Excellent Acid Resistance Research Articles

Preparation of Zeolite A from Ion-Adsorbing Rare Earth Tailings for Selective Adsorption of Pb2+: An Innovative Approach to Waste Valorization

Ion-adsorbing rare earth tailings (IRETs) contain a large amount of clay minerals, which are a potential source of silicon and aluminum for the preparation of zeolite materials. The complexity of the tailings’ composition and the impurity composition are the main difficulties in the controllable preparation of zeolite. Herein, IRETs were treated by classification activation technology for the preparation of IRET-ZEO, which was used for the removal of heavy metal Pb2+ in water. A new method of resource utilization of ion-type rare earth tailings is realized by “treating waste with waste”. The results showed that the IRETs were classified and then thermally activated, and the optimal activation parameter was calcination at 850 °C for 1 h. The optimal NaOH concentration used in the crystallization process was 5 mol/L, with a crystallization time of 3 h and a crystallization temperature of 85 °C, and the crystallization product was zeolite A. The removal rate of the Pb2+ solution with an initial concentration of 100 mg/L was as high as 96.7% in an acidic solution with a pH value from 2 to 5.5. In particular, when the solution pH was higher than 4.2, the adsorption rate of Pb2+ was close to 100%. The IRET-ZEO showed a fast adsorption rate (5 min to reach adsorption equilibrium), a large adsorption capacity (378.35 mg/g), excellent acid resistance, and selectivity and regenerability for Pb2+. This work provides a new strategy for the green resource utilization of IRETs and the treatment of lead-containing wastewater.

Excellent acid resistance and MXene enhanced photothermal conversion of bilayered porous solar evaporator fabricated by palygorskite and pectin

Acidic wastewater comes from a wide range of sources in industrial process. The traditional treatment method of acidic wastewater is acid-base neutralization which consumes a lot of chemicals. In recent years, much attention has been paid to the treatment of wastewater through solar interfacial evaporation. However, many of the reported evaporators present challenges in terms of poor acid resistance and costly raw materials. In this article, the three-dimensional porous MXene/PPAL aerogel was prepared by directional freeze-drying using inexpensive Palygorskite (Pal) and renewable pectin, then a moderate amount of MXene was sprayed onto the aerogel surface to create a double-layer solar evaporator. The prepared evaporator exhibited great mechanical properties with a compressive strength of 0.85 MPa at 70 % strain, and high vapor rate of 1.5474 kg m−2 h−1 that equals 94.7 % photothermal conversion efficiency. Furthermore, photothermal conversion efficiency of the solar evaporator in 5 % H2SO4 solution (pH = 1) was 90.2 %, which was only slightly different from that in pure water. The results provided a new technology that easy recovery of acidic wastewater and reused treated water from industrial acidic wastewater through economical and efficient solar interfacial evaporation.

Thermal Vapor Deposition of a Hydrophobic and Gas-Permeable Membrane on Zirconium Phosphate Cation Exchanger: An Oral Sorbent for the Urea Removal of Kidney Failure.

An oral sorbent with high capacity for NH4+ is desirable in lowering the blood urea level and mitigating the dialysis burden for end-stage kidney disease (ESKD) patients. Zirconium phosphate (ZrP) is an amorphous cation ion exchanger with high NH4+ binding capacity as a sorbent material, but its selectivity to remove NH4+ is limited in the presence of other competing ions in water solution. We previously have developed a gas-permeable and hydrophobic perfluorocarbon coating on ZrP, which improves ZrP's NH4+ selectivity. However, the coating preparation procedure, a wet chemistry approach, is complicated and time-consuming, and more importantly, the large amount of usage of acetone poses a concern for the application of ZrP as an oral sorbent. In this study, we developed a solventless coating protocol that effectively coats ZrP with tetraethyl orthosilicate (TEOS) and 1H,1H,2H,2H-perfluorooctyltriethoxysilane (FOTS) via thermal vapor deposition (TVD) in a simplified manner. X-ray photoelectron spectroscopy (XPS) and contact angle measurements verify the two coatings are successfully deposited on the ZrP surface, and the coating condition was optimized based on an in vitro static binding study. The dynamic binding study of competing ions on Na-loaded ZrP with TVD coatings yields a maximum NH4+ removal (∼3.2 mequiv/g), which can be improved to ∼4.7 mequiv/g if H-loaded ZrP under the same coating condition is used in basic stock solutions. More importantly, both materials barely remove Ca2+ and show excellent acid resistance. The significant improvement in the NH4+ binding capacity and selectivity reported here establishes a highly promising surface modification approach to optimize oral sorbents for ESKD patients.

