Modeling of the Competition between Uranyl Nitrate and Nitric Acid upon Extraction with Tri-n-butyl Phosphate.

Uranium is a strategic element and plays an important role in energy resources. A H2O-HNO3-UO2(NO3)2-TBP (tri-n-butyl phosphate)-diluent system is commonly used for uranium separation and purification in liquid-liquid extraction. Uranyl nitrate is promoted by the existence of nitrate at low HNO3 concentrations but is inhibited at high HNO3 concentrations. Considering the competitive extraction between HNO3 and UO2(NO3)2, a generic extraction model is developed. The activities of components in the aqueous phase were estimated using Pitzer models. The thermodynamic equilibrium constants and Pitzer parameters were regressed by experimental data. The resulting model was able to successfully predict uranyl nitrate, nitric acid, and water extraction over a large range of conditions (U, 0-1.8 mol/L; HNO3, 0-10 mol/L; TBP, 5-100 vol %) within average absolute relative deviations of 11.2, 15.7, and 23.8%, respectively. The predicted results show that water and nitric acid were extracted as di-solvates HNO3·(TBP)2·H2O and (TBP)2·2H2O at low nitric acid concentrations, with the formation of mono-solvates HNO3·TBP and HNO3·TBP·H2O as the acid concentration increased. Uranyl nitrate was shown to be rejected from the organic phase as the formation of HNO3·TBP and HNO3·TBP·H2O in acid was extracted at high acid concentrations.

Application of a Sustainable Bioderived Solvent (Biodiesel) for Phenol Extraction.

Replacement of volatile organic compound solvents by greener or more environmentally sustainable solvents is becoming increasingly important due to the increasing health and environmental concerns. In the present work, a bioderived solvent, soybean oil methyl ester, which is better known as biodiesel and is a nonvolatile organic compound, was used as a solvent to replace the fossil solvent (kerosene) for phenol extraction. First, biodiesel was selected as an optional solvent to replace kerosene based on Hansen solubility parameter calculation results. Second, the effects of solvent concentration, equilibrium pH of the aqueous phase, temperature, extraction time, etc. on phenol extraction were examined. The results show that biodiesel has strong extraction ability on phenol extraction than that of kerosene. An acidic environment decreases the phase disengagement time. Phenol extraction reached equilibrium in 30 s of contact time at room temperature. McCabe-Thiele diagram calculation results show that the phenol extraction efficiency can reach 98% in three theoretical stages at an A/O ratio of 10:1 (Cyanex923 + biodiesel). Finally, the extraction mechanism indicated that biodiesel could reduce the intermolecular hydrogen bond forces in the extractant so as to improve the extraction efficiency.

Identification and characterization of broadly cross-reactive neutralizing antibodies in patients infected with HIV-1 B'/C recombinant (CRF07_BC).

The identification of broadly cross-reactive neutralizing (BCN) antibodies is essential for the development of a more universally effective vaccine for human immunodeficiency virus (HIV). In this study, CRF07_BC serum was analyzed for cross-clade antibody reactivity and neutralization. A total of 117 HIV-1 sera (CRF07_BC) were screened for their capacity to neutralize three primary HIV-1 isolates. A total of 18 out of 117 sera cross-neutralized all three viruses, and were tested along with eight randomly selected non-BCN sera against seven primary HIV-1 isolates and two laboratory strains that represented different clades and tropisms. BCN sera neutralized eight or all nine of these primary isolates. Non-BCN sera did not display any broadly cross-reactive neutralizing responses. BCN sera neutralized with higher frequency and geometric mean titers compared to non-BCN sera. Sera from asymptomatic individuals on average neutralized a significantly greater number of the three key isolates than sera from symptomatic individuals. Our data indicate that the three HIV-1 isolated strains are sufficient to screen broad cross-neutralizing sera, and that BCN responses may contribute to protection from infection and disease progression. The neutralizing antibody response demonstrated extensive cross-neutralization, suggesting that neutralizing antibodies induced by vaccines will have a relatively low epitope diversity to overcome in patients infected with HIV-1 B'/C recombinant (CRF07_BC).

Association of variations of NAb 2F5 and 4E10 epitopes and disease progression in Chinese antiretroviral treatment-naïve patients infected with HIV-1 clade B'.

BACKGROUND: Studies on human immunodeficiency virus type 1 (HIV-1) vaccines have recently focused on targeting the conserved neutralizing epitopes 2F5 and 4E10, and hence it is important to understand the extent of mutations in these two viral epitopes. Here, we investigated the amino acid mutations in epitopes of 2F5 (ELDKWA, HIV-1 HXB2 env 662 - 667 aa) and 4E10 (NWFDIT, HIV-1 HXB2 env 671 - 676 aa) in the membrane proximal-external region of gp41 from clade B' HIV-1-infected individuals living in Henan province, China. We also examined the frequency of a mutation and its relation to disease progression. METHODS: A cohort of 54 treatment-naïve HIV-1-infected individuals was recruited in this study, and 16 individuals were selected for a short-term longitudinal study on sequence evolution. The HIV-1 env gp41 gene was amplified, cloned, and sequenced, and predicted amino acid sequences were aligned for analysis. RESULTS: The mutations E662A and K665E on the 2F5 epitope and N671S and T676S on the 4E10 epitope were seen. Simultaneous RNA sequencing showed some discrepancies with proviral DNA sequences. In our longitudinal study, mutation levels of these two neutralizing epitopes were low but diverse and persistent. The frequencies of mutations within the 4E10 peptide NWFDIT in slow progressors were noticeably lower than those in AIDS patients (P < 0.05). CONCLUSIONS: Antigenic variation of the neutralizing epitopes 2F5 and 4E10 is limited in subtype B' infection, and that 4E10 peptide mutation is correlated with disease progression. Monitoring epitope mutations will offer useful data for development of the candidate 2F5-like and 4E10-like antibodies to prevent and treat AIDS.