Sustainable Conversion of Agriculture and Food Waste into Activated Carbons Devoted to Fluoride Removal from Drinking Water in Senegal

Transcription

1 Intrnational Journal of Chmistry; Vol. 8, No. 1; 2016 ISSN E-ISSN Publishd by Canadian Cntr of Scinc and Education Sustainabl Convrsion of Agricultur and Food Wast into Activatd Carbons Dvotd to Fluorid Rmoval from Drinking Watr in Sngal Mohamad M. Diémé 1, Maxim Hrvy 2, Saïdou N. Diop 1, Clair Gérnt 2, Audry Villot 2, Yvs Andrs 2 & Courfia K. Diawara 1 1 Laboratoir d Chimi t Physiqu ds Matériaux, Univrsité Assan Sck, BP 523, Ziguinchor, Sénégal 2 Ecol ds Mins d Nants, laboratoir GEPEA, UMR CNRS 6144, 4 ru Alfrd Kastlr, BP 20722, Nants cdx 3, Franc Corrspondnc: Saïdou N. Diop, Laboratoir d Chimi t Physiqu ds Matériaux, Univrsité Assan Sck, BP 523, Ziguinchor, Sénégal. sndiop@univ-zig.sn Rcivd: Octobr 8, 2015 Accptd: Novmbr 6, 2015 Onlin Publishd: Novmbr 25, 2015 doi: /ijc.v8n1p8 URL: Abstract Th objctiv of this study was to invstigat th production of activatd carbons (AC) from cashw shlls, and millt stalks and thir fficincy in fluorid rtntion. Ths agricultural rsidus ar collctd from Sngal. It is known that som rgions of Sénégal, commonly calld th groundnut basin, ar affctd by a public halth problm causd by an xcss of fluorid in drinking watr usd by ths populations. Th activatd carbons wr producd by a combind pyrolysis and activation with watr stam; no othr chmical compounds wr addd. Thn, activatd carbonacous matrials obtaind from cashw shlls and millt stalks wr calld CS-H 2 O and MS-H 2 O rspctivly. CS-H 2 O and MS-H 2 O show vry good adsorbnt faturs, and prsnt carbon contnt rangs btwn 71 % and 86 %. Th BET surfac aras ar 942 m² g -1 and 1234 m².g -1 for CS-H 2 O and MS-H 2 O rspctivly. A third activatd carbon producd from food wasts and coagulation-flocculation sludg (FW/CFS-H 2 O) was producd in th sam conditions. Carbon and calcium contnt of FW/CFS-H 2 O ar 32.6 and 39.3 % rspctivly. Th kintics sorption wr prformd with all ths activatd carbons, thn th psudo-first quation was usd to dscrib th kintics sorption. Fluorid adsorption isothrms wr prformd with synthtic and natural watr with th bst activatd carbon from kintics sorption, Langmuir and Frundlich modls wr usd to dscrib th xprimntal data. Th rsults showd that carbonacous matrials obtaind from CS-H 2 O and MS-H 2 O wr wakly fficint for fluorid rmoval. With FW/CFS-H 2 O, th adsorption capacity is mg.g -1 with r² = 0.99 with synthtic watr. Kywords: activatd carbon, adsorption, calcium, fluorid, cashw shll, millt stalk, food wast 1. Introduction In rcnt yars, many studis hav bn don in ordr to rmov th high concntration of many contaminants from drinking watr such as fluorid, lad, arsnic, coppr and nitrat (Sud, Mahajan, & Kaur, 2008). It is known that fluorid is an ssntial lmnt in drinking watr. This trac lmnt is activly involvd in th halth of tth, spcially in th prvntion of dntal cavitis and plays an important rol in bon strngth. Howvr, whn th fluorid concntration in drinking watr is highr than 1.5 mg.l -1, it may caus harmful ffcts on human halth namly dntal fluorosis and skltal fluorosis at concntrations abov 4 mg.l -1 (Srivastav, Singh, Srivastava, & Sharma, 2013; Diallo, Diop, Diémé, & Diawara, 2015). In th world, it is stimatd that mor than 200 