Utilization of nano-cryptomelane for the removal of cobalt, cesium and lead ions from multicomponent system: Kinetic and equilibrium studies

Cesium adsorption from an aqueous medium for environmental remediation: A comprehensive analysis of adsorbents, sources, factors, models, challenges, and opportunities

Considering the widespread and indispensable nature of nuclear energy for future power generation, there is a concurrent increase in the discharge of radioactive Cs into water streams. Recent studies have demonstrated that adsorption is crucial in removing Cs from wastewater for environmental remediation. However, the existing literature lacks comprehensive studies on various adsorption methods, the capacities or efficiencies of adsorbents, influencing factors, isotherm and kinetic models of the Cs adsorption process. A bibliometric and comprehensive analysis was conducted using 1179 publications from the Web of Science Core Collection spanning from 2014 to 2023. It reviews and summarizes current publication trends, active countries, adsorption methods, adsorption capacities or efficiencies of adsorbents, tested water sources, influencing factors, isotherm, and kinetic models of Cs adsorption. The selection of suitable adsorbents and operating parameters is identified as a crucial factor. Over the past decade, due to their notable capacity for Cs adsorption, considerable research has focused on novel adsorbents, such as Prussian blue, graphene oxide, hydrogel, and nanoadsorbents (NA). However, there remains a need for further development of application-oriented laboratory-scale experiments. Future research directions should encompass exploring adsorption mechanisms, developing new adsorbents or their combinations, practical applications of lab-scale studies, and recycling radioactive Cs from wastewater. Drawing upon this literature review, we present the most recent research patterns concerning adsorbents to remove Cs, outline potential avenues for future research, and delineate the obstacles hindering effective adsorption. This comprehensive bibliometric review provides valuable insights into prevalent research focal points and emerging trends, serving as a helpful resource for researchers and policymakers seeking to understand the dynamics of adsorbents for Cs removal from water.

A novel bio-based fluorescent N, P-CDs@CMC/PEI composite hydrogel for sensitive detection and efficient capture of toxic heavy metal ions

To address the serious environmental pollution problems of toxic heavy metal ions in water bodies, a novel fluorescent composite hydrogel N, P-CDs@CMC/PEI with a bio-based polymer matrix of carboxylmethyl cellulose (CMC), polyethylenimine (PEI) as a second interpenetrating network and N, P-doped carbon dots (N, P-CDs) as a fluorescent probe was prepared for simultaneous detection and capture of HMIs by a facile and simple one-step approach. The morphology, chemical structure, swelling ratio, mechanical strength and fluorescence property of these composite hydrogels were studied through varied characterization methods. The composite hydrogel showed sensitive and selective fluorescence response with Hg(II) and Fe(III) and the according LOD values were 0.48 and 0.27 mg L-1, respectively. The relationship between the types of the adsorbent, pH value, HMIs concentration and temperature on the adsorption capacity of these composite hydrogels were studied. The pseudo-second-order model and Langmuir model were applicable to explain the adsorption process of CPH2 for Hg(II) and Cr(VI). The maximum calculated adsorption capacities for the above targeted HMIs by Langmuir model were 846.7 and 289.5 mg g-1, respectively. Coexisting inorganic salts and organic acids in low concentration had little effects on Hg(II) and Cr(VI) removal and the composite hydrogel showed good recyclability and stability for Hg(II) and Cr(VI) removal after four cycles. The electrostatic attraction and coordination covalent bonds were responsible for the adsorption process.

One-pot synthesis of novel mesoporous FeOOH modified NaZrH(PO4)2·H2O for the enhanced removal of Co(II) from aqueous solution

