Adsorption Chemistry of Oil-in-Water Emulsion from Spent Oil Based Cutting Fluids Using Sawdust of Mangifera indica

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1 J. Int. Environmntal Application & Scinc, Vol. 4 (1): (2009) Adsorption Chmistry of Oil-in-Watr Emulsion from Spnt Oil Basd Cutting Fluids Using Sawdust of Mangifra indica Sandp Tiwari 1,*, Vimal K. Gupta 2, P.C. Pandy 3, H. Singh 4, P.K.Mishra 5 1 Mchanical Enginring Dpartmnt, GLA Institut of Tchnology & Managmnt, Mathura, India, 2 Mchanical Enginring Dpartmnt, GLAITM, Mathura, India, 3 Mchanical Enginring Dpartmnt, IIT, Roork India, 4 Mchanical Enginring Dpartmnt, KNIT, Sultanpur India, 5 Mchanical Enginring Dpartmnt, IT BHU, Varanasi, India Rcivd July 24, 2008; Accptd Novmbr19, 2008 Abstract: Frundlich and Langmuir thoris of surfac chmistry for th adsorption of mulsifid oil from spnt cutting fluid gnratd by th us of smi-synthtic mtal working fluid in mtal machining oprations using sawdust of Mangifra indica through batch adsorption study undr optimizd adsorptiv prtinnt factors wr studid in th prsnt rsarch work. Adsorption of mulsifid oil was favourd at low ph with maximum rmoval at ph=3 and tmpratur of 25 0 C. Mathmatical adsorption isothrms wr prdictd using linarizd plots of adsorbd oil pr unit wight of sawdust vrsus quilibrium oil-in-watr concntration. Ths prdictd isothrm modl wr compard with th Frundlich and Langmuir modls. Numrical analysis has bn usd to calculat corrlation cofficint of xprimntal obsrvd adsorbd oil with prdictd modls. Rsults of prsnt study for Frundlich and Langmuir kintics for adsorption show th applicability of ths thoris for th adsorption of mulsifid oil from smi-synthtic mtal working fluid. Ky words: Adsorption, Frundlich Isothrms, Langmuir Isothrms, Smi-synthtic Mtal Working Fluid Symbols C 0 Initial oil concntration, mg L -1 C Adsorbat quilibrium oil concntration, mg L -1 C t Oil concntration at tim of t, mg L -1 k Frundlich Constant (i.. Adsorption Capacity) k 1 Langmuir Empirical Constant (i.. Equilibrium constant), L (mg) -1 k 2 Langmuir Empirical Constant (i.. Adsorption Capacity), mg (gm) -1 m s Wight of adsorbnt, gm. n Frundlich Constant (i.. Adsorption Intnsity) Oil rmovd pr unit wight of adsorbnt, mg (gm) -1 t Adsorbd oil pr unit wight of adsorbnt at tim t, mg (gm) -1 V volum of th SCF, L Introduction Mtal Working Fluids (MWF) hav found xtnsiv applications in mtal working industris to improv th friction conditions btwn th tool and work and carry away th hat gnratd du to mtal machining (McCoy, 1994). This has also bn found to improv th tool lif, work surfac finish and mtal rmoval rat. In addition, thy hlp to carry th swart away from th working ara and protct th nwly formd surfac. MWF ar complx mixtur that may contain ptrolum products, vgtabl and animal fats, organic/inorganic salts and wid varity of additivs. MWF can groupd into four major catgoris: straight MWF, which ar undilutd minral and fatty oils; solubl MWF, which ar watr mulsions of minral and fatty oils; synthtic MWF, which ar chmical solutions of organic compounds and inorganic salts in watr; and smi-synthtic MWF, which ar mulsions of minral oils with watr and th chmicals found in synthtics (NIOSH, 1998). Onc MWF has bn usd for a priod, its dgradation with tim is unavoidabl and it gnrats toxic liquid wast known as Spnt Cutting Fluid (SCF). Du to incrasing concrn for nvironmntal protction, it has now bcom mandatory to procss th SCF bfor thy can b disposd off into th nvironmnt safly. * Corrsponding: E mail: sandp_tiwari1970@rdiffmail.com, Tl: , Fax:

