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Decontamination of the toxic selenium compound, selenite (Se(IV)) and selenate (Se(VI)), from wastewater is imperative for environmental protection. Efficient approaches to remove Se(IV) and Se(VI) are in urgent needs. In this work, an accessible adsorbent Fe–OOH–bent was prepared and applied for the removal of Se(IV) and Se(VI) from wastewater. The batch experimental results demonstrate that Fe–OOH–bent exhibits high adsorption capacities of 5.01 × 10−4 and 2.28 × 10−4 mol/g for Se(IV) and Se(VI) respectively, which are higher than most of the reported bentonite based materials, especially in the case of Se(VI). Moreover, the Fe–OOH–bent displayed superior selectivity towards Se(IV) and Se(VI) even in the presence of excess competitive anions (Cl−, HCO3−, NO3−, SO42− and PO43−) and HA with concentrations of 1000 times higher than Se(IV) and Se(VI). By evaluating the adsorption ratio of Se(IV) and Se(VI), the reusability of Fe–OOH–bent was great through five adsorption-desorption cycles. For practical application, the column experiments were performed with simulated wastewater samples. The breakthrough and eluting curves of Se(IV) and Se(VI) were investigated through the columns packed with Fe–OOH–bent, and the results show that Se(IV) and Se(VI) can be successfully separated and recovered using 0.1 mol/L Na2SO4 (pH = 9.0) and 0.1 mol/L Na3PO4 (pH = 9.0), respectively. Our work provides a new approach for fractional separation as well as the recovery of Se(IV) and Se(VI) from wastewater. [ABSTRACT FROM AUTHOR]

The application for montmorillonite to deal with toxic metals (including radionuclides) becomes interesting based on its excellent physicochemical properties. In this work, the thermal activation method was utilized to pre-treat montmorillonite before use. The sample was characterized by FTIR, XRD, zeta potential, BET and potentiometric titration to clarify the variation of montmorillonite before and after thermal activation. Batch techniques were used to investigate the sorption ability of montmorillonite to U(VI) under different environmental conditions. The electrical double layer model has been introduced to describe the variation of pre-treated sample as well as the principal mechanism for U(VI) uptake. In addition, the irradiation effects of samples for U(VI) sorption was also investigated. Based on the optimum condition for U(VI) uptake, it can be deduced that the thermally activated montmorillonite has potential application for the removal of U(VI) in wastewater. [ABSTRACT FROM AUTHOR]

• An efficient and economic HDPy-bent material was synthesized and applied for removing 99Tc from contaminated water. 99Tc is one of the critical fission products in the treatment of wastewater and the nuclear waste repository due to its long half-life (t 1/2 = 2.13 × 105 y), high fission yield (~6%), and high mobility in the environment. The development of highly-efficient, low-cost and easily available materials that can rapidly and selectively remove 99Tc is of great significance, but remains a challenge. In this work, bentonite-based materials (HDPy-bent) were obtained through modifying bentonite with hexadecylpyridinium (HDPy) and applied for the remove of TcO 4 − as well as its surrogate ReO 4 −. The structure of HDPy-bent (e.g., the values of d 001) was evaluated and the maximum loading amount of HDPy on bentonite was found to be 200% CEC. The loaded HDPy+ might replace exchangeable cations in the inter-layer space of bentonite. Batch experiment results show that HDPy-bent could quantitatively remove TcO 4 − from aqueous solution within 3 min. The distribution coefficient (K d) of TcO 4 − in this material is up to 2.1 × 105 mL/g, which is significantly higher than most of the previously tested inorganic adsorbent materials. More importantly, HDPy-bent can selectively remove TcO 4 − in the presence of large excess (80,000 times) of competitive anions (NO 3 –, SO 4 2−, CO 3 2−, PO 4 3− and Cl−). This work demonstrates that the HDPy-bentonite is a low cost, and effective adsorbent for removing 99Tc from contaminated water. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel extractant resin DtBuCH18C6@CG-71 was successfully prepared with simple and low-cost method. • DtBuCH18C6@CG-71 exhibited remarkable separation ability of Sr(II) even in high concentration HNO 3 (3–12 mol/L). • DtBuCH18C6@CG-71 possessed great acid, irradiation and thermal resistance stability. • DtBuCH18C6@CG-71 can adeptly sequesters and recovers Sr(II) from wastewater via an automated separation system. Effective removal of radioactive 90Sr is crucial for both management of spent nuclear fuel and recovery of radioactive strontium resources, while it's still a great challenge due to the presence of high acid levels and intense radiation. Herein, a novel porous resin (DtBuCH18C6@CG-71) were synthesized by introducing 4′,4″(5″)-di- tert -butyldicyclohexano-18-crown-6 onto CG-71 resin using vacuum impregnation. The DtBuCH18C6@CG-71 resin maintains superior adsorption abilities in extreme conditions, including high acid resistance (3–12 mol/L HNO 3), substantial γ-irradiation (200 kGy 60Co), and elevated temperatures (50–100 ℃). Impressively, even when exposed to a high concentration of matrix ions (59 elemental ions), the Sr(II) adsorption ratio onto DtBuCH18C6@CG-71 resin remains near 100 % even in highly acidic condition, which performance outpaces most of commercial resins. Dynamic column tests using an automated separation system further confirmed the superior ability of DtBuCH18C6@CG-71 in term of extracting Sr(II) from wastewater. Given its impressive features, cost-effectiveness, and scalability, DtBuCH18C6@CG-71 resin holds promising potential for 90Sr disposal in nuclear wastewater. [ABSTRACT FROM AUTHOR]

