A predictive model for salt nanoparticle formation using heterodimer stability calculations

Acid–base clusters and stable salt formation are critical drivers of new particle formation events in the atmosphere. In this study, we explore salt heterodimer (a cluster of one acid and one base) stability as a function of gas-phase acidity, aqueous-phase acidity, heterodimer proton transference, vapor pressure, dipole moment and polarizability for salts comprised of sulfuric acid, methanesulfonic acid and nitric acid with nine bases. The best predictor of heterodimer stability was found to be gas-phase acidity. We then analyzed the relationship between heterodimer stability and J4×4, the theoretically predicted formation rate of a four-acid, four-base cluster, for sulfuric acid salts over a range of monomer concentrations from 105 to 109 molec cm−3 and temperatures from 248 to 348 K and found that heterodimer stability forms a lognormal relationship with J4×4. However, temperature and concentration effects made it difficult to form a predictive expression of J4×4. In order to reduce those effects, heterodimer concentration was calculated from heterodimer stability and yielded an expression for predicting J4×4 for any salt, given approximately equal acid and base monomer concentrations and knowledge of monomer concentration and temperature. This parameterization was tested for the sulfuric acid–ammonia system by comparing the predicted values to experimental data and was found to be accurate within 2 orders of magnitude. We show that one can create a simple parameterization that incorporates the dependence on temperature and monomer concentration on J4×4 by defining a new term that we call the normalized heterodimer concentration, Φ. A plot of J4×4 vs. Φ collapses to a single monotonic curve for weak sulfate salts (difference in gas-phase acidity >95 kcal mol−1) and can be used to accurately estimate J4×4 within 2 orders of magnitude in atmospheric models.

A Predictive Model for Salt Nanoparticle Formation UsingHeterodimer Stability Calculations

Acid–base clusters and stable salt formation are critical drivers of new particle formation events in the atmosphere. In this study, we explore the relationship between J1.5, the theoretically predicted formation rate of clusters larger than 4 acid and 4 base molecules, and acid–base heterodimer stability, a property that is relatively easy to calculate using computational methods. Heterodimer stability as a function of gas-phase acidity, aqueous-phase acidity, heterodimer proton transference, vapor pressure, dipole moment, and polarizability were explored for the salts comprised of sulfuric acid, methanesulfonic acid, and nitric acid with nine bases. The best predictor of heterodimer stability was found to be gas-phase acidity. The relationship between heterodimer stability and J1.5 was analyzed for sulfuric acid salts over a range of monomer concentrations from 105 to 109 molec cm−3 and temperatures from 248 to 348 K. Heterodimer concentration was calculated from heterodimer stability and yielded an expression for predicting J1.5 for any salt, given approximately equal acid and base monomer concentrations and knowledge of monomer concentration and temperature. This parameterization was tested for the sulfuric acid–ammonia system by comparing the predicted values to experimental data and was found to be accurate within 2 orders of magnitude. We show that one can create a simple parameterization that incorporates the dependence on temperature and monomer concentration on J1.5 by defining a new term that we call the normalized heterodimer concentration, Φ. A plot of J1.5 vs. Φ collapses to a single monotonic curve for all weak salts of sulfuric acid, and can be used to accurately estimate J1.5 in atmospheric models.

Extraction of Scandium from Red Mud Using ELM with P204 as Carrier

Scandium is an important rare earth element. Stacking of red mud has caused serious environmental and social issues. Red mud is rich in scandium. In this paper, recovery of scandium from red mud by emulsion liquid membrane (ELM) was studied. Composition of ELM is P204-Span80-sulfonated kerosene-HCl. Effects of mobile carrier and surfactant concentration, Roi, Rwe, internal and external aqueous phase acidity on the extracting rate of Sc3+ were studied. Results show that it is feasible for P204-Span80-Sulfonated Kerosene-HCl ELM System extracting Sc3+ from red mud leaching solution. The optimum condition is P204=12%, Span80=3%, Roi= 2:3, Rwe=6, the internal aqueous c(HCl)= 4mol/L, the external aqueous phase pH=2, the time of making emulsion is 20 minutes, extracting time is 15 minutes. The extracting rate of Sc3+ can reach to 99.6% under optimal condition. The extracting rate of other impurities is lower than 5%.

Recovery of Sc3+ from Red Mud Leaching Solution by Emulsion Liquid Membrane

In this paper, recovery of scandium from red mud leaching solution by emulsion liquid membrane (ELM) was studied. Composition of ELM is P507+ span80 + sulfonated kerosene + HCl. Effects of mobile carrier and surfactant concentration, Roi, Rwe, internal and external aqueous phase acidity on the extracting rate of Sc3+were studied. Results show that it is feasible for ELM extracting Sc3+from the red mud leaching solution. The optimum condition for ELM extracting scandium from the red mud is P507%=8%, Span80%=7%, Roi=2:3, Rwe=6, internal aqueous c(HCl)=2 mol/L, external aqueous phase pH=2. The extracting rate of Sc3+can reach to 98% under optimal condition.

Preparation of U(VI) and Th(IV) α-sources from calcium nitrate solutions by combining solvent extraction and electrodeposition procedures

SummaryA simple method of preparing α-sources for alpha spectrometric analysis of uranium and thorium is investigated by combining solvent extraction and electrodeposition procedures. Extraction of these actinides is performed by diethyl ether from calcium nitrate solution with various nitric acid concentrations. Recoveries of 90–100% are obtained for uranium and 83.5% for thorium. Good resolutions are also achieved under optimum conditions.The dependence of the overall yield of U(VI) and Th(IV) is examined in relation to the aqueous phase acidity. A procedure combining solvent extraction and electrodeposition is proposed for a selective α-source preparation of U(VI) and Th(IV). Uranium is first extracted at pH range about 1 to 2. At this acidity, thorium remains in the aqueous phase and may be subsequently extracted from this after acidification with 2 M HNO