One-pot synthesis of a novel mesoporous hydroxyl oxidize iron functional Na-zirconium phosphate (FeOOH-NaZrH(PO4)2·H2O) composites was firstly characterized and investigated its Co(II) adsorption from aqueous solution. Compared to NaZrH(PO4)2·H2O (65.7 mg⋅g-1), the maximum Co(II) adsorption capacity of FeOOH-NaZrH(PO4)2·H2O was improved to be 95.1 mg⋅g-1. BET verified the mesoporous structures of FeOOH-NaZrH(PO4)2·H2O with a larger pore volume than NaZrH(PO4)2·H2O. High pH values, initial Co(II) concentration, and temperature benefited the Co(II) adsorption. Kinetics, isotherms, and thermodynamics indicated an endothermic, spontaneous chemisorption process. FeOOH-NaZrH(PO4)2·H2O has a better Co(II) adsorption selectivity than that of NaZrH(PO4)2·H2O. In particular, FeOOH-NaZrH(PO4)2·H2O exhibited an outstanding reusability after ten cycles of tests. The main possible mechanism for adsorbents uptake Co(II) involved in ion exchange, electrostatic interaction, and -OH, Zr-O bond coordination based on FTIR and XPS analysis. This work presents a feasible strategy to prepare novel modified zirconium phosphate composites for extracting Co(II) from solutions and providing a new insight into the understanding of Co(II) adsorption in the real nuclear Co(II)-containing wastewater.

Insights into interactions of biodegradable and non-biodegradable microplastics with heavy metals

Biodegradable microplastics (BMPs) are considered to be environmentally friendly compared to non-biodegradable plastics (NMPs). However, BMPs are likely to become toxic during their transport because of the adsorption of pollutants (e.g., heavy metals) onto them. This study investigated the uptake of six heavy metals (Cd2+, Cu2+, Cr3+, Ni2+, Pb2+, and Zn2+) by a common BMPs (polylactic acid (PLA)) and compared their adsorption characteristics to those of three types of NMPs (polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC)) for the first time. The order of heavy metal adsorption capacity among the four MPs was PE > PLA > PVC > PP. The findings suggest that BMPs contained more toxic heavy metals than some NMPs. Among the six heavy metals, Cr3+ showed considerably stronger adsorption than other heavy metals in both BMPS and NMPs. The adsorption of heavy metals on MPs can be well explained using the Langmuir isotherm model, while the adsorption kinetic curves showed the best fit to the pseudo-second-order kinetic equation. Desorption experiments revealed that BMPs released a higher percentage of heavy metals (54.6-62.6%) in the acidic environment in a shorter time (~ 6 h) compared to NMPs. Overall, this study provides insights into interactions of BMPs and NMPs with heavy metals and their removal mechanisms in aquatic environment.

Fabrication of magnesium oxide-calcium alginate hydrogel for scaffolding yttrium and neodymium from aqueous solutions

In this research, the possibility of using sustainable nano-MgO/Ca-alginate beads for efficient sorption of some rare earth metal ions such as neodymium(III) and yttrium(III) from an aqueous acidic solution was explored. The nano-MgO/Ca-alginate beads adsorbent was characterized before and after sorption of Nd(III) and Y(III) using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), energy dispersive X-ray analysis (EDX), and X-ray diffraction (XRD) techniques. Batch sorption parameters were investigated, such as contact time, initial metal ion concentration, and adsorbent dose (V/m). The calculated experimental results showed that the suitable selected sorption conditions were carried out using 100 mg/L of Nd(III) and Y(III) with nano MgO/Ca-alginate beads (contact time = 90 min, pH = 2, V/m = 0.05 L/g). The maximum sorption capacity of 0.1 g of nano MgO/Ca-alginate was found to be 7.85 mg/g and 5.60 mg/g for Nd(III) and Y(III), respectively. The desorption of Nd(III) and Y(III) from the loaded nano MgO/Ca-alginate was achieved with 1.0 M sulfamic acid and found to be 51.0% and 44.2%, respectively. The calculated thermodynamic parameters for the nano MgO/Ca-alginate/Nd/Y system show that the positive charge of ΔHo confirmed the endothermic nature of the sorption process, ΔSo (positive) indicates an increase in reaction system disordering, and ΔGo (negative) indicates a spontaneous process. These kinetic results indicate that the sorption process of Nd(III) and Y(III) on nano MgO/Ca-alginate beads is performed by the chemisorption process.

