This perspective proposes a potential pathway to diminish atmospheric CO2 accumulations which is distinct from traditional carbon capture and geological sequestration strategies and from existing negative emissions technologies (NETs). Unlike conventional sorbent- or solvent-based CO2 capture processes where substantial energy expenditures are associated with demixing and desorbing CO2, the single-step carbon sequestration and storage (sCS2) approach relies on electrolytic carbonate mineral precipitation using renewable energy within a simple and scalable process design. Although numerous approaches have implied electrolysis for carbon management, the sCS2 approach is unique in the following ways: (1) CO2 mineralization for promoting solid carbonate formation: The thermodynamic and kinetic barriers to carbonate precipitation are overcome by direct and in situ electrochemical forcing to stabilize dissolved inorganic carbon and divalent cations [Ca,Mg] to form carbonate minerals. (2) Flow-through membraneless electrolysis: A flowing electrolyte (seawater) is dissociated while in motion. The process utilizes cost-effective mesh electrodes while also decreasing the number of components and assembly steps and reducing the risk of device failure. (3) Integrated electrolytic reactor–rotary drum filter: An electroactive thin-film mesh cathode (eTFC) is suggested to be integrated within a rotary drum filter configuration, allowing for the filtration of dilute and polydispersed mineral precipitates at a low energy cost. These attributes render sCS2 as an approach worthy of more detailed evaluation, development, and scaling for global-scale carbon management.
Sequestration of CO2 within stable mineral carbonates (e.g., CaCO3) represents an attractive emission reduction strategy because it offers a leakage-free alternative to geological storage of CO2 in an environmentally benign form. However, the pH of aqueous streams equilibrated with gaseous streams containing CO2 (pH < 4) are typically lower than that which is required for carbonate precipitation (pH > 8). Traditionally, alkalinity is provided by a stoichiometric reagent (e.g., NaOH) which renders these processes environmentally hazardous and economically unfeasible. This work investigates the use of regenerable ion-exchange materials to induce alkalinity in CO2-saturated aqueous solutions such that the pH shift required for mineralization occurs without the need for stoichiometric reagents. Na+-H+ exchange isotherms (at [H+] = 10−8–10−1 M) and rates were measured for 13X and 4A zeolites and TP-207 and TP-260 organic exchange resins in batch equilibrium and fixed-bed exchange experiments, respectively. At solutions equilibrated with CO2 at 1.0 atm (pH = 3.9), H+ exchange capacities for the materials were similar (1.7–2.4 mmol H+/g material) and resulted in pH increases from 3.9 to greater than 8.0. Multi-component mixtures using Ca2+ and Mg2+ cations (at 10−3–10−1 M) in CO2-saturated water were used to probe competitive ion exchange. The presence of divalent cations in solution inhibited H+ exchange, reducing capacities to as low as 0.2 mmol H+/g for both resins and zeolites. Dynamic H+ exchange capacities in fixed-bed ion exchange columns were similar to equilibrium values for resins (∼1.5 mmol/g) and zeolites (∼0.8 mmol/g) using inlet solutions that were equilibrated with gaseous streams of CO2 at 1.0 atm. However, exchange kinetics were limited by intraparticle diffusion as indicated by the increased rate parameters with increasing inlet flow rates (20–160 cm3 min−1). Experimental calcite precipitation from mixing the alkaline CO32−-rich water solution obtained from the ion-exchange column with a simulated liquid waste stream solution achieved thermodynamic maximum yields. The results from these studies indicate that ion exchange processes can be used as an alternative to the addition of stoichiometric bases to induce alkalinity for the precipitation of CaCO3, thereby opening a pathway toward sustainable and economic mineralization processes.
Abstract:A threshold system is a reliability system whose success/failure is a threshold switching function in the successes/failures of its components. A coherent system (CS) is one that is causal, monotone, and with relevant components. The coherent threshold system (CTS), typically called the weighted k-out-of-n system, is consequently described by strictly positive weights and threshold. This paper presents recursive relations as well as boundary conditions for eight entities pertaining to a CTS. These are (a) expressions of monoform literals as well as disjoint or probabilityready expressions for either system success or failure, and (b) all-additive formulas as well as inclusion-exclusion ones for either system reliability or unreliability. These entities are obtained according to the best policy of implementing the Boole-Shannon expansion with respect to a higher-weight component before it is made with respect to a lower-weight one. With this best policy, the success and failure expressions with monoform literals are both minimal and shellable.Each of the eight entities considered is represented by an acyclic (loopless) signal flow graph (SFG). The SFG for system success or failure is isomorphic to a reduced ordered binary decision diagram, which is the optimal data structure for a Boolean function. The interrelations between the SFGs demonstrate optimal procedures for implementing (a) the probability (real) transform of a Boolean function, (b) inversion or complementation of a Boolean function, and (c) disjointing or orthogonalization of a sum-of-products expression of a Boolean function. The SFGs discussed herein for a CT can be extended to a general coherent system. They reduce to elegant symmetric regular graphs for the special case of a partially redundant system (k-out-of-n system).
W ö)«d «uE «Ë WO bMN « vM « s dO W c/Ë ¡UBI « w U U «-Ëoe W Ë"u*« X uB « rE VFK WD WO{U -WI dD rEM « Ác n u W K W U b u AEW oeUB ô« WO UL ô«Ë WO UO « WO ôu « ‰«Ëb « W ôb X uB « rEM Ÿ-U n Ë WL AE…dO J « rEMK UNLOLF sJ1 W u Ë W U oeu Ë s Ë ‰«Ëb « Ác ‰u …d u *« U uKF*« ¡«d s «dO n u « «c lH ABSTRACTWeighted voting systems play a crucial role in the investigation and modeling of many engineering structures and political and socio-economic phenomena. There is an urgent need to describe these systems in a simpli ed powerful mathematical way that can be generalized to systems of any size. An elegant description of voting systems is presented in terms of threshold Boolean functions. This description bene ts considerably from the wealth of information about these functions, and of the potpourri of algebraic and map techniques for handling them. The paper demonstrates that the prime implicants of the system threshold function are its Minimal Winning Coalitions (MWC). The paper discusses the Boolean derivative (Boolean difference) of the system threshold function with respect to each of its member components. The prime implicants of this Boolean difference can be used to deduce the winning coalitions (WC) in which the pertinent member cannot be dispensed with. Each of the minterms of this Boolean difference is a winning coalition in which this member plays a pivotal role. However, the coalition ceases to be winning if the member defects from it. Hence, the number of these minterms is identi ed as the Banzhaf index of voting power. The concepts introduced are illustrated with detailed demonstrative examples that also exhibit some of the known paradoxes of voting-system theory. Finally, the paper stresses the utility of threshold Boolean functions in the understanding, study, analysis, and design of weighted voting systems irrespective of size.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.