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MINISTRY OF EDUCATION AND TRAINING VIETNAM ACADEMYOF SCIENCE AND TECHNOLOGY GRADUATE UNIVERSITY SCIENCE AND TECHNOLOGY ……..….***………… Nguyen Vu Ngoc Mai STUDY ON SYNTHESIS OF MANGANE

MINISTRY OF EDUCATION AND

TRAINING

VIETNAM ACADEMYOF SCIENCE AND TECHNOLOGY

GRADUATE UNIVERSITY SCIENCE AND TECHNOLOGY

…… ….***…………

Nguyen Vu Ngoc Mai

STUDY ON SYNTHESIS OF MANGANESE OXIDE, IRON OXIDE ON REDUCED GRAPHENE OXIDE NANOPARTICLES TO TREATMENT OF PIGMENTS AND PESTICIDES IN THE AQUEOUS ENVIRONMENT

The thesis was performed at Graduate University of Science and Technology, Vietnam Academy Science and Technology

Supervisor 1: Assoc Prof Dr.Nguyen Quang Trung

Supervisor 2: Assoc Prof Dr Dao Ngoc Nhiem

………… on………, 20……

The thesis can be found in:

- The library of Graduate University of Science and Technology

- National Library of Vietnam

NEW FINDINGS OF THE THESIS

1 Successfully synthesized mixed oxide Fe2O3 – Mn2O3 nanoparticles using tartaric acid (AT), tartaric acid combined with polyvinyl alcohol (PVA) as gel – forming agents Nanostructured Fe2O3-Mn2O3 mixed-oxides prepared by the combustion method that used a mixture of tartaric acid and PVA (pH 4, the molar ratio of Fe/Mn = 1/1, the molar ratio of AT/PVA = 1/1, the molar ratio of (Fe/Mn)/(AT /PVA) = 1/3, the gel-forming temperature of 80 oC and the calcination temperature at 450 oC during 2h) had uniform size and specific surface area of their (63.97 m2/g) was larger than using only tartaric acid as gel – forming agents (46.25 m2/g)

2 Studied the photocatalytic ability of Fe2O3 –Mn2O3 and Fe2O3 –Mn2O3/rGO materials to decompose some pollutants such as methyl orange , methylene blue, parathion, fenitrothion For the first time, mixed oxide Fe2O3 – Mn2O3/rGO nanoparticles were studied to decompose parathion and fenitrothion The results showed that parathion was decomposed efficiency (after 90 minutes reaction time, pH 7.5, the concentration after adsorption equilibrium is 1.5 ppm, the catalyst content of 0.05 g/L, the decomposition efficiency

of parathion is 77.32%) The decomposition efficiency fenitrothion (after 90 minutes reaction time, pH 7.0, concentration after adsorption equilibrium 1.4 ppm, catalyst content of 0.05 g/L) is 88.61% Through modern analytical methods such as High-performance liquid chromatography and Gas chromatography- mass spectrometry, some intermediates formed during the decomposition

of methyl orange, methylene blue, parathion, fenitrothion are proposed

LIST OF WORKS HAS BEEN PUBLISHED

1 Nguyen Vu Ngoc Mai, Dao Ngoc Nhiem, Pham Ngoc

Chuc, Nguyen Quang Trung, Cao Van Hoàng, Synthesis of Fe 2 O 3

-Mn 2 O 3 nanostructured by tartaric acidand preliminary study on methylene orange degradations, Vietnam Journal of Chemistry

(2017), 55 (3e12)

2 Nguyen Vu Ngoc Mai, Nguyen Thi Ha Chi, Nguyen Quang Bac, Doan Trung Dung, Pham Ngoc Chuc, Duong Thi Lim,

Nguyen Quang Trung, Dao Ngoc Nhiem, Synsthesis of nano – mixed

oxides Fe 2 O 3 - Mn 2 O 3 and their applications to photocatalytic degradation of Parathion from water, Proceedings The 3rd

