1. International Conference on Sustainable Built Environment
NANCO AND UNIVERSITY OF MELBOURNE JOINT RESEARCH SESSION ON NANOTECHNOLOGY AND SUSTAINABLE BUILT ENVIRONMENT
13-14 December, 2010 at Earls Regency, Kandy, Sri Lanka

2. DEFLOURINATION OF DRINKING WATER USING LAYERED DOUBLE HYDROXIDES
Presented by: Nadeesh Madusanka
Other group members:
Eranga Warsakoon
Nuwan Gunawardene
Hasitha Kalahe
Imalka Munaweera
Nilwala Kottegoda

3. Introduction
About 1 billion people in the world, mostly in developing countries, have no access to potable water
2.6 billion people lacking access to adequate sanitation.

4. Sri Lanka currently faces a number of water related problems.
70 % of the Sri Lankan population satisfies their water needs from dug wells, deep wells, reservoirs and rivers.

5. One of the pertaining water related problem in the dry zone of Sri Lanka
Levels fluoride ion concentrations in ground water
> 10 ppm
WHO recommended fluoride ion concentration 1 ppm

6. Adverse effects due to the excessive exposure to fluoride in drinking-water
Mild dental fluorosis to
crippling skeletal fluorosis
Chronic kidney disease (CKD)

7. Fluoride removing methods in water
Adsorption
Precipitation or Adsorption
Ion-exchange
Electro dialysis
Electrochemical Processes

8. The most common approach to remove fluoride in the dry zone
of Sri Lanka
Use of brick filters -low efficiency.
Combination of alum (or aluminium chloride) and lime (or sodium aluminate), together with bleaching powder, are added to high-fluoride water, stirred and left to settle.
Flocculation, sedimentation and filtration.

9. Currently, nanotechnology has not left any field
Untouched.
This new technology can be harnessed to provide sustainable solutions to water related problems prevailing in Sri Lanka particularly to remove fluoride ions from drinking water.

10. Possible Nanomaterials
Layered Double Hydroxide
Nano TiO2
Nano Magenetite

11. Layered Double Hydroxides
Structure-based on the Brucite ( Mg(OH)2 )structure
Isomophous substitution of M2+ of brucite by M3+.
Brucite
brucite like
layers
Inter layer region
Charge balancing
anions
4.8 nm
LDH
General formula: M2 +1-xM3+ x(OH)2.An-x/n-.mH2O
M2+ is a divalent metal ion, such as Mg2+, Ca2+, Zn2+
M3+ is a trivalent metal ion, such as Al3+, Cr3+, Fe3+
An− is any anion

12. Characteristics of Layered Double Hydroxides
Thermally stable.
A range of trivalent and divalent cationic combinations are available.
The cationic ratio can be modified within a wide range.
Large anion exchange capacity.
Can be synthesized as bulk quantities with relatively low
cost and under ambient conditions.

13. Applications of Layered Double Hydroxides
Biomedical applications-Drug stabilizer, Antacids,Gene and Drug Delivery
Catalysis- Hydrogenation,Polymerizations
Polymer nanocomposites
Ion Exchanger

14. LDH as an Ion Exchanger
Intercalation

15. Research methodology 1) Synthesis of Mg-Al-hydroxide LDH (Mg-Al-OH) +
Mixed metal solution
50 ml
Anionic solution
(Al: OH- =1:10) +
co- precipitation reaction
25 oC, pH=10
Under N2 atmosphere
MgAl-OH- LDH
Ref. Hibino and Jones , J. Mater. Chem

16. 2) Flouride removal from drinking water using Mg-Al-OH-LDH
Different weights of LDH were added to water samples containing fluoride ions (8.2 ppm ,100 ml) and kept it for 24 hours on the magnetic stirrer.
Final concentration of the fluoride solution was tested using an ion selective electrode.
The efficiency of the LDH material was compared with that of the conventional method where brick powder is used as the ion exchange medium.

17. 3) Regeneration of the material
Exhausted LDH powder was calcined at 400 oC for three hours.
Then the resulting mixed oxide was characterized by PXRD and FTIR.
Then it was exposed to 1 M NaOH solution for 24 hours with mechanical stirring and the resulting product was characterized using PXRD and FTIR.
The fluoride gas coming out was allowed to absorb into 1 M calcium hydroxide solution.

18. 4) Characterization Scanning Electron Microscopy
Powder X-ray Diffraction
Fourier Transform Infra Red Spectroscopy
Chemical Analysis

19. Results
SEM Images of LDHs

20. PXRD Mg-Al-OH LDH (b) Mg-Al-F LDH (c) mixed oxide received after
calcination of the
Mg-Al-F LDH at 450 0C
(d) regenerated mixed oxide
in the presence of OH ions.

21. FTIR Mg-Al-OH LDH Mg-Al-F LDH mixed oxide received after
calcinations of the Mg-Al-F
LDH at 450 0C

22. Weight of filter material/ (g) Flouride concentration
Flouride ion concentrations after filtering though LDHs and brick powder.
Weight of filter material/ (g)
LDH
Flouride concentration
(mg/l)
Brick powder
0.01
0.05
0.1
0.2
0.5
1.0
2.0
8.04
7.80
7.57
6.63
6.54
4.57
1.80
1.05
7.25
6.75
6.65
6.55
6.5
5.48
5.08

23. Adsorption isotherm for Mg-Al-OH LDH and brick powder

24. Proposed layout design of the purification plant
Ca(OH)2 solution inlet for regeneration
Outlet for backwash water outlet
Inlet for Chlorination
Storage
Deflouridation Columns (with LDH)
Sand filter
Bore hole
Water Pump
Treated water

25. Conclusions
Layered double hydroxides have displayed high efficiency in removing fluoride ions from drinking water compared to the basic methods currently used.
LDHs can be used in either regional water purification units or domestic house hold filters.
Product is economically and environmentally sustainable.
An added advantage of using LDHs would be its superior capability of removing other anions such as carbonate, sulfates etc

26. Acknowledgement D.S. Senanayake College, Colombo 07.
Sri Lanka Institute of Nanotechnology

27. DEFLOURINATION OF DRINKING WATER USING LAYERED DOUBLE HYDROXIDES
Research Group:
Nadeesh Madusanka
Eranga Warsakoon
Nuwan Gunawardene
Hasitha Kalahe
Imalka Munaweera
Nilwala Kottegoda