Lightweight hybrid fiber-reinforced sheet molding compound with enhanced mechanical properties and excellent acid resistance

Lightweight hybrid fiber-reinforced sheet molding compound with enhanced mechanical properties and excellent acid resistance

Fabrication of hydrophilic and durable Beta zeolite membranes for dehydration of fuel n-butanol by adjusting Al spatial distribution

Highly hydrophilic and durable Beta zeolite membranes with high aluminum (Al) spatial distribution were synthesized on inexpensive α-alumina supports via an organic template-free synthesis gel. In the absence of organic templates, the Al spatial distribution of Beta zeolite membrane crystal was regulated by the synthesis parameters such as the Al2O3/SiO2 ratio, alkalinity, H2O/SiO2 ratio and crystallization temperature, and the crystal morphology, Si/Al ratio and dehydration performance of the membrane could be further effectively controlled. Under optimal synthesis conditions, the prepared Beta zeolite membrane had an excellent separation factor of over 22,000 and a high permeation flux of 3.02 kg m−2 h−1 in the case of a 90 wt% n-butanol/water mixture at 75 °C. The high-performance Beta zeolite membrane was applied for continuous dehydration to obtain anhydrous n-butanol (99.9 wt%) from a 90 wt% n-butanol/water mixture. Furthermore, Beta zeolite membranes showed long-term acid stability in pervaporation dehydration of a 90 wt% n-butanol/water mixture with a pH value of approximately 2.0 at 75 °C for 192 h, indicating that these membranes by adjusting Al spatial distribution exhibited excellent hydrophilicity and acid resistance, which had a broad promising prospect of industrial applications for dehydration separation of acid-containing organic solvents.

Anti-fouling ampholytic polymer membrane with super-wetting surfaces for efficient oil-water emulsion separation

The development of highly efficient polymeric membranes with super-wetting surfaces (superhydrophilic/submerged superoleophobic) is one of the ideal options to achieve emulsified oily wastewater separation. However, this remains a challenging due to low fluxes and severe membrane contamination limitations. Here, we have demonstrated an ultra-hydrophilic, underwater super-oleophobic, highly anti-fouling and antibacterial (polydopamine/poly [2-(methacryloyloxy) ethyl] dimethyl- (3-sulfopropyl) ammonium hydroxide) PDA/PSBMA modified membrane by grafting amphoteric polymers via atom transfer radical polymerization (ATRP). Benefiting from PSBMA's superhydrophilicity and the unique adhesion of dopamine (DA), the PDA/PSBMA modified membrane shows superhydrophilic properties, superoleophobicity underwater, oil resistance, and fouling resistance. Meanwhile, PDA/PSBMA modified membrane reached a superb permeability to water as high as 5620 L·m−2·h−1·bar−1 and remarkable oil rejection rate of 98 % in separating diesel-in-water emulsions. Furthermore, the separating performance remained fairly constant over 10 emulsion filtration cycles. Besides, the PDA/PSBMA modified membranes have excellent acid and alkali resistance and antibacterial properties, showing its potential for oily wastewater purification. This work offers a simple and versatile strategy to fabricate superwetting efficient polymeric membranes to separate emulsified oily wastewater.

