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

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

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.

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.

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

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

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

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.

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.

Possible Nanomaterials Layered Double Hydroxide Nano TiO2 Nano Magenetite

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

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.

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

LDH as an Ion Exchanger Intercalation

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 , 2001 J. Mater. Chem 11 1321

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.

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.

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

Results SEM Images of LDHs

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.

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

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

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

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

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

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

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