RISK ASSESSMENT AND SYNTHESIS OF MAGNETIC BIOCHAR COMPOSITES...

RISK ASSESSMENT AND SYNTHESIS OF

MAGNETIC BIOCHAR COMPOSITES FROM

PAPER MILL SLUDGE FOR REMOVAL OF

PENTACHLOROPHENOL

PARMILA DEVI

DEPARTMENT OF CHEMICAL ENGINEERING

INDIAN INSTITUTE OF TECHNOLOGY DELHI

OCTOBER 2015

RISK ASSESSMENT AND SYNTHESIS OF

MAGNETIC BIOCHAR COMPOSITES FROM

PAPER MILL SLUDGE FOR REMOVALOF

PENTACHLOROPHENOL

by

PARMILA DEVI

DEPARTMENT OF CHEMICAL ENGINEERING

Submitted

in fulfillment of the requirements of the degree of

DOCTOR OF PHILOSOPHY

to the

INDIAN INSTITUTE OF TECHNOLOGY DELHI

OCTOBER 2015

I

CERTIFICATE

This is to certify that the thesis entitled, “Risk assessment and synthesis of magnetic biochar

composites from paper mill sludge for removal of pentachlorophenol” being submitted by

Ms. Parmila Devi to the Indian Institute of Technology Delhi for the award of Doctor of

Philosophy is a record of bonafide research work carried out by her under my guidance and

supervision in conformity with the rules and regulations of Indian Institute of Technology Delhi.

The research report and results presented in this thesis have not been submitted, in part or full, to

any other university or institute for the award of any degree or diploma.

Date: Dr. Anil K. Saroha

Place: New Delhi Professor

Department of Chemical Engineering

Indian Institute of Technology Delhi

New Delhi-110016

II

ACKNOWLEDGEMENTS

Words are often too less to reveal one’s deep regards. This thesis has been kept on track and

came to completion with the support and encouragement of numerous people including my

supervisor, SRC members, my friends, colleagues and my family. I take this opportunity to

express my profound sense of gratitude and respect to all those who helped me through the

duration of this Ph.D. thesis.

First, I would like to thank the Supreme Power, the GOD, since born to till now for each

moment give his support, being with me and always guided me to work on the right path of

life. Without his grace, this would not have been possible.

At this moment of accomplishment, I am extremely grateful to my guide, Prof. Anil K.

Saroha, for providing necessary infrastructure and resources to accomplish my research work.

This work would not have been possible without his guidance, support and encouragement.

Under his guidance I successfully overcame many difficulties and learned a lot.

I am extremely grateful to my SRC members, Prof. T.R. Sreekrishnan (Department of

Biochemical Engineering and Biotechnology), Prof. Ratan Mohan (Department of Chemical

Engineering) and Prof. K.K. Pant (Department of Chemical Engineering) for their critical

evaluations, suggestions and encouragement during the whole course of the work.

I sincerely appreciate the help rendered by the staff of the Department of Chemical

Engineering, Indian Institute of Technology Delhi. I express my sincere thanks to staff of

Central Facility and Nanoscale Research Facility, Indian Institute of Technology Delhi for

providing all the administrative help and facilities for the performance of the thesis work. I

am grateful to Prof. G.P Agarwal and his research group for co-operation and providing

facilities for the analysis of the samples.

III

I am extremely grateful to Prof. S. Basu, Head, Department of Chemical Engineering and

Prof. A.N. Bhaskarwar, former Head, Department of Chemical Engineering for extending all

necessary help.

I take this opportunity to sincerely acknowledge the University Grant Commission (UGC),

Government of India, New Delhi, for providing financial assistance in the form of Junior and

Senior Research Fellowship which buttressed me to perform my work comfortably. I wish to

acknowledge the funding received for the project from Council of Scientific & Industrial

Research (CSIR), New Delhi, India.

