Waste treatment, liquid membrane technology

Since 1995, the Chemical and Nuclear Engineering Department of the Polytechnic University of Valencia in Spain has been working on the application of membrane technology to the treatment of low and medium level radioactive liquid wastes. In this chapter, we describe two practical cases of radioactive liquid waste treatment using membrane processes the treatment of Cs-contaminated water generated after a radioactive incident in a stainless steel production factory, and the treatment of 1 liquid wastes from nuclear medicine services at hospitals. 

Treatment of Cyanide-Containing Waste Water from Gold Mine Operation by Liquid Membrane Technology. News release in Kexue Bao (Newspaper of Science), China, October 16, 1987. 

Commercial eind laboratory applications of liquid membrane technology are discussed including gas transport, sensor development, metal ion recovery, waste treatment, biotechnology and biomedical engineering. Immobilized liquid membranes, emulsion or liquid surfactant membranes, and membrane reactors are discussed. Economic data from the literature for liquid membrane processes are presented and compared with existing processes such as solvent extraction and cryogenic distillation of air. 

It has been demonstrated that membrane separation processes can be successfully used in the removal of radioactive substances, with some distinct advantages over conventional processes. Following the development of suitable membrane materials and their long-term verification in conventional water purification, membrane processes have been adopted by the nuclear industry as a viable alternative for the treatment of radioactive liquid wastes [1]. In most applications, membrane processes are used as one or more of the treatment steps in complex waste treatment systems, which combine both conventional and membrane treatment technologies. These combined systems have proved more efficient and effective for similar tasks than conventional methods alone. 

This section aims to explain the unique features of membrane separation methods, their superior performance in contaminant removal, and their operational sensitivities and limitations. We focus particularly on the factors that need to be carefully assessed when the membrane technology to be used in the treatment of liquid radioactive waste is being considered. These include membrane configuration and arrangement, process application, operational experience, data related to key performance parameters, and plant and organizational impacts. 

Gupta, S.K.S., Slade, J.A., and Buckley, L.P., Demonstration of membrane technology for treatment of radioactive liquid waste, Ultrapure Water J., May, 1993. 

Chmielewski, A.G., Harasimowicz, M., and Zakrzewska-Trznadel, G., Membrane technologies for liquid radioactive waste treatment, Czech. J. Phys., 49, 979, 1999. 

Some research groups worldwide are currently working on the application of membrane technology to the treatment of radioactive liquid wastes with different levels of activity, from low to high activity waste. Research is mainly focused on wastes from the nuclear industry. However, the nuclear industry is not the only source of radioactive wastes medical and research applications of radioisotopes also generate radioactive wastes. 

Membrane technologies have a great potential in the treatment of radioactive liquid wastes, as it has been proved throughout this chapter. In this sense, it is expected a growing use of the membrane processes in the radioactive field, with different possibilities alone, combined between them (microfiltration or ultrafiltration and reverse osmosis) or combined with other conventional processes like evaporation or ion exchange. Furthermore, some special membrane processes, like membrane distillation or liquid membranes, could be applied for the specific treatment of radioactive wastes. 

Dulama, M., Pavelescu, M., Deneanu, N., Dulama, C.N., Application of indigenous inorganic sorbents in combination with membrane technology for treatment of radioactive liquid waste from decontamination processes, Radiochim. Acta 98, 413, 2010. 

G.Zakrzewska-Trznadel,M.Harasimowicz,A.G.Chmielewski, Membrane processes in nuclear technology-application for liquid radioactive waste treatment, Sep. Purif. Technol. 2(23), 2001, 617-625. 

G. Zakrzewska-Tiznadel, Advances in membrane technologies for the treatment of liquid radioactive waste. Desalination 321, 2013,119-130. 

Membrane processes are very important in our everyday life, but also in industry, for example, for water and waste water treatment, in medical applications, or separation of petrochemicals. Membrane processes are an energy saving method for the separation of mixtures, which occur in nearly all production processes in the chemical industry. Membrane-based devices are much smaller and work at lower temperatures compared to conventional separation facilities with distillation, extraction, or adsorption processes. Classical separation methods used for purification of chemical products, notably distillation, extraction, and crystallization are energy and cost intensive. Over 50% of the energy costs in the chemical industry are used for the separation of gaseous or liquid mixtures. With membrane technology, the costs for difficult separations, for example, of azeotropic mixtures. 

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