Synthesis of novel nanomaterials and their application in efficient removal of radionuclides

With the development of nuclear energy, large amounts of radionuclides are inevitably released into the natural environment. It is necessary to eliminate radionuclides from wastewater for the protection of environment. Nanomaterials have been considered as the potential candidates for the effective and selective removal of radionuclides from aqueous solutions under complicated conditions because of their high specific surface area, large amounts of binding sites, abundant functional groups, pore-size controllable and easily surface modification. This review mainly summarized the recent studies for the synthesis, fabrication and surface modification of novel nanomaterials and their applications in the efficient elimination and solidification of radionuclides,and discussed the interaction mechanisms from batch experiments, spectroscopy analysis and theoretical calculations. The sorption capacities with other materials, advantages and disadvantages of different nanomaterials are compared, and at last the perspective of the novel nanomaterials is summarized.

Temperature-responsive alkaline aqueous biphasic system for radioactive wastewater treatment

The treatment of anionic ^(99)TcO_(4)^(-)in the waste tank with high alkalinity is still very challenging.In this work,a new temperature-responsive alkaline aqueous biphasic system(ABS)based on(tri-n–butyl)-ntetradecyl phosphonium chloride(P_(44414)Cl)was developed to remove radioactive ^(99)TcO_(4)^(-).The phase transition mechanism was studied by cloud point titration,small-angel X-ray scattering,dynamic light scattering,and molecular dynamic simulations.As the Na OH concentration or temperature increased,the P_(44414)^(+)micelle could grow and aggregate.This micelle showed a particularly high affinity toward ReO_(4)^(-)/^(99)TcO_(4)^(-)compared to other competing anions and could directly extract more than 98.6%of ^(99)TcO_(4)^(-)from simulated radioactive tank waste supernatant.Furthermore,the loaded ^(99)TcO_(4)^(-)could be easily stripped by using concentrated nitric acid rather than metal salt-based reductants.This work clearly demonstrates that the alkaline ABS is a promising separation system for solving the technetium problem in the alkaline waste tank.

A one-pot process based on P_(44414)Cl-HCl aqueous biphasic system for recovering rare earth elements from NdFeB permanent magnet

Recovering critical metals from secondary resources have attracted great interest recently.In this work,a green one-pot leaching-extraction process based on tributyl(tetradecyl)phosphonium chloride (P_(44414)Cl)aqueous biphasic system (ABS) was developed to efficiently recover rare earth elements (REEs) from Nd Fe B permanent magnet.The reaction process,phase separation mechanism,and operation conditions were thoroughly investigated.It is found that the P_(44414)Cl-HCl ABS showed strong extraction ability towards Fe (>99%) whereas only a few REEs (<10%) were extracted,leading to extremely high separation selectivity between Fe and REEs.The characterization results showed that the coordination differences of Fe and Nd in HCl were the main driving forces for such highly selective separation.The phase diagram of P_(44414)Cl-Nd Cl_(3)ABS indicated that the salting-out effect of Nd Cl_(3)was stronger than common chlorides.Due to the hydrophobic property of P_(44414)[Fe Cl_(4)]and salting-out effect of Nd Cl_(3),the P_(44414)Cl could directly form ABS at room temperature after dissolving practical roasted Nd Fe B samples without any other operations and reagents.REEs and Fe could be mutually separated in just one step.Compared with traditional liquid-liquid extraction or ABS separation,this recovery process is green and facile and shows great application prospects in the field of rare-earth recovery.

Chromate separation by selective crystallization

A new paradigm to remove toxic chromate anions from aqueous solution by crystallization of chromatewater clusters with imine-linked guanidinium cationic ligands is introduced.The guanidium-based cationic ligand was easily prepared through the imine condensation of an alde hyde and aminoguanidine hydrochloride.The cationic imine-linked guanidinium liga nd(BBIG-CI)showed a high re moval capacity(292.5 mg/g)in the solutions.Rapid decontamination of chromate anions from the wastewater by this cationic ligand was resulted from an instantaneous crystallization.The produced guanidium chromate salts have an extremely low solubility(Ksp,BBIG=8.19×10^9).Such superior removal performance of these mate rials was attributed to the cha rge-assisted hydrogen bonding between the cationic ligand and chromate-water hydrate anions,which was revealed by the single-crystal X-ray diffraction analysis and density functional theory(DFT)calculations.In addition,the succes s ful recove ry of the guanidium-based ligand makes it more attractive for real-world applications.