2 J. Int. Environmntal Application & Scinc, Vol. 4 (1): (2009) Till dat, wid rang of approachs through rsarchs for th rmoval of mulsifid oil from SCF gnratd by th us of smi-synthtic MWF ar in xistnc and frquntly usd in industrial wastwatr tratmnt plants. Ths includ physical and chmical prcipitation through sttlings, cntrifugation, pasturization, skimmrs, ultra-filtration, coalscnc, straining, dp bd filtration, ion xchang, rvrs osmosis, nano-filtration, coaxial micro-filtration tc (Bnito & Ruiz, 2002; Mathavan & Viraraghavan 1992; Rngaraj t al., 2001; Solisio t al., 2002; Viraraghavant & Mathavan, 1990; Yurlova t al., 2002). Adsorption phnomnon is bing usd worldwid by th nvironmntal nginrs to sparat many organic/inorganic compounds from industrial wastwatr. But, in cas of SCF, it is rarly usd in any industrial tratmnt plants to sparat mulsifid oil. In th prsnt study, innovativ work has bn don for th study of adsorption kintics of mulsifid oil from SCF. For this purpos, batch adsorption study was conductd using sawdust of Mangifra indica in th form of USMI and TSMI as th adsorbnt. Applicability of Frundlich and Langmuir thoris for oil adsorption has bn analyzd using th xprimntal rsults of batch adsorption study. Matrial and Mthods Adsorbnt Prparation Sawdust of Mangifra indica (i.. Mango tr) found in th country rgion of India was usd as an adsorbnt for th study of adsorption kintics of mulsifid oil from SCF. Collctd sawdust from timbr working shop situatd nar agricultur land aras was washd to clan th adhring dirt, rinsd thoroughly with doubl distilld watr and finally hatd in ovn at 105 o C for 24 hrs. Aftr drying, it was ground to a fin powdr and to mak homognous it was sivd through 177 μm and rtaind part of sawdust on 100 μm siv was usd as adsorbnt and namd as Unmodifid Sawdust of Mangifra Indica (USMI). Activation of Adsorbnt To rmov any dbris or solubl bio-molculs which may b intractd with mtal ion during sorption, drid form of sawdust rtaind on 100 μm siv was furthr tratd with highly concntratd H 2 SO 4 in th ratio of 1:1 (w/v ratio i.. on mg of sawdust with on ml of acid) in a muffl furnac for 24 hrs at 150 o C. Th hatd matrial was washd with doubl distilld watr and soakd in 1% sodium bicarbonat solution ovrnight to rmov rsidual acid. Th matrial was drid in an ovn at 105 o C for 24 hrs. Aftr that it was groundd and homognizd by passing it with siv of 177 μm and rtaind part on 100μm siv was usd as chmically modifid activatd carbon and namd as Tratd Sawdust of Mangifra indica (TSMI). All adsorbnts wr drid at 105 o C ovrnight bfor any adsorption xprimnts. Adsorbat Solution Th mtalworking fluid usd in this work is Hysol G, SDS # 7040, a smi-synthtic oil prpard by Castrol Limitd which givs a micro-mulsion whn mixd with watr. Liquid wast in th form of mulsifid oil gnratd aftr th us of Hysol G in mtal working oprations as spnt cutting fluid was collctd from M/s Timkn India Limitd, Tata Nagar, India. Adsorbat solution sampls wr prpard in th proportion of 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5% and 6.0% (v/v ratio) of mulsifid oil for th batch adsorption study. Analysis of Oil-in-watr Emulsion Th concntrations of oil in th aquous solution wr masurd by hand rfractomtr. In rfractomtr, principl of rfraction of light is usd and by mans of xtrnal light intrfrnc rfractiv indx of sampl is masurd which givs th concntration of oil. It is basd on th phnomna that as dnsity of a substanc (i.. concntration) incrass its rfractiv indx riss in proportionat mannr (Hilal t al., 2004). Batch Adsorption Studis Batch adsorption xprimnts to study th adsorption kintics of mulsifid oil through adsorbnt of USMI and TSMI wr conductd. Concntration of adsorbat solution sampls wr 100

