George P. Gallios

Nanostructures in environmental pollution detection, monitoring, and remediation

abstract We present preliminary results of our joint investigations to monitor and mitigate environmental pollution, a leading contributor to chronic and deadly health disorders and diseases affecting millions of people each year. Using nanotechnology-based gas sensors; pollution is monitored at several ground stations. The sensor unit is portable, provides instantaneous ground pollution concentrations accurately, and can be readily deployed to disseminate real-time pollution data to a web server providing a topological overview of monitored locations. We are also employing remote sensing technologies with high-spatial and spectral resolution to model urban pollution using satellite images and image processing. One of the objectives of this investigation is to develop a unique capability to acquire, display and assimilate these valuable sources of data to accurately assess urban pollution by real-time monitoring using commercial sensors fabricated using nanofabrication technologies and satellite imagery. This integrated tool will be beneficial towards prediction processes to support public awareness and establish policy priorities for air quality in polluted areas. The complex nature of environmental pollution data mining requires computing technologies that integrate multiple sources and repositories of data over multiple networking systems and platforms that must be accurate, secure, and reliable. An evaluation of information security risks and strategies within an environmental information system is presented. In addition to air pollution, we explore the efficacy of nanostructured materials in the detection and remediation of water pollution. We present our results of sorption on advanced nanomaterials-based sorbents that have been found effective in the removal of cadmium and arsenic from water streams.

Flotation of Salt-Type Minerals

Salt-type minerals flotation is discussed, based mainly on experiments on magnesite, dolomite and calcite. Among the parameters affecting flotation, the following are examined : crystal structure, solubility of minerals, surface charge, collectors, organic and inorganic modifiers, adsorption, contact angle and floatability. The selective separation by flotation of salt-type minerals from each other and from silicates is also investigated.

Separation of fines by flotation techniques

Abstract A large amount of valuable minerals is discarded today as fines and ultrafines because of inadequate technology to process them economically. Treatment of fine particles presents a difficult problem in the chemical industry and raw materials processing, and its solution is required both in production and effluent treatment. This article reviews various suitable flotation techniques—such as precipitate flotation, flocculation-flotation, column flotation, dissolved-air flotation, and electrolytic flotation and presents different laboratory experiments with fines (mostly at the subsieve size range) as examples. Also included is the conventional froth flotation and particularly the effect of bubbles size on performance. Although froth flotation is a commonly applied selective separation process in mineral processing, it becomes inefficient for beneficiating fines. In the closing overview of the process, several ideas for future research are suggested.

Removal of cadmium, zinc, copper and lead by red mud, an iron oxides containing hydrometallurgical waste

Abstract Red mud, a residue of the alumina production industry which is actually a solid waste, has been studied as a potential sorbent for the removal of toxic bivalent cations (i.e. Cd, Zn, Cu and Pb) from aqueous solutions in the presence of 0.01 M NaNO3. The experimental data were modeled with Langmuir and Freundlich isotherms and fitted quite well. The relatively high uptake indicated that red mud can adsorb considerable amounts of cadmium and zinc from near-neutral aqueous solutions (maximum uptake capacity for cadmium: 68 mg-g1 at pH 6 and ca. 133 mg-g1 for zinc at pH 7). A significant uptake was also observed for copper and lead at pH 6 and 7 respectively which was attributed to precipitation of the respective insoluble hydroxides. TCLP leaching tests before and after the metal removal have shown that read mud is an environmentally compatible material that could be used for the wastewater treatment. Regeneration possibilities have also been observed.

Uranium sorption on amorphous titanium and zirconium phosphates modified by Al3+ or Fe3+ ions

The sorption of uranium from aqueous solutions on titanium and zirconium phosphates in H+ and K+ forms modified by iron or aluminum ions has been investigated. The modified pattern of porosity is much better, than for none modified analogous, owing to their increased sorption capacity and kinetics of uranium absorption. The modified sorbents display selectivity towards uranium, that allows to purify solutions up to the content of uranium below the limit of its analytical definition.