million popl ar xposd to drinking watr with a fluorid concntration that xcds th WHO guidlin (1.5 mg.l -1 ) (Bhatnagar, Kumar, & Sillanpää, 2011). Many countris around th world such as India, Bangladsh, Npal, Sénégal, USA, and Mxico ar concrnd by fluorid xposur bcaus of th high numbrs of thir populations that prsnt th ffcts causd by th high concntration of fluorid in thir drinking watr (Fawll t al., 2006; Bibi, Farooqi, Hussain, & Haidr, 2015). Thus, svral procsss for fluorid rmoval hav bn dvlopd. Som ar basd on mmbran tchnologis such as nanofiltration and rvrs osmosis ( Diop, Diémé, & Diawara, 2015), whil othrs us adsorption tchnologis such as adsorption into clay or activatd carbon (Yadav, Abbassi, Gupta, & Dadashzadh, 2013). Mmbran tchnology is wll known for its ffctivnss in fluorid rmoval, but its high oprating cost may rmain a problm for dvloping countris. Many paprs also rport th us of th adsorption procss to rmov fluorid in drinking watr. Activatd carbons ar widly usd as adsorbnts for pollutant rmoval du to thir intrsting physical and chmical proprtis. Morovr, activatd carbons could b low-cost matrials if producd from agricultural wast collctd frly in th 8

2 Intrnational Journal of Chmistry Vol. 8, No. 1; 2016 filds. Prvious paprs studid th fficincy of activatd carbon in fluorid uptak. Consquntly, for nhancing th uptak of fluorid by activatd carbon ths authors hav modifid th adsorbnt by imprgnating it with th calcium solution (Hrnándz-Montoya, Ramírz-Montoya, Bonilla-Ptriciolt, & Monts-Morán, 2012). Th purpos of this study is to produc and charactriz low-cost activatd carbon and to study thir fficincy in fluorid sorption. Th activatd carbons wr producd from millt stalk, cashw shll and a mixtur of food wast and coagulation-flocculation sludg (FW/CFS). Thn ths thr carbonacous matrials wr usd to study fluorid adsorption fficincy. Th Langmuir and Frundlich modls wr usd to dscrib th isothrms xprimntal data and th psudo first ordr quation was also usd to dscrib th kintic data. 2. Matrials and Mthods 2.1 Production of Carbonacous Matrials Millt stalks and cashw shlls namd rspctivly MS and CS, wr usd as prcursors. Millt stalks wr cut into small pics to facilitat thir introduction to th ractor, whil cashw shlls wr lft in thir original stat. Th carbonization (or pyrolysis) was conductd undr an inrt atmosphr (0.5 L/min of N 2 ) up to 850 C with a tmpratur ramp of 10 C/min in a batch quartz rotary furnac (HTR 11/150, Carbolit). At 850 C, th stp of activation was startd with an injction of stam (0.7 ml of watr.min -1 ) as activating gas for 80 minuts. Th cooling of th furnac was still ralizd undr inrt atmosphr. For th FW/CFS, first, pyrolysis char from 50 wt % FW and 50 wt % CFS was producd in smi-continuous scrw ractor by slow pyrolysis (hating rat of 22 C.min -1 ) at 700 C during 30 min. Th dtails of th xprimntal procdur wr dscribd in a prvious papr (Mura, Dbono, Villot, & Pavit, 2013). Th char was thn activatd with stam to produc FW/CFS-H 2 O. Th sam xprimntal procdur as that dscribd abov was usd for th activation procss. AC wr washd with dionizd watr, and drid at 105 C bfor bing charactrizd. This mthod was adaptd from th prvious work ralizd by th rsarch tam (Torrs-Prz, Grnt, & Andrs, 2012). 