With the fast advancement of human modernization and rapid development of social economy, traditional energy consumption has been enormously increased and climate change has therefore become a very challenging issue for the human being. The development of modern industry, especially the chemical industry, has brought not only convenience to people, but also unprecedented destruction to the ecological environment closely related to human life. Energy and environmental issues have become a global challenge for us today. In order to better deal with the challenges and protect our living homeland, the majority of researchers are constantly seeking and exploring new materials and technologies which are environmentally friendly and can be used efficiently, aiming to solve increasingly serious environmental problems. In current stage, environmental materials and technologies have received ever-increasing attention and are developing rapidly.

Environmental materials, as the name implies, are materials designed and developed for environmental issues. The key issue of environmental problems is environmental pollution. At present, the widely concerned pollutants include gas pollutants, persistent organic pollutants (POPs), and heavy metals. At the same time, with drastic development of nuclear energy industry in the past two decades in China, radioactive pollutants have also received increasing attention. Separation and removal of these pollutants from environment by certain means is an effective and common method for environmental pollution control. Therefore, the key for solving environmental problems is to develop materials and technologies that can effectively remove environmental pollutants. Plenty of versatile materials for specific contaminant removals have been reported over the past few decades. These materials come in a wide variety of functions, with varying structures and performance. Most concerned materials include traditional molecular sieves^[1], mineral materials^[2], carbon materials such as graphene and carbon nanotubes^[3], polymer based materials such as resins^[4], metal organic frameworks (MOFs)^[5] and covalent organic frameworks (COFs)^[6]. Among these materials, inorganic materials have broad application prospects in the removal and separation of environmental pollutants due to their stability, low cost and environmental friendliness. In particular, inorganic nanoporous materials have become favorable in recent years. The nanometer size makes nanomaterials not only have quantum size effect, but also possess larger specific surface area and more surface atoms compared to other common materials, thus exhibiting stronger adsorption ability and better dispersibility in aqueous solution. In addition, the porosity of materials greatly enhances the specific surface area and correspondingly increases the contact opportunity between the material and contaminant. Meanwhile, it also improves the diffusion and transportation of contaminants inside the material, elevating the adsorption kinetics. Metal nanomaterials, metal oxide nanomaterials, mineral materials, etc. are typical representatives of inorganic nanomaterial family.

Based on the published works, many efforts in the field of inorganic environmental materials focused on improving the removal efficiency and selectivity toward one or more target pollutants. Inorganic materials have higher stability than organic materials, but possess low removal capacity and poor selectivity, due to lacking of active functional groups on the surface. Functionalization of inorganic materials should be a reasonable approach to overcome this drawback. It is well known that functional groups with strong binding or coordination ability to the target contaminant decorated on the surface of material by physical or chemical means can greatly improve the adsorption performance of inorganic materials^[7]. Moreover, besides modifying the specific recognition group on the surface of the material^[8], adjusting the pore structure of material and physically screening contaminants by the size effect^[9] are always common and effective. It is also promising to combine size effects, bonding and electrostatic interactions by means of molecular imprinting or composition^[10]. Besides, developing inorganic environmental materials used under harsh conditions^[11], such as high acid, high alkali, and high temperature, is becoming a research hot topic in recent years.

In all, after decades of development, researches on inorganic environmental materials have made significant progress, whereas most of materials are still not satisfactory for industrial applications. In order to better solve the increasingly serious environmental problems, it is still necessary for the material researchers to overcome difficulties and make continuous efforts.

For the future advanced nuclear fuel cycle system, pyrochemical technology based on molten salt electrolysis is generally considered to be one of the most promising and reliable reprocessing technologies. The salt-containing waste generated in each step of the pyrochemical process needs to be converted into a ceramic waste form, which can be stably disposed in a long term manner in deep geological repository. This is of pivotal importance for the scale-up and industrialization of molten salt electrolysis based pyrochemical processing. In this review, the current research progresses of ceramic solidification technology in main nuclear energy countries with respect to salt-containing wastes were summarized and reviewed, with emphasis on ceramic solidifications of salt-containing wastes from electro-reduction process in LiCl-based salt and electro-refining process in LiCl-KCl salt. In addition, future perspectives in this field are also given.

Nanoscale zero-valent iron (NZVI) has been widely applied to eliminate radionuclide U(VI). However, poor stability and low efficiency restrict the employment of pure NZVI. In this study, surface passivation and dispersion technology were employed together. Ca-Mg-Al layered double hydroxide supported sulfide NZVI (CMAL-SNZVI) was synthesized and applied for U(VI) elimination. Macroscopic and microscopic investigations demonstrate the outstanding physicochemical properties, high reactivity and excellent performance for U(VI) removal. The reaction process can be achieved equilibrium within 2 h and the maximum elimination capacity reaches 175.7 mg·g ^-1. The removal mechanism of U(VI) on CMAL-SNZVI is the synergistic effect between adsorption and reduction, through which U(VI) can be adsorbed by CMAL base and the SNZVI surface via inner-sphere surface complexation, U(VI) can be reduced into less toxic and insoluble U(IV) by Fe ⁰ inner core. Overall, the synthetization of CMAL-SNZVI can lead a new direction of NZVI modification. In the meantime, the outstanding performance of U(VI) removal indicate the potential of CMAL-SNZVI as excellent material for environment remediation.

