The commonly methods are used to treat wastewater containing TNT including: physical method adsorption by activated carbon, electrolysis; chemical method Fenton, UV - Fenton, internal el
Trang 1MINISTRY OF EDUCATION
AND TRAINING
VIETNAM ACADEMY OF SCIENCE AND TECHNOLOGY
GRADUATE UNIVERSITY OF SCIENCE AND TECHNOLOGY
VU DUY NHAN
STUDY ON INTERNAL ELECTROLYSIS COMBINE WITH
AAO-MBBR TO TREAT TNT WASTEWATER
Speciality: Chemical Engineering
Code: 9 52 03 01
PhD DISSERTATION SUMMARY ON CHEMICAL
ENGINEERING
Ha Noi - 2020
Trang 2The work was completed at:
Vietnam Academy of Science and Technology
Science instructor:
1 Assoc Prof Le Thi Mai Huong
2 Prof Le Mai Huong
The dissertation can be found at:
1, National Library of Viet Nam
2, Library of Institute of Natural Products Chemistry - Vietnam Academy of Science and Technology
Trang 3I INTRODUCTION 1.1 Background
2,4,6 trinitrotoluene (TNT) is a chemical widely used in defense and economy The explosive manufacturing industry discharges a large amount of wastewater containing toxic chemicals such as TNT
In fact, about 50 years after World War II, in places where gunpowder factories were built, large amounts of TNT and their isomers were found in soil and water environments [1, 2, 21] This proves that TNT
is capable of long-term survival in nature or in other words, TNT is difficult to biodegrade In our country, besides the factories is producing ammunition, explosives, and launchers in the defense industry, there are still a large amount of wastewater containing TNT which needs to be treated in warehouses for repairing and collecting ammunition
The commonly methods are used to treat wastewater containing TNT including: physical method (adsorption by activated carbon, electrolysis); chemical method (Fenton, UV - Fenton, internal electrolysis), biological method (aerobic activated sludge, MBBR, UASB, MBR, plants, enzymes, white rot fungi) These measures may
be used independent or combination with each other, depending on the nature of the wastewater and the material facilities and economic conditions of the manufacture establishment
This dissertation focuses on establishing the process of manufacturing bimetallic Fe / Cu internal electrolysis nanomaterial, thereby studying some characteristics correlation between corrosive line and TNT decomposition kinetics and time Setting and optimizing the internal electrolysis process by bimetal Fe / Cu nanomaterials combined with biological method A2O-MBBR (moving bed Biological reactor) to treat TNT wastewater at laboratory scale and Pilot scale at the scene At the same time, the first step establishing the control automatic or semi-automatic operation software with the conditions of the treatment process are determined
Trang 41.2 Research objectives
Bimetal Fe / Cu internal electrolytic nanomaterials
Internal electrolysis method and biological method A2O - MBBR to treat wastewater containing TNT
1.3 New contributions
1.3.1 Successfully fabricated bimetallic Fe / Cu electrolytic internal materials with average size of 100 nm, potential (voltage) E0 = 0.777 V In electrolyte solution pH=3 with TNT concentration of 100 mg/L, corrosive current is reaching 14.85*10-6 A/cm2 and corrosion speed reach 8 87*10-2 mm / year Therefore has increased the reaction rate, processing efficiency is higher, faster Concurrently, It has been determined corrosion current and its relationship with LnCt / C0 depend
on the duration of the TNT reduction process by the corrosion current measurement method There has not been any announcement using this method Some related publication determined the relationship between TNT reduction speed and reduction speed of H+ to H2
1.3.2 Establishing TNT treatment technology by combining the internal electrolysis method using bimetal Fe/Cu nanomaterials with biological method A2O-MBBR Nowadays, no announcement has been made which combined these two methods to treat wastewater The microorganisms in the A2O-MBBR system used to treat wastewater containing TNT has been identified, among them two
strains can be new: Novosphingobium sp (HK1-II, HK1-III) have bootstrap value of 97.4-97.92% to Novosphingobium sediminicola sp and Trichosporon (HK2-II, TK2-II and HK2-III) have bootstrap value
of 97.7% to middelhonenii sp These two species were published on
the international gene bank with the code GenBank: LC483151.1; LC483155.1 and the corresponding link are:
https://www.ncbi.nlm.nih.gov/nuccore/LC483151;
https://www.ncbi.nlm.nih.gov/nuccore/Lc483155
Trang 51.4 The layout of dissertation
The dissertation consists of 191 pages with 24 tables, 101 pictures, 139 references and 2 appendices The layout of dissertation: Introduction (3 pages), Chapter 1: Literature review (44 pages), Chapter 2: Materials and methods (15 pages), Chapter 3: Results and discussion (79 pages) ), Conclusion (2 pages), Published works (1 page), References (15 pages), Appendix (17 pages)
