Lorenzo Reyes-Bozo

Characterization and remediation of contamination: the influences of mining and other human activities

There are many definitions of the term contamination. Jefferis (2002 p. 75) provided the simple definition Bcontamination is a chemical, a living organism or energy in the wrong place.^ Paraphrasing this definition, contamination is the presence of an unwelcome component in a material, physical body, place, or other entity. In the natural environment, contamination implies that an exotic constituent that generally poses risks to biota living in that environment, particularly humans, has been introduced to the environment. Humans produce most contaminants, and cause many elements and compounds to be released into natural waters, soil, and the atmosphere that can then enter the human food chain. These elements and compounds are commonly called potentially harmful (or toxic) elements. Potentially harmful elements can have a very wide range of characteristics and origins. Potentially harmful elements can be heavy metals or metalloids (e.g., As, Cd, and Hg) released during mining or other industrial activities, or they can be organic compounds, such as medications (the excess of which can be released when they are used in clinical treatments). A very wide range of factors therefore affect contamination, and this variety affects the methods that are used to study and assess contamination processes and the methods that can be used to decrease the impacts of contaminants on the environment and human health. Some of the most important questions about contamination are related to the potential of potentially harmful elements to cause real health effects in the general population. Most contamination is caused by industrial processes, in mines and factories, for instance. However, the risks posed to workers in mines and factories are (or should be) generally controlled and minimized because they are known risks. However, improperly controlled gases and/or liquids containing potential contaminants can be released into the surrounding environment and affect local inhabitants. Potential risks need to be assessed taking into account processes that affect the mobilities and, in particular, the bioavailabilities of the contaminants present. Regional, national, and international regulators have introduced legislation in which maximum amounts of contaminants that can be released into the environment for any reason have been set. However, very limited success has been achieved in holding governments or individuals responsible for emissions of greenhouse gases, which are considered to be the primary causes of anthropogenic climate change (Zeben 2015). It is also necessary to take into consideration the chemical forms in which contaminants are released. For example, mercury is considered to be a potentially harmful element, but it is necessary to know which form of mercury is present in the environment or in a product that is released to assess properly the potential for mercury to cause toxic effects. The potential for toxic effects Responsible editor: Philippe Garrigues

In-Situ FTIR Kinetic Study in the Silylation of Low-k Films with Hexamethyldisilazane Dissolved in Supercritical CO2

In-situ Fourier transform infrared spectroscopy measurements were obtained by using an innovative equipment to study the heterogeneous reaction between a hydrolyzed porous methylsilsesquioxane film and hexamethyldisilazane (HMDS) dissolved in CO2 at supercritical conditions. Gas and solid infrared signatures were separated to obtain kinetic information of the heterogeneous reaction. A two-step reaction mechanism was observed: a fast first step controlled by kinetics and a second step controlled by the diffusion of the HMDS inside the porous material. Infrared information was used to derive a rate law expression of the silylation reaction between HMDS and Si-OH. A first order of reaction relative to the concentration of hydrophilic sites was observed with activation energy of 51.85 ± 1.25 kJ/mol.

Surfactant properties of humic acids extracted from volcanic soils and their applicability in mineral flotation processes

Surface Tension (ST) of water solutions of humic acids extracted from volcanic ash derived soils (soil humic acids, S-HA), were measured under controlled conditions of pH (13.0), temperature (25 °C) and ionic strength (NaOH 0.1M) to establish the Critical Micellar Concentration (CMC). All S-HA were characterized by elemental analysis, acid-base titration, Transmission Electronic Microscopy (TEM) micrographs, isoelectric point (IEP) and solid state 13C-NMR. After that, these humic acids were evaluated as potential biomaterials to be used in mineral flotation processes, where a series of experiments were conducted at different S-HA and molybdenite ratio (from 0.2 to 50 g ton-1) establishing the IEP of all resultant materials. The use of solid state 13C-NMR enabled the following sequence of intensity distribution areas of S-HA to be established: O/N Alkyl>Alkyl C>Aromatic C>Carboxyl. The experimental values of ST and the calculated CMC (ranging from 0.8 to 3.3 g L-1) revealed that for S-HA no relationship between the abundance groups and their behavior as surfactant materials was observed. In relation with IEP determined for all materials, the highest surface charge, which can be useful for flotation processes, was obtained with 0.2 g of S-HA per ton of molybdenite. Additionally, TEM studies confirm the formation of pseudoaggregates for all the S-HA considered. Finally, the S-HA could be considered as an alternative to chemical products and commercial humic acids materials in mineral flotation processes.

Study of Low-k Film Functionalization and Pore Sealing Using Chlorosilanes Dissolved in Supercritical Carbon Dioxide

Surface functionalization of hydrolyzed methyl-silsesquioxane films were performed by treatment of samples with trimethylchlorosilane (TMCS) and methyltrichlorosilane (MTCS) dissolved in supercritical carbon dioxide. Films thicknesses modifications, pore size distributions, hydrophobicity, dielectric constants, and chemical reaction analyses were performed by ellipsometry, ellipsometric porosimetry, goniometry, electrical measurements, and Fourier transform infrared spectroscopy, respectively. As results, the properties of the functionalized films were able to be modified in function of reaction conditions (concentration, temperature, and/or pressure). Layers thicker than a monolayer were deposited by both TMCS and MTCS, and a tradeoff between the surface functionalization and layer thickness for both chemicals was observed. The results led to the conclusion that a combination of reagents or processing steps could be used for surface properties tuning.

Environmental-Microbial Biotechnology Inside Mining Operations from an Engineering Viewpoint Based on LCA

The relationship between the mining industry, society, and environment has been historically complex due to the number and scale of operational impacts. Today, the mining sector is at a tipping point to achieve equilibrium between high levels of production and minimizing environmental impacts. A feasible and novel approach to solve this need is the incorporation of concepts from industrial ecology to mining processes. Such approach could support an integrated management of materials available inside mine plants delivered by other industrial and depurative activities. Mining operations tend to be characterized as a conservative industry with few opportunities to innovate particularly with consideration to the application of microbial biotechnology at a large scale inside mineral processing plants, waste treatment, and ore recovery limited to bio-hydrometallurgical processing (e.g., Biolixiviation).

Soil pollution related to mercury-mining activities in the proximity of Usagre (Badajoz, SW Spain)

Usagre (Badajoz, SW Spain) mercury mine was active for an undetermined time until its closure in 1971. The ore exploited in this mine was cinnabar (red HgS), and metallurgy was also performed locally by means of primitive furnaces of the Bustamante type. Since the closure of the mine, reclamation measures have not been carried out at the site, and actual passives include a mine shaft, an accessible descending gallery and a mine dump adjacent to the descending gallery. In the work described here, data from two soil geochemistry surveys were combined and analysed. The surveys were separated by a period of 32 years. Measurements of total gaseous mercury (TGM) in the underground mine and its surroundings were also considered. The soil geochemistry included mercury, lead, zinc and copper. The results indicate that soil pollution is mostly related to the trace mineralisations on the surface and they can therefore be interpreted as natural geochemical anomalies. TGM concentrations are extremely high inside the mine but are of very low concern outside the mine.