Technical, economic, and environmental feasibility of rice hull ash from electricity generation as a mineral additive to concrete.

A circular economy based on symbiotic relationships among sectors, where the waste from one is resource to another, holds promise for cost-effective and sustainable production. This research explores such a model for the agriculture, energy, and construction sectors in California. Here, we develop new an understanding for the synergistic utilization mechanisms for rice hull, a byproduct from rice production, as a feedstock for electricity generation and rice hull ash (RHA) used as a supplementary cementitious material in concrete. A suite of methods including experimental analysis, techno-economic analysis (TEA), and life-cycle assessment (LCA) were applied to estimate the cost and environmental performance of the system. TEA results showed that the electricity price required for break even on expenses without selling RHA is $0.07/kWh, lower than the market price. As such, RHA may be available at little to no cost to concrete producers. Our experimental results showed the viability of RHA to be used as a supplementary cementitious material, meaning it can replace a portion of the cement used in concrete. LCA results showed that replacing 15% of cement with RHA in concrete can reduce carbon dioxide equivalent (CO2e) emissions by 15% while still meeting material performance targets. While the substitution rate of RHA for cement may be modest, RHA generated from California alone could mitigate 0.2% of total CO2e from the entire cement production sector in the United States and 1% in California.

Carboxymethylated cyclodextrins and their complexes with Pr(III) and Yb(III) as water-soluble chiral NMR solvating agents for cationic compounds.

Cyclodextrins that are indiscriminately carboxymethylated at the 2-, 3-, and 6-positions are used as chiral NMR solvating agents for cationic substrates with phenyl, naphthyl, pyridyl, indoline, and indole rings. Enantiodifferentiation with the alpha-, beta-, and gamma-cyclodextrin derivatives is compared. The carboxymethylated derivatives are almost always more effective as chiral NMR solvating agents for cationic substrates than native cyclodextrins. The most effective carboxymethylated cyclodextrin varies for different substrates, and at times even different resonances of the substrate. Addition of paramagnetic praseodymium(III) or ytterbium(III) to mixtures of the carboxymethylated cyclodextrin and substrate often causes enhancements in enantiomeric discrimination and facilitates measurements of enantiomeric purity. The lanthanide ion bonds to the carboxymethyl groups and causes perturbations in the chemical shifts in the NMR spectra of substrate molecules in the cyclodextrin cavity.