The preparation of activated carbon from South African coal

Transcription

1 The peption of ctivted cbon fom South Aficn col by Q.P. Cmpbell*, J. R. Bunt*, H. Ksini, nd D.J. Kuge* J o u n l Synopsis Activted cbons used in the pecious metls extction industy e chcteized by lge intenl sufce es nd get ffinity fo metl ions. The pupose of this esech is to pepe ctivted cbon fom South Aficn bituminous col by physicl ctivtion tht is suitble nd cost-effective fo use in the extction of metls. The qulity of the col-bsed ctivted cbon my not pove to be s good s ctivted cbon poduced fom othe tditionl souces, but the poduction costs involved my mke South Aficn col fesible ltentive feedstock. The ctivted cbons poduced wee chcteized by Bunue, Emmett, nd Telle (BET) sufce e, ctivted cbon ph, nd phenol dsoption studies nd the esults comped to the esults fom commecilly vilble ctivted cbon, Noit RO 0.8 (contol smple). Bituminous cols fom vious souces including Witbnk Sem 4 nd Fee Stte col wee used in this study. The peption method chosen ws physicl ctivtion using supeheted stem. The effects of pocess vibles such s ctivtion time (1 3 h) nd tempetue ( C) wee studied in ode to optimize those pmetes. The ctivted cbon sufce e ws chcteized by mens of nitogen dsoption isothems t 77K. BET sufce e nlysis showed tht Witbnk Sem 4 col ctivted t tempetue of 800 C nd ctivtion time of 3 hous esulted in sufce e of 340 m2/g. Qulity contol of ech smple ws pefomed by mesuing the ph of known mount of the peped ctivted cbon in distilled wte ove time. Results showed tht the ph of some of the peped ctivted cbons eched vlue of 11. Phenol dsoption esults fo the diffeent ctivted cbons peped coesponded well to the esults obtined fo the Noit RO 0.8 ctivted cbon smple. Keywods ctivted cbon, pecious metl, South Aficn col, sufce e, phenol dsoption. poduced depends pimily upon the w mteil, nd to lesse extent upon the pocess of mnufctue1. Activted cbon cn be mnufctued fom ny cellulosic o lignocellulosic mteil3. Bituminous col is one of these types of mteils tht cn be used to mnufctue ctivted cbon becuse of its inheent micostuctue4. Othe pecusos tht hve been poven successful e gicultul wstes, coconut shells5, pecn nut shells6,7, nd even boile mnue8. The ctivtion of the w mteil in ode to pepe ctivted cbon cn be cied out in two wys: chemicl nd physicl ctivtion9. Chemicl ctivtion is whee the w mteil is teted using ny dehydting gent tht dissolves cellulosic components10,11. Physicl ctivtion is when the cbonceous mteil is fist devoltilized fo n extended peiod of time (1 48 hous), nd then the fomed ch is teted with ny oxidizing gent such s cbon dioxide o stem. The oxidizing gent ects with the cbon to fom gseous poducts, which esults in poes nd chnnels being ceted10,12. Loenc-Gbowsk et l4 developed mesopoosity in lignite nd gs col (high-voltile bituminous col) by col modifiction using C- nd Fe-exchnge, nd epoted tht 20 25% incese of mesopoe volume ws obseved. Gñn et l13 peped high-poosity cbons fom bituminous col pitches by the combined use of chemicl nd physicl ctivtion. The ctivted cbons peped using this pocess hd sufce es in excess P p e Bckgound nd intoduction Activted cbon (lso ctivted chcol, ctivted col), n mophous, non-gphitic fom of cbon, is chcteized by lge specific sufce e of m2/g, which llows fo the physicl dsoption of gses nd vpous s well s dissolved o dispesed substnces fom liquids1,2. Gs-phse cbons hve pedominntly fine poes, less thn 100 Å in dimete; whees the poe dimetes fo liquid-phse cbons hve bod nge of Å. The clss of ctivted cbon * School of Chemicl nd Minels Engineeing, Noth-West Univesity School of Chemicl Engineeing, Tshwne Univesity of Technology. The Southen Aficn Institute of Mining nd Metllugy, SA ISSN X/ Ppe eceived Jun. 2010; evised ppe eceived Jun The Jounl of The Southen Aficn Institute of Mining nd Metllugy VOLUME 112 JANUARY