Chemically recyclable rosin-based polymers

The pursuit of next-generation sustainable polymers with chemical recyclability and resource renewability has become a priority in materials science. Rosin, a widely available renewable natural biomass, holds promise in this regard. In this study, dehydroabietic acid was incorporated into a cyclooctene monomer structure as pendant groups. This tailored monomer with low ring strain possesses the ability to efficiently undergo ring-opening metathesis polymerization (ROMP), resulting in the synthesis of rosin-based unsaturated polymers with a fully hydrocarbon backbone. The molecular weight of these polymers, ranging from 50 kDa to 160 kDa, can be easily modulated by varying the monomer-to-catalyst feeding ratio. Remarkably, these amorphous polymers exhibit exceptional thermostability, with a decomposition temperature exceeding 400 °C. This type of polymer exhibits excellent acid and alkali resistance within a pH range of 3 to 11. Upon exposure to Grubbs catalyst under mild conditions, these polymers undergo depolymerization back to the native monomer in a highly efficient manner, achieving a remarkable recovery ratio of approximately 95 %. It is evident that this innovative approach is not only relevant for the development of rosin-based polymers but also holds promise for informing the design of other renewable polymers with superior thermostability and enhanced chemical recyclability.

TiO2 modified basalt fiber cloth with superhydrophilicity and underwater superoleophobicity for oil-water separation

Titanium mesh, stainless steel mesh and other substrate materials for oil-water separation membranes have excellent acid and alkali resistance. However, the preparation process pollutes the environment and is costly. Therefore there is an urgent need for an economical and eco-friendly new material to replace them. Here, this research found that eco-friendly basalt fibers can replace them. In this work, superhydrophilic/underwater superoleophobic TiO2/basalt fiber cloths were prepared by solvothermal method. It has a contact angle of 0° for water in air and maximum 161° for n-hexadecane underwater. The oil-water separation efficiency was up to 99.75%, which indicated its efficient oil-water separation capability. The underwater n-hexadecane contact angle was 154° after immersing it in 6 mol of HCl and NaOH for 2 h respectively. This indicates that it has excellent acid and alkali resistance. And with titanium mesh, stainless steel mesh separation membrane acid and alkali resistance is not much different. However, the price is only one percent of titanium mesh. In addition, the softness of basalt fiber can be folded to enhance the pressure-bearing capacity. Therefore, this work provides a green, acid and alkali resistant, inexpensive new material for oil-water separation membranes, which has great potential in the field of oil-water separation.

Immobilization of pancreatin based on ultrasound-assisted polydopamine functionalized magnetic porous chitosan for the detoxification of ochratoxin A in wine

Ochratoxin A (OTA) is a mycotoxin that globally contaminates fruits and their products. Since OTA have a huge negative impact on health hazards and economic losses, it is imperative to establish an effective and safe strategy for detoxification. Here, pancreatin was immobilized on the surface of polydopamine functionalized magnetic porous chitosan (MPCTS@ PDA) for the degradation of OTA. Compared with free pancreatin, MPCTS@ PDA@ pancreatin displayed excellent thermal stability, acid resistance, storage stability and OTA detoxification in wine (>58%). Moreover, the MPCTS@ PDA@ pancreatin retained 43% initial activity after 8 reuse cycles. There was no significant change in the quality of wine after MPCTS@ PDA@ pancreatin treatment. Moreover, it did not exhibit cytotoxicity which facilitated its application in wine. These results demonstrated that MPCTS@ PDA@ pancreatin can be used as a highly effective biocatalysate for OTA detoxification in wine.