Active carbon-based waste packaging materials for uranium sorption from aqueous solution

Waste (packaging plastic and industrial water) accumulation is one of the great global challenges over the world. Combining waste recycling science and water treatment knowledge are fascinating as applied sciences add value to the safe disposal of waste plastic packaging materials and wastewater. Active carbons (ACs) are prepared from polyethylene terephthalate (PET) at two pyrolysis temperatures (i.e. 450 and 500 °C) and compressed in well-defined designed molds to form cylinder shapes as applied in industry. Particle size (817 and 1074 nm), zeta potential (- 7.17 and - 25.6 mV), surface area (544 and 632 m2/g), and topography of prepared ACs were investigated and discussed. Zeta potential exhibited nice dispersion in accordance to charge value and surficial SEM images prove space hole filling with adsorbed materials after treatment. The prepared activated carbon sorbents have been applied for the removal of radioactive elements from wastewater. The displayed data declare that both sorbents have the same sorption performance, whereas the uranium sorption process using both sorbents is obeyed to pseudo-second-order kinetic model and Langmuir isotherm model. Nevertheless, it is worth noting that the prepared AC at a pyrolysis temperature of 500 °C exhibits higher sorption capacity (38.9 mg g^-1) than that prepared at lower temperature, i.e., 450 °C (36.2 mg g^-1) which indicates that the increase in pyrolysis temperature improves the sorption characteristics of the yield-activated carbon.

Performance of molybdenum vanadate loaded on bentonite for retention of cesium-134 from aqueous solutions

This article studied the sorption behavior of Cs(I) ions from aqueous solutions onto molybdenum vanadate@bentonite (MoV@bentonite) composite. MoV@bentonite has been fabricated using the precipitation method and was characterized by different analytical tools including, FT-IR, XRD, and SEM attached with an EDX unit. The sorption studies applied on Cs(I) ions include the effect of contact time, pH, initial metal concentrations, ionic strength, desorption, and recycling. The experimental results revealed that in the adsorption process carried out after equilibrium time (300 min), saturation capacity has a value of 26.72 mg·g^-1 and the sorption of Cs(I) ions is dependent on pH values and ionic strength. Sorption kinetic better fit with the pseudo-second-order model; sorption isotherms apply to Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models. Data of thermodynamic parameters indicate that sorption is spontaneous and endothermic. Recycling experiments show that MoV@bentonite could be used for 7 cycles and the best eluant for the recovery of Cs(I) ions is 0.1 M HCl (76.9%). All the obtained data clarify that MoV@bentonite is considered a promising sorbent for the sorption of Cs(I) ions from aqueous solutions.

Construction of efficient Ni-FeLDH@MWCNT@Cellulose acetate floatable microbeads for Cr(VI) removal: Performance and mechanism

Water pollution is an aggravating dilemma that is extending around the world, threatening human survival. Strikingly, the notorious heavy metals like hexavalent chromium ions (Cr⁶⁺) cause environmental problems raising awareness of the essentials for finding feasible solutions. For this purpose, the self-floating Ni-FeLDH@MWCNT@CA microbeads were prepared for removing Cr⁶⁺. The morphological, thermal, and composition characteristics of Ni-FeLDH@MWCNT@CA microbeads were analyzed using XRD, FTIR, TGA, SEM, XPS, and zeta potential. Notably, the adsorption aptitude of Cr⁶⁺ was enhanced by raising the MWCNTs proportion to 5 wt% in microbeads. The Cr⁶⁺ adsorption onto Ni-FeLDH@MWCNT@CA fitted Langmuir and Freundlich isotherm models with q_m of 384.62 mg/g at pH 3 and 298 K. The adsorption process was described kinetically by the pseudo-2nd order model. More importantly, the adsorption of Cr⁶⁺ onto Ni-FeLDH@MWCNT@CA occurred via electrostatic interactions, inner/outer sphere complexations, ion exchange, and reduction mechanisms. Besides, the cycling test showed the remarkable reusability of Ni-FeLDH@MWCNT@CA floatable microbeads for five subsequent cycles. The self-floating Ni-FeLDH@MWCNT@CA microbeads in this work provide essential support for the potential applications for the remediation of heavy metals-containing wastewater.

