John Wiley & Sons Applied Water Science Cover Water is one of the most precious and basic needs of life for all living beings, and a precious nati.. Product #: 978-1-119-72476-6 Regular price: $195.33 $195.33 Auf Lager

Applied Water Science

Fundamentals and Applications, Volume 1

Inamuddin / Ahamed, Mohd Imran / Boddula, Rajender / Rangreez, Tauseef Ahmad (Herausgeber)

Cover

1. Auflage Juli 2021
560 Seiten, Hardcover
Wiley & Sons Ltd

ISBN: 978-1-119-72476-6
John Wiley & Sons

Jetzt kaufen

Preis: 209,00 €

Preis inkl. MwSt, zzgl. Versand

Weitere Versionen

epubmobipdf

Water is one of the most precious and basic needs of life for all living beings, and a precious national asset. Without it, the existence of life cannot be imagined. Availability of pure water is decreasing day by day, and water scarcity has become a major problem that is faced by our society for the past few years. Hence, it is essential to find and disseminate the key solutions for water quality and scarcity issues. The inaccessibility and poor water quality continue to pose a major threat to human health worldwide. Around billions of people lacking to access drinkable water. The water contains the pathogenic impurities; which are responsible for water-borne diseases. The concept of water quality mainly depends on the chemical, physical, biological, and radiological measurement standards to evaluate the water quality and determine the concentration of all components, then compare the results of this concentration with the purpose for which this water is used. Therefore, awareness and a firm grounding in water science are the primary needs of readers, professionals, and researchers working in this research area.

This book explores the basic concepts and applications of water science. It provides an in-depth look at water pollutants' classification, water recycling, qualitative and quantitative analysis, and efficient wastewater treatment methodologies. It also provides occurrence, human health risk assessment, strategies for removal of radionuclides and pharmaceuticals in aquatic systems. The book chapters are written by leading researchers throughout the world. This book is an invaluable guide to students, professors, scientists and R&D industrial specialists working in the field of environmental science, geoscience, water science, physics and chemistry.

Preface xix

1 Sorbent-Based Microextraction Techniques for the Analysis of Phthalic Acid Esters in Water Samples 1
Miguel Ángel González-Curbelo, Javier González-Sálamo, Diana A. Varela-Martínez and Javier Hernández-Borges

1.1 Introduction 2

1.2 Solid-Phase Microextraction 6

1.3 Stir Bar Sorptive Extraction 25

1.4 Solid-Phase Extraction 26

1.5 Others Minor Sorbent-Based Microextraction Techniques 48

1.6 Conclusions 52

Acknowledgements 53

References 53

2 Occurrence, Human Health Risks, and Removal of Pharmaceuticals in Aqueous Systems: Current Knowledge and Future Perspectives 63
Willis Gwenzi, Artwell Kanda, Concilia Danha, Norah Muisa-Zikali and Nhamo Chaukura

