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Water treatment-and-nanotechnology

  1. Water Treatment and Nanotechnology Prakhar Shukla Karan Singla Ravi
  2. INTRODUCTION Water is the most essential and critical for all human activities Sources of clean water are very limited While Requirement is increasing Sources is often contaminated by many causes eg; microbes, harmful chemicals, bacteria, minerals, and pharmaceuticals The amount of water to be treated should also be assessed Malaria, Cholera, Typhoid, Viral hepatitis, Skin diseases are caused by contaminated water
  3. Conventionally Used Methods For Water Treatment  Five types of contaminants are found in water Methods that are in use to remove these elements have wider Range (from simple and inexpensive to elaborate and costly) Around Twenty-five conventional methods used to purify water are divided into four categories: 1) Separation 2) Filtration 3) Chemicals 4) Oxidation.
  4. Conventionally Used Methods For Water Treatment Separation: Sedimentation, Boiling, Distillation, UV light Filtration: Sand, Diatomaceous earth, Porous stone/Ceramic, Paper/Cloth, Charcoal/Carbon Block, Reverse Osmosis, Enzymes & Bacteria, Plants.
  5. Conventionally Used Methods For Water Treatment Chemicals: Halogens(Cl, Br, I) Hydrogen Peroxide (H2O2), Silver (Ag), Nontoxic organic acids, Lime & mild alkaline agents, Coagulation-flocculation, Ion exchange Oxidation: Ozonization, Electronic Purification & Dissolved Oxygen Generation
  6. Drawbacks in present water treatment process Most of the methods available have impact either on our health or on the environment. Time consuming, Fails to remove the heavy metal, Not able to remove micro organisms, Chemical pollutants and heavy metals, Application of UV lightning require longer radiation time Removes the useful minerals and Nutrients
  7. A combination selected from the following process  Pre-chlorination for algae control and arresting biological growth  Slow-Sand filtration  Coagulant aids, also known as polyelectrolytes – to improve coagulation and for more robust floc formation.  Sedimentation for solids separation- removal of suspended solids trapped in the floc.  Disinfection for killing bacteria viruses and other pathogens
  8. Solution •The highly efficient, modular, and multifunctional processes enabled by nanotechnology are envisaged to provide high performance, affordable water and wastewater treatment solutions that less rely on large infrastructures. •Nanotechnology is the design, characterization, production and applications of structures, devices and systems by controlling shape and size at nanometer scale. • Nano Structured Materials are applicable as adsorbents or catalysts in order to remove toxic and harmful substances from wastewater.
  9. What is nanotechnology ? We all are familiar: • Greek word for dwarf • Nanotechnology is science, engineering, and technology conducted at the nano-scale, which is about 1 to 100 nano-meters • One nm is a billionth of a meter, or 10-9 of a meter
  10. The key features that make nano-particles attractive for water treatment……….  More surface area and small volume The higher the SA:V - the stronger, more stable and durable Materials may change optical, electrical, physical, chemical, or biological properties at the nanoscale level Makes biological and chemical reactions easier Can attach various reactor groups to increase the chemical affinity to words the target
  11. Adsorption : Polymeric Based nano-adsorbents and Metal based nano-adsorbent  Efficiency of current conventional adsorbents is usually limited by the surface area or active sites, the lack of selectivity, and the adsorption kinetics.  Nano-adsorbents offer significant improvement with their extremely  High specific surface area  Associated sorption sites,  Short intraparticle diffusion distance  Tunable pore size  Enhanced Surface chemistry. Current and potential applications of Nanotechnology in Water treatment: - Adsorption - Membrane Nanotechnology - Photo-catalysis - Disinfection and Microbial Control - Sensing and Monitoring
  12. Metal Based Nano-Adsorbents:  Multifunctional Magnetic nanoparticles are used as the core material in a core–shell nanoparticle structure where the shell provides the desired function while the magnetic core realizes magnetic separation.  Silica coating helps functionalization due to the rich silica chemistry.  It is a two-step process: These magnetic nanoparticles can be either used directly as adsorbents or as the core material in a core–shell nanoparticle structure where the shell provides the desired function while the magnetic core realizes magnetic separation  Metal based nanomaterials have been explored to remove a variety of heavy metals such as arsenic, lead, mercury, copper, cadmium, chromium, nickel