2 The peption of ctivted cbon fom South Aficn col of 400 m2.g-1. Qing et l14 investigted the selective dsoption popeties of SO 2 nd NO onto col-bsed ctivted cbon. Hsu nd Teng15 peped ctivted cbon fom bituminous col vi chemicl ctivtion (ZnCl 2, H 3 PO 4, nd KOH), fte which the smple ws cbonized in nitogen t vious tempetues. It ws found tht ZnCl 2 nd H 3 PO 4 wee not suitble fo peping high-poosity cbons fom bituminous col, while KOH cn poduce cbons with high poosity. Minel mtte content cn ffect the dsoptive cpcity of n ctivted cbon. Lines-Solno et l16 investigted this subject nd epoted tht the smples with lowe sh content yielded highe micopoe volumes. Numeous ticles hve lso been published with egds to the extction of metl utilizing ctivted cbon. Riz Qdee17 hs pefomed extensive esech on the dsoption of uthenium ions on ctivted cbon. The emovl of this ion is impotnt fo puifiction, wste tetment, nd tce metl nlysis. Ylcin nd Ihsn Aol18 epoted tht due to the expnsion of the gold industy, the use of coconut shells s w mteil fo the poduction of ctivted cbon suitble fo gold dsoption fom cynide lech liquos is costly nd the exploittion of othe w mteils should be consideed. They investigted the use of hzelnut shells, picot nd pech stones, nd studied the gold loding cpcity nd dsoption kinetics. Zhng et l19 studied the dsoption of the gold thioue complex onto ctivted cbon nd found tht equilibium gold loding decesed with n incese in thioue concenttion, solution ph, nd tempetue. Fg et l20 investigted the ole of cbon sufce sites on the popeties of cbon-suppoted pltinum ctlysts. They pe-teted commecilly vilble ctivted cbon (Noit ROW 0.8 s) nd pefomed oxidtive tetments on the cbon to cete sufce cidic sites nd destoy sufce bsic sites. Fu et l21 studied the dsoption nd eduction of Pt(IV) on ctivted cbon fibe (ACF). They investigted the eltionship between the dsoptioneduction of the metl nd the ctivted cbon peption conditions, s well s dsoption conditions (solid/liquid tio, Pt(IV) concenttion, ection tempetue, nd solution ph). They concluded tht Pt(IV) dsoption-eduction cpcity onto noml ctivted cbon fibes is not popotionl to the specific sufce e. Ji et l22 investigted the dsoption chcteistics of gold nd silve cynide nionic species on suite of ctivted cbons deived fom col, coconut shell, nd polycylonitile. Ksini et l23 investigted the selective dsoption of pltinum fom mixed chloide solutions contining bse metls using chemiclly modified ctivted cbons. Fom the bove it is cle tht thee e mny pmetes tht ffect cbon pefomnce. The mount nd distibution of poes ply key oles in detemining how well contminnts e dsobed. Adsoption is lso ffected by the chemicl ntue of the dsobing sufce becuse the sufce intects to cetin extent with ognic molecules. Electicl foces between the sufce nd some ognic molecules my lso esult in dsoption o ion exchnge. But genelly, the lest soluble ognic molecules e most stongly dsobed, nd often the smlle ognic molecules e held the tightest, becuse they fit into the smlle poes. Adsoption usully inceses s ph nd tempetue decese nd contct time is incesed. In South Afic, cuent pecious met.l concentto plnts nd efineies e