2.1 Introduction 64

2.2 Occurrence and Behavior of Pharmaceutics in Aquatic Systems 65

2.2.1 Nature and Sources 65

2.2.2 Dissemination and Occurrence in Aquatic Systems 67

2.2.3 Behaviour in Aquatic Systems 71

2.3 Human Health Risks and Their Mitigation 73

2.3.1 Human Exposure Pathways 73

2.3.2 Potential Human Health Risks 74

2.3.3 Human Health Risks: A Developing World Perspective 81

2.3.4 Removal of Pharmaceuticals 82

2.3.4.1 Conventional Removal Methods 83

2.3.4.2 Advanced Removal Methods 85

2.3.4.3 Hybrid Removal Processes 88

2.4 Knowledge Gaps and Future Research Directions 88

2.4.1 Increasing Africa's Research Footprint 88

2.4.2 Hotspot Sources and Reservoirs 89

2.4.3 Behavior and Fate in Aquatic Systems 89

2.4.4 Ecotoxicology of Pharmaceuticals and Metabolites 89

2.4.5 Human Exposure Pathways 89

2.4.6 Human Toxicology and Epidemiology 90

2.4.7 Removal Capacity of Low-Cost Water Treatment Processes 90

2.5 Summary, Conclusions, and Outlook 90

Author Contributions 91

References 91

3 Oil-Water Separations 103
Pallavi Jain, Sapna Raghav and Dinesh Kumar

3.1 Introduction 103

3.2 Sources and Composition 106

3.3 Common Oil-Water Separation Techniques 106

3.4 Oil-Water Separation Technologies 107

3.4.1 Advancement in the Technology of Membrane 111

3.4.1.1 Polymer-Based Membranes 111

3.4.1.2 Ceramic-Based Membranes 111

3.5 Separation of Oil/Water Utilizing Meshes 113

3.5.1 Mechanism Involved 113

3.5.2 Meshes Functionalization 114

3.5.2.1 Inorganic Materials 115

3.5.2.2 Organic Materials 115

3.6 Separation of Oil-Water Mixture Using Bioinspired Surfaces 116

3.6.1 Nature's Lesson 116

3.6.2 Superhydrophilic/Phobic and Superoleophilic/Phobic Porous Surfaces 117

3.7 Conclusion 118

Acknowledgment 118

References 119

4 Microplastics Pollution 125
Agnieszka Dbrowska

4.1 Introduction and General Considerations 125

4.2 Key Scientific Issues Concerning Water and Microplastics Pollution 126

4.3 Marine Microplastics: From the Anthropogenic Litter to the Plastisphere 131

4.4 Social and Human Perspectives: From Sustainable Development to Civil Science 133

4.5 Conclusions and Future Projections 134

References 134

5 Chloramines Formation, Toxicity, and Monitoring Methods in Aqueous Environments 139
Rania El-Shaheny and Mahmoud El-Maghrabey

5.1 Introduction 140

5.2 Inorganic Chloramines Formation and Toxicity 140

5.3 Analytical Methods for Inorganic Chloramines 143

5.3.1 Colorimetric and Batch Methods 144

5.3.2 Chromatographic Methods 148

5.3.3 Membrane Inlet Mass Spectrometry 150

5.4 Organic Chloramines Formation and Toxicity 151

5.5 Analytical Methods for Organic Chloramines 154

5.6 Conclusions 156

References 156

6 Clay-Based Adsorbents for the Analysis of Dye Pollutants 163
Mohammad Shahadat, Momina, Yasmin, Sunil Kumar, Suzylawati Ismail, S. Wazed Ali and Shaikh Ziauddin Ahammad

6.1 Introduction 164

6.1.1 Biological Method 165

6.1.2 Physical Method 165

6.1.3 Why Only Clays? 165

6.1.4 Clay-Based Adsorbents 166

6.1.4.1 Kaolinite 166

6.1.4.2 Rectorite 168

6.1.4.3 Halloysite 169

6.1.4.4 Montmorillonite 170

6.1.4.5 Sepiolite 170

6.1.4.6 Laponite 171

6.1.4.7 Bentonite 171

6.1.4.8 Zeolites 172

6.2 Membrane Filtration 180

6.3 Chemical Treatment 181

6.3.1 Fenton and Photo-Fenton Process 182

6.3.2 Mechanism Using Acid and Base Catalyst 182

6.4 Photo-Catalytic Oxidation 186

6.5 Conclusions 188

Acknowledgments 188

References 188

7 Biochar-Supported Materials for Wastewater Treatment 199
Hanane Chakhtouna, Mohamed El Mehdi Mekhzoum, Nadia Zari, Hanane Benzeid, Abou el kacem Qaiss and Rachid Bouhfid

7.1 Introduction 200

7.2 Generalities of Biochar: Structure, Production, and Properties 201

7.2.1 Biochar Structure 201

7.2.2 Biochar Production 203

7.2.2.1 Pyrolysis 204

7.2.2.2 Gasification 204

7.2.2.3 Hydrothermal Carbonization 205

7.2.3 Biochar Properties 205

7.2.3.1 Porosity 205

7.2.3.2 Surface Area 207

7.2.3.3 Surface Functional Groups 207

7.2.3.4 Cation Exchange Capacity 210

7.2.3.5 Aromaticity 210

7.3 Biochar-Supported Materials 212

7.3.1 Magnetic Biochar Composites 212

7.3.2 Nano-Metal Oxide/Hydroxide-Biochar Composites 214

7.3.3 Functional Nanoparticles-Coated Biochar Composites 216

7.4 Conclusion 220

References 222

8 Biological Swine Wastewater Treatment 227
Aline Meireles dos Santos, Alberto Meireles dos Santos, Patricia Arrojo da Silva, Leila Queiroz Zepka and Eduardo Jacob-Lopes

