Thermochemical Properties of Synthesized Urea from Recovered Ammonia and Carbon Dioxide in Well-Ordered Nanospaces of Hollow Silica Spheres

The present work investigated the thermochemical properties of urea synthesized in well-ordered nanospaces of porous hollow silica spheres' shells from recovered ammonia and carbon dioxide in aqueous solution. Thermochemical behaviors of the urea synthesized in well-ordered nanospaces of the hollow spheres' shells prepared with 1-dodeclyamine were analyzed from the results of thermogravimetric analysis (TGA) and differential thermal analysis (DTA), and endothermic peaks assigned as the phase transition and decomposition were observed at ca. 440 and 514 K, respectively, which were higher than those of pristine urea (405 and 408 K, respectively), probably because of the nanoconfinement effect. The decomposition behavior was also confirmed by the result of diffuse reflectance infrared Fourier transform (DRIFT) spectra of the samples treated at various temperatures up to 573 K, and the decomposition of urea synthesized in the well-ordered nanospaces of the hollow spheres' shells started at 468 K and completed up to 533 K.

Preparation and properties of phosphinic acid-functionalized polyacrylonitrile hollow fiber membrane for heavy metal adsorption

In this study, phosphorylated polyacrylonitrile hollow fiber membrane was synthesized by reacting aminated polyacrylonitrile hollow fiber membrane with phosphinic acid in a Mannich reaction. The batch single-factor measurements revealed that the phosphorylated polyacrylonitrile (PPAN) membrane had an outstanding ability for Hg²⁺ adsorption. Thermodynamic investigations indicated that the adsorption process was homogenous, and the theoretical maximum adsorption capacity predicted by the Langmuir model was 371.75 mg·g^-1. The PPAN membrane was able to successfully chelate Hg²⁺ ions and attain saturation in 4 h, demonstrating that the reaction was chemically controlled by the adsorption kinetics. Based on the FT-IR and XPS spectral characterization data, successful phosphinic acid group grafting was proven, and a plausible mechanism for Hg²⁺ adsorption by PPAN membranes was presented. Furthermore, the five adsorption-desorption cycle experiments revealed that PPAN hollow fiber membranes had outstanding reusability, indicating a possible use for removing heavy metal ions from wastewater.

Conversion of Recovered Ammonia and Carbon Dioxide into Urea in the Presence of Catalytically Active Copper Species in Nanospaces of Porous Silica Hollow Spheres

The present study firstly reported porous silica hollow spheres as a host material for recovery of ammonia and carbon dioxide and conversion of the compounds into urea. These compounds were effectively introduced into the hollow spheres from an aqueous solution including ammonium and carbonate ions accompanied with catalytically active copper ions from the analyses of diffuse reflectance infrared Fourier transform (DRIFT) spectra and diffusion reflectance ultraviolet-visible and near-infrared (DR UV-vis-NIR) spectra. The ammonium and carbonate ions were converted into urea in the hollow spheres at 323 K under 0.5 MPa of argon atmosphere from the results of the DRIFT spectra. From the results of nitrogen sorption isotherms and X-ray photoelectron spectra (XPS) spectra, the amount of the generated urea depended on the amount of the introduced ammonium ions and the size distribution of the nanospaces in the hollow spheres. Urea was highly generated in the hollow spheres with a high amount of ammonium ions and well-ordered nanospaces from the reactants at high density.

Two dimensional MXenes as emerging paradigm for adsorptive removal of toxic metallic pollutants from wastewater

Effective methods for removing harmful metals from wastewater have had a huge impact on reducing freshwater scarcity. Because of its excellent removal effectiveness, simplicity and low cost at ambient conditions, adsorption is one of the most promising purifying approaches. MXene-based nanoarchitectures have proven to be effective adsorbents in a variety of harmful metal removal applications. This owes from the distinctive features such as, hydrophilicity, high surface area, electron-richness, great adsorption capacity, and activated metallic hydroxide sites of MXenes. Given the rapid advancement in the design and synthesis of MXene nanoarchitectures for water treatment, prompt updates on this research area are needed that focus on removal of toxic metal, such as production routes and characterization techniques for the advantages, merits and limitations of MXenes for toxic metal adsorption. This is in addition to the fundamentals and the adsorption mechanism tailored by the shape and composition of MXene based on some representative paradigms. Finally, the limits of MXenes are highlighted, as well as their potential future research directions for wastewater treatment. This manuscript may initiate researchers to improve unique MXene-based nanostructures with distinct compositions, shapes, and physiochemical merits for effective removal of toxic metals from wastewater.

