ADSORPTION OF DISPERSE BLUE DYE ON IRAQI DATE PALM SEEDS ACTIVATED CARBON

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1 Int. J. Chm. Sci.: 11(3), 2013, ISSN X ADSORPTION OF DISPERSE BLUE DYE ON IRAQI DATE PALM SEEDS ACTIVATED CARBON AHMED F. HALBUS, ZAHRAA H. ATHAB a and FALAH H. HUSSEIN * Chmistry Dpartmnt, Collg of Scinc, Babylon Univrsity, HILLA, IRAQ a Environmntal Rsarchs Cntr, Babylon Univrsity, HILLA, IRAQ ABSTRACT In this papr, adsorption isothrm and kintics of disprs blu dy on activatd carbon prpard from Iraqi dat sds (Zahdi dat sds ZDS) wr dtrmind from batch tsts. Th ffct of diffrnt paramtrs, such as, diffrnt doss, ph and contact tim wr invstigatd. Equilibrium adsorption data for synthsizd activatd carbon (ZDSAC) wr analyzd by Langmuir and Frundlich isothrm. Th quilibrium data wr bst fittd with Langmuir isothrm modl, showing maximum monolayr adsorption capacity of 8.13 mg/g. Kintic analyzs wr tstd using psudo-first ordr, psudo-scond ordr and th intraparticl diffusion modl. Kintic studis showd that th adsorption kintics was mor accuratly rprsntd by a psudo-scond ordr modl. Among ZDSAC rmovs 66.47% of disprs blu at th dos of 0.3 g, whras th commrcial activatd carbon rmovs 54.33% of disprss blu. Ky words: Adsorption, Dat palm sds, Activatd carbon, Disprs blu, Kintics, Isothrms. INTRODUCTION Activatd carbon is th most popular and widly usd adsorbnt in wastwatr tratmnt throughout th world. Activatd carbon is chap, asily availabl, high capacity of adsorption and surfac ractiv 1. Adsorption is an important tchnology and ffctiv mthod for purification procss of watr and wastwatr in industrial application such as odor, oil, and colors of organic pollutants. Svral rsarchrs usd th activatd carbon as an adsorbnt for watr and air purification 2. Adsorption onto activatd carbon prpard from dat palm sds has bn provn to b an ffctiv procss for disprs dy rmoval, but it is an xpnsiv procss. This has largly bn associatd with th cost of producing activatd carbon, and th lack of suitabl and inxpnsiv rgnration procdurs for ths * Author for corrspondnc; abohasan_hilla@yahoo.com

2 1220 A. F. Halbus t al.: Adsorption of Disprs Blu Dy on. adsorbnts. Th activation mthod to b proposd is important for th cost of producing activatd carbons. In this rspct, ths hav ld many rsarchrs to us low-cost plant and wood-basd matrials for activatd carbon production. Numrous low-cost plants such as pistachio shlls 3, palm krnl shll 4, coconut husk 5, bamboo wast 6, coir pith 7, ric husk 8 and oil palm shll activatd carbon 9, hav bn usd for th production of activatd carbon for th rmoval of th txtil dy fflunts. Disprs dys ar xtnsivly usd in diffrnt typs of industris, such as txtils, papr and lathr. Disprs dys ar non-ionic aromatic compounds, scarcly solubl in watr, but solubl in organic solvnt. Majority of thm ar azo and anthraquinon dys. Ths dys can b applid to synthtic fibrs such as nylon, polystr, cllulos, acrylic and actat 10,11. During dy production and txtil manufacturing procsss, a larg quantity of wastwatr containing high concntration of organic compounds difficult rmoval of ths dys du to high solubility in watr Many rsarchrs ar dvotd in rcnt yars to rmov dys from wastwatrs, using diffrnt tchniqus such as adsorption tchniqu. Adsorption rmoval is an ffctiv and simpl tchniqu for dy tratmnt, but usually producs larg amount of sludg, which may caus scondary pollution. Th individual tratmnt tchniqu is not prfct nough to rmov th dys from wastwatrs in high fficincy without producd a scondary contaminants. As a rsult combining two or mor tratmnt tchniqus such as using th adsorption with th photodgradation tchniqu is mor ffctiv to gt high rmoval of dys from wastwatr Th main objctiv of this rsarch was to valuat th ability of using activatd carbon prpard from Iraqi dat palm sds (Phonix dactylifra); as on of th most important fruit crops grown in th Iraq, by phosphoric acid activation for th adsorption of disprs dy from aquous solutions. Matrials and mthods Adsorbat EXPERIMETNAL Disprs blu 26 dy (DB26), 1, 5-Dihydroxy-4,8-bis (mthylamino) anthracn- 9,10-dion was usd as an adsorbat and was not purifid prior to us. Distilld watr was usd to prpar all th solutions and ragnts. DB26 has a chmical formula of C 16 H 14 N 2 O 4, with molcular wight of g/mol. Th chmical structur of DB26 dy is illustratd in Fig. 1.