INTRODUCTION
The introduction refers to the scientific and practical significance of the dissertation
CHAPTER 1: LITERATURE REVIEW
Overview of international and domestic studies on issues such as: The studies on treatment methods wastewater containing TNT
The studies on the internal electrolysis method to treat wastewater Studies on Fe / Cu bimetallic materials fabrication method for wastewater treatment
Studies on combines biological method of A2O-MBBR to wastewater treatment
The studies on software controls the wastewater treatment system
CHAPTER 2: MATERIALS AND METHODS
Analytical methods to determine the structure, size, composition
of Fe / Cu bimetal nano: SEM, ERD, EDX
Methods of measuring corrosive lines: potential range 0.0V, scanning speed 10 mV/s, Electrodes compare Ag/AgCl
Trang 6-1.00V-(saturation) The corrosion line and the corrosion potential were measured using Autolab PG30 (Netherlands)
TNT analytical methods: HPLC, Von – Amper
Methods of determining Fe content
Proceed to determine Fe ion content according to EPA 7000B method on Contraa 700 device
Method of determining COD, T-N, T-P, NH4 +: According to TCVN or ISO
Experimental method
1 Fabrication of Nano Fe / Cu materials: by CuSO4 plating method
on powder Fe average size of 100 nm on magnetic stirrer
2 Treatment of TNT wastewater: Prepare a 100 mg/L TNT solution into a 500 ml erlenmeyer flask, change the conditions reaction as pH, temperature, shaking speed, Fe/Cu content to each corresponding research
3 Experimental planning method: Follow the quadratic planning Behnken and Design-Expert optimization software version 11
Box-4 Isolation of activated sludge: To activate, take activated sludge from wastewater containing TNT treatment stations of production facilities 121, 115 Then, activated sludge in anaerobic, anoxic and oxic activated condition of 30 days Then proceed to isolate microorganism system in the sludge is activated
5 Microbiological classification method: Conduct DNA sequencing
of selected strains, then compare with the DNA sequence of 16S are published species by the DDBJ, EMBL, GenBank
CHAPTER 3: RESULTS AND DISCUSSIONS
The chapter’s content includes: establishing conditions for manufacturing bimetal Fe/Cu nanomaterials, the effects of internal electrolytic factors, A2O-MBBR to treat wastewater containing TNT and optimize treatment conditions, Kinetic characteristics of internal electrolytic reaction, the diversity of microorganisms in the A2O-MBBR system, the software control the internal electrolytic system combined with A2O-MBBR to treat wastewater containing TNT
Trang 73.1 Fabrication of internal electrolytic materials Nano bimetal Fe/Cu
This section write details the results of the research to establish the reaction conditions for creating Fe / Cu materials: Fe powder of
100 nm size is plated by CuSO4 solution at a concentration of 6% in 2 minutes Fe/Cu materials have Cu concentration on the surface of 68.44% and copper atomic mass reaches 79.58%
Figure 3.2: Tafel line of galvanic corrosion of Fe/C electrode
system (a) and Fe/Cu after plating (b) at different time values
From Figure 3.2, it can be seen that the corrosion potential (EĂM) of
Fe materials has the descending rule towards the negative side However, the potential of Fe/Cu electrolytic internal materials reaches
- 0.563 V÷-0.765 V with absolute value higher than the corrosion potential of Fe/C, only from - 0.263 V÷- 0.6693V
Trang 8Figure 3.3 shows that the corrosion speed of Fe / Cu material is 8,187.10-2 mm/year, which is nearly 2 times higher than that of Fe / C material, only 4,811.10-2 mm/year
4.0E-6 6.0E-6 8.0E-6 1.0E-5 1.2E-5 1.4E-5 1.6E-5
Figure 3.3: The dependent on time of corrosion line of electrode
material system: Fe/C before plating -- (a) and Fe/Cu after chemical plating -■- (b)
Thus, bimetallic Fe/Cu electrolytic internal material has been
synthesized with average size of 100 nm, potential voltage E0 =
0.777 V In electrolyte solution which have pH=3, concentration of TNT 100 mg/L, Fe/Cu materials have corrosion current density
14.85*10-6 A/cm2 and corrosion speed 8,187*10-2 mm/year
3.2 Effect of factors on the efficiency of TNT treatment
20 40 60 80 100
Thời gian (phút)
2 2.5 3 3.5 4 4.5 5 5.5 6
Trang 9Figures 3.4 and 3.5 show that during the first 90 minutes, the reaction speed was very fast, achieving high processing efficiency At 90 minutes, the TNT concentration reached 1.61; 1.62; 1.71 and 1.72 mg/L and treatment efficiency in turn 98.29; 98.22; 98.34 and 98.22% correspond to the initial pH values of 2.0; 2.5; 3.0; 3.5 For pH 4.0; 4,5; achieved a lower efficiency and the corresponding TNT concentration was 3.05; 13.09 mg/L Values pH 5.0; 5.5 and 6 have the lowest treatment efficiency, with TNT concentrations respectively are 26.03; 56.36 and 89.03 mg/L From 90th to 180th minute, the processing efficiency slows down and does not change significantly
