High mechanical property and hydrophilic electrospun poly amidoxime/poly acrylonitrile composite nanofibrous mats for extraction uranium from seawater

Seawater reserves about 4.5 billion tons of uranium, if properly extracted, could be a sustainable green energy resource for hundreds of years, alternating its limited terrestrial ore and reducing the CO2 emitted from fossil fuels. The current seawater uranium adsorbents suffer neither economically viable nor adsorption efficiency, requiring more development to harvest satisfactorily uranium from seawater. Amidoxime-based fibrous adsorbents are the most promising adsorbents of seawater uranium due to abundant chelating sites. However, they suffer from severe shrinkage and stiffness once they dry, losing porous architecture and mechanical properties. Herein, an economical and scalable two-nozzle electrospinning technology was applied to produce poly amidoxime nanofibers (PAO NFs) supported by Poly acrylonitrile nanofibers (PAN NFs) as composite PAO/PAN nanofibrous mats with high structure stability. These PAO/PAN mats, with rapid wettability and excellent mechanical strength, show promising uranium adsorption capacities of 369.8 mg/g at seawater pH level, much higher than PAO and PAN NFs. The uranium adsorption capacity of the PAO/PAN mat reached 5.16 mg/g after 7 days of circulating (10 ppm uranium) spiked natural seawater. Importantly, the composite mat maintained its fibrous structure after five adsorption-desorption cycles with more than 80 % of its adsorption capacity, confirming its recyclability and stability. Therefore, the composite PAO/PAN mat fulfills the basic requirements for effectively and economically trapping uranium from seawater, which could be a matrix for further development.

Effects of type and distribution of clay minerals on the physico-chemical and geomechanical properties of engineered porous rocks

The study of the properties of engineered rocks is of great importance to researchers in engineering sciences such as petroleum, mining, and civil engineering owing to their wide application in these fields. In the present study, a physico-chemical and geomechanical investigation was carried out on the effects of different clay minerals on porous rocks. Various chemical products formed during chemical interactions between cement, clay minerals, and water can change the pore structure and thus the rock characteristics. The results of the current study showed that increasing the clay content could remarkably reduce the porosity and permeability of the rock by an average of 86% and 6.76%, respectively. In this regard, samples containing kaolinite were further influenced due to their new pore structure. Moreover, a power relationship was found between sonic velocity and porosity, which can be used to predict rock properties. Chemical analysis indicated an amplification in quantities of chemical products, particularly calcium silicate hydrate and portlandite, due to an increase in clay content. The impacts of porosity and cementation quality as two main factors on rock strength have also been studied. The outcomes revealed that a reduction in porosity could compensate for detrimental effects of poor bond quality and consequently improved UCS by up to 30% in samples containing kaolinite, while decreasing the degree of cementation prevailed over the porosity reduction in specimens including illite and resulted in a 14% decrease in UCS. The effects of porosity and bond quality on UCS would cancel each other out in samples containing bentonite. It is worth noting that when it comes to changes in geomechanical characteristics, the dominant factor (i.e., porosity reduction or cementation quality) determines the ultimate effect of clay minerals on the properties of engineered porous rocks.

A green synthesis of calcium silicate nanopowders from silica fume and marble sawing dust by a microwave irradiation-assisted route

Calcium silicate nanopowders have been successfully synthesized from solution mixtures of silica fume and marble sawing dust via a simple, fast and eco-friendly microwave irradiation method.

A nanocomposite paper comprising calcium silicate hydrate nanosheets and cellulose nanofibers for high-performance water purification

Removal of soluble organic and inorganic contaminants from wastewater to produce clean water has received much attention recently. However, the simultaneous enhancement of water permeability and removal efficiency is still a challenge for filtration membranes. Here, we present a new kind of nanocomposite paper (CSH/CNF) consisting of calcium silicate hydrate (CSH) nanosheets and cellulose nanofibers (CNFs), and demonstrate the rapid water filtration and highly efficient contaminant (e.g., dyes, proteins, and metal ions) adsorption properties. The CNFs can serve as the bridging material to connect the CSH nanosheets to form a porous network structure and vital channels in the CSH/CNF paper for rapid water transportation. The weight ratio of CSH nanosheets in the paper is up to 75–85%. The weight ratio of CSH nanosheets has a significant effect on the water permeability and removal efficiency. The water permeability of the CSH/CNF paper with 82.5 wt% CSH nanosheets reaches as high as 312.7 L m⁻² h⁻¹ bar⁻¹, which is about 14.7 times that of the CSH/CNF paper with 75 wt% CSH nanosheets. Because of the high specific surface area and abundant adsorption sites of CSH nanosheets, the CSH/CNF paper with 82.5 wt% CSH nanosheets exhibits high adsorption capacities and removal efficiencies for methyl blue (242.6 mg g⁻¹, 97.3%), bovine serum albumin (289.2 mg g⁻¹, 98.5%) and Pb²⁺ ions (366.2 mg g⁻¹, 98.2%). The CSH/CNF nanocomposite paper holds great potential for application in environmental wastewater purification.

A nanocomposite paper with high water permeability and removal efficiency was prepared for the removal of organic and inorganic contaminants by filtration.