I specially thank my colleagues and seniors, Dr. Dal Singh Kharat, Dr. Shyamal Roy,

Dr. Vinita Khandegar, Mr. Bharadwaj Adiraju, Ms. Sushma, Ms. Manjari Kumari, Mr.

Santosh Gughe, Ms. Firdaus Praveen, Mr. Tanmoy Patra, Mr. Hari and Dr. Prabhakar

Mohanty, Dr. Sachchit Majhi, for their immense cooperation at times of need.

I express my heartfelt gratitude to my friends Ms. Jyoti Rani, Ms. Amita Chaudhary, Mr.

Amandeep Jindal, Ms. Niharika and Ms. Akansha for their kind co-operation and support

during the course work and thesis work.

Last but not least, I would like to pay high regards to my parents, my husband and my family

for their sincere encouragement and inspiration throughout my research work and lifting me

uphill this phase of life. I owe everything to them.

I truly believe that all persons who have directly or indirectly contributed to this study whom

I have not mentioned personally are aware of my deep appreciation.

(Parmila Devi)

IV

ABSTRACT

Huge quantity of sludge is generated during the paper manufacturing process in the pulp and

paper industry. The disposal and management of the generated sludge is a big challenge as it

contains significant amount of heavy metals, organic toxins and pathogenic microorganisms.

Accumulation and bio-availability of heavy metals in the sludge is a limiting factor for its

disposal and utilization. Pyrolysis is a promising sludge treatment method for the heavy

metals immobilization leading to a significant reduction in the bioavailability and leaching

potential of the heavy metals in the biochar. Therefore, efforts have been made in the present

study to immobilize the heavy metals present in the sludge using pyrolysis. The risk analysis

was performed to study the bioavailability and eco-toxicity of heavy metals in biochar

obtained from pyrolysis of pulp and paper mill effluent treatment plant sludge. The sludge

was pyrolyzed at different temperatures (200 – 700oC) and the resultant biochar were

analyzed for fractionation of heavy metals by sequential extraction procedure. It was

observed that all the heavy metals get enriched in biochar matrix after pyrolysis, but the

bioavailability and eco-toxicity of the heavy metals in biochar were significantly reduced as

the mobile and bioavailable heavy metal fractions were transformed into the relatively stable

fractions. Moreover, it was observed that the leaching potential of heavy metals decreased

after pyrolysis and the best results were obtained for biochar pyrolyzed at 700oC. Further, the

sorption behaviour of the biochar was determined on the basis of degree of carbonization and

bulk and surface properties of the biochar. It was found that the sorption behaviour varied

from linear to non-linear depending on fractions of uncarbonized and carbonized organic

matters in the biochar. The carbonized fraction acts as an adsorption media whereas

uncarbonized fraction acts as a partition media. The individual fractions of adsorption and

partition were quantified by isotherm separation method and isotherm parameters were

correlated with biochar properties. It was found that H/C, O/C and (N+O)/C atomic ratios

V

were negatively correlated with adsorption capacity, while surface area, total pore volume

and pore diameter were positively correlated to the biochar adsorption capacity.

The biochar pyrolyzed at 700 oC (BC700) showed best results in the terms of adsorption

performance and environmental friendliness. However, the tedious separation process of the

exhausted powdered biochar from the effluent and the regeneration/disposal problem of the

exhausted biochar limit its commercial applications. Therefore, zero-valent iron (ZVI) was

incorporated in the biochar matrix to modify the biochar to magnetic biochar composite

which facilitate the separation of the exhausted biochar from the effluent. ZVI has powerful

magnetic and reducing properties, which makes it most suitable magnetic reducing media for

mixing with the biochar to obtain the modified magnetic biochar composites. The zero-valent

iron magnetic biochar composites (ZVI-MBC) were synthesized from the paper mill sludge

biochar and used for the treatment of the synthetic and real effluent containing

pentachlorophenol (PCP). During the synthesis of ZVI-MBC, NaBH4 was used as the

reducing agent to reduce Fe (II) to Fe (0) and cetyltrimethylammonium bromide was added as

surfactant. The effect of the molar ratio of FeSO4 to NaBH4, dose of the surfactant and the

