Synthesis of Multi-Walled Carbon Nanotubes and Its Application for Removal of Dyes

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1 Synthsis of Multi-Walld Carbon Nanotubs and Its Application for Rmoval of Dys S. Magswari, V. S. Angulakshmi 2* and C. Sathiskumar 3.Vivkananda Collg of Enginring for Womn, Tiruchngod, TN, India. 2. Kathir Collg of Enginring for womn,coimbator, TN, India. 3. Chickkanna Govrnmnt Arts Collg, Tirupur, TN, India. *Author to whom all Corrspondnc should b addrssd to, mmahs5@gmail.com Abstract Cymbopogn flxuous oil and Glycin max oil, natural botanical hydrocarbons, hav bn found to b fficint prcursors of multi-walld carbon nanotubs (MWNTs) synthsis. MWNTs wr prpard by Chmical Vapor Dposition of Cymbopogn flxuous oil and Glycin max oil ovr wll disprsd F/Co/Mo catalyst supportd on silica. MWNTs wr charactrizd by SEM, HRTEM, Raman spctroscopy and Nitrogn adsorption studis. Raman spctroscopy rvals that MWNTs ar wll graphitizd. Dynamic and quilibrium studis of adsorption of Basic brown-4 on MWNTs wr rportd. INTRODUCTION Carbon nanotubs (CNTs) hav bn studid xtnsivly sinc thy wr discovrd in 99[] and hav opnd a nw arna scinc and tchnology in nanoscal matrials. Thr ar fw rports on th synthsis of multi-walld carbon nanotubs (MWNTs) and vrtically alignd carbon nanotubs from camphor, turpntin oil and pin oil [2, 3, 4]. Nw aras of application of nanotubs ar constantly bing idntifid vr stimulating th scintist to pp into ths nanotubs. Sinc th discovry of multiwalld carbon nanotubs, various mthods hav bn dvlopd to obtain this nw form of carbon [7-8]. Thir synthsis mthods and charactrization hav bn studid xtnsivly. Practical applications of carbon nanotubs rquir th synthsis of carbon nanotubs with crtain wll dfind proprtis such as diamtr distribution, alignmnt, filling with various matrials tc. [9, 0]. To dat, only purifid ptrolum products such as mthan, bnzn, actyln, tc., ar in practic for synthsizing carbon nanotubs. Th advantags of using plant-drivd prcursors ar that thy can b cultivatd in rquird quantity and thr is no far of bing dpltd. Kumar and Ando prpard a mixtur of singl-walld Carbon Nanotubs (SWNTs) and multi-walld carbon nanotubs (MWNTs) by thrmal dcomposition of botanical hydrocarbon: camphor [5]. Rcntly Andrws t al synthsizd pur SWNTs by Chmical Vapor Dposition of camphor and its analogs [6]. Cymbopogn flxuous oil and Glycin max oil has bn found to b anothr promising prcursor for pur MWNTs synthsis. Ths prcursors ISSN(Onlin) : Vol. 3, Spcial Issu 28, Fbruary 207

2 ar nvironmntally frindly and no chanc of shortag in th nar futur. Th mthod which w hav bn using for th synthsis of CNTs is vry simpl and inxpnsiv. Dys inhibit svral biological procsss and also color of txtil fflunts scalats nvironmntal problm mainly bcaus of its non-biodgradabl charactristics. Rsarchrs rval that dys can b rmovd compltly from fflunts prior to thir final discharg [, 2, and 3]. Adsorption, coagulation, lctrochmical procss, oxidation, prcipitation, filtration, tc ar th common tchniqus rportd for th rmoval of dys from fflunts. Among ths tchniqus, adsorption sms to b on of th most ffctiv mthods bcaus of simpl opration and asy handling. In this papr w rport Dynamic and quilibrium studis of adsorption of Basic brown-4 on chmical vapor dpositd MWNTs using natural prcursors. EXPERIMENTAL RESULTS Synthsiz of Multiwalld Carbon Nanotubs Th synthsis was carrid out using a st up similar to Afr t al. [4]. Dsird amounts of F/Co/Mo supportd with silica catalyst ar prpard. Th catalyst on a quartz boat was placd in a quartz tub insid an lctric furnac. Bfor switching on th furnac, nitrogn gas was purgd for a fw minuts for th complt rmoval of air from th raction chambr.th furnac was switchd on and hatd to th raction tmpratur C. Synthsis was conductd at C, with a typical raction tim of 30 min. Th carrir gas N 2 was flushd for 0 minuts bfor switch on th raction furnac to rmov th insid air and crat N 2 atmosphr. Th raction furnac was switchd on to rach st tmpratur, whn th furnac attaind th dsird tmpratur th N 2 gas flow was incrasd 00ml pr min. Thn Cymbopogn flxuous oil and Glycin max oil wr supplid at a rat of 0.g/min. Aftr dposition th furnac was switchd off and allowd to cool down to room tmpratur. Aftr cooling, th sampls wr collctd. Th grown carbon nanotubs wr charactrizd by SEM, HRTEM and Raman spctroscopy. Final products obtaind in ach cas wr stord sparatly in vacuum dsiccators until usd. Th rsulting carbons namd as CF-MWNT and GM-MWNT. Nitrogn Adsorption Studis Th N 2 adsorption-dsorption isothrms of MWNTs wr masurd at 77K using a gas sorption analyzr (NOVA 000,Quanta Chrom corporation) in ordr to dtrmin th surfac aras and th total por volums[]. Th surfac aras wr calculatd using th BET quation. Surfac ara of ach MWNT was found to b 468 m 2 /g and 452 m 2 /g rspctivly. Adsorption Dynamics Th study of adsorption dynamics dscribs th solut uptak rat and vidntly this rat controls th rsidnc tim of adsorb at uptak at th solid-solution intrfac. Th ISSN(Onlin) : Vol. 3, Spcial Issu 28, Fbruary 207

