Ammonium removal from aqueous solution by silver nano particles

THAI NGUYEN UNIVERSITY UNIVERSITY OF AGRICULTURE AND FORESTRY VU TRA GIANG AMMONIUM REMOVAL FROM AQUEOUS SOLUTION BY SILVER NANO PARTICLES BACHELOR THESIS Study Mode: Full-time Maj

THAI NGUYEN UNIVERSITY

UNIVERSITY OF AGRICULTURE AND FORESTRY

VU TRA GIANG

AMMONIUM REMOVAL FROM AQUEOUS SOLUTION BY

SILVER NANO PARTICLES

BACHELOR THESIS

Study Mode: Full-time

Major: Environment Science and Management

Faculty: Advanced education program office

Thai Nguyen University of Agriculture and Forestry

Degree Program Bachelor of Environmental Science and Management Student name Vu Tra Giang

Thesis title Ammonium removal from aqueous solution by silver

nano particles Supervisor(s) Dr Van Huu Tap (Thai Nguyen University of Science)

Supervisor’s signature (s)

Abstract: NH4+ is a pollutant from human activities that affects the health of plants,

animals and human It’s very important to remove it from contaminated waters This study aims at synthesizing silver nanoparticles (AgNPs) by chemical reduction method In this work, silver nanoparticles were prepared using silver nitrate with a reducing agent is sodium borohydride and Poly Vinyl Pyrrolidone (PVP) which is used as stabilizing agents The size of crystalline for AgNPs was measured by UV–vis spectroscopy and flourier transform infrared (FTIR) The properties of nano-silver particles (AgNPs) have been studied using scanning electron microscope (SEM) The capability of nanoparticles to remove NH4+ from contaminated solution

was then studied Parameters like types of AgNPs, pH of ammonium solution, contact time, adsorbent dosage and initial ammonium concentration were studied Ammonium removal increased when increased in the adsorbent dosage (from 0.228

mg/25mL to 2.28 mg/25mL), pH from 3 to 9, contact time from 5 to 60 and decreased in initial concentration of NH4+ The most appropriate conditions for

Ammonium adsorption onto AgNPs in batch experiments obtained at pH 9, contact time of 60 min, 1.824 mg AgNPs/25 mL of Ammonium solution with initial concentration of 5 mg/ L At this condition, the highest adsorption capacity of Ammonium onto AgNPs reached 100.48 mg/g Isotherm adsorption was also described by the Langmuir model with a constant correlation (R2) is 0.9339 With highest R2 (0.885), the adsorption kinetic of Ammonium onto AgNPs obeyed

Elovich model with the chemical sorption process

ACKNOWLEDGEMENT

I would like to express my special thanks of gratitude to Dr Van Huu Tap who in spite

of being extraordinarily busy with his duties, took time out to hear, guide, keep me on the correct path and complete report during the time of conducting the research, which also helped me know about so many new things I am really thankful to him

I would also like to express my great appreciation to Dr Vu Xuan Hoa for his constant support, patient guidance and suggestions related to my work

Finally, I would also like to thank my parents and friends who helped me a lot in

finalizing this project within the limited time frame

Thank you all very much!

Thai Nguyen, August 2018

Student

Vu Tra Giang

TABLE OF CONTENTS

ACKNOWLEDGEMENT iii

LIST OF FIGURES vi

LIST OF TABLES vii

LIST OF ABBREVIATIONS viii

PART I INTRODUCTION 1

1.1 Research rationale 1

1.2 Research’s objectives 2

1.3 Research’s questions and hypothesizes 2

1.4 Limitations 3

PART II LITERATURE REVIEW 4

2.1 Ammonium ion 4

2.1.1 Ammonium ion in water 4

2.1.2 Sources of Ammonium pollution 5

2.1.3 Standard of Ammonium ion in water 7

2.2 Effect of Ammonium 8

2.3 Silver nanoparticles 8

2.4 Adsorption 9

2.5 Research projects on ammonium treatment 10

PART III METHODOLOGY 11

3.1 Materials 11

3.1.1 Laboratory instruments 11

3.1.2 Ammonium NH 4 + solution 11

3.1.3 Preparation of adsorbent (AgNPs) 11

3.2 Adsorption experiments of Ammonium (NH4+) onto AgNPs 12

3.2.1 Method of ammonium analysis 14

3.2.2 Measurements 15

3.2.3 Data analysis 16

PART IV RESULTS AND DISSCUSSION 17

4.2 Effect of type AgNPs 19

4.3 Effect of pH 19

4.4 Effect of contact time 21

4.5 Effect of adsorbent dose 23

4.6 The effect of NH4+ concentrations 24

4.7 Adsorption isotherm 25

4.8 Adsorption kinetics of AgNPs 29

PART V CONCLUSIONS 33

REFERENCES 34

LIST OF FIGURES

Figure 1: The relationship between Ammonia Ionization and pH 5

Figure 2 Characteristic of AgNPs: (a) The absorption spectra of silver solution; (b) The TEM image of the AgNPs; (c) The distribution of AgNPs size obtained from Fig 2b; (d) FTIR spectra of pure starch and ST0.2 sample; (e) XRD patterns of synthesized AgNPs 18