Use of activated Chromolaena odorata biomass for the removal of crystal violet from aqueous solution: kinetic, equilibrium, and thermodynamic study

In the present study, biomass from the Chromolaena odorata plant's stem was activated using sulfuric acid to adsorb crystal violet (CV) dye. The adsorption operation of CV dye was studied considering the effect of variables like pH, initial dye concentration, time, adsorbent dosage, and temperature. The pseudo-second-order equation best fitted the kinetic study. The thermodynamic parameters such as activation energy (9.56 kJ/mol), change in Gibbs energy (81.43 to 96.7 kJ/mol), enthalpy change (6.89 kJ/mol), and entropy change (-254.4 J/mol K) were calculated. Response surface methodology estimated that at pH (4.902), adsorbent dosage (8.33 g/L), dye concentration (82.30 ppm), and temperature (300.13 K) dye removal of 97.53% is possible. FTIR, SEM, XRD, BJH, and BET confirmed adsorption operation. The adsorbent can be reused for 3 cycles effectively. Langmuir isotherm which best fitted the adsorption operation was used for designing a theoretical single-stage batch adsorber for large-scale operation.

Post-irradiation physicochemical features of polymer composite for the removal of Co(II) and Nd(III) from aqueous solutions

The scientific impact of this work is the protection of the environment from hazardous pollutants. Gamma irradiation was employed for the preparation of a new composite polymer by irradiating a mixture containing polyvinyl pyrrolidone (PVP), hydroxyethyl methacrylate (HEMA), and tannic acid (TA) to produce PVP-HEMA-TA. The sorption efficiency and capacity of PVP-HEMA-TA were evaluated by studying some factors affecting the sorption of Nd(III) and Co(II) from aqueous solutions. The results demonstrated that the maximum uptake was 92.4 and 75.3% for Nd(III) and Co(II), respectively. From the kinetic studies, the pseudo-second-order equation could better fit the data than the pseudo-first-order for the sorption of both ions. The sorption isotherm investigations illustrated that the Langmuir equation fits the gained data better than Freundlich equation. The Langmuir capacity was 64.5 and 60.8 mg/g for neodymium and cobalt ions, respectively. The applicability of Langmuir equation is strong evidence that the process is limited by a chemisorption mechanism. Findings of the work highlight the potential utilization of PVP-HEMA-TA as an effective and recyclable material for the elimination of Nd(III) and Co(II) from the aqueous phase.

Ni-alginate hydrogel beads for establishing breakthrough curves of lead ions removal from aqueous solutions

The scientific impact of this work is the protection of the environment from hazardous pollutants using a column technique. Besides its higher stability at working pH and its time persisting, Ni-alginate has a higher ability to remove lead ions compared to the other prepared beads (Sr-alginate, Co-alginate, and Ca-alginate). Also, Ni-alginate possessed a higher removal percent, 93.3%, toward Pb2+ than the other ions, taking the sorption order of Pb2+ > Sr2+ > Co2+ > Cd2+ > Zn2+. Therefore, this study focused on using Ni-alginate as a selective sorbent for lead ions. Fixed-bed column was employed for the sorption process. The results for that efficiency are presented as breakthrough curves in view of the impact of various parameters; influent flow rate (1.5, 3.0, and 5.0 mL/min), lead concentration (100, 150, and 200 mg/L), and bed depth of sorbent (3.0, 5.0, and 7.0 cm). Breakthrough modeling including Thomas and Yan models was employed. The outcomes indicated that Thomas theory is more applicable. The overall outcomes indicated that Ni-alginate is recommended for selective removal of Pb2+ from waste solutions.