3 kintics of Basic Brown 4 adsorption on th MWNTs was analyzd using psudo first ordr [5] and psudo scond ordr [6, 7] kintic modls. Th conformity btwn xprimntal data and th modl prdictd valus was xprssd by th corrlation cofficints (r 2 valus closr or qual to ). A rlativly high r 2 valu indicats that th modl succssfully dscribs th kintics of Basic Brown 4 adsorption. Th psudo First-ordr Equation Th psudo first - ordr quation [5] is gnrally xprssd as follows. dqt dt k ( q q ) t Whr, q and q t ar th adsorption capacity at quilibrium and at tim t., rspctivly (mgg - ), k is th rat constant of psudo first-ordr adsorption (min -). Aftr intgration and applying boundary conditions t =0 to t = t and q t = 0 to q t = q t, th intgration form of quation () bcoms. log( q log( q ) k qt ) t Th valu of log (q q t ) wr linarly corrlatd with t. Th plot of log (q q t ) Vs t should giv a linar rlation ship from which k and q can b dtrmind from th slop and intrcpt of th plot, rspctivly. Th Psudo scond-ordr Equation. Th psudo scond ordr adsorption kintic rat quation [6] is xprssd as dq (3) t 2 k2 ( q qt ) dt Whr, k 2 is th rat constant of psudo scond ordr adsorption (g. mg -. min - ). For th boundary conditions t = 0 to t = t and q t = 0 to q t = q t, th intgratd form of quation (3) bcoms. q q t q k t (4) Which is th intgratd rat law for psudo scond ordr raction. Equation (4) can b rarrangd to obtain quation (5), which has a linar form. t ( t) 2 qt k 2q q (5) If th initial adsorption rat h (mg g - min - ) is () (2) ISSN(Onlin) : Vol. 3, Spcial Issu 28, Fbruary 207

4 h k q 2 2 (6) thn Equations (5) and (6) bcom: t q t h q t (7) Th plot of (t/q t ) and t of quation (7) should giv a linar rlationship from which q and k 2 can b dtrmind from th slop and intrcpt of th plot, rspctivly. RESULTS AND DISCUSSION Th morphology and orintation of CNT can b asily rvald using Scanning lctron microscops. Tranmission Elctron Microscpy is th powrful instrumnt that rvals th diamtr of CNT and numbr of walls. Fig, 2 shows th SEM and TEM imags of as grown nanotub from Cymbopogn flxuous oil and Glycin max oil rspctivly. Raman Spctroscopy is commonly mployd to study th quality of th carbon nanotubs. Fig 3 rprsnts th Raman spctra of our nanotub sampls. Th Sharp G-band pak and th D band pak for th Multiwalld carbon nano tubs from Cymbopogn flxuous oil and Glycin max oil rspctivly. G pak is assignd to E 2g mod of graphit lattic and D pak, du to th structural dfcts corrsponds to an A g mod. [7, 8]. Ratios of th D pak to th G pak hav bn usd as an indicator of th amount of disordr with nanotubs. Fig. a. SEM imag of MWNT from Cymbopogn flxuous oil Fig. b. SEM imag of MWNT from Glycin max oil ISSN(Onlin) : Vol. 3, Spcial Issu 28, Fbruary 207