3 J. Int. Environmntal Application & Scinc, Vol. 4 (1): (2009) takn in th proportion of 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5% and 6.0%. Exprimnts wr carrid out by adding 25 gm of adsorbnt in on littr of ach proportion of SCF. uantity of 50 ml from ach proportion was takn for th batch adsorption study. Adjustmnt of ph was carrid out using 0.1 N NaOH and/or 0.1 N H 2 SO 4. Agitation of th systm undr invstigations was carrid out on orbital thrmal shakr. To maximiz mulsifid oil rmoval by th adsorbnts, batch xprimnts wr conductd at ambint tmpratur (i C) using th optimum conditions of all prtinnt factors such as adsorbnt dos, ph, agitation spd, contact tim (Chakravarty t al., 2002). Subsqunt adsorption xprimnts wr carrid out with only optimizd paramtrs. Adsorption isothrms wr carrid out in th raction mixtur consisting of 25 gm (L) -1 of adsorbnt and 50 ml of mulsifid oil of SCF solution with varying initial oil concntration from 12.3 mg (L) -1 to 49.2 mg (L) -1. Th chang in oil concntration du to adsorption was dtrmind using hand rfractomtr. Th amount of mulsifid oil adsorbd pr unit wight of adsorbnt was computd by th following mass balanc quation; t ( C C ) o t V = (1) m s Whr t is th wight of oil rmovd from SCF pr unit wight of adsorbnt in mg(gm) -1, C 0 and C t ar th concntration of oil initially and at givn tim t, rspctivly in mg(l) -1, V is th volum of th SCF in littr and m s is th wight of adsorbnt (i.. sawdust) in gm. Prcntag rmoval of oil (R %) in solution was calculatd using following quation; R ( ) ( Co Ct ) 100 % = x (2) C o To nsur th accuracy, rliability, and rproducibility of th collctd data, all th batch xprimnts wr carrid out in duplicat and th man valus of two data sts ar prsntd. Whn th rlativ rror xcdd th rlativ standard dviation by mor than 1.0%, th data wr disrgardd and a third xprimnt was conductd until th rlativ rror fll within th accptabl rang. Numrical Analysis Adsorption kintics of mulsifid oil has bn assssd by minimizing th sum of squar of rrors btwn th xprimntal obsrvd data and th prdictd isothrm modls with th application of linar last squar rgrssion mthod (Btha, t al., 1985). Rsult and Discussion Adsorption Equilibrium Isothrms Th physical chmistry involvd for adsorption is complx phnomna and no singl thory of adsorption till dat has bn put forward to xplain all th adsorptiv principls of adsorption systms. Adsorption isothrms ar dscribd in many mathmatical forms, som of which ar basd on a simplifid physical pictur of adsorption and dsorption, whil othrs ar intndd to corrlat th xprimntal data in simpl quations with svral mpirical paramtrs (Chakraborty t al., 2005). In th prsnt study, Frundlich and Langmuir thory of surfac chmistry for adsorption at solid-liquid intrfac has bn usd to study of adsorption kintics of mulsifid oil. Rsults of batch adsorption for adsorbd oil pr unit wight of adsorbnts vrsus quilibrium solut concntration hav bn plottd in Fig 1. Numrical analyss hav bn usd to prdict mathmatical Frundlich and Langmuir Modls. Prdictd mathmatical modls hav also bn plottd in Figur 1. Frundlich Isothrm Modl Hrbrt Max Finly Frundlich, a Grman physical chmist, prsntd an mpirical adsorption isothrm for non-idal sorption on htrognous surfacs as wll as multilayr sorption. Htrognity of th surfac and th xponntial distribution of adsorbnt and thir nrgis can b dfind by th by Frundlich isothrm (Frundlich, 1906). Eq. 3 rprsnt Frundlich adsorption 101

4 J. Int. Environmntal Application & Scinc, Vol. 4 (1): (2009) isothrm to xplain th variation of adsorption with concntration ovr a limitd rang at constant tmpratur. f 1 n = k C (3) Figur 1: Exprimntally obsrvd isothrms and prdictd isothrms by Frundlich and Langmuir Modl I & II for both adsorbnts. Isothrms ar plottd btwn adsorbd mulsifid oil pr unit wight of adsorbnt in mg gm -1 vrsus quilibrium concntration of solut in mg L -1. Exprimntal Paramtrs, Initial Oil Concntration: from 12.3 mg L -1 to 49.2 mg L -1, Adsorbnt dos: 25 gm L -1, ph =3, Tmpratur: 25 0 C, Agitation spd: 150 rpm and Particl Siz: μm. Whr is th oil rmovd pr unit wight of adsorbnt in mg (gm) -1, C is th adsorbat quilibrium oil concntration in mg (L) -1, k f and n ar Frundlich constants. On linarization, Eq. 3 can b writtn by Eq. 4 and known as linarisd Frundlich isothrm modl. 1 Ln ( ) = Ln( k f ) + Ln( C ) (4) n Logarithmic plot of and C obtaind from batch study has bn plottd in Figur 2. Batch adsorption xprimntal data wr obsrvd at th optimizd conditions of all prtinnt factors such as ph, adsorbnt particl siz, dos, tmpratur and agitation spd at initial oil concntration from 12.3 mg L -1 to 49.2 mg L -1. Figur 2 givs straight lin having corrlation cofficint of and for adsorbnts of USMI and TSMI, rspctivly, indicating th applicability of Frundlich thory for th adsorption kintics of mulsifid oil from SCF. Adsorption kintics has bn analyzd with th hlp of numrical analysis of obsrvd xprimntal data. Adsorption intnsity and adsorption capacity has bn dtrmind for both adsorbnts and ar rportd in Tabl 1. Mathmatically, prdictd Frundlich isothrm quations for both adsorbnt can b writtn by Equation 5 & For UMSI; = 0.136C (5) For TMSI; C = (6) 102

