Removal of zirconium from aqueous solution by modified clinoptilolite

Nanostructured layered double hydroxide (NLDH) - Zn/Al-based materials: strategy to improve performance for zirconium sorption from acidic sulfate solution

Zirconium is a highly stable radionuclide commonly used in various nuclear operations. However, removing zirconium from wastewater streams is crucial to protect the environment and human health. To achieve this, a zinc and aluminum nanostructured layered double hydroxide (Zn/Al-NLDH) was prepared and investigated for effective removal of zirconium from aqueous solutions. This study examined the prepared Zn/Al-NLDH's structural and textural properties and the impact of various factors on its adsorption performance. The Langmuir isotherm and Pseudo-second order kinetic models were found to be the best fit for the adsorption process of Zr(vi). This suggests that the adsorption process is uniform, involves the formation of a monolayer, and is chemisorption in nature. The maximum uptake capacity was 117.6 mg g-1, and the process was endothermic, spontaneous, and feasible. About 96% of Zr(vi) was successfully desorbed from the loaded sorbent using 1.0 M hydrochloric acid, and the Zn/Al-NLDH sorbent remained stable for six consecutive sorption/desorption cycles. These findings emphasize the high potential of Zn/Al-NLDH to act as a remarkable sorbent for efficiently tackling water contaminants.

New insight into desorption behavior and mechanism of oil from aged oil-contaminated soil in microemulsion

The intractable nature of oil-contaminated soil (OS) constitutes the chief limiting factor for its remediation. Herein, the aging effect (i.e., oil-soil interactions and pore-scale effect) was investigated by analyzing the properties of aged OS and further demonstrated by investigating the desorption behavior of the oil from the OS. XPS was performed to detect the chemical environment of N, O, and Al, indicating the coordination adsorption of carbonyl groups (oil) on the soil surface. Alterations in the functional groups of the OS were detected using FT-IR, indicating that the oil-soil interactions were enhanced via wind-thermal aging. SEM and BET were used to analyze the structural morphology and pore-scale of the OS. The analysis revealed that aging promoted the development of the pore-scale effect in the OS. Moreover, the desorption behavior of oil molecules from the aged OS was investigated via desorption thermodynamics and kinetics. The desorption mechanism of the OS was elucidated via intraparticle diffusion kinetics. The desorption process of oil molecules underwent three stages: film diffusion, intraparticle diffusion, and surface desorption. Owing to the aging effect, the latter two stages constituted the major steps for controlling oil desorption. This mechanism provided theoretical guidance to apply microemulsion elution for remedying industrial OS.

Simultaneous CO2 reduction and NADH regeneration using formate and glycerol dehydrogenase enzymes co-immobilized on modified natural zeolite

In this work, the co-immobilization of formate dehydrogenase (FDH) and glycerol dehydrogenase (GlyDH) enzymes is proposed to reduce CO₂ into formic acid, an important chemical intermediate. The reduction of carbon dioxide is carried out by FDH to obtain formic acid, simultaneously, the GlyDH regenerated the nicotinamide cofactor in the reduced form (NADH) by the oxidation of glycerol into dihydroxyacetone. Natural zeolite was selected as immobilization support given its good properties and low cost. The natural zeolite was modified with subsequent acid-alkaline attacks to obtain a mesostructurization of the clinoptilolite. The two enzymes were co-immobilized on clinoptilolite, previously hetero-functionalized with amino and glyoxyl groups. The distribution of the enzymes was confirmed by fluorescence microscopy analysis. Furthermore, a great increase in the retained activity for the formate dehydrogenase enzyme was noted, passing from 18% to 89%, when the mesostructured clinoptilolite was used as support. The immobilization yield of formate dehydrogenase and glycerol dehydrogenase is around 100% with all the supports studied. The promising results suggest a possible development of this procedure in enzyme immobilization and biocatalysis. The biocatalysts were characterized to find the optimal pH and temperature. Furthermore, a thermal stability test at 50 °C was carried out on both enzymes, in free and immobilized forms. Finally, it was shown that the biocatalyst is effective in reducing CO₂, both by using the cofactor in the reduced form (NADH) or the oxidized form (NAD⁺), obtaining NADH through the regeneration with glycerol in this latter case.