Adsorption kinetics and equilibrium of Ni2+, Cu2+, Co2+, and Ag+ on geopolymers derived from ashes: application to treat effluents from the E-Coat printing process

Geopolymers were obtained from ashes through an alternative geopolymerization process and applied to remove Ni²⁺, Cu²⁺, Co²⁺, and Ag⁺ from synthetic aqueous media and real effluents. The study in synthetic solutions revealed that pseudo-second-order and general order models were the best to fit the kinetic curves. To represent the equilibrium curves, Langmuir and Freundlich were the most adequate. The geopolymer derived from bottom ash (GHA) was superior to adsorb Cu⁺², Co⁺², and Ag⁺¹ than the geopolymer derived from fly ash (GFA). GHA reached adsorption capacities of 279.5, 288.2, and 462.8 mg g^-1 for Co⁺², Cu⁺², and Ag⁺¹, respectively. Otherwise, GFA was the best for Ni⁺² removal, with an efficiency of 95% in low concentrations. In treating real effluents of the E-coat printing process, both GHA and GFA were efficient, with the removal of higher than 85% for all the metals. In brief, it can be stated that GFA and GHA prepared are promising materials to remove metals from aqueous media (synthetic and real), presenting fast adsorption kinetics, high adsorption capacity, and high metal removal percentage.

Utilization of synthetic nano-cryptomelane for enhanced scavenging of cesium and cobalt ions from single and binary solutions

The feasibility of using nano-cryptomelane for elimination of cobalt and cesium metal ions from their single and binary solutions was studied. In this respect, the material was prepared and characterized to confirm its chemical composition and structure. Results illustrate that the synthesized nano-cryptomelane has a tunnel structure with particle size ranged between 4 and 6 nm. The material feasibility was detected by conducting a series of batch experiments for determination of the kinetic and equilibrium performance of the removal process. All characteristic Raman bands for Mn–O lattice vibrations within the (2 × 2) tunnel structure of MnO6 octahedral are observed which confirm formation of nano-cryptomelane. The specific surface area (SSA) for nano-cryptomelane was calculated and equal to 299.03 m2/g while the surface fractal information (Ds) was2.53. The process sensitivity to changes of H+ concentration is attributed to changes in structural elements-species distribution at the solid/aqueous interface. The pH optimum value was desired at pH 5 for exchange of Cs+ and/or Co2+ with K+ ions. The equilibrium studies show that Langmuir isotherm model was more fitted to the experimental data than that of Freundlich model.

Sorbent extraction behavior of cesium and strontium from nitric acid solutions using a new high thermal stability material

In this study a new low-cost carbonaceous material was prepared from husks of opuntia-ficus-indica as a starting material (precursor) which was accomplished by chemical activation route using H₃PO₄ impregnation. The material has been identified by different analytical tools. The sorption performance of Cs(I) and Sr(II) from HNO₃ solutions was examined through batch system. Variations of the distribution coefficients (K_d) as a function of HNO₃ concentration in the range 0.001-5.0 M were presented. Some of separation probabilities were suggested. The results attained signals that the Sr(II) selectivity is higher than that of Cs(I) at high molarities. The retention capacity (q_e) of Cs(I) and Sr(II) ions increased with growing temperature. The capacities at 0.001 M HNO₃ are 34 and 108 mg/g for Cs(I) and Sr(II), respectively. Whereas, at 2.0 M HNO₃ capacities were about 4 and 37 mg/g for each of Cs(I) and Sr (II), respectively. This studies demonstrates that the prepared carbonaceous sorbent is an economically effective sorbent for retention of Cs(I) and Sr(II) species from HNO₃ solutions. Cs(I) and Sr(II) removal potential was tested from simulated low- and intermediate-level radioactive waste samples.

Ecofriendly, selective removal of radioactive strontium ions in aqueous solutions using magnetic banana peels

Radionuclide Sr²⁺ in aqueous solution was removed using a large amount of banana peel (BP). Magnetized BP, mag@BP, was synthesized for recovery after the adsorption process. The synthesis was a very simple process of precipitation of BP with a magnetic substance. The synthesized adsorbent was thoroughly examined by performing Fourier-transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction analysis, and vibration sample magnetometer analysis. Moreover, mag@BP has a Sr²⁺ maximum adsorption capacity of 23.827 mg/g according to isothermal adsorption, which is the best fit for the Langmuir isotherm model. In the pH effect experiment, the highest Sr²⁺ adsorption capacity was found at pH 9, and it has a spontaneous adsorption mechanism through experiments on temperature, time, and selectivity, and it reaches adsorption equilibrium within a short time and has high selectivity through competitive adsorption with Na⁺. In addition, an adsorption mechanism accompanied by ion exchange with K⁺ on the surface of BP, bonding with various functional groups, and electrical attraction were established. Therefore, mag@BP is suitable for use an environmentally friendly, low cost, and recoverable adsorbent for magnetic removal of Sr²⁺ from aqueous solutions. Further, unlike other carbon-based adsorbents, it does not cause cytotoxicity.

