Evaluation of sterilization possibility in water environment of activated nano MnO 2 coated on calcined laterite Cao Việt Trường Đại học Khoa học Tự nhiên Luận văn ThS Chuyên ngành: Quản lý chất thải và xử lý vùng ô nhiễm Người hướng dẫn: PGS.TS Trần Hồng Côn Năm bảo vệ: 2011 Abstract: The TEM images of solution clearly reveal the presence of a large quantity of nanomanganese dioxide particles with lozenge shape and barked sphere with diameters around 30nm. The SEM images of material’s surface shows the distribution of barked sphere shape nano MnO 2 all over laterite surface. - Investigation sterilizing possibilities in static condition and dynamic condition. - Manganese has affect in sterilizing capabilities of BRM. It reacts with MnO 2 to create semi-product [MnO 2 .Mn].nO 2 which plays as strong sterilization substances. Keywords: Quản lý chất thải; Xử lý ô nhiễm; Hóa học môi trường Content 1. Introduction 1.1 Water situation in general Water is one of the world’s most essential demands for human life, and the origin of all animal and plant life on the planet. Civilization would be impossible without steady supply of fresh and pure water and it has been considered a plentiful natural resource because the sensitive hydrosphere covers about 75% of the Earth's surface. Its total water content is distributed among the main components of the atmosphere, the biosphere, oceans and continents. However, 97% of the Earth's water is salty ocean water, which is unusable for most human activities. Much of the remaining 3% of the total global water resource, which is fresh-water, is locked away in glaciers and icebergs. Approximately 20% of the freshwater resources are found as groundwater, and only 1% is thought to be easily accessible surface water located in biomass, rivers, lakes, soil moisture, and distributed in the atmosphere as water vapor. [1] In the process of rapid development of science and technology, the demand for pure water is increasing to serve multifarious purposes in different types of industries. Global water consumption raised six folds in the past century, double the rate of population growth. In addition, the boom in world’s population during recent decades, has contributed to the dramatically rising demand of pure water usage for both household and industrial purposes. The high population density and industrialization speed have triggered the hydrosphere to be polluted with inorganic and organic matters at a considerable rate. Moreover, to satisfy the food demand, a number of harmful chemicals such as pesticides and herbicides are used in order to improve the productivity in agricultural production, which also causes the scarcity of clean resources. [1] 1.2 Water sterilization Water sterilization technology is useful in various ways for our daily life. For example, it is used in water and sewerage systems treatment. Methods commonly used for sterilization include chemicals, heat, ultraviolet (UV) radiation, and ozone. Chemicals (chlorine, peroxide, etc.) are utilized extensively for sterilization because of their simplicity; however, they probably form unexpected effects, such as modifying the quality of the target. In addition, sterilization by chlorine usually generates odorous substances and bio-hazardous materials. [2] 1.2.1 Boiling The main disadvantage of this method is that it requires a continuous source of heat and appropriate equipment. 1.2.2 Chlorine The drawback of this method is that it the storage of chlorine and its use must need careful handling, large chlorine residual may cause bad taste. 1.2.3. Ozone The disadvantage of this method is the high cost for operation. 1.2.4 Ultraviolet light The main disadvantage to the use of UV radiation is that, like ozone treatment, it leaves no residual disinfectant in the water. Because neither ozone nor UV radiation leaves a residual disinfectant in the water, it is sometimes necessary to add a residual disinfectant after they are used. This is often done through the addition of chloramines, discussed above as a primary disinfectant. When used in this manner, chloramines provide an effective residual disinfectant with very few of the negative aspects of chlorination. [6] 1.2.5 Hydrogen peroxide Hydrogen peroxide (H 2 O 2 ) works in a similar way to ozone. Activators such as formic acid are often added to increase the efficacy of disinfection. It has the disadvantages that it is slow-working, phytotoxic in high dosage, and decreases the pH of the water it purifies. [6] 1.2.6 Solar disinfection One low-cost method of disinfecting water that can often be implemented with locally available materials is solar disinfection (SODIS). It partially relies on the ultraviolet radiation that is part of sunlight. Unlike methods that rely on firewood, it has low impact on the environment. [6] 1.2.7 Photocatalysis on semiconductors The processes of heterogeneous photocatalysis on semiconductors, developed during the last twenty years, were firstly regarded as potential methods for hydrogen photoproduction from water. However, even at the very beginning of their development, some