International Workshop on Corrosion and Protection of Materials (2018), Hanoi, Vietnam

3 Nguyen Vu Ngoc Mai, Duong Thi Lim, Nguyen Quang Bac, Nguyen Thi Ha Chi, Doan Trung Dung, Ngo Nghia Pham, Dao

Ngoc Nhiem, Fe 2 O 3 /Mn 2 O 3 nanoparticles: Preparations and applications in the photocatalytic degradation of phenol and parathion in water, Journal of the Chinese chemical society (2019),

DOI : 10.1002/jccs.201900033

4 Nguyen Vu Ngoc Mai, Doan Trung Dung, Duong Thi

Lim, Dao Ngoc Nhiem, Study on synthesis of Mn 3 O 4 nanoparticles and their photocatalytic ability, Vietnam Analytical Sciences Society

(2019), 1, 24

5 Nguyen Vu Ngoc Mai, Nguyen Thi Ha Chi, Duong Thi

Lim, Nguyen Quang Trung, Dao Ngoc Nhiem, Study on

photodegradation of methyl orange, dimethoate and parathion from aqueous solution by nano iron – manganese oxide particles, Vietnam

Journal of Chemistry (2019), 57(4e1,2) 330-334

6 Nguyen Vu Ngoc Mai, Doan Trung Dung, Nguyen Quang Bac, Duong Thi Lim, Nguyen Quang Trung, Dao Ngoc

Nhiem, Synthesis of nano-mixed oxides Fe 2 O 3 -Mn 2 O 3 and their applications in phenol treatment, Vietnam Journal of Chemistry

(2019), 57(4e1,2) 330-334

INTRODUCTION The urgency of the thesis

Currently, environmental pollution is a great challenge to the globe including Vietnam Industrialization and modernization of the economy are raised many persistent pollutants such as pigments, phenol, antibiotics, …becoming more and more

Viet Nam is a long-standing agricultural country To meet the food needs of the increasing number of people, the cultivated area is increasingly shrinking, measures such as agricultural intensification, seed improvement, the use of crop pesticides are implemented to increase productivity Organophosphorus with the advantage of a wide range of prevention and rapid elimination of pests and diseases are now widely applied However, the widespread use of organophosphorus during cultivation has left this chemical residue in the environment very large, especially in the aqueous environment Thus, not only in industrial wastewater but also in agricultural wastewater, durable and persistent organic substances should be treated Currently, many studies focus on completely mineralizing these persistent pollutants into non-toxic substances The advanced oxidation method based on hydroxyl radical activity ●OH (with the highest oxidation potential of 2.8 eV) is of interest to study on The formation of ●OH radicals during reaction occurs through a variety of processes, including photocatalytic processes based on mixed oxide Fe2O3 – MnOx nanoparticles The efficiency of the photocatalytic process increases with the dispersion of these nanoparticles on the carrier (rGO) The object selected for treatment is persistent organic pigments, including MO, MB, and pesticides which are represented

by fenitrothion and parathion The photocatalytic process is applied

to treat these pollutants From the above reasons, the topic “ Study on synthesis of manganese oxide, iron oxide on reduced graphene oxide nanoparticles to treatment of pigments and pesticides in the aqueous environment” is selected to research and deal with these pollutants in Vietnam

The objectives of the thesis

Successfully synthesized nano – mixed oxide by different gelling agents; compared, selected the appropriate gelling agent; researched

to evaluate the catalytic activity of mixed oxide nanoparticles formed with pollutants methyl orange (MO), methylene blue (MB)

Successful dispersed mixed oxide nanoparticles on rGO; investigated catalytic activity of material systems on parathion, fenitrothion

The main contents of the thesis

- Synthesis of metal oxide nanomaterials by a gel - forming agent as tartaric acid and a combination of tartaric acid and PVA, thereby comparing and selecting the appropriate gel - forming agent

