الفهرس 
Introduction and Literature ReviewOnly 14 pages are availabe for public view
 |  | from | 255 |  |  |
| | | from | 255 | | |
Abstract
Water is considered one of the most important ingredients upon which civilizations have been based throughout history. Therefore, human life has centered throughout history near water sources. In Egypt, the Nile River is the main source of water on which the ancient Egyptian civilization was based, which relied on agriculture as a primary activity for most of the population at that time. Because of this great value of the Nile River, the ancient Egyptian was sacredly careful not to pollute the waters of the Nile. Unfortunately, with the expansion of human activities and the population increasing around the main course of the Nile and its tributaries, the leakage of various human activities from agricultural, industrial, and health care to the surface waters of the Nile. With the scientific progress in the field of pollutants detection and their impact on human health and the environment in general, Various categories of pollutants with a significant and cumulative impact have been monitored. The current study provided a comprehensive trail for the design, preparation, and application of novel photocatalysts used in treating water samples from Rosetta Branch that could contain a complex matrix of pollutants using artificial and direct sun light.
4.1. Summary:
For decades, researchers have made a lot of efforts to monitor various pollutants and find ways to estimate their concentrations and find effective ways to remove them. As a result of these efforts, these pollutants have been classified into organic, inorganic, bacteriological and biological pollutants. They also studied the effectiveness of traditional treatment methods that depend on the use of coagulants such as aluminum sulfate (alum), or iron salts such as ferric sulfate, ferric chloride, and other coagulants, which remove suspended matter in water and have the ability to adsorb some pollutants. The ability of oxidants used in water disinfection such as chlorine, ozone, oxygen water, and ultraviolet radiation to oxidize some organic pollutants was also studied. Also, some researchers mixed some of these methods with each other and studied their ability to get rid of some organic pollutants. With the development in materials science and the discovery of the unique properties of nanomaterials, especially metal oxides and their abilities to work as semiconductors and the possibility of using them as photo-induced catalysts, researchers worked on using these properties to break down pollutants in water. The most famous of these nanomaterials are oxides of titanium, zinc, iron, and tungsten.
The aims of the currents study were to prepare two categories of photocatalytic nanocomposites so that they are from available materials, environment friendly, harmless to human health, can be recovered, and be economically feasible to ensure the sustainability of treatment methods. Iron, titanium, and zinc oxides were selected to prepare three photo-magnetic catalysts for the first category. The magnetic properties of these catalysts were exploited to facilitate their recovery after the treatment process. These catalysts were labeled with MTN1.5, MTN 9.5, and ZMTN. The second category was prepared by using aluminum pellets and loading titanium oxide on them, as well as copper oxide in two different concentrations. These catalysts were labeled with T/A, H-Cu/T/Al, Ma -Cu/T/Al, and Mb -Cu/T/Al. The photocatalysts of this category were synthesized using thermal or wet impregnation methods to assess the impact of the preparation methods on photo-degradation efficiencies. In addition, the different amount of doped copper oxide was tested on photo-degradation effectiveness. Routine characterization of these nanocomposites was performed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD).
Three groups of organic pollutants, which have been proven to have a negative impact on human health and the ecosystem were selected. They were selected via researches survey published in literature for more than twenty years, which revealed the presence of these substances in the drains that flow into the Rosetta branch of the Nile River and polluting its surface water. The first group consists of pharmaceutical residues that varied between antibiotics, analgesics and anti-inflammatory. The second group consists of pesticide residues used for agricultural purposes. The third group consists of herbicides also used for agricultural purposes, also.
- group of pharmaceutical residues: Ofloxacin, oxacillin, sulfamethazine, ciprofloxacin, paracetamol, ibuprofen, caffeine, diclofenac sodium, naproxen, and penicillin.
- group of pesticides residues: molinate, simazine, Isoproturon, atrazine (1), propanil, carbofuran, dimethoate (1), pendimethalin, metolachlor, pyriproxifen, and aldicarb.
- group of herbicides residues: (2,4-dichlorphenoxy) acetic acid (2,4D), 2-(2,4-dichlorphenoxy) propionic acid (2,4DP), (2,4,5-trichlorophenoxy) acetic acid (2,4,5T), Bentazone, (4-chloro- 2-methylphenoxy) acetic acid (MCPA), and (RS) 2-(4-chloro-2-methylphenoxy) propionic acid (MCPP).
Ezbet Sharif, located on Rosetta branch, about 6 km away from the outlet of El Rahawy drain, was chosen as a sampling point. Spiking slightly higher known concentrations of the three groups of pollutants into raw water samples was carried out. This step was taken to ensure that these compounds were present in relatively high concentrations during the experiment. A homemade cabin equipped with a metal halide simulated sunlight source with a power of 400 watts and an illumination intensity of 4000 lux was used to conduct the photo-degradation experiments. Experiments were also conducted once again using natural direct sunlight and under the same conditions and steps, to measure the efficiency of the method under natural conditions. The spiked samples were subjected to stay in the dark for 15 minutes to complete the adsorption process and reach the equilibrium state. Then, they were exposed separately to simulated sun light and natural direct sunlight. Samples for analyses were withdrawn at different time in order to measure the extent of the degradation of pollutants in both cases.