papers appeared which dealt with photooxidation of organic and some inorganic (e.g. CN - ions) compounds. For more than ten years the interest of scientists has turned into application of the heterogeneous photocatalytic methods to water detoxification. [6] 1.2.8 High speed water sterilization using one-dimensional nanostructures One-dimensional nanostructures have been extensively explored for a variety of applications in electronics, energy and photonics. Most of these applications involve coating or growing the nanostructures on flat substrates with architectures inspired by thin film devices. It is possible, however, to make complicated three-dimensional mats and coatings of metallic and semiconducting nanowires, as has been recently demonstrated in the cases of superwetting nanowire membranes and carbon nanotube (CNT) treated textiles and filters. Silver nanowires’ (AgNWs) and CNTs’ have unique ability to form complex multiscale coatings on cotton to produce an electrically conducting and high surface area device for the active, high-throughput inactivation of bacteria in water. [6] 1.3 Nanotechnology Nanotechnology is the science of the small; the very small. It is the use and manipulation of matter at a tiny scale. At this size, atoms and molecules work differently, and provide a variety of surprising and interesting uses. The prefix of nanotechnology derives from ‘nanos’ – the Greek word for dwarf. A nanometer is a billionth of a meter, or to put it comparatively, about 1/80,000 of the diameter of a human hair. Nanotechnology should not be viewed as a single technique that only affects specific areas. It is more of a ‘catch-all’ term for a science which is benefiting a whole array of areas, from the environment, to healthcare, to hundreds of commercial products. Although often referred to as the 'tiny science', nanotechnology does not simply mean very small structures and products. Nanoscale features are often incorporated into bulk materials and large surfaces. Nanotechnology is already in many of the everyday objects around us, but this is only the start. It will allow limitations in many existing technologies to be overcome and thus has the potential to be part of every industry: 1.4 Manganese dioxide Manganese dioxide (MnO 2 ) occurs naturally as the mineral pyrolusite, which is the main ore of manganese and a component of manganese nodules. In the past decades, Manganese dioxide have been exploited for heavy metal removal from aqueous media, i.e., heavy metal ions [8], arsenate [9], and phosphate [10] from natural water has attracted considerable attention, because it would significantly mediate the fate and the mobility of the target pollutants in water [11, 12]. For example, Kanungo et al. [12] and Kanungo et al. [13] studied the sorption of Co(II), Ni(II), Cu(II), and Zn(II) ions on manganese dioxide particles in the presence of different electrolytes. They found that these toxic metals can be effectively trapped by manganese dioxide through electrostatic forces and formation of inner-sphere complexes. The specific properties of manganese dioxide render it a potential sorbent for heavy metal ion removal from contaminated water. Manganese dioxide has high oxidation potential so it can disrupt the integrity of the bacterial cell envelope through oxidation (similar with Ozone, Chlorine…). 1.5 Laterite Laterites are residual products, which are formed during prolonged mechanical and chemical weathering of ultramafic bedrocks at the surface of the earth [14]. It was found that laterite’s profiles depend on the conditions of weathering intensities, geotectonic zones and the parent rock’s compositions. Laterite is used to describe soils, ferruginous materials, weathering profiles, and chemical compositions, which are based on SiO 2 , Al 2 O 3 , and Fe 2 O 3 [15]. Laterite is categorized as soil which contains up to 60.3% iron [16] and is available in many tropical regions, such as India, Vietnam, Philippines and China [17-19]. Furthermore, laterite adsorbs other ion and heavy metals, such as fluoride (F), cesium (Cs), mercury (Hg II) and lead (Pb) [20-22]; in water treatment, laterite has been found to be effective and feasible as an adsorbent in removing some heavy metals in contaminated groundwater. When laterite heated to 420-900 o C, the removal capacity is even better. Expanded laterite has special properties such as high porosity (and consequently, low density), it is chemically rather inert, non-toxic, thus it can be used as excellent filter aid and as a filler in various processes and materials. Because of it low specific surface area and acidic surface, expanded laterite was found to be of limited use as an adsorbent for bacterial removal on its own, but it can be utilized as an appropriate carrier material. On the other hand, nanoparticles MnO 2 have a large surface area and high oxidation potential which make them excellent candidates for the bacterial removal in general. 