into a chernikovite precipitate with a flower-like shape induced by phosphate-containing groups. The work indicated that the as-synthesized Mg/Fe-LDHs@nHAP composites are effective adsorbents for the removal of U(IV) in wastewater.

Selective adsorption of Cs+ by MXene (Ti3C2Tx) from model low-level radioactive wastewater

This study explored whether MXene (Ti3C2Tx) could remove radioactive Cs+ from model nuclear wastewater. Various adsorption tests were performed and the physical aspects of the interaction were investigated. We varied the MXene dosage, Cs+ initial concentration, solution pH, solution temperature and exposure time. MXene adsorption exhibited very fast kinetics, based on the fact that equilibrium was achieved within 1 h. MXene exhibited an outstanding adsorption capacity (148 mg g−1) at adsorbent and adsorbate concentrations of 5 and 2 mg L−1, respectively, at neutral pH condition (i.e., pH 7). We explored Cs+ adsorption by MXene in the presence of four different ions (NaCl, KCl, CaCl2 and MgCl2) and three different organic acids (sodium oleate, oxalic acid, and citric acid). The Cs+ removal rate changed in the presence of these components; adsorption of Cs+ by MXene thus involved ion exchange, supported by both Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. We confirmed that MXene was re-usable for at least four cycles. MXene is cost-effective and practical when used to adsorb radionuclides (e.g., Cs+) in nuclear wastewater.

Good hydrolysis activity on raffinose family oligosaccharides by a novel α-galactosidase from Tremella aurantialba

An α-galactosidase designated as TAG was purified from the dried fruit bodies of Tremella aurantialba with 182.5-fold purification. The purification procedure involved ion exchange chromatography on Q-sepharose, DEAE-Cellulose, and Mono Q and gel filtration by FPLC on Superdex 75. The purified α-galactosidase was a monomeric protein with a molecular mass of 88 kDa. The optimal pH of TAG was 5.0 and more than 60% of the original enzyme activity remained at pH 2.0 and 3.0. Its optimal temperature was 54 °C with good thermo-stability, 30.8% of the original activity was retained after exposure to a temperature of 70 °C for 1 h. The metal ions Hg2+, Cu2+, Fe3+ and Mg2+ strongly inhibited the enzyme activity. The enzyme activity was found to be inhibited by N-bromosuccinimide indicating that tryptophan was essential to the catalytic activity of α-galactosidase. The enzyme completely hydrolysed stachyose and partially hydrolysed raffinose to galactose at 50 °C within 6 h as detected by thin layer chromatography and the dinitrosalicylic acid method and the content of reducing sugar reached 4.36 mg/mL.

Synthesis and phosphate adsorption behaviour of Mg/Al-pillared montmorillonite loaded with La(OH)3

ABSTRACT Magnesium/aluminum-pillared montmorillonite loaded with lanthanum hydroxide (Mg/Al-MMT-La(OH)3) was synthesized using non-toxic raw materials by ion-exchange and co-precipitation for phosphate removal from wastewater. Some adsorbents were fabricated in different molar ratios of Mg to Al, analyzed using various characterizations, and investigated in batch adsorption experiments. The determined adsorption kinetics of the 1:4 Mg/Al-MMT-La(OH)3 composite fitted well with the Elovich model. In addition, the Langmuir model revealed the high adsorption efficiency of phosphate by the adsorbent with a maximum adsorption capacity of 79.33 mg/g. The negative value of ΔG° and positive value of ΔH° (64.25 kJ/mol) demonstrated that phosphate adsorption onto 1:4 Mg/Al-MMT-La(OH)3 was spontaneous and endothermic in nature. Moreover, when the molar ratio of to was 1:5, the phosphate adsorption capacity reduced by 53.5%, far exceeding the effect of , , Cl−, and . The addition of Al3+ caused a sharp decline in phosphate removal property by 81.9% when /Al3+ molar ratio was 1:5, however, the presence of other cations showed the negligible impact on it. The adsorption mechanism primarily involved ion exchange with intercalated anions and surface coordination with loaded hydroxides. Results proved that 1:4 Mg/Al-MMT-La(OH)3 material has a favourable application potential in the surface water remediation.