How to Obtain Maximum Environmental Applicability from Natural Silicates

Unmodified natural silicates (bentonite, kaolin, clinoptilolite and diatomites) were tested as adsorbents for the organic pollutants in water tables using Methylene Blue (MB) as the model adsorbate. Among the selected materials, bentonite adsorbed as much as 237 mg/g, confirming its excellent suitability for pollutant removal. Spectral evidence confirmed successful MB immobilization at the bentonite surface. Furthermore, the thermal treatment of MB-saturated adsorbent in an inert atmosphere at 700 °C produced a carbon/silicate composite. EDX confirmed the formation of the nitrogen-doped carbon overlay on the silica scaffold and the obtained composite material was probed as an electrode material for oxygen reduction in an alkaline solution. Reduction proceeded via a two-electron mechanism with the main product being HO2−, a known nucleophile, which was subsequently used to degrade/demethylate MB. The composite showed a considerable 70% MB removal rate after an hour of electrochemical treatment. The synergy between the processes of adsorption of MB and the surface-generated HO2− dictates the efficiency of the method and points to a possible route for spent adsorbent reuse in the form of a durable product for environmental protection.

Clinoptilolite mediated activation of peroxymonosulfate through spherical dispersion and oriented array of NiFe2O4: Upgrading synergy and performance

Inspired by the features of both transition metal oxide and natural clinoptilolite (flaky structure with suitable pore diameter and open skeleton structure), we adopted a robust strategy by immobilization of nickel ferrite nanoparticles (NiFe₂O₄) on the clinoptilolite surface via typical citric acid combustion method. The hybrid catalyst exhibited enhanced peroxymonosulfate (PMS) activation efficiency and bisphenol A (BPA) degradation performance. Calculated by effective equivalent of NiFe₂O₄, it is found that the reaction rate constant (k) of NiFe₂O₄/clinoptilolite/PMS system (0.1859 min^-1) was 11.9 times higher than that of bare NiFe₂O₄/PMS system (0.0156 min^-1), which demonstrated that catalyst would be conjugated to PMS or contaminant efficiently and renders the rapid degradation and mineralization in the presence of clinoptilolite. After comprehensive characterization analysis and DFT simulations, natural mineral carrier effect (i.e. decreased crystalline size, increased oxygen vacancy content, etc.), abundant surface-bonded and structural hydroxyl groups as well as effective bonding with iron or nickel ions charged for the potential activation mechanism of PMS by NiFe₂O₄/clinoptilolite composite. And it is indicated that not only ^•OH and SO₄^•-, but also ¹O₂ was involved into series reactions. Overall, this study put forward a green and promising technology for high-toxic wastewater treatment.

Kinetics and adsorption equilibrium of some radionuclides on polyaniline/SiO2 composite

The sorption kinetics and equilibrium isotherms of zirconium, uranium, and molybdenum ions onto synthetic polyaniline/SiO2 composite (PAn/SiO2) have been studied using batch-sorption techniques. This study was carried out to examine the sorption behavior of the PAn/SiO2 for the removal of Zr(IV), U(VI), and Mo(VI) ions from an aqueous solution. The influence of some parameters on the sorption process was also studied. The maximum sorption for Zr(IV), U(VI), and Mo(VI) ions was achieved at 60 min shaking time. Langmuir isotherm model is the most representative for discussing the sorption process with a maximum sorption capacity of 24.26, 21.82, and 13.01 mg/g for Zr(IV), U(VI), and Mo(VI) ions, respectively. Kinetic modeling revealed that the sorption of all ions follows the pseudo-second-order kinetic model. The results demonstrated that both the external and intra-particular diffusion are taken into account in determining the sorption rate. Thermodynamic parameters like ΔG°, ΔH°, and ΔS° for the sorption process were evaluated. The synthetic composite has been successfully applied for the removal and recovery of U(VI) ions from real solution (monazite leachate) using a chromatographic column packed with PAn/SiO2 composite with a breakthrough capacity equal to 239.70 mg/g.

