Tóm tắt luận Án tiến sĩ tiếng anh nghiên cứu khả năng cố Định một số kim loại nặng trong Đất bằng vật liệu zeolite lưỡng cực

UNIVERSITY OF AGRICULTURE AND FORESTRYNGUYEN THI BICH HANH RESEARCH ON THE ABILITY TO FIX SOME HEAVY METALS IN SOILS BY BIPOLAR ZEOLITE MATERIALS Major: Environmental Science Code: 9.44.

UNIVERSITY OF AGRICULTURE AND FORESTRY

NGUYEN THI BICH HANH

RESEARCH ON THE ABILITY TO FIX SOME HEAVY METALS IN SOILS BY BIPOLAR ZEOLITE MATERIALS

Major: Environmental Science

Code: 9.44.03.01

SUMMARY DOCTORAL DISSERTATION

IN ENVIRONMENTAL SCIENCE

THAI NGUYEN – 2024

UNIVERSITY OF AGRICULTURE AND FORESTRY -

THAI NGUYEN UNIVERSITY

Scientific Supervisors: 1 Prof Dr Dang Van Minh

2 Assoc Prof Dr Van Huu Tap

Reviewer 1:

Reviewer 2:

Reviewer 3:

The dissertation was defended in front

of the institutional dissertation evaluation Committee

Meeting at: Thai Nguyen University of Agriculture and Forestry, Thai

Nguyen University

On , day month year 202

Dissertation can be found at:

- National Library

- Thai Nguyen Learning Resource Center

- Library of University of Agriculture and Forestry - Thai Nguyen University

TO THE DISSERTATION

1 Nguyen T B H., Van H T., Dang V.M., Tran T N H., Nguyen

T T., and Hoang T K (2024) Insight into chromium adsorption

from contaminated soil using Mg/Al LDH-zeolite Heliyon.

https://doi.org/10.1016/j.heliyon.2024 e31084

2 Nguyen T B H., Van H T., Dang V M, Nguyen T H., and Hoang

T K (2024) Immobilization of Pb, Cd, and Cr in contaminated soilaround mining areas using Mg/Al LDH-zeolite and evaluation of maize

growth Environmental Research Communications, 6(10), 105001.

3 Nguyen T B H., and Van H T (2024) Application of modifiedzeolite in the remediation of heavy metal in contaminated soil: a

short review Technology in Agronomy, 4(1), pp 2-7.

4 Nguyen Thi Bich Hanh, Van Huu Tap, Dang Van Minh, Ta MinhPhuong The influence of some environmental factors on the ability

to simultaneously immobilize Pb, Cd and Cr in contaminated soilusing Mg/Al LDH-zeolite Journal of Hydrometeorology, No.763,07-2024, pp 01-12

5 Nguyen Thi Bich Hanh, Van Huu Tap, Dang Van Minh Theinfluence of pH on the ability to simultaneously adsorb Pb, Cd and

Cr in contaminated soil using zeolite, Journal of Science andTechnology, Thai Nguyen University, No 299 (10) pp 51-60

1 Reason for choosing the topic

Along with the development of modern socio-economy, thequality of human life is increasingly improved, however, environmentalpollution problems are increasing and attracting the attention of peopleand authorities Heavy metal (HM) pollution in soil is currently one ofthe notable environmental problems that can affect environmentalquality , ecosystems and human health due to the ability of HM toaccumulate in food (B Hu et al., 2017) Therefore, the treatment of

HM pollution in the soil environment is very meaningful and meets theneed for people to use safe agricultural products

Currently, many methods have been applied to treat heavy metalpollution in soil, including physical, chemical, physicochemical andbiological methods (Xu et al., 2022) In which, adsorption is one of themethods used by many scientists in the world and in Vietnam toremediate and restore soil contaminated with heavy metal However,new studies have only treated heavy metal in soil in the form of cations

or anions Research on the simultaneous treatment of cations and anions

of heavy metal in soil using bipolar zeolite adsorbent materials is stilllimited, although similar bipolar materials have been studied to adsorbheavy metal anions and cations in water and wastewater environments.Zeolite is an aluminosilicate mineral and is quite common innature (Jha et al., 2016) The structure of zeolite is formed from SiO 4

tetrahedral units connected together Zeolite has been studiedextensively in the treatment of heavy metal ions in water and soil Forpositive ions, zeolite is very effective, however, for anions, theadsorption capacity of this material is limited

LDH (layered double hydroxides) materials are two-dimensionalnanostructured materials In which, the positive charge generated by thereplacement of 2 + cationswith 3 + cationswill be compensated by anionsbetween the layers These anions can be replaced by other anions,making LDH capable of adsorbing anionic heavy metals such asarsenite, arsenate, chromate, etc., so LDH is used in environmentaltreatment research ( Shi et al., 2021)