2.2 Charactrization of Activatd Carbon Elmntal analysis of CHNSO was prformd using th apparatus Flash EA 1112, Thrmofinnigan. Th total ash contnt and ph PZC (point of zro charg) dtrmination of ach activatd carbon wr carrid out following a mthodology prviously dscribd (Torrs-Prz, Grnt, & Andrs, 2012). For th ph PZC, 100 ml of 0.01 mol.l -1 NaCl solution was placd in a closd polythyln bottl. Th ph was adjustd btwn 2 and 12 by adding HCl or NaOH 0.1 mol.l -1 solution. Thn, 0.05 g of ach sampl was addd in th closd polythyln bottl that was st stirring for 5 days at th room tmpratur bfor masuring th final ph. Thn th final ph was plottd against th initial ph, and th point whr this curv crosss th lin ph final = ph initial rprsnts th ph PZC. Th porous proprtis of activatd carbon wr dducd from nitrogn adsorption isothrms at 77 K (ASAP 2020 Micromritics). Th scanning lctron microscopy (SEM) was carrid out using th apparatus JOEL JSM 5800LV, allowing th obsrvation of th porous structur of carbonacous matrials. To dtrmin th prsnc of th othr lmnts such as iron and calcium quantitativ analysis was prformd by using EDX-800HS apparatus. 2.3 Fluorid Adsorption All th masurmnts of fluorid concntration wr prformd by using a UV-1800 spctrophotomtr. Firstly, th suitabl wavlngth for ths masurmnts was dtrmind. Thus, a solution of 2 mg.l -1 was prpard from an initial fluorid solution of 0.2 g.l -1 prpard by dissolution of NaF in dionizd watr (Milli-Q Millipor 18.0 MΩcm -1, rsistivity). Thn a squar cll sampl was filld with 2 mg.l -1 of fluorid solution up to th mark bfor it was placd in th sampl holdr. From thr, th pak wavlngth was dtrmind from th spctrum curv. Thus th maximum wavlngth usd in this study was nm. Analytical masurmnts wr obtaind with a quantification limit of 0.25 mg L -1 and a dtction limit of 0.12 mg L -1. Th quantification limit is th lowst lvl that can b rliably masurd. All thr activatd carbons wr usd in th fluorid adsorption in dionizd watr, bfor th bttr of ths adsorbnts wr usd for th isothrm adsorption both in dionizd and natural watr. For th sorption kintic xprimnts, batch contact tim xprimnts wr conductd at 21 C by stirring 0.8 g of sorbnt with 1000 ml of fluorid solution (5 mg L -1 ) at 250 rpm. Th ph was masurd bfor adding th sorbnt in th polythyln ractor and masurd at th nd of kintic. Thn th quilibrium tim btwn th solid and th solution was dtrmind by plotting th fluorid concntration vrsus tim. Th psudo first ordr sorption modl proposd by (Ho & Mckay, 1998) was usd to dscrib th kintic curvs as indicat by th following quation: dqt k 1 q qt (1) dt 9

3 Intrnational Journal of Chmistry Vol. 8, No. 1; 2016 Whr q and q t ar th sorption capacitis at quilibrium and at tim t rspctivly (mg.g -1 ) and k 1 is th rat constant of psudo first ordr sorption (min -1 ). Thn th intgration with th conditions follow, t = 0 to t = t and q = 0 to q = q, th linar form obtaind is xprssd as follow: t t t k1 log t q q logq t k wr calculatd by plotting (2) Th paramtrs q and 1 log q q t vrsust. Bath adsorption isothrms wr conductd at 21 C with 250 ml of synthtic solution from 3 to 25 mg.l -1 of fluorid and g of adsorbnt. Thn th ractors hav bn stirrd for 120 min at 250 rpm. Th ph was masurd bfor adding th sorbnt and at th nd of th xprimnt, th valus rangd btwn 5 and 9. Langmuir and Frundlich modls wr usd to dscrib th xprimntal data of th isothrms (Frundlich, H.M., 1906); (Langmuir, I., 1918). Th Langmuir quation is dscribs blow: 10 q q bc m (3) 1 bc Whr b is th quilibrium constant of th raction (L.mg -1 ), q m and C ar th maximum adsorption capacity (mg.g -1 ) and th amount of fluorid at quilibrium (mg.l -1 ), rspctivly. Th Frundlich quation is givn blow: q K C (4) Whr K f (mg.g -1 )/(mg.l -1 ) 1/n and n th Frundlich isothrm constant rlatd to th adsorption capacity. In sorption procsss, it is know that th prsnc of othr ions can contribut to a comptitiv ffct btwn th ions, lading to a modification of th adsorption capacitis. Thus th isothrm adsorption was prformd with natural watr, th composition of which is givn in Tabl 1. Tabl 1. Minral contnt of natural watr Elmnts Ca 2+ Mg 2+ Na + K + - HCO 3 Cl SO 4 NO 3 C (mg.l -1 ) Th potntial ffct of ths ions into th adsorption capacity will b discussd blow. 3. Rsults and Discussions 3.1 Charactrization of Activatd Carbon Th chmical charactrization (lmntal analysis and ph PZC ) and th physical charactrization (BET surfac ara analysis) ar givn in th Tabl 2. Tabl 2. Proprtis of activatd carbons Mass fraction /% S Matrial ph BET V micro V mso Total porous C H O Ash PZC /m².g -1 /cm 3.g -1 /cm 3.g -1 volum /cm 3.g -1 MS-H 2 O CS-H 2 O FW/CFS-H O As svral activatd carbons producd at laboratory scal, th major lmnt contnts of thm ar C, O and H. Th carbon prcntag showd in Tabl 1 is 86.0 %, 71.0 % and 32.6 % for th MS-H 2 O, CS-H 2 O and FW/CFS-H 2 O rspctivly. Th valus of carbon contnt of MS-H 2 O and CS-H 2 O lad to ral carbonacous matrials. In th litratur, similar valus wr obtaind during rsarch activitis for th activatd carbons production from agricultural wasts (Rashidi, Yusup, Ahmad, Mohamd, & Hamd, 2012; Torrs-Prz, Grnt, & Andrs, 2012; Skirifa, Hadj-Mahammd, Pallir, Baamur, Richard, & Al-Dujaili, 2013). In contrast, th carbon contnt of activatd carbon from th mixtur of food wast and coagulation-flocculation sludg (FW/CFS-H 2 O) is low (32.6 %). This carbon contnt may ngativly impact on th BET surfac ara. As an idntical production mthod was usd, th diffrncs in th proprtis of th activatd carbons ar only assignd to th prcursor natur. Th scond major lmnt of th activatd carbon is oxygn. Its contnt is 12.2 %, 21.0 % and 6.6 % for th MS-H 2 O, CS-H 2 O and FW/CFS-H 2 O rspctivly. Ths valus of oxygn contnt ar clos to thos obtaind by Torrs-Prz, Grnt, & Andrs, (2012) that hav charactrizd two commrcial granular activatd carbons. f n

4 Intrnational Journal of Chmistry Vol. 8, No. 1; 2016 Th ash contnt is 0.1 % and 6.5 % for MS-H 2 O and CS-H 2 O rspctivly and ths valus ar clos to thos obtaind in th litratur ( Torrs-Prz, Grnt, & Andrs, 2012). Howvr, th ash contnt in FW/CFS-H 2 O is significantly highr: 62.2 %, this valu is so high that it can xplain th low carbon contnt of this matrial. Gnrally whn w an activatd carbon prsnts a low carbon contnt and a high ash contnt, its BET surfac ara is low. Finally all ths carbonacous matrials rval a basic ph PZC, rangingg from 8.0 to Thus th surfac charg of carbonacous matrials is ngativ. As dscribd abov, th BET surfac araa is prformd with ASAP 2020 Micromritics by nitrogn adsorption at 77 K. Th rsults ar prsntd in th Tabl 2. Thus th BET surfac ara of th MS-H 2 O, CS-H 2 O and FW/CFS-H 2 O is 1324 m².g -1, 942 m² ²g -1 and 225 m².g -1 