3 Int. J. Chm. Sci.: 11(3), OH O NH-CH 3 CH 3 -HN CH 3 O OH Prparation of activatd carbon Fig. 1: Chmical structur of disprs blu Zahdi dat sds (ZDS) wr usd to prpar th activatd carbon ZDSAC. Th sds wr washd with hot distilld watr to rmov dust and othr impuritis, drid at 105 o C. 40% phosphoric acid (purity 85% Mrck, Grmany) was addd to it during th chmical activation procss. Th activation was compltd by hating at tmpratur 700 o C for 1 hour. Aftr cooling, th activatd carbon was rpatdly washd with hot distilld watr until th ph of th washing solution rachd Th product was drid at 105 o C for 2 hours and kpt in tightly closd plastic containr. Adsorption studis Th adsorption xprimnts in this work wr don for th study th ffct of xprimntal conditions on disprs blu adsorption and dtrmining th conditions that achiv th maximum rmoval of disprs blu. Th adsorption tsts wr conductd in magntic mixr. Th concntration of disprs blu was 20 ppm and th amount of adsorbnt was includd th ratio 0.1, 0.15, 0.2, 0.25, 0.3, and 0.35 g for activatd carbon. In all xprimnts, th rquird amount of th adsorbnt was suspndd in 100 cm 3 of aquous solution of disprs blu. 2 ml was takn from th raction suspnsion, cntrifugd at 6,000 rpm for 15 minuts in an 800 B cntrifug, and filtrd to rmov th particls. Th scond cntrifug was found ncssary to rmov fin particl of th activatd carbon. Aftr th scond cntrifug, th absorbanc of th disprs blu was masurd at 570 nm, using 1650 PC UV-visibl spctrophotomtr Shimadzu. Th fficincy for rmoval of disprs blu, (% Rmoval), was calculatd as follows : % Rmoval = Ci C C i f x 100 (1) whr C i is th initial concntration and C f is th final concntration. q is th amount of mtal adsorbd pr spcic amount of adsorbnt (mg/g).th sorption capacity at tim t, q t (mg/ g) was obtaind as follows:

4 1222 A. F. Halbus t al.: Adsorption of Disprs Blu Dy on. q t = (Ci C t) x V m (2) whr C i is th initial concntration of disprs blu, C t rprsnts disprs blu concntration at tim t., V was th solution volum and m th mass activatd carbon (g). Th amount of adsorption at quilibrium, (q ) was calculatd by th following quation : q = (Ci C) x V m (3) whr C was th disprs blu concntration at quilibrium. Effct of contact tim RESULTS AND DISCUSSION Fig. 2 shows th ffcts of contact tim on disprs blu dy rmoval. Rmoval prcntag was incrasd with an incras in contact tim. Adsorption was vry rapid in th first 20 min for activatd carbon, and thn it was incrasd slowly with tim until raching quilibrium. It was found that th quilibrium tim was mor than 20 min for both activatd carbons. To nsur full quilibration, a shaking tim of 60 min was usd for all concntrations of activatd carbon in this study Rmoval (%) g 0.30 g 0.25 g 0.20 g 0.15 g 0.10 g Tim (min) Fig. 2: Effct of contact tim on disprss blu dy rmoval by ZDSAC

5 Int. J. Chm. Sci.: 11(3), Comparison btwn th rmoval fficincy of ZDSAC and commrcial activatd carbon Fig. 3 rprsnts th comparison of ffct of synthsizd ZDSAC and commrcial activatd carbon on disprss blu. Fig. 3 indicats that th maximum disprs blu rmoval was found at 0.3 g of synthsizd ZDSAC i % whras 54.33% for commrcial AC. Rmoval (%) Rmoval % by 0.3 g ZDSAC (Synthsis) Rmoval % by 0.3 g AC (Commrcial) Tim (min) Fig. 3: Comparison btwn th rmoval fficincy of ZDSAC and commrcial activatd carbon Effct of activatd carbon dosag Th ffct of activatd carbon dos was studid by varying th dos btwn 0.1 g and 0.35 g in 100 ml aquous solution of disprs blu dy. Ths tsts wr conductd at a tmpratur of 25 o C, with ph 5.5 for disprs blu dy. Th initial disprs blu concntration was 20 ppm. It was obsrvd that th adsorption fficincy prcntag of disprs blu dy onto th activatd carbon incrasd rapidly with th incras of adsorbnt concntration as shown in Fig. 4. This rsult was xpctd bcaus th incras of adsorbnt dos lads to gratr surfac ara. Whn th adsorbnt concntration was incrasd from 0.1 g to 0.35 g, th prcntag of disprs blu adsorption incrasd from to at highr concntrations, howvr th quilibrium uptak of disprs blu dy did not incras significantly with incrasing activatd carbon. Thr was no any apprciabl incras in th ffctiv surfac ara rsulting du to th conglomration of xchangr particls, so 0.3 g/100 ml was considrd as optimum dos 30.