99Tc primarily exists high mobility in the natural aqueous environment due to its extremely high solubility and non-complexing features, which can easily cause radioactive pollution. We herein report a general strategy for constructing a novel resin (SiPAN-PEI) with multiple positive charges nitrogen, exhibiting ultrafast adsorption kinetics (< 3 min), superior adsorption capacities (463.96 mg g−1), and excellent selectivity in the presence of excess competitive anions, which exceed those of most commercial resins. Moreover, based on impressive structure stability in extreme conditions, SiPAN-PEI can still maintain superior adsorption abilities after suffering irradiation, calcination, and immersion in strong acid. In addition, the separation performance kept excellently after five loading-washing-eluting cycles and the total adsorption ratio can still reach 97 %. Outstandingly, SiPAN-PEI can remove most of ReO 4 - from simulated nuclear wastewater through a sequential injection automatic separation system and can reduce the concentration of ReO 4 - to the maximum concentration standard set by the World Health Organization (WHO) in a short time. Leveraging density functional theory calculations and other characteristics clearly elucidated adsorption mechanism of anion-exchange between Cl- and TcO 4 -/ReO 4 -. In terms of superior adsorption property, SiPAN-PEI is demonstrated to be a pretty candidate for 99Tc elimination from wastewater. [Display omitted] • A novel resin SiPAN-PEI was successfully synthesized for selective capture of 99Tc. • SiPAN-PEI exhibited excellent adsorption ability of 99Tc in harsh conditions. • Multiple positive charge nitrogen plays a critical role in capture of 99Tc. • SiPAN-PEI demonstrated efficiency capture of 99Tc in simulated wastewater. [ABSTRACT FROM AUTHOR]

Finding an approach for pretreatment of radionuclides from contaminated water are interesting topics of research. In present work, the ZSM-5 molecular sieve was characterized with different techniques such as zeta potential, SEM, FT-IR and XRD to clarify the surface properties of sample and applied as a sorbent to concentrate and recover Cs(I) from aqueous solution. The effect of environmental conditions such as contact time, ionic strength, content of sorbent and solution pH on Cs(I) uptake were optimized using batch techniques. Different kinetic and isotherm models were utilized to evaluate the experimental data and the correlation parameters were obtained. Based on the sorption/desorption experiment, it can be deduced that the ZSM-5 molecular sieve has potential application for the rapid and quantitative recovery of radiocesium from wastewater. [ABSTRACT FROM AUTHOR]

Efficient and cost-effective removal of radioactive iodine anions from contaminated water has become a crucial task and a great challenge for waste treatment and environmental remediation. Herein, we present hexadecylpyridinium chloride monohydrate modified bentonite (HDPy-bent) for the efficient and selective removal of iodine anions (I− and IO 3 −) from contaminated water. Batch experiments showed that HDPy-bent could remove more than 95% of I− and IO 3 − within 10 min, and had maximum I− and IO 3 − adsorption capacities of 80.0 and 50.2 mg/g, respectively. Competitive experiments indicated that HDPy-bent exhibited excellent I− and IO 3 − selectivity in the excessive presence of common concomitant anions including PO 4 3−, SO 4 2−, HCO 3 −, NO 3 −, Cl− (maximum mole ratio of anions vs iodine anions was ∼50,000). An anion exchange mechanism was proposed for the selective adsorption of iodine anions. Optimal adsorption structure of HDPy+/I− (IO 3 −) at atomic level and driving forces of the I− (IO 3 −) adsorption were calculated by density functional theory (DFT) simulations. Moreover, the good durability and reusability of the HDPy-bent has been demonstrated with 5 adsorption-desorption cycles. Dynamic column experiment also demonstrated that HDPy-bent exhibited excellent removal and fractional recovery capabilities towards I− and IO 3 − from simulated groundwater and environmental water samples. In conclusion, this work presents a promising adsorbent material for the decontamination of radioactive iodine anions from wastewater on a large scale. [Display omitted] • HDPy-bent showed excellent adsorption abilities for iodide and iodate. • Anions exchange mechanism was confirmed by batch experiments and DFT simulations. • The pyridine N was the intrinsic active site of the modified bentonite. • HDPy-bent was efficient for removing radioiodine anions from wastewater. [ABSTRACT FROM AUTHOR]