Phytic acid-modified carboxymethyl cellulose hydrogel for uranium adsorption from aqueous solutions.

Phytic acid-modified carboxymethyl cellulose (CMC-PA) has been investigated as a promising adsorbent for the removal of uranium from aqueous solutions. The synthesis of CMC-PA involves the hydrogen bonding interaction between CMC and PA, resulting in the incorporation of PA groups onto the cellulose backbone. The hydrophilicity, reusability and adsorption capacity of the prepared CMC-PA hydrogel have improved with the increase of PA content. Moreover, the adsorption experiments were conducted by varying parameters such as pH, initial uranium concentration, and contact time. The results showed that CMC-PA exhibited excellent uranium adsorption performance, with a theoretical maximum adsorption capacity of 436 mg/g. In addition, the material exhibits excellent reusability, and the reusability improves with the increase of crosslinking density, indicating that the crosslinking structure of the polymer gel can effectively enhance the structural stability of the material. Furthermore, CMC-PA also exhibits high selective adsorption performance towards uranium ions in the presence of various competing ions. Its high adsorption capacity, reusability, and selectivity make it a promising candidate for high-performance uranium ion adsorbents.

Preparation of the N, P-Codoped Carbonized UiO-66 Nanocomposite and Its Application in Supercapacitors.

Preparing high-performance electrode materials from metal-organic framework precursors is currently a hot research topic in the field of energy storage materials. Improving the conductivity of such electrode materials and further increasing their specific capacitance are key issues that must be addressed. In this work, we prepared phosphoric acid-functionalized UiO-66 material as a precursor for carbonization, and after carbonization, it was combined with activated carbon to obtain nitrogen-/phosphorus-codoped carbonized UiO-66 composite material (N/P-C-UiO-66@AC). This material exhibits excellent conductivity. In addition, the carbonized product ZrO2 and the nitrogen-/phosphorus-codoped structure evidently improve the pseudocapacitance of the material. Electrochemical test results show that the material has a good electrochemical performance. The specific capacitance of the supercapacitor made from this material at 1.0 A/g is 140 F/g. After 5000 charge-discharge cycles at 10 A/g, its specific capacitance still remains at 88.5%, indicating that the composite material has good cycling stability. The symmetric supercapacitor assembled with this electrode material also has a high energy density of 11.0 W h/kg and a power density of 600 W/kg.

Preparation of N,P Co-doped Porous Carbon Derived from Daylily for Supercapacitor Applications.

Biomass-derived activated carbon is a widely used electrode material for supercapacitors. One of the keys to preparing high-performance activated carbon is the selection of appropriate precursors. Daylily is a common edible herb and is widely planted in Asia. It is rich in nitrogen and phosphorus, so it can be used as a precursor of heteroatom-doped activated carbon. Herein, a daylily-derived porous carbon with a large specific surface area and high content of heteroatoms has been successfully prepared by a simple carbonization method. The as-prepared carbon materials showed a remarkable specific capacitance of 299.1 F/g at 0.5 A/g and excellent cycling stability of 99.6% after 4000 cycles at a current density of 1 A/g. Moreover, the assembled symmetric supercapacitor showed a high energy density of 21.6 Wh/kg at a power density of 598.2 W/kg in 6 M KOH electrolyte. These results demonstrate that the daylily-derived porous carbon is an excellent material for high-performance supercapacitors.

Efficient removal of uranium (VI) with a phytic acid-doped polypyrrole/ carbon felt electrode using double potential step technique.

In order to efficiently extract uranium from uranium-containing wastewater, a novel acid doped polypyrrole/carbon felt (PA-PPy/CF) electrode was prepared via a facile electrodeposition method. For this material, PA and PPy combined to form a stable chemical structure by a charge compensation mechanism. The electrochemical characterization results showed that PA-PPy can significantly accelerate the electrochemical reduction rate of uranium ions. Moreover, a double potential step technique (DPST) was applied to prevent water splitting and maintained the electrocatalytic reduction activity of the surface groups during the electrochemical adsorption process. The removal efficiency obtained by the DPST method was six times higher than that obtained by the conventional chemical adsorption. When the concentrations of uranyl nitrate were 10, 20, 50, and 100 mg/L, the removal efficiencies of uranium were 98.8%, 98.1%, 94.6%, and 93.7%, and the adsorption capacities of uranium were 164.7, 326.9, 788.5, and 1562.0 mg/g, respectively. This material also showed an excellent recycling performance and remarkable selectivity for uranium ions. This work may shed light on the development of removal system for uranium (VI).