6 1224 A. F. Halbus t al.: Adsorption of Disprs Blu Dy on. Rmoval (%) Dosag of adsorbnt (g) Effct of ph Fig. 4: Th ffct of dosag of adsorbnt on th rmoval of disprss blu dy Th ph of solution is an important factor in th adsorption procss. Fig. 5 shows th ffct of ph on th rmoval of th disprs blu dy onto synthsizd activatd carbon. It was obsrvd that th adsorption of disprs blu dy is unaffctd by changing solution ph and rmaind narly constant ovr th ph rangs from q (mg/g) Fig. 5: Effcts of ph for adsorption of disprs blu on ZDSAC ph

7 Int. J. Chm. Sci.: 11(3), Th prcntag adsorption of disprs blu was not significantly changd whn th initial ph was incrasd from 3 to 11. Thus ph 7 was slctd as th optimum ph valu for all furthr xprimnts du to th advantag of nutral ph valu. As th solubility of disprs dys in aquous solution is low, thy hav a tndncy to accumulat at th surfac of adsorbnts 31. It was found that th adsorption of disprs blu onto activatd carbon rmaind approximatly constant in th ph rang of Whn th adsorbing spcis is not ionizd, no such lctrical rpulsion xists, and thus th packing dnsity on th surfac can b highr 32. Kintics of disprs blu dy adsorption Th kintics of disprs blu dy adsorption on synthsizd activatd carbon ZDSAC wr dtrmind undr th conditions: initial disprs blu concntration 20 ppm, ph 5.5 and tmpratur 25 o C. It was found that th quilibrium tim for both activatd carbon usd in this study was mor than 20 min. To nsur full quilibration, a shaking tim of 60 min was usd for all concntrations of activatd carbon in this study. Th xprimntal data wr procssd with rspct to thr diffrnt kintic modls namly psudo-first ordr 33, psudo-scond ordr 34, and intra-particl diffusion 35. Th quations 4 and 5 rprsnt th linar forms of th psudo-first ordr and psudo-scond ordr modls, rspctivly. ln (q - q t ) = ln q k 1 t (4) t q t 1 t = + (5) k q q 2 2 whr, q (mg/g) and q t (mg/g) ar amounts of disprs blu adsorbd at quilibrium and at tim t, rspctivly. k 1 (min -1 ) and k 2 (g/min.mg) ar th psudo-first ordr and psudo-scond ordr adsorption rat constant, rspctivly. Fig. 6 and Fig. 7 show psudo-first ordr and psudo-scond ordr plots for th xprimntal data. Various rat constants drivd from th slops and intrcpts along with corrlation cofficints ar givn in Tabl 1 and Tabl 2. Th psudo-scond ordr plot in Fig. 7 has bttr corrlation cofficint (R 2 ). Th calculatd valu of adsorption capacity from th plot in Fig. 7 was found to b closr to th xprimntally dtrmind valu than that calculatd from Fig. 6. This suggsts that th psudo-scond ordr modl rprsnts th kintic data mor accuratly.

8 1226 A. F. Halbus t al.: Adsorption of Disprs Blu Dy on. ln (q - q t) ln (q - q t) Tim (min) Tim (min) ln (q - q t) ln (q - q t) Tim (min) Tim (min) ln (q - q t) ln (q - q t) Tim (min) Tim (min) Fig. 6: Psudo-first-ordr-kintic modl for th adsorption of disprs blu dy onto ZDSAC

