%& 162ῌ῍      +/  1  ,/    +/  +,  , !"Removal of Arsenic in Geothermal Water
by Addition of Adsorbents
Satoshi TAKAHASHI, Hidetoshi HIRAHARA, Sumio AISAWA and Eiichi NARITA
Department of Chemical Engineering, Faculty of Engineering, Iwate University

Abstract
The Kakkonda geothermal well, located in the northwestern area of Iwate Prefecture,
Japan, is a hot water eminent-type well, from which a large quantity of hot water isconstantly discharged with steam. However, since the geothermal water usually contains about . mg/l of arsenic, all the water is returned deep below the surface through aninjection well to preserve the natural environment. In this study, the removal of arsenicfrom the geothermal water has been attempted using an adsorbent in order to develop
the utilization of the waste water. The adsorbent used here was prepared by supportingiron(III) chloride reagent into the commercial charcoal produced from Akamatsu. Firstthe oxidation of As(III) in the geothermal water was investigated using ozone gas, dilutedhydrogen peroxide solution, bleaching powder etc. as an oxidant in the batch wise
experiments. Then the As(V)-contained water was passed through the column packed
with the Fe(III)-loaded adsorbent to remove As(V). As the ﬁnal procedure, the outﬂow
water was neutralized by addition of powdered limestone because it became gradually
acidic by hydrolysis of Fe(III) ion in the adsorbent.
In the oxidation experiments of As(III), the oxidation method using ozone was foundto be superior to any other oxidation methods. In the on-site experiments using thecontinuous ﬂow column, the residual arsenic concentration was decreased to *.+ mg-As/l for about +* min under the following optimum condition ; Oxidation rate of As(III) byozone, , mg-O-/min at /*#, Flow rate of the geothermal water, -** ml/min, Weight of theFe(III)-loaded charcoal with a grain size of /$+* mm, +** g. With the elapse of thereaction time, the residual arsenic concentration was gradually increased beyond *.+mg-As/l, which was left as a residual problem. It was also found that the charcoal wase#ective not only as the supporting material, but also a ﬁlter of ﬁne particles of theresulting arsenic-contained precipitate.
Key words : Geothermal water, Removal of arsenic, Adsorption, Iron(III) chloride, Charcoal© /- ¼ ,**.

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1 As ῌ "FG"+S gCHIH$Ik)?2lmJ?Kn LGMI8NoOP *.+ mg-Asῌl pC?qQjh1rR45 STs1UV,?tjWu1vn\]()w5 +xy XKY] +32- 1
8 ῌ ZdgC?@j=>8Wu" z{|>?@[}STs"?
1(]~\8]^", Egues ]+321

 Huang ]+323

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,-, GH 167 !

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12.2! Q|1 As T%$ ->. mgῌl$` 0*ῌ

T1Q2!

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Table +Years

pH

pH+31,24**·+330 ·243*

T-As As(III) T-SiO, Na¶K¶Ca,¶Mg,¶(mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l)-2,·/,/

0..
·100.,·12/42·14*

d.+2·123-.,·//*-.
·22

T-Fe

Al-¶

CldSO.,d(mg/l) (mg/l)*4*,*4**4*+
3/1·*4,. ·*4.* ·*4+/ ·+*+1

T-As As(III) T-SiO, Na¶
K¶
Ca,¶
Mg,¶
(mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l)
-4.
·.40

165

Chemical composition of the Kakkonda geothermal water.

+331
24,.
-4*2+422·+333 ·24-3 ·.4,0 ·,40/Years

RS%'(%ABT-FeAl-¶/4/*4*+*4**4*+·+*43 ·*4-. ·+4-/ ·,40/++*·+03

CldSO.,d(mg/l) (mg/l).,2·3-.