5 J. Int. Environmntal Application & Scinc, Vol. 4 (1): (2009) Figur 2: Linarisd Frundlich isothrms of USMI & TSMI. Isothrms ar plottd in adsorbd mulsifid oil from SCF pr unit wight of adsorbnt in mg.gm -1 and quilibrium concntration of solut in mg.l -1. Exprimntal Paramtrs, Initial Oil Concntration: from 12.3 mg.l -1 to 49.2 mg.l -1, Adsorbnt dos: 25 gm.l -1, ph =3, Tmpratur: 25 0 C, Agitation spd: 150 rpm and Particl Siz: μm. Tabl 1: Adsorptiv paramtric constants for Frundlich Modl Adsorptiv Paramtr Frundlich USMI TMSI Adsorption Intnsity, n a b Adsorption Capacity, k f Corrlation Cofficints a It is Frundlich constant known as adsorption capacity, which is dimnsionlss constant. b It is Frundlich constant known as adsorption intnsity. It givs an indication of th favourability of adsorption. Valu of constant, n: 2-10, rprsnt good; 1-2, rprsnt favorabl; and n <1 shows poor adsorption charactristics (Raji & Anirudhan, 1997, Rao & Bhol, 2001). It is dpndnt upon th 1 (1 n) 1 n 1 adsorption capacity of adsorbnt. It is rprsntd by mg L gm. Langmuir Isothrm Modl Irving Langmuir pointd th inhrnt assumption of surfac chmistry for adsorption thory. According to this assumption, rapid falling of intrmolcular forcs with distanc is du to singl molcul adsorbd thicknss of layr, which is mainly bcaus of availability of fixd localizd surfac sits prsnt on th homognous surfac of adsorbnt molcul (Langmuir, 1918). This viw is widly accptd for adsorption at low prssur or at modratly high tmpratur. On th basis of abov principl, Langmuir has dvlopd following quation, known as Langmuir isothrm. k k C 1 2 = (7) 1+ k1c Whr is th amount of oil adsorbd pr unit wight of adsorbnt to from a complt monolayr on th surfac in mg (gm) -1, C, is th oil concntration at quilibrium in mg (L) -1, k 1 and k 2 ar Langmuir mpirical constants. 103

6 J. Int. Environmntal Application & Scinc, Vol. 4 (1): (2009) Langmuir Isothrm Modl: I According to linarization by Stumm & Morgan, 1981, Eq.7 can b rprsntd by Eq. 8 and it is known as linarisd Langmuir Isothrm Modl I = + k2 k1k2 C Langmuir Isothrm Modl: II (8) Similarly, linarization according to Wbr (1972), Eq. 7 can b rprsntd by Eq. 9 and it is known as linarisd Langmuir Isothrm Modl II. C 1 1 = + ( C ) (9) k k k Rsults obtaind from batch study at optimizd prtinnt adsorptiv factors and initial concntration from 12.3 mg (L) -1 to 49.2 mg (L) -1 ar plottd in C / vrsus C and 1/ vrsus 1/C as shown in Fig 3. Both plots shown in th Fig 3 giv straight lins indicating applicability of Langmuir thory for oil adsorption. Numrical analysis has bn usd for linarisd isothrm of Langmuir Modl I & II and mathmatical isothrms as shown in quation from 10 to 13 ar prdictd. Adsorption Langmuir constants in trms of quilibrium constant and adsorption capacity ar dtrmind and ar rportd in Tabl 2. Tabl 2: Adsorptiv paramtric constants for Langmuir Modl I & II Langmuir Modls Modl: I Modl: II Adsorptiv Paramtr USMI TSMI USMI TSMI Equilibrium constant, c k 1 [L (mg) -1 ] d 353 d 91 d 338 d Adsorption Capacity, k 2 [mg (gm) -1 ] c It is Langmuir mpirical constant, which is basd on th typ of analysis. In cas of thrmodynamic quilibrium, it is affinity paramtrs, similarly for mass transfr balanc, it is affinity paramtr. It is tmpratur dpndnt and rlatd to th Gibbs fr nrgy and hnc it shows th chang in nthalpy. d If initial concntration of solut is takn in mg.ml -1. For Langmuir Modl I For USMI; For TMSI; C = (10) C 0.61 C = (11) C For Langmuir Modl II For USMI; C = (12) C 104