The results were interpreted as follows:
Generally, there was no significant difference in photocatalytic degradation of pharmaceutical compounds between both types of the catalysts (iron-based and alumina-based), whatever with adding metals and with different methods of preparation of the catalysts.
Photocatalytic degradation of Sulfamethazine was the highest (from 99%-100% removal) with both types of the catalysts (iron-based and alumina-based) compared with the other pharmaceuticals, whatever using artificial light or natural sun light. Furthermore, the addition of different metals such as zinc or cupper to the photocatalysts has no effect on photodegradation efficiency toward Sulfamethazine.
Diclofenac sodium exhibited the second highest percentage removal (more than 92%-100% removal) with both types of the catalysts (iron-based and alumina-based) using the direct sun light compared with using the light simulator.
Inversely, Ibuprofen showed higher percentage removal (85%-95%) with both types of catalysts (iron-based and alumina-based) using the light simulator compared with the using direct sun light.
Except for Diclofenac sodium and Ciprofloxacin, light simulator showed higher efficiencies on photocatalytic degradation toward the other pharmaceuticals with both types of catalysts (iron-based and alumina-based) compared with using the sun light.
Generally, the iron-based catalysts showed slightly higher efficiencies in photocatalytic degradation of all pesticides than with alumina-based catalysts, regardless of metal addition or methods of preparation of the catalysts.
Photocatalytic degradation of Pendimethalin was the highest (95% removal) with the iron-based catalysts and (90% removal) with the alumina-based catalysts by using direct sun light compared with the other compounds. Furthermore, the addition of different metals to the photocatalysts, such as zinc or cupper, has no effect on the photocatalytic degradation efficiency toward Pendimethalin.
Pyriproxifen exhibited the second highest percentage removal (93% removal) with the iron-based catalysts, regardless of whether it was exposed to artificial or natural light. While the photocatalytic degradation of this compound showed lower percentage removal (76%) with the alumina-based catalysts by using the light simulator compared with using the direct sun light (57% removal).
Except for Pendimethalin and Pyriproxifen, the Photocatalytic degradation efficiencies were low (39%-58% removal) with the iron-based catalysts, and (34%-46% removal) with the alumina-based catalysts. Furthermore, light simulator showed higher efficiencies on photocatalytic degradation compared with using the direct sun light.
Generally, the photocatalytic degradation of herbicides was the lowest with both types of the catalysts (iron-based and alumina-based) compared with the pharmaceuticals and pesticides.
Iron-based catalysts were more efficient than alumina-based catalysts in photocatalytic herbicides degradation.
The addition of different metals to the photocatalysts, such as zinc or cupper, has no significant effect on the photocatalytic degradation of the herbicides.
The direct sun light showed higher efficiencies in photocatalytic degradation of the herbicides with both types of the catalysts (iron-based and alumina-based) compared with using the light simulator.
2,4-D, Bentazone and MCPA exhibited higher photolytic degradation with the iron-based catalysts by using light simulator compared with the other compounds.
In general, the results of the study revealed the ability of the prepared nanocomposites to remove the three groups of dangerous organic pollutants, which have been proven to be dangerous to human health and the ecosystem. This removal might be accomplished through adsorption or photo-catalytic degradation using direct sun light, bringing them closer to practical application in treatment plants after the necessary utilities were provided. To reduce pollution, these catalysts can be used in industrial sites in the form of filters exposed to the sun to treat wastes before they are dumped into water drains. Also, these catalysts can also be loaded onto transparent surfaces and immersed in wastewater at municipal treatment plant entrances. The results of the study can also be used in the production of many treatment tools, which helps to establish new industries and provide new job opportunities.
4.2. Conclusion
The prepared catalysts exhibited superior photodegradation efficiencies of potentially harmful organic pollutants created by various activities using artificial and direct sunlight. Despite the presence of a complex matrix and a large number of contaminants, these catalysts demonstrated varying degrees of photodegradation abilities, ranging from 100 % to less than 25 %t in some cases. Due to differences in surface properties and added metals (i.e., Zn, and Cu) concentrations, the preparation methods of these catalysts were reflected in their efficiencies toward photodegradation by using both light sources. Some research should be conducted on such catalysts to investigate their behavior during photocatalytic reactions with the selected pollutants present in a complex matrix. Because these treatments are critical, the mechanisms, pathways, intermediates, and reaction conditions should be clarified.
4.3. Recommendation
The current study clarifies the advanced oxidation processes and water resource contamination. Taking into account the study’s findings, the following should be taken into account:
Continues monitoring of the contaminants existing in water resources.
Further studies should be done on some contaminates e.g., pharmaceutical residues.
Given the limitations of conventional treatment methods for organic pollutants, studies on modern treatment methods for removing these contaminants should be widely disseminated.
Expansion of studies on photocatalyst-based techniques, as well as an examination of their impact on treated water quality.
Behaviours, pathways, and mechanisms of the photocatalysts during the reaction with the contaminants should be studied furthermore.
Many epidemiological studies have found that some organic contaminants, such as pharmaceutical residues, have a negative impact on human health, so water legislation should be changed.
Finally, in light of current and future water challenges, a national strategic plan should be developed to coordinate these activities and benefit from their outcomes in order to maximize the utilization of all freshwater sources in Egypt.