unble to etieve ll of the vlubles, nd significnt quntities of pecious metls e discded on tiling dms. The scope of the poject is to poduce n ctivted cbon tht will be ble to dsob pecious metl ions fom dilute solutions. Othe studies24 hve poven tht Noit RO 0.8 is suitble fo this dsoption pocess, but this mteil hs to be impoted. It hs been shown tht South Aficn col cn be used s w mteil fo the mnufctuing of ctivted cbon25, but studies hve not been conducted to exploe futhe pplictions of the ctivted cbon thus poduced. This study hs theefoe imed to poduce n ctivted cbon, using South Aficn col, which must meet cetin citei specificlly concening sufce e nd dsoption chcteistics. The successful ctivted cbon will be used in lte dsoption studies to chcteize the success of the choice of w mteil nd peption method, which will fom the bsis of futue ppe. Two South Aficn cols wee selected s pecuso mteils fo the peption of ctivted cbon. Expeiments wee conducted to detemine the optimum pmetes such s ctivtion time nd tempetue. BET sufce e nlysis, ph mesuements, nd phenol dsoption wee used to quntify whethe the peped ctivted cbon is of suitble qulity. Key chcteistics tht influence the suitbility of ctivted cbon fo use in poduction plnt i.e. hdness (dubility), pticle shpe (impotnt fo sceening), nd potentil fo fouling by ognics o othe contminnts flls outside the scope of this study nd e thus not consideed.hee. The intention of this ticle is not to demonstte kinetics nd equilibium lodings of PGM o Au fom solution using the col-deived ctive cbons, but the to use indiect indictos such s Bunue, Emmett, nd Telle (BET) sufce e nd phenol dsoption to indicte potentil fo metl loding. Expeimentl To chieve the desied esults in mnufctuing n ctivted cbon meeting ll citei, n expeimentl pocess needed to be consideed. This section consides the expeimentl pocedue tht ws followed, nd ddesses the equipment tht ws used s well s the chcteiztion methods employed. It should be noted tht the pecious metl ppliction testing of the col-deived ctive cbons is excluded fom this explotoy study. Genel pocess considetions, i.e. loded metl ions dsobed fom the lech solution using gitted tnks with intestge sceens followed by elution, wee used to detemine which popeties e impotnt. This philosophy ssisted in detemining the pefomnce citei chosen to mesue (BET sufce e, phenol dsoption, nd ph) which e indeed the most impotnt pmetes fo the ppliction. Absion nd sceening testing of the loded cbon should be consideed in futue dsoption studies. Col The w cols used in this study wee souced fom two es in South Afic, i.e. Witbnk sem 4 (Kiel opencst), nd Fee Stte col (New Vl Colliey). Both of these cols e esonbly epesenttive of col in ech of these es s cn be seen fom the poximte nlysis esults (Tble I) 38 JANUARY 2012 VOLUME 112 The Jounl of The Southen Aficn Institute of Mining nd Metllugy

3 The peption of ctivted cbon fom South Aficn col comped with the litetue26. The s-eceived (..) smples wee stge cushed nd sieved to now pticle size nge (+860 μm μm), clened using dilute solution of 1M HCl to emove ny inognic mteil, nd then wshed using distilled wte, filteed, nd died unde vcuum t 105 C fo ppoximtely 6 hous. Poximte nlysis ws conducted on the sized col smples. Activtion ecto setup The min components in the expeimentl setup (s shown in Figue 1) include veticl tube funce cpble of eching tempetues of up to C, nd stem geneto with piston pump deliveing the equied flow te of stem. The wte fo the stem geneto ws supplied vi esevoi