IVGHIEIXI CIJU LUQT S O OAC TIIVH CLIA PHYTOL FH (CAY HOA THACH) TACH T U RQIVI R A
Nguyin Ngge MinhS Ph^m Thi DinhS Lj^Thi HingS Nguyin Th| Thu Huou LI Thj Uln*, Dio Thj Khinh Ly', Ph^un Vin QuangS Nguyin Thj Thij
T6MTAT
Phytobth la mot d^ing Si sinh hoc tich luy nhi^u trong cdc loai cSy nhu liia, mia, tre... Nghien ciiu nay nhim xAc dinh tiem nSng sir dung phytolith tdch ra tir roni ra nhu m^t vOt li^u cai tao dO phi d i t va han ch^ su linh dpng cua mpt sd chat 6 nhi^m. Phytobth dugc tich ra khoi rom b i n g hai phuong phip la tro hoa khd va tro boa uot vd dupe sii dyng cho cac thi nghiem h.^p phu anion huu co (axit humic) va cac cation (Al**, Ca"* va K*). San phiin phytolith thu dupx- co kich thuoc tir 5 - 40 pni, trong do phuong phip tro hoa uot c6 hi^u suit tach Uiip hon do su hoa tan nipt ph^n phytolith trong moi trudng axit manh. Phuong phip tro boa kh6 neu ti^n hanh o nlii^t dp cao (>800"C) cung c6 the din d^n si; chuyen hda Si trong phytolith 6i hinh thanh cac oxit silic ben vung (crislobalite - d i t kremmezeni) v i tro n^n kh6 ti^u hon ddi voi ciy trong. Phytolith co dung Uch trao ddi cation rit \bn (157 cmol Kg') vi hdu h^t cic vj tri trao doi U-^n b^ m$t phytoliUi bj chi^m giuboi K. Hdu h^t lugng K n i y (-120g Kg') li d§ U6u vi\ c6 th^ bj U^o d6i boi CaClj0,1 moi L'. Lupng axit huniic h i p phy boi phytolith c6 th^ l6n d^'n -23 g K g ' Kha ning h i p phu cua phytobth doi voi axit humic Uiim chi c6n tAng th^m khi c6 mit cac cation voi vai tr6 "'ciu n6i". Rom r? voi m^t luong phytolith -15% chiia khoang chat quan trpng cho cSy tr6ng nhu K, Ca, Mg... Do d6 vi^c dua tro rom ra tra lai dong rupng la v6 ciing can thid't d^ hoan tra chit dinh du&ng cho d i t Mat khac, voi kha nSng hap phy ca cation va anion phytolith co the dong vai tro lam giam sy linh dpng cua cac chat 6 nhi^m (cic kim logi nang) va cai tao dp phi dat.
Tir khoa: Anion, cation, Iiap phu, phytolith (cay hoa th^ch), rom r^. 4
L DAT VAN DE phat thai c i e khi n h i kinh tir d i t vao khong kh Phytolith hay con ggi la "ciy b o a diach", l i silic f ^^^•"^, \^^'\^^'^^'' M^lhoUand & Prior, 1993 sinh hoc hinh thinh tir qui trinh but thu vi tich luy ^^' ^^ ^ ^ ^^^- ^ " ^ ^ ^ ^^^' ^ ^ ^"^ ^^^ ^ ° ^ trong mo thue vit (Rovner, 1971). Sau khi xic thuc ' f , ^ ^ " ^ ^^^' ^^^""^^ T^ ^^ ^^ ^ ^ ^^ ^^°^
vat bi phin huy phytolith duoc giai phong vio dit vi J"^^ " ^ ^ ^^^ P^'^ ^ ^ ° ^«' ^ ^ " « " ^ ^ ^ ^ " ^ ^ dong vai tro nhit dinh ddi voi cic tinh chit ly - hoa ^\ ^ J ' " ^ cac nhom silanol trin b l mit (FraysS^d dit, die biet l i kha ning h i p phu chit hiru co f^-2006) Do do. khong chi co kha ning c6 djnh ch^