Research on mechanism and characteristics of oil recovery from oily sludge in ultrasonic fields

The acoustic parameters and operating conditions that determine efficiency of oil recovery from oily sludge are studied. Based on this, the mechanism of ultrasonic disintegration of oily sludge is analyzed. The results show that lower frequency ultrasound results in larger and more energetic cavitation bubbles that are more effective in the desorption of oil from solid particles. Moreover, acoustic intensity and treatment time that correspond to maximal oil recovery are found. Increasing the ratio of water to sludge and pH can reduce the slurry viscosity and facilitate the formation of HSiO₃^-, respectively, which improves the oil recovery efficiency. Moreover, Triton X-100 has better oil solubilizing effects than SDBS. After ultrasonic treatment, small amounts of asphaltenes are more stable on solid particles than other components. The heteroatoms such as S, N, and O in asphaltenes form hydrogen bonds with hydroxyl groups on the surface of the particles, impeding the desorption of oil. Mechanical effects such as shock waves and micro jets due to acoustic cavitation can break the hydrogen bonds between asphaltenes and solid particles, thereby facilitating oil recovery from oily sludge.

Chemisorption mechanism of crude oil on soil surface

One of the main challenges in cleaning crude oil-contaminated soil is the unknown adsorption mechanism between residual oil and soil. Herein, infrared spectrometer (IR) is used to detect the existence of dibutylphthalate (DBP) and pelargonamide on montmorillonite (MMT) surface. In addition, after the adsorption of DBP and pelargonamide on MMT, the bands in fingerprint region of the two IR spectra are almost identical, indicating coordination bonds were formed on the surface of MMT. X-ray photoelectron spectroscopy (XPS) is employed to detect the chemical environment of N, O and Al. The reverse migration of Al^2p spectrum and forward migration of N^1s and O^1s spectra indicate the coordination adsorption of carbonyl and amine groups on MMT surface. Then, density functional theory (DFT) calculations are applied to make a further explanation of the bonding mechanisms of DBP and pelargonamide onto MMT surfaces. The result shows that there are two types of aluminum on the surface of MMT acting as Lewis acid sites in coordination adsorption, namely Al³⁺/Si⁴⁺ isomorphic substitutions and Al³⁺ adsorbed on MMT by means of electrostatic adsorption. Meanwhile, the oxygenium on the surface of MMT acts as Brønsted bases in hydrogen bonding adsorption.

Sorption of some radionuclides from nuclear waste effluents by polyaniline/SiO2 composite: Characterization, thermal stability, and gamma irradiation studies

Polyaniline/SiO₂ composite was successfully prepared via in situ polymerization using polyvinyl alcohol as a surfactant. The prepared PAn/SiO₂ composite was used for the removal of Zr(IV), U(VI), and Mo(VI) ions from their liquid solutions. PAn/SiO₂ composite was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The synthesized composite was irradiated with γ-radiation from a Co-60 radioactive source with absorbed dose 50, 100, and 150 kGy and the corresponding changes in structural properties of the composites were studied. The thermal and radiation stabilities of PAn/SiO₂ composite in terms of saturation capacities were studied. PAn/SiO₂ composite has a good thermal stability as it retained about 78.83% of its saturation capacity upon heating at 400±1 °C, while the saturation capacity of PAn/SiO₂ composite was increased from 191.28 to 319.16 mg/g for Zr(IV) with varying the irradiated doses from 0 to 150 kGy. The sorption studies for several metal ions revealed marked selectivity of PAn/SiO₂ composite towards Zr(IV), U(VI), and Mo(VI) ions with selectivity order; Zr(IV) > U(VI) > Mo(VI). The results indicated that PAn/SiO₂ composite removed 95.33, 75.97, and 52.87% from Zr(IV), U(VI), and Mo(VI) ions, respectively at pH 3.26. Hence, analytical utility of PAn/SiO₂ composite was accomplished by performing some quantitative separation such as separation of U(VI) ions from monazite leachate and separation of Zr(IV), U(VI), and Mo(VI) ions from simulated liquid waste. Thermodynamic parameter studies concluded that the adsorption of Zr(IV), U(VI), and Mo(VI) ions was spontaneous and endothermic in nature.

