High-Strength Organic-Inorganic Composites with Superior Thermal Insulation and Acoustic Attenuation.

We demonstrate facile fabrication of highly filled, lightweight organic-inorganic composites comprising polyurethanes covalently linked with naturally occurring clinoptilolite microparticles. These polyurethane/clinoptilolite (PUC) composites are shown to mitigate particle aggregation usually observed in composites with high particle loadings and possess enhanced thermal insulation and acoustic attenuation compared with conventionally employed materials (e.g., drywall and gypsum). In addition to these functional properties, the PUC composites also possess flexural strengths and strain capacities comparable to and higher than ordinary Portland cement (OPC), respectively, while being ∼1.5× lighter than OPC. The porosity, density, and mechanical and functional properties of these composites are tuned by systematically varying their composition (diisocyanate, polyurethane, and inorganic contents) and the nature of the organic (reactivity and source of polyol) components. The fabrication process involves mild curing conditions and uses commonly available reagents (naturally occurring aluminosilicate particles, polyols, and diisocyanate), thereby making the process scalable. Finally, the composite properties are shown to be independent of the polyol source (virgin or recycled), underlining the generality of this approach for the scalable utilization of recycled polyols.

Fly ash degree of reaction in hypersaline NaCl and CaCl2 brines: Effects of calcium-based additives.

The pozzolanic reaction of fly ashes with calcium-based additives can be effectively used to solidify and chemically stabilize (S&S process) highly concentrated brines inside a cementitious matrix. However, complex interactions between the fly ash, the additive, and the brine typically affect the phases formed at equilibrium, and the resulting solid capacity to successfully encapsulate the brine and its contaminants. Here, the performances of two types of fly ash (a Class C and Class F fly ash) are assessed when combined with different additives (two types of cement, or lime with and without NaAlO2), and two types of brine (NaCl or CaCl2) over a range of concentrations (0 ≤ [Cl-] ≤ 2 M). The best performing matrices - i.e., the matrices with the highest Cl-containing phases content - were identified using XRD and TGA. The experimental results were then combined with thermodynamic modeling to dissociate the contribution of the fly ash from that of the additives. All results were implemented in a machine learning model that showed good accuracy at predicting the fly ash degree of reaction, allowing for the robust prediction of extended systems performance when combined with thermodynamic modeling.

Electrolytic Seawater Mineralization and the Mass Balances That Demonstrate Carbon Dioxide Removal.

We present the mass balances associated with carbon dioxide (CO2) removal (CDR) using seawater as both the source of reactants and as the reaction medium via electrolysis following the "Equatic" (formerly known as "SeaChange") process. This process, extensively detailed in La Plante E.C.; ACS Sustain. Chem. Eng.2021, 9, ( (3), ), 1073-1089, involves the application of an electric overpotential that splits water to form H+ and OH- ions, producing acidity and alkalinity, i.e., in addition to gaseous coproducts, at the anode and cathode, respectively. The alkalinity that results, i.e., via the "continuous electrolytic pH pump" results in the instantaneous precipitation of calcium carbonate (CaCO3), hydrated magnesium carbonates (e.g., nesquehonite: MgCO3·3H2O, hydromagnesite: Mg5(CO3)4(OH)2·4H2O, etc.), and/or magnesium hydroxide (Mg(OH)2) depending on the CO32- ion-activity in solution. This results in the trapping and, hence, durable and permanent (at least ∼10 000-100 000 years) immobilization of CO2 that was originally dissolved in water, and that is additionally drawn down from the atmosphere within: (a) mineral carbonates, and/or (b) as solvated bicarbonate (HCO3-) and carbonate (CO32-) ions (i.e., due to the absorption of atmospheric CO2 into seawater having enhanced alkalinity). Taken together, these actions result in the net removal of ∼4.6 kg of CO2 per m3 of seawater catholyte processed. Geochemical simulations quantify the extents of net CO2 removal including the dependencies on the process configuration. It is furthermore indicated that the efficiency of realkalinization of the acidic anolyte using alkaline solids depends on their acid neutralization capacity and dissolution reactivity. We also assess changes in seawater chemistry resulting from Mg(OH)2 dissolution with emphasis on the change in seawater alkalinity and saturation state. Overall, this analysis provides direct quantifications of the ability of the Equatic process to serve as a means for technological CDR to mitigate the worst effects of accelerating climate change.