ZVI to biochar ratio on the PCP removal efficiency was investigated. It was found that the

ZVI-MBC combines the advantages of biochar and ZVI particles for the simultaneous

adsorption and dechlorination of PCP in the effluent and the complete removal of PCP was

obtained in 240 min. The ageing tests showed that biochar prevents the formation of oxide

film on the ZVI particles and leaching tests confirmed the stability of ZVI on biochar matrix

as very low iron leaching was noticed. Although, ZVI-MBC was efficient in dechlorination

of PCP from the aqueous solution but the dechlorination reaction was too slow to achieve the

desired dechlorination in practical period of time. One of the practical approaches for

enhancing the dechlorination rate of the ZVI-MBC is the impregnation of ZVI-MBC with a

catalyst (Ni). Therefore, the Ni-ZVI magnetic biochar composites (Ni-ZVI-MBC) were

VI

synthesized by doping of Ni on ZVI-MBC surface. The synthesized Ni-ZVI-MBC were

characterized and analyzed for the stability of Ni and ZVI particles in biochar matrix. It was

found that the removal of PCP with Ni-ZVI-MBC involves simultaneous adsorption and

dechlorination mechanism resulting in higher PCP removal efficiency. The presence of Ni as

a catalyst in Ni-ZVI-MBC enhances the dechlorination rate and prevents the accumulation of

PCP in the biochar matrix. The effect of operating parameters (solution pH, Ni loading, initial

PCP concentration in the solution and temperature) on adsorption and dechlorination

efficiency was studied. The dechlorination efficiency of Ni-ZVI-MBC was found to increase

with an increase in Ni loading and the optimum Ni loading was found to be 0.5 wt %. The

adsorption and dechlorination kinetics of PCP removal were studied and it was found that

adsorption is the rate limiting step in PCP removal by Ni-ZVI-MBC.

The disposal of the exhausted adsorbent becomes a problem as it contains concentrated

amount of the pollutants. So, the feasibility of usage of exhausted adsorbents for brick

formation was evaluated. The bricks were prepared using geopolymerization technique using

NaOH as polymerization agent. The geopolymer bricks showed good compressive strength

and met ASTM standards. The concentration of heavy metals in the leachate was found

within the permissible limits prescribed by Indian Standards for Industrial and Sewage

Effluents Discharge (inland surface water) suggesting that the use of the geopolymer brick

will not cause any harm to the environment.

VII

Table of Contents Certificate ................................................................................................................................... I

Acknowledgements .................................................................................................................... II

Abstract .................................................................................................................................... IV

Table of contents .................................................................................................................... VII

List of Figures ........................................................................................................................ XII

List of Tables ......................................................................................................................... XIV

Abbreviations ........................................................................................................................ XVI

Nomenclature .......................................................................................................................XVII

CHAPTER 1: INTRODUCTION .............................................................................................. 1

1.1. Background .................................................................................................................... 1

1.2. Paper industry ................................................................................................................. 2

1.3. Manufacturing processes in pulp and paper industry ...................................................... 4

1.4. Emissions from paper making process ............................................................................ 6

1.5. Disposal of sludge ........................................................................................................... 9

1.6. Statement of problem and objectives ............................................................................ 10

1.7. Organization of thesis .................................................................................................... 12

CHAPTER 2: LITERATURE REVIEW ................................................................................. 16

2.1. Preparation of sludge based adsorbent .......................................................................... 16

2.2. Activation of the sludge based adsorbent ...................................................................... 18

2.2.1. Physical activation ............................................................................................. 18

2.2.2. Chemical activation ........................................................................................... 20

2.2.3. Activation using additives .................................................................................. 30

2.3. Characterization of the adsorbent ................................................................................. 32

