Occurrence, behavior and effects of nanoparticles in the environment.

1: Magnetic Particles: Preparation, Properties and Applications: M. Ozaki. 2: Maghemite (gamma-Fe2O3): A Versatile Magnetic Colloidal Material C.J. Serna, M.P. Morales. 3: Dynamics of Adsorption and Oxidation of Organic Molecules on Illuminated Titanium Dioxide Particles Immersed in Water M.A. Blesa, R.J. Candal, S.A. Bilmes. 4: Colloidal Aggregation in Two-Dimensions A. Moncho-Jorda, F. Martinez-Lopez, M.A. Cabrerizo-Vilchez, R. Hidalgo Alvarez, M. Quesada-PMerez. 5: Kinetics of Particle and Protein Adsorption Z. Adamczyk.

Surface and Colloid Science

Developments in nanotechnology are leading to a rapid proliferation of new materials that are likely to become a source of engineered nanoparticles (ENPs) to the environment, where their possible ecotoxicological impacts remain unknown. The surface properties of ENPs are of essential importance for their aggregation behavior, and thus for their mobility in aquatic and terrestrial systems and for their interactions with algae, plants and, fungi. Interactions of ENPs with natural organic matter have to be considered as well, as those will alter the ENPs aggregation behavior in surface waters or in soils. Cells of plants, algae, and fungi possess cell walls that constitute a primary site for interaction and a barrier for the entrance of ENPs. Mechanisms allowing ENPs to pass through cell walls and membranes are as yet poorly understood. Inside cells, ENPs might directly provoke alterations of membranes and other cell structures and molecules, as well as protective mechanisms. Indirect effects of ENPs depend on their chemical and physical properties and may include physical restraints (clogging effects), solubilization of toxic ENP compounds, or production of reactive oxygen species. Many questions regarding the bioavailability of ENPs, their uptake by algae, plants, and fungi and the toxicity mechanisms remain to be elucidated.

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Environmental behavior and ecotoxicity of engineered nanoparticles to algae, plants, and fungi

Colloid mobilization and transport in groundwater

Although progress has recently been made toward understanding the health and environmental consequences of these materials, challenges ramain for future research.

http://pubs.acs.org/doi/pdf/10.1021/es062726m

Assessing the risks of manufactured nanomaterials.

Etudes de l'adsorption des ions oxalate et citrate sur des particules spheriques colloidales d'hematite et de leur influence sur l'elimination du fer a partir de celles-ci, en fonction de la concentration du solute, du pH et de la temperature

Interaction of metal hydrous oxides with chelating agents. 7. Hematite-oxalic acid and -citric acid systems

Stability of nanodispersions: a model for kinetics of aggregation of nanoparticles.

Mass titration method was developed as a suitable tool for determination of the point of zero charge (p.z.c.) and surface charge density (σ 0 ) of metal oxide colloid particles at different ionic strengths. In the course of mass titration, subsequent portions of a metal oxide powder are added to an aqueous electrolyte solution, and pH of the equilibrated dispersion is measured. The pH of the system changes gradually and approaches a constant value of pH ∞ , which is in the case of a metal oxide free of impurities equal to the point of zero charge pH pzc . Counterion association shifts the pH pzc either to the acidic region (preferential adsorption of cations) or to the basic region (preferential adsorption of anions). Mass titration therefore enables detection of the difference between association affinities of counterions (cations and anions), which is important information about the equilibrium within the electrical interfacial layer. Such an analysis is not possible by the conventional acid-base potentiometric titration of the dispersion, since the location of the p.z.c. is based on the common intersection point (c.i.p.) of the data obtained at different ionic strengths. It is shown that c.i.p. may be used for locating the p.z.c. only in a asymmetric case«, when affinities of the anions and cations to associate with oppositely charged surface groups are equal. Analysis of the mass titration was performed on the basis of experimental data obtained with colloidal titania dispersed in an aqueous sodium chloride solution, and also by numerical simulation based on the Surface Complexation Model and the 2-pK mechanism of surface reactions. Increase in the NaCI concentration shifted the point of zero charge to the basic region, while the isoelectric point was shifted to the acidic region, indicating higher association affinity of chloride ions compared to sodium ions.

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Point of Zero Charge and Surface Charge Density of TiO2 in Aqueous Electrolyte Solution as Obtained by Potentiometric Mass Titration

This article summarizes methods for determining proton surface charge at mineral/water inter- faces. It covers conventional experimental procedures and discusses problems with the techniques. Also it involves recommendations for obtaining reasonable and comparable results. The term "comparable re- sults" refers to comparison between results for the same solid as obtained in different laboratories. The most important parameters for the surface titrations are discussed. We also propose a reference titration procedure that would allow direct, unbiased comparisons of experimental data. The article finally includes a check-list for researchers and reviewers which should allow limiting the amount of titration data that are not useful for future uses. (doi: 10.5562/cca2062)

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Potentiometric Titrations as a Tool for Surface Charge Determination

Analyse en termes de modele de complexation en surface, des donnees d'adsorption des acides oxalique et citrique sur des particules d'hematite colloidale, dispersees dans l'eau. Evaluation des contributions chimique et electrostatique et determination des especes de solute qui reagissent avec le solide

Nikola Kallay

Papers

Interaction of metal hydrous oxides with chelating agents. 7. Hematite-oxalic acid and -citric acid systems

Stability of nanodispersions: a model for kinetics of aggregation of nanoparticles.

Point of Zero Charge and Surface Charge Density of TiO2 in Aqueous Electrolyte Solution as Obtained by Potentiometric Mass Titration

Potentiometric Titrations as a Tool for Surface Charge Determination

Adsorption at solid/solution interfaces. 1. Interpretation of surface complexation of oxalic and citric acids with hematite