Utilization of carbon-coated ZrO2/Mn-Mg-Zn ferrites nanostructures for the adsorption of Cs (I) and Sr (II) from the binary system: kinetic and equilibrium studies

Carbon-coated ZrO2/Mn-Mg-Zn ferrites nanostructures (CZ-FN) have been prepared as a new inorganic sorbent to remove Cs (I) and Sr (II) from a waste stream. Adsorption of Cs (I) and Sr (II) has been implemented considering different noteworthy parameters, for example, shaking time and the optimum time achieved high adsorption capacity of both ions [103 and 41 mg/g for Sr (II) and Cs (I)] was found 30 min. Also, the impact of pH values was studied; the best pH value for the adsorption process is pH 6. The adsorption saturation capacity of CZ-FN is 420.22 and 250.45 mg/g for strontium and cesium, respectively. The solubility percentage of CZ-FN was calculated utilizing diverse molarities from HNO3, HCl, and NaOH as eluents, the obtained data reveals an increase in the solubility percentage with more increase in the molarity of the eluents. The elevation in the solubility percentage follows the following order; HNO3 < HCl < NaOH. The kinetic studies were applied using the nanolinear form of different kinetic models; it was found that the adsorption process obeys the nonlinear pseudo-second-order. According to equilibrium studies, the Langmuir model has been more accurate than the Freundlich model for adsorption in the case of binary systems. The values of Di for the strontium and cesium are 10-10 m2/s, which displays the chemisorption nature of this process. The greatest values of the desorption process for the strontium and cesium are 96.87% and 94.43 by 0.3 M of HNO3. This indicated that the carbon-coated ZrO2/Mn-Mg-Zn ferrites could be regenerated and recycled to remove strontium and cesium ions from waste streams.

Efficient adsorptive removal of Co2+ from aqueous solution using graphene oxide

This study aimed to utilize synthesized graphene oxide (GO) for adsorptive removal of cobalt ions and investigate the adsorption mechanism using advanced techniques such as X-ray absorption spectra (XAFS). The GO was synthesized via an improved Hummers method, resulting in high surface area (93.7 m2/g) and abundant oxygen-containing functional groups. Various characterizations, including SEM, TEM, Raman, FT-IR, TG, potentiometric titrations, and N2 sorption-desorption measurements, were employed to characterize the GO. The adsorption behavior of GO towards Co2+ was investigated, and the results showed that the adsorption process followed a pseudo-second-order kinetic model and the Langmuir model, with a maximum sorption capacity of 93.7 mg/g. The adsorption process was chemisorption and endothermic, with GO showing adsorption selectivity order of Co2+ > Sr2+ > Cs+. Based on various characterizations such as X-ray absorption near-edge spectroscopy (XANES), extended X-ray absorption fine structure (EXAFS), FT-IR, and XPS, the sorption mechanism of Co2+ onto GO was discussed, with the results indicating that coordination and electrostatic interaction were the primary adsorption mechanisms, with oxygen-containing functional groups playing a vital role. The first coordinating atom for Co2+ was O, and the coordination environment was similar to that of cobalt acetate and CoO. Overall, this study provides comprehensive understanding of the adsorption behavior and mechanism of Co2+ onto GO, highlighting its potential as an effective adsorbent for removing nuclides from aqueous solution.

Removal and isolation of radioactive cobalt using DNA aptamers

Electricity generation using nuclear power has various advantages, such as carbon reduction, but the treatment of nuclear waste is emerging as a big issue in many countries. The development of technology that can selectively remove radionuclides from liquid radioactive waste is one of the ways to reduce nuclear waste. Here, we assessed a new way of removing radioactive cobalt from a liquid using an aptamer. Aptamers specifically binding cobalt ions were selected through systematic evolution of ligands by exponential enrichment (SELEX). Their binding strength and stability of their complexes with cobalt were analyzed through surface plasmon resonance assay and 2D program Mfold, respectively. The optimal aptamer/bead conjugate conditions for binding cobalt were established using an FA-C1 aptamer with the strongest binding to cobalt. Under these conditions, more than 80% of radioactive cobalt was removed, and more than 99.95% of removed cobalt was recovered. These results proved that radioactive cobalt removal using this aptamer can effectively reduce liquid radioactive waste. This means that the aptamer/bead complex can be utilized to remove various radioactive metal ions.

Extraction and separation feasibility of cerium (III) and lanthanum (III) from aqueous solution using modified graphite adsorbent

Graphite (GR) and graphite/alginate (GRA) composite were synthesized utilizing the thermal annealing technique and used as a new adsorbent material for the selective separation and removal of La(III) and Ce(III) from aqueous solutions. Fourier transform infrared (FTIR) spectroscopy, thermal analysis (DTA, TGA), X-ray diffraction (XRD), surface area, porosity, and scanning electron microscope (SEM) were also used to characterize the generated material. Distinct experiments were performed to test the ability of the GRA to La(III) and Ce(III) removal, which include the effect of pH, shaken time, initial concentration of La(III), and Ce(III) at different temperatures range. After 20 min, both ions have reached equilibrium. The pseudo second-order kinetic model was chosen as one which best fits the experimental evidence and better reflects the chemical sorption process. Adsorption isotherm was studied using the Langmuir, Freundlich, and D-R models. The Langmuir model was used to better fit the results obtained. At 25 °C, Ce(III) and La(III) have maximum monolayer capacities of 200 and 83.3 mg/g, respectively. The sorption was endothermic reaction and spontaneous, as illustrated by the data of thermodynamics studies. GRA has the ability to be used as a novel lanthanide adsorbent material, especially for selective separation between Ce(III) and La(III).