Spiramycin adsorption behavior on activated bentonite, activated carbon and natural phosphate in aqueous solution.

Efficacy of activated bentonite, activated carbon, and natural phosphate under experimental conditions was tested as low-cost adsorbents for spiramycin antibiotic removal from aqueous solution. Equilibrium kinetic and isotherm adsorption process are well described by pseudo-second order and Langmuir isotherm models for activated bentonite and activated carbon, while natural phosphate follows pseudo-first order and Freundlich models, respectively. Obtained results revealed that activated bentonite has the highest adsorption capacity (260.3mg/g) as compared to activated carbon (80.3mg/g) and natural phosphate (1.7mg/g). The adsorption capacity decreases for all adsorbents in the presence of NaCl. The adsorption processes are facilitated in the alkaline pH range for activated bentonite and activated carbon, whereas, for natural phosphate, the acidic pH range is favorable. They are involving ion exchange and hydrogen bond mechanisms as well as Van der Waals forces and also π interactions for activated carbon. Thermodynamic calculation shows that spiramycin adsorption is endothermic and spontaneous on all adsorbents. The activated bentonite reusability is more efficient by more than 95% in two-step desorption using NaOH and HCl eluents compared to activated carbon. Thus, activated bentonite is a promising adsorbent for spiramycin removal from aqueous solution.

K2xMnxSn3−xS6 (x = 0.5–0.95) (KMS-1) immobilized on the reduced graphene oxide as KMS-1/r-GO aerogel to effectively remove Cs+ and Sr2+ from aqueous solution

Novel composite of immobilized layered K2xMnxSn3−xS6 (x = 0.5–0.95) (KMS-1) on the surface of reduced graphene oxide (r-GO), KMS-1/r-GO (KGO), has been fabricated by employing hydrothermal technique and used for the removal of radioactive Cs+ and Sr2+ ions from aqueous solutions. The KGO was characterized thoroughly with different characteristic techniques and found that the laminar KMS-1 nanoplate were immobilized on the surface of r-GO nanosheets, forming a highly porous stacked structure. Batch studies have been done for obtaining optimal experimental parameters and investigating the effect of adsorption time, initial concentration of pollutant, pH of solution, temperature, and competing anions on the removal properties. At room temperature, the maximum adsorption capacity of KGO was 338.18 mg·g−1 and 220.12 mg·g−1 for both Cs+ and Sr2+, respectively. Langmuir isotherm and pseudo-second-order kinetic models were fitted well with experimental data of removed Cs+ and Sr2+. Adsorption showed good selectivity of composite towards Cs+ and Sr2+ in the presence of co-existing ions (Ca2+ and Mg2+). The proposed adsorption mechanism involved ion exchange through the presence of K+ ions in KMS-1 and formation of surface ionic interactions between r-GO and ions through COOX or SX (X denoted Cs+ and Sr2+). This study highlighted the facile applicability of novel material KGO and could be used as a new adsorbent for the removal of radioactive ions.

Addition of iron materials for improving the removal efficiencies of multiple contaminants from wastewater with a low C/N ratio in constructed wetlands at low temperatures.

Constructed wetlands (CWs) are widely used in wastewater treatment. Wastewater generally contains multiple contaminants. In this study, CWs were applied to treat wastewater with a low COD/TN ratio and containing heavy metals. Iron-based material was added in CWs to enhance the treatment efficiency. The contaminant removal efficiency was positively correlated with the dosage of iron-based material. Considering the operation cost, we added 1g of iron-based material in CW and realized the multi-contaminant removal efficiency after 4-day treatment at low temperature: 99.51% of Cu(II), 87.22% of Cr(VI), 65.62% of TN, and 60.23% of COD. Microbial community analysis and kinetic analysis predicted that the removal mechanism involved ion exchange and microbial denitrification. Specific bacteria were found in CWs with iron-based material, such as Thiobacillus spp. and Thauera spp., indicating that the nitrate removal in the denitrification process was triggered by carbon sources and that Fe2+ worked as both the electron donor and the adjuster of the abundances of specific bacteria. The addition of iron-based material into CWs was a green option to improve the pollutant removal performance.

