evaluation of sterilization possibility in water environment of activated nano mno2 coated on calcined laterite

Cao Việt EVALUATION OF STERILIZATION POSSIBILITY IN WATER ENVIRONMENT OF ACTIVATED NANO MnO2 COATED ON CALCINED LATERITE CHUYÊN NGÀNH: QUẢN LÝ CHẤT THẢI VÀ XỬ LÝ VÙNG Ô NHIỄM CHƯƠNG TR

Cao Việt

EVALUATION OF STERILIZATION POSSIBILITY IN WATER ENVIRONMENT OF ACTIVATED NANO MnO2 COATED ON CALCINED

LATERITE

CHUYÊN NGÀNH: QUẢN LÝ CHẤT THẢI VÀ XỬ LÝ VÙNG Ô NHIỄM

(CHƯƠNG TRÌNH ĐÀO TẠO QUỐC TẾ)

LUẬN VĂN THẠC SĨ KHOA HỌC

GIÁO VIÊN HƯỚNG DẪN: PGS.TS TRẦN HỒNG CÔN

Abbreviation i

List of Figures ii

List of Tables iii

Chapter 1 1

INTRODUCTION 1

1.1 Water situation in general 1

1.2 Water sterilization 3

1.2.1 Boiling 4

1.2.2 Chlorine 5

1.2.3 Ozone 5

1.2.4 Ultraviolet light 6

1.2.5 Hydrogen peroxide 7

1.2.6 Solar disinfection 7

1.2.7 Photocatalysis on semiconductors 7

1.2.8 High speed water sterilization using one-dimensional nanostructures 7

1.3 Nanotechnology 8

1.4 Manganese dioxide 10

1.5 Laterite 11

Chapter 2 13

OBJECTIVES AND RESEARCH METHODS 13

2.1 Objectives 13

2.2 Materials and Research methods 13

2.2.1 Material and instruments 13

2.2.2 Research methods 14

RESULTS AND DISCUSSION 17

3.1 Synthesis of nano MnO2 adsorbents 17

3.2 Investigation of sterilizing capability of nano manganese dioxide 23

3.2.1 Investigation in static condition 24

3.2.2 Investigation in dynamic condition 28

3.3 Mechanism of sterilization of MnO2 coated on calcined laterite in water 33

3.3.1 Investigation the influence of Mn2+ in sterilizing capability 33

3.3.2 Examine the mechanism of sterilization of MnO2 35

Chapter 4 38

CONCLUSION 38

REFERENCES 40

DNA Deoxyribonucleic Acid

SODIS Solar Disinfection

CNT Carbon Nanotube

AgNWs Silver Nanowires‟

TEM Transmission Electron Microscopy SEM Scanning Electron Microscope EPA Environmental Protection Agency

E coli Escherichia coli

BRM Bacteria removing material

MPN Most probable number

EBCT Empty Batch Contact Time

Figure 4: MnO2 nanoparticles with the magnification of 40000 times 19

Figure 5: MnO2 nanoparticles with the magnification of 60000 times 20

Figure 6: MnO2 nanoparticles with the magnification of 100000 times 21

Figure 7: Creation of adsorbent coating by nano MnO2 particles (100k) 22

Figure 8: Creation of adsorbent coating by nano MnO2 particles (200k) 22

Figure 9: Shaking equipment for static condition investigation 23

Figure 10: Column device for dynamic condition investigation 24

Figure 11: Samples in contact time‟s influence experiment 25

Figure 13: Samples in BRM/water ratio‟s influence experiment 27

Figure 14: Samples in BRM/water ratio‟s influence experiment 28

Figure 15: Model of column device 29

Figure 16: Samples in flow rate in BRM column‟s influence experiments 30

Figure 17: Influence of flow rate on bacteria sterilizing in BRM column 30

Figure 18: Samples in the experiments 32

Figure 19: Influence of column height on bacteria sterilizing in BRM column 32

Figure 21: Influence of Mn2+ in sterilizing capabilities 35

Table 3: Influence of flow rate on bacteria sterilizing in BRM column 29 Table 4: Influence of column height on bacteria sterilizing in BRM column 31 Table 5: Influence of Mn2+ in sterilizing capabilities 34

Chapter 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]

The contamination of ground water (mostly by toxic metal ions due to both natural and anthropogenic reasons) is also one of concerning issues on clean water It is necessary to assess the quality of water used in industry, household activities and drinking purpose Understanding of the importance of clean water

in human life, many countries has gradually adjusted their environmental regulations more stringently to reserve clean water resources With the purpose

of overcoming the water pollution problems, and to meet the stricter environmental regulations, scientists and researchers have focused on improving exist water purification processes and approaching to alternative water treatment technologies as well, so as to increase the efficiency of those decontamination methods It is surveyed that human awareness about the seriousness of water pollution has enhanced over the world People have also started realizing that water is not an unlimited resource, hence it needs to be protected and smartly used