- Evaluation of the photocatalytic ability of system Fe2O3 – Mn2O3

in decomposition process MO and MB of the synthesized material system

- Dispersion of mixed oxide nanoparticles Fe2O3 – Mn2O3 on a carrier rGO Survey to evaluate the photocatalytic ability of material system Fe2O3 – Mn2O3/rGO in the process of decomposition parathion and fenitrothion

- Evaluation of the reusability of the catalyst

Chapter 1 OVERVIEW 1.1 General introduction about pesticides

1.1.1 Definitions of pesticides

Pesticides which are substances or mixtures work to:

 prevent, stop, repel, induce, destroy or control crop pests;

 regulate crop or insect growth;

 preserve crops; increase safety and effectiveness when using the pesticides

1.1.2 Classification of pesticides: four main groups

1.1.3 Current situation of pesticide use in Vietnam

How to use pesticides in our country today

 Using pesticides which has been banned

 Increasing using dosage

 Spraying pesticides at anytime

 Using the wrong manual

Organophosphorus are more durable than those in the pyrethroids

group Carbamates have a fairly common use rate in many

agricultural areas Organochlorines are mostly banned from use

1.1.4 Negative effects of organophosphorus pesticides

1.1.4.1 Soil pollution

1.1.4.2 Air pollution

1.1.4.3 Water polution

 In the Northern of Viet Nam [16], fenitrothion (0,06 và 0,04 mg/L), dichlorvos (0,02 and 0,03 mg/L) were detected

In groundwater: dichlorvos was found in 45% of all samples taken, fenitrothion was found in all samples [16]

 In the Mekong Delta, in 2008, Carvalho and etc [17] showed that concentration of diazinon was 3,5 – 42,8 ng/L, that of fenitrothion was 3,3 – 11,9 ng/L found in 5/8 samples

Organophosphorus pesticides residues were detected in soil, air, surface water, and groundwater The commonly used peticides are fenitrothion, diazinon, quinalphos, dichlorvos Comparing with Limited standard EC, residues concentration of pesticides exceeds the allowed level (0.5 µg/L)

1.1.4.4 Impact on human, plants and animals

In addition to the environment pollution by pesticide residues, the pollution by pigments should also be treated These substances are very toxic and dangerous to human health and the ecosystem [19, 20] In the thesis, MO, MB which are the pigments and pesticides which are parathion, fenitrothion are selected to research and treatment with these pollutants in Vietnam

1.2 General introduction about some research pollutants

1.2.1 Physical and chemical properties of some organic pigments

1.3 Methods for treating pigments and organophosphorus in agricultural wastewater

1.3.1 The adsorption method

The main disadvantage of this method is that the adsorbent must be reconstituted, and the hazardous solid waste which is a saturated adsorbent containing the high concentrations of pollutants after treatment must be generated

1.3.2 The biological treatment methods

The drawbacks of the method are research local available microorganism, long decomposition time, low decomposition efficiency

1.3.3 Decomposes by oxidizing agents

Using strong oxidizing agents to oxidize persistent organic

compounds in wastewater are applied

1.3.4 The advanced oxidation process

The advanced oxidation process decomposes organic pigments and pesticides by producing hydroxyl radicals with the highest oxidative potential (2.8 eV) during the reaction

1.4 The photocatalysis decomposes organic pigments and organophosphorus

Figure 1.6 Schematic representation of semiconductor

photocatalytic mechanism

1.4.2 Introduction to Fe2O3 – Mn2O3 materials

Mixed oxide Fe2O3 – Mn2O3 nanoparticles are mainly used for decomposing colored pollutants and high treatment efficiency The

pesticides that belong to the organophosphorus group, namely

parathion and fenitrothion have not been studied for decomposition

by photochemical processes using this catalyst

rGO that has a multilayered structure has many functional groups in its molecule, so it is easy to form bonds with transition metal ions With the above advantages, rGO is suitable for dispersing metal oxide Fe2O3 – Mn2O3 nanoparticles