Figure 3 Effect of types of AgNPs on adsorption of Ammonium 19

Figure 4 Effect of pH on adsorption of Ammonium by AgNPs 21

Figure 5 Effect of contact time on adsorption of Ammonium by AgPNs 22

Figure 6 Effect of AgPNs dose on adsorption of Ammonium 23

Figure 7 Effect of initial Ammonium concentration 25

Figure 8 Equilibrium adsorption prediction of Ammonium on AgNPs by Langmuir and Freundlich models (contact time= 60 min, Co =10 mg/L) 27

Figure 9 Kinetics modelling of NH4+ sorption onto AgNPs (Co: 10 mg/L; adsorbent dose: 1.6 mL/25 mL; initial pH: 9) 31

LIST OF TABLES

Table 1: Adsorption isotherm parameters and correlation coefficients of Langmuir and

Freundlich models for Ammonium adsorption on AgNPs 28

Table 2: Calculated kinetic parameters of models of Ammonium adsorption on

AgNPs 30

PART I INTRODUCTION

1.1 Research rationale

The treatment of nitrogen compounds (nitrate, nitric and ammonia nitrogen) directly from water plants or indirectly from agriculture and filtering from sludge into landfill and fields led to eutrophication of the muscles, water body It has been widely reported that ammonium nitrate (NH4+-N) is a very common chemical species in aquatic

ecosystems and its toxic effect on life is very high (Haseena.P.V et al., 2016)

Water contains ammonium, nitrite, and nitrate, the result of the decomposition of organic matter or pollution from waste water In particular, ammonium is the most toxic for fish and aquatic species Nitrite is formed from the reaction of organic and ammonium nitrate and with the participation of bacteria The nitrite is then oxidized to nitrate In addition, nitrate is present in the water source due to wastewater from the chemical industry, from the field using chemical fertilizers, landfill leaks, and rain water runoff The presence of nitrogen compounds in the chemical composition of water indicates signs of water pollution Clean water standards specify that ammonium

is less than 3 mg/l The drinking water standard specifies that Ammonium is less than 1.5 mg/l (WHO)

Ammonium itself is not too toxic to the body, but if it is present in water at levels beyond the allowed standard it can be transformed into carcinogens and other dangerous diseases Studies have shown that 1g of ammonia is converted to 2.7 g of nitrite and 3.65 g of nitrate while the content of nitrite is 0.1 mg / liter and nitrate is 10-50 mg / liter (Europura, 2016)

Ammonium contamination in the groundwater as a source of water for living has been studied in many areas, many countries in the world There are many methods, such as biological, physical, chemical, or a combination of these methods, have been developed for the removal of ammonium from wastewaters

In order to solve the defects of traditional absorbents, nanomaterials were used as novel substances to remove pollutants from water and wastewater Materials of size from 1 nm to 100 nm are defined as nanomaterials With its properties dependent on shape and fiction, nanomaterials have been extensively studied for more than a decade

In recent years, the development of nanoscale science and nanotechnology has shown significant potential in overcoming environmental problems (Lee J et al., 2010, Ali I 2012) Compared with traditional materials, nanocomposite adsorbent have shown higher efficiency and faster water treatment rates

1.2 Research’s objectives

In recent years, the method of adsorption is receiving much attention from researchers

to contribute to eliminating environmental pollution However, studying the adsorption capacity of AgNPs in water treatment is a new direction, not much research work AgNPs are a small size material that is able to retain some of the substance This surface can be an absorbent material Therefore, in this study, AgNPs were synthesised and used to remove ammonium in aqueous solution by adsorption method in laboratory condition

1.3 Research’s questions and hypothesizes

1 What kind of AgNPs has effect on Ammonium absorption?

2 What are the optimal conditions to have the best effect?

1.4 Limitations

In the laboratory do not have enough machines therefore; some parts have to send to another laboratory in Hanoi to get the result

