Toward a Delaminated Organotalc: The Use of Polyamidoamine Dendrons

Nanosilica polyamidoamine dendrimers for enhanced direct air CO2 capture

Exploring efficient systems to recover CO2 from the atmosphere could be a way to address the global carbon emissions issue. Herein, we report the synthesis of nanosilica (NS) functionalized with polyamidoamine (PAMAM) dendrimers (NS-PAMAM) as efficient adsorbents for CO2 capture under simulated direct air capture (DAC) (400 ppm CO2 in helium at 30 °C) and indoor air (≥400 ppm, 50 ± 3% RH at 30 °C) conditions. The results inferred that the 1st (NS-G1.0), 2nd (NS-G2.0), 3rd (NS-G3.0), and 4th (NS-G4.0) generations of the NS-PAMAM dendrimers exhibited excellent performance for CO2 capture. Compared to the other generations, NS-G3.0 demonstrated superior CO2 adsorption capacities of 0.50 mmol g-1 under simulated dry CO2 conditions (400 ppm in He), 1.02 mmol g-1 under indoor air (dry) CO2 conditions (≥400 ppm, 26 ± 3% RH), and 1.54 mmol g-1 under indoor air (humid) CO2 conditions (≥400 ppm, 50 ± 3% RH). The study included the evaluation of CO2 adsorption-desorption performance of the NS-PAMAM dendrimers under varying structural and chemical parameters, kinetics, regeneration at low temperature (80 °C), as well as CO2 adsorption under humid conditions. Additionally, NS-G3.0 displayed a substantially superior performance with stable CO2 capture displayed during ten short temperature swing adsorption (TSA) cycles, making it a promising candidate for CO2 capture from ambient air. Finally, we demonstrated the recovery and reutilization of the captured CO2 for both the synthesis of formate via carbonate hydrogenation and for the production of calcium carbonate pellets.

Superior performance of oxygen vacancy-enriched Cu-Co3O4/urushiol-rGO/peroxymonosulfate for hypophosphite and phosphite removal by enhancing singlet oxygen

The treatment of wastewater containing hypophosphite [P(I)] and phosphite [P(III)] is challenged by limitations of traditional Fenton oxidation such as low efficiency, secondary pollution and high costs. This study introduced a facile solvent-thermal method to synthesize Cu-Co3O4 nanoparticles uniformly loaded on graphene (Cu-Co3O4/U-rGO) through the reduction and coordination effects of urushiol (U). As prepared Cu-Co3O4/U-rGO exhibited excellent activity in activating peroxymonosulfate (PMS) for the oxidation of P(I)/P(III) to phosphate [P(V)] (0.229 min-1), along with high stability and reusability (91.5 % after 6 cycles), low metal leaching rate (Co: 0.2 mg/L, Cu: 0.05 mg/L), insensitivity to common anions in water and a wide pH range (3-11). The activation mechanism involved the synergistic effects from both urushiol and graphene, which promoted redox of Cu+/Cu2+ and Co2+/Co3+ and induced abundant oxygen vacancies for PMS activation to produce singlet oxygen. Furthermore, the Cu-Co3O4/U-rGO/PMS was also excellent in the oxidative removal of organic phosphorus. This study is expected to advance strategies for the treatment of P(I)/P(III)-rich wastewater and provide new insights for the development of low-cost, highly efficient heterogeneous catalysts with abundant oxygen vacancies.

Hydrothermal-Freeze-Casting of Poly(amidoamine)-Modified Graphene Aerogels towards CO2 Adsorption

This article presents novel poly(amidoamine) (PAMAM) dendrimer-modified with partially-reduced graphene oxide (rGO) aerogels, obtained using the combined solvothermal synthesis-freeze-casting approach. The properties of modified aerogels are investigated with varying synthesis conditions, such as dendrimer generation (G), GO:PAMAM wt. ratio, solvothermal temperature, and freeze-casting rate. Scanning electron microscopy, Fourier Transform Infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy are employed to characterize the aerogels. The results indicate a strong correlation of the synthesis conditions with N content, N/C ratio, and nitrogen contributions in the modified aerogels. Our results show that the best CO₂ adsorption performance was exhibited by the aerogels modified with higher generation (G7) dendrimer at low GO:PAMAM ratio as 2:0.1 mg mL⁻¹ and obtained at higher solvothermal temperature and freeze-casting in liquid nitrogen. The enclosed results are indicative of a viable approach to modify graphene aerogels towards improving the CO₂ capture.