Elimination of highly consumed herbicide; 2,4-dichlorophenoxyacetic acid from aqueous solution by TiO2 impregnated clinoptilolite, study of degradation pathway

In this research, the degradation of the highly consumed herbicide, 2,4-dichlorophenoxy acetic acid, was evaluated by a nanophotocatalyst prepared by impregnation of natural zeolite clinoptilolite with TiO₂. The photodegradation process of was studied under UV and visible light irradiations. To optimize the influencing parameters on the degradation efficiency, the Design Expert software and the Response surface methodology were used. The predicted values obtained by the methods were in good agreement with the experimental data. The degradation efficiency determined by UV-Vis spectroscopy indicated that the optimized degradation efficiency (58% by UV, and 31% by visible light) was obtained at pH = 6, catalyst dose of 0.4 g L^-1, pollutant concentration of 6 mg L^-1, and irradiation time of 95 min. The reaction mechanism was studied by Gaussian 03 program and a computer simulation method (density functional theory). The results were in good agreement with the results of the HPLC method used for identification of the degradation products. The mineralization of the pollutant was evaluated by measurement of total organic carbon of the degradation solution before and after irradiations. The results indicated that the degraded pollutant was mostly mineralized and converted to of CO₂ and H₂O.

A versatile proximity-dependent probe based on light-up DNA-scaffolded silver nanoclusters

It is well-known that proximity-dependent probes containing an analyte recognization site and a signal formation domain could be assembled specifically into a sandwich-like structure (probe-analyte-probe) via introducing an analyte. In this work, using the design for zirconium ion (Zr(4+)) detection as the model, we develop a novel and reliable proximity-dependent DNA-scaffolded silver nanocluster (DNA/AgNC) probe for Zr(4+) detection via target-induced emitter proximity. The proposed strategy undergoes the two following processes: target-mediated emitter pair proximity as target recognition implement and the synthesis of DNA/AgNCs with fluorescence as a signal reporter. Upon combination of the rationally designed probe with Zr(4+), the intact templates were obtained according to the -PO3(2-)-Zr(4+)-PO3(2-)- pattern. The resultant structure with an emitter pair serves as a potent template to achieve highly fluorescent DNA/AgNCs. To verify the universality of the proposed proximity-dependent DNA/AgNC probe, we extend the application of the proximity-dependent probe to DNA and adenosine triphosphate (ATP) detection by virtue of a specific DNA complementary sequence and ATP aptamer as a recognition unit, respectively. The produced fluorescence enhancement of the DNA/AgNCs in response to the analyte concentration allows a quantitative evaluation of the target, including Zr(4+), DNA, and ATP with detection limits of ∼3.00 μM, ∼9.83 nM, and ∼0.81 mM, respectively. The proposed probe possesses good performance with simple operation, cost-effectiveness, good selectivity, and without separation procedures.

Palladium-Zeolite nanofiber as an effective recyclable catalyst membrane for water treatment

Zeolite is an exciting natural material due to its unique capability of ammonium nitrogen (NH3N) adsorption in water. In this study, multifunctional hybrid composites of zeolite/palladium (Ze/Pd) on polymer nanofiber membranes were fabricated and explored for sustainable contaminant removal. SEM and XRD demonstrated that zeolite and palladium nanoparticles were uniformly distributed and deposited on the nanofibers. NH3N recovery rate was increased from 23 to 92% when palladium coated zeolite was embedded on the nanofiber. Multifunctional nanofibers of Ze/Pd membranes were able to adsorb NH3N on the zeolites placed on the surface of fibers and palladium catalysts were capable of selective oxidation of NH3N to N2 gas. The cycling of NH3N adsorption-oxidation, high flux, hydrophilicity, and flexibility of the membrane makes it a strong candidate for water treatment.