which ws locted on lod cell. The mss chnge (W) ws ecoded, fom which the stem flow te ws detemined. It ws ssumed tht the mss loss in the esevoi ws n indiction of the stem flow te supplied to the funce. The stem geneto ws contolled t tempetue of 160 C. The stem ws mixed with nitogen nd pssed though heting stge which ws lso contolled t 160 C. The piping to the funce ws well insulted to ensue miniml het loss. The stem/nitogen mixtue ws then pssed ove the smple in the funce. A themocouple in the ecto ensued tht the smple tempetue ws monitoed nd logged. The length of the ecto ws 200 mm, while the length of the heting zone ws 300 mm. This ensued tht both the coil nd the ection zone wee t the contolled tempetue. The coil ensued tht the stem/nitogen mixtue ws bought fom its initil tempetue of ±160 C to the tempetue tht the funce ws contolled t. With ech expeimentl un, 20 g of the sized nd clened col ws fistly devoltilized using nitogen pio to stem ctivtion. This smple mount occupied ppoximtely hlf of the volume of the ecto. The devoltiliztion tempetue ws vied between 600, 700, nd 800 C; nd the stem ctivtion expeiments, using supeheted stem t flow te of 13.7 cm3/(g.h) ws vied fo peiods of 1, 2, nd 3 hous. Afte ection, the funce ws llowed to cool to below 45 C befoe emovl of the smple. Activted cbon chcteiztion The peped ctivted cbon smples wee chcteized using BET sufce e detemintion, phenol dsoption studies, nd cbon ph testing. These esults wee comped to the commecilly vilble ctivted cbon (Noit RO 0.8). The NORIT efeence cbon ws chosen s benchmk bsed on simility of ppliction; i.e. pet-deived, high sufce e. BET sufce e The sufce es of the col-deived ctivted cbons wee detemined by mens of nitogen dsoption expeiments in Micometics ASAP 2010 Anlyze. Initilly the smples wee degssed t 25ºC fo peiod of 48 hous. Afte degssing, the cbons wee nlyzed by mens of gs dsoption using nitogen s sobent. All of the gs dsoption expeiments wee done t tempetue of 77K using stution pessue (P 0 ) of < 660 mm Hg. Phenol dsoption studies Activted cbon ws stied in phenol solution nd smples wee tken t vious intevls. These smples wee then nlyzed using ultviolet spectophotomete (UV-vis) to detemine the phenol concenttion of the pent solution. The concenttion esults eflect the mount of phenol tht ws dsobed by the ctivted cbon. Befoe the phenol concenttion could be detemined, it ws necessy to obtin clibtion cuve. This ws pefomed by mesuing the dsobnce of diffeent concenttions of phenol with the use of the UV-vis. The dsobnce dt ws plotted ginst the diffeent concenttions nd stight line ws fitted. J o u n l P p e Figue 1 Schemtic of the expeimentl setup The Jounl of The Southen Aficn Institute of Mining nd Metllugy VOLUME 112 JANUARY

4 The peption of ctivted cbon fom South Aficn col ph mesuement Two gms of the ctivted cbon smple ws dded to 40 cm3 of distilled wte nd stied t speed of /min. The ph of the solution ws mesued evey 5 minutes fo peiod of 200 minutes. When the ctivted cbon nd de-ionized wte ws mixed nd stied, it ws obseved tht the mximum ph vlue ws eched within 60 minutes. It ws lso seen tht fte eching the mximum ph vlue fo specific smple, the ph gdully decesed nd did not stbilize. Fom the mesued ph esults, the following clcultions wee pplied nd gphs wee obtined fo the diffeent smples. ΔpH vesus time(s) ΔpH /dt vesus time(s) ph vesus time(s) to obtin dsoption constnt * ph vesus time(s) to obtin de-soption constnt *. The dsoption nd desoption tes wee detemined fom the initil nd finl slope