Organically modified layered magnesium silicates to improve rheology of reservoir drilling fluids

Petroleum well drilling fluids are one of the most significant constituents in the subterranean drilling processes to meet an increasing global demand for oil and gas. Drilling fluids experience exceptional wellbore conditions, e.g. high temperature and high pressure that adversely affect the rheology of these fluids. Gas and oil well drilling operations have to adjourn due to changes in fluid rheology, since the drilling fluids may lose their effectiveness to suspend heavy particles and to carry drilled cuttings to the surface. The rheological properties of drilling fluids can be controlled by employing viscosifiers that should have exceptional stability in downhole environments. Here, we have developed next-generation viscosifiers-organically modified magnesium silicates (MSils)-for reservoir drilling fluids where organic functionalities are directly linked through the Si-C bond, unlike the industry's traditional viscosifier, organoclay, that has electrostatic linkages. The successful formation of covalently-linked hexadecyl and phenyl functionalized magnesium silicates (MSil-C16 and MSil-Ph) were confirmed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA). Identical drilling fluid formulations were designed for comparison using MSils and a commercial viscosifier. The rheological properties of fluids were measured at ambient conditions as well as at high temperatures (up to 150 °C) and high pressure (70 MPa). Owing to strong covalent linkages, drilling fluids that were formulated with MSils showed a 19.3% increase in yield point (YP) and a 31% decrease in apparent viscosity (AV) at 150 °C under 70 MPa pressure, as compared to drilling fluids that were formulated with traditional organoclay. The higher yield point and lower apparent viscosity are known to facilitate and increased drilling rate of penetration of the fluids and an enhanced equivalent circulation density (ECD), the dynamic density condition, for efficient oil and gas wells drilling procedures.

Soft-Pillared@Magadiite: influence of the interlayer space and amine type on CO2 adsorption

Layered silicates are versatile materials that can be grafted with different organosilanes for several applications. Despite this, there are few studies on the use of layered silicate-based materials in CO₂ adsorption. In this regard, the present study describes the synthesis of organo-magadiite followed by simultaneous grafting with two organosilanes ((3-glycidyloxypropyl)trimethoxysilane (GPTS) and N¹-(3-trimethoxysilylpropyl)diethylenetriamine (TMSPETA)) to prepare an adsorbent labeled Soft-Pillared@Magadiite. The adsorbents were characterized through XRD, ¹³C- and ²⁹Si-NMR, TGA/DTG, and elemental analyses of carbon, hydrogen, and nitrogen (CHN). The results suggest that this adsorbent has an expanded interlayer space (3.05 nm) that is larger than the interlayer space when the layered material is grafted with the organosilanes separately, and it may display improved CO₂ adsorption. The CO₂ adsorption was evaluated by TGA, CO₂-TPD, and DSC. Moreover, the adsorption isotherms were fitted using a pseudo-second order, a fractional order, and Avrami models. The optimum adsorption temperature of Soft-Pillared@Magadiite was 25 °C, and the adsorption capacity and efficiency were 0.36 mmol g^-1 and 0.15, respectively, obtained using 5 vol% CO₂ in He for 3 h. The CO₂-TPD shows that the desorption of CO₂ occurs below 90 °C, and from DSC, it is found that thermodynamic parameters, specifically sensible heat and heat of regeneration, are low as compared to those of aqueous MEA solution; the current technology indicates that Soft-Pillared@Magadiite has a good potential for CO₂ adsorption.

Organoclays with carbosilane dendrimers containing ammonium or phosphonium groups

New composite materials could reveal attractive capabilities and favourable properties.

Gel Electrolytes with Polyamidopyridine Dendron Modified Talc for Dye-Sensitized Solar Cells

Organic-inorganic hybrid layered materials are proposed as additives in a quasi-solid gel electrolyte for dye-sensitized solar cells. Talcs could provide a low-cost and environmentally friendly, as well as abundant, option as gelators. Here, talcs were prepared by functionalizing an organotalc with three polyamidopyridine dendron generations, PAMPy-talc-Gn (n = 1, 2 and 3). PAMPy dendrons grow parallel to the lamellae plane and form an organized structure by intermolecular interactions. In addition, polyiodide-dendron charge-transfer complexes were prepared onto the organotalc by adsorption of iodine. In this work, the effect of the dendron generation of PAMPy-talc and the influence of polyiodide intercalation on solar cell performance and stability were investigated. The best results were reached with the use of lowest-generation PAMPy-talc (η = 4.5 ± 0.3%, V_OC = 710 ± 19 mV, J_sc = 10.4 ± 0.9 mA cm^-2, and FF = 61 ± 2%): 15% higher efficiency compared to similar liquid devices. While some previously studied talcs illustrate very strong absorption of the iodide from the electrolyte, in the case of PAMPy-talc such interfering effects were absent: In a 1000 h light soaking test, the PAMPy-talc cells both with and without polyiodide intercalation demonstrated stable performances. Furthermore, the color analysis of the electrolyte indicated that the color of the electrolyte remained stable after an initial period of stabilization, which is a good indication of the compound being stable and not absorbing charge carriers from the electrolyte. The performance and stability results indicate that PAMPy-talc has potential as a gelling method for electrolytes for dye solar cells.