EVALUATION OF A TECHNOLOGY FOR TREATMENT OF SURFACE WATER CONTAMINATED BY APPLYING DIRECTLY NANOMATERIALS AND OSMOSIS
ILDEFONSO CASTRO ANGULO (*); ADRIANA PATRICIA HERRERA BARROS, Ph.D. (**)
*: Q.F., Esp. Ingeniería Sanitaria y Ambiental, Candidato Msc. Ingeniería Ambiental,
** Directora departamento de Ingenieria Quimica Universidad de Cartagena, Colombia Grupo de Investigación: Nanomateriales Multifuncionales; Línea de Investigación: Nanotecnología y Remediación Ambiental
ABSTRACT
Water is a very important life for liquid. It is used in all cellular processes and essential for many industrial, agricultural and livestock activities. Unfortunately a large amount of water is required for everyday life, generating effluents of various types according to the type of materials involved in the process. Our society is forced to design and implement treatment technologies such waters to retrieve and reuse. This is mandatory in spite of the increasing decline in quantity and quality of water resources of the planet.
In this work the possibility of using osmotic membranes modified with silver nanoparticles to enhance their antimicrobial capacity in contact with contaminated water was investigated. Surface water samples from Cienaga de las Quintas, Cartagena, Colombia, was used as feed for direct osmosis test. Water analysis showed elevated microbial contamination. Modification of cellulose acetate membranes with silver nanoparticles showed antimicrobial antibacterial development potential against microorganisms content in raw water.
A pilot device was used to treat water samples by direct osmosis (DO), using iron magnetic nanoparticles modified iron as extraction solute and the osmotic membranes modified with silver nanoparticles as a means of osmotic treatment. Test results demonstrated potential use of this technology to produce an osmotic effluent free of microorganisms and other inorganic and organic contaminants. Recovering magnetic nanoparticles was made by an electromagnetic device, obtaining recovery rates exceeding 99% by weight of nanoparticles used as solute extraction direct osmosis.
Characterization of magnetic nanoparticles was made by testing energy dispersive X-ray (EDX), infrared Fourier transform spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) to determine their physical properties.
1 INTRODUCCIÓN
The increasing pollution of water sources with multiple organic and inorganic substances is a risk factor for life on earth. In recent years, membrane processes have proven to be reliable and reasonable alternative water to remove unwanted substances and drinking water even highly polluted water cost.
The present research proposal involves the construction of a water treatment process at laboratory scale by applying direct osmosis through a membrane modified with silver nanoparticles. Direct osmosis uses a semipermeable membrane modified with silver nanoparticles. Magnetic nanoparticles modified with carboxymethyl cellulose (CMC) were used as osmotic draw solute. Alternatively nanoparticles recovery by means of an electromagnetic device was evaluated. The goal was to evaluate an alternative treatment of contaminated surface water, specifically those found in the Cienaga de las Quintas in Cartagena city. The advantage of the use of nanotechnology in water treatment is based on the positive experiences in the scientific literature and the relative ease of implementing the techniques of synthesis and modification.
1.1 Direct Osmosis
Forward osmosis is a process governed by the concept of osmosis, which is a natural process that occurs spontaneously; in recent years has taken a great interest for its great potential for development of applications in fields such as desalination, wastewater treatment and food processing (Field & Wu, 2013). Unlike other membrane processes, direct osmosis uses the difference in osmotic pressure between a concentrated solution, known as osmotic agent, and a number of aqueous solutions as wastewater. The process involves the flow of water from the less concentrated solution (low osmotic pressure) to the more concentrated solution (osmotic agent), which pass through a permeable membrane that rejects molecules and contaminant ions. Continuous flow of water while osmotic pressure differences exist between the two sides of the membrane
The forward osmosis process is a useful alternative low energy within conventional membrane processes such as reverse osmosis (RO). The driving force is an osmotic pressure created by the osmotic gradient existing between a high concentration salt solution when placed on one side of the membrane versus a feed solution of low concentration on the other side. As direct osmosis processes use natural source pressure osmosis, power consumption can be significantly reduced compared to other pressure assisted processes such as the case of reverse osmosis. Direct osmosis has been considered as an appropriate technology for water treatment and related processes (Li, et al, 2012).