Effective decontamination of phosphate and ammonium utilizing novel muscovite/phillipsite composite; equilibrium investigation and realistic application

Novel muscovite/synthetic zeolitic phillipsite composite (Mu/Ph) was synthesized and inspected by different analytical techniques as a hybrid product of enhanced physicochemical properties and adsorption capacities for phosphate and ammonium. Mu/Ph adsorption systems for phosphate and ammonium were inspected considering the kinetic, equilibrium and thermodynamic studies as well as the controlling mechanisms. The kinetic behaviors of Mu/Ph for both phosphate and ammonium were remarkably described by Pseudo-second order model and the equilibration times were attained after 720 min and 480 min, respectively. The equilibrium curves for both ions were categorized as L-type isotherms which assigned mainly to systems of high affinity between the inspected adsorbents and the target dissolved ions. Additionally, the uptake results of both ions displayed slight preferences to be described by the Langmuir model. The thermodynamic studies revealed endothermic and exothermic nature for phosphate and ammonium, respectively. Moreover, the calculated parameters indicated physisorption of them by spontaneous reaction involved ion exchange processes controlled mainly by electrostatic interactions rather than ionic or covalent binding. The composite showed promising reusability properties to be applied in the reduction of phosphate and ammonium six times. The novel synthetic Mu/Ph exhibits higher capacities than numerous studied adsorbents and was applied in decontamination of phosphate and ammonium from real sewage water achieving exceptional results.

Effects of pH, carbonate, calcium ion and humic acid concentrations, temperature, and uranium concentration on the adsorption of uranium on the CTAB-modified montmorillonite

With the aim of gathering uranium from ground aquatic environment in which uranium mainly occurs in negative species, the montmorillonite (MT) intercalated with cetyltrimethylammonium bromide (CTAB) was fabricated. X-ray diffraction and Fourier transform infrared spectroscopy were utilized to prove the entrance of CTAB into MT. Adsorption of uranium onto CTAB-MT was studied with respect to effect of pH, carbonate, calcium, humic acid, contact time, initial uranium concentration, and temperature. The adsorption negatively depended on pH, carbonate and calcium ion and humic acid concentrations. CTAB-MT had a higher uranium adsorption ability. The maximum monolayer uranium adsorption amount of CTAB-MT calculated by well fitted Langmuir model was determined as 213.31 mg g−1, preceding 82.17 mg g−1 of MT. The adsorption kinetics was well fitted by pseudo-second-order model. The uptake mechanism involved ion exchange and electrostatic attraction. The adsorption was endothermic and spontaneous. The results demonstrated CTAB-MT was promising to separate uranium from ground water.

Modelling Low-Salinity Oil Recovery Mechanisms Using an Ion Dissociation Model

Experimental evidence shows that injecting low-salinity water during the oil recovery process can lead to an increase in the amount of oil recovered. Numerous mechanisms have been proposed to explain this effect, and, in recent years, two which have gained notable support are multicomponent ionic exchange (MIE) and pH increase. Both mechanisms involve ion exchange reactions within the thin film of water separating the oil in a reservoir from the clay minerals on the surface of the reservoir rock. Since the reactions occur on the molecular scale, an upscaled model is required in order to accurately determine the dominant mechanism using centimetre-scale experiments. In this paper, we develop the first stages of this upscaling process by modelling the pore-scale motion of an oil slug through a clay pore throat. We use a law-of-mass-action approach to model the exchange reactions occurring on the oil–water and clay–water interfaces in order to derive expressions for the surface charges as functions of the salinity. By balancing the disjoining pressure in the water film with the capillary pressure across the oil–water interface, we derive an expression for the salinity-dependent film thickness. We compare the two mechanisms by modifying an existing model for the velocity of an oil slug through a pore throat. Numerical results show that the velocity increases as the salinity decreases. The percentage increase is larger for the MIE mechanism, suggesting that MIE may be the dominant causal mechanism; however, this will vary depending on the particular clay and oil being studied.