2.3.1. Surface area and porosity of adsorbents ............................................................ 44

2.3.2. Ash content ........................................................................................................ 46

2.3.3. Acidity and basicity ........................................................................................... 48

2.4. Factors affecting adsorption ......................................................................................... 51

2.4.1. Effect of solution pH .......................................................................................... 51

VIII

2.4.2. Effect of contact time ......................................................................................... 51

2.4.3. Effect of adsorbent dose ..................................................................................... 52

2.4.4. Effect of initial pollutant concentration ............................................................ 52

2.4.5. Effect of temperature ......................................................................................... 53

2.4.6. Effect of agitation speed .................................................................................... 54

2.5. Adsorption models ....................................................................................................... 54

2.5.1. Adsorption isotherm models .............................................................................. 54

2.5.2. Adsorption kinetics models................................................................................ 60

2.5.3. Adsorption thermodynamics models ................................................................. 63

2.6. Application of sludge based adsorbents ........................................................................ 65

2.6.1. Adsorption of heavy metals ............................................................................... 65

2.6.2. Adsorption of dyes ............................................................................................. 75

2.6.3. Adsorption of phenols ........................................................................................ 85

2.6.4. Adsorption of phosphorus and phosphates ........................................................ 89

2.6.5. Adsorption of miscellaneous compounds .......................................................... 93

2.7. Desorption/regeneration of sludge based adsorbents .................................................. 100

2.8. Leaching potential of sludge based adsorbent ............................................................. 103

2.9. Cost estimation ............................................................................................................ 106

2.10. Stabilization and usage of exhausted adsorbent ........................................................ 108

2.11. Gaps in literature ....................................................................................................... 109

CHAPTER 3: RISK ASSESSMENT FOR BIOAVAILABILITY AND ECOTOXICITY OF

HEAVY METALS IN BIOCHAR ........................................................................................ 110

3.1. Background ................................................................................................................. 110

3.2. Materials and methods ................................................................................................ 112

3.2.1. Preparation of raw material .................................................................................. 112

3.2.2. Pyrolysis of paper mill sludge .............................................................................. 113

3.2.3. Acid digestion ....................................................................................................... 113

3.2.4. Sequential extraction ............................................................................................ 114

3.2.5. Leaching tests ....................................................................................................... 115

3.2.6. Effect of pH on heavy metals leaching ................................................................. 115

3.3. Results and discussion ................................................................................................. 116

3.3.1. Effect of pyrolysis temperature on heavy metal partitioning ............................... 116

3.3.2. Fractionation and bioavailability of heavy metals ................................................ 118

IX

3.3.3. Leaching studies ................................................................................................... 122

3.3.4. Effect of solution pH on heavy metals leaching ................................................... 124

3.3.5. Ecological risk assessment ................................................................................... 125

CHAPTER 4: EFFECT OF PYROLYSIS TEMPERATURE ON PAHs TOXICITY AND

SORPTION BEHAVIOUR OF BIOCHAR .......................................................................... 128

4.1. Background ................................................................................................................. 128


4.2.1. Characterization of biochars ................................................................................. 130

4.2.2. Adsorption studies ................................................................................................ 131

4.2.3. Data analysis ......................................................................................................... 132

4.2.4. PAHs extraction.................................................................................................... 132

4.2.5. GC-MS analysis.................................................................................................... 133


4.3.1. Thermal degradation of paper mill sludge ............................................................ 133

4.3.2. Effect of pyrolysis temperature on biochar properties ......................................... 135

4.3.3. Effect of pyrolysis temperature on adsorption behaviour .................................... 141

4.3.4. PAHs concentration in biochars ........................................................................... 152

CHAPTER 5: SYNTHESIS AND CHARACTERIZATION OF ZVI-MBC FOR

PENTACHLOROPHENOL REMOVAL .............................................................................. 158

5.1. Background ................................................................................................................. 158


5.2.1. Chemicals ............................................................................................................. 160