PART II LITERATURE REVIEW

2.1 Ammonium ion

2.1.1 Ammonium ion in water

Nitrogen is an important factor of the biogeochemical cycle, involving the transfer of essential nutrients from living organisms to the environments and vice versa The biological cycle of nitrogen consists of both natural and man-made components and it

is subject to great complexity due to the variety of compounds and associated variations (Dekker et al., 2000, Franson et al., 2005) In water, dissolved ammonia exists in two types of equilibrium: free ammonia (NH3) and dissolved ammonium

(NH4+) (Waite et al., 1984)

NH4+ H2O ↔ NH3 H3O+ The NH3 - NH4+ balance is extremely dependent on pH and at lower levels of salinity

and temperature At typical pH of natural waters, NH4+ is dominant (Lee J et al.,

2010)

From the Fig.1, the pH is low, the equilibrium shifts to the right: more ammonia molecules are transferred into ammonium ions Conversely, if the pH value of water is high (the concentration of hydrogen ions is low), the equation shifts to the left: the hydroxide ion isolates a proton from the ammonium ion, which create ammonia

Sourse: http://www.aqtinfo.com

Figure 1: The relationship between Ammonia Ionization and pH

2.1.2 Sources of Ammonium pollution

Ammonium is produced from both natural and human sources Although natural sources are responsible for most of its content in the country, human origins have been greatly increased in the last century (Dekker et al., 2000, Franson et al., 2005 and Waite et al., 1984)

There are many causes of ammonium contamination in the groundwater but one of the main causes is the overuse of organic fertilizers, pesticides, chemicals and plants They damage to water sources, or the decomposition of organic compounds and substances that accelerate ammonium contamination in the groundwater In addition, the level of pollution depends on the type of cultivation of each area (Nguyen Viet Anh, 2005)

 Due to geological structure and history of stratigraphic formation

The results of geological activities (erosion, etc.) have formed on the Quaternary pebble aquifer This is the main source of water used to supply water for living activities of people The fourth floor consists of many types of tectonics with different sediments of origin Generally, these layers contain peat particles, soils with organic compounds The ability to move dirt into the water is closely related to the grain composition Particularly dried particles have greater flow, small absorption capacity, easy to move dirt, fine particles and the opposite

As the process of extracting water expands, the release of nitrogen-containing compounds is generated in the muddy soil that contains many decomposing organic substances, which results in increased nitrogen content in the groundwater

 Due to the existence of pollution sources located above the ground

Over the years, with the development of social life, the development of industry and agriculture we have emitted into the environment a large amount of waste, including both water and wastewater They have high levels of organic pollutants

In addition, the extraction of the groundwater with large volumes of new water cannot

be timely and has created the hopper to lower the water level, which also contributes to the penetration of dirt faster In order to compensate for the amount of groundwater being extracted, the natural erosion process is accelerated, and the groundwater is supplemented by seepage from surface water This is the cause of increased levels of pollutants in groundwater by artificial origin Due to the discharge of large amounts of wastes, wastewater containing many water-soluble nitrogen-containing compounds results in an increase in the concentration of nitrogen in surface water as the product of

urea, ammonium and salt production Ammonium from fertilizers, from rotting and from domestic wastewater and industrial effluent These substances, by surface water, penetrate downwards from the top or through the sides of rivers, penetrate the groundwater to increase the concentration of ammonium in groundwater

 Due to the ventilation zone thickness

When the thickness of the ventilation zone (or infiltration thickness) is reduced, the possibility of penetrating contaminants into the aquifer is higher But for nitrate and nitrite alone, the thickness of the aeration zone is too great, the nitrification process is favorable, and the thickness of the aeration zone is too small, the nitrification process

is weaker

In reality, as the zone of ventilation becomes thicker, the amount of oxygen entering the atmosphere and other sources on the ground into the ventilation zone will be large, facilitating the favorable conditions for the development of the micro Aerobic bacteria

As a result, nitrification occurs and NO2 and NO3 levels increase

 Due to the large hydraulic slope

Areas with strong currents increase the penetration of pollutants into groundwater Areas below steep slopes tend to have higher levels of contamination than low slopes This is consistent with the laws of physical motion of matter

2.1.3 Standard of Ammonium ion in water

For ammonium in drinking water, an indicator parameter of 0.50 mg/L has been laid down in the European Union legislation The indicator parameter has been set based

on technological reasons and does not imply a health concern at concentrations higher than 0.50 mg/L (European Food Safety Authority, 2012)