Equilibrium, Kinetic, and Thermodynamic Studies of Anionic Dyes Adsorption on Corn Stalks Modified by Cetylpyridinium Bromide

Corn stalks (CS) were modified by a cationic surfactant, cetylpyridinium bromide (CPB), and used as an adsorbent (CS-CP) to remove anionic dyes [Acid Red (AR) and Acid Orange (AO)] from aqueous solutions. The FTIR analysis and the obtained calculations based on the determination of the adsorption capacity of CS towards CPB confirmed that the cationic surfactant had been adsorbed on the surface of corn stalks. Adsorption of the anionic dyes on modified corn stalks was investigated in a series of batch adsorption experiments at 303–328 K. The adsorption data were analyzed using Langmuir, Freundlich, and Temkin models. The Langmuir model was found to be more suitable for the experimental data of the anionic dyes on CS-CP than other adsorption models. Kinetic studies revealed that the pseudo-second order model showed the best fit to the experimental data. The thermodynamic parameters indicated that the adsorption process was spontaneous and exothermic. Mechanisms involving ion exchange and chemisorption might be responsible for the uptake of the anionic dyes on CS-CP. Obtained results imply that CS-CP could be applied as an effective adsorbent to remove anionic dyes from aqueous solutions.

Production and separation of 163Ho for nuclear physics experiments.

This paper describes the production and chemical separation of the 163Ho isotope that will be used in several nuclear physics experiments aiming at measuring the neutrino mass as well as the neutron cross section of the 163Ho isotope. For this purpose, several batches of enriched 162Er have been irradiated at the Institut Laue-Langevin high flux reactor to finally produce 6 mg or 100 MBq of the desired 163Ho isotope. A portion of the Er/Ho mixture is then subjected to a sophisticated chemical separation involving ion exchange chromatography to isolate the Ho product from the Er target material. Before irradiation, a thorough analysis of the impurity content was performed and its implication on the produced nuclide inventory will be discussed.

Effective, rapid and selective adsorption of radioactive Sr2+ from aqueous solution by a novel metal sulfide adsorbent

A novel metal sulfide (KZTS) adsorbent has been synthesized using a simple one-step hydrothermal method for radioactive Sr2+ removal from aqueous solutions. XRD and TG analyses indicated that KZTS was chemically and thermally stable. SEM-EDS and TEM images showed that KZTS possessed both flake-like and polyhedral structure with the formula of K1.67Zn0.67Sn2.17S6.00 and K5.84Zn3.47Sn5.04S16.99, respectively. The average formula was determined to be K1.87ZnSn1.68S5.30 using ICP-OES. The adsorption ability of KZTS for Sr2+ was evaluated in detail by batch experiments. The kinetics studies showed that Sr2+ was rapidly removed from the aqueous solution within the equilibrium time of 10 min. According to Langmuir isotherm, the maximum adsorption capacity of KZTS was 19.3 mg/g at 298 K and the high value of the Langmuir constant indicated the high affinity of KZTS for Sr2+. The adsorption mechanisms involved ion exchange and surface Sr–S bonding interactions, with the former dominating. High adsorption performance was observed over a broad pH range of 3–11, although it could be inhibited by co-existing ions, especially Ca2+ and Mg2+. The adsorbent showed a high distribution coefficient (Kd = 1.26 × 106 mL/g) and negligible adsorbate leaching at low Sr2+ concentrations, indicating the strong and irreversible adsorption of Sr2+ on KZTS. Further, KZTS exhibited high selectivity for Sr2+ in alkaline and tap water. These remarkable features suggest that KZTS is a highly desirable adsorbent to remove radioactive strontium from radioactive wastewater.

