0. Removal of fluoride in waste waters by using calcium phosphate (DCPD)
Proceedings of the 2012 Japan-Taiwan Symposium on intelligent Green and Orange (iGO) Technology
Removal of fluoride in waste waters by using calcium phosphate (DCPD)
Toyama National College of Technology Yukina CHUJO

1. Fluoride Wastewater treatment
1/12
Conventional Method
Ca salts (ex Ca(OH)2)
Waste
Water
Al or Fe salts
And NaOH
Effluent
Effluent
1st step
CaF2
M (OH)x
2nd step
Sludge
Fluoride > mg/L – 30 mg/L > 10 mg/L

2. Problems of Conventional Method
2/12
unsuitable for agriculture Al and Na damage soil
Fluoride > mg/L – 30 mg/L > 10 mg/L
Sludge
CaF2
M (OH)x
Ca Salts (ex Ca(OH)2)
Al or Fe salts
And NaOH
Effluent
Waste
Water
1st step
2nd step
not remove fluoride efficiently not to meet environmental standard 8mg/L
huge amount of wet sludge impact to landfill

3. acid proof, hardly soluble
Reaction of DCPD
3/12
hint：anticarious fluoride application
acid proof, hardly soluble F-
＋Acid HA
(Ca10(PO4)6(OH)2)
＋Fluoride
DCPD
(CaHPO4・2H2O)
( Ca10(PO4)6F2 )
FAp F- F-
- immobilize small amount of fluoride in water by forming Fap - No addition of excess chemicals are needed.
Environmental reparation technique using DCPD

4. Problem of DCPD
4/12
Reactivity of each DCPD is quite different by the kinds
lag time
lag time
fluoride ion mg / L
25 μm
product B
100 μm
product A
time / min
Fig.1 Difference of DCPD’s reactivity with fluoride ion

5. Nano-Etching DPCD 5/12 Before After 1.2 m3/g 4.8 m3/g
by-product DCPD from food industry
nano surface structure
→Nano-Etching DCPD
Treatment In
Hot Water
10mm
10mm
1.2 m3/g
4.8 m3/g
1 mm
1 mm
Fig.2 SEM images of DCPD particles

6. Difference in DCPD 6/12 3 hours lag time Fluoride mg / L no lag time
By-Product DCPD (before treatment)
Nano-Etching DCPD (after treatment)
time / min
Fig.8　Reaction of DCPD

7. Conventional Fluoride Treatment
Method Comparison
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able to remove fluoride ion efficiently
because of having no lag time
cheaper but inefficient
By-Product DCPD
Nano-Etching DCPD ？
Conventional Fluoride Treatment
treatment performance
amount of generated sludge
cost efficacy

8. Experiment 8/12 Fig.3 Experimental Procedure
Fluoride Ion Solution 500ml
Fluoride Ion Solution 500ml
DCPD 0.03～0.09g or
Al2(SO4)3 0.2～0.35g
DCPD 0.05g or
Al2(SO4)3 0.25g
pH adjust in
Al precipitation
pH adjust in
Al precipitation
Mix for 1hr
Add Flocculant
Mix for 1hr
Add Flocculant
Observation
Decantation
・Gas Chromatography
・Ion Selective Electrode
Weight measurement of Sludge
Fluoride Analysis
Fig.3 Experimental Procedure

9. Result 9/12 aluminum sulfate 0.3g Fluoride ion mg/L time / hour
Fig.4　Changes of fluoride ion

10. Property of Sludge 10/12 Fraction (%) Size (mm) Filtration ratio (-)
NE-DCPD
Fraction (%)
NE-DCPD
Aluminum salt
(gel like precipitate)
Size (mm)
Filtration ratio (-)
Large particle size
= easy to filtration !!
Time (min)

11. Conclusion 11/12 Nano-Etching DCPD Aluminum Sulfate Removal Control
Table1 Comparison between NE-DCPD and Aluminum
Nano-Etching DCPD
Aluminum Sulfate
Removal Control
- Additive -Time
Time
Chemicals Amount
0.1 kg/m3
0.5 kg/m3
pH Adjustment
No Need
NaOH：0.1 kg/m3
Sludge Amount
0.09 kg/m3
0.3 kg/m3
Filtration
Good
Bad
Final Evaluation ○ △

12. Summary
12/12
In this study, we applied the reaction of DCPD to fluoride solution treatment.
The results of the research were summarized as follow;
By using nano-activated DCPD, the particle size was not changed after water treatment. If suitable particle of DCPD is applied, obtained sludge seems to be separated by conventional filtrations.
By using the DCPD, fluoride in waste water was easily removed, and a less amount of chemicals is needed than conventional method using aluminium sulphate.

13. Thank you for your attention