Projects Involving Nanotechnology at The Oxford Centre for Sustainable Water Engineering. Dr Nick Hankins

Transcription

1 Projects Involving Nanotechnology at The Oxford Centre for Sustainable Water Engineering Dr Nick Hankins

2 Introduction to Centre for Sustainable Water Engineering Adsorptive Micellar Flocculation Forward Osmosis Nanocatalysts Outline Macromolecular Complexation-Flocculation

3 Data: Wateraid, Chartered Institute for Environmental Health; Photo: CEH Wallingford Water Problems 1.1 billion people have no access to safe water 2.6 billion people have no proper sanitation as a result million deaths per year are related to water/hygiene/sanitation; many of these are children In the United Kingdom, one in six households may be adversely affected by water poverty.

4 Prioritization of Activity IChemE Roadmap for the 21 st Century specifically highlights water in priority position statements: Water as a Resource Sustainability and New technology Industrial Usage

5 Prioritization of Activity Sustainability and New Technology: Develop existing and implement novel potable water and waste-water treatment processes with - low cost, low energy, low environmental impact and low footprint eg membrane processes Effective removal of micro-contaminants and nitrates/phosphates from waste-water

6 Prioritization of Activity Industrial Water Usage: Seek the potential to: Reduce consumption of Recycle Recover - Water, Raw materials and Energy Beneficial sludge reduction/disposal

7 Focus of Research Activity Market Driven: Potable Water Treatment and Desalination Development of Novel Osmotic Agents for Forward Osmosis Visible-light Photocatalytic Oxidation/Disinfection Waste Water Treatment Application of Synthetic Sludge to Study Activated Sludge Process Use of Micellar Enhanced Ultrafiltration and Polyelectrolyte Complexation for Removal and Concentration of Dilute Heavy Metal Ions

8 Focus of Research Activity Market Driven: Waste Water Treatment Removal of Emerging Micro-contaminants eg EDCs, APIs eg ibuprofen, diclofenac (CEH) Process Stream Treatment Adsorptive Micellar Flocculation to Remove/Reuse Organic Acids and Bases

9 Focus of Research Activity Technology Driven: Membrane Processes MBRs, Pre-coagulation, Forward Osmosis Nanostructures Colloids and Interfaces Micellar/Colloidal Complexation, Ion-Exchange, Coagulation/Flocculation, Adsorption Environmental Microbiology Ian Thompson

10 SWT: Goals Establish an internationally leading, state-of-the-art centre of excellence in fundamental and applied research in potable, waste-water & process water treatment Be interdisciplinary: engineers, microbiologists, chemists, social scientists Leverage external support: Government, Industry EC/international organizations

11 Nanotechnology: Adsorptive Micellar Flocculation Remove and recycle valuable components - weak organic acids/bases -from aqueous effluent and process streams Develop a novel surfactant-based process: Adsorptive Micellar Flocculation (AMF) Perform pilot-plant studies to validate the process

12 Concept of Adsorptive Micellar Flocculation Heavy metal ion UF membrane Micelles Micelles Organic acid anion Flocculant Coarse filter

13 Experiments on Pilot Plant

14 removal efficiency (%) Pilot Plant Results Optimum Flocculant Dosage Pilot tests Bench tests (distilled water, from Salvation Anthony, Mres disertation, 2002) Bench tests (tap water) ratio of floculant and SDS (-) Optimum molar ratio of flocculant:surfactant for phenol removal = 0.75 (pilot rig, bench tests) Highest removal = 68.8 % (one stage)

15 Nanotechnology: Micellar-based Techniques Micellar Enhanced Ultrafiltration - Involves metal binding to micellar surface or solubilization within hydrocarbon core - Micelles and target species trapped by UF Pollutant Micelle Pollutant Problems: Pollutant - membrane fouling and large retentate stream

16 Mixed liquor Draw solution Nanotechnology: Forward Osmosis Emerging alternative to reverse osmosis for desalination Exploit natural osmotic pressure gradient from saline feed through membrane to concentrated draw solution Membrane Membrane H 2 O Osmotic pressure gradient (higher concentration) FO

17 Forward Osmosis Concentrated Draw Solution Raw Feed Solution Separation Unit Draw Solution Draw Solution Potable Water Membrane Unit

18 Forward Osmosis Contaminant Water Clean Water Draw Solution Field Gradient Lower concentration/ osmotic potential Magnetic Nanoparticle Higher concentration/ osmotic potential

19 Forward Osmosis Key Challenges: Develop an effective draw agent: high osmotic pressure, high diffusivity, low toxicity Draw agent easily regenerable from product water Develop an effective membrane to minimise internal concentration polarisation

20 Nanotechnology: Visible Light Photocatalysts Ultra-Violet only about 5% of sunlight Develop wide gap semiconductors: work in visible light Dope titanium with N 2 and Sn; phosphate materials good stability and activity Test capacity to degrade organic contaminants and kill microbial cells

21 Visible Light Photocatalysts

22 Nanotechnology:Complexation-Flocculation Heavy metal ion MEUF Micelles or Macromolecules Micelles or Macromolecules Heavy metal ion Flocculant (metal ion or polyelectrolyte) CF

23 Complexation-Flocculation Process Remove Heavy Metal ions from aqueous solution by complexation-flocculation Complex heavy metal ions to macromolecular humic substances by electrostatic interactions Flocculate humic acid and bound heavy metal ions by polyelectrolyte: charge neutralisation and polymer bridging Filter or settle flocs remove heavy metal!

24 Complexation-Flocculation Process Metal ions HS Cationic polymer flocculent Ultrafiltration membrane

25 Removal efficency (%) Removal efficency (%) Complexation-Flocculation Process Humic Acid- PolyDADMAC Flocculation Effect of PolyDADMAC dosage Effect of ph 100 ph7 100 ph3 ph5 ph7 ph Ratio of PDADMAC to HA (mass/mass) Flocculation passes through a maximum Optimum dosage increases with ph Ratio of PDADMAC to HA (mass/mass)

26 Thank-you for your Attention!

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