rspctivly. For th MS-H 2 O and CS-H 2 O, thir high contnt of carbon and a low ash contnt probably allow ths carbonacous matrials to dvlop th BET surfac ara abov 800 m².g -1. During thir work in 2012, Torrs-Pérz t al, producd two activatd carbons from agricultural wasts, and thir BET surfac aras rangd btwn 821 and 829 m²g -1. Bsid th high BET surfac araa dvlopd by MS-H 2 O and CS-H 2 O, as xpctd, th FW/CFS-H 2 O has th lowst valu (218 cm²g -1 ). With SEM micrograph and EDX spctra of ths activatd carbons (data not shown) it was possibl to apprciat th diffrnc btwn th macropors upon th surfac of ach sampl. Thn with th EDX spctra, th high prsnc of calcium was found in th FW/CFS-H 2 O with a prcntag of 39.3 %. Concrning th total porous volums, th valus obtaind with th MS-H 2 O, CS-H 2 O and FW/CFS-H 2 O ar cm 3.g -1, cm 3.g -1 and cm 3 g -1 (Tabl 2). As for th BET surfac aras, th activatd carbons from millt stalks and cashw shlls prsnt th highst total porous volums. Howvr, all ths activatd carbons hav a dvlopd microporous natur. Th nitrogn adsorption isothrms obtaind confirm th microporous natur of ths activatd a carbons. MS-H 2 O and CS-H 2 O dvlop a microporous volum ranging btwn and cm 3.g -1 ; for th FW/CFS-H 2 O, th microporous volum is cm 3 g -1. Ths valus of microporous volum obtaind in this study can b compard to data found by Bandosz & Ania, (2006). Th msoporous volums ar 0.033, and cmm 3 g -1 for MS-H 2 O, CS-H 2 O and FW/ CFS-H 2 O rspctivly. 3.2 Fluorid Rmoval with Carbonacous Matrials Sorption Kintics With MS-H 2 O, CS-H 2 O and FW/CFS-H 2 O, batch contact xprimnts wr prformd. Th kintics curvs of CS-H 2 O and FW/CFS-this matrial is not plottd 2 O ar dpictd in Figur 1. MS-H 2 O displayd a fluorid uptak almost null, thus th kintic curv of hr. Figur 1. Kintic dcay curvs for fluorid uptak on CS-H 2 O and FW/CFS-H 2 O From ths kintic dcay curvs for rmoval of fluorid on ths activatd carbons, th optimal contactt tim is dtrmind as 20 min and 2 h for CS-H 2 O and FW/CFS-H 2 O rspctivly. Thus, xprimntal adsorption capacity for CS-H 2 O is 1.61 mg.g -1, whil for FW/CFS-H 2 O, th xprimntal adsorption capacity rach 5.29 mgg quilibrium tim. Tabl 3 prsnts th paramtrs q -1- at th and k 1 calculatd from linar form of psudo first ordr quation by plotting log q q t vrsust. Tabl 3. Paramtrs of psudo first ordr kintic modl Matrial q, xp (mg.gg -1 ) q CS-H 2 O 1.61, cal (mg.g -1 ) k 1 (min -1 ) r² FW/CFS-H 2 O

5 Intrnational Journal of Chmistry Vol. 8, No. 1; 2016 Th psudo first ordr modl tstd in this study dos not dscrib vry wll th xprimntal data spciallyy for th xprimntal data obtaind with CS-H 2 O that r² = With its low adsorption capacity of fluorid this matrial will not b usd for th quilibrium adsorption isothrms. It appars hr that th BET surfac ara and th carbonn contnt ar not dcisiv factors for th fluorid adsorption bcaus CS-H 2 O has th highr BET surfac ara and carbonn contnt than FW/CFS-H 2 O. Furthrmor, th xprimntal fluorid adsorption capacity of 5.29 mg.g -1 is rachd and th psudo first ordr dscrib bttr th xprimntal data with r² = 0.91 vn if th fluorid adsorption capacity calculatd is ovrstimat (8.59 mg.g -1 ). Th psudo first ordr quation dos not fit wll th xprimntal data of kintic sorption. Gnrally, this modl is applicabl ovr th initial 20 to 30 min of th