1.4.3 The situation of researching on the treatment of pigments

and organophosphorus in Vietnam

Studies to treat organic pigments such as MO and MB have been widely conducted in Vietnam Many methods are applied such as adsorption, coagulation and flocculation,biodegradation,…especially advanced oxidation processes, including photocatalytic processes

In Vietnam, research on treating residues of organophosphorus is limited, the main subjects of study are organochlorines such as DDT, Dioxin Studies of decomposition by biological, physical, and chemical methods have also been conducted However, in Vietnam, there have been no specific studies on the decomposition of pesticides, including organophosphorus, particularly parathion and fenitrothion using a photochemical process with a catalyst of mixed oxide Fe2O3 – Mn2O3 nanoparticles

1.5 Methods of synthesizing Fe 2 O 3 - Mn 2 O 3 materials

Chapter 2 EXPERIMENT 2.1 Materials

gel String, heating

gel

Visco

us gel /rGO

Fe2O3 Mn2O3 /rGO

-rGO String, heating

adjust pH string heating, calcinating

Figure 2.2 Diagram of Fe2O3-Mn2O3/rGO synthesis process

using combustion method

2.3 Characterization of materials

2.3.1 Thermal Analysis method (TGA - DTA)

2.3.2 X – ray diffraction method (XRD)

2.3.3 Energy-dispersive X-ray spectroscopy method (EDS)

Transmission Electron Microscope Method (TEM)

2.3.5 Brunauer-Emmet-Teller Method (BET)

charge of materials

2.4 Catalyst activity testing

2.4.1 Decomposion efficiency of MO, MB of photocatalyst mixture material by Fe2O3 – Mn2O3 nanoparticles

The photodegradation efficiency of each sample was calculated by the following expression:

2.4.2 Test of (Fe2O3 – Mn2O3)/rGO on pesticides treatment

Figure 2.3 Equipment of Ace

Photochemical UV Power Supply &

Mercury Vapor Lamps (USA) V: 500 mL

Lamp Watts: 450W, 135 V, Arc – length:11,4 cm, lamp is the use of

a light source to simulate sunlight

H % = C0− Cf

C0 ∗ 100% 2.3

2.4.2.1 Equilibrium adsorption process of pesticides

2.4.2.2 Effect of reaction time on the degradation of pesticides 2.4.2.3 Effect of catalyst dosage on the degradation of pesticides 2.4.2.4 Effect of pH on the degradation of pesticides

2.4.2.5 Effect of inital pesticides concentration

2.5 The methods used to analyze pollutants in the study

2.5.1 The photometric method was determined the content of MO and MB in the sample

intermediates formed during the decomposition of MO and MB 2.5.3.The GC/MS method was determined the concentrations of parathion and fenitrothion in the sample

Chapter 3 RESULTS 3.1 Study on synthesizing nano mixed oxide Fe 2 O 3 - Mn 2 O 3

particles

3.1.1 Study on synthesizing nano mixed oxide Fe2O3 – Mn2O3 particles with tartaric acid as gel – forming agents

3.1.1.1 TGA – DTA analysis of pre - sample with tartaric acid as gel

– forming agents (Figure 3.1)

3.1.1.2 The effect of calcination temperature on the formation of

→ The optimum temperature (500 o

C) was chosen

→ The pH value chosen was pH 4

→ The Fe/Mn mole ratio chosen was Fe/Mn = 1/1

Figure 3.3 X-Ray diffractions at various pH a) pH 1, b) pH 2, c) pH 3, d) pH 4, e) pH 5

Figure 3.4 X-ray diffraction of samples with various mole ratios of Fe/Mn a) 9/1; b) 3/1; c) 2/1; d) 1/1; e) 1/3; f) 1/9

Figure 3.1 TGA and DTA

curves of the as -

prepared gel

Figure 3.2 X-Ray diffractions at

various calcination temperatures a)

300 oC, b) 400 oC, c) 450 oC, d)

500 oC, e) 550 oC, f) 600 oC