Removal of Th(IV), Ni(II)and Fe(II) from aqueous solutions by a novel PAN–TiO2 nanofiber adsorbent modified with aminopropyltriethoxysilane

Evaluation of Adsorptive Capture and Release Efficiency of MNPs-SA@Cu MOF Composite Beads Toward U(VI) and Th(IV) Ions from an Aqueous Media

Effluent from nuclear power plants, rocks, and minerals contains hazardous radionuclides that adversely affect human health and seriously threaten the environment. To address this issue, simple, economic, and sustainable magnetite nanoparticle loaded sodium alginate copper metal-organic framework composite beads (MNPs-SA@Cu MOF composite beads) have been designed, and their performance has been evaluated under varying conditions of pH, time, adsorbent dose, and initial concentration and have been studied by batch adsorption studies for optimizing the adsorption conditions. In this work, MNPs-SA@Cu MOF composite beads have been prepared in situ for the adsorptive removal of uranium [U(VI)] and thorium [Th(IV)] ions from an aqueous solution. The synthesized MNPs-SA@Cu MOF composite beads were characterized by model analytical techniques like Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, Brunauer-Emmett-Teller, and thermal gravimetric analysis. Here, 6 mg of adsorbent with 10 mL of 50 mg/L uranium and thorium ion solution at pH 5 was capable of removing the U(VI) and Th(IV) ions with 99.9 and 97.7% removal efficiencies, respectively. The obtained results showed that the adsorption behavior of the adsorbent for U(VI) and Th(IV) follows pseudo-second-order kinetics, and Langmuir isotherm fitted well with a maximum adsorption capacity of 454.54 and 434.78 mg/g, respectively. The adsorption mechanism indicated that electrostatic interaction and hydrogen bonding are the main driving forces for removing the U(VI) and Th(IV) ions. It can be reused for up to 10 adsorption-desorption cycles with minimal loss of removal efficiency. The easy synthesis method of MNPs-SA@Cu MOF composite beads and the high removal efficiency of U(VI) and Th(IV) ions reveal that they can potentially treat radionuclide waste effectively.

Advances in electrospun materials for the adsorption and separation of environmental pollutants: A comprehensive review

Despite a broad range of new techniques developed, adsorption methods remain one of the technologies of choice for the removal of contaminants. However, significant progress has also been made in these, which finds reflection in a new spectrum of adsorbents that can be used. This comprehensive review discusses properties, advantages, and perspectives on the use of custom-made electrospun adsorbents in the processes of heavy metals, agrochemicals, and microplastic contaminants removal from the environment. It presents the versatility and adaptability of materials that can be used as electrospun fibers matrix, also considering the mechanism and parameters of the sorption process carried out with them. The presented review proves, that due to the use of new, custom-made sorbents, such as electrospun materials, the adsorption processes still possess great application potential and development opportunities to provide an attractive and effective alternative to other remediation techniques.

Selective separation and purification of cerium (III) from concentrate liquor associated with monazite processing by cationic exchange resin as adsorbent

The present study is directed to find the optimal conditions required for efficient separation and purification of Ce3+ as an analog for lanthanides from Fe3+, Th4+, and Zr4+ (interfering ions) using Amberlite IR120H (AIR120H) resin as a strongly cationic exchange adsorbent. The main factors affecting the separation processes had been investigated and optimized. Ce3+ (Ln3+) as an admixture with Fe3+, Th4+, and Zr4+ was successfully separated by batch and column techniques. The sorption efficiency (S, %) from different acidic media was in this order: HCl > HNO3 > H2SO4. In a quaternary mixture with Fe3+ and Th4+, the maximum separation factor between Ce3+ and Zr4+ was ~ 13 after 90 min of equilibration, and the sorption capacity of AIR120H resin for Ce3+ was 8.2 mg/g. The rate of adsorption was found to follow a pseudo-second-order kinetic model. Separation of the absorbed ions was achieved by desorption processes. Firstly, 98 ± 2% of loaded Ce3+ is fully desorbed by 1 M sodium acetate solution without interfering ions. Moreover, ~ 95% of Zr4+ is desorbed by 1 M citric acid solution. Finally, 85% of loaded Fe3+ and Th4+ ions are desorbed with 8 M HCl solution. The batch technique was applied to separate and purify Ln3+-concentrate in chloride liquor (LnCl3), coming from the caustic digestion of Egyptian high-grade monazite. However, the enhanced radioactivity in LnCl3 due to radium -isotopes (228Ra2+, 226Ra2+, 224Ra2+, 223Ra2+) and radio-lead (210Pb2+) is initially reduced by a factor of 92% (i.e., safe limit) by pH-adjustment. As result, it can be recommended that the sorption process by AIR120H resin is efficient and promising for exploring pure lanthanides from its minerals.

