Removal of fluoride in waste waters by using calcium phosphate (DCPD )

1. 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 TechnologyYukina CHUJO

2. Sludge CaF2 M (OH)x 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 2nd step Fluoride > 10000 mg/L 20 – 30 mg/L > 10 mg/L

3. CaF2 M (OH)x Sludge Problems of Conventional Method 2/12 unsuitable foragricultureAl and Na damage soil Ca Salts (ex Ca(OH)2) Al or Fe salts And NaOH Waste Water Effluent not remove fluoride efficientlynot to meet environmental standard 8mg/L Effluent 1st step huge amount of wet sludgeimpact to landfill 2nd step Fluoride > 10000 mg/L 20 – 30 mg/L > 10 mg/L

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

5. 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

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

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

8. Method Comparison 7/12 able to remove fluoride ion efficiently because of having no lag time cheaper but inefficient Nano-EtchingDCPD By-ProductDCPD ？ ConventionalFluoride Treatment • treatment performance • amount of generated sludge • cost efficacy

9. pHadjustin Al precipitation Experiment 8/12 Fluoride Ion Solution500ml Fluoride Ion Solution500ml DCPD 0.03～0.09g or Al2(SO4)3 0.2～0.35g DCPD 0.05g or Al2(SO4)3 0.25g pHadjustin Al precipitation Mix for 1hr Add Flocculant Mix for 1hr Add Flocculant Observation Decantation ・Gas Chromatography ・Ion Selective Electrode Weight measurementof Sludge Fluoride Analysis Fig.3 Experimental Procedure

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

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

12. Conclusion 11/12 Table1 Comparison between NE-DCPD and Aluminum

13. 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.

14. Thank you for your attention