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

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 > 10000 mg/L 20 – 30 mg/L > 10 mg/L

Problems of Conventional Method 2/12 unsuitable for agriculture Al and Na damage soil Fluoride > 10000 mg/L 20 – 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

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

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

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

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

Conventional Fluoride Treatment Method Comparison 7/12 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

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

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

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)

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 ○ △

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.

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