(Brinkman, 1978; Mizota et al., 1982; Hassannezhad ^ ^ co PhytoUth con co t h i dong vai tro hip phu cac et al., 2008). Phytolith eo t h i khic nhau vl kich ' ' ^ ^ ° " ' ^ ^""^ ^ ° " « ^^^- ^^^^^^ ^"^ "^^ " ^ ^ ^ ^ thuoc, hinh dang tiiy thuoc vao cie loii thue vit vi v\ ^'"^ ^l^" "^"^ ^ ^ ^ phytoUth tir rom ra. B^n canh do, tri khu tni trong cic eo quan thue vit (thin, ii, rl) ^^"^ ^'^"^ ^'"^ ^ ^ ""^ ""^^ ^ ^"^ ^^^^ '^ ' ^^^ ^^' Cic loii sifeu tich luy silic (vi du: liia, mia, ng6, tre...) ^"^ Phytohth cung dugc xac djnh di lim ro vai tro CO kha ning tao ra mot lu(?ng phytolith rit Ion va giai ^""^ " ^ ^ ^^."^ " ^ ^ " " ^ ^'^"^ phytolith trong linh phong vio dit khi chet di (Marsehner, 1995; Wilding, ^ ^ ^^' ^ ° ^^^ ^^ ^ " ^^ ° "^^^'"•
1967; Parr & Sullivan, 2005). B. VAT UpJ VA PHUONG PHAP Cau tnic te b i o silic cua phytolith dugc bil't d i n ^- ^^^ ^^^
trong cac n g h i i n cuu khao co h g c v i o n h u n g n i m M a u r o m r a dugc thu t h i p tai canh dong thSii thap n i l n 60 t h i ky 20 (Wilding et al., 1967). Nhihig M i l u Nha, x i Tay M o , h u y | n Tir Li6m, Ha Noi troflE nghien cuu sau n i y cho t h i y c h i t h u u e o eo t h i hi d(?t khao s i t lay m i u ngay 2 4 / 1 0 / 2 0 1 0 . Mau rom i^
hap phu va tao lien k i t b i n vimg voi phytolith. T o e dugc r u a sach, phoi k h o t r o n g p h o n g thi nghifl, do k h o i n g hoa c h i t him e o cham lai g o p phan giam n g h i i n n h o va du<?c bao quan trong h o p plastic. Axil humic (AH) s u d u n g trong nghien cuu nay dugc tacli ' Khoa Moi truong, Truong D^i hpc Khoa hpc T\c nhien, ^^^^^ ^ "^^" ^ " ° ^iiu him ca.
Dai hpc Quoc gia Ha Npi
28 NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 10/
KHOA HOC C 6 N G N G H £
Bang 1. Thinh SiO^
74,48
Kp
17,0
phin h6a hgc ciia tro rom ra (Don vi: %) CaO
3,9
MgO 2,2
AI2O3 1.0
NagO 0,6
Fe203
0,5 2. Phuong phip
a. Tich phytolith turom ra
Hai phuong phap tro hoa kho v i tro hoa uot (Parr et al., 2001) dugc tiin hinh d l so sinh hi|u suit tich phytolith. Thi nghi$m xac dinh kha ning tiap phu AH vi cic cation sir dung phytolith tich tu rom ra theo phuong phap tro hoa kho.
Tro hda khd
Nung miu o nhiet do 500°C trong 6 h
XvL ly phan rin thu dugc voi HCl 10% (w/v: 1/5)
Hap cich thiiy o nhi|t do 7 0 ^ trong 20 p. Ly tim (3500 v/p) vi gan bo phin dich long
Tiep tuc xu ly phan rin voi H2O2 15% trong bon cich thuy 6 nhiet do 70°C.