Highly Dispersed Ni Nanoparticles on Anhydrous Calcium Silicate (ACS) Nanosheets for Catalytic Dry Reforming of Methane: Tuning the Activity by Different Ways of Ni Introduction

Three kinds of nickel-loaded anhydrous calcium silicate nanocatalysts (ACS), including Ni-ACS-Dop, Ni-ACS-Iex and Ni-ACS-Im, were prepared by introducing Ni species through doping in the synthesis of calcium silicate hydrate (CSH) nanosheets, ion-exchange with premade CSH nanosheets and deposition on calcined ACS nanosheets, respectively. Although Ni species were introduced in different ways, all the Ni-ACS catalysts showed similar chemical compositions and microstructures, where Ni nanoparticles were highly dispersed on the ultrathin ACS nanosheets with a large surface area and good thermal stability. However, the differences in the way of Ni introduction did produce Ni with different electronic states. The Ni-ACS-Iex catalyst with "surface Ni" as a dominant form had more electrons enriched on the surface of Ni, which led to the highest activity in the dry reforming of methane (DRM) reaction among the three catalysts, whereas the Ni-ACS-Dop catalyst with "lattice Ni" as a dominant form showed an electron-deficient property and lowest activity. Different from the introduction of a more favourable nanostructure or chemical component to the catalyst system, this work controlled the chemical environment of metal precursors and created metal catalysts with a preferred surface electronic state during synthesis, which could be a new strategy to improve the catalytic activity.

OPAC (orange peel activated carbon) derived from waste orange peel for the adsorption of chlorophenoxyacetic acid herbicides from water: Adsorption isotherm, kinetic modelling and thermodynamic studies

This study presents the orange peel activated carbon (OPAC), derived from biowaste precursor (orange peel) by single step pyrolysis method and its application for the adsorption of chlorophenoxyacetic acid herbicides from the water. The OPAC exhibited the surface area of 592.471 m² g^-1, pore volume and pore diameter of 0.242 cc g^-1 and 1.301 nm respectively. The adsorption kinetics and thermodynamic equilibrium modelling for all chlorophenoxyacetic acid herbicides were investigated. The various parametric effects such as pH and temperature were evaluated. A pseudo-second-order kinetic model was well fitted for all the herbicides. The Langmuir isotherm was obeyed for all the herbicides and the maximum Langmuir capacity of 574.71 mg g^-1 was achieved. The thermodynamic studies revealed that the adsorption increases with increase in temperature. The results shows that the orange peel derived carbon (OPAC) as effective and efficient adsorbent material for the removal of chlorophenoxyacid herbicides from the water.

Efficient extraction of uranium from aqueous solution using an amino-functionalized magnetic titanate nanotubes

In this paper, titanate nanotubes/cobalt ferrite/tetraethylenepentamine (TNTs/CoFe₂O₄/TEPA) adsorbents were prepared for the adsorption of uranium (VI) from the solution. Its morphology was observed by transmission electron microscopy (TEM) and exhibited the uniform well tubular structure. TNTs/CoFe₂O₄/TEPA composites were easily separated from solution by an external magnetic field. The removal of uranium (VI) from aqueous solution (ppm level) and simulated seawater (ppb level) were investigated by the TNTs/CoFe₂O₄/TEPA composites. Batch adsorption experiments were conducted to determine the effect of varying pH, contact time, and reaction temperature. The best fit for uranium (VI) adsorption was obtained with the Langmuir model, and the highest adsorption of TNTs/CoFe₂O₄/TEPA composites reached 509.89 mg-U/g-adsorbent at pH 6. From an investigation of the adsorption by XRD, FTIR and XPS, it is suggested that the surface complexation and cation exchange were the main adsorption mechanism. In addition, TNTs/CoFe₂O₄/TEPA composites maintained good adsorption properties after five sorption-desorption cycles. Therefore, we conclude that the adsorbents are promising materials for the removal of uranium (VI) from aqueous solutions.

Facile synthesis of silver nanoparticles deposited on a calcium silicate hydrate composite as an efficient bactericidal agent

Silver nanoparticles deposited calcium silicate hydrate composite was synthesized and demonstrated high antibacterial activities against Gram-negative and Gram-positive bacteria.

The removal of aqueous uranium by SBA-15 modified with phosphoramide: a combined experimental and DFT study

Phosphoramide-modified SBA-15 materials were prepared via a two-step process involving: (1) the synthesis of phosphoramide via amidation of phosphoryl chloride with a primary amine and (2) modification of the phosphoramide onto SBA-15.

Polypyrrole/cobalt ferrite/multiwalled carbon nanotubes as an adsorbent for removing uranium ions from aqueous solutions

A novel rod-like, dual-shell structural adsorbent of polypyrrole/cobalt ferrite/multiwalled carbon nanotubes (PPy/CoFe₂O₄/MWCNTs) was successfully synthesized by a hydrothermal method, which could easily separate uranium(vi) ions with an external magnetic field.

Biorecognition and highly sensitive determination of Ribonuclease A with chemiluminescence sensor based on Fe3O4/multi-walled carbon nanotubes/SiO2-surface molecular imprinting polymer

A new functional material Fe₃O₄/MWCNTs/SiO₂ was used as a supporting material to prepare SMIP for the CL determination of RNase A.

In situ growth of ZnO nanorod arrays on cotton cloth for the removal of uranium(vi)

In situ growth of ZnO nanorod arrays on cotton cloth (ZnO/CC) was proposed to remove uranium (vi) from aqueous solution. The as-prepared adsorbent is easy separation from the reaction medium after adsorption.