The population increases and residents consume more fresh water. In order to solve this problem, it is necessary to find a gentle and inexpensive process for water desalination.
China has a large and growing demand, Japan has a large demand and also the Middle East. It is a worldwide problem (Klausner, 2004).
Actually, the water desalination problem is the high costs. On this research, we are using the interesting quality of the ultrasonic waves because they can be developed into several harmonics that can dissociate the water molecule (Suslick, 1988; José F. Ábrego López, 2006).
The advantage of this process, is the recovery of silver from the AgCl byproduct. It might be an economical process.
On this new process, using the waves additive phenomenon, it was possible to accelerate the chemical reactions and to dissociate the stiffness molecule of NaCl.
Several countries, in order to find an economical process, are using Inverse Osmosis and Nanotubes but they have contaminate byproducts.
MATERIALS AND METHODS
Theoretical considerations: The study was conducted in El Instituto
Nacional de Investigaciones Nucleares (México) on 2006 and involves the
desalination of the thermal geyser from Municipal hot-Baths of Ixtapan de la
Sal, Mex. (México).
||Comparative study between thermal water of Ixtapan De La Sal,
Mex. and seawater
On the process were used chemical reactions, ultrasound
and flotation cell.
Table 1 shows a comparative study between the thermal water of Ixtapan de la Sal, Mex. and seawater (Otomer, 1983). The thermal water on the geyser was 37°C.
Some physical properties of NaCl: The molecular dissociation of NaCl
is very difficult because it is too much high stiff structure. The physical
properties of NaCl are (http://www.chemed.chem.purdue.edu):
|| A view of the experimental equipment
Each Na+ ion in NaCl is surrounded by six Cl¯ ions and each
Cl¯ ion is surrounded by six Na+.
Apparatus and procedure: The apparatus used were (Fig. 1):
||Ultramet II, Sonic cleaner, 100 watts, 55 kHZ
||Flotation cell, DENVER, Size D-1
||Conductivity meter, orion, mod. 145
The process involves a series of chemical reactions in order principally to dissociate the NaCl into sodium ion Na+ and chloride ion Cl¯.
In the desalination technology, on one liter of brackish water Ag2SO4 and CaSO4 were added and then, was excited by ultrasound and flotation cell. It was done in two steps each one of 1 h. At the end of the process the filtrate was analyzed for sulfate, nitrate, hardness, chloride, sodium, iron, silver, calcium, pH and bacteria concentration.
It was also obtained a calcium and sodium sulfate precipitated and AgCl also precipitated in which the silver is recovery using industrial methods and treated water. Because the equipment was designed under standards, this process can be scaled to a largest seawater desalination process.
||Comparative study between brackish water processed and some
RESULTS AND DISCUSSION
According to drinkable water standards, it is important to note that the NaCl was totally dissociated and the values are under such standards. Using this results, it is possible to design new tests in order to have the best results for the silver and sulfates.
Another interesting thing is that, only the ultrasonic excitation of brackish water, was enough for to destroy the 99.65% of bacteria and using also the Ag2SO4, all bacteria were destroyed. It is important because, the brackish water treated is sterilized.
It is possible that, the conductivity was increased for the Ag+ and SO4¯ that remain in the final water treated.
Table 2 presents a comparison between the brackish water processed and some
Table 3 presents the percentage of NaCl and bacteria eliminated from the original
The conductivity was increased from original water 9,490. microsiemens/cm to treated water 10,130. microsiemens/cm:
||Using Ag2SO4 and CaSO4 on
the process, the bacterial colony was destroyed from 45 cfu mL1
||Without chemical reactions on the process and only excitation with ultrasound and flotation cell, the bacterial colony 40 cfu mL1 was destroyed 99.65% and only remaining spores and fungus 0.35%.
The water desalination process on NaCl was satisfactory but because it is a preliminary study, it is necessary to design new tests in order to eliminate Ag+ and SO4¯ from the treated water.
||Percentage of NaCl AND bacteria eliminated from the original
The chemical reactions were also satisfactory and the ultrasonic and flotation cell excitation accelerated the process. The same process can be applied for seawater desalination, the difference is approximate 10 times more of NaCl.
The drinkable water standards are very restrictive for silver (0.05 ppm) on such a water but, the photographic industry has the process for recovery silver from photographic solutions by means of the metallic replacement and electrolytic process (Davis, 2001).
It can be a new and economic and efficient process because it is possible to recovery silver and only it is necessary to find the best parameters of time duration of process and reactive dose.
The sodium chloride was converted into AgCl precipitated and a dual precipitated of Ca and Na sulfate.
For economical problems, it was not possible to improve the process because it is necessary to design new tests in order to eliminate the Ag and SO4 residual.
The process could be inexpensive because from AgCl it is possible to recovery the silver. And also, it is possible to recovery silver from the final solution because the photographic industry has the process for recovery silver from photographic solutions by means of the metallic replacement and electrolytic process (Davis, 2001).
||May be the conductivity was increased for the Ag and SO4
||It is very important the bactericide action of the process
because the final water could be drinkable. They were killed 100.00% of
the original 45 cfu mL1.
||The bactericidal properties of the ultrasound also are very
important because it is the confirmation of my doctorate degree named El
ultrasonido como una radiación ionizante (Instituto Politécnico
Nacional, México). From 40 cfu mL1 were killed 99.65%,
remaining 0.35% of the spores and fungus.
||Because the tests were done on standardization equipment,
the process can be scaled to a largest seawater desalination.
||If the desalination process is good for the thermal water
from Ixtapan de la Sal, also it is good for the seawater desalination because
the chemical reactions are the same.
The preliminary study, is very important because, the NaCl was dissociated and this process can be applied for seawater desalination and only it is necessary to design new tests in order to eliminate the Ag+ and SO4¯ on the final water treated. It is possible to have a drinkable water without bacteria and fungus.
I would like to thank Ing. Gerardo Nava Solares, Dpto. Análisis Químicos (ININ) for the supply of chemical reactive, M.C Ricardo García Ruiz and Ing. Alberto Medrano Beltrán Dpto. De Tecnología de Materiales (ININ) for the support on the ultrasonic equipment and M.C. David Alcántara Díaz Dpto. De Biología (ININ), for the biological study.