7 J. Int. Environmntal Application & Scinc, Vol. 4 (1): (2009) For TMSI; C = (13) C Figur 3: Linarisd isothrms of Langmuir Modl I & II for both adsorbnts. For Langmuir modl I, graph is plottd btwn 1/ vrsus 1/C and similarly for Langmuir modl I, It is plottd in C / vrsus C. Exprimntal Paramtrs for both plots; Initial Oil Concntration: from 12.3 mg L -1 to 49.2 mg L -1, Adsorbnt dos: 25 gm L -1, ph =3, Tmpratur: 25 0 C, Agitation spd: 150 rpm and Particl Siz: μm. Validation of Adsorption Modls Rsults of th batch adsorption study and graph plottd on Figur 4 indicat vry littl variation in prdictd data from obsrvd xprimntal data. Corrlation cofficint of xprimntal data and prdictd rsults of Frundlich and Langmuir Modl I & II for oil adsorption ar tabulatd in Tabl 3. Tabl 3: Corrlation Cofficints for Exprimntal and Obsrvd Data Corrlation Cofficints Adsorption Modls USMI TSMI Frundlich Langmuir Modl I Langmuir Modl II

8 J. Int. Environmntal Application & Scinc, Vol. 4 (1): (2009) Figur 4: Validation of Frundlich Modl, Langmuir Modls I & II. Exprimntally obsrvd adsorbd mulsifid oil pr unit wight of adsorbnts in mg.gm -1 vrsus initial concntration in mg.l -1 of oil has bn plottd for TSMI and USMI at Initial Oil Concntration: from 12.3 mg.l -1 to 49.2 mg L -1, Adsorbnt dos: 25 gm L -1, ph = 3, Tmpratur: 25 0 C, Agitation spd: 150 rpm and Particl Siz: μm. Conclusion Adsorption rsults of batch study and numrical analysis of xprimntal data show littl variation in th prdictd rsults of Frundlich and Langmuir thory of adsorption for mulsifid oil rmoval. Corrlation cofficint for both modls ar approaching towards unity indicat th applicability of Frundlich and Langmuir thory for th oil adsorption through sawdust of mangifra indica. Rfrncs Bnito Y, Ruiz ML, (2002) Rvrs osmosis applid to mtal finishing wastwatr. Dsalination, 142, Btha RM, Duran BS, Boullion TL, (1985) Statistical Mthods for Enginrs and Scintists, Marcl Dkkr, Inc, Nw York. Chakraborty S., D S, Gupta SD, Basu JK, (2005) Adsorption study for th rmoval of a basic dy: xprimntal and modling. Chmosphr 58, Chakravarty S, Durja V, Bhattacharyya G, Maity S, Bhattacharj S, (2002) Rmoval of arsnic from groundwatr using low cost frruginous mangans or. Watr Rsarch, 36, Frundlich HMF, (1906) Ovr th adsorption in solution. Z. Phys. Chm. 57, Hilal N, Busca G, Hankins N, Mohammad AW, (2004). Th us of ultra filtration and nanofiltration mmbrans in th tratmnt of mtal working fluids. Dsalination, 167, Langmuir I, (1918) Th adsorption of gass on plan surfac of glass, mica and platinum. J. Am. Chm. Soc, 40, Mathavan GN, Viraraghavan T, (1992) Coalscnc/filtration of an oil-in-watr mulsion in a pat bd. Watr Rs. 26, McCoy JS, (1994) Introduction: Tracing th historical dvlopmnt of mtalworking fluids. In: Byrs JP (Ed.), Mtalworking fluids, Marcl Dkkr, Nw York NIOSH, (1998) Critria for a rcommndd standard: occupational xposur to mtal working fluids, US. Raji C, Anirudhan TS, (1997) Chromium (VI) adsorption by sawdust: Kintics and Equilibrium. Indian J. Chmical Tchnology, 4,

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