Removal of barium and strontium from aqueous solution using zeolite 4A

The adsorption efficiency of Sr(2+) and Ba(2+) from aqueous solutions by zeolite 4A was investigated. Adsorption studies were carried out both in single and binary component systems. The single ion equilibrium adsorption data were fitted to three isotherm models: Langmuir, Freundlich and Dubinin-Radushkevich. The Langmuir model represents the equilibrium data better than the Freundlich model in the studied initial metal concentration (0.3-25 mmol L(-1)) in both the single and binary component systems. The obtained RL (separation factor or Langmuir parameter) values were in the range of 0-1 indicating that Sr(2+) and Ba(2+) sorption were favorable. The obtained mean free energy value for adsorption of Ba(2+) and Sr(2+) was 8.45 kJ mol(-1) and 9.12 kJ mol(-1), respectively, indicating that both ions were uptaken through an ion exchange process. The maximum adsorption capacities (Qmax) were 2.25 mmol g(-1) and 2.34 mmol g(-1) for Ba(2+) and Sr(2+) ions, respectively. Also, the study of the competitive sorption of ions in the binary system showed that zeolite 4A preferentially adsorbs cations in the following order: Ba(2+) < Sr(2+).

Enhancement in photocatalytic activity of NiO by supporting onto an Iranian clinoptilolite nano-particles of aqueous solution of cefuroxime pharmaceutical capsule

NiO/nano-clinoptilolite (NiO-NCP) was prepared by ion exchanging process of the prepared ball-mill nano-clinoptilolite particles with nickel(II) chloride aqueous solution. The prepared composite was characterized by XRD, UV-Vis DRS, TEM and FT-IR and then used as a catalyst in the photodegradation of cefuroxime (CF) using Hg lamp. The best experimental parameters were obtained as: 0.025 g L(-1) of the photocatalyst containing 13.3% NiO, 50 times diluted cefuroxime solution at pH 5. The degradation extent was monitored by UV-Vis spectroscopy and the results were confirmed by HPLC and COD. The kinetics of the photodegradation process obeyed the Langmuir-Hinshelwood model.

Preparation of zirconium oxy ion-imprinted particle for the selective separation of trace zirconium ion from water

Zr(IV) oxy ion-imprinted particle (Zr-IIP) was prepared using the metal ion imprinting technique in a sol-gel process on the surface of amino-silica. The dosages of zirconium ions as imprinted target, (3-aminopropyl) triethoxysilane (APTES) as a functional monomer and teraethyl orthosilicate (TEOS) as a cross-linker were optimized. The prepared Zr-IIP and Zr(IV) oxy ion non-imprinted particle (Zr-NIP) were characterized. pH effect, binding ability and the selectivity were investigated in detail. The results showed that the Zr-IIP had an excellent binding capacity and selectivity in the water. The equilibrium data fitted well to the pseudo-second-order kinetic and the Langmuir model for Zr(IV) binding onto Zr-IIP, respectively. The saturate binding capacity of Zr-IIP was found to be 196.08 μmol g(-1), which was 18 times higher than that of Zr-NIP. The sequence of binding efficiency of Zr-IIP for various ions was Zr(IV)>Cu(II)>Sb(III)>Eu(III). The coordination number has an important effect on the dimensional binding capacity. The equilibrium binding capacity of Zr-IIP for Zr(IV) decreased little under various concentrations of Pb(II) ions. The analysis of relative selectivity coefficient (Kr) indicated that the Zr-IIP had an appreciable binding specificity towards Zr(IV) although the competitive ions coexisted in the water. The Zr-IIP could serve as an efficient selective material for recovering or removing zirconium from the water environment.