�rea Cient�fica: Electrónica e Instrumentação
Dessalinazação de água do mar
Publicada a 2015-04-09
Aluno: Pedro Filipe Coelho Rocha N�mero: 58742 Email: a58742@alunos.uminho.pt
Data in�cio: 01/11/2013 Data Conclus�o:
Orientador(es):
Nome: Luis Miguel Valente Gonçalves Email: lgoncalves@dei.uminho.pt
Descri��o:
Fresh water is a vital resource for human life. However, population growth and enhanced living standards, together with the expansion of industrial and agricultural activities, are creating unprecedented demands on clean water supplies all over the world. The Organization for Economic Co-operation and Development (OECD) and the United Nations (UN) have reported that 0.35 billion people in 25 different countries, particularly in the Middle East and Africa, are currently suffering from water shortage, and this will grow to 3.9 billion people (two-thirds of the world population) in 52 countries by 2025. Converting sea water into fresh water could provide the solution to the worldwide water-shortage problem, because about 97% of the total water resource on Earth is sea water, and only 0.5% of the total comprises potable, fresh water. Historically, distillation has been the method of choice for desalination of sea water, in spite of its high capital and energy costs, but this is suitable only for countries where the fuel required for distillation is relatively inexpensive. Current seawater-desalination techniques can produce freshwater at a cost of 0.4–0.7Eur per 1,000L, if operated at the scale of a large plant. However, areas affected by acute water shortage are often in the poorest, most underdeveloped countries, which lack the necessary power and water-delivery infrastructures. This presents a significant global challenge, because the lack of clean water also creates considerable health, energy and economic challenges to the populations of these countries. For this reason, small-scale or portable seawater desalination systems with low power consumptions and high throughput would be very useful in fulfilling important government, civilian and military needs, including humanitarian operations in disaster-stricken areas or in resource-limited settings.
Objectivos:
Objectives
The thesis aims a process for converting sea water (salinity ∼500 mM or ∼30,000 mg/L) to fresh water salinity <10 mM or <600 mg/L) in which a continuous stream of sea water is divided into desalted and concentrated streams. Rather than competing with larger desalination plants, we want to make small- or medium-scale systems, with the possibility of battery powered operation.
Methods
Capacitive deionization (CDI) is a water desalination technology in which salt ions are removed from brackish water by flowing through a spacer channel with porous electrodes on each side. Upon applying a voltage difference between the two electrodes, cations move to and are accumulated in electrostatic double layers inside the negatively charged cathode and the anions are removed by the positively charged anode. Ions can also be inserted in cathode or anode like a “desalination battery” This desalination battery operates in a similar way to the capacitive desalination techniques but instead of storing charge in the electrical double layer (built at the surface of the electrode) it is held in the chemical bonds (bulk of the electrode material).
A four-step charge/discharge process allows these electrodes to separate seawater into fresh water and brine streams. In the first step, the fully charged electrodes, which do not contain mobile sodium or chloride ions when charged, are immersed in seawater. A constant current is then applied in order to remove the ions from the solution (Step 1). In the second step (Step 2), the fresh water solution in the cell is extracted and then replaced with additional seawater. The electrodes are then recharged in this solution, releasing ions and creating brine (Step 3). In the final, fourth step (Step 4), the brine solution is replaced with new seawater, and the desalination battery is ready for the next cycle.
Work Plan
Study of available techniques for desalination – 2 months
Physical and chemical principles study – 2 months
Desalination proof of principle of – 2 months
Design and construction of portable desalination equipment – 3 months
Test of portable desalination equipment – 1 month
Article and thesis – 2 months
Advisor
L.M. Goncalves (lgoncalves@dei.uminho.pt)
References
“A Desalination Battery”, Mauro Pasta, Colin D. Wessells, Yi Cui, and Fabio La Mantia, Nano Letters 2012 12 (2), 839-843
“Direct seawater desalination by ion concentration polarization”, Sung Jae Kim, Sung Hee Ko, Kwan Hyoung Kang & Jongyoon Han; Nature Nanotechnology 5, 297 - 301 (2010)
“Ions transport and adsorption mechanisms in porous electrodes during capacitive-mixing double layer expansion (CDLE)”, RA Rica, D Brogioli, R Ziano, D Salerno, F Mantegazza, The Journal of Physical Chemistry C 116 (32), 16934-16938
“A Portable and Battery-Powered Seawater Desalination Device by Ion Concentration Polarization”, Dr. Sung Jae Kim, Prof. Jongyoon Han, November 16, 2010, Micro/Nanofluidic BioMEMS Group, Dep. of Electrical Engineering and Computer Science, MIT - Massachusetts Institute of Technology
Os candidatos necessitam aprovação a todas as UCs da área de microtecnologias
Links importantes:
http://dei-s1.dei.uminho.pt/pessoas/lgoncalves/Dissert_2013-14.pdf
Palavras chave:
Dessalinizão, desoinização capacitiva, CDI
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