After mining and processing, zeolite can be used immediately ormodified mainly to treat cationic heavy metals such as Cd 2+ and Pb 2+ in the

water environment LDH materials have also been studied to treat anionicheavy metals of As and Cr in soil and water environments It can be seenthat zeolite, LDH or LDH-zeolite combinations have been studied by manyauthors to treat pollutants in the water environment However, the researchdirection of using bipolar Mg/Al LDH-zeolite (MALZ) materials to treatsome heavy metals in soil ( CrO 4 2- , Pb 2+ , Cd 2+ ) is still limited Theresearch on using bipolar zeolite materials to treat cationic and anionicheavy metals in soil is a new direction, with the ability to be applied inpractice However, studies evaluating the adsorption capacity of thismaterial for HM cations and anions in soil are still limited in Vietnam aswell as in the world.

Therefore, the study of the treatment of some cations and anions

of heavy metals in contaminated soils by bipolar zeolite adsorbentmaterials will enrich the research methods and enhance the efficiency oftreating heavy metals in soils, which will bring about efficiency in basic

research and practical applications Therefore, the topic : " Research on the ability to fix some heavy metals in soils by bipolar zeolite materials"

is a new research direction and has high practical significance

2 Objectives of the topic

* General objectives:

Evaluation of the adsorption and immobilization capacity ofheavy metals (CrO4 2- , Pb2+, Cd2+) of bipolar zeolite adsorbent (MALZ)and its application study in the treatment of contaminated soil nearmining areas

Cd2+) of MALZ material

- Evaluation of the growth, development and absorption of heavymetals of plants (corn) in soil near the mining area contaminated withheavy metals (the thesis used 2 contaminated soil samples: soil sample

near the lead-zinc mine waste dump (Lang Hich, Dong Hy, Thai Nguyen)and soil sample near the tin factory area (Ha Thuong, Dai Tu, ThaiNguyen)) after being treated with MALZ material.

3 Scientific and practical significance

- Scientific basis for application: research results provide a solidtheoretical basis for using MALZ to fix cations and anions (CrO4 2- ,

Pb2+, Cd2+) in contaminated soil environment

- The study clarified the ability to accumulate cations and anions(CrO42-, Pb2+, Cd2+) in corn grown on 02 acres of land near a HM-contaminated mineral mining area after treatment with bipolar zeolitematerial, contributing to improved understanding of interactionsbetween plants and pollutants

b Practical significance

Based on the scientific and practical basis of using bipolar zeolite

in research, the thesis has:

- Application in pollution treatment: The thesis has demonstratedthe effectiveness of bipolar zeolite in adsorbing heavy metal ions inpolluted soil, contributing to providing practical solutions for pollutiontreatment in mineral exploitation areas

- Evaluation of the effect on plant growth: The study evaluatedthe impact of MALZ supplementation on the growth and development

of corn plants in contaminated soil conditions, thereby determining theability to reduce heavy metal accumulation in plants

4 New points of the thesis

- Adsorption capacity and optimal conditions: The thesis

evaluated the heavy metal adsorption capacity of bipolar zeolite

material (MALZ) and determined some optimal environmentalconditions (pH, humidity, incubation time, material to soil ratio) toimprove adsorption efficiency, suitable for practice in Vietnam.

- Practical application in pollution treatment: The thesis

applied MALZ to treat polluted soil near mineral exploitation areas Theresults showed that the treated soil met the standards for corncultivation, with heavy metal content in crops meeting the QCVN 8-2:2011/BYT standards on heavy metal pollution limits in food

Chapter 1 DOCUMENT OVERVIEW

1.1 Studies on heavy metal pollution in soil

1.1.1 Causes and consequences of heavy metal pollution in soil

1.1.2 Chemical characteristics, forms of existence and transformation

of Pb, Cd and Cr in soil

1.1.3 Factors affecting the existence of Pb, Cd and Cr in soil

- Soil pH

- Organic matter in soil

- Clay minerals and soil texture

- Presence of competing ions

1.1 4 Absorption , accumulation and effects of Pb, Cd and Cr on plants 1.1.5 Current status of heavy metal pollution in soil