Petal-like CoMoO4 Clusters Grown on Carbon Cloth as a Binder-Free Electrode for Supercapacitor Application.

The development of supercapacitors with a high energy density and power density is of great importance for the promotion of energy storage technology. In this study, we designed and prepared petal-like CoMoO4 clusters combined with carbon cloth as an excellent self-standing and binder-free electrode for asymmetric supercapacitors. Due to the abundant electrochemical active sites, the promising electron conduction, and ion diffusion rate, the CoMoO4@carbon cloth (CoMoO4@CC) electrode exhibits an excellent electrochemical performance. The results show that the CoMoO4@CC material exhibits a high specific capacitance (664 F/g at a current density of 1 A/g) and an excellent cycle stability (capacitance remains at 84.0% after 1000 cycles). The assembled symmetrical supercapacitor has an energy density of 27 Wh/kg when the power density is 600 W/kg. Even at a higher power density (6022 W/kg), it still maintains a good energy density (18.4 Wh/kg).

Fabrication of a Three-Dimensionally Networked MoO3/PPy/rGO Composite for a High-Performance Symmetric Supercapacitor.

A three-dimensionally interconnected molybdenum trioxide (MoO3)/polypyrrole (PPy)/reduced graphene oxide (rGO) composite was synthesized via an eco-friendly three-step method. The as-obtained electrode shows a high specific capacity of 412.3 F g-1 at a current density of 0.5 A g-1 and a good cycling stability (85.1% of the initial specific capacitance after 6000 cycles at 2 A g-1 is retained), and these excellent electrochemical performances can be attributed to the unique structure, remarkable electrical conductivity, and the synergetic effects between MoO3, PPy, and rGO. Furthermore, a symmetric supercapacitor based on a MoO3/PPy/rGO electrode was assembled to investigate the practical application performance of this material. The results demonstrate a high energy density of 19.8 W h kg-1 at a power density of 301 W kg-1. These findings shine a light on the rational design of electrode materials with multicomponents for high-performance supercapacitors.

Efficient Removal of Uranium(VI) from Aqueous Solutions by Triethylenetetramine-Functionalized Single-Walled Carbon Nanohorns.

In the present study, SWCNH-COOH and SWCNH-TETA were fabricated using single-walled carbon nanohorns (SWCNHs) via carboxylation and grafting with triethylenetetramine (TETA) for uranium (VI) ion [U(VI)] removal. The morpho-structural characterization of as-prepared adsorbing materials was performed by transmission electron microscopy, X-ray diffractometry, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Several parameters including the pH value of the aqueous solutions, contact time, temperature, and U(VI) concentration were used to evaluate the sorption efficiency of SWCNH-COOH and SWCNH-TETA. The Langmuir isotherm model could well represent the as-obtained adsorption isotherms, and the kinetics was successfully modeled by pseudo-second-order kinetics in the adsorption process. The maximum adsorption capacity of SWCNH-TETA was calculated as 333.13 mg/g considering the Langmuir isotherm model. Thermodynamic studies showed that adsorption proved to be a spontaneous endothermic process. Moreover, SWCNH-TETA exhibited excellent recycling performance and selective adsorption of uranium. Furthermore, the possible mechanism was investigated by XPS and density functional theory calculations, indicating that the excellent adsorption was attributed to the cooperation capability between uranium ions and nitrogen atoms in SWCNH-TETA. This efficient approach can provide a strategy for developing high-performance adsorbents for U(VI) removal from wastewater.

Effect of stretching on the mechanical properties in melt-spun poly(butylene succinate)/microfibrillated cellulose (MFC) nanocomposites.

In order to prepare poly(butylene succinate)/microfibrillated cellulose composites with high performance, in this work, microfibrillated cellulose (MFC) was first treated by acetylchloride with ball-milling to improve its interfacial compatibility with poly(butylene succinate) (PBS). Then melt stretching processing was adopted to further improve the dispersion and orientation of MFC in as-spun PBS fiber. And the effect of MFC on the crystalline structure and mechanical properties were systematically investigated for the melt-spun fibers prepared with two different draw ratios. The dispersion, alignment of the MFC and interfacial crystalline structure in the composite fibers are significantly influenced by the stretching force during the melt spinning. The possible formation of nanohybrid shish kebab (NHSK) superstructure where aligned MFC as shish and PBS lamellae as kebab has been suggested via SEM and SAXS in the composite fibers prepared at the high draw ratio. Large improvement in tensile strength has been realized at the high draw ratio due to the enhanced orientation and dispersion of MFC as well as the formation of NHSK.