9 Int. J. Chm. Sci.: 11(3), Tabl 1: Th psudo-first-ordr-kintic modls, for th adsorption of disprs blu dy onto ZDSAC at diffrnt adsorbnt dos Adsorbnt dos Psudo-first-ordr kintic (g/100 ml) q, xp (mg/g) q, calc. (mg/g) k 1 (min 1 ) R t/q t (min.g/mg ) g 0.30 g 0.25 g 0.20 g 0.15 g 0.10 g Tim (min) Fig. 7: Psudo-scond ordr kintic modl for th adsorption of disprs blu dy onto ZDSAC Tabl 2: Th psudo-scond ordr kintic modl for th adsorption of disprs blu dy onto ZDSAC at diffrnt adsorbnt dos Adsorbnt dos Psudo-scond ordr kintic (g/100 ml) q, xp (mg/g) q,calc. (mg/g) K 2 (g/mg.min) R Cont

10 1228 A. F. Halbus t al.: Adsorption of Disprs Blu Dy on. Adsorbnt dos (g/100 ml) Psudo-scond ordr kintic q, xp (mg/g) q,calc. (mg/g) K 2 (g/mg.min) R Th intraparticl diffusion modl, is xprssd as 34 q t = k id t 1/2 + C (6) whr, k id is th intraparticl diffusion rat constant (mg/g.min 1/2 ) and C is a constant rlatd to boundary layr thicknss (mg/g). If intraparticl diffusion is involvd in th adsorption procss, th q t vrsus t 1/2 plot should b linar and should go through th origin, if intraparticl diffusion is th sol rat-controlling stp. Fig. 8 shows that th plot of q t vs. t 1/2 is not linar ovr th ntir tim priod. This implis that mor than on procss is controlling th adsorption. Th dottd lin is indicativ of th intraparticl diffusion on th activatd carbon, for which th rat constant and intrcpt ar givn in Tabl 3. q t (mg/g ) /2 1/2 Tim (min ) 0.10 g 0.15 g 0.20 g 0.25 g 0.30 g 0.35 g Fig. 8: Intraparticl diffusion modl, for th adsorption of disprs blu dy onto ZDSAC

11 Int. J. Chm. Sci.: 11(3), Tabl 3: Th intraparticl diffusion modl, for th adsorption of disprss blu dy onto ZDSAC at diffrnt adsorbnt dos Adsorbnt dos Intraparticl diffusion (g/100 ml) q, xp (mg/g) C (mg/g) K id (mg/g.min 1/2 ) R Adsorption isothrms Th adsorption isothrms wr studid through various modls such as th Langmuir and Frundlich isothrms. Th Langmuir modl is basd on th assumption of homognous monolayr covrag with all sorption sits to b idntical and nrgtically quivalnt. Th Frundlich modl assums physicochmical adsorption on htrognous surfacs. Th linar forms of th two modls ar : Langmuir 1/q = 1/q m + 1/K L q m C Frundlich log q = log K F + 1/n log C (7) (8) whr, q (mg/g) is amounts of disprs blu adsorbd at quilibrium, q m (mg/g) is th monolayr adsorption capacity, K L (L/mg) is th Langmuir adsorption constant rlatd to th fr nrgy of adsorption and C (mg/l) is quilibrium disprs blu concntration in th solution. K F and (1/n) ar Frundlich adsorption isothrm constants bing indicativ of xtnt of adsorption and intnsity of adsorption, rspctivly. Th Langmuir isothrm quation was usd to stimat th maximum adsorption capacity of th activatd carbon undr th following conditions 25 o C, ph 5.5 and 20 ppm initial disprs blu concntration whil varying adsorbnt dos from (0.1 to 0.35 g). Th valus of th isothrm constants and R 2 ar givn in Tabl 4. Th linar plot is shown in Fig. 9, of 1/q vrsus 1/C along with high valu corrlation cofficint indicat that Langmuir isothrm provids a bttr fit with th quilibrium data. Th adsorption data whn fittd to th Langmuir isothrm th plot of 1/q vrsus 1/C in Figur 9 shows that Langmuir isothrm givs a poor fit to th xprimntal data as compard to Frundlich isothrm. Th isothrm paramtrs as drivd from th slop and intrcpt of th plots ar listd in Tabl 4.

12 1230 A. F. Halbus t al.: Adsorption of Disprs Blu Dy on. Tabl 4: Langmuir and Frundlich isothrm constants Isothrm constants Langmuir Frundlich Constants/Corrlation cofficints R 2 q m K L R 2 K F n Valus /q = 1/q + 1/K q C m L m y = x R = /q t /C Fig. 9: Langmuir adsorption isothrms for disprs blu dy adsorption onto ZDSAC log q log q = log K + 1/n log C f y = x R = log C Fig. 10: Frundlich adsorption isothrms for disprs blu adsorption onto ZDSAC

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