With the development of nuclear power, radioactive pollutants discharge into the environment and then contaminate soil and water resources. Nanoscale zero-valent iron (nZVI) materials are widely used in water remediation due to their strong reducibility and high removal efficiency. A carbon-based zero-valent iron material (Fe-CB) was prepared in this work. Fe-CB was fabricated using sodium alginate (SA) as a carbon source via one-step carbothermic method and then applied to eliminate U(Ⅵ) from aqueous solution. Its mechanism and adsorption properties of Fe-CB and U(VI) were studied by spectroscopic analyses and macroscopic experiments. The results illustrated that Fe-CB possessed of ample functional groups (such as -OH and -COOH) and high BET surface area, which made up for the dispersibility and low removal efficiency of nanoscale zero-valent iron (nZVI). The removal of U(VI) by Fe-CB achieved equilibrium in 3 h and the maximum sorption capacity was 77.3 mg·g ^-1 at 298 K. XPS analyses indicated that the U(Ⅵ) removal by Fe-CB was a synergistic effect of reductive adsorptive processes. Adsorption process resulted from surface complexation and the reduction process was dominated by U(VI) reduction to U(IV) by nZVI. The results show that Fe-CB can be used as an inexpensive and highly efficient pollutant scavenger, which has great potential for environment pollution management.

Hydrothermal carbon adsorption materials possess the advantages of simple preparation process, mild synthesis conditions and easy surface modification. In this UO₂ ²⁺speciation as a function of CO₃ ^2- concentration, soluble starch used as carbon source, acrylonitrile was grafted onto starch molecule through ring opening under the catalysis of cerium ammonium nitrate. Subsequently, amidoxime hydrothermal carbon spheres (AO-HTC) were successfully synthesized by hydrothermal reaction and hydroxylamine hydrochloride reduction. Meanwhile, static and dynamic adsorption experiments were performed to investigate the effects of solution pH, carbonate and calcium ion concentration on the adsorption performance of AO-HTC for uranium. And the dynamic adsorption process of AO-HTC for uranium was also studied by Yoon-Nelson and Thomas models. The results show that the adsorption capacity of AO-HTC, the volume of penetration point as well as saturation point in the penetration curve also decreases gradually with the increase of pH, carbonate concentration and calcium concentration. The maximum adsorption capacity (q_o) and the required time (τ) of adsorbate through 50% of 5% AO-HTC column are several times higher than that of pure soil column. Therefore, the research highlights that AO-HTC would act as an excellent permeable-reactive barriers (PRB) medium and expected to remediate uranium-contaminated soil and groundwater.

¹³⁷Cs is one of the most intractable β-emitters which is commonly generated from nuclear weapons test and nuclear power station. Due to the nature of high solubility and mobility, the effective sequestration of ¹³⁷Cs ⁺ from radioactive waste solution is considered as a long-term challenge. In this work, a two-dimensional layered anion framework material (SZ-6) was synthesized through conventional solvothermal reaction and the Cs ⁺ removal properties were systematically investigated. Single Crystal X-ray Diffraction (SCXRD) analysis revealed that SZ-6 adopts layer packed structure with large tetramethylammonium cations loaded between the layers which is greatly beneficial to cation exchange process. Powder X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM) confirmed the material with high purity and excellent hydrolytic stability. Batch experiments were used to investigate the adsorption behavior towards Cs ⁺ in aqueous solutions. The adsorption kinetics of SZ-6 could be achieved within 5 min, which is currently one of the fastest sorbents for the removal of Cs ⁺. Meanwhile, SZ-6 exhibits superior decontamination capability over a wide pH range from 4 to 12. Furthermore, it possesses marked selectivity in the presence of large excess of Na ⁺, K ⁺, Ca ²⁺ competing cations.

Reduction of soluble U(VI) to insoluble U(IV) oxide is an effective approach to control uranium contamination. Three-dimensional (3D) macroporous g-C₃N₄ photocatalyst with interconnected porous was prepared by thermal polymerization and template etching using self-assembly of SiO₂ nanosphere as the template. The material was then applied to adsorption-photocatalytic reduction of U(VI). Characterization results showed that the 3D macroporous g-C₃N₄ photocatalyst presented a well-defined interconnected macroporous architecture and numerous nanopores existed on the well-defined macroporous skeleton. 3D macroporous g-C₃N₄ also had a significant increase in specific surface area which was beneficial to the absorption of visible light. Adsorption results showed that the maximum adsorption capacity of U(VI) on 3D macroporous g-C₃N₄ was ~30.5 mg/g, which was more than ~1.83 times higher than that of bulk g-C₃N₄. The adsorption isotherm matched well with the Langumuir equation. Photocatalytic reduction experiments showed that the 3D macroporous g-C₃N₄ had high photocatalytic activity and good stability with the reduction rate constant of 0.0142 min ^-1, which was ~4.9 times higher than bulk g-C₃N₄ (~0.0024 min ^-1). As the sorption-photocatalytic performance of the sample is excellent, 3D macroporous g-C₃N₄ is a high efficient visible-light-responsive photocatalyst for the removal of U(VI) from radioactive wastewater.