الفهرس 
CorrosionOnly 14 pages are availabe for public view
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Abstract
Brackish groundwater makes up a portion of the total amount of water stored in aquifers. Brackish groundwater desalination holds promise as a water supply strategy. It offers opportunities such as providing a viable water resource where other supply options are not readily available. Brackish groundwater desalination is only one tool in the toolbox for meeting water supply needs. One must take care that it is the most appropriate, environmentally cost effective tool for the specific location it is implemented in.
Most machines that make electricity need some form of mechanical energy to get things started. Mechanical energy spins the generator to make the electricity. In the case of hydroelectricity, the mechanical energy comes from large volumes of falling water or running water under pressure such as reject brine from R.O. desalination plants.
A small-scale hydro system usually consists of turbine, which is made to spin by jets of high velocity water. The turbine spins continuously, as long as there is water to drive it. The recovery of lost energy in RO desalination plants through hydro-turbine systems is a big aim to lower its cost and its large scale application in agriculture and irrigation fields.
The turbine is connected to an electrical generator, and the electricity is then available for running appliances or charging batteries. The spent water is returned to the stream. This kind of system is called Micro-hydro systems which can provide clean, environmentally friendly electricity in rural communities.
Mini hydro turbine could be used for energy recovery from the reject of the brackish desalination plants. The reject stream is characterized by high velocity, high pressure and high salt concentration. All the above mentioned makes these streams very corrosive for the material of the hydro turbine. So protection of these hydro turbines against corrosion is required. Many technologies for this protection may be carried out.
Corrosion can lead to enormous economic costs and damage to modern industrial societies, which have a bad impact on humans and the surrounding environment. It has been reported that corrosion consumes more than 3% of the gross domestic product (GDP) of the world annually (Hao et al., 2011, Renner et al., 2006 and Stierle, 2008).
One of the most commonly practiced techniques to prevent metals from corrosion is to apply anticorrosive paints on their surfaces.
One of the most promising technologies is the use of impressed current cathodic protection which will be compared with other cost effective techniques for corrosion protection.
It offers permanent and automatic protection that aids in preventing galvanic corrosion and electrolysis from attacking the undersides of various mobile or fixed offshore structures as well as sea vessels. It is the top protection system of choice of ship owners since it can efficiently reduce maintenance and fuel cost.
Coatings and cathodic protection complement each other. where possible, one can use them in combination to achieve the optimal economy and protection. The coating protects everywhere.
Conducting polymers gained much attention during the past two decades because of their environmentally friendly behavior as well as their unusual corrosion inhibiting action for metals (Gomez et al., 2010, Blinova et al., 2007, Yan et al., 2013, Annibaldi et al., 2012, Guimard et al., 2007, Palraj et al., 2012 and Zhu et al., 2006). Among these conducting polymers, polyaniline is considered to be one of the best anticorrosive materials (Lee et al., 2006, Guo et al., 2006 and Wu et al., 2011). By interacting between PANI and hosting material such a Zeolite we can get a new material with new properties, we called it composites. Composites are materials made from a mixture of a minimum of two components which, when combined, produce a material with significantly different physical or chemical properties which are superior to those of the individual materials.
This study deals with synthesis, characterization, structural and corrosion studies of some new composites formed from the reaction of Zeolite X with Polyaniline. The present work was aimed mainly to study the spectroscopic, morphological studies of all synthesized composites and corrosion studies for the Polyaniline/Zeolite X coat. The outcome of the results can be summarized as
I- Synthesis study:
Synthesis of PANI was done by chemical oxidation way which involved the use of hydrochloric acid in the presence of ammonium persulfate as the oxidizing agent in the aqueous medium. Zeolite X with 1, 2, 3 and 4% (w/w) was added in acidic media. Therefore, the yield was PZ1, PZ2, PZ3 and PZ4 composites.
II- Characterization studies:
from the infrared analysis of Polyaniline/Zeolite X composites spectra, 3436 cm−1 band had been dropped into 3428 cm−1 due to stretching frequency of the N-H group in Polyaniline (Olad and Naseri, 2010). Another two bands were recorded at 1584 cm−1 and 1491 cm−1 which were attributed to quinine and benzene rings after being 1586 cm−1, 1490 cm-1 in Polyaniline spectra. The degree of electron delocalization could be measured in Polyaniline chains by infrared analysis, 1107 cm-1 band proved it. There were new absorption peaks at 1047, 538 and 514 cm–1 which could be assigned to the presence of Zeolite X in the prepared composites. Therefore, FTIR spectra of Polyaniline/Zeolite X composites exhibits bands characteristic of Polyaniline as well as of Zeolite X which confirms the presence of both components in the PZ composites.