Ly tim (3500 v/p) vi rira phin rin vii lan bang nuoc cat
Them 1 ml EtOH de qua dem v i say kho
Tro h6a u6t Mau rom dugc oxy boa trong m6i truong HNO3 dac + KCIO4 (w/v: 1/10) den khi miu chuyen tir miu niu sang ving sing
Ly tim (3500 v/p) vi rua phin rin vii lan bing nuoc cat
Them 1 ml EtOH di qua dem vi say kho
b. Xic dinh hinh thii, thinh phan hoa hoc vi kha nang hap phu cua phytolith
Hinh thii vi cau tnic ciia phytolith xic dinh voi kinh hien vi dien tu quit (SEM), miy do nhiiu xa tia X (XRD). Thinh phin hoa hgc cua phytolith dugc xic dinh theo phuong phip tro boa uot v i do tr^n miy quang pho hip thu nguyen tir (AAS).
Thi nghi$m hip phu trao doi cation: CaCl2 vdi cac nong do 1, 20, 40, 60, 80 v i 100 mmol \^ dugc su dung de xic dinh su giai phong K tir b l mit cua phytolith. 1 g phytolith dugc cho vio ong plastic chua 20 ml CaCl2 voi cic nong do neu tr6n. Miu dxxoc lie 1 h tren miy lac vi sau do ly tam 20 phiit b toe do 3000 wng/phiit. Phin dung dich tich ra dugc su dung de phin tich him lugng K tr6n miy quang k l nggn lira lenwayPFPT.
Thi nghiem hap phu axit humic: 2 g phytolith Jugc trgn voi 20 ml AH eo ning do 0,4, 0,8,1,0,1,2, 1,4, 1,8, 2,0 mg mH Lie mau trong 2 h trin miy lac sau do ngim qua dim va ly tam. Lugng AH du trong
dung dich dugc dinh lugng theo phuong phap so miu.
Thi nghi|m hip phu axit humic voi su eo mit ciia cic cation: 2 g phjrtolith trOn vdi 50 mL AH (0,5 mg mlO- Cic mu6i AICI3, CaClz, KCl dugc bo sung dgc lip sao cho cie dung djch e6 nong do cation trong khoang 0,1 1,0 N. Lie miu trong 2 h, ngam qua d6m vi ly tim. Lugng AH du trong dung dich dugc xic dinh tuong tu thi nghi|m tr6n.
UI. KET QUA VA THAO LUAN
1. Die dilm hinh thii cua phytolith trong tro romra
Phytolith tich ra tu rom ra co hinh dang vi kich thuoc khi da dang. Kit qua phin tich tr^n kinh hiin vi di|n tir quit (SEM) cho tiiiy kich thuoc phytolith chu yiu dao dgng tir 5 - 40 pm (hinh 1), khi tuong dong vdi kich thuoc phytolith gioi thi$u boi Pearsall
(1989).
Hinh 1. Anh chtip SEM rom r^ tuoi (a) v i phytoUth tich ra ttr rom r? (b)
Cie "tl bio phytolith" eo kich thuoc nho hon v i CO hinh thii ding nhat hon khi dugc tich ra theo phuong phip tro hoa uot Diiu niy chung to mot phin phytolith bi hoa tan trong moi truong axit manh dan den kich thudc phytolith giam di (thuong nho hon 10 pm). Nghiin cuu ciia Rosen (1994) ciing d i chiing minh co din -20% phytolith trong rom ra hi mit di do su hoa tan Si trong moi truong axit manh.
Ngugc lai, b phuong phip tro hoa kho khong diin ra
^ONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 10/2011 29
qui trinh hoa tan Si, do do kich thu6c phytolith nhin chung Ion hon vi dao dgng tir 10 - 50 pm. T^i nhi|t do 500"C, phan Ion cic bon huu eo bj phin buy. Tuy nhi^n mot luqmg nh6 cic bon khong chiy vin tin t^ai trong mau 6 nhi|t dO niy (Kordatos et al., 2008).
Lugng cic bon khdng chiy niy c6 thi d6ng vai tro kit dinh giira cic phytolith di hinh thiiih cie hat c6 kich thulc Ion hon.