of the ph vesus contct time gphs. All tests wee conducted in duplicte to ssess epetbility, nd the veged dt is pesented in the discussion of the esults. Results nd discussion The poximte nlysis esults fo the Witbnk 4 sem col nd the Fee Stte col e given in Tble I. These will be discussed pio to eviewing the ctivted cbon chcteiztion esults. Fom Tble I it cn be obseved tht the feed col moistue contents wee 1.3% nd 2.4% fo the Witbnk sem 4 nd Fee Stte cols espectively. On dy bsis, the [1] [2] Tble I Rw col poximte nlysis esults Test Witbnk Sem 4 Fee Stte % Moistue (SABS 924) 1.31% 2.37% % Ash (DB) (ISO 1171) 29.94% 34.40% % Voltiles (DAFB) (ISO 562) 28.17% 29.96% % Fixed Cbon (Clcultion) 49.67% 44.86% Cloific Vlue (ISO 1928) 22.33MJ.kg MJ.kg-1 espective sh contents wee 30% nd 34.4%; nd on dy sh fee (d..f.) bsis the voltile mtte contents wee esonbly simil, i.e. 28% nd 30%. The fixed cbon pecentge ws clculted to be highe fo the Witbnk Sem 4 col (49.7%) when comped to the Fee Stte col (44.9%). Thus the heting vlue (ISO 1928) ws lso mesued to be highe fo the Witbnk sem 4 col (22.3 MJ/kg) comped with 19.4 MJ/kg fo the Fee Stte col. These esults compe well with the dt supplied by the Deptment of Minels nd Enegy fo these two w cols27. BET sufce e esults The sufce e esults fo the ctivted cbons peped fom both the Witbnk Sem 4 col nd the Fee Stte col e gphiclly depicted in Figue 2. Befoe expeimenttion commenced on the Fee Stte w col, it ws decided to ssess the finl ctivted cbon poduct only t n ctivtion time of 2 nd 3 hous, since the esults fom the Witbnk Sem 4 w mteil showed tht vey low sufce es wee obtined t n ctivtion time of 1 hou (4 10 m2/g). It cn be obseved fom Figue 2 tht the sufce es fo the Witbnk sem 4 cbons genelly incesed with incesing ctivtion tempetue nd ctivtion time. At tempetue of 600 C the sufce e ws 4.7m2/g fte 1 Figue 2 Sufce e (m2/g) s function of ctivtion tempetue fo the Witbnk Sem 4 cbon (W) nd the Fee Stte cbon (FS) 40 JANUARY 2012 VOLUME 112 The Jounl of The Southen Aficn Institute of Mining nd Metllugy

5 The peption of ctivted cbon fom South Aficn col hou of ctivtion. Afte 2 hous of ctivtion (t 600 C) the sufce e incesed to 41.7 m2/g, nd finlly to 176 m2/g fte 3 hous of ctivtion. When the tempetue ws incesed to 800 C, the sufce e incesed fom 9.8 m2/g fte 1 hou of ctivtion to m2/g nd m2/g fte 2 nd 3 hous of ctivtion time espectively. This incese in the sufce e is lso n indiction of the quntity of dsoption sites tht e ceted with incesing ctivtion time nd tempetue. The effect of the lge quntity of dsoption sites will be discussed with efeence to phenol dsoption in the following section. The sufce e mesuements obtined fo the ctivted cbon smples peped fom Fee Stte col exhibit the sme tend s the Witbnk sem 4 ctivted cbon smples, i.e. n incese in the ovell sufce e is obseved with n incese in ctivtion time nd tempetue. At tempetue of 600 C nd n ctivtion time of 2 hous, the sufce e ws 44 m2/g fo the Fee Stte cbon. Howeve, t highe tempetue (800 C) nd ctivtion time (3 hous), the Fee Stte ctivted cbon sufce e decesed fom 190 m2/g (2 hous) to m2/g, this decese ws not obseved in the cse of the Witbnk Sem 4 ctivted cbons. Pevious studies28 30 on the influence of minels in col on gsifiction nd ectivity hve shown tht highe minel content inceses the vege density, nd deceses the vilble sufce e nd poosity of the col pticles. Duing the heting of col, vitinites nd ll othe ective mcels soften, nd fte while degsify. The elese of gsses cetes poes, nd s these gses