5 Fig. 2a. TEM imag of MWNT from Cymbopogn flxuous oil Fig. 2b. TEM imag of MWNT from Glycin max oil Intnsity (a.u) Raman shift (cm - ) Fig 3. Raman spctra of as grown MWNTs from Cymbopogn flxuous and Glycin max ISSN(Onlin) : Vol. 3, Spcial Issu 28, Fbruary 207

6 ADSORPTION STUDIES Th adsorption procss for th chosn adsorbnt-adsorbat systm wr invstigatd at tmpratur ranging from 30 to 60 ºC for ach CF-MWNT and GM- MWNT. An analysis of th data rvals that th influnc of tmpratur of th Basic Brown 4 has vry littl influnc on th first ordr rat constants. Th tabl also rvals that th influnc of th tmpratur of Basic Brown 4 on psudo-scond ordr rat constant is nithr apprciabl nor littl. Tabl. Th Adsorption Kintic Modl Rat Constants for CF-MWNT and PP- MWNT Adsorbnt Initial Tmpratur Psudo first ordr k min - r 2 Psudo Scond ordr k 2 g mg - min - h mg g - min - 2 r CF-MWNT PP-MWNT It is obvious that th adsorption of Basic Brown 4 on th MWNTs is bst dscribd by psudo scond ordr rat quation with rgrssion cofficint valu is gratr than ISSN(Onlin) : Vol. 3, Spcial Issu 28, Fbruary 207

7 ADSORPTION ISOTHERM: Th Frundlich and th Langmuir adsorption isothrms for ach procss wr studid. Th xprimntal valu of th Longmuir constants wr quatd at tmpratur of 30, 45 and 60 0 C using th wll known linar form of Langmuir s adsorption isothrm quation, q Q0 bq0c (8) whr, q is th amount of Basic Brown 4 adsorbd i.. is quilibrium concntration of Basic Brown 4 and Q o and b ar th Langmuir constants rlatd to th maximum adsorption capacity and nrgy of adsorption, rspctivly. Rsults show that th valu of Q o incrass with incras in tmpratur and accounts for th ndothrmic natur of th on going procss. It is intrsting to not that both th adsorbnt xhibit similar adsorption bhavior towards th Basic Brown 4.Th adsorption data of Basic Brown 4 wr also analyzd by th Frundlich modl, givn by th quation. logq log K F logc n Whr, q is th amount adsorbd (mg g - ), C is th quilibrium concntration of th adsorb at (M), and K F and n ar th Frundlich constant rlatd to adsorption capacity and adsorption intnsity rspctivly. Whn log q is plottd against log C, a straight lin with slop /n obtaind which clarly spcifis that th adsorption of Basic Brown 4 ovr both CF-MWNT and GM- MWNT follows th Frundlich isothrm. From ths plots th Frundlich constant K F and n ar calculatd and th valus of thss at diffrnt tmpraturs ar also prsntd in Tabl 2. Th profil prsntd in th tabls clarly indicats that for both th adsorption procss, adsorption capacity (K F ) incrass with incrasing tmpratur. (9) ISSN(Onlin) : Vol. 3, Spcial Issu 28, Fbruary 207

8 Tabl 2. Frundlich and Langmuir constants of Basic Brown 4 Langmuir constants Frundlich constants Adsorb nt Q 0, mg/g b, L/mg n K F, mg g C 45 0 C 60 0 C 30 0 C 45 0 C 60 0 C 30 0 C 45 0 C 60 0 C 30 0 C 45 0 C 60 0 C CF- MWNT GM- MWNT X X X X X X0-5 CONCLUSION W hav dvlopd a simpl and rproducibl way of synthsizing a MWNT by CVD using botanical hydrocarbons. Th high slctivity and quality of synthsizd MWNTs has bn confirmd by SEM and Raman analysis. Th N 2 adsorption is usd to dtrmin th surfac ara by using BET quation. Rmoval of Basic Brown 4 from aquous solution was possibl using as grown MWNTs. Th adsorption of Basic Brown 4 was found to b dpndnt on tmpratur, and concntration for both adsorbnts. Th prcntag saturation was found to b almost 98 and 96% for th CF-MWNT and GM- MWNT rspctivly. Th kintics of Basic Brown 4 adsorption on diffrnt MWNT basd adsorbnts was found to follow a psudo scond-ordr rat quation. ACKNOWLEDGEMENT W ar gratful to our principal, Vivkananda Collg of nginring for womn for his valuabl supports and ncouragmnts. Rfrnc. S.Iijima, Natur 354(99) 56. ISSN(Onlin) : Vol. 3, Spcial Issu 28, Fbruary 207

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