Qui trinh xir ly rom ra b nhi|t dg cao c6 thi anh huong den dang ton tai cua Si trong phytolith. Cac oxit Si CO thi chuyin tir dang v6 dinh hinh sang cic trang thii kit tinh bin vimg hon. Kit qua phin tich nhiiu xa tia X cho miu rom xu ly o nhi|t d | 500"C cho thiy khong c6 phan xa nio die trung cho ciu tnic tinh thi. 6 nhi|t dg cao hon (800"C) oxit Si v6 dinh hinh chuyin hia thinh cristobalite (m|t dang oxit Si bin virng) vi c6 thi dugc nhin bill nhb su c6 mit ciia peak o vi tri d = 4,06 A (hinh 2) (Kordatos et al., 2008). Do viy, khi \\i ly mau d nhi|t dg cao el thi lim giim kha ning hia tan cua Si vi lim mit di ho^t tinh ciia phytolith.
Cristobalit
d'4,06 A
thi cho cic khoing sit tir nhiin tr 6 nhilm cung nhu cii tao dg phi d
1 vucxu
Hinh 2. Ph6 nhiiu xa tia X cua miu xir ly 6 500°C (a) vi 800°C (b)
2. Kha ning hip phvi cic cation ciia phytolith Phytolith dugc xic dinh li mgt "keo im" vi e6 thi dong gop vai tr6 nhat dinh dii voi cic qui trinh trong dat (Fraysse et al., 2006). Di|n tich im trin bl mit phytolith phu thuge vig cic nhdm silanol trin bl mit vi kha ning phin ly H* ciia cic nhdm niy. Khi pH moi trudng ting, H* cd xu hudng phin ly nhiiu hon vi do dd bl mit phytoUth trd nIn am di|n hon.
Diiu niy dong nghia vdi kha ning hap phu cic cation ting lln khi pH ting (Fraysse et al., 2006).
PhytoUth tach ehilt tir rom ra trong nghiin ciiu niy cd dung tich trao doi cation (CEC: 157 cmol Kg"^
kha cao so vdi mgt so khoing set tu nhien (hinh 3).
Do dd, phytolith cd thi su dung nhu mgt vat Ulu thay
160 140
^ 120 - 100
o i 80 (J 60
UI
^ 40 20
0 Phytolith Bentonit Vermiculit Kaolin
Hinh 3. Dung tich trao ddi cation ciia phytoUtfa so sinh vdi mOt sd khoing sit ti/ nhiin kaolin- Hii Duong; bentonit-C6 Djnh, Thanh Hda (Nguyfa Nggc Minh et al., 2010); vermiculit (Nguyen etal,
2006)
Thinh phin hda hgc cua phytoUth chii yiu lil vi K, trong dd K li nguyin t l chilm uu thi thii h
(-17%). K chu yiu nim b d?jig hda tan hoic d^i hip phu trao doi trin b l mit ciia phytoUth. Lugogi trao dii tir bl mit cd thi cung cip nhiing thong ti hiru ich vl die dilm b l mit vi kha ning hip pi cation ciia phytolith. Thi nghi|m trao ddi cation d thiy phytolith chiia mgt lugng K hoa tan rit Idn {4 g Kg'O vi chilm -50% him lugng K tong sd troi phytolith. Ca^* cd mit trong dung djch di thiic di phan ung trao ddi vdi K* trin b l mit phytoUth va^
din su giii phong K* (hinh 4). Khi nong d^ Cla trong dung djch t^ng tir 0 - 100 mmol t', thi lugmgl giii phdng ting l^n tuong ling la 80 -118 g Kg'. Nl viy, vin edn mgt lugrng K rit Idn (-50 g Kg-^ bj g lai boi phytoUth va khdng bj trao ddi boi CaCl2.