incese in volume, the wlls soften nd expnd. This cuses the mteil to incese in volume nd sufce e. The decese in sufce e t highe tempetues nd ctivtion time fo the Fee Stte cbon cn possibly be explined by the fct tht the highe density cols (5% highe sh content thn fo the Witbnk sem 4 col) tend to fom thick-wlled dense chs26 28 with low sufce e. The stndd Noit RO 0.8 ctivted cbon ws found to hve sufce e of m2/g. It is cle tht the highest sufce es obtined fo the ctivted cbons peped fom Witbnk Sem 4 col (338 m2/g) nd fo the Fee Stte col (181.7 m2/g) do not meet the sufce e equiement when comped to tht of Noit RO 0.8. Phenol dsoption esults Figue 3 shows the initil phenol dsoption esults (ppm/min) which wee obtined fo the diffeent ctivted cbon smples peped fom the Witbnk Sem 4 w col. In these esults the initil phenol dsoption te incesed with ctivtion tempetue nd ctivtion time. Futhemoe, the dsoption te incesed fom 4.7 to 8.9 ppm/min fo cbons peped t 600 C nd 800 C nd n ctivtion time of 1 hou. When the ctivtion time is futhe incesed to 2 hous, the dsoption te incesed fom 4.4 to 17.2 ppm/min within the sme tempetue nge. Afte 3 hous of ctivtion, the dsoption te incesed even futhe, i.e. fom 5.6 to 22 ppm/min t tempetues of 600 C nd 800 C espectively. Figue 4 shows the phenol dsoption esults obtined fo the diffeent ctivted cbon smples peped fom Fee Stte col. The te t which the Fee Stte ctivted cbon dsobed phenol (20.5 ppm/min) ws simil to tht of Witbnk sem 4 ctivted cbon (22.0 ppm/min). When the ctivtion tempetue nd time e incesed, the phenol dsoption te inceses up to the point whee mximum loding occus. Thee is thus eltionship between the BET sufce e (Figue 2) nd phenol dsoption te (Figues 3 4), i.e. highe sufce e esults in highe phenol dsoption te. When the phenol dsoption tes fo Witbnk sem 4 ctivted cbon e comped to Noit RO 0.8 (27.8 ppm/min), the Witbnk sem 4 ctivted cbon smple, J o u n l P p e Figue 3 Phenol dsoption te (ppm/min) s function of ctivtion tempetue fo the Witbnk Sem 4 cbon The Jounl of The Southen Aficn Institute of Mining nd Metllugy VOLUME 112 JANUARY

6 The peption of ctivted cbon fom South Aficn col Figue 4 The phenol dsoption te (ppm/min) s function of ctivtion tempetue fo the Fee Stte cbon (FS) Figue 5 ph mesuements Witbnk sem 4 ctivted cbon (peped t 800 C nd 3 hous) showed the best esemblnce (22.0 ppm/min). Desoption fo the espective smples ws not evident, since phenol loding onto the totl cbon sufce occued to the extent whee ll dsoption sites e occupied. Activted cbon ph. esults Figues 5 nd 6 show the mesued ph vlues obtined fo the Witbnk sem 4 cbon nd Fee Stte cbon smples espectively. All the col-deived cbons chnged the ntue of the wte to bsic duing the ph nlysis. Fust nd Aly31 found tht when n H-type ctivted cbon is poduced (ctivted t tempetues bove 650 C nd exposed to stem o CO 2 ), it is hydophobic in ntue nd tends to tke on positive chge by dsobing the H+-ions when immesed in wte (most of the sufce oxides pesent e bsic in ntue). On the othe hnd, the L-type cbon bsobs the hydoxyl (OH ) ions when immesed in wte nd the sufce oxides fomed e cidic in ntue. Thus, the H-type cbon behviou cn clely be seen fo the ctivted cbons tht wee peped fom both the Witbnk Sem 4 nd Fee Stte w mteil, s well s fo the stndd Noit RO 0.8 ctivted cbon. Tbles II V show the clculted initil dsoption nd finl desoption tes fo ll of the col-deived ctivted cbon smples. Consideing the ph esults obtined fo the Noit RO 0.8 contol smples (initil dsoption te of 0.802, nd