Robust and stable organic sulfonate sodium salt-coated superhydrophilic mesh for ultra-fast gravity-drive oil-water separation

Due to its special wetting behavior and high selectivity, super-wetting mesh is considered as an ideal candidate material for efficient separation of water/oil mixture. However, the oil-water separation mesh suffers from the problems of poor stability and durability, leading to the failure of the separation. In this paper, a robust and stable superhydrophobic/superhydrophilic copper mesh had been successfully prepared by decorating the copper mesh via the chemical grafting of the 3-thiol-propyl trimethoxysilane (KH590) and the subsequent reaction with 2-acrylamide-2-methylpropane-1-sulfonate sodium (AMPS). It showed that the KH590 condensation compound was tightly coated on the surface and the superhydrophobic copper mesh (SUCM) possessed excellent superhydrophobicity towards various liquid droplets with a WCA of higher 150° and a sliding angle lower 5°, while the superhydrophilic copper mesh (SICM) had promising anti-oil pollution property with WCA near 0°. The SUCM and SICM also had excellent acid and alkali resistance. The obtained SICM had preeminent separation efficiency higher 99% and extremely high permeability flux of 33,441 L·m−²·h−¹ for gravity-driven toluene-water separation, and possessed excellent recyclability even after 20 cycles. Moreover, the SICM could be used to separate the oil-water mixture of aqueous solution with different pH (pH=5/7/8) and aqueous sodium chloride solution with different concentrations (5%/25%/50%/saturated aqueous sodium chloride solution). In addition, the SICM had outstanding anti-abrasion mechanical stability. This work provided a simple and effective method for the preparation of special wettability materials with excellent acid/alkali resistance and mechanical stability, and promoted the practical application of oil/water separation mesh.

Synergistic enhancement of iodine capture from humid streams by microporosity and hydrophobicity of activated carbon fiber

Activated carbon fibers (ACF) are widely used to remove gaseous radioiodine produced during spent fuel reprocessing owing to their excellent adsorption properties. However, ACF's strong affinity for moisture tends to dominate, significantly reducing its ability to capture iodine in humid environments. The study used a one-step facile modification method of spray-deposited poly(divinylbenzene) (PDVB) nanoparticles on ACF to prepare hydrophobic activated carbon fiber (ACF-PDVB1.5). Compared to the initial ACF, the ACF-PDVB1.5 enhances the specific surface area to 1571 m2/g while maintaining abundant active sites, overcoming the disadvantage of pore reduction caused by traditional modification methods. More importantly, they also have excellent acid and alkali resistance and hydrophobicity (water contact angle 131.1°), with a preference for I2 pores (97 % microporosity). The iodine capture capacity of ACF PDVB 1.5 showed a significant increase compared to the initial ACF, as indicated by both static and dynamic adsorption tests. Notably, the dynamic iodine adsorption capacity of ACF-PDVB1.5 in a mixed iodine-water vapor stream at actual temperature (75 °C) and humid (50 % RH) conditions was 1847.69 mg/g, an increase of 55.47 % over the capacity of initial ACF (1188.71 mg/g). This work improves the overall I2 adsorption performance through hydrophobicity and pore size coordination.

Effect of B2O3 and Basic Oxides on Network Structure and Chemical Stability of Borosilicate Glass

Glass properties play crucial roles in ensuring the safety and reliability of electronic packaging. However, challenges, such as thermal expansion and resistance to acid corrosion, pose long-term service difficulties. This study investigated the impact of the microstructure on acid resistance by adjusting the glass composition. A glass material with excellent acid resistance was obtained by achieving a similar coefficient of thermal expansion to tantalum; it exhibited a weight loss rate of less than 0.03% when submerged in 38% sulfuric acid at 85 °C for 200 h. Theoretically, this glass can be used to seal wet Ta electrolytic capacitors. Differential scanning calorimetry (DSC) was used to analyze the glass transition temperature and thermal stability of borosilicate glasses. X-ray diffractometry (XRD), scanning electron microscopy (SEM), and Raman spectroscopy were used to study the microstructure of the amorphous phase of the borosilicate glass, which revealed a close relationship between the degree of network phase separation in the borosilicate glass and the degree of polymerization (isomorphic polyhedron value, IP) of the glass matrix. The IP value decreased from 3.82 to 1.98 with an increasing degree of phase separation. Boron transitions from [BO4] to [BO3] within the glass network structure with increasing boron oxide content, which diminishes the availability of free oxygen provided by alkaline oxide, resulting in a lower acid resistance. Notably, the glass exhibited optimal acid resistance at boron trioxide and mixed alkaline oxide contents of 15% and 6%, respectively. Raman experiments revealed how the distributions of various bridging oxygen atoms (Qn) affect the structural phase separation of the glass network. Additionally, Raman spectroscopy revealed the depolymerization of Q4 into Q3, thereby promoting high-temperature phase separation and highlighting the unique advantages of Raman spectroscopy for phase recognition.