- Characteristics of heavy metal pollution in soil

+ Wide distribution

+ Strong potential

+ Irreversibility and reversibility

+ Multi-metal pollution

- Current status of heavy metal contaminated soil in the world

1.1.6 Methods of treating soil contaminated with heavy metals

1.2 Studies on zeolite mineral materials, LDH and modified zeolite

1.2.1 Zeolite mineral materials

1.2.2 Layer double hydroxides (LDH) mineral materials

1.2.3 Bipolar materials and bipolar zeolites

1.2.3.1 Bipolar materials

1.2.3.2 Bipolar zeolite material: Mg/Al LDH-zeolite

1.2.4 Modified zeolite materials and applications in treating heavy metal pollution in soil

1.2.4.1 Some zeolite modification techniques

1.2.4.2 Some typical studies on modified zeolite

1.2.4.3 Achievements and limitations of existing studies on modified zeolites

1.2.4.4 Heavy metal adsorption mechanism of modified zeolite

1.3 Factors affecting the heavy metal adsorption process of zeolite

Chapter 2 RESEARCH CONTENT AND METHODS

2.1 Research object and scope

* Research object

- Test materials: Commercial zeolite and MALZ, also known asbipolar zeolite, were manufactured at the laboratory of the Faculty ofNatural Resources and Environment, College of Science, Thai NguyenUniversity

- Soil with very low Pb, Cd and Cr content is artificially polluted

- Soil near the mineral exploitation area contaminated with HM:The thesis used 02 soil samples taken in the area near 02 mineralexploitation mines: Lang Hich lead-zinc mine in Tan Long commune,Dong Hy district, Thai Nguyen province and tin mine in Ha Thuongcommune, Dai Tu district, Thai Nguyen province

- Experimental corn variety: hybrid corn variety CP 111 of CPSeeds company

- Some environmental factors and adsorbent materials affect theability to adsorb heavy metals in soil (pH, incubation time, soil moistureduring incubation, mass percentage of composting materials)

* Scientific scope: The study focuses on the ability of adsorbents

(zeolite, MALZ) to adsorb heavy metals in soil (soil environmentartificially polluted with heavy metal cations and anions: Pb2+, Cd2+,CrO42-) of adsorbent materials (zeolite, MALZ), post-mining soil and

the ability of corn plants to absorb heavy metals in naturally andartificially polluted soil samples through laboratory-scale studies.

* Research space scope

- Laboratory research scope: all of the above studies were conducted

at the Experimental Area, College of Science, Thai Nguyen University

- Research period: 2020 - 2024

2.2 Research content

- Content 1: Overview of documents and evaluation of basiccharacteristics of MALZ bipolar adsorbent material: phase composition,morphology, structure, elemental composition, surface area of adsorbentmaterial

- Content 2: Study on the adsorption capacity and some factorsaffecting the adsorption of heavy metals of bipolar zeolite material(MALZ)

+ Content 2.1: Study the effect of the mass ratio of compostedmaterial with soil on the adsorption efficiency of heavy metals

+ Content 2.2: Study the effect of pH on the adsorption efficiency

2.3 Research method

2.3.1 Method of material preparation and evaluation of material adsorption characteristics

2.3.2 Research method on factors affecting the ability of research materials to adsorb heavy metals in soil

2.3.2.1 Preparation of chemicals and experimental soil

2.3.2.2 Experimental design to study some factors affecting the HM adsorption capacity of MALZ material

Table 2.1 Experimental formulas of some factors affecting

Experimental formula for the effect of humidity

Experimental formula influence

at 70%,incubationtime 30days,optimal pH

of eachexperimentalgroupaccording topHexperiment

Adsorbent added, humiditymaintained at70%, incubationtime 30 days,optimal pH ofeachexperimentalgroup according

to pHexperiment

Adsorbent added ,humidity maintained at70%, incubation time

15, 30 and 45 days ,optimal pH of eachexperimental groupaccording to pHexperiment

at 70%,incubationtime 30days,optimal pH

of eachexperimentalgroupaccording to

Humidity 30 %,add 1.5 g zeolite

or MALZ ,incubation time

30 days, optimal

pH of eachexperimentalgroup according

to pHexperiment

Incubate for 15 days,add 1.5 g zeolite orMALZ , humiditymaintained at 70%,optimal pH of eachexperimental groupaccording to pHexperiment

Experimental formula for the effect of humidity

Experimental formula influence

of incubation time

pHexperiment

at 70%,incubationtime 30days,optimal pH

of eachexperimentalgroupaccording topHexperiment

Humidity 50 %,add 1.5 g zeolite

or MALZ ,incubation time

30 days, optimal

pH of eachexperimentalgroup according

to pHexperiment

incubate for 30 days,add 1.5 g zeolite orMALZ , humiditymaintained at 70%,optimal pH of eachexperimental groupaccording to pHexperiment

at 70%,incubationtime 30days,optimal pH

of eachexperimentalgroupaccording topHexperiment

Humidity 70 %,add 1.5 g zeolite

or MALZ ,incubation time

30 days, optimal

pH of eachexperimentalgroup according

to pHexperiment

Incubate for 45 days,add 1.5 g zeolite orMALZ , humiditymaintained at 70%,optimal pH of eachexperimental groupaccording to pHexperiment