kintic sorption (Ho & McKay, 1998; Grnt, V.K.C. L, L Cloirc, & McKay, 2007; Islam & Patl, 2011) Adsorption Isothrms Adsorption isothrms wr carrid out during 2h of contact tim btwn th fluorid solution with initial concntrations ranging btwn 3 to 25 mg.l -1, and ph ranging from 5 to 9. Th xprimntal data ar plottd whil w th Langmuir and Frundlich quations ar usd to modl th xprimntal curv of th fluorid uptak (Figur 2). Th Langmuir isothrm rflcts th monolayr adsorption whil th Frundlich isothrm shows th multilayr adsorption. Figur 2. Exprimntal adsorption isothrm of fluorid using th Langmuir and Frundlich modls From ths curvs, th Langmuir modl fits th xprimntal data vry wll with r² = 0.99 as wll as th Frundlich modl (r² = 0. 98). In th Tabl 4, th modlling paramtrs of Langmuir and Frundlich ar listd. Tabl 4. Isothrm paramtrs of fluorid adsorption on FW/CFS-H 2 O Langmuir Frundlich Matrial q (mg.g -1 ) b (L.mg -1 ) r² m K ((mg.g -1 )/((mg.l -1 ) 1/n ) n r² f FW/FCS-H 2 O Concrning th Frundlich modl, K is found to 9.95 (mg.g -1 )/(mg.l -1 ) 1/n with r² = 0.98 and n = Rgarding th f Langmuir modl, th adsorption capacity q L.mg -1 m is mg.g -1 and quilibrium constant of th raction b = Th valu of qm calculatd from th Langmuir modl is similar to th xprimntal data which is mg.g -1. This match indicats that a monolayr adsorption is involvd in fluorid sorption and only th intractions btwn th fluorid spcis and th adsorbnt surfac occur. Dspit its low BET surfac ara and th low carbon contnt than CS-H 2 O, th FW/FCS-H 2 O can b an altrnativ and fficint sorbnt for fluorid rmoval from drinking watr. This high adsorption capacity suggsts that th high prsnc of calcium upon th adsorbnt plays a vry important rol in th uptak of fluorid. Ths thr activatd carbons wr producd by adapting th sam mthod and non hav bn modifid. Indd during thir activity rsarch, Hrnándz-Montoya t al., (2012) usd pcan nut shlls as prcursor for th production of activatd carbon. Th activatd carbons wr thn imprgnatd with a calcium solution xtractd from gg shlls. Th calcium contnt in thir activatd carbon ar rangd btwn 1.6 and 4.48 %. Using th Langmuir modl, th activatd carbon with th highst calcium contnt t rachd th bttr adsorption capacity with th valu of 2.51 mgg -1. Th BET surfac ara of this modifid activatd carbon is 17 m²g -1. This adsorption capacity rmains significantly lowr than thatt obtaind in our study with th non-modifid FW/FCS-H (2012) obtaind an adsorption capacity of 2 O (28.48 mg.g -1 ) which naturally n contains calcium spcis. Sivasankar, Rajkumar, Murugsh, & Darchn, mg.g -1 using th Langmuir modl with carbonacous matrial from tamarind fruit shll imprgnatd in ammonium carbonat solution. Th calcium contnt and BET surfac ara of this modifid carbonacous matrial wr 7.2 % and 473 m².g -1, rspctivly. At th prsnt tim, many rsarch activitis ar bing don to rmov xcss 12

