Trace metal removal

Fig. 15-5 Comparative adsorption of several metals onto amorphous iron oxyhydroxide systems containing 10 M Fej and 0.1 m NaNOs. (a) Effect of solution pH on sorption of uncomplexed metals, (b) Comparison of binding constants for formation of soluble Me-OH complexes and formation of surface Me-O-Si complexes i.e. sorption onto Si02 particles, (c) Effect of solution pH on sorption of oxyanionic metals. (Figures (a), (c) reprinted with permission from Manzione, M. A. and Merrill, D. T. (1989). "Trace Metal Removal by Iron Coprecipitation Field Evaluation," EPRI report GS-6438, Electric Power Research Institute, California. Figure (b) reprinted with permission from Balistrieri, L. et al. (1981). Scavenging residence times of trace metals and surface chemistry of sinking particles in the deep ocean, Deep-Sea Res. 28A 101-121, Pergamon Press.)...

Trace Metal Removal from Aqueous Solution... 

Woodhouse, G., in Trace Metal Removal from Aqueous Solution, Thompson, R., Ed., Royal Society of Chemistry, London, 1986. 

This has been whimsically described as the Great Particle Conspiracy. An important set of these processes involves the incorporation of trace metals into biogenic hard and soft parts. Another involves the adsorption of metals onto the surfaces of particles. Although some metals can theoretically be removed by abiotic precipitation into mineral phases, continuing research confirms that most of the trace metal removal is biologically mediated. 

Oliver [190] recommends the dissolution of the polymer if possible (see above) but in other cases a wet ashing procedure was used. The sample was heated with 2—3 ml of concentrated sulphuric acid and then hydrogen peroxide added drop-wise until the organic matter was destroyed. Twenty elements were determined in a 2% solution of polymer. Polymers may be dispersed in an organic solvent and trace metals removed by leaching with an appropriate aqueous solution, preferably the procedure should be repeated more than once to ensure complete extraction. To determine antimony in fire-retardant polypropylene, the sample was dispersed in xylene and extracted with 6M hydrochloric acid under reflux [191]. The filtered acid layer was combined with two further extracts prior to aspiration into the air/acetylene flame and measurement at 217.6 nm. Martinie and Schilt [45] reported that nylon would dissolve completely in perchloric/nitric acid digestion but potentially explosive problems were encountered in the dissolution of Amberlite resins and rubber. 

Removal of trace metals from liquid streams is not new and has been accomplished using as ion-exchange resin, seen in Fig. 19.2, which has been used in the water purification industry since the 1940s [13-16]. Most of the challenges associated with CMP waste treatment center around pretreating the waste stream prior to the trace metals removal step. Once the waste stream has been properly conditioned, it becomes a matter of removing the trace metal contaminants. For metals removal in CMP, cation resins are used. 

There are numerous commercially available CMP wastewater treatment system technologies on the market today. All of the system suppliers strive for cost-effective trace metals removal and maximum water recovery, but may differ on how they address solids control and oxidizer removal. It is a... 

Snoeyink, V. L. and D. Jenkins (1980). Water Chemistry. John Wiley Sons, New York, 210. Sikora, F. J., L. L. Behrends, and G. A. Brodie (1995). Manganese and trace metal removal in successive anaerobic and aerobic wetland environments. Proc. 51th Anna. Am. Power Conf, Part 2, April 18-20, Chicago, IL, 57-2, 1683-1690. Illinois Institute of Technology, Chicago, IL. 

Turner, A. Millward, G.E. (1993) Application of the concept to the study of trace metal removal and adsorption during estuarine mixing. Estuarine, Coastal and Shelf Science 36, 1-13. 

Manzione, M. A. and D. T. Merrill (1989). Trace Metal Removal by Iron Coprecipitation Field Evaluation. Electric Power Research Institute Report EPRI GS-6438, Palo Alto, CA, USA. 

As for the overall metal removal efficiency, the best results were obtained for Pb and Zn as well as Cd (if precipitation at the cathode is considered), with more than 60% of each metal being mobilized as a result of the electrokinetic process. This result is likely related to multiple mechanisms, including speciation of trace metals in the original sediment, thermodynamic stability, and formation kinetics of metal-EDTA complexes, as well as ionic mobility of individual trace metal ions. However, due to the presumably interconnected effects of the mentioned mechanisms, a precise quantification of their individual contribution to trace metal removal from sediment is hard to be attained. 

Acetal copolymer Methyl methacrylate butadiene styrene terpolymer Polystyrene toys, high-strength Styrene/acrylates copolymer trace element, animal feeds Cobalt carbonate (ous) trace element, soils Cobalt carbonate (ous) trace metal analysis Perchloric acid trace metal removal... 

Williams JM, Olson MC (1976) Extended surface electrolysis for trace metal removal testing a commercial scale system. AIChE Symposium Series73, pp. 119-131... 

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