Preparation of dense polysulfonamide acid-resistant composite membrane with high rejection based on polyethylene substrate

Polysulfoneamide (PSA) separation membranes show promising prospects for use in acidic wastewater treatment due to their outstanding acid stability. However, current PSA membranes have the disadvantages of low flux, poor NaCl rejection, and poor acid resistance of substrate. In this paper, a positively charged PSA membrane was successfully prepared by using polyethylene (PE) stretch membrane (usually used as a battery diaphragm) as the substrate, with polyethyleneimine (PEI) and naphthalene-1,3,6-trisulfonyl chloride (NTSC) as the monomers for interfacial polymerization. The acid-resistant membrane exhibits a dense structure with an average pore size of just 0.2844 nm. Consequently, the membrane exhibits superior rejection rates for monovalent and divalent metals (MgCl2 99.15 %, CaCl2 98.85 %, MgSO4 94.5 %, NaCl 93.27 %), while also maintaining satisfactory flux. The membrane has excellent acid resistance, and maintains its superior separation performance after being immersed in 20 wt% H2SO4 at a high temperature of 24 h.

Construction of superhydrophobic flexible polyurethane with dual nano-enhancement effect for solar-assisted high-viscosity oil cleanup and oil-water separation

Rapid and safe implementation of viscous crude oil cleanup is still a daunting challenge. Superhydrophobic materials are outstanding candidates for handling solvent spills, but are limited to recovering low viscosity oil and organic solvents. Hence, a polyurethane foam (PMRP-PU) integrating superelasticity, dual solar-responsive and fire resistance was fabricated by blending MXene and reduced graphene oxide (RGO) via self-foaming method. The surface temperature of the PMRP-PU reached 105 °C after simulated sunlight irradiation for 600 s. PMRP-PU had outstanding adsorption performance for low-viscosity oil and organic solvent (∼70.1 g/g) at room temperature, and the adsorption capacity of high-viscosity oil was also increased by 202.1 % compared with pure PU. Additionally, the adsorption capacity of PMRP-PU-3 remained at 92.7 % of the original level after 20 cycles of experiments. Excellent acid and alkali resistance and high temperature stability also greatly improved the environmental adaptability of the foam. Contrary to the flammability of pure PU, the peak heat release rate and total heat release of PMRP-PU-3 were decreased by 22.6 % and 25.2 %, respectively, and the melt dripping phenomenon disappeared during burning, exhibiting excellent fire safety. Briefly, this polyurethane foam can be repeatedly used for oil spill cleaning, and has a broad development prospect in the field of oil-water separation.

All-in-one treatment: Capture and immobilization of 137Cs by ultra-stable inorganic solid acid materials HMMoO6·nH2O (M = Ta, Nb)

Capture and immobilization of 137Cs is urgent for radioactive contamination remediation and spent fuel treatment. Herein, an effective all-in-one treatment method to simultaneously adsorb and immobilize Cs+ without high-temperature treatment is proposed. According to the strategy of incorporating high-valency metal ions into molybdates to increase the material stability and affinity towards radionuclides, layered HMMoO6·nH2O (M = Ta (1), Nb (2)) are prepared. Both materials exhibit excellent acid resistance (even 15 mol/L HNO3). They maintain remarkable adsorption capacity for Cs+ in 1 mol/L HNO3 solutions and can selectively capture Cs+ under excessive competitive ions. Furthermore, they show successful cleanup for actual 137Cs-liquid-wastes generated during industrial production. In particular, adsorbed Cs+ can be firmly immobilized in interlayer spaces of materials due to the highly stable anionic framework. The removal mechanism is attributed to ion exchange between Cs+ and interlayer H+ by multiple characterizations. Study of the structure-function relationship shows that the occurrence of Cs+ ion exchange is closely related to plate-like layered structure. This work develops an efficient all-in-one treatment method for capturing and immobilizing radiocesium by ultra-stable inorganic solid acid materials with low energy consumption and high safety for radionuclide remediation.