2. Objectives and Research methods 2.1 Objectives When materials possess nanoparticle size, they will have special properties in chemical, physical, adsorption and electrode, etc. Therefore, the research objectives are addressed as follows: - To synthesize MnO 2 nanoparticles coated on calcined laterite; - Analyzing of MnO 2 nanoparticles formation portion and its physical structure; - To investigate the sterilization possibilities of created material; - To examine the mechanism of sterilization of MnO 2 coated on calcined laterite in water. 2.2 Materials and Research methods 2.2.1 Material and instruments All chemicals were reagent grade and they were used without further purification. Laterite ore was taken from coal and baked at 900 o C. Potassium permanganate (KMnO 4 ), ethanol, sodium hydroxide (NaOH, 98%), and hydrogen peroxide (H 2 O 2 ) were made in China. Agar was purchased from Ha Long company, endo agar from Merck. Petri disks, distilled water and others instruments which were used in the experiment, taken from Faculty of Chemistry lab equipment. For structural characterization, the samples were taken to use Transmission Electron Microscopy (TEM) operated at 80kV. Surface analysis was done using Scanning Electron Microscope (SEM) (Hitachi S-4800) in National Institute of Hygiene and Epidemiology. 2.2.2 Research methods 2.2.2.1 Synthesis of nano MnO 2 adsorbents According to Environmental Protection Agency (EPA) [23], particles are classified regarding to size: in term of diameter, coarse particles cover a range between 10,000 and 2,500 nanometers. Fine particles are size between 2,500 and 100 nanometers. Ultrafine particles, or nanoparticles are sized between 100 and 1 nanometers. Therefore, our goal is to create particles which have the size between 100 and 1 nanometers. The MnO 2 nanoparticles were synthesized using potassium permanganate (KMnO 4 ) as a precursor using a slight modification of method [24] in the following way: stirring vigorously a 100ml water:ethanol (1:1, v/v) solution using magnetic stirrer at room temperature for 10 min, and then the solution was added 5ml of KMnO 4 0.05M, stirring steady then put slowly H 2 O 2 until brown black color appears (around 10ml H 2 O 2 10%). Finally, colloidal nano MnO 2 solution was taken for analyzing of nanoparticles formation portion and coating on calcined laterite. To synthesize laterite/MnO 2 , the dried calcined laterite, which was grained with size of 0.1 – 0.5 mm diameter, was poured into MnO 2 nanoparticles solution with the volumetric portion of solid and liquid was 1/1. The soaking time was 8 to 24 hours. Then the liquid phase was drained off. Solid phase was washed out of dissolved ions and dried to get bacterial removing material (BRM). 2.2.2.2 Structural characterization For structural characterization, the samples were taken to use Transmission Electron Microscopy (TEM) operated at 80kV. TEM is a microscopy technique whereby a beam of electrons is transmitted through an ultra thin specimen, interacting with the specimen as it passes through. An image is formed from the interaction of the electrons transmitted through the specimen; the image is magnified and focused onto an imaging device, such as a fluorescent screen, on a layer of photographic film, or to be detected by a sensor. [25] Surface analysis was done using Scanning Electron Microscope (SEM). The SEM uses a focused beam of high-energy electrons to generate a variety of signals at the surface of solid specimens. The signals that derive from electron-sample interactions reveal information about the sample. [26] 2.2.2.3 Investigation of sterilizing capability of nano MnO 2 adsorbents The routine monitoring of the bacteriological quality of drinking water relies on the use of the indicator organisms Escherichia coli (E. coli) and coliforms which are used to indicate fecal contamination or other water quality problems such as failures of disinfection, bacterial regrowth within the distribution system or ingress. The most commonly employed technique for the detection of these organisms in water is membrane filtration. Normally, water (100ml) is concentrated by membrane filtration and the membranes placed onto a selective and differential medium such as Endo agar [27] which inhibits the growth of gram positive bacteria. Appropriately diluted (10 -2 ) sample (100mL in volume) volumes were filtered through 0.45µm membrane filters. Plates were then incubated for 24h at 37 o C on endo agar for total coliform. The bacteria number was determined in initial water sample and followed the time of sterilizing process. The experiments were performed in the static condition as well as the dynamic condition to estimate the sterilizing capability of MnO 2 nanoparticles. Specifically, contact time and the ratio between material and water sample were chosen as fundamental parameters. Therefore, other parameters which affect the alteration of contact time and the ratio between material and polluted water sample, such as the column height, the flow rate, etc in the dynamic condition, were taken into consideration. 