8.1 Introduction 227

8.2 Swine Wastewater Characteristics 228

8.3 Microorganisms of Biological Swine Wastewater Treatment 231

8.4 Classification of Biological Swine Wastewater Treatment 235

8.5 Biological Processes For Swine Wastewater Treatment 236

8.5.1 Suspended Growth Processes 237

8.5.1.1 Activated Sludge Process 237

8.5.1.2 Sequential Batch Reactor 237

8.5.1.3 Sequencing Batch Membrane Bioreactor 238

8.5.1.4 Anaerobic Contact Process 238

8.5.1.5 Anaerobic Digestion 238

8.5.2 Attached Growth Processes 239

8.5.2.1 Rotating Biological Contactor 239

8.5.2.2 Upflow Anaerobic Sludge Blanket 240

8.5.2.3 Anaerobic Filter 240

8.5.2.4 Hybrid Anaerobic Reactor 241

8.6 Challenges and Future Prospects in Swine Wastewater Treatment 241

References 242

9 Determination of Heavy Metal Ions From Water 255
Ritu Payal and Tapasya Tomer

9.1 Introduction 255

9.2 Detection of Heavy Metal Ions 256

9.2.1 Atomic Absorption Spectroscopy 257

9.2.2 Nanomaterials 257

9.2.3 High-Resolution Surface Plasmon Resonance Spectroscopy with Anodic Stripping Voltammetry 258

9.2.4 Biosensors 259

9.2.4.1 Enzyme-Based Biosensors 260

9.2.4.2 Electrochemical Sensors 261

9.2.4.3 Polymer-Based Biosensors 261

9.2.4.4 Bacterial-Based Sensors 262

9.2.4.5 Protein-Based Sensors 262

9.2.5 Attenuated Total Reflectance 262

9.2.6 High-Resolution Differential Surface Plasmon Resonance Sensor 262

9.2.7 Hydrogels 263

9.2.8 Chelating Agents 264

9.2.9 Ionic Liquids 265

9.2.10 Polymers 266

9.2.10.1 Dendrimers 266

9.2.11 Macrocylic Compounds 266

9.2.12 Inductively Coupled Plasma Mass Spectrometry 267

9.3 Conclusions 267

References 268

10 The Production and Role of Hydrogen-Rich Water in Medical Applications 273
N. Jafta, S. Magagula, K. Lebelo, D. Nkokha and M.J. Mochane

10.1 Introduction 273

10.2 Functional Water 275

10.3 Reduced Water 275

10.4 Production of Hydrogen-Rich Water 277

10.5 Mechanism Hydrogen Molecules During Reactive Oxygen Species Scavenging 279

10.6 Hydrogen-Rich Water Effects on the Human Body 280

10.6.1 Anti-Inflammatory Effects 280

10.6.2 Anti-Radiation Effects 281

10.6.3 Wound Healing Effects 282

10.6.4 Anti-Diabetic Effects 284

10.6.5 Anti-Neurodegenerative Effects 285

10.6.6 Anti-Cancer Effects 285

10.6.7 Anti-Arteriosclerosis Effects 285

10.7 Other Effects of Hydrogenated Water 285

10.7.1 Effect of Hydrogen-Rich Water in Hemodialysis 285

10.7.2 Effect on Anti-Cancer Drug Side Effects 286

10.8 Applications of Hydrogen-Rich Water 286

10.8.1 In Health Care 286

10.8.2 In Sports Science 288

10.8.3 In Therapeutic Applications and Delayed Progression of Diseases 289

10.9 Safety of Using Hydrogen-Rich Water 290

10.10 Concluding Remarks 291

References 292

11 Hydrosulphide Treatment 299
Marzie Fatehi and Ali Mohebbi

11.1 Introduction 300

11.1.1 Agriculture 302

11.1.2 Medical 307

11.1.3 Industrial 315

11.2 Conclusions 325

References 326

12 Radionuclides: Availability, Effect, and Removal Techniques 331
Tejaswini Sahoo, Rashmirekha Tripathy, Jagannath Panda, Madhuri Hembram, Saraswati Soren, C.K. Rath, Sunil Kumar Sahoo and Rojalin Sahu