5.2.2. Preparation of ZVI-MBC ..................................................................................... 160

5.2.3. Characterization of ZVI-MBC ............................................................................. 161

5.2.4. Adsorption experiments........................................................................................ 161

5.2.5. Extraction studies ................................................................................................. 163


5.3.1. Optimization of ZVI-MBC synthesis parameters ................................................. 163

5.3.2. Characterization of ZVI-MBC ............................................................................. 167

5.3.3. PCP removal using ZVI-MBC as an adsorbent .................................................... 170

5.3.4. Treatment of real industrial effluent ..................................................................... 172

5.3.5. Ageing of ZVI-MBC ............................................................................................ 173

X

CHAPTER 6: SIMULTANEOUS ADSORPTION AND DECHLORINATION OF

PENTACHLOROPHENOL BY Ni-ZVI-MBC ..................................................................... 175

6.1. Background ................................................................................................................. 175


6.2.1. Chemicals ............................................................................................................. 176

6.2.2. Preparation of Ni-ZVI-MBC ................................................................................ 176

6.2.3. Characterization of Ni-ZVI-MBC ........................................................................ 178

6.2.4. Adsorption experiments........................................................................................ 178

6.2.5. Analysis ................................................................................................................ 179

6.2.6. Adsorption and dechlorination kinetics ................................................................ 179

6.2.7. Extraction studies ................................................................................................. 180


6.3.1. Characterization of Ni-ZVI-MBC ........................................................................ 180

6.3.2. Comparison of PCP sorption by different adsorbents .......................................... 184

6.3.3. Effect of operating parameters on removal efficiency of PCP ............................. 186

6.3.4. Adsorption and dechlorination kinetics ................................................................ 189

6.3.5. Thermodynamics studies ...................................................................................... 192

6.3.6. Treatment of real industrial effluent ..................................................................... 194

6.3.7. Leaching studies ................................................................................................... 195

6.3.8. Ageing of Ni-ZVI-MBC ....................................................................................... 195

CHAPTER 7: FEASIBILITY OF BRICK FORMATION FROM EXHAUSTED BIOCHAR

................................................................................................................................................ 198

7.1. Background ................................................................................................................. 198


7.2.1. Chemicals ............................................................................................................. 200

7.2.2. Preparation of biochar-based geopolymer bricks ................................................. 200

7.2.3. Characterization of biochar-based geopolymer bricks ......................................... 200

7.2.4. Water absorption test ............................................................................................ 201

7.2.5. Leaching tests ....................................................................................................... 201


7.3.1. Characteristics of fresh biochar ............................................................................ 202

7.3.2. Optimization of preparation parameters ............................................................... 203

7.3.3. Characterization of biochar-based geopolymer bricks ......................................... 207

XI

7.3.4. Water absorption and abrasion index ................................................................... 210

7.3.5. Leaching potential of biochar-based geopolymer bricks ...................................... 211

7.3.6. Brick preparation using exhausted ZVI-MBC and Ni-ZVI-MBC ....................... 212

CHAPTER 8: CONCLUSIONS ............................................................................................ 214

CHAPTER 9: SCOPE FOR FUTURE WORK ..................................................................... 218

REFERENCES ...................................................................................................................... 219

APPENDIX ............................................................................................................................ 251

BIODATA.............................................................................................................................. 253

XII

List of Figures

1.1 Typical manufacturing process in pulp and paper mill ........................................................ 6

1.2 Scheme of sludge generation in pulp and paper mill ........................................................... 8

3.1 Experimental set up for pyrolysis of paper mill sludge ................................................... 113

3.2 Sequential extraction procedure of the heavy metals in PMS and biochar ...................... 114

3.3 Partitioning of the heavy metals in biochar pyrolyzed at different temperatures ............ 117

3.4 Fractionation and bioavailability of the heavy metals in PMS and biochar (a) Cr; (b) Cu;

(c) Ni; (d) Zn; (e) Pb; (f) Cd ................................................................................................. 120