Direct osmosis employs a semipermeable membrane to separate water from the solids dissolved. The driver of this separation force is the osmotic pressure gradient. The simplest equation describing the relationship between osmotic pressure and water pressure and water flow is
Jw=A∆π-∆PEc.(1)
Where
Jw wáter flux
A membrane hydraulic permeability
Dp osmotic pressure difference
DP hydrostatic pressure difference
Furthermore the salt concentration in the permeate was determined based on the amount of water passing the draw solution in the course of the experiment and the amount of dissolved salts in this end. Thus, the percentage of salts rejected by the membrane (%) can be determined by the following equation (Ming, Wang, & Chung, 2010):
R=1-SPSF×100% Ec.(2)
Where R is the salt rejection rate (%) is the salinity S_P permeate (water passing through the membrane in g / L) and S_F is salinity feed (g / L). Systems have been developed in which the direct osmosis between wastewater highly contaminated with seawater are combined, and reverse osmosis brine produced for drinking water
1.2 Paramagnetic Nanopartícles
Magnetite nanoparticles can be synthesized from iron ore by leaching acid and iron hydroxide precipitation, coprecipitation of the aqueous solution with ferrous oxide in an inert atmosphere. The electrostatically stabilized magnetic nanoparticles show superparamagnetism and good dispersibility in aqueous media with high stability. Under examination by scanning electron microscopy and transmission magnetic nanoparticles are spheroidal or cubic shape with size range from 8.3 to 23.0 nm (Giri, BHUs, & Pradhan, 2011).
These nanoparticles can be functionalized by surface modification of the internal structure or through the addition of dendritic macromolecules of various kinds, using the micellar properties of the molecule. These guests cavities dendritic branches maintained by allowing the incorporation of metal particles. The solubility of these particles can be controlled depending on surface modifications (Newkome & Shreiner, 2008). Among the main advantages of using forward osmosis free operation of hydraulic pressures, high rejection of organic and inorganic contaminants and low membrane fouling are counted. The equipment used is very simple and the water flows are high (Cath, Childress, & Elimelech, 2006)
1.3 Silver Nanoparticles
For many years, silver has been used in various fields for its antibacterial qualities. Silver has been recognized and proven in various applications as an excellent antimicrobial agent for its high biocidal activity. However, use in the form of nanoparticles is most beneficial, since it is cheaper (Alonso, et al, 2011).
Silver nanoparticles exhibit a better antibacterial effect, and because of its small size, the surface area to volume is much larger (Doll, 2010). Bacteria, viruses and fungi depend on an enzyme to metabolize oxygen to live. Silver ions interfere with this enzyme and disables the absorption of oxygen, killing the microbe (Pelayo, 2007).
Se ha investigado diferentes rutas de producción de nanopartículas de plata; algunas basadas en la reducción de nitrato de plata por borohidruro de sodio o citrato de sodio, mientras otros métodos incluyen el uso de microondas, electrólisis, microemulsión y foto-reducción de iones de plata (Morales, Moran, Quintana, & Estrada, 2009).
1.4 Membrane modification with Silver NPs
The use of silver nanoparticles in different applications, has gained importance in recent times. One of these fields is the modification of membranes and polymeric fibers. This modification can be accomplished by no situ synthesis of silver nanoparticles. Research has shown that by hydrolytic decomposition of silver nitrate using as reducing agent and stabilizer triethanolamine, leading to spherical particles well dispersed throughout the membrane (Barud, and others, 2011).
Referring to the preparation of membranes used, researchers (Manjarrez Nevárez, and others, 2011) nanocomposite membranes prepared using the method of phase separation induced by steam. This was used in water treatment obtained from underground deposits in Chihuahua (Mexico), contaminated with high concentrations of arsenic, calcium, fluoride, sodium and magnesium. It was found that the efficiency of removal of arsenic and fluoride is affected by the amount of organic matter present in water.
The synthetic route varies depending on the selected method (Ming Ming Ling, 2010). Used between the reaction has been reported iron and 2-pyrrolidine, by refluxing at 245 ° C, reaction with refluxing at 280 ° C triethylene glycol, triethylene glycol or polyacrylic acid and refluxing at 275 ° C (Figure 5). The potential energy of nanoparticles tested explains the differences in the flow of water obtained through the membrane.
These magnetic nanoparticles are removed from the flow and can finally obtain recovered water. The experimental results showed that the nanoparticles prepared with alkalis surface show higher osmotic strength. Compared drain solutes based salts, the advantage of nanoparticles is that these do not cause backflow through the forward osmosis membrane (Ling & Shung Chung, 2012).