Green Nanoparticle-Aided Biosorption of Nickel Ions Using Four Dry Residual Biomasses: A Comparative Study

The green synthesis of titanium dioxide nanoparticles was performed using the sol-gel method for their use in the modification of several agricultural biomasses (orange, lemon, cassava and yam peels) to evaluate the enhancement of adsorption capacity. To this end, different particle sizes (0.355, 0.5 and 1.0 mm) and initial solution pHs (2, 4 and 6) were assessed to identify the optimum conditions for further experimentation with the selected lignocellulosic materials. The defined conditions reporting the highest removal yields were used to perform adsorption experiments for chemically modified biosorbents. The biomaterials were characterized via elemental and bromatological analysis in order to quantify their composition. After the incorporation of TiO2 nanoparticles, the resulting biosorbents were characterized via FT-IR and SEM techniques. The results revealed that the pH solution significantly affects the nickel ion uptake, reaching the best performance at pH = 6 for all biomasses. Unmodified biomasses shown adsorption capacities between 18–20 mg/g. For chemically modified with TiO2 orange peels and yam peels biomass, the increase in adsorption capacities was 21.3 and 18.01 mg/g, respectively. For cassava and lemon peels chemically modified, it was found the increasing in adsorption capacities with values of 21.3 and 18.01 mg/g, respectively, which suggested that the incorporation of nanoparticles enhances adsorption capacities.

Comparative Removal of Lead and Nickel Ions onto Nanofibrous Sheet of Activated Polyacrylonitrile in Batch Adsorption and Application of Conventional Kinetic and Isotherm Models

We investigated the adsorption of lead (Pb²⁺) and nickel (Ni²⁺) ions by electrospun membranes of polyacrylonitrile (PAN) nanofiber activated with NaHCO₃ (PANmod). Analysis by Fourier-transform infrared spectrometry (FTIR), field emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectroscopy (EDX) validated the functionalization of PAN nanofibers with NaHCO₃, and the successful agglomeration of Pb²⁺ and Ni²⁺ onto PANmod. After a rapid uptake of the heavy metal ions (15 min), the equilibrium contact time was attained (60 min) following a linear increase of both adsorption capacity and removal efficiency. PANmod showed a better affinity for Ni²⁺ than Pb²⁺. The adsorption on PANmod was best described by the pseudo-second-order kinetic model for both studied models, supporting chemisorption. By varying the solution pH from 2.0 to 9.0, we found that the adsorption capacity followed an increasing trend, reaching a maximum at the pH of 7.0. Despite increasing adsorption capacities, the removal efficiency of both heavy metal ions exhibited a decreasing trend with increase in initial concentrations. The amount of PANmod directly affects the removal efficiency, with 0.7 and 0.2 g being the optimum dose for maximum uptake of Pb²⁺ and Ni²⁺, respectively. The Langmuir model fitted well the Pb²⁺ adsorption data suggesting monolayer adsorption, and the Freundlich model perfectly fitted the Ni²⁺ adsorption data, indicating heterogeneous adsorption. The estimated values of the mean free energy of adsorption in the D–R isotherm indicated a physical adsorption of both heavy metal ions into the surface of the PANmod.