Adsorption of o-cresol Using Activated Carbon

Transcription

1 2012 Intrnational Confrnc on Clan and Grn Enrgy IPCBEE vol.27 (2012) (2012) IACSIT Prss, Singapor Adsorption of o-crsol Using Activatd Carbon Shabiimam M. A. 1 and Anil Kumar Dikshit 2,3,4 + 1,2 Cntr for Environmntal Scinc and Enginring, IIT Bombay, Mumbai, India 3 Nanyang Tchnological Univrsity, Singapor Univrsity of KwaZulu-Natal, Duban, South Africa Abstract. Commrcial activatd carbon was usd for th adsorptiv rmoval of o-crsol from dilut aquous solutions. Batch mod adsorption studis wr prformd by varying paramtrs such as ph, adsorbnt dosag and tim. Th xprimntal study show that adsorption with activatd carbon can rmov up to 95% of o-crsol from th wastwatr within 10 minuts. Th optimum procss variabls of this adsorption of o-crsol wr found as ph 8 and adsorption dosag 5 g/l. Th adsorption followd Langmuir Isothrm. Kywords: o-crsol, adsorption, activatd carbon, Frundlich isothrm, Langmuir isothrm 1. Introduction Th worldwid production volum of o-crsol is approximatly tons/annum [1]. It is mostly usd as an intrmdiat for th production of psticids, poxy rsins, dys and pharmacuticals, but also as a componnt of disinfctants and claning agnts. Approximatly 60% of o-crsol is drivd from coal tar and crud oil using classical tchniqus such as distillation, stripping, liquid-liquid xtraction. Rmaining amount is obtaind synthtically by alkylation of phnol with mthanol, ithr in th vapour or liquid phas. Most halth xposurs of o-crsol obsrvd in popl, includ irritation and burning of skin, ys, mouth, and throat, abdominal pain and vomiting, hart damag, anmia, livr and kidny damag facial paralysis, coma, and dath [2]. 2. Matrials and Mthods 2.1. Chmicals All chmicals usd in th prsnt study wr of analytical grad (A.R.), and purchasd from Mrck chmicals, Mumbai, India. Powdrd activatd carbon (having mthyln blu ratd adsorption capacity as gratr than 180 mg/g) was also procurd from Mrck Chmicals and was usd as an adsorbnt in this study Analytical Mthods ph of th wastwatr was masurd by a digital ph mtr (Polmon, LP-1395, India). COD was dtrmind by th standard closd rflux mthod using a COD ractor (Hach, DRB200 COD ractor, USA) [3]. TOC was masurd using a TOC analyzr (Shimadzu, TOC-VCSH, Japan) Estimation of o-crsol o-crsol was stimatd using spctro-photomtric mthod as proposd by APHA (2005) [3]. o-crsol was rapidly condnsd with 4-Aminoantipyridin followd by its oxidation with potassium frricyanid at ph 7.9 to yild rd colourd compound. Th absorbanc was masurd at 510 nm using UV-Visibl spctrophotomtr (Thrmolctron Corporation, GENESYS 20, USA). + Corrsponding author. Tl.: + (91) ; fax: + (91) addrss: dikshit@iitb.ac.in. 88

2 2.4. ph Study Th optimum ph for th procss was dtrmind from th data obtaind from xprimnts carrid out at varying initial ph (2, 4, 6, 8, 10 and 12) and all subsqunt xprimnts wr carrid out at this ph Dosag Study Adsorbnt dosag was optimizd by prforming th xprimnts at varying adsorbnt dosag (2, 3, 4, 5, 6 and 7 g/l) at optimum ph. Aliquots of th sampl wr collctd at spcifid tim intrvals (10, 20, 30, 40 min) and analyzd by TOC and o-crsol by spctrophotomtric mthod. Th data obtaind wr usd to plot isothrms which dscrib th adsorption procss Batch Adsorption Study As mntiond arlir o-crsol (500 mg/l, TOC 417 mg/l) was usd as th modl compound for adsorption studis. All th adsorption xprimnts wr don in 100 ml glass-stopprd bottls containing pr-dtrmind amount of activatd carbon as adsorbnt with 50 ml of synthtic wastwatr. Th flasks wr labld and kpt in an orbital shakr (Trishul quipmnts, Than) at a spd 120 rpm for 60 minuts. Batch xprimnts wr carrid out to valuat th ffct of th following paramtrs on th rmoval of o- crsol from th wastwatr: ph, adsorbnt dos and tim. To valuat th fficincy of adsorption, o-crsol and TOC of th wastwatr bfor and aftr th tratmnt wr dtrmind. All th runs wr carrid out in duplicat to confirm th rsults. 3. Rsult and Discussion 3.1. Charactristics of o-crsol Th charactristics of o-crsol ar shown in Tabl 1. Initial ph is 6.8 and 417 mg/l of TOC. Tabl 1: Charactristics of o-crsol. Paramtr Unit Valu ph COD mg/l 1655 TOC mg/l 417 Mlting-point o C 31 Boiling-point o C 191 Dnsity kg/m Effct of ph on th Adsorption of o-crsol Rsults obtaind from th adsorption of o-crsol at varying initial ph valus ar prsntd in Figur 1. Powdrd activatd carbon dos was kpt 2 g/l in all th runs. It can b sn that TOC rmoval was maximum at ph 8 and showd a 65.32% rduction from th initial valu. Hnc all subsqunt xprimnts wr carrid out at this ph. Similar trnd was obtaind for th concntration of o-crsol at diffrnt ph valus (Figur 1) Effct of Adsorbnt Dos To obsrv th ffct of adsorbnt dos, th runs wr conductd at diffrnt doss (2, 3, 4, 5, 6 and 7 g/l). From Figur 2, it can b sn that TOC dcrasd rmarkably whn th adsorbnt dosag was incrasd from 2 to 3 g/l. Byond this adsorbnt dos, TOC and substrat concntration continud to dcras. But it was found that any addition of adsorbnt in th xcss of 5 g/l did not xhibit applicabl dcras (< 50% from th prvious valu). o-crsol rduction always occurrd in th sam manr as th TOC as TOC was du to o- crsol only. Hnc all subsqunt xprimnts wr carrid out using this dos. 89