High solid content waterborne polyurethane with high foaming rate to artificial leather: Synthesis and characterization

A type of high solid content waterborne polyurethane (HSWPU) dispersions applied to foamed artificial leathers were designed and prepared by prepolymer method. The solid content of the waterborne polyurethane dispersions could reach 53 %, and the foaming ratio could reach an astonishing 2.50 by adjusting the parameters. The influence of synthesis parameters, including R value (molar ratio of -NCO/-OH), D value (hydrophilic group content), trimethylol propane (TMP) content (degree of crosslinking) and ethylenediamine (EDA) content (it was chain extender) on foaming ratio were investigated. Meanwhile, a series of properties of HSWPU dispersions, films and foamed artificial leathers were introduced in detail. The results demonstrated that R value, TMP content, D value and EDA content synergistically decided the foaming properties of HSWPU dispersions in three aspects: three-dimensional structure, surface tension and polarity, respectively. With optimized parameters of R = 2.0, TMP = 0.4 wt%, DMPA = 3.0 wt% and EDA = 60 wt%, the HSWPU dispersions had good appearance and stability, and the latex particles exhibited excellent water, acid and alkali resistance after films formation. The HSWPU dispersions with high foaming rate without collapsing in the foam-forming process and created uniformly bubble pores. In terms of application properties, the prepared foamed artificial leathers showed admirable air permeability and water vapor transmissions. All results distinctly demonstrate a feasible yet promising paradigm for applying the HSWPU on foamed artificial leathers had great potential applications.

Development of a novel and specialised cementitious matrix overlay for anode embedment in impressed current cathodic protection (ICCP) systems for reinforced concrete bridges

Impressed Current Cathodic Protection (ICCP) is a widely utilised method for safeguarding reinforced concrete (RC) structures, including bridges, in marine environments. However, certain ICCP systems encounter degradation of the backfill mortar caused by acid formation at the anode. The acid produced reacts with the anode backfill mortar, compromising the functioning of the cathodic protection system. Rectifying the acidification issue typically involves replacing the backfill mortar and, in some cases, even the anode when it is negatively impacted by acid attack. This paper presents, for the first time, a specialised sustainable cementitious matrix that exhibits excellent acid resistance, intended for use as the anode's backfill material in ICCP systems. The proposed mortar effectively mitigates the effects of acidification around the anode, significantly enhancing the durability of the mortar and, consequently, the service life of bridges equipped with ICCP systems. The mechanical and durability performance of the mortar in an acidic environment is evaluated through various tests, including gravimetric analysis, dimensional changes, diffusion depth, compressive strength, direct tension, slant shear, impact resistance, and interface integrity assessments. Additionally, scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques are employed to investigate the material's performance. Subsequently, the specialised mortar is applied to cover Mixed Metal Oxide (MMO) activated titanium mesh anodes of the ICCP system in a reinforced concrete bridge, while its performance is continuously monitored. The results demonstrate that the proposed mortar effectively eliminates acidification issues and improves the performance and longevity of ICCP systems in harsh marine environments.