An ideal water treatment process should have the capability to mineralize completely all the toxic organic components without leaving behind any harmful by-products and to recover all toxic metals from wastewater In broader classification, biological, mechanical, thermal, chemical or physical treatments,

or their combinations may be applied to purify contaminated water The choice

of the proper water treatment processes depend on the nature of the pollutants presenting in water, and on the acceptable contamination level in treated water There are two main purposes of water treatment study – the reduction of contaminant level in the discharged stream to meet environmental standards, and

the purification of water to ultrapure water in order to be able to use in semiconductor, microelectronic and pharmaceutical industries Moreover, the cost or effectiveness of the water treatment processes also plays a significant role

in choosing a particular one Biodegradation, adsorption in activated carbon, air stripping, incineration, ion-exchange, coagulation-precipitation, membrane separation, thermal and catalytic oxidation, oxidation by permanganate, chlorine, ozone and hydrogen peroxide are widely applied in conventional water treatment processes for organic and inorganic pollutant containing water Besides advantages, each process has their own shortcomings which are being improved gradually via new technologies [1, 2]

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]

It is not totally accurate to assess whether water is of an appropriate quality only

by visual examination Simple procedures such as boiling or the use of a household activated carbon filter are not sufficient for treating all the possible contaminants that maybe present in water from an unknown source Even natural spring water – considered safe for all practical purposes in the 1800s – must now

be tested before determining what kind of treatment, if any, is needed Chemical

analysis, while expensive, is the only way to obtain the information necessary for deciding on the appropriate method of purification [3]

Simple techniques for treating water at home, such as chlorination, filters, and solar disinfection, and storing it in safe containers could save a huge number of lives each year

Sterilization is accomplished both by filtering out harmful microbes by and also adding disinfectant chemicals in the last step in purifying drinking water Water

is disinfected to kill any pathogens which pass through the filters Possible

pathogens include viruses, bacteria, including Escherichia coli, Campylobacter and Shigella, and protozoa, including Giardia lamblia and other cryptosporidia

In most developed countries, public water supplies are required to maintain a residual disinfecting agent throughout the distribution system, in which water may remain for days before reaching the consumer Following the introduction

of any chemical disinfecting agent, water is usually held in temporary storage - often called a contact tank or clear well to allow the disinfecting action to complete [4]

1.2.1 Boiling

Boiling is an easy, cheap and common way to eliminate contaminations and microorganisms in developing countries, but this method is only practical for small amounts When the water has boiled for 5 – 10 min all the pathogens have been killed and the water is safe to drink [2]

The main disadvantage of this method is that it requires a continuous source of heat and appropriate equipment

1.2.2 Chlorine

Chlorine is most effective against pathogens and not as much for turbidity; it will function relatively effectively up to 20 NTU [2] If chlorine were combined with other methods such as rapid sand filtration the turbidity would decrease Chlorine Bleach can be used to purify water with the dosage of 1 part of bleach and 10 parts of water and wait for 30 min, or longer if the solution still looks cloudy [3] It is important to note that chlorine bleach does not kill

Cryptosporidium and may not kill Giardia, a pathogen and a parasite that both

give diarrheal diseases [5] It is difficult to determine the correct chlorine dosage, too much gives an unpleasant taste and people will be reluctant to drink it, but a too small dosage will not kill the germs [4]

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

Ozone (O3) is an unstable molecule which readily gives up one atom of oxygen providing a powerful oxidizing agent which is toxic to most waterborne organisms It is a very strong, broad spectrum disinfectant that is widely used in

Europe It is an effective method to inactivate harmful protozoa that form cysts

It also works well against almost all other pathogens Ozone is made by passing oxygen through ultraviolet light or a "cold" electrical discharge To use ozone as

a disinfectant, it must be created on-site and added to the water by bubble contact Some of the advantages of ozone include the production of fewer dangerous by-products (in comparison to chlorination) and the lack of taste and odor produced by ozonization Although fewer by-products are formed by ozonation, it has been discovered that the use of ozone produces a small amount

of the suspected carcinogen bromate, although little bromine should be present in treated water Another of the main disadvantages of ozone is that it leaves no disinfectant residual in the water Ozone has been used in drinking water plants since 1906 where the first industrial ozonation plant was built in Nice, France The U.S Food and Drug Administration has accepted ozone as being safe; and it

is applied as an anti-microbiological agent for the treatment, storage, and processing of foods [6]