3.5 Leaching potential of the heavy metals .......................................................................... 123

3.6 Effect of pH on leachability of heavy metals from PMS and biochar ............................ 124

4.1 Thermal degradation profile of paper mill sludge ........................................................... 134

4.2 Effect of pyrolysis temperature on aromaticity and polarity index of the biochars ......... 137

4.3 Van Krevelen diagram of biochars pyrolyzed at different temperatures ......................... 138

4.4 FTIR spectra of biochar pyrolyzed at different temperatures ......................................... 140

4.5 Isotherm plot of PCP adsorption for different biochars ................................................... 142

4.6 Isotherm separation and DMM model fit for biochars (a) BC500; (b) BC400; (c) BC300

and (d) BC200 ........................................................................................................................ 145

4.7 Linear correlation of biochar properties with sorption parameter (qm, adsorption) (a) H/C; (b)

O/C; (c) (N+O)/C; (d) surface area; (e) total pore volume and (f) ash content ..................... 150

4.8a Correlation of partition coefficient with aromaticity index of the biochars ................... 151

4.8b Correlation of partition coefficient with polarity index of the biochars ........................ 151

4.9 TPAHs and TEQ profile of biochars pyrolyzed at different temperatures ...................... 152

4.10 Effect of pyrolysis temperature on concentrations distribution of different PAHs ....... 153

4.11 Distribution profile of PAHs on the basis of number of rings ....................................... 154

5.1 Effect of FeSO4: NaBH4 molar ratio on PCP removal by ZVI-MBC ............................. 164

5.2 Effect of CTMB dosage on PCP removal by ZVI-MBC ................................................ 165

5.3 Effect of ZVI: biochar ratio on PCP removal by ZVI-MBC .......................................... 167

XIII

5.4 Characterization of the ZVI-MBC (a) SEM image (b) X-ray diffraction (XRD) pattern of

ZVI-MBC and (c) Fourier transform infra red (FTIR) plot of ZVI-MBC ............................. 170

5.5 Adsorption and dechlorination plot of the PCP by ZVI, biochar and ZVI-MBC ............ 171

5.6 Effect of different ageing environment on the PCP removal efficiency of ZVI-MBC .. 174

6.1. X-ray diffraction plot of Ni-ZVI biochar composites at different Ni loadings ............... 181

6.2 Scanning electron micrograph (a) paper mill sludge; (b) fresh Ni-ZVI-MBC and (c)

exhausted Ni-ZVI-MBC ........................................................................................................ 182

6.3 FTIR spectra of fresh and exhausted Ni-ZVI-MBC ........................................................ 184

6.4 PCP removal efficiency using different adsorbents ......................................................... 185

6.5 Effect of solution pH on PCP removal efficiency using Ni-ZVI-MBC ........................... 187

6.6 Effect of Ni loading on PCP removal efficiency and dechlorination efficiency ............. 189

6.7 First order kinetics of PCP removal by Ni-ZVI-MBC at different initial PCP

concentrations ........................................................................................................................ 190

6.8 First order kinetics of PCP removal by Ni-ZVI-MBC at different Ni-ZVI-MBC dosage

................................................................................................................................................ 191

6.9 Effect of temperature on PCP removal efficiency ........................................................... 193

6.10 Effect of ageing on efficiency of Ni-ZVI-MBC (a) PCP removal efficiency (b) PCP

dechlorination efficiency ...................................................................................................... 196

7.1 Effect of NaOH dosage and curing temperature on compressive strength of the biochar-

based geopolymer bricks ....................................................................................................... 204

7.2 Effect of initial water content on compressive strength of the biochar-based geopolymer

bricks ...................................................................................................................................... 205

7.3 Effect of calcium carbonate content on compressive strength of the biochar-based

geopolymer bricks ................................................................................................................. 206