/+·+-1

T : Total
Data of +331·+333 : This work
Data of +31,·+330 : Umetsu et al  !"#$%& '(῎)"*+,-./01 2324.3&56,7 89:;%<,=>?"@'(AB%CDEF#G@$,? H%I%JKL;%M$, '(#PQ A$NORS&(T$, As UῌV %(WX'Y9Z[@ 7%;\ ]#! Ag- AsO- Co- UAsO-V, ^8_Zn- UAsO-V, #L?<9 H@`@ab +.+c+*d+1 ,.,c+*d,* ^8_ ,.2c+*d,* eG@$,? 7@"fghijklm&n#$ ) '( o As U῍V %(&#fg?NO"@, p FeAsO. AlAsO. Ca- UAsO.V, ^8_ Mg- UAsO.V,& H@`@ab /.1c+*d,+ +.0c+*d+0 0.2c+*d+3 ^8_ +.3c+*d,* ?"@$, 7@"%>qR r%>&<s t;?u#@v[,>&<, ) H%wx%yz["#$%& CD& {'(%o UῌV %|}~$6,7

6,
-ῌ, ῎ῑ῍ῐ῏'(%o$ " U+310V o - volῌH, O, R O-$,? 7@ )"'(t% &
CD&

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r6,h%a /* &JKLa#$? ijk& /* %R @$,%& a o  s
Fig. +

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( UCa UClOV,V )f*­ $*ao^8_®¯+¯&°± /*+ mmol^², As UῌV %+**ῌ o ,( UO V %-,. UmmolV H%% H@`@³´ e6
O- : 3.0 mmol +** V /. ,.+2 mg-O-ῌmin U+1 mlῌsecV ¯ῌ&%b 0µ -.2c+*, m,ῌlR¹º»¼166-* sec H, O, : +-/ mmol / min Ca ClO, : ..+mmol +.+ g +* min  : -,3 mmol *./A +* min H, O, Ca  ClO,  !"#$ %&'()"*+,- ./0123456
9

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"<= ῌ "2^_I `a<=bB@
Jc9VdS Fig. , efmin "

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Ozonizer : *.20 mg-O/min
As(III) : . mg/l,+** ml -** mlῌ

min "g8῍(M)S;85h:2 ijkSlmWXnok@JpqpLkrst 2 m"uvr V w +x R ῌ TUWX+** g Yῌk ,* min Fig. , yz{|} -"+~"!:`a<=bB :-"  WX +** g FG

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@ +* min AB " GV ,* min  + mgῌl V,** g Yῌk"`

a<=bB *.+ mgῌl "U+x+/ min AB

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O§: m :!¡-6¨ ¦ pH O

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ª«¬V¦ ­  %R ῌ ®¯°
5J:±²S f:³´ :R ῌ TUWXS;V  !L  WX@J ¥VFe ῌ '()lr6 µ¶

Fig. , Removal of arsenic in geothermal waterby Fe(III)-loaded charcoal (Column method).
Fe(III)-loaded charcoal : Grain size ; /·+*mm, .., mg-Fe / g charcoal, Limestone(Neutralizer) : Grain size ; /·+* mm, Weight ;+,/* g, Geothermal water : Temperature ;/*¸, Flow rate ; -** ml/min, Ozone ﬂow
rate : +,** ml/min, Column pipe length ;3** mm, Measurement of arsenic :Immediately after over ﬂow.

» /- ¼ ,**.

¸u+#12op¹º167

 Fe ῌ   Fe-!!-H, O"Fe OH -!-H!

#$% &'()'*  ῌ+#$,-(./%  01*2*34+52 ῌ  6 7 '89 :;<=>?% @A89
 ClB = Fe ῌ CD  E34
+F%  52 6 ῌ GHIJK Fig. .  6 LMNOP 0* min Q% 34+8) % R
Fig. - Time variation of residual As(III) concentration and pH value in geothermal water
after neutralization by limestone.
Initial As concentration : -.2. mg/l
Water : After oxidation, -** mi/min, /*·Fe(III)-loaded charcoal : +** g
Cl vs Fe mol ratio : +.32 I% ST34 52UV 6= JK% 34+ ClB Fe ῌ ( 6=(W5X ῌ)9 )9YZ

