Duoqiang Pan

Interactions between Silicon Oxide Nanoparticles (SONPs) and U(VI) Contaminations: Effects of pH, Temperature and Natural Organic Matters

The interactions between contaminations of U(VI) and silicon oxide nanoparticles (SONPs), both of which have been widely used in modern industry and induced serious environmental challenge due to their high mobility, bioavailability, and toxicity, were studied under different environmental conditions such as pH, temperature, and natural organic matters (NOMs) by using both batch and spectroscopic approaches. The results showed that the accumulation process, i.e., sorption, of U(VI) on SONPs was strongly dependent on pH and ionic strength, demonstrating that possible outer- and/or inner-sphere complexes were controlling the sorption process of U(VI) on SONPs in the observed pH range. Humic acid (HA), one dominated component of NOMs, bounded SONPs can enhance U(VI) sorption below pH~4.5, whereas restrain at high pH range. The reversible sorption of U(VI) on SONPs possibly indicated that the outer-sphere complexes were prevalent at pH 5. However, an irreversible interaction of U(VI) was observed in the presence of HA (Fig 1). It was mainly due to the ternary SONPs-HA-U(VI) complexes (Type A Complexes). After SONPs adsorbed U(VI), the particle size in suspension was apparently increased from ~240 nm to ~350 nm. These results showed that toxicity of both SONPs and U(VI) will decrease to some extent after the interaction in the environment. These findings are key for providing useful information on the possible mutual interactions among different contaminants in the environment.

Effects of pH, ionic strength, humic substances and temperature on Th(IV) sorption onto ZSM-5

We report the influencing factor of pH, ionic strength, temperature and humic acids on the chemical affinity of Zeolite Socony Mobil (ZSM)-5 with Th(IV), which was determined by batch technique under ambient conditions. The sorption of Th(IV) on ZSM-5 was strongly dependent on pH values and temperature whereas the influence of ionic strength was weak. The sorption of Th(IV) on ZSM-5 zeolite was exothermic process. Further, for strong complex ability of Th(IV)-HA/FA at low pH, the effects of humic acid (HA) and fulvic acid (FA) were positive and negative at higher pH.

Sorption behavior of thorium(IV) onto activated bentonite

Activated bentonite was obtained from acid activation and purification of raw bentonite, sorption of Th(IV) onto activated bentonite was studied by batch experiments. Characterization of activated bentonite and sorption behavior of Th(IV) demonstrated that Th(IV) could quickly absorbed on activated bentonite, and kinetic process fitted well with the pseudo-second-order model. Sorption percentage of Th(IV) on activated bentonite strongly depended on pH, background anion, ionic strength and temperature, which indicated surface complexation was the main sorption mechanism, physisorption and ion-exchange as secondary factors also participated in sorption processes. The results showed activated bentonite was an efficient material for Th(IV) sorption.

beta-Zeolite modified by ethylenediamine for sorption of Th(IV)

beta-Zeolite-EDA was modified with ethylenediamine (EDA) after synthesized. The synthesized material was characterized and used for removal of Th(IV) from aqueous solutions. The influences of pH, ionic strength, contact time, temperature and humic acid (HA) on Th(IV) sorption onto synthesized beta-zeolite-EDA was studied by batch technique. The dynamic process showed that the sorption of Th(IV) onto beta-zeolite-EDA matched the pseudo-second-order kinetics model. The sorption of Th(IV) on beta-zeolite-EDA was significantly dependent on pH values, the sorption percentage increased markedly at pH 3.5-4.5, and then maintained a steady state as pH values increased. Through simulating the sorption isotherms by Langmuir, Freundlich and Dubini-Radushkevich (D-R) models, it could be seen respectively that the sorption pattern of Th(IV) on beta-zeolite-EDA was mainly controlled by surface complexation, and that the sorption processes was endothermic and spontaneous. The presence of HA increased Th(IV) sorption on beta-zeolite-EDA.

Effect of MWCNTs on Gastric Emptying in Mice.

After making model of gastric functional disorder (FD), part of model mice were injected intravenously (i.v.) with oxide multi-walled carbon nanotubes (oMWCNTs) to investigate effect of carbon nanotubes on gastric emptying. The results showed that NO content in stomach, compared with model group, was decreased significantly and close to normal level post-injection with oMWCNTs (500 and 800 μg/mouse). In contrast to FD or normal groups, the content of acetylcholine (Ach) in stomach was increased obviously in injection group with 500 or 800 μg/mouse of oMWCNTs. The kinetic curve of emptying was fitted to calculate gastric motility factor k; the results showed that the k of injection group was much higher than FD and normal. In other words, the gastric motility of FD mice was enhanced via injection with oMWCNTs. In certain dosage, oMWCNTs could improve gastric emptying and motility.

Retardation of hexavalent uranium in muscovite environment: a batch study

Abstract The sorption of hexavalent uranium on muscovite as a function of pH, background electrolyte, temperature and humic acid (HA) was investigated in detail using batch experiments. The results showed that the uranium sorpiton on muscovite was kinetic fast, the kinetic process was fitted well by pseudo-second-order kinetic model. The sorption of uranium depended strongly on pH while weakly on background electrolyte concentration, indicating that surface complexation dominated the sorption process. The escalation of temperature and humic acid concentration were favorable to uranium sorption on muscovite. The sorption isotherms at pH 6.0 could be described better by Langmuir model than Freundlich or Dubinin-Radushkevich (D-R) model, thermodynamic data indicated that the uranium sorption process on muscovite was spontaneous and endothermic process. The findings in present work can provide important experimental reference for understanding the environmental behavior of uranium in mica-rich terrains.

Sorption of Eu(III) at feldspar/water interface: effects of pH, organic matter, counter ions, and temperature

Abstract The sorption of Eu(III) on potassium feldspar (K-feldspar) was studied under various physicochemical conditions such as pH, temperature, counter ions and organic matter. The results showed that the sorption of Eu(III) on K-feldspar significantly increased with the increase of pH, and high Eu(III) concentration can inhibit such immobility to some extent. The presence of humic acid (HA) can increase the sorption of Eu(III) on K-feldspar in low pH range; while inhibit to a large extent under alkaline conditions. It is very interesting that at pH ~6.5, high ionic strength can promote the sorption of Eu(III) on K-feldspar in the presence of HA. In contrast, Eu(III) sorption was restricted obviously by NaCl in the absence of HA. The sorption procedure was involved with ion exchange and/or outer-sphere complexation as well as inner-sphere complexation. The presence of F− and PO43− dramatically enhanced Eu(III) sorption on K-feldspar, whereas both SO42− and CO32− had negative effects on Eu(III) sorption. X-ray photoelectron spectroscopy analysis indicated that Eu(III) tended to form hydrolysates at high initial concentration (3×10−4 mol/L) and high temperature (338 K).