Construction of a Porous Zwitterionic Polyimidazole Resin for the Elimination of Technetium in Acidic Environments

Due to the complex type of coexisting ions, remarkable acidity, and high radioactivity, efficient and sustainable methods for the removal of pertechnetate (99TcO4-) from acidic nuclear waste streams have attracted much attention. Herein, a porous highly polymeric zwitterionic resin (PDVBVIM1.5SO3) was synthesized by installing sulfobetaine zwitterionic units in the polymeric imidazole resin to achieve the purpose of balancing the hydrophilicity and hydrophobicity of the resin structure and improving the reaction kinetics and ion selectivity of the resin at the same time for perrhenate (ReO4-)/99TcO4- removal from acidic solutions. The results demonstrate that PDVBVIM1.5SO3 exhibits fast adsorption kinetics, superior adsorption capacity, and excellent selectivity in the presence of a variety of 1000-fold competing anions. The rapid elimination of ReO4- can be achieved even in 1 mol L-1 HNO3. Importantly, when subject to acid soaking, calcination procedure, and high doses of ionizing radiation, PDVBVIM1.5SO3 maintained its structural integrity and outstanding performance. Additionally, PDVBVIM1.5SO3 displayed outstanding adsorption efficiency toward a simulated Hanford low-activity waste stream with ReO4-. This work demonstrates that achieving a balance between hydrophobicity and hydrophilicity in an exchange resin is of great significance for enhancing the selection and removal of TcO4-/ReO4-, and PDVBVIM1.5SO3 resin could be an excellent acid nuclear waste-adsorbing material candidate.

Enhanced removal of radioactive iodine anions from wastewater using modified bentonite: Experimental and theoretical study

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 IO₃^-) from contaminated water. Batch experiments showed that HDPy-bent could remove more than 95% of I^- and IO₃^- within 10 min, and had maximum I^- and IO₃^- adsorption capacities of 80.0 and 50.2 mg/g, respectively. Competitive experiments indicated that HDPy-bent exhibited excellent I^- and IO₃^- selectivity in the excessive presence of common concomitant anions including PO₄^3-, SO₄^2-, HCO₃^-, NO₃^-, 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^- (IO₃^-) at atomic level and driving forces of the I^- (IO₃^-) 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 IO₃^- 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.

Investigation on the efficient separation and recovery of Se(IV) and Se(VI) from wastewater using Fe–OOH–bent

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 −, SO4 2− and PO4 3−) 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.