2,0 1
0 20 40 60 80 100 Nona dp Ca-" trong dung dich can bang (mmol L')
Hinh 4. Quan h | giOa ndng dO Ca^* trong dung dii vi him lugng K* giai phdng khoi b l mit phytolii
30 NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 10/2|j
KHOA HOC
C 6 N G N G H £3. Kha ning hip phu chit hiru co (axit humic) la phytoUth
Chat hiru eo cd kha ning bi giir vdi mgt lugng n ben trong cau tnic cua phytolith trong suit qui inh kit tiia hinh thinh cac te bao Si. Lugng "chat ru CO ngi tai" niy thuong bi eieh ly vdi moi trudng m ngoii nen cd the ton tai trong mgt thdi gian dii i khong bi phan hiiy (Wilding et al., 1967). Mat lie, chat hiru eo cung cd thi lifen kit trfen bl mit yoii cua phytolith. Kit qua thue nghi|m (hinh 5) 10 thiy phytolith cd kha ning hap phu rat Idn doi )i AH. Khi nong do AH trong dung dich tang tir 0,4 2,0 g 1\ thi lugng hap phu ting tuong ung tir 2,8 - 5,2 g Kg^). Lugng hip phu AH thim chi cd thi dat en ~ 25 g Kg"^ (kit qui dugc trinh biy d hinh 6), rong duong vdi 2,5% khoi lugng ciia phytolith.
Su hap phu ciia phytolith ddi vdi chit hiru co cd le lien quan din sir hinh thinh cic lien kit vd co - hoing. Nghien cuu ciia Fraysse et al. (2006) di tiling minh ring phytolith cd mgt bl mat mang di|n ch im vinh ciru. Do dd trong moi trudng chira cic ation se hinh thinh mgt xu hudng cic cation niy bi 1 keo vi hap phu len bl mit phytoUth dudi tic dgng ia luc hiit tinh dien van Der Waal. Ngugc lai, ghien ciiu ciia Alexandrova (1970) cho thay cic axit liin phan ling vdi cation vd co tao thinh cic mudi di re hay humat hoic fulvat. Cic mudi di cue hinh iinh cd thi tiip tuc tuong tie vdi cic hgp phan vd co Ilia Si qua ciu ndi cation de hinh thinh cic kit tia idng tan vi tao thinh cie ming bim tren bl mat .loxan. Nhu viy, mgt xu hudng cd thi hinh thinh dd
: cation se ddng vai trd tao ciu ndi trong Uen kit
*iytoUth-AH.
16 - 12 -
8 •
4 -
0/5 1,0 1,5 2,0
Nong dp AH t r o n g d u n g djch can bang (g L"^)
Hinh 5. Hip phu axit humic (AH) boi phytoUth Ndng do cation cd anh hudng nhit dinh ddi vdi
"'li ning hap phu AH cua phytolith.; Kit qua xic 'ah him lugng AH hap phu trin phytolith khi cd
mit cic cation (hinh 6) cho thay: Khi ndng do K\
Ca^* vi Al^^ ting tir 0,1 - 1,0 g V thi lugng AH hap phu tuong img li 24,4 - 24,6 g Kg\ 23,8 - 25,0 g Kg\
24,4 - 24,9 g Kg-^ Cie cation khic nhau cd bilu hiin khic nhau trong vai trd ciu ndi ciia liin kit phytoUth - AH. Trong dd, inh hudng din sir hip phu AH tr^n phytolith nhin chung tuin theo quy luit hda tri cing cao thi vai trd ciu ndi cing Idn. O ndng do cation thap (< 0,2 mmol H), Al^ cd inh hudng rd r|t nhat thiic day sir hap phu AH l€n bl mit phytolith. Tuy nhien, d cic ndng do cao hon (> 0,2 mmol L'O Al^ cd kha ning can trdxu hudng hap phu AH l^n phytolith.
Dieu niy cd thi do sir thiiy phin ciia Al tao ra H* tao ra su canh tranh hap phu Al^* vi H* tren bl mit phytolith. 6 ndng do > 0,5 moi \'\ Ca^* bieu hi|n vai trd lim cau ndi tdt hon so vdi Al^"^ Trong trudng hgp khdng cd su bd sung cic cation, phytolith vin bilu hien kha ning hap phu chit hiru co rit tdt (-24 g Kg' 0. Diiu niy cd thi do cic cation trao ddi "'sin cd"
tren bl mit phytolith (K*, Ca^*...) ddng vai trd lim cau noi.
25.5
00
3- D.
