To further determine the fouling behavior of bovine serum albumin (BSA) on different hydrophilic PVDF ultrafiltration (UF) membranes over a range of pH values, self-made atomic force microscopy (AFM) colloidal probes were used to detect the adhesion forces of membrane–BSA and BSA–BSA, respectively. Results showed that the membrane–BSA adhesion interaction was stronger than the BSA–BSA adhesion interaction, and the adhesion force between BSA–BSA-fouled PVDF/PVA membranes was similar to that between BSA–BSA-fouled PVDF/PVP membranes, which indicated that the fouling was mainly caused by the adhesion interaction between membrane and BSA. At the same pH condition, the PVDF/PVA membrane–BSA adhesion force was smaller than that of PVDF/ PVP membrane–BSA, which illustrated that the more hydrophilic the membrane was, the better antifouling ability it had. The extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory predicts that the polar or Lewis acid–base (AB) interaction played a dominant role in the interfacial free energy of membrane–BSA and BSA–BSA that can be affected by pH. For the same membrane, the pH values of a BSA solution can have a significant impact on the process of membrane fouling by changing the AB component of free energy.
Specific second-order rate constants were determined for 5-FU and CAP with ozone.Reaction sites were confirmed by kinetics, Fukui analysis, and products.The olefin moiety was the main ozone reaction site for 5-FU and CAP.Carboxylic acids comprised most of the residual TOC for 5-FU.Ozonation removed the toxicity associated with 5-FU and products but not CAP. Anticancer drugs (ADs) have been detected in the environment and represent a risk to aquatic organisms, necessitating AD removal in drinking water and wastewater treatment. In this study, ozonation of the most commonly used antimetabolite ADs, namely 5-fluorouracil (5-FU) and its prodrug capecitabine (CAP), was investigated to determine reaction kinetics, oxidation mechanisms, and residual toxicity. The specific second-order rate constants between aqueous ozone and 5-FU, 5-FU−, 5-FU2−, CAP, and CAP− were determined to be 7.07(±0.11)×104 M−1·s−1, 1.36(±0.06)×106 M−1·s−1, 2.62(±0.17)×107 M−1·s−1, 9.69(±0.08)×103 M−1·s−1, and 4.28(±0.07)×105 M−1·s−1, respectively; furthermore, the second-order rate constants for •OH reaction with 5-FU and CAP at pH 7 were determined to be 1.85(±0.20)×109 M−1·s−1 and 9.95(±0.26)×109 M−1·s−1, respectively. Density functional theory was used to predict the main ozone reaction sites of 5-FU (olefin) and CAP (olefin and deprotonated secondary amine), and these mechanisms were supported by the identified transformation products. Carboxylic acids constituted a majority of the residual organic matter for 5-FU ozonation; however, carboxylic acids and aldehydes were important components of the residual organic matter generated by CAP. Ozone removed the toxicity of 5-FU to Vibrio fischeri, but the residual toxicity of ozonated CAP solutions exhibited an initial increase before subsequent removal. Ultimately, these results suggest that ozone is a suitable technology for treatment of 5-FU and CAP, although the residual toxicity of transformation products must be carefully considered. 相似文献
This study focuses on providing a direct insight into the process by which sulfate is formed on mineral dust surface in the
actual atmosphere. Six sets of aerosol measurements were conducted in the outskirts of Beijing, China, in 2002–2003 using
a tethered balloon. The mineralogy of individual dust particles, as well as its influence on the S (sulfur) loadings was investigated
by SEM-EDX analysis of the directly collected particles.
The mixed layer in the urban atmosphere was found to be quite low (500–600m), often appearing as a particle dense stagnant
layer above the surface. It is suggested that mineral dust is a common and important fraction of the coarse particles in Beijing
(35–68%), and that it is relatively enriched with Calcite (>28%).
An exceptional amount of S was detected in the mineral particles, which can be explained neither by their original composition,
nor by coagulation processes between the submicron sulfates and the dust. Heterogeneous uptake of gaseous SO2, and its subsequent oxidation on dust was suggested as the main pathway that has actually taken place in the ambient environment.
The mineral class found with the largest number of particles containing S was Calcite, followed by Dolomite, Clay, Amphibole
etc., Feldspar, and Quartz. Among them, Calcite and Dolomite showed distinctly higher efficiency in collecting sulfate than
the other types.
A positive correlation was found with the number of S containing particles and the relative humidity. Calcite in particular,
since almost all of its particles was found to contain S above 60% r.h. On the other hand, the active uptake of SO2 by the carbonates was not suggested in the free troposphere downwind, and all the mineral classes exhibited similar S content.
Relative humidity in the free troposphere was suggested as the key factor controlling the SO2 uptake among the mineral types. In terms of sulfate loadings, the relationship was not linear, but rather increased exponentially
as a function of relative humidity. The humidity-dependent uptake capacity of mineral types altogether showed an intermediate
value of 0.07 gSO42− g−1 mineral at 30% r.h. and 0.40 gSO42− g−1 mineral at 80%, which is fairly consistent with laboratory experiments. 相似文献
