Isotherm, kinetic, and thermodynamic studies for sorption of Cu(II) and Pb(II) by activated carbon prepared fromLeucaenaplant wastes

Facile Strategy for Fabricating an Organosilica-Modified Fe3O4 (OS/Fe3O4) Hetero-nanocore and OS/Fe3O4@SiO2 Core-Shell Structure for Wastewater Treatment with Promising Recyclable Efficiency

The development of a sustainable process for heavy metal ion remediation has become a point of interest in various fields of research, including wastewater treatment, industrial development, and health and environmental safety. In the present study, a promising sustainable adsorbent was fabricated through continuous controlled adsorption/desorption processes for heavy metal uptake. The fabrication strategy is based on a simple modification of Fe₃O₄ magnetic nanoparticles with organosilica in a one-pot solvothermal process, carried out in order to insert the organosilica moieties into the Fe₃O₄ nanocore during their formation. The developed organosilica-modified Fe₃O₄ hetero-nanocores had hydrophilic citrate moieties, together with hydrophobic organosilica ones, on their surfaces, which facilitated the further surface coating procedures. To prevent the formed nanoparticles from leaching into the acidic medium, a dense silica layer was coated on the fabricated organosilica/Fe₃O₄ (OS/Fe₃O₄). In addition, the prepared OS/Fe₃O₄@SiO₂ was utilized for the adsorption of cobalt(II), lead(II), and manganese(II) from the solutions. The data for the adsorption processes of cobalt(II), lead(II), and manganese(II) on OS/(Fe₃O₄)@SiO₂ were found to follow the pseudo-second-order kinetic model, indicating the fast uptake of heavy metals. The Freundlich isotherm was found to be more suitable for describing the uptake of heavy metals by OS/Fe₃O₄@SiO₂ nanoparticles. The negative values of the ΔG° showed a spontaneous adsorption process of a physical nature. The super-regeneration and recycling capacities of the OS/Fe₃O₄@SiO₂ were achieved, comparing the results to those of previous adsorbents, with a recyclable efficiency of 91% up to the seventh cycle, which is promising for environmental sustainability.

Decontamination of 137Cs,95Zr, 154Eu and 144Ce from aqueous solutions using polyacrylamide titanium tungstosilicate

Polyacrylamide titanium tungstosilicate (PAM/TiWSi) composite was synthesised using a sol–gel process and characterized via FT-IR, SEM, XRD, and TGA methods. The effects of several factors on the adsorption of Cs+, Eu3+, Ce3+and Zr4+ have been studied, including contact duration, pH, temperature, and starting concentration. PAM/TiWSi sorption of Cs+, Eu3+, Ce3+and Zr4+ was studied in terms of isotherms and kinetics. The Freundlich model was better linked with isotherm data than the Langmuir model. Cs+, Eu3+, Ce3+and Zr4+ have maximum sorption capacities (Qmax) of 30.7, 26.6, 25,3 and 29.7 mg.g−1, respectively. Furthermore, the sorption process was found based on pseudo-second-order.

Fabrication and application of nanosized stannic oxide for sorption of some hazardous metal ions from aqueous solutions

A batch equilibrium method was utilized to evaluate the retention of Fe(III) and Pb(II) onto stannic oxide (SnO2) nanomaterial. SnO2 was prepared by a simple precipitation method and characterized by different analytical apparatuses like FT-IR, SEM, TEM, and XRD. Scherrer’s formula and Williamson-Hall (WH) analysis were utilized to detect the crystallite size and lattice strain. The XRD and TEM data revealed that SnO2 has a nanoscale and crystalline nature. The retention study for Fe(III) and Pb(II) includes the influence of shaking time, batch factor, pH, initial concentrations, capacity, and applications. The data reveal that the maximum uptake of SnO2 was achieved at pH 2.5 and 3.7 for Fe(III) and Pb(II), respectively. SnO2 has a fast kinetic (60 min) and the reaction kinetic data obey the pseudo–second-order model. The capacity has values of 50.4 and 48.8 mg/g for Fe(III) and Pb(II), respectively. The real sample applications proved that SnO2 is an excellent sorbent for the capture of Pb(II) and Fe(III) from industrial wastewater and low-grade monazite (LGM) respectively, in addition to the capture of 59Fe radionuclide from low-level radioactive waste (LLRW).

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.

Adsorptive removal of PAR and Arsenazo-III from radioactive waste solutions by modified sugarcane bagasse as eco-friendly sorbent

In this paper, sugarcane bagasse (SCB) was modified using phosphoric acid. The modified sugarcane bagasse (MSCB) has been used to remove 4-(2-pyridylazo)resorcinol (PAR) and Arsenazo-III (Ar-III) from liquid radioactive waste. The surface morphology and functional groups of the MSCB were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). Adsorption ability of MSCB has been tested by batch mode through some relevant factors like initial pH, reaction time, initial coloring reagents (PAR and Ar-III) concentrations, and adsorbent weight. At adsorption equilibrium time 180 min and pH values of 3 and 1 for PAR and Ar-III; the maximum removal (%) for both PAR and Ar-III were 93 and 57%, respectively. The adsorption isotherm data are representative well to Freundlich isotherm model. The mean free energy of adsorption, E (kJ/mol), has been estimated as 5.75 and 2.28 kJ/mol for PAR and Ar-III, respectively, which suggests that the adsorption occurred physically. The maximum adsorption capacity of MSCB for PAR and Ar-III is 96.62 and 15.18 mg/g, respectively. The adsorption kinetics are better fitted by the pseudo-second-order model. The partial film along with intra-particle diffusion controlled the diffusion of coloring reagents from the solution bulk to the particle interior pores. Application of MSCB for removing PAR and Ar-III from simulated liquid radioactive waste containing U(VI) and Th(VI) ions has been achieved successfully.

Removal of strontium radionuclides from liquid scintillation waste and environmental water samples

Strontium-90 (t_1/2 = 29 y) is one of the most concerned isotopes in both nuclear accidents and reprocessing of nuclear fuel. In this study, the removal of strontium using low cost and valuable Dowex-HCR-S/S (DHS) resin was achieved. The kinetic and equilibrium sorption studies have been investigated using batch technique. The results of kinetic studies showed that the pseudo-second-order kinetic model was found to correlate well with the experimental data. Equilibrium data were also analyzed by sorption isotherm models indicating that the monolayer capacity of Sr(II) at equilibrium is 400.0 mg/g. It was concluded that resin has an efficient sorption capacity compared to many sorbents. The thermodynamic parameters of the removal (ΔH^o, ΔS^o, and ΔG^o) were also determined. The removal process was endothermic and spontaneous. The resin has been successfully applied for the removal of ⁸⁵Sr from organic liquid scintillator waste and some environmental waters such as tap water, river water, sea water and ground water samples. The present work concludes that the low-cost and commercial DHS resin used under these conditions has a major possibility as an efficacious material for the removal of ⁹⁰Sr from environmental and real radioactive wastewaters. It can therefore have a site in the treatment of radioactive liquid waste because it is of an affordable and commercially available retention material.