12.1 Introduction 332

12.1.1 Available Radionuclides in the Environment 333

12.1.1.1 Uranium 333

12.1.1.2 Thorium (Z = 90) 334

12.1.1.3 Radium (Z = 88) 335

12.1.1.4 Radon (Z = 86) 336

12.1.1.5 Polonium and Lead 336

12.1.2 Presence of Radionuclide in Drinking Water 337

12.1.2.1 Health Impacts of Radionuclides 338

12.1.2.2 Health Issues Caused Due to Uranium 338

12.1.2.3 Health Issues Caused Due to Radium 339

12.1.2.4 Health Issues Caused Due to Radon 339

12.1.2.5 Health Issues Caused Due to Lead and Polonium 339

12.2 Existing Techniques and Materials Involved in Removal of Radionuclide 340

12.2.1 Ion Exchange 340

12.2.2 Reverse Osmosis 340

12.2.3 Aeration 341

12.2.4 Granulated Activated Carbon 341

12.2.5 Filtration 342

12.2.6 Lime Softening, Coagulation, and Co-Precipitation 342

12.2.7 Flocculation 343

12.2.8 Nanofilteration 343

12.2.9 Greensand Filteration 344

12.2.10 Nanomaterials 344

12.2.10.1 Radionuclides Sequestration by MOFs 344

12.2.10.2 Radionuclides Removal by COFs 345

12.2.10.3 Elimination of Radionuclides by GOs 346

12.2.10.4 Radionuclide Sequestration by CNTs 346

12.2.11 Ionic Liquids 347

12.3 Summary of Various Nanomaterial and Efficiency of Water Treating Technology 348

12.4 Management of Radioactive Waste 348

12.5 Conclusion 350

References 350

13 Applications of Membrane Contactors for Water Treatment 361
Ashish Kapoor, Elangovan Poonguzhali, Nanditha Dayanandan and Sivaraman Prabhakar

13.1 Introduction 362

13.2 Characteristics of Membrane Contactors 362

13.3 Membrane Module Configurations 365

13.4 Mathematical Aspects of Membrane Contactors 366

13.5 Advantages and Limitations of Membrane Contactors 367

13.5.1 Advantages 367

13.5.1.1 High Interfacial Contact 368

13.5.1.2 Absence of Flooding and Loading 368

13.5.1.3 Minimization of Back Mixing and Emulsification 368

13.5.1.4 Freedom for Solvent Selection 368

13.5.1.5 Reduction in Solvent Inventory 368

13.5.1.6 Modularity 369

13.5.2 Limitations 369

13.6 Membrane Contactors as Alternatives to Conventional Unit Operations 370

13.6.1 Liquid-Liquid Extraction 370

13.6.2 Membrane Distillation 370

13.6.3 Osmotic Distillation 372

13.6.4 Membrane Crystallization 372

13.6.5 Membrane Emulsification 372

13.6.6 Supported Liquid Membranes 373

13.6.7 Membrane Bioreactors 373

13.7 Applications 374

13.7.1 Wastewater Treatment 374

13.7.2 Metal Recovery From Aqueous Streams 375

13.7.3 Desalination 375

13.7.4 Concentration of Products in Food and Biotechnological Industries 375

13.7.5 Gaseous Stream Treatment 376

13.7.6 Energy Sector 376

13.8 Conclusions and Future Prospects 377

References 378

14 Removal of Sulfates From Wastewater 383
Ankita Dhillon, Rekha Sharma and Dinesh Kumar

14.1 Introduction 383

14.2 Effect of Sulfate Contamination on Human Health 384

14.3 Groundwater Distribution of Sulfate 384

14.4 Traditional Methods for Sulfate Removal 385

14.4.1 Treatment With Lime 385

14.4.2 Treatment With Limestone 386

14.4.3 Wetlands 387

14.5 Modern Day's Technique for Sulfate Removal 387

14.5.1 Nanofiltration 387

14.5.2 Electrocoagulation 388

14.5.3 Precipitation Methods 389

14.5.4 Adsorption 391

14.5.5 Ion Exchange 392

14.5.6 Biological Treatment 393

14.5.7 Removal of Sulfate by Crystallization 394

14.6 Conclusions and Future Perspective 394

Acknowledgment 395

References 395

15 Risk Assessment on Human Health With Effect of Heavy Metals 401
Athar Hussain, Manjeeta Priyadarshi, Fazil Qureshi and Salman Ahmed