6 Intrnational Journal of Chmistry Vol. 8, No. 1; 2016 fluorid from drinking watr on th adsorbnts and a high adsorption capacity ar rachd (Srivastav, Singh, Srivastava, & Sharma, 2013; Zhang, Lu, Lin, Su, & Zhang, 2014; Bibi, Farooqi, Hussain, & Haidr, 2015). Figur 3, dpicts th initial concntration of fluorid against th prcntag of rmoval fluorid obtaind with dionizd d watr and natural watr. Figur 3. Prcntag of rmoval fluorid in synthtic and natural watr Indd th hypothsis statd abov is vrifid according to th shap of th curvs obtaind with natural watr w and dionizd watr (synthtic watr in th figur). Th prsnc of othr ions promotd a comptitiv ffct btwn th fluorid ion (F - ) and thos of natural watr (Tabl 1) ). It is probably th anions prsnt in natural watr which w ar rsponsibl for th ffct of comptition with th fluorid anion. Th potntial anions in natural watr whichh can b comptitor anion ar HCO - 3, Cl -, SO 2-4 and NO - 3. Morovr, a possibl attraction could tak plac btwn th fluorid anion in solution and calcium cations in FW/FCS-H 2 O. Finally, th rsults obtaind in this study and thos rportd in th litratur hav shown th issu of fluorid worldwid can b solvd by using activatd carbons producd from various agricultural rsidus or wast as adsorbnts. 4. Conclusionn In th prsnt study, thr activatd carbons wr prpard from millt stalks (MS-H 2 O), cashw shlls (CS-H 2 O), food wasts and coagulation-flocculationn sludg (FW/CFS-H 2 O). Th MS-H 2 O and CS-H 2 O hav dvlopdd a grat chmical and physical charactristic proprtis. Thn thy wr studid as sorbntss for fluorid rmoval from drinking watr. Only FW/CFS-H 2 O had shown a grat potntial for fluorid rmoval with prcntags abov 70 and 800 % with natural and synthtic watr rspctivly. From kintic sorption, th quilibrium tim is 2h and th psudo first ordr dos not fit th xprimntal data vry wll. Rgardingg quilibrium data, th xprimntal data ar bttr dscribd by Langmuir modl than by th Frundlich modl. A high adsorption capacity is providd by Langmuir in dionizd watr (28.48 mgg -1 ). With an initial fluorid concntration of 7 mgl -1, th rmaining fluorid concntration masurdd aftr 2h quilibrium tim with FW/CFS-H 2 O is 1..4 mg.l -1. Th limit stablishd by th WHO is 1.5 mgl -1 for drinking watr. Gnrally, th drinking watr which prsnts xcss fluorid concntration rangs btwn 3 and 8 mg.l -1. That mans FW/CFS-H 2 O can b usd in watr tratmnt spcially for fluorid rmoval. Acknowldgmnts This rsarch was supportd by th Frnch Embassy in Sngal via its Cultural and Coopration Dpartmnt which allows Sngal PhD studnts to raliz scintific stays in Frnch laboratory. All th xprimnts of this study wr carrid out in th Enrgy and Environmntal Enginring Dpartmnt (DSEE) of Ecol ds Mins d Nants-Franc. And M. Hrvy wishs to thank Institut Carnot M.I.N.E.S for its financial support. Rfrncs Bandosz, T. J., & Ania, C. O. (2006). Chaptr 4 Surfac chmistry of activatd carbons and its charactrization. In Trsa J. Bandosz (éd.). Intrfac Scinc and Tchnology, Bhatnagar, A.., Kumar, E., & Sillanpää, M. (2011). Fluorid rmoval from watr by adsorption A rviw. Chmical C Enginring Journal, 171(3), /j.cj

7 Intrnational Journal of Chmistry Vol. 8, No. 1; 2016 Bibi, S., Farooqi, A., Hussain, K., & Haidr, N. (2015). Evaluation of industrial basd adsorbnts for simultanous rmoval of arsnic and fluorid from drinking watr. Journal of Clanr Production, 87, Diallo, M. A., Diop, S. N., Diémé, M. M., & Diawara, C. K. (2015). Efficincy of nanofiltration mmbran TFC-SR3 and SlRo MPF-34 for partial limination of fluorid and salinity from drinking watr. Journal of Watr Rsourc and Protction, 7, Fawll, J., Baily, K., Chilton, J., Dahi, E., Fwtrll, L., & Magara, Y. (2006). Fluorid in drinking watr, WHO-IWA (p ). WHO. Frundlich, H. M. (1906). Ovr