Supplementary Material. Fluoride Removal from Water Using High-Activity Aluminum Hydroxide

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1 Elctronic Supplmntary Matrial (ESI) for RSC Advancs. This journal is Th Royal Socity of Chmistry 05 Supplmntary Matrial Fluorid Rmoval from Watr Using High-Activity Aluminum Hydroxid Prpard by th Ultrasonic Mthod Wi-Zhuo Gai a,b, Zhn-Yan Dng a, * and Ying Shi b a Enrgy Matrials & Physics Group, Dpartmnt of Physics, Shanghai Univrsity, Shanghai 00444, China b School of Matrials Scinc and Enginring, Shanghai Univrsity, Shanghai 00444, China *Author to whom corrspondnc should b addrssd. Tl: , Fax: , zydng@shu.du.cn. Adsorption dynamics Th adsorption kintics dscribs th rat of adsorbat uptak on adsorbnt, which dtrmins th adsorption uilibrium tim. Undrstanding of adsorption kintics is hlpful for modling th adsorption procss and dsigning adsorptionbasd watr tratmnt systms. Psudo-first-ordr and psudo-scond-ordr adsorption kintic modls wr usd to analyz th xprimntal data for th F - adsorption onto UAH. Th psudo-first-ordr adsorption kintic modl is xprssd as follows

2 k log( t ) log t (S).303 whr and t ar th amounts of F - adsorbd (mg/g) at uilibrium and at tim t, rspctivly, and k is th adsorption rat constant, which can b dtrmind from th slop of linar plot of log( - t ) vrsus t. Th psudo-scond-ordr adsorption kintic modl is xprssd as follows t t k t (S) whr k is th adsorption rat constant, which can b dtrmind by plotting t/ t vrsus t. Fig. S shows th psudo-first-ordr and psudo-scond-ordr kintic plots for th fluorid rmoval from solution with diffrnt initial F - concntration using UAH at 5 C. Th kintic paramtrs for psudo-first-ordr and psudo-scond-ordr kintic modls ar givn in Tabl S. From th corrlation cofficint R, it can b sn that th adsorption kintics data for UAH fit bttr with th psudo-scond-ordr kintic modl, indicating that F - adsorption onto UAH follows th scond-ordr adsorption.. Adsorption isothrm Langmuir, Frundlich and Dubinin-Radushkvich (D-R) adsorption isothrm modls wr usd to analyz th xprimntal data for F - adsorption onto UAH. Th Langmuir isothrm modl assums that adsorption taks plac on a homognous surfac by monolayr adsorption without intraction btwn adsorbat spcis, which is givn by th following uation

3 ( K max L ) C max (S3) whr max is th maximum thortical amount of F - adsorbd on adsorbnt, C is th uilibrium concntration of F - in solution and K L is th binding nrgy constant. Th Frundlich isothrm is basd on non-idal adsorption on htrognous surfacs as wll as for multilayr adsorption, which is givn by th following uation log log K F log C n whr K F is isothrm constant, and n is th Frundlich constant rlatd to th (S4) favorabl dgr of adsorption. Whn th valu of n is btwn and 0, th adsorption is bnficial. Fig. S shows Langmuir and Frundlich adsorption isothrm plots for th fluorid rmoval from auous solution using UAH at 5 C. Th paramtrs of Langmuir and Frundlich adsorption isothrms for F - adsorption onto UAH ar givn in Tabl S. It can b sn that th adsorption xprimntal data fit bttr with Frundlich isothrm modl, indicating that F - adsorption on UAH is multilayr adsorption. Th valu of n is 3.054, implying that F - adsorption onto UAH is bnficial. In ordr to analyz whthr th adsorption is physical or chmical adsorption, D- R adsorption isothrm modl was usd to analyz th xprimntal data, which is dscribd by th following uation ln ln max K (S5) whr K is a constant rlatd to th adsorption nrgy, and th Polanyi potntial is 3

4 givn by RT ln( ) C (S6) whr R is th gas constant and T is th adsorption tmpratur. Fig. S3 shows D-R isothrm plots for th fluorid rmoval using UAH at diffrnt tmpraturs. Th paramtrs of D-R adsorption isothrms for F - adsorption onto UAH ar givn in Tabl S3. From th valu of R, it can b sn that th xprimntal data fit wll with th D-R isothrm modl. Th valu of max dcrass with incrasing th tmpratur, also indicating that F - adsorption onto UAH is an xothrmic procss. Th K valus can b usd to calculat th adsorption nrgy, E, using th following uation E (K) / (S7) and E can b usd to stimat th adsorption typ. If th valu of E is btwn 8 and 6 kj/mol, th adsorption procss is chmical adsorption; if E is blow 8 kj/mol, th adsorption procss is physical adsorption. Th calculatd adsorption nrgy E for UAH is ~ 0 kj/mol, indicating that F - adsorption onto UAH is a chmical adsorption procss. 3. Thrmodynamic study To valuat th thrmodynamic fasibility of th adsorption procss, thr basic thrmodynamic paramtrs, standard nthalpy ( H 0 ), standard ntropy ( S 0 ) and standard fr nrgy ( G 0 ) wr calculatd using th following uations 3 4

5 0 0 S H log( ) ( ) C.303R.303R T (S8) G 0 H 0 T S 0 (S9) whr /C is th adsorption affinity. Th thrmodynamic paramtrs wr calculatd from th plot of log( /C ) vrsus /T for dfluoridation tst using UAH at an initial F - concntration of 0 mg/l, as shown in Tabl S4. Th H 0 for F - adsorption onto UAH is -9.3 kj/mol, indicating that F - adsorption is an xothrmic procss. Th G 0 for F - adsorption is about -8 kj/mol, and th ngativ valu of G 0 suggsts that F - adsorption onto UAH is favorabl and spontanous in natur. Rfrncs Y. Shan and H.M. Guo, Chm. Eng. J., 03, 3, A. L. Srivastav, P. K. Singh, V. Srivastava and Y. C. Sharma, J. Hazard. Matr., 03, 63, X. L. Zhao, J. M. Wang, F. C. Wu, T. Wang, Y. Q. Cai, Y. L. Shi and G. B. Jiang, J. Hazard. Matr., 00, 73,

6 Fig. S. (a) Psudo-first ordr kintic and (b) psudo-scond ordr kintic plots for fluorid rmoval from auous solution with diffrnt initial F - concntrations using UAH at 5 C. Fig. S. (a) Langmuir adsorption isothrm and (b) Frundlich adsorption isothrm plots for fluorid rmoval from auous solution using UAH at 5 C. 6

7 Fig. S3. Dubinin-Radushkvich isothrm plots for fluorid rmoval from auous solution using UAH. Tabl S Kintic paramtrs of psudo-first-ordr and psudo-scond-ordr modls for F - adsorption by UAH at 5 C. C 0 (mg/l)* Psudo-first-ordr Psudo-scond-ordr k (min - ) (mg/g) R k (g/mg min) (mg/g) R *C 0 is th initial F - concntration in auous solution. 7

8 Tabl S Paramtrs for Langmuir and Frundlich isothrm modls for F - adsorption by UAH at 5 C. Langmuir paramtrs Frundlich paramtrs max (mg/g) K L (L/mg) R K F n R Tabl S3 Paramtrs for D-R isothrm modl for F - adsorption by UAH. Tmpratur (K) m (mg/g) K R E (kj/mol) Tabl S4 Thrmodynamic paramtrs for F - adsorption by UAH. H 0 (kj/mol) S 0 (J/mol K) G 0 (kj/mol) R 5 C 35 C 45 C 55 C