Preliminary study on removing Cs⁺/Sr²⁺ by activated porous calcium silicate-A by-product from high-alumina fly ash recycling industry

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.

Superadsorbents for Strontium and Cesium Removal Enriched in Amidoxime by a Homo-IPN Strategy Connected with Porous Silica Texture

In light of the fact that two with good compatibility are better than one, the homo-interpenetrating polymer network (IPN) strategy was used in this work to design novel amidoxime (AOX)-interpenetrating networks into porous silica (PSi) with the final aim to enhance the sorption performances of composite sorbents toward Cs⁺ and Sr²⁺. To achieve this goal, first, a homo-IPN of poly(acrylonitrile) (PAN) was constructed inside the channels of two kinds of porous silica, one mesoporous (PSi1) and one macroporous (PSi2), the textural properties of silica being exploited in controlling the sorption performances of the composites. The novel composites were fully characterized by thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and the nitrogen sorption/desorption isotherms (Brunauer-Emmett-Teller (BET) analysis). The sorption properties of the PSi1/AOX and PSi2/AOX composite sorbents for Sr²⁺ and Cs⁺ were investigated in the batch mode to determine the effect of solution pH, contact time, initial metal ion concentration, temperature, and the presence of competitive ions on the adsorption performances. The fast kinetics of sorption was supported by the fact that ∼80% of Sr²⁺ and ∼65% of Cs⁺ were adsorbed in the first 30 min, the kinetic data being better described by the pseudo-second-order kinetic model. The experimental isotherms were well fitted by the Langmuir and Sips isotherm models. The superadsorption of Sr²⁺ and Cs⁺ is demonstrated by the values of the maximum sorption capacity of the best sorbent constructed with mesoporous silica (PSi1/IPN-AOX), which were 344.23 mg Cs⁺/g and 360.23 mg Sr²⁺/g. The sorption process was spontaneous and endothermic for both metal ions. The presence of interfering cations (Na⁺, K⁺, Ca²⁺, and Mg²⁺), at a concentration of 10^-2 M, only slightly influenced the sorption capacity for the main cation. The composite sorbents were still highly efficient after five sorption/desorption cycles.

Amidoxime Functionalization of Algal/Polyethyleneimine Beads for the Sorption of Sr(II) from Aqueous Solutions

There is a need for developing new sorbents that incorporate renewable resources for the treatment of metal-containing solutions. Algal-polyethyleneimine beads (APEI) (reinforced with alginate) are functionalized by grafting amidoxime groups (AO-APEI). Physicochemical characteristics of the new material are characterized using FTIR, XPS, TGA, SEM, SEM-EDX, and BET. AO-APEI beads are tested for the recovery of Sr(II) from synthetic solutions after pH optimization (≈ pH 6). Uptake kinetics is fast (equilibrium ≈ 60-90 min). Sorption isotherm (fitted by the Langmuir equation) shows remarkable sorption capacity (≈ 189 mg Sr g-1). Sr(II) is desorbed using 0.2 M HCl/0.5 M CaCl2 solution; sorbent recycling over five cycles shows high stability in terms of sorption/desorption performances. The presence of competitor cations is studied in relation to the pH; the selectivity for Sr(II) is correlated to the softness parameter. Finally, the recovery of Sr(II) is carried out in complex solutions (seawater samples): AO-APEI is remarkably selective over highly concentrated metal cations such as Na(I), K(I), Mg(II), and Ca(II), with weaker selectivity over B(I) and As(V). AO-APEI appears to be a promising material for selective recovery of strontium from complex solutions (including seawater).