th adsorption in solution. J. Phys. Chm., 57, Grnt, C., V. K. C., L, L., Cloirc, P., & McKay, G. (2007). Application of Chitosan for th Rmoval of Mtals From Wastwatrs by Adsorption Mchanisms and Modls Rviw. Critical Rviws in Environmntal Scinc and Tchnology - CRIT REV ENVIRON SCI TECHNOL, 37(1), Hrnándz-Montoya, V., Ramírz-Montoya, L. A., Bonilla-Ptriciolt, A., & Monts-Morán, M. A. (2012). Optimizing th rmoval of fluorid from watr using nw carbons obtaind by modification of nut shll with a calcium solution from gg shll. Biochmical Enginring Journal, 62, Ho, Y. S., & McKay, G. (1998). A Comparison of Chmisorption Kintic Modls Applid to Pollutant Rmoval on Various Sorbnts. Procss Safty and Environmntal Protction, 76(4), Ho, Y. S., & Mckay, G. (1998). Kintic Modls for th Sorption of Dy from Aquous Solution by Wood. Procss Safty and Environmntal Protction, 76(2), Islam, M., & Patl, R. (2011). Thrmal activation of basic oxygn furnac slag and valuation of its fluorid rmoval fficincy. Chmical Enginring Journal, 169(1-3), Langmuir, I. (1918). Th adsorption of gass on plan surfac of glass, mica and platinum. J. Am. Chm. Soc., 40, Muro, E., Dbono, O., Villot, A., Pavit, F., (2013) Pyrolysis of biomass in smi-industrial scal ractor: Study of th ful-nitrogn oxidation during combustion of volatils. Biomass Bionrgy 59, Rashidi, N. A., Yusup, S., Ahmad, M. M., Mohamd, N. M., & Hamd, B. H. (2012). Activatd Carbon from th Rnwabl Agricultural Rsidus Using Singl Stp Physical Activation: A Prliminary Analysis. APCBEE Procdia, 3, Skirifa, M. L., Hadj-Mahammd, M., Pallir, S., Baamur, L., Richard, D., & Al-Dujaili, A. H. (2013). Prparation and charactrization of an activatd carbon from a dat stons varity by physical activation with carbon dioxid. Journal of Analytical and Applid Pyrolysis, 99, Sivasankar, V., Rajkumar, S., Murugsh, S., & Darchn, A. (2012). Tamarind (Tamarindus indica) fruit shll carbon: A calcium-rich promising adsorbnt for fluorid rmoval from groundwatr. Journal of Hazardous Matrials, , Srivastav, A. L., Singh, P. K., Srivastava, V., & Sharma, Y. C. (2013). Application of a nw adsorbnt for fluorid rmoval from aquous solutions. Journal of Hazardous Matrials, 263, Part 2, Sud, D., Mahajan, G., & Kaur, M. P. (2008). Agricultural wast matrial as potntial adsorbnt for squstring havy mtal ions from aquous solutions A rviw. Biorsourc Tchnology, 99(14), Torrs-Prz, J., Grnt, C., & Andrs, Y. (2012). Convrsion of agricultural rsidus into activatd carbons for watr purification: Application to arsnat rmoval. Journal of Environmntal Scinc and Halth Part a-toxic/hazardous Substancs & Environmntal Enginring, 47(8), Yadav, A. K., Abbassi, R., Gupta, A., & Dadashzadh, M. (2013). Rmoval of fluorid from aquous solution and groundwatr by what straw, sawdust and activatd bagass carbon of sugarcan. Ecological Enginring, 52, Zhang, S., Lu, Y., Lin, X., Su, X., & Zhang, Y. (2014). Rmoval of fluorid from groundwatr by adsorption onto 14

8 Intrnational Journal of Chmistry Vol. 8, No. 1; 2016 La(III)- Al(III) loadd scoria adsorbnt. Applid Surfac Scinc, 303, Copyrights Copyright for this articl is rtaind by th author(s), with first publication rights grantd to th journal. This is an opn-accss articl distributd undr th trms and conditions of th Crativ Commons Attribution licns ( 15