In Brazil, composite silver nanoparticles and bacterial cellulose membranes by in situ synthesis were obtained. The preparation was carried out by hydrolytic decomposition of a silver nitrate solution using triethanolamine (TEA) as a reducing agent and complexing agent. The concentration of silver nitrate solution was kept constant while the ASD varied. Membrane color changed from yellow-brown to black as the concentration of TEA was increased due to the increase in the content of nanoparticles. UV-Vis analysis by the formation of silver nanoparticles obtained evidenced wavelengths of 427 nm and 452 nm for concentrations of 0.01 mol / L and 1 mol / L of TEA respectively. Furthermore the behavior of composite membranes from Gram-negative bacteria such as E.coli and Gram-positive bacteria Staphylococcus aureus was studied. Zones of inhibition of 2 cm was obtained, confirming the diffusion of silver nanoparticles in the composite membrane (Barud, and others, 2011).
Other research focused mainly on the most recent and innovative applications of forward osmosis that are related to sustainability. Is the first to mention desalination, which is a highly energy consuming process if carried out by reverse osmosis. Are being sought to integrate the forward osmosis desalination process in order to treat seawater wastewater to reduce its salt concentration and thereby reduce energy costs. Another application that stands out is the integration of forward osmosis with the production of biofuels from algae and wastewater treatment. NASA is developing a project called OMEGA, in which plastic bags as photobioreactors, which have within algae and nutrients act as draw solution used; algae carbon dioxide capture and wastewater, releasing oxygen and clean water, while producing lipids to be used for biofuels. Finally, the authors discuss the importance of water for agricultural purposes and include a term known as fertigation, which is simply the simultaneous application of water and fertilizers through the irrigation system. In this, they use a concentrated solution of fertilizer and draw solution and combined by forward osmosis membrane with brackish groundwater, obtaining a diluted fertilizer suitable for agriculture (Hoover, Phillip, Tiraferri, Yin Yip, & Elimelech, 2011) .
In China, different amounts of biogenic silver nanoparticles incorporated into a polyester sulfone membrane by immersion phase method were used. Composite membranes were obtained with a thickness of 140 microns. The effects of the content of silver nanoparticles in the structure of the membrane and filtration performance were investigated, resulting in a significant increase in the permeated water as it increases in content of nanoparticles increase, showed that the presence of nanostructures hydrophilic increased capacity and the permeate flow. The results of thermogravimetric analysis showed good thermal stability due to the incorporation of the nano composite. In turn, the antimicrobial and antibacterial properties were tested using pure cultures of E.coli and a mixed culture (activated sludge bioreactor). This was carried out by the disc diffusion method, with a diameter of 25 mm and a 24-hour period. Potential biofilm formation on the surface of the membrane was studied by immersing the membranes in an anaerobic bioreactor activated sludge for 9 weeks. After 3 weeks of immersion, the membrane was unmodified high amounts of bacteria, in contrast to the modified membranes having small amounts. After 9 weeks, the composite membranes effectively resisted biofilm formation, having clearances even growth of bacteria, ie clean rooms. We conclude that these results agree with the nano compound obtained seems to be attractive to act as a reducing agent fouling membranes for water treatment (Zhang, Zhang, De Gusseme, & Verstraete, 2012).
NgaNguyen et al prepared a membrane for direct osmosis by immersion-precipitation, composed of cellulose triacetate (TCA) and cellulose acetate (CA) using different conditions for the preparation, which were optimized for membranes with increased water flow and salts under reverse flow. Optimized results membrane showed water flows 10.39 LMH (l/ (m 2 h)) about a reverse flow of solutes molNaCl/ 0084 (m 2 h) and a NaCl rejection rate of 99 533%. He also showed a more hydrophilic and softer than a commercial membrane surface, suggesting a lower fouling factor, becoming a potential application for treating wastewater and desalination (NgaNguyen, Yun, Kim, & Kwon, 2013).
2 EXPERIMENT
As contaminated water source to test the system Cienaga de las Quintas defined. This is a coastal lagoon system associated streams and inland lakes of the city of Cartagena (Figure 1). It ranges from Jiménez bridge to the Cartagena Bay, in the Bazurto bridge. It has a maximum depth of 2.25 m, with an approximate length of 1.29 km and a mirror of water about 30 hectares (Tirado, Manjarrez, & Diaz, Environmental characterization of Cienga of Quintas located in Cartagena de Indias, Colombia, 2011). This is an area of potential use for the conservation and preservation of flora and fauna because the mangrove area is in good condition although the water has a high rate of contamination (Ministry of Environment, Ministry of Environment, Housing and Territorial Development ; EPA, Environmental Public Establishment of Cartagena, 2006). This water pollution is largely due to human activities, mostly developed market Bazurto, main supply center in the city. A consequence and the water is contaminated with various substances, both organic and inorganic as well as energy, deteriorating quality and preventing further use