3.2.2 Effect of Fe/Cu material content
Conducting survey on the influence of different Fe/Cu material content inTNT treatment efficiency The experiments have been conducted with 10; 20; 30; 40; 50; 60 g/L of Fe/Cu The result is shown in Figure 3.11; 3.12 and 3.13
Trang 103.2.3 Effect of temperature
Temperature has an effect on the rate of internal electrolysis reaction, the higher the temperature, the faster the reaction speed and conversely
0 4 8
Figure 3.8: Dependence of
TNT treatment efficiency on
temperature at first 90 minutes
Figure 3.9: The change in TNT
concentration is treated by internal electrolyte material according to reaction time at different temperatures Figures 3.8 and 3.9 show that the higher the temperature and the faster the reaction speed and conversely At the time of 90 minutes, the temperatures at 40℃ and 45℃ treated TNT were most effective, the concentration of TNT decreased to 0.57; 0.63 mg / L; next at 30℃, 35℃ is 1.76; 1.71 mg / L and finally at 20℃, 25℃ to 5.31; 3.60 mg /
L Thus, it is clear that the higher the temperature and the faster the reaction speed, the highest processing efficiency is at 45℃ and the lowest is 20℃ The next phase, from 90 to 120 minutes, the reaction speed slows down
3.2.4 Effect of TNT concentration
The initial concentration of TNT affects the reaction speed and the processing efficiency due to the following reasons: (1) contaminants and intermediate decomposition products will compete with each other on the surface of electrodes (2) Different concentrations of contaminants make the dispersion phase in contact between pollutants with Fe / Cu electrode surface different:
Trang 110 10 20 30 40 50 60 70 80 90 100 110
30 40 50 60 70 80 90 100 0
20 40
Figure 3.10: Dependence of
TNT concentration remaining
after treatment on the initial
concentration
Figure 3.11: The change of TNT
concentration after treatment over time with different initial TNT concentrations
Figure 3.10; 3.11 shows that the lower the concentration of TNT, the higher the processing efficiency and conversely After 90 minutes, the remaining TNT concentration was 1.35; 1.42; 1.51; 1.68 mg/L corresponds to the initial TNT concentrations of 40; 60; 80; 100 mg /
L In the next phase, from 90 to 180 minutes, the effect of the initial TNT concentration on the processing speed and efficiency is almost
no difference At 180 minutes, the remaining TNT concentration was corresponding to 0.15; 0.19; 0.21 and 0.23 mg/L
3.2.5 Optimize the process of treating TNT wastewater
Applying Box-Behnken method for pH, temperature, shaking speed, reaction time for regression equations:
Y = 93.16 + 1.05B + 3.02C + 8.62D - 0.265BC - 4.73CD + 1.12A2 - 1.11C2 - 3D2 Optimal conditions are determined from the regression equation corresponding to: pH = 3.24, temperature at 32.6 ℃, shaking speed of 91 rpm for 140 minutes and get TNT treatment efficiency of 98.29% Among the factors that affect TNT's processing performance, the time is greatest affect, follow is the temperature, but to a lesser, the shaking speed and pH have little effect
Trang 12c d
Figure 3.12: Relationship between factors on efficiency of TNT
treatment (a): pH and time; (b) pH and temperature; (c) pH and shaking speed; (d) temperature and time; (e) temperature and shaking speed; (f) shaking speed and time
3.3 Some kinetic characteristics of the internal electrolysis process TNT
3.3.1 Iron corrosion rate and TNT decomposition kinetics
This section presents the results of the iron corrosion rate and the correlation between the rate of TNT decomposition
0.2 0.4 0.6 0.8 1.0
dissolved Fe content on reaction
time of internal electrolysis process
Figure 3.14: Dependence of
TNT concentration on the internal electrolytic reaction time of Fe / Cu materials
Trang 13Figure 3.13 and Figure 3.14 show the causal relationship between the rate of iron corrosion and the iron concentration in TNT treatment process depend on time
Figure 3.15: Relationship between logarithms of concentration and time
Figure 3.15 proves that TNT is reduced by Fe / Cu internal electrolysis reaction fit Level 1 Kinetic assumptions model The reaction rate constant is calculated by the slope (angular coefficient)
of the linear regression line
3.3.2 Effect of pH and Fe/Cu content
-4.0 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5
Figure 3.16: Effect of initial pH
on the rate of TNT decomposition
Figure 3.17: Effect of Fe / Cu content
on the rate of TNT decomposition
3.3.3 Effect of shaking speed and temperature
Figure 3.18: Effect of shaking speed
on the rate of TNT decomposition
Figure 3.19: Effect of temperature
on the rate of TNT decomposition