Separation of cesium from wastewater with copper hexacyanoferrate film in an electrochemical system driven by microbial fuel cells

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.

Constructing porous ZnFC-PA/PSF composite spheres for highly efficient Cs+ removal

Radioisotope leaking from nuclear waste has become an intractable problem due to its gamma radiation and strong water solubility. In this work, a novel porous ZnFC-PA/PSF composite sphere was fabricated by immobilization of ferrocyanides modified zinc phytate into polysulfone (PSF) substrate for the treatment of Cs-contaminated water. The maximum adsorption capacity of ZnFC-PA/PSF was 305.38 mg/g, and the removal efficiency of Cs+ was reached 94.27% within 2 hr. The ZnFC-PA/PSF presented favorable stability with negligible dissolution loss of Zn2+ and Fe2+ (< 2%). The ZnFC-PA/PSF achieved high-selectivity towards Cs+ (Kd = 2.24×104 mL/g) even in actual geothermal water. The adsorption mechanism was inferred to be the ion-exchange between Cs+ and K+. What's more, ZnFC-PA/PSF worked well in the fixed-bed adsorption (E = 91.92%), indicating the application potential for the hazardous Cs+ removal from wastewater.

Decontamination of radioactive cesium-contaminated soil/concrete with washing and washing supernatant- critical review

We reviewed washing of radioactive Cs-contaminated concrete and soil based on the fate of Cs in concrete and soil, including sorption materials for treatment of supernatant solution. In non-aged cement materials (the calcium silicate hydration (C-S-H) phase), it was possible to decontaminate Cs using ion exchange with monovalent cations, such as NH₄⁺. The clay components in the soil and aggregates were important factors in optimization of the efficiency and mechanism for Cs decontamination with washing solution. The parameters (reagent component, pH, and temperature) of the washing solution should be determined considering soil mineral type (here, weathered biotite (WB) with vermiculite), since monovalent cations such as NH₄⁺ and K⁺ can inhibit Cs decontamination due to collapse of the hydrated and expanded interlayer regions with cation exchange. In this case, hydrothermal treatment or H₂O₂ dosing was necessary to expand the collapsed interlayer region for Cs removal by washing with cation exchange or organic acids. Acid and a chelating agent significantly enhanced Cs-release with dissolution of the adsorbent layer containing iron and aluminum oxides. The important characteristics of important and emerging sorption materials for treatment of the radioactive Cs-contaminated supernatant after washing treatment are discussed. Sorbents for treatment of washing supernatant are divided in to two main categories. Clay minerals, metal hexacyanoferrates, and ammonium molybdophosphates are discussed in the inorganic class of materials. Hypercrosslinked polymers, supramolecular sorbents, carbon nanotubes, and graphene oxide are covered in the carbon-based sorbents for Cs removal from water.

Electrochemical synthesis of EuVO4 for the adsorption of U(VI): Performance and mechanism

The efficient removal of uranium from aqueous solution remains of great challenge in securing water environment safety. In this paper, we reported a high temperature electrochemical method for the preparation of EuVO₄ with different morphologies from rare earth oxides and vanadate, which solved the problems of rare earth and vanadium recovery. The effects of pH, ionic strength, contact time, initial concentration and reaction temperature on the adsorption of U(VI) by prepared adsorbent were studied by static batch experiments. When the concentration of U(VI) standard is 100 mg g^-1, the maximum adsorption capacity of EuVO₄ is 276.16 mg g^-1. The adsorption mechanism was elucidated with zeta potential and XPS: 1) negatively charged EuVO₄ attracted UO₂²⁺ by electrostatic attraction; 2) exposed Eu, V, and O atoms complexed with U(VI) through coordination; 3) the hybrid of Eu was complex, which accommodated different electrons to interact. In the multi-ion system with Al³⁺, Zn²⁺, Cu²⁺, Ni²⁺, Cr²⁺ and Mn²⁺, EuVO₄ also showed good selective adsorption properties for U(VI). Five adsorption and desorption cycle experiments demonstrated that EuVO₄ possessed good renewable performance.

Highly ordered macroporous silica dioxide framework embedded with supramolecular as robust recognition agent for removal of cesium

Owning to highly mechanical strength and non-interference effectivity, silica dioxide is often explored as a stable supporter commonly with mesopore. It is known that a macroporous framework has larger mass transfer channel, possibly beneficial to adsorption process. Herein highly ordered macroporous silica dioxide framework (homogeneous pore size of 194.20 nm) was synthesized and embedded with supramolecular (CC/OMS). Cs cation adsorption onto CC/OMS was explored under different pH (presence or absence of humic acid), initial cesium concentration, shaking time, competing ions. The robust cesium uptake capacity demonstrated by a theory adsorption amount of 150.01 mg/g highlighted unique CC/OMS properties combining large mass transfer channel and superior complex capacity of supramolecular. The adsorption was well fit with Langmuir and pseudo-second-order model. Sodium and potassium at a lower concentration showed little influence on cesium adsorption. The results demonstrated that CC/OMS was an alternative material for cesium capture from acidic aqueous solution.

Electrochemical recovery of cobalt using nanoparticles film of copper hexacyanoferrates from aqueous solution

Nanoparticles film of copper metal hexacyanoferrates (CuHCF) was fabricated to electrochemically separate Co²⁺ in aqueous solutions under various conditions such as applied potential, solution pHs, initial concentrations, contact time and coexisting ions. Results showed that the removal efficiency conducted in reduction potential was obviously higher than that in oxidation potential. The optimal pH for Co²⁺ adsorption occurred at 8.0. Coexisting ions studies revealed that Co²⁺ could be removed from aqueous solutions containing Li⁺, Cu²⁺ and Al³⁺. Considering that cobalt and lithium are the main metallic elements in LiCoO₂, the effect of different ionic strengths (IS) of LiNO₃ (0.5, 1, 2, 5, 10) on adsorption was further investigated. Results showed that IS of LiNO₃ had little impact on the removal efficiency of Co²⁺, which indicated the potential of selective recovery of cobalt from LiCoO₂ in spent lithium-ion batteries. X-ray energy-dispersion spectroscopy (EDS) confirmed that the Co²⁺ could be adsorbed effectively onto CuHCF film. The adsorption was well described by Langmuir isotherm and the maximum sorption capacity is 218.82 mg/g. The kinetic rate of Co²⁺ adsorption was rapid initially and attained equilibrium within 60 min, and the data well fitted the Redlich-Peterson and the Elovich model, implying a chemisorption dominated process.