Phosphate uptake behavior and mechanism analysis of facilely synthesized nanocrystalline Zn‐Fe layered double hydroxide with chloride intercalation

Zn‐Fe layered double hydroxide with chloride intercalation (ZFCL) was synthesized by a coprecipitation method at room temperature. ZFCL was characterized by N2 adsorption‐desorption isotherms, X‐ray diffraction, scanning electron microscope, Zeta‐sizer analyzer, X‐ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The results showed that ZFCL had large surface area and layered structure. The maximum adsorption capacity of ZFCL was 150.6 mg/g at 25°C. That was higher than most other adsorbent which were reported. The kinetic data were described better by the pseudo‐second‐order adsorption kinetic rate model. The adsorption isotherm on the adsorbent was described by Langmuir, Freundlich, and Sips models at pH 6 and followed the fitting order: Sips >Freundlich>Langmuir. Thermodynamic analyses indicated that the phosphate adsorption on ZFCL was endothermic and spontaneous in nature. The sequence of coexisting cations and anions competing with phosphate was Ca2+ > Mg2+ > Na+ and SO42− > NO3− > Cl−. ZFCL can be regenerated by the sequential use of NaOH and ZnCl2. The adsorption capacity remained high as 108.6 mg/g after regeneration of 3 times. The results of zeta potential, Fourier transform infrared spectroscopy, and X‐ray photoelectron spectroscopy analyses indicated that the phosphate adsorption mechanisms involved ion exchange, Zn3(PO4)2 precipitation, and the formation of inner‐sphere complex via replacement of surface hydroxyl groups by phosphate.

Nanoscale spatial analysis of clay minerals containing cesium by synchrotron radiation photoemission electron microscopy

A synchrotron radiation photoemission electron microscope (SR-PEEM) was applied to demonstrate the pinpoint analysis of micrometer-sized weathered biotite clay particles with artificially adsorbed cesium (Cs) atoms. Despite the insulating properties of the clay, we observed the spatial distributions of constituent elements (Si, Al, Cs, Mg, and Fe) without charging issues and clarified reciprocal site-correlations among these elements with nanometer resolution. We found that Cs atoms were likely to be adsorbed evenly over the entire particle; however, we identified an occupational conflict between Cs and Mg atoms, implying that Cs sorption involves ion exchange processes. Spatially resolved X-ray absorption spectra (XAS) of the Cs4,5 M-edge region showed Cs to be present in a monocation state (Cs+) as typically observed for Cs compounds. Further pinpoint XAS measurements were also performed at the Fe L2,3-edge to determine the chemical valence of the Fe atoms. The shapes of the spectra were similar to those for Fe2O3, indicating that Fe in the clay was in a 3+ oxidation state. From these observations, we infer that charge compensation facilitates Cs adsorption in the vicinity of a substitution site where Si4+ ions are replaced by Fe3+ ions in SiO4 tetrahedral sheets. Our results demonstrate the utility of SR-PEEM as a tool for spatially resolved chemical analyses of various environmental substances, which is not limited by the poor conductivity of samples.

Sorption of uranium(VI) by La-Al-carboxymethyl konjac glucomannan microsphere sorbent

The microsphere of carboxymethyl konjac glucomannan immobilizing La3+ and Al3+ (CMKGM-La-Al) has been explored for sorption of U(VI). The maximum U(VI) sorption capacity of the microsphere is found to be 45.4 mg g−1 at pH 5. Experimental data are fitted well with the linear Langmuir and linear pseudo-first-order kinetic model. The sorption process is endothermic, spontaneous and favorable. The possible mechanism of CMKGM modification and sorption of U(VI) on CMKGM-La-Al involves ion exchange and coordination reaction. The comparison between CMKGM-La-Al and other sorbents suggests that CMKGM-La-Al can be considered as an effective sorbent for U(VI) sorption.