The UV-vis absorption spectra for Polyaniline and Polyaniline/Zeolite X composites were done in DMSO solvent. This spectrum showed a characteristic peak around 330 nm and a broad peak around 600 nm. The first one corresponds to the π– π * transition. The second one can be assigned to the exciton transition which is rather weak in these polymers (Ozdemir et al., 2006).
The X-ray diffraction patterns were recorded for Polyaniline, Zeolite X and Polyaniline/Zeolite X composite. The intensity of the XRD pattern peaks could be influenced by crystallinity or by polyaniline chain order in the composite structure. According to the XRD patterns of polyaniline, it can be seen that polyaniline has a relatively amorphous structure, but by encapsulation of Polyaniline in the Zeolite X channels the alignment and arrangements of polyaniline chains were improved and as a result, the intensity of the peaks related to the composite was increased (Shyaa et al., 2015).
In order to inspect the surface morphology of Polyaniline, Zeolite X and Polyaniline/Zeolite X composites and estimate the presence of both materials and the structure of each other, scanning electron microscopy (SEM) and Transmittance Electron Microscope (TEM) were used.
SEM images appeared the accumulation of the single polyaniline chains as it emitted out of the zeolite layers. from TEM images, it has been observed that Zeolite X particles have been dispersed in the polymer matrix inside polyaniline chains. The dark spots inside the chains in the TEM images refers to the Zeolite X particles. These two analysis confirmed the presence of both components in the prepared composites.
Thermogravimetric (TGA and differential thermogravimetric analyses DTG) and Differential scanning calorimetry (DSC) analysis of composites were carried out to identify their thermal stabilities structure. Analysis of Zeolite X, Polyaniline and its composites by thermogravimetric analysis revealed two weight loss regions, the first one at a round temperature of 250 °C which corresponds to the loss of water. The second temperature region for Zeolite X was above 200 °C and this may attributed to the complete combustion of organic substances of the Zeolite X structure (Giroux et al., 2016 and Tiseanu et al., 2007). For Polyaniline at 300°C the Polyaniline begin to degrade and was completely decomposed at 630°C. The interaction between Polyaniline and Zeolite X could be explained from the extent of decomposition of PANI/Zeolite X composites (560 °C) which was less than that of Polyaniline (490 °C) (Shyaa et al., 2015) and this leads to increase the thermal stability of composites.
Thermal properties and interaction between the polyaniline and Zeolite X could also be investigated from the differential scanning calorimetry (DSC) studies. DSC plots showed some endothermic and exothermic peaks for removal of different materials, crystalline melting, recrystallization and polymer decomposition.
Polyaniline has two an endothermic transition, the first one was at 75-116 °C indicated the evaporation of water molecules from the polymer matrix and structural changes in the polymer morphology due to the thermal treatment (Alves et al., 2010). The second endothermic peak was at 247 °C which arises due to thermal degradation of polymer (Ahdash et al., 2014 and Kazim et al., 2007).
Zeolite X showed a single large intensity endothermal dehydration peak at a temperature range of 101-165 °C with very low heat capacity (Ahdash et al., 2014).
The prepared composite materials in different compositions of Zeolite X showed entirely different thermogram than that of polyaniline. It showed an endothermic peak at 50-150℃, due to the loss of water molecules present in polymer matrix. While the second peak was an exothermic peak at 602, 604, 611 and 618 ℃ for PZ1, PZ2, PZ3 and PZ4 composites respectively, which might be assigned to the cross-linking of composite backbone, while the small change above 700℃ might be assigned due to the degradation of the composite backbone.
EDX spectrum was used to show the elemental distribution of the composite material. This analysis was done to prove the incorporation of Polyaniline chains inside Zeolite X structure. It was found that PANI, only peaks corresponding to C, O and N elements with high content of carbon are displayed, (Rafiqi and Majid, 2016) while for the Zeolite X the EDX spectrum showed the presence of Al, Si, Na and other peaks with high content of Al and Si (Jahangirian et al., 2013). The presence of a band attributed to Aluminum and Silicon in the EDX spectrum of the composites indicated the incorporation of polyaniline with the Zeolite X structure. The intensity of aluminum and silicon signals increased for Polyaniline/Zeolite X composites in the following order: PZ1< PZ2<PZ3<PZ4 with increasing Zeolite X percent in composites.