$%  89 =[\HW]^_M`X52% 89 abc 6 d efg)9(+% h ῌ  6(i2*<=jW  ῌ  6k*l % 89 k*l m#(% Rn=op,qK(r-l*$stE% u=vwv
=x% y ῌ (vwv 5% z< {!("#01&*2*5X  | }&$~(%& 'Fig. . Elution of Fe(III) from Fe(III)-loaded charcoal.
Geothermal water : Temperature ; /*·, Flowrate ; -** ml/min()*c%    D u *.*, mgῌl GH+=x, +* min -"#( $% )*+<q.

tW d% /u / *.+ mgῌl W$% & ./01*X ~}&$0 %&xn 123Q% ῌ34++ g% op#L(¡k% 89 # ῌ 45g% LD¢N(£yQ ῌ 34+¤¥¦§ ¨©ª Fig. /   « X ¬­ ®
M ¯ EPMA #°p±JK% ²6³5<#(% ´  Fe% Si (²µ- % 7¶* As <ῌ5*(2²µ- = % op#L,F8 +x·¸

168Fig. /SEM photographs of Fe(III)-loaded charcoal before and after treatment of geothermal water.

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1 m ^ +(I-)=      !"# $% !&'() 169

*!& +,-. /01 !)" +2#3!($+4 5%& ῍6!&7)8$
9'(:;<῍)=*>?

-.,@ 3*A BC;<DEC+  /*A ,D FE  GῌH I- JKL)=.MN $/OPQRS012 TR!&#3;<UVV 45 +W;</>637&):.ῌ ῎ ῍ ῏
XN GῌH  Y

I-Z[8Y  GῌH Q\]^

_ +W9`Na +2I-T+bJKL )= cdW
:e 0* mm ; 3** mm fghi j  1* mg-Feῌgl+* mm  GῌH  ClῌFe k<= , >e / +** g ?ῌ )4j (@m >e /l+* mm AnA+,,/* g ?ῌi:B CD . mg-Asῌl /*A \o]I- GῌH Np -** mlῌmin q>8E> = +* min r)=4FG *.+ mg-Asῌl s  d HI)!t uJvKwL(.T+bxM
NOr P!& $!9'^Q2 :

Ryz{ 1 (T+bS(  |LK!

}

+2 ZI-~T 2U: V (@mAnA +2VW ){5:sXd$ $YZuJv[ " \ῒῑRyz]^ _2 `yzcWRabc9d e

!$b yzfdR9g ehV iRjNvGH ῎kvl GHY AnA GHmnT+bZ(@o-vvpqrisl+2t" V@ TYuv ¡w¢£x¤2  yz!hV !T Ryz 2{jv G¥HY¦|§}ud$¨~yz{:2 ©ª«¬ ­X®Vΐῐ

abc9 kj (  ¯° G+331H : 1 m ^ +(JKL)= E
± .1 G+H +.῍,+.
abc9 ¦²  ³´ kj G+333H : (I-)= iRE±µ¶2· ,+ p. -/.
¸¯¹ º C» G+32-H : N GῌH a& +(I-)= N -, +++῍++0.
H.E. Egues and E.H. Cho (+321) : Adsorption of Arsenic on Activated Charcoal, Journal of

jk&!

170

Metals, 1, -2῍.+.
C.P. Huang and L.M. Vanl (+323) : Enhancing As/ removal by a Fe,-treated activated carbon,Journal WPCF, 0+, +/30῍+0*-.
H. Matsunaga, T. Yokoyama, R. J. Eldridge and B.A. Bolto (+330) : Adsorption characteristicsof arsenic(III) and arsenic(V) on iron(III)-loaded chelating resin having lysine-Na,Na-diacetic acid moiety, Reactive & Functional Polymers, ,3, +01῍+1..

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N. Wakao, H. Koyatsu, Y. Komai, H. Shimokawara, Y. Sakurai and H. Shiota (+322) : Microbial
Oxidation of Arsenite-Oxidizing Bacteria in Acid Mine Water from a sulfur-Pyrite Mine,
Geomicrobiology Journal, 0, ++῍,..

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