Isotope signature and elemental characteristics of subsurface formations around deep-laying coal seams probed by means of atomic and nuclear-based techniques

A systematic investigation on the isotopic and elemental signature, for both stable and radioactive elements, and mineral contents was performed to examine the characteristics of subsurface formations collected at different depths between 3.962 km and 4.115 km around deep-laying coal seams located under the Marmarica plateau in Egypt. Concentrations of major and minor oxides (Na₂O, MgO, Al₂O₃, SiO₂, SO₃, K₂O, CaO, TiO₂, MnO, ΣFeO + Fe₂O₃, SrO, ZrO₂, and BaO) were determined by X-ray fluorescence and dependencies among these concentrations revealed the type and sort of the formations. Organic contents were determined by Fourier Transform infrared spectroscopy to investigate the variation of the CO/CC bonding ratio with depth. Rare earth elements (REE), specifically Y, Sc, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu were determined by inductively coupled plasma mass spectrometry while actinoids were detected by the radioactive decay of its daughter nuclei. The results showed a high trapping of REE elements and actinoids in layers above the coal seams which indicates the occurrence of aqueous flow followed by possible sorption in these layers. The mobility of the fluid was investigated using the process radioactive decay series between Ra226 and Ac228 from one side and their daughters from the other side.

Electro-assisted adsorption of Cs(I) and Co(II) from aqueous solution by capacitive deionization with activated carbon cloth/graphene oxide composite electrode

In this study, a new composite of activated carbon cloth/graphene oxide (ACC/GO) was prepared, characterized and used as electrode material for the electro-assisted adsorptive removal of Co²⁺ and Cs⁺ from aqueous solution. The ACC/GO composite was synthesized by a vacuum filtration method, and characterized by cyclic voltammetry and various surface characterization methods. Effect of applied voltage and initial concentration of Co²⁺ and Cs⁺ on their removal efficiency was examined. The kinetics and isotherms of Co²⁺ and Cs⁺ adsorption were investigated to explain the adsorption mechanism. At 0 V, the removal efficiency of Co²⁺ and Cs⁺ was 10.1% and 21.4%; at 1.2 V, electro-assistance increased the removal efficiency of Co²⁺ and Cs⁺ to 40.8% and 39.7%, respectively. Moreover, ACC/GO composite electrode had higher adsorption capacity compared to the pristine ACC electrode, due to its higher specific surface area and more oxygen-containing functional groups. The maximum adsorption capacity of Co²⁺ and Cs⁺ was 16.7 mg g^-1 and 22.9 mg g^-1, respectively at 1.2 V and 20 mg L^-1 by ACC/GO composite electrode. The modeling and experimental results demonstrated that the removal mechanism involved in physical adsorption, chemical adsorption, and electro-adsorption. Overall, the prepared ACC/GO composite electrode had high capacitive deionization performance in removing heavy metal ions from wastewater.

Mechanism study of metal ion adsorption on porous hydroxyapatite: experiments and modeling

In this study, low-cost biomaterial hydroxyapatite (N-Hap) prepared from bovine bones was tested for its potential to sorb copper Cu2+ and Fe3+ from aqueous solution and was compared with commercial hydroxyapatite (C-Hap). The structural characterization of N-Hap and C-Hap were carried out by Fourier transform infrared (FTIR) analysis, textural analysis (BET), morphology, and elemental analysis via scanning electron microscopy (SEM-EDX). The results obtained show that SEM images confirmed the formation of porous N-Hap with various morphologies and the average particle size ranges from 50 to 100 nm and the CaP ratio is 1.657. The presence of functional groups on N-Hap surface was confirmed by FTIR analysis. The specific surface areas of N-Hap and C-Hap are found to be 46.87 and 40.98 m2/g, respectively. Adsorption of two metals Cu2+ and Fe3+ was fast, with equilibrium attained within 30 min. Copper ions exhibited the greatest adsorption on both adsorbents because of their size and pH conditions. Metallic ion removal efficiency was favored at a slightly acidic solution pH and low temperature. The equilibrium and kinetic data were found to fit well the Langmuir model and the pseudo second order model with intraparticle diffusion. Thermodynamic parameters (ΔHads < 0 and ΔGads < 0) involved the exothermic, spontaneous, and physical adsorption process. The adsorption interaction of Cu2+ and Fe3+ with Hap surface was investigated by theoretical density functional theory (DFT) calculations. Therefore, the porous hydroxyapatite N-Hap displays potential as a new biocompatible adsorbent, and its use seems to be an interesting solution for the treatment of industrial wastewater.

Redox sorption of Ce(III)/Ce(IV) on potassium bismuthate

Potassium bismuthate rods was synthesized in a form of elongated rods in non-aqueous methanol medium. The material morphology and structure were investigated using energy dispersive spectroscopy, scanning electron microscopy, and X-ray diffraction. The effects of annealing temperature on the material morphology and structure were investigated. Sorption kinetic study and ionic selectivity was investigated using batch technique. The sorption of Ce3+ on potassium bismuthate was found to be Ce3+ cation’s ionic state selective process. Results showed that the chemical sorption of Ce3+ ionic state in KBiO3 follows the reduction of Bi5+ to Bi2− as a result of the formation of cerium bismuthide ( Ce 2 3 + Bi 2 − O 2 ) . $({\rm{Ce}}_2^{3 + }{\rm{B}}{{\rm{i}}^{2 - }}{{\rm{O}}_2}).$ The suggested chemo-sorption mechanism includes equilibration parallel processes of the released K+ to form K2CeO2 and Bi2O3 that consumes the original material. The sorption kinetic has two different orders depending on contact time, isotherms fits adequately with Freundlich model and Dubinin-Radushkevich model. The material is considered a candidate for lanthanides radioactivity removal from aqueous media for radioactive waste disposal processes.