2.2.2.4 Examine the mechanism of sterilization of MnO 2 coated on calcined laterite in water There are two main purposes in this part: One is to examine whether the mechanism of sterilization of MnO 2 coated on calcined laterite is influenced by the high oxidation potential of MnO 2 . The other is to survey the effects of Mn 2+ on sterilizing process of MnO 2 by changing the concentration of Mn 2+ . Chapter 3 RESULTS AND DISCUSSION 3.1 Synthesis of nano MnO 2 adsorbents The coating process was carried out as shown in Figure 3. Figure 1: Coating process The TEM images of MnO 2 nanoparticles solution clearly reveal the presence of a large quantity of nanoparticles and assemble to form barbed sphere shape with the diameter approximately 30nm (as shown in Figure 4-6) Soaking Sucking excess liquid Drying Washing Drying Dried laterite grains Nano solution [...]... q = 2.8 mL/min So EBCT = 10.17 2.8 = 3.63 mins In the case of the investigation, the minimum EBCT for safely bacterial sterilizing is 3.63 min 3.3 Mechanism of sterilization of MnO2 coated on calcined laterite in water 3.3.1 Investigation the influence of Mn2+ in sterilizing capability The experiment was performed to analysis the influence of Mn2+ on water sterilizing capability of MnO2 nanoparticles... there reformation of nanoparticles or inactivation, etc That confusion should be investigated in following time 3.2 Investigation of sterilizing capability of nano manganese dioxide In this research, total coliform was chosen as indicating bacteria for all bacterial removing investigation The bacteria number was determined in the initial water sample and followed the time of sterilizing process Static... nanoparticles Before coating, the surface of laterite was quite smooth; but after coating there were nanoparticles of MnO2 in barbed sphere shape distributed tight all over laterite surface The clinging of MnO2 nanoparticles on calcined laterite surface was recognized for application purpose, but the essence of this phenomenon was not determined so far There may were any chemical bond, what was binding energy,... 2: MnO2 nanoparticles with the magnification of 100000 times A: Before coating B: After coating Figure 7: Creation of adsorbent coating by nano MnO2 particles (100k) A: Before coating B: After coating Figure 3: Creation of adsorbent coating by nano MnO2 particles (200k) On SEM images in the same scale, it is easy to recognize different surface pictures of the material before and after coating MnO2 nanoparticles... different concentrations which are ranging 0.1, 1 and 10 ppm of Mn2+ were put into water samples with the available of MnO2 nanoparticles material The processes were conducted in static condition (100mL waste water was treated by 0.5g BRM; contact time was 10 minutes; initial MPN in wastewater was 380) The results are shown in Table 5, Figure 20-21 Table 5: Influence of Mn2+ in sterilizing capabilities... dynamic condition were chosen to conduct the experiments 3.2.1 Investigation in static condition 3.2.1.1 Influence of detention time on bacteria sterilizing Detention time is an important parameter to determine the sterilizing ability In this experiment, the raw water was treated, diluted then the material is poured into polluted water solid:liquid=2g:100ml in conical beakers with the phase ratio of (BRM:polluted... Critique of the Schellmann: Definition and Classification of Laterite Catena 2002 47: p 117-131 16 Mamindy-Pajany, Arsenic adsorption onto hematite and goethite Comptes Rendus Chimie, 2009 12(8): p 876-881 17 S.V., D., Removal of arsenic from synthetic groundwater by adsorption using the combination of laterite and iron-modified activated carbon Journal of Water and Environment Technology 2008 6(1):... H., Yin, Z and B Wu, Pressure Acid Leaching of a Chinese Laterite Ore Containing Mainly Maghemite and Magnetite Hydrometallurgy In Press 19 Mohapatra, M., Khatun, S and S Anand, Kinetics and Thermodynamics of Lead (II) Adsorption on Lateritic Nickel Ores of Indian Origin Chem Eng J., 2009 155: p 184-190 20 Yu, X., Zhu, L., Guo, B and S He, Adsorption of Mercury on Laterite from Guizhou Province, China... performance in treating by nano MnO2 adsorbent 4 Conclusions - The nano MnO2 solution was prepared as 2.2.2.1 The TEM images of solution clearly reveal the presence of a large quantity of MnO 2 nanoparticles with lozenge shape and barked sphere with the diameters around 30nm - The BRM was prepared from calcined laterite and nano MnO 2 solution The SEM images of material’s surface shows the distribution of barked... obtains some positive results in creating a new material for wastewater sterilization, which may account for the global effort of saving clean water resources – which is currently one of the most concerning issues not only in Vietnam but also in other countries However, in order to apply those study results in the real world, it is still required further investigations on the mechanism and the harms of . Evaluation of sterilization possibility in water environment of activated nano MnO 2 coated on calcined laterite Cao Việt . taken into consideration. 2.2.2.4 Examine the mechanism of sterilization of MnO 2 coated on calcined laterite in water There are two main purposes in