2.2 Effect of Ammonium

When exceeded, ammonia leads to excessive biomass growth, disturbing the ecological balance of the water column Although micronutrients, ammonia causes many side effects in living organisms (Dekker, 2000, Franson, 2005 and Waite, 1984)

With ammonium chloride, the acidic effects of chloride ions seem to be of greater importance than ammonium ions Ammonium chloride affects metabolism by shifting acid-base balances, impaired glucose tolerance and reduced insulin-sensitization at doses above 100 mg/kg body weight per day (33.7 mg ammonium ion/kg body weight per day) (US Environmental Protection Agency, 1989)

The main biological effect of nitrite in humans is its involvement in the normal oxidation of Hb to methaemoglobinaemia, which cannot transport oxygen to tissues Oxygen reduction becomes clinically apparent when the concentration of methamphetamine reaches 10% of normal Hb concentration; this condition, called methaemoglobinaemia, causes cyanosis and, at higher concentrations, causes asphyxia Normal human hemoglobin levels are below 2%; in infants less than 3 months old, less than 3% (WHO, 2011)

2.3 Silver nanoparticles

Nanotechnology is an important part of modern research relating to design, synthesis, and manipulation of particle structures ranging from approximately 1-100 nm

Nowadays, Nanoparticles (NPs) applied in wide range areas such as medicine, manufacturing and materials, environmental health, energy and electronics (Understanding nano, 2018)

Silver nanoparticles (AgNPs) have been applied in various fields, including medical, food, health care, consumer, and industrial purposes and environment due to their unique physical and chemical properties For the environment, silver nanoparticles are antimicrobial agent as well as in the removal of pollutants and toxic materials (e.g Methylene Blue, Iodide and bromide ions, Bacterial pathogen) (Park J Y et al., 2011, Polo M S et al., 2006, Krishna S et al., 2009,)

2.4 Adsorption

Absorption is a surface phenomenon where the adsorbent is a sticky substance to another substance on its surface A substance which accumulates on the surface of adsorbent is named adsorbate Adsorption can be a chemical or physical process, or a combination of them, occurs at the boundary of two phases, such as liquid - solid, gas - solid, gas - liquid or liquid – liquid (Fomkin A, 2009) In other words, the adsorption is

a change in the concentration of a certain substance (e.g contaminant) at an interface with an initial reduction in concentration Adsorption has importance for industries which work with air and water purification

2.4.1 Adsorption capacity

Adsorption capacity (q) is the amount of adsorbed substance (adsorption) by 1 gram of solid adsorbent (Le Van Cat, 1999) calculated as:

Where:

q: amount of adsorbed material (mg / g)

C0, C: initial concentration and concentration of adsorbed substance (mg / l)

V: volume of solution (l)

m: weight of absorbent (g)

2.4.2 Adsorption effeciency

Adsorption efficiency (H) is the ratio between the concentration of the adsorbed

solution (C) and the initial solution concentration C0 (Mohammad et al., 2011)

2.5 Research projects on ammonium treatment

Many methods, such as biology, physics, chemistry, or combination of these methods, have been developed to remove ammonium from wastewater and other point sources They mainly include ion exchange and adsorption, biotechnology, dechlorination, chlorination, chemicals, reverse osmosis, microwave radiation, and supercritical water oxidation (Bermejo et al., 2008; Bernet et al., 2000; Bodalo et al., 2005; Booker et al., 1996; Guštin and Marinšek-Logar, 2011; Huang et al., 2015a; Lin et al., 2009;

Siegrist, 1996; Turan, 2016)

PART III METHODOLOGY

 UV-VIS Visible Spectrometer (Hitachi Z 2000, Japan)

 Shaker machine (HY 2A, China)

 pH meter (Hanna HI 9025, Romania)

3.1.3 Preparation of adsorbent (AgNPs)

There were 6 kinds of AgNPs used in this study:

1:16 GLED 1h GLED 1h30 GLED 2h30 GLED 3h30 SEED

Nanosized metal colloids are synthesized by reduction method

Chemical reduction of silver nanoparticles involves the reduction of a silver salt (silver nitrate) with a reducing agent is sodium borohydride in the presence of colloidal stabilizer Sodium borohydride has been used with Poly Vinyl Pyrrolidone (PVP) which is used as stabilizing agents

The synthesis of colloidal silver nanoparticles (AgNPs) was performed using NaBH4

as the reducing agent First, a 100 ml of a 10-3M solution of AgNO3 were mixed with

the amount of 0.2 g of PVP to generate starch solutions containing Ag+ ions Second,

the solution was stirring vigorously on a magnetic stirrer at 70o C to ensure that the

mixture was homogeneous While the solution was stable at 70oC, a 25 ml of 10-3 M

sodium borohydrides solution was added gradually (drop by drop) to the solution There acted solutions then cooled to room temperature The chemical reaction is the sodium borohydride reduction of silver nitrate (Sally D S et al., 2007)

