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

Toyama National College of Technology

Yukina CHUJO

Fluoride Wastewater treatment 1/12

Fluoride > 10000 mg/L 20 – 30 mg/L > 10 mg/L

Sludge

CaF2M (OH)x

Ca salts (ex Ca(OH)2)

Al or Fe salts

And NaOHEffluent

Effluent

WasteWater

1st step

2nd step

Conventional Method

Problems of Conventional Method 2/12

Fluoride > 10000 mg/L 20 – 30 mg/L > 10 mg/LSludge

CaF2M (OH)x

Ca Salts (ex Ca(OH)2)

Al or Fe salts

And NaOHEffluent

Effluent

WasteWater

1st step

2nd step

unsuitable foragricultureAl and Na

damage soil

huge amount of wet sludge

impact to landfill

not remove fluoride efficiently

not to meet environmental

standard 8mg/L

Reaction of DCPD 3/12

DCPD(CaHPO4 ・ 2H2O)

Environmental reparation technique using DCPD

acid proof,hardly soluble

( Ca10(PO4)6F2 )

FApHA(Ca10(PO4)6(OH)2)

＋ Acid ＋ Fluoride

hint ： anticarious fluoride application

F-

F-

F-

- immobilize small amount of fluoride in water by forming Fap

- No addition of excess chemicals are needed.

Problem of DCPD 4/12

0

5

10

15

20

0 100 200 300 400 500 時間 / min

フッ化

物イ

オン

濃

度/

mg dm

-3

lag time

lag time

product B

product A

Fig.1 Difference of DCPD’s reactivity with fluoride ion

fluor

ide

ion

mg

/ L

time / min

Reactivity of each DCPD is quite different by the kinds

100 μm

25 μm

Nano-Etching DPCD 5/12

Before After

1 mm1 mm

10mm10mm

TreatmentIn

Hot Water

1.2 m3/g 4.8 m3/g

by-product DCPDfrom food industry

nano surface structure→Nano-Etching DCPD

Fig.2 SEM images of DCPD particles

Difference in DCPD

Fig.8 　 Reaction of DCPD

0

5

10

15

20

0 100 200 300 400 500 時間 / min

3 hours lag time

By-Product DCPD(before treatment)Nano-Etching DCPD

(after treatment)

no lag time

6/12

Flu

orid

e m

g /

L

time / min

Method Comparison

Nano-EtchingDCPD

Nano-EtchingDCPD

By-ProductDCPD

By-ProductDCPD

able to remove fluoride ion efficientlybecause of having no lag time

ConventionalFluoride Treatment

ConventionalFluoride Treatment

- treatment performance- amount of generated sludge- cost efficacy

？

7/12

cheaper but inefficient

Experiment 8/12

Fluoride Ion Solution500ml

Mix for 1hr Add Flocculant

DCPD 0.03 ～ 0.09gor

Al2(SO4)3 0.2 ～ 0.35g

Fluoride Analysis

pH adjustin

Al precipitation

・ Gas Chromatography・ Ion Selective Electrode

Fluoride Ion Solution500ml

Mix for 1hr Add Flocculant

DCPD 0.05gor

Al2(SO4)3 0.25g

Observation

pH adjustin

Al precipitation

Weight measurementof Sludge

Decantation

Fig.3 Experimental Procedure

Result

0

2

4

6

8

10

12

0 1 2 3

時間 / h

NE- DCPD 0.09g

硫酸 アルミニウム 0.3g

time / hour

9/12

Flu

orid

e io

n m

g/L

Fig.4 　 Changes of fluoride ion

aluminum sulfate 0.3g

Property of Sludge 10/12

NE-DCPD Aluminum salt(gel like precipitate)

Size (mm)F

ract

ion

(%)

Large particle size= easy to filtration !!

NE-DCPD

Time (min)

Filt

ratio

n ra

tio (

-)

ConclusionTable1 Comparison between NE-DCPD and Aluminum

11/12

Nano-EtchingDCPD

AluminumSulfate

RemovalControl

- Additive-Time Time

ChemicalsAmount 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.

Thank you for your attention