<
25,0
24,5 ;
24,0
1 ^
• /
II
1 1 —
1~
1
*
- * - A I - * - C a
— 1 1
23,5
0 0,2 0,4 0,6 0,8 1,0 Nong d$ cation trong dung djch can bang (mmol L"'-)
Hinh 6. Kha ning hip phu axit humic (AH) dia phytoUth khi cd mit cic cation
IV. K£T LUAN
PhytoUth thu dugc tir rom ra theo hai phuong phip tro hda khd vi tro hda udt cd kich thudc dao dgng ttr 5 - 40 pm, tuong duong vdi kich thudc thuong gip ciia phytolith trong nhiiu loai dat khic nhau (Pearsall, 1989). Phytolith cd trong rom ra chua mgt lugng Idn Si vd dinh hinh. Do dd, viec ddt rom ra vi bdn trd lai ddng rugng se cung cip mgt lugng ding kl Si d dang dl tieu ddi vdi ciy trdng. Kali hip phu trin bl mit phytoUth cung cd the dugc giai phdng vi li ngudn dinh duong ting cudng cho dat.
Vdi kha nang hap phu ddng thdi ca cation vi anion (die bi$t li cic anion hiru eo), mgt mit phytolith chi
flpNG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 10/2011 31
phdi cic phan ung hip phu trao ddi vi kha ning giir chit dinh duong (^H;, K^ Ca2^ Mg^*...) cua dit, mit khic phytolith lim giam kha ning di ddng vi nguy CO mit di ciia cic chit hiiu co hda tan (DOM) thdng qua qui trinh rua trdi. 6 khia cgnh mdi trudng, phytolith cd kha ning lim giam tinh linh dgng ciia chit d nhilm trong dit (vi du: kim lo^
ning) thdng qua kha nang cd djnh cie chelat. Cic yiu td mdi trudng dit nhu pH, Eh, khoing set... cd anh hudng nhat dinh din die tinh hda hgc bl mit cung nhu kha nang hip phu ciia phytolith vi se dugc tim bilu trong cic nghien cuu tiip theo.
TAILpmAMKHAO
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Tech. 11(1), 17-21.
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Handbook of Procedures. London: Academic Press.
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INVESTIGATION ON SEVERAL PHYSIO - CHEMICAL PROPERTIES OF PHYTOLITH SEPARATED FROM RICE STRAW
Nguyen Ngoe Minh, Pham TTii Dinh, Ly Thi Hang, Nguyen Thi Thu Huong Le U i i Lien, Dao Thi Khanh Ly, Pham Van Quang, Nguyen Thi Thuy
Summary
Rice straw is a major by-product of the rice processing industries, which contains large amount of opal silica (phytolith). The overall scope of this study is to investigate posibility of using phytolith to provide nutrients (available K and SO for crops and to act as absorbents for cations and anions. Phytolith was separated from rice straw by wet and dry ashing techniques and examined for cation, anion adsorptions. It was found that wet ashing yields less phytolith than dry ashing because of phytolith dissolution in strong acid. Particle sizes of phytolith ranges from 10 to 40 pm which are relatively similar to those reported by Pearsall (1989). Heat treatment at high temperature can lead to a crystallization that amorphous silica is transformed to a more stable silica (e.g. cristobalite). This crystallization is a disadvantage towards serving of silicon for plant. Phytolith has large amount of exchange sites on surface which are mainly occupied by potassium. Release of potassium up to 120 g Kg' from exchange sites of phytolith can be achieved in the presence of CaClj 0.1 M. Humic acid (HA) held by phytolith can reach 25 g Kg' Increase of cation concentration can accelerate HA occlusion on phytolith surface. With high adsorption capability for both cations and organic anions, phytolith can be a promissing candidate for soil amendment in order to improve soil quality on one hand, and to reduce mobility of contaminants such as heavy metals on the other hand.
Keywords: Anion, cation, adsorption, phytolidi, rice, straw.
Ngudi phan bi|n. TS. Bui Huy Hiin
ONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 - THANG 10/2011 33