Experimental formula for the effect of humidity

Experimental formula influence

2.4 Methods of analyzing soil and crop indicators

2.5 Method of synthesizing results and processing statistical data

Chapter 3 RESEARCH RESULTS AND DISCUSSION

3.1 Characteristics of bipolar zeolite material (MALZ)

3.1 1 FT-IR spectrum of materials

MALZ exhibits the appearance of new peaks: The peak at 553 cm

-1 present only in MALZ represents the Al-O group, which is a sign ofthe combination of zeolite and Mg/Al double hydroxide layer in thiscomposite material Characteristic peaks for CO functional groups: Thepeak at 1369 cm -1 present only in MALZ, related to the carbonate group

in the double hydroxide structure, is also a clear difference from thenormal zeolite The change in intensity and position of some peaks,such as at 3460 cm -1 representing the hydroxyl group, indicates theinteraction between the components during the formation of MALZ

3.1 2 X-ray diffraction (XRD) analysis of materials

MALZ materials with CuKα radiation of (ƛ = 1.540Å), scanning rate

of 0.02 deg/s and 2 theta angle in the range of 5-55 o are as follows:XRD data of zeolite samples e There are characteristic peaks formordenite at 2θ angles in the range of 6.51 ; 9.72 ; 13.87; 19.68 ;22.27 ; 25.58 ; 26.32; 27.71 ; 31.93 and 35.57° and for MALZ at 2θangles in the range of 11.55 ; 23.28 ; 34.22 ; 39.43 and 46.82 °

3.1 3 EDX data of the material

The elemental composition of the material was analyzed by energydispersive X-ray spectroscopy (EDX) Some elements present in MALZbut not in zeolite such as Mg, Na and the ratio of elements present inthese two materials The elements appearing in the zeolite compositioninclude C (16.86%), O (53.59%), Al (4.68%), Si (21.42%), K (0.83%),

Ca (1.33%) and Fe (1.24%) Meanwhile, besides the presence ofelements in the zeolite composition, the Al ratio in MALZ increased to6.22% and new elements appeared such as Mg (10.09%) and Na(1.10%) EDX analysis data also showed that most of the elements ofMALZ exist in the form of CaCO3, SiO2, Al2 O3 and other forms Theanalysis results showed that the bipolar MALZ material wassuccessfully synthesized

3.1 4 SEM image of the material

- 4800 electron microscope showed a homogeneous and porous particlestructure In addition, the results also demonstrated that the material had aporous structure The SEM image showed that the morphology of zeolite had arod-like structure while MALZ had a heterogeneous structure MALZ had amore heterogeneous structure than zeolite due to the presence of Mg and Alduring the synthesis process This demonstrated that MALZ material wassuccessfully synthesized

3.1 5 Surface area

Table 3 1 Surface area of Zeolite and MALZ

Cumulative adsorption surface

area

Pore size 38,3594 12,3100

3.1.6 Physical and chemical properties of materials

Table 3 2 Physicochemical properties of Zeolite and MALZ

3.2 Adsorption capacity and factors affecting heavy metal adsorption

of bipolar zeolite material (MALZ)

3.2.1 Composition and properties of the studied soil

Table 3.3 Physical and chemical properties of initial soil (clean soil

sample taken

at University of Agriculture and Forestry, Thai Nguyen University)

The effect of pH (from 5 - 9) on the ability to fix CrO 4 2- , Pb 2+ , Cd2+

The exchange capacity (F1) in soil by zeolite and MALZ adsorbentmaterials is presented in Table 3.4

Table 3.4 Average contents of exchangeable CrO 4 2- , Pb 2+ , Cd 2+ F1

at different pH levels (mg/kg) Experiment HP anion CrO 4

14,880 ± 0.393e

11.322 ± 0.458b

Experiment HP anion CrO 4

12.670 ± 0.351c

pH 9 zeolite

13.537 ± 0.175e

0.955 ± 0.029e

13.525 ± 0.061d

HP equals MALZ

MALZ

14.553 ± 0.191f

1.497 ± 0.017f

14,880 ± 0.393f

pH 5 MALZ 1.793 ± 0.023a 0.603 ±

0.013c

10.558 ± 0.103c

pH 6 MALZ

2.691 ± 0.170b

0.422 ± 0.012b

8.218 ± 0.318b

pH 7 MALZ

8.721 ± 0.109c

0.252 ± 0.019a 6.002 ± 0.111a

pH 8 MALZ 9.496 ±

0.153d

0.728 ± 0.021d

11.758 ± 0.154d

pH 9 MALZ

11.678 ± 0.102e