AgNO3+ NaBH4 →Ag0 + 1

2 H2+ 1

2 B2H6 + NaNO3

The PVP containing Ag+ solutions turned to light yellow after the addition of the

sodium borohydrides solution and to brighter yellow when all of the sodium

borohydride solution had been added The overall reaction process was carried out in the dark box to avoid unnecessary photochemical reaction (Benjamin L O et al., 2015)

3.2 Adsorption experiments of Ammonium (NH 4 + ) onto AgNPs

Experiments were performed by using batch modes A suck out of AgNPs was placed into 100 mL conical flasks containing 25 mL of solution with concentrations

of NH4+ was 10 mg/l The adsorption experiments of NH4+ were conducted in batch

shake-flasks shaken at 120 rpm orbital for 60 min, at room temperature (25±20C)

The effects of pH on NH4+ adsorption onto AgNPs were conducted by putting 1.14mg

of AgNPs in 25 mL of solution containing 10mg/L of NH4+ in 100 mL conical flasks PH were adjusted between 3 and 10 using either H2SO4 1M or NaOH 1M

solution The conical flasks containing NH4+ solution were shaken for 60 min at 120

rpm orbital, at room temperature (25±20C)

The effects of contact time on adsorption capacity of NH4+ were conducted with

changing of contact time from 5 to 180 min with the optimal of NH4+ pH value determined in above experiments with 1.14 mg of AgNPs in 25 mL of solution (10mg/l) The mixtures were placed in to 100 mL conical flasks and then were shaken

at 120 rpm orbital, at room temperature (25±20C)

Effects of AgNPs doses on adsorption of NH4+ were performed by putting a dose of

AgNPs varying in range from 0.2 to 2 ml (0.228 mg – 2.28 mg) AgNPs/25 mL of

NH4+ solution with concentration of NH4+ was 10mg/l The experiments also were

adjusted to optimal pH value and contact time that was determined as above described experiments The conical flasks were shaken at 120 rpm orbital for optimal contact time, at room temperature (25±20C)

The effects of initial NH4+ concentrations were evaluated by placing each 25 mL solution containing NH4+ adjusted to an optimum pH value that was

determined in above described experiments with varying of initial concentrations from

5 to 80 mg /L into 100 mL conical flasks with optimal dose of AgNPs Finally, the conical flasks were shaken at 120 rpm orbital for optimal contact time, at room temperature (25±20C)

3.2.1 Method of ammonium analysis

To determine the amount of NH4 + remaining after the experiment, we went to color directly with Nessler reagent

 Scope of application

Ammonia that is present in water is due to the decomposition of organic matter under anaerobic conditions, or water contaminated by the waste This method is used to determine the content of ammonia for surface water, water supply, wastewater and natural water such as rain water and groundwater

of the test solution measured at 450 nm

We have a reaction:

2K2HgI4 + NH3 + 3KOH → Hg(HgIONH2) + 7KI + 2H2O (yellow) 2K2 HgI4 +

NH + KOH → Hg(HgI NH ) + 5KI + H O (yellowish brown)

But natural water often contains Ca2+ ions, Mg2+ ions (hard water) In strong bases,

these ions form hydroxides in the colloidal form, causing the solution to melt away To overcome this phenomenon, use Seignett salt (KNaC4H4O6), or EDTA for analysis, so

that these salts combine with Ca2+ and Mg2+ ions to form soluble, colorless solvents in

solution

M+ + KNaC4H4O6→ K+ + Na+ + MC4H4O6

M2+ + Na2H2I → Na2MI + 2H+

 Impact of obstruction

 Iron ions, the high hardness of the water cause the reaction to react This factor

is eliminated by Natri Kalitartrat

 Chlorinated water interferes with the colorimetric process, so samples should be filtered before analysis and use of 5% zinc sulphate solution

 Excess chlorine in water at high concentrations reduces the amount of ammonia

in the sample, so it is necessary to remove excess chlorine in water with a 5% sodium thiosulfate solution

 Conditions to proceed

 After creating the conditions for the sample, allow the solution to stand for 10

to 15 minutes for maximum color intensity

 Glassware should be cleaned with a rinse solution and then thoroughly rinsed with distilled water

3.2.2 Measurements

NH4+ concentrations in the bulk reactor suspensions of all samples in the above