Influence of sorption parameters on cesium-137 removal using modified activated carbon obtained from corchorus olitorius stalks

Removal of 137Cs radionuclides from the environment has engrossed the concern of researchers after Fukushima accident. The leakage of radioactive cesium ions can lead up to surface and groundwater contamination, and this leads to pollution of drinking water sources. In this work, corchorus olitorius stalks has been used as a novel precursor for production of low-cost meso porous a ctivated c arbon ( Meso-AC ) and HNO3/H2O2- m odified Meso-AC ( m-Meso-AC ). The physicochemical properties of all adsorbents were evaluated. The influences of sorption parameters and presence of some ligands (humic acid, fulvic acid, and EDTA) on the sorption of 137Cs were studied. The maximum 137Cs capacity of m-Meso-AC was found to be 58.74 mg/g. Efficiency of the new adsorbent to remove 137Cs radionuclides from natural waters (tap, river, and groundwater) was investigated. The studies showed that new adsorbent could be used as promising material for the retention of 137Cs from real radioactive waste and natural water samples.

Prepared self-growing supported nickel catalyst by recovering Ni (Ⅱ) from metal wastewater using geopolymer microspheres

Here, new and effective microsphere adsorbents were synthesized by NaOH activating slag based geopolymer (Na-SGS). These microsphere adsorbents upset the adsorption equilibrium with the maximum Ni²⁺ adsorption capacity of 414.38 mg/g which is much larger than that of other geopolymer materials. After Ni²⁺ adsorption from simulated nickel electroplating wastewater, more active positions for the adsorption Ni²⁺ ions on Na-SGS were provided as shifts from the average pore diameter of 22.00-7.44 nm, the pore volume of 0.06 to 0.25 cm³/g, the Brunauer-Emmett-Teller (BET) surface area of 10.46-125.35 m²/g and the apparent change of new morphology. Moreover, the adsorbed Ni²⁺ species were distributed uniformly on Na-SGS. Thermodynamic performance reflected an exothermic, spontaneous and molecular disorder adsorption process, which can be easily controlled by the pH, dosage, initial concentration, contact time and temperature. Through the controllable adsorption, Na-SGS after Ni²⁺ adsorption (Na-SGS-Ni) was recycled and then reduced to be directly supported nickel catalysts (red-Na-SGS-Ni), which showed superior catalytic activity for CO₂ methanation. Although the highest percent of CO₂ conversation (XCO₂ =99.54%) and methane selectivity (SCH₄ =99.5%) are both at 300 °C, red-Na-SGS-Ni performed good XCO₂ (99.48%) and SCH₄ (98.2%) at low temperatures (100 °C).

Macroscopic, theoretical simulation and spectroscopic investigation on the immobilization mechanisms of Ni(II) at cryptomelane/water interfaces

In the present study, the macroscopic sorption behaviors and microscopic immobilization mechanisms of Ni(II) at cryptomelane/water interfaces were explored using the combination of batch sorption technique, desorption procedure, theoretical simulation, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS) analyses. The good simulation of the pseudo-second-order model on the sorption kinetics data suggests a driving force of chemical sorption rather than mass transport or physical interaction. The sorption trends and uptake mechanisms are obviously related to the solution pH, with cation exchange or outer-sphere surface complexation at an acidic pH of 4.0, inner-sphere surface complexation in both the edge-shared (ES) and double corner-shared (DCS) modes at a neutral pH of 7.0, and precipitation of α-Ni(OH)₂(s) phase at a highly alkaline pH of 10.0. The gradual increase of Ni(II) sorption amount with solution temperature rising from 293 K to 333 K is consistent with the increased ratio of the weak DCS configuration. The research findings herein can help us better understand the migration and transformation trends of Ni(II) in the manganese mineral-riched aquatic environment.