3 (a) Fig. 1: Effct of ph on th adsorption of o-crsol. Exprimntal conditions: activatd carbon usd = 2 g/l; initial concntration of o-crsol = 500 mg/l, initial TOC = 417 mg/l. (a) Fig. 2: Effct of adsorbnt dos on th adsorption of o-crsol. Exprimntal conditions: xprimntal ph = 8; initial concntration of o-crsol = 500 mg/l; initial TOC = 417 mg/l Effct of Raction Tim Th ffct of raction tim on th ovrall o-crsol rmovd was studid by withdrawal of sampls at an intrval of 10 minuts. Th total duration of th runs was 40 minuts. Th adsorbnt was takn 5 g/l and th solution ph was kpt at 8.0. Th rsults ar plottd in Figur 3. It can b sn that 95% rmoval of TOC occurrd in 40 minuts. Howvr, most of th rmoval was achivd within 10 minuts. Fig. 3: Effct of tim on th adsorption of o-crsol. Exprimntal conditions: activatd carbon usd = 5 g/l; ph maintaind = 8; initial concntration of o-crsol = 500 mg/l. 90

4 q (mg/g) C (mg/l) Fig. 4: Adsorption isothrm plot for o-crsol on activatd carbon Langmuir Isothrm Th rsults obtaind for th xprimntal studis, shown in Figur 4, wr fittd in th quation prscribd for Langmuir isothrm [2, 4]: q = K LC /( 1+ bc ) = qmbc /(1 + bc ) (1) whr q is th adsorption capacity (mg/g), C is quilibrium concntration of adsorbat (mg/l), K L and b ar Langmuir constants, and q m is th Langmuir monolayr adsorption capacity Frundlich Isothrm Th rsults obtaind for th xprimntal studis wr fittd in th quation prscribd for Frundlich isothrm [1, 5]: F ( 1/ n) q = K C (2) whr q is adsorption capacity (mg/g), C is quilibrium concntration of adsorbat (mg/l), and K F and n ar Frundlich constants. (a) Fig. 5: Langmuir (a) and Frundlich isothrms for adsorption of o-crsol on activatd carbon. Th quilibrium adsorption data obtaind wr thn fittd to Langmuir and Frundlich isothrms. Figur 5 shows th langmuir and Frundlich Isothrm plots and Tabl 2 shows th paramtr for both th modls. Tabl 2: Isothrm paramtrs for th adsorption of o-crsol on activatd carbon Modl K L Q max b R 2 Langmuir

5 4. Conclusion Modl K f 1/n n R 2 Frundlich Th prsnt study provd that th commrcial activatd carbon can rmov up to 95% of o-crsol from th wastwatr within 10 minuts by adsorption tchniqu. Th rsults wr fittd with Langmuir Isothrm. Th optimum procss variabls of this adsorption of o-crsol wr found as ph of 8 at an adsorbnt dosag of 5 g/l. 5. Rfrncs [1] A. D. Vasu. Rmoval of phnol and o-crsol by adsorption onto activatd carbon. E-Journal of Chmistry 2008, 5 (2): [2] H. I. Maarof, B. H. Hamd, and A. L. Ahmad. Adsorption Isothrm of o-crsol from Aquous Solution by Granular Activatd Carbon. Proc. Intrnational Confrnc on Chmical and Bioprocss Enginring. Univrsiti Malaysia Sabah, 2003, pp [3] Amrican Public Halth Association (APHA). Standard Mthods for th Examination of Watr and Wastwatr, 21st d., APHA, Washington, DC, [4] S. Juang, F. C. Wu, and R. L. Tsng, Adsorption isothrms of phnolic compounds from aquous solutions onto activatd carbon fibrs. Journal of Chmical & Enginring Data 1996, 41 (3): [5] Y. Foo, and B. H. Hamd. Insights into th modling of adsorption isothrm systms. Chmical Enginring Journal 2010, 156 (1):