Sustainable reutilization of ion-adsorbed rare earth tailings: Preparation of low-cost functionalized pigments

In order to alleviate the ecological pressure caused by rare earth tailings, this study focuses on the application of ion-adsorbed rare earth tailings in the preparation of functional pigments. By using mechanical grinding and high-temperature calcination, 33 new functionalized red pigments were successfully prepared by doping iron and lanthanum elements. X-ray diffraction (XRD), scanning electron microscopy (SEM), CIE 1976 color space system, and ultraviolet–visible–near-infrared spectrophotometer were used for characterization. The synthesized pigment exhibits a rich color range from light yellow to reddish brown. Compared with commercially available iron red pigments, it exhibits significantly enhanced near-infrared reflectance, excellent acid and alkali resistance, and strong thermal stability up to 900 °C. It is worth noting that pigment P-1-2-1 achieved the best red value (L* = 43.73, a* = +24.07, b* = +15.65) with a maximum near-infrared reflectance of 91 %. Therefore, the utilization of rare earth tailings as raw materials for the preparation of functional pigments has significant effects. This study provides valuable insights for the development of eco-friendly pigments, which not only helps alleviate the urban heat island effect but also promotes the sustainable utilization of rare earth tailing resources, contributing to the achievement of carbon neutrality goals.

Preparation of Environmentally Friendly BiVO4@SiO2 Encapsulated Yellow Pigment with Remarkable Thermal and Chemical Stability

The preparation of environmentally friendly inorganic encapsulated pigments with a bright color and sufficient stability provides an effective strategy for expanding their applications in plastic, paint, glass, and ceramic decoration. The challenges facing the use of such pigments include the formation of a dense protective coating with the required endurance, the relatively weak color of the encapsulated pigments, and the preferable inclusion particle size. Environmentally friendly BiVO4 is regarded as a very promising pigment for multiple coloring applications due to its brilliant yellow color with high saturation. However, its poor thermal and chemical stability greatly limit the application of BiVO4. Herein, we report a sol–gel method to synthesize inorganic BiVO4@SiO2 yellow pigment with a core–shell structure. By controlling the synthesis conditions, including the particle size and dispersion of BiVO4 and the calcination temperature, a BiVO4@SiO2 encapsulated pigment with excellent chromatic properties was achieved. The obtained environmentally friendly BiVO4@SiO2 pigment with encapsulation modification has a comparable color-rendering performance to BiVO4, and it has a high thermal stability at 700 °C, excellent acid resistance, and good compatibility in plastics. The present research is expected to expand the application of yellow BiVO4 pigment in harsh environments.

Selective Separation of Zr(IV) from Simulated High-Level Liquid Waste by Mesoporous Silica.

The efficient separation of Zr(IV) ions from strong acidic and radioactive solutions is a significant challenge, especially in the context of the aqueous reprocessing of nuclear fuels. The complexity of such solutions, which are often characterized by high acidity and the presence of radioactive elements, poses formidable challenges for separation processes. Herein, several mesoporous silicas (HMS, MCM-41, KIT-6, and SiO2-70 Å) with excellent acid and radiation resistance properties were employed as sorbents to remove Zr(IV) ions from simulated high-level liquid waste. The batch experiments were designed to investigate the influence of adsorption time, HNO3 concentration, initial Zr(IV) concentration, adsorbent dosage, and temperature on the adsorption behavior of Zr(IV). The results indicate that the adsorption equilibrium time of mesoporous silica materials was approximately 8 h, and all the adsorption processes followed the pseudo-second-order kinetics equation. The isotherms of Zr(IV) adsorption by KIT-6 exhibited good agreement with the Langmuir model, while the Freundlich model could be utilized to fit the adsorption on HMS, MCM-41, and SiO2-70 Å. The adsorption capacity of MCM-41 for Zr(IV) in 3 mol/L HNO3 was 54.91 mg/g, which is three times the adsorption capacity reported for commercial silica gel (17.91 mg/g). The thermodynamic parameters indicate that the adsorption processes for zirconium are endothermic reactions. Furthermore, the mesoporous silicas exhibited a pronounced selectivity in the adsorption of Zr(IV) within a simulated high-level liquid waste containing 10 co-existing cations (3 mol/L HNO3). This suggests that mesoporous silicas have great potential for Zr(IV) removal in actual radioactive liquids with high acidity during spent fuel reprocessing.