15.1 Introduction 402

15.2 Toxic Effects Heavy Metals on Human Health 403

15.3 Biomarkers and Bio-Indicators for Evaluation of Heavy Metal Contamination 406

15.3.1 Hazard Quotient 407

15.3.2 Transfer Factor 407

15.3.3 Daily Intake of Metal 408

15.3.4 The Bioaccumulation Factor 409

15.3.5 Translocation Factor 410

15.3.6 Enrichment Factor 410

15.3.7 Metal Pollution Index 412

15.3.8 Health Risk Index 412

15.3.9 Pollution Load Index 412

15.3.10 Index of Geo-Accumulation 413

15.3.11 Potential Risk Index 413

15.3.12 Exposure Assessment 414

15.3.13 Carcinogenic Risk 415

References 417

16 Water Quality Monitoring and Management: Importance, Applications, and Analysis 421
Abhinav Srivastava and V.P. Sharma

16.1 Qualitative Analysis: An Introduction to Basic Concept 422

16.2 Significant Applications of Qualitative Analysis 422

16.2.1 Water Quality 424

16.2.2 Water Quality Index 426

16.3 Qualitative Analysis of Water 427

16.3.1 Sampling Procedure 428

16.3.2 Sample Transportation and Preservation 429

16.3.3 Some Important Physico-Chemical Parameters of Water Quality 431

16.4 Existing Water Quality Standards 434

16.5 Quality Assurance and Quality Control 435

16.6 Conclusions 437

References 437

17 Water Quality Standards 441
Hosam M. Saleh and Amal I. Hassan

17.1 Introduction 442

17.2 Chemical Standards for Water Quality 443

17.2.1 Physical Standards 443

17.2.2 Chemical Standards for Salt Water Quality 445

17.2.3 Biological Standards 446

17.2.4 Radiation Standards 447

17.2.5 Wastewater and Water Quality 447

17.3 Inorganic Substances and Their Effect on Palatability and Household Uses 451

17.3.1 Aluminum 451

17.3.2 Calcium 451

17.3.3 Magnesium 452

17.3.4 Chlorides 452

17.4 The Philosophy of Setting Standards for Drinking Water (Proportions and Concentrations of Water Components) 457

17.5 Detection of Polychlorinated Biphenyls 458

17.6 The Future Development of Water Analysis 459

17.7 Conclusion 460

References 460

18 Qualitative and Quantitative Analysis of Water 469
Amita Chaudhary, Ankur Dwivedi and Ashok N Bhaskarwar

18.1 Introduction 469

18.2 Sources of Water 470

18.3 Water Quality 472

18.3.1 Physical Parameters 472

18.3.2 Chemical Parameters 472

18.3.3 Biological Parameters 474

18.3.4 Water Quality Index 474

18.4 Factors Affecting the Quality of Surface Water 476

18.5 Quantitative Analysis of the Organic Content of the Wastewater 477

18.5.1 Biochemical Oxygen Demand 477

18.5.1.1 DO Profile Curve in BOD Test 478

18.5.1.2 Significance of BOD Test 479

18.5.1.3 Nitrification in BOD Test 480

18.5.2 Chemical Oxygen Demand 480

18.5.3 Theoretical Oxygen Demand (ThOD) 482

18.6 Treatment of Wastewater 483

18.6.1 Primary Treatment Method 484

18.6.1.1 Pre-Aeration 484

18.6.1.2 Flocculation 484

18.6.2 Secondary Treatment 485

18.6.2.1 Aerobic Biological Process 485

18.6.2.2 Anaerobic Biological Treatment 485

18.6.2.3 Activated Sludge Process 487

18.6.3 Tertiary Treatment 488

18.6.3.1 Nutrients Removal 488

18.6.3.2 Phosphorus Removal 490

18.6.3.3 Ion-Exchange Process 490

18.6.3.4 Membrane Process 491

18.6.3.5 Disinfection 491

18.6.3.6 Coagulation 491

18.7 Instrumental Analysis of Wastewater Parameters 492

18.7.1 Hardness 492

18.7.2 Alkalinity 492

18.7.3 pH 493

18.7.4 Turbidity 493

18.7.5 Total Dissolved Solids 494

18.7.6 Total Organic Carbon 494

18.7.7 Color 495

18.7.8 Atomic Absorption Spectroscopy 495

18.7.9 Inductive Coupled Plasma-Mass Spectroscopy 496

18.7.10 Gas Chromatography With Mass Spectroscopy 497

18.8 Methods for Qualitative Determination of Water 497

18.8.1 Weight Loss Method 497

18.8.2 Karl Fischer Method 498

18.8.3 Fourier Transform Infrared Spectroscopy Method 499