  13. Carbon Based Nano- Adsorbents:  Carbon absorption is a widely used method of home water filter treatment because of its ability to improve water by removing disagreeable tastes and odors, including objectionable chlorine and can be effective against microorganisms. However, generally it will not affect total dissolved solids.  Carbon Based Nano-Adsorbents(CNTs) have have shown higher efficiency than activated carbon on adsorption of various organic chemicals due to the large specific surface area and the diverse contaminante CNT interactions
  14. Membrane Nanotechnology Process  The basic goal of water treatment is to remove undesired constituents from water thus membranes provide a physical barrier for such constituents based on their size, allowing use of unconventional water sources.  A major challenge of the membrane technology is the inherent tradeoff between membrane selectivity and permeability  The performance of membrane systems is largely decided by the membrane material. Incorporation of functional nanomaterials into membranes offers a great opportunity to improve the membrane permeability, fouling resistance, mechanical and thermal stability, as well as to render new functions for contaminant degradation and self- cleaning.
  15. Nanofiber Membranes  Electrospinning is a simple, efficient and inexpensive way to make ultra-fine fibers using various materials. The resulting nanofibers have high specific surface area and porosity and form nanofiber mats with complex pore structures.  The diameter, morphology, composition, secondary structure, and spatial alignment of electrospun nanofibers can be easily manipulated for specific applications.  Functional nanomaterials can be easily doped into the spinning solutions to fabricate nanoparticle impregnated nanofibers such as nano-zeolites, nano-Ag, nano-TiO2, and CNTs TiO2 to remove heavy metals and organic pollutants during filtration.  Biologically inspired membranes  Antimicrobial nanomaterials such as nano-Ag and CNTs can reduce membrane biofouling from by organisms such as algae.
  16. Photo-catalysis:  TiO2 is the most widely used semiconductor photo-catalyst while fullerene derivatives are second most used in Photocatalytic reactors, and solar disinfection systems.  TiO2 has low toxicity, chemical stability, low cost, and abundance as raw material.  TiO2 generates an electron/hole (e−/h+) pair upon absorbing a UV photon, which later either migrate to the surface and form reactive oxygen species (ROS) or undergo undesired recombination.  The photo-activity of nano-TiO2 can be improved by optimizing particle size and shape, reducing e−/h+ recombination by noble metal doping, maximizing reactive facets, and surface treatment.  The size of TiO2 plays an important role in its solid-phase transformation, sorption, and e−/h+ dynamics.
  17. Disinfection and Microbial Control:  Nano-Ag, nano-ZnO, nano-TiO2, nano-Ce2O4, CNTs, and fullerenes are used.  These nanomaterials inactivate microorganisms by releasing toxic metal ions, compromising cell membrane integrity upon direct contact or generating reactive oxygen species with fewer tendencies to form DBPs.  Nano-Ag is a common choice for point-of-use (POU) water treatment devices because of its strong and wide-spectrum antimicrobial activity and low toxicity to humans.  The fibrous structure, antibacterial activity, and conductivity of CNTs enable their use in antimicrobial filters.
  18. Nanomaterial antimicrobial mechanisms. Nanomaterials Antimicrobial mechanisms Nano-Ag Release of silver ions, protein damage, suppression of DNA replication, Nano-TiO2 Production of ROS Nano-ZnO Release of zinc ions, production of H2O2, membrane damage Nano-MgO Membrane damage Nano-Ce2O4 Membrane damage Fullerol and aminofullerene Production of ROS Carbon nanotubes Membrane damage, oxidative stress Graphene-based nanomaterials Membrane damage, oxidative stress Nanomaterial antimicrobial mechanisms.
  19. Sensing and monitoring Quality monitoring Is a bigger Challenge. Sensors with high sensitivity and fast response are needed. Nanomaterials can improve sensor sensitivity and speed. Magnetic nanoparticles and CNTs are explored for sample concentration and purification  QDs, nanoparticles, noble metal and CNTs are widely used in nanosensor
  20.  Availability and cost,  Toxicity of nano-material,  Social acceptability must be addressed.  Potential health and environmental risks,  CNT may be cause of lung damage.
  21. CONCLUSION  Toxicity to cells in nano particles may be modified or reduced by coating the nano particles.  Already showing promising results.  Once certain impending hurdles are overcome, will solve the global water shortages.  Opportunities to develop next-generation water supply systems.

Notas del editor

  1. Thin film nanocomposite (TFN) membranes: Development of TFN membranes mainly focuses on incorporating nanomaterials into the active layer of thin film composite (TFC) membranes via doping in the casting solutions or surface modification.