The disadvantage of this method is the high cost for operation

1.2.4 Ultraviolet light

Ultraviolet light is very effective at inactivating cysts, as long as the water has a low level of colour so the UV can pass through without being absorbed Ultraviolet light works against viruses, bacteria, pathogens and other potentially harmful particles by modifying and even destroying their nucleic acids and disrupting their deoxyribonucleic acid (DNA) When employed in a UV filter,

UV light can have two effects on these microorganisms It can either eliminate their ability to reproduce, or can kill them outright, a more desirable outcome where water purification is concerned

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]

The main disadvantages of this methods is the low efficiency and the dependent

on water turbidity

1.2.5 Hydrogen peroxide

Hydrogen peroxide (H2O2) 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:

Health and medicine - With advances in diagnostic technologies, doctors will

be able to give patients complete health checks quickly and routinely If any

medication is required this will be tailored specifically to the individual based on their genetic makeup, thus preventing unwanted side-effects As a result, the health system will become preventative rather than curative

Society and the environment - Renewable energy will become the norm For

example, solar cells based on quantum dots could be as much as 85% efficient Wind, wave, and geothermal energy will also be tapped more effectively using new materials and stored or delivered more efficiently through advances in batteries and hydrogen fuel cells New ambient sensor systems will allow us to monitor our effect on the environment and take immediate action, rather than

“waiting to see” Nanotechnology will also help us clean up existing pollution and make better use of the resources available to us

New materials - Nanomaterials such as quantum dots, carbon nanotubes and

fullerenes will have applications in many different sectors because of their new properties So quantum dots can be used in solar cells, but also in optoelectronics, and as imaging agents in medical diagnostics Carbon nanotubes can be used in displays, as electronic connectors, as strengthening materials for polymer composites, and even as nanoscale drug dispensors Fullerenes can be used in cosmetics, as “containers” for the delivery of drugs, in medical diagnostics, and even as nanoscale lubricants

Figure 1: Nanoscale materials

Nanoscale materials and devices hold great promise for advanced diagnostics, sensors, targeted drug delivery, smart drugs, screening and novel cellular therapies [7]

The future of nanotechnology has great potential However, it also has the potential to change society more than the industrial revolution It will affect

everyone and so should be developed for everyone

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…)

When laterite heated to 420-900oC, 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 MnO2 have a large surface area and high oxidation potential which make them excellent candidates for the bacterial removal in general

Chapter 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 MnO2 nanoparticles coated on calcined laterite;

- Analyzing of MnO2 nanoparticles formation portion and its physical structure;

- To investigate the sterilization possibilities of created material;

- To examine the mechanism of sterilization of MnO2 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 900oC Potassium permanganate (KMnO4), ethanol, sodium hydroxide (NaOH, 98%), and hydrogen peroxide (H2O2) 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

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 MnO2 nanoparticles were synthesized using potassium permanganate (KMnO4) 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 KMnO4 0.05M, stirring steady then put slowly H2O2 until brown black color appears (around 10ml H2O2 10%) Finally, colloidal nano MnO2

solution was taken for analyzing of nanoparticles formation portion and coating

on calcined laterite

To synthesize laterite/MnO2, the dried calcined laterite, which was grained with size of 0.1 – 0.5 mm diameter, was poured into MnO2 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]

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

37oC 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 MnO2 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

laterite in water

There are two main purposes in this part: One is to examine whether the mechanism of sterilization of MnO2 coated on calcined laterite is influenced by the high oxidation potential of MnO2 The other is to survey the effects of Mn2+

on sterilizing process of MnO2 by changing the concentration of Mn2+

Chapter 3 RESULTS AND DISCUSSION 3.1 Synthesis of nano MnO 2 adsorbents

Working solution of MnO2 nanoparticles was prepared by stirring solution of 50ml distilled water and 50ml ethanol Afterwards, the solution was added 5ml KMnO4 0.05M, stirring steadily then dropped slowly H2O2 solution into the solution until brown black color appears (around 10ml H2O2 10%) The experiment product, colloidal nano MnO2 solution, was taken for analyzing of nanoparticles size and formation portion by Transmission Electron Microscopy (TEM)

The dried calcined laterite grains with size of 0.1 – 0.5 mm diameter were poured into nanosilver solution The volumetric portion of solid and liquid was 1:1 The soaking time was from 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) The surface of solid phase was characterized using Scanning Electron Microscope (SEM) to obtain information on its physical structure

Consequently, the coating process was carried out as shown in Figure 3