18.8.4 Nuclear Magnetic Resonance Spectroscopy Method 499

18.9 Conclusion 500

References 500

19 Nanofluids for Water Treatment 503
Charles Oluwaseun Adetunji, Wilson Nwankwo, Olusola Olaleye, Olanrewaju Akinseye, Temitope Popoola and Mohd Imran Ahamed

19.1 Introduction 504

19.2 Types of Nanofluids Used in the Treatment of Water 505

19.2.1 Zero-Valent Metal Nanoparticles 505

19.2.1.1 Silver Nanoparticles (AgNPs) 505

19.2.1.2 Iron Nanoparticles 506

19.2.1.3 Zinc Nanoparticles 507

19.2.2 Metal Oxides Nanoparticles 507

19.2.2.1 Tin Dioxide (TiO2) Nanoparticles 507

19.2.2.2 Zinc Oxide Nanoparticles (ZnO NPs) 508

19.2.2.3 Iron Oxides Nanoparticles 508

19.2.3 Carbon Nanotubes 509

19.2.4 Nanocomposite Membranes 509

19.2.5 Modes of Action of These Nanofluids 509

19.2.5.1 Carbon-Based Nano-Adsorbents (CNTs) for Organic Expulsion 509

19.2.5.2 Heavy Metal Removal 510

19.2.5.3 Metal-Based Nano-Adsorbents 510

19.2.5.4 Polymeric Nano-Adsorbents 511

19.2.5.5 Nanofiber Membranes 511

19.2.5.6 Some Applications of Nanofluids in the Treatment of Water 512

19.2.5.7 Informatics and AI Nanofluid-Enhanced Water Treatment 513

19.3 Conclusion and Recommendation to Knowledge 516

References 516

Index 525
Inamuddin, PhD, is an assistant professor at the Department of Applied Chemistry, Zakir Husain College of Engineering and Technology, Faculty of Engineering and Technology, Aligarh Muslim University, Aligarh, India. He has extensive research experience in analytical chemistry, materials chemistry, electrochemistry, renewable energy, and environmental science. He has worked on different research projects funded by various government agencies and universities and is the recipient of multiple awards, including the Fast Track Young Scientist Award and the Young Researcher of the Year Award for 2020, from Aligarh Muslim University. He has published almost 200 research articles in various international scientific journals, 18 book chapters, and 120 edited books with multiple well-known publishers.

Mohd Imran Ahamed, PhD, is a research associate in the Department of Chemistry, Aligarh Muslim University, Aligarh, India. He has published several research and review articles in various international scientific journals and has co-edited multiple books. His research work includes ion-exchange chromatography, wastewater treatment, and analysis, bending actuator and electrospinning.

Rajender Boddula, PhD, is currently working for the Chinese Academy of Sciences President's International Fellowship Initiative (CAS-PIFI) at the National Center for Nanoscience and Technology (NCNST, Beijing). His academic honors include multiple fellowships and scholarships, and he has published many scientific articles in international peer-reviewed journals. He is also serving as an editorial board member and a referee for several reputed international peer-reviewed journals. He has published edited books with numerous publishers and has authored over twenty book chapters.

Tauseef Ahmad Rangreez, PhD, is working as a postdoctoral fellow at the National Institute of Technology, Srinagar, India. He completed his PhD in applied chemistry from Aligarh Muslim University, Aligarh, India and worked as a project fellow under the University Grant Commission, India. He has published several research articles and co-edited books. His research interest includes ion-exchange chromatography, development of nanocomposite sensors for heavy metals and biosensors.

Inamuddin, King Abdulaziz University, Jeddah, Saudi Arabia; Aligarh Muslim University, Aligarh, India; M. I. Ahamed, Aligarh Muslim University, Aligarh, India; R. Boddula, National Center for Nanoscience and Technology (NCNST, Beijing)