7.4 XRD plot of the biochar-based geopolymer bricks ........................................................ 207

7.5 FTIR spectra of biochar-based geopolymer bricks ......................................................... 208

7.6 SEM image of biochar-based geopolymer bricks ........................................................... 209

7.7 The heavy metal leaching potential of biochar-based geopolymer bricks prepared using

different CaCO3 content ........................................................................................................ 212

XIV

List of Tables

1.1 Typical characteristics of pulp and paper mill effluent ....................................................... 7

2.1 Effect of pyrolysis and activation conditions on the properties of sludge based adsorbents

.................................................................................................................................................. 33

2.2 Mathematical adsorption isotherm models ........................................................................ 55

2.3 Adsorption kinetics models................................................................................................ 61

2.4 Removal of heavy metals by sludge based adsorbents ..................................................... 66

2.5 Removal of dyes by sludge based adsorbents .................................................................... 76

2.6 Removal of phenols by sludge based adsorbents ............................................................... 86

2.7 Removal of phosphorus and phosphate by sludge based adsorbents ................................. 90

2.8 Removal of miscellaneous compounds by sludge based adsorbents ................................. 94

3.1 Characterization of paper mill sludge .............................................................................. 112

3.2 Enrichment of heavy metals in biochar pyrolyzed at different temperatures .................. 118

3.3 Percentage recovery of heavy metals calculated by comparison of analytical procedures

................................................................................................................................................ 119

3.4 Concentration of different heavy metals (mg/L) in leachate (TCLP) .............................. 123

3.5 Indices for the ecological risk assessment ...................................................................... 126

3.6 Ecological risk assessment of the heavy metals in sludge and biochar .......................... 127

4.1 Proximate and elemental analysis of paper mill sludge and biochars ............................. 135

4.2 Surface area, porosity and pH of paper mill sludge and biochars ................................... 139

4.3 Estimated values of sorption isotherm parameters .......................................................... 147

4.4 Concentration of PAHs in biochars pyrolyzed at different temperatures ........................ 156

5.1 Surface area and porosity of paper mill sludge, biochar and ZVI-MBC ......................... 168

5.2 Characterization of pulp and paper mill effluent ............................................................ 173

6.1 Surface area and porosity of paper mill sludge biochar and ZVI-MBC and Ni-ZVI-MBC

................................................................................................................................................ 181

XV

6.2 PCP absorption and dechlorination kinetics constants for Ni-ZVI-MBC ....................... 192

6.3 Estimated values of thermodynamics parameters for PCP removal by Ni-ZVI-MBC .... 194

7.1 Characterization of paper mill sludge biochar ................................................................. 202

7.2 Water adsorption and abrasion index of biochar-based geopolymer bricks prepared using

different NaOH dosages ......................................................................................................... 211

7.3 Mechanical and leaching characteristics of biochar-based geopolymer brick ................. 213

XVI

ABBREVIATIONS

BOD – Biochemical oxygen demand (mg/L)

COD – Chemical oxygen demand (mg/L)

EDX – Electron dispersive X-ray spectroscopy

FTIR – Fourier infrared transform spectroscopy

GC-MS – Gas chromatography mass spectroscopy

HPLC – High pressure liquid chromatography

SEM – Scanning electron microscopy

TDS – Total dissolved solids (mg/L)

TOC – Total organic carbon (mg/L)

TSS – Total suspended solids (mg/L)

XRD – X-ray diffraction spectroscopy

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NOMENCLATURE

ETP – Effluent treatment plant

HMW – High molecular weight

LMW – Low molecular weight

MMW – Medium molecular weight

Ni-ZVI-MBC – Nickel zero-valent iron magnetic biochar composites

PAHs – Polycyclic aromatic hydrocarbons

PCP – Pentachlorophenol

PMS – Paper mill sludge

ZVI – Zerovalent iron

ZVI-MBC – Zero-valent iron magnetic biochar composites

RISK ASSESSMENT AND SYNTHESIS OF MAGNETIC BIOCHAR COMPOSITES...

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