Mineral processing and the environment

Preface. Fundamentals. Hydrophobic Agglomeration of Fine Particles Z. Sadowski. Electrokinetic Behaviour of Sulphide Minerals: A Contribution to the Chemistry of Flotation G.P. Gallios, et al. Bacterial Leaching of Minerals F.J. Garcia Frutos. Legal Framework for Environmental Protection in Mineral Processing Activities A. Turkman, H. Mordogan. Environmental Pollution and Prevention. Air-Pollutant Emissions and Imissions from Metallurgical Industry E. Vircikova, J. Macala. Electrochemical Approach to Pollutants Removal and Destruction C.A.C. Sequeira. Electrohydrometallurgical Recovery of Cadmium and Nickel from Spent Batteries C.A.C. Sequeira. The Treatment of Radioactive Liquid Wastes and the Problems Connected with the Long Term Storage of Radioelements C. Loos-Neskovic. Removal and Recovery of Metals from Dilute Solutions: Applications of Flotation Techniques K.A. Matis, et al. Separation Processes. Desulphurization of Coal to Protect the Environment G. Ozbayoglu. Extraction of Priority Pollutants Using Inorganic Ion Exchangers M.J. Hudson. Arsenic Removal from Effluents of Copper Plants V. Nenov, et al. Hydrometallurgy of Precious Metals: Effects on the Environment S.S. Gaydardiev. New Developments in the Processing of Chromite Tailings M.Z. Dogan, et al. Innovative Techniques. Recycling of Plastics: Application of Flotation J. Frenay, et al. Mineral Processing Technology Applied to the Remediation of Contaminated Soils G.J.P. Morizot. Electroflotation in Waste Water Treatment: Results and Perspectives A.M. Romanov. The Biosorption Process: An Innovation in Reclamation of Toxic Metals A.I. Zouboulis, K.A. Matis. List of Contributors. List ofParticipants. Index.

Dissolved — Air and Electrolytic Flotation

The problem of processing mineral fine particles poses an immense challenge today. The application of conventional methods is generally uneconomical. Among the new flotation techniques that could be possibly applied , two of them — namely dissolved-air flotation and electrolytic flotation — are described and reviewed. Both of them have principally come from effluent treatment and are characterised by the production of fine gas bubbles. Operation and design aspects are discussed and different applications are examined , among them , laboratory experimental results on the flotation of carbonates. In the introduction , the problem of fines is briefly referred to, with emphasis on the role of particle and bubble size.

MODIFICATION OF PYRITE AND SPHALERITE FLOTATION BY DEXTRIN

Abstract The role of dextrin in the xanthate flotation of pyrite and sphalerite was examined by means of flotation tests and microelectrophoretic measurements. Floatability and ζ-potential of both minerals were found to be depressed in a suitable pH range due to the formation of their respective superficial metal hydroxide layers. The influences of surface oxidation and flocculation of mineral particles were also discussed. The selective flotation of sphalerite from pyrite in an acidic medium in the presence of copper sulfate was found to be possible, as shown by artificial mixture separation studies. In this way, the possible exclusion of cyanides (for environmental reasons) may be advanced.

Processing of magnesium carbonate fines by dissolved-air flotation

Abstract Dissolved-air flotation of natural magnesite and dolomite fine particles (at the sub-sieve size range) was undertaken for their selective recovery. A commercial fatty acid was used as anionic collector in a batch cell, at different pH values. The application of modifiers, such as carboxymethyl cellulose, sodium hexametaphosphate and sodium pyrophosphate, was examined together with zeta-potential measurements. After the laboratory separation experiments with the pure salt-type minerals, the differential separation of artificial mixtures was carried out in the presence of modifiers, at the optimum conditions, to give promising results especially in reverse flotation of magnesite.

Anionic flotation of magnesium carbonates by modifiers

Abstract Laboratory research has been carried out on the selective separation of magnesite and dolomite by flotation, applying sodium oleate as collector. These industrial minerals exhibit similar flotation behaviour and hence, modifying agents (sodium silicate, fluorosilicate and Calcon) have also been added. Preliminary work involved the study of the effect of conditioning time on pH, due to solubility, and the effects of collector concentration, pH of solution and hard water. Experiments on artificial mixtures of magnesite/dolomite followed, with classical flotation at an alkaline pH.