Synthesis of Zeolite from Circulated Fluidized Bed Coal Fly Ash

Circulating fluidized bed combustion (CFBC) is known for its ability to significantly reduce the emission NOx and SO2 from coal combustion, the fly ash produced from CFBC (CFBFA), however, is...

Sustainable valorization of mesoporous aluminosilicate composite from display panel glasses waste for adsorption of heavy metal ions

The recycling of the huge amount of thin film transistor liquid crystal display (TFT-LCD) glass wastes has become one of the worldwide environmental issues. Herein, a novel and cost-effective synthesis method for the fabrication of mesoporous aluminosilicate composite (M-ANC) from the TFT-LCD waste has been developed to serve as the environmentally benign adsorbent for the removal of metal ions including Cu²⁺, Zn²⁺ and Ni²⁺. After melting at 1000 °C in the presence of Na₂CO₃ for phase separation, nanoparticles with average particle size of 12 nm appear on the surface of M-ANC, and subsequently results in the production of mesoporous structure with a surface area of 175 m² g^-1. The tailored M-ANC shows negatively charged and functional groups, which exhibits an excellent adsorption capacity toward metal ion removal in the pH range of 1.5-7.0. The maximum Langmuir adsorption capacity of Cu²⁺, Zn²⁺ and Ni²⁺ are determined to be 64.5, 34.0 and 23.1 mg g^-1, respectively, at pH 3.5. Moreover, the environmental applicability of M-ANC is evaluated by column experiment in the presence of real electroplating wastewater. M-ANC can effectively remove Ni²⁺ in the electroplating wastewater with the adsorption capacity of 18.7 mg g^-1. Results obtained in this study clearly indicate that M-ANC recycled from TFT-LCD is a novel environmentally friendly adsorbent toward metal ion removal, which can open a gateway to fabricate mesoporous aluminosilicate materials through the recycling of other electronic wastes for real environmental application to remove metal ions and other emerging pollutants in the contaminated water and wastewater.

Improving barium ion adsorption on two-dimensional titanium carbide by surface modification

To capture radioactive barium from wastewater, the Ti₃C₂T_x material was modified by activation treatment and it exhibited high adsorption ability for removal of Ba²⁺ from aqueous solution.

Highly efficient Pb(ii) and Cu(ii) removal using hollow Fe3O4@PDA nanoparticles with excellent application capability and reusability

The easily synthesized Fe₃O₄@PDA material showed excellent performance for Pb(ii) and Cu(ii) elimination from wastewater, and its adsorption mechanism was revealed.

Waste Printed Circuit Board (PCB) Recycling Techniques

With the development of technologies and the change of consumer attitudes, the amount of waste electrical and electronic equipment (WEEE) is increasing annually. As the core part of WEEE, the waste printed circuit board (WPCB) is a dangerous waste but at the same time a rich resource for various kinds of materials. In this work, various WPCB treatment methods as well as WPCB recycling techniques divided into direct treatment (landfill and incineration), primitive recycling technology (pyrometallurgy, hydrometallurgy, biometallurgy and primitive full recovery of NMF-non metallic fraction), and advanced recycling technology (mechanical separation, direct use and modification of NMF) are reviewed and analyzed based on their advantages and disadvantages. Also, the evaluation criteria are discussed including economic, environmental, and gate-to-market ability. This review indicates the future research direction of WPCB recycling should focus on a combination of several techniques or in series recycling to maximize the benefits of process.

Recyclable 3D graphene aerogel with bimodal pore structure for ultrafast and selective oil sorption from water

Development of graphene based porous sorbent to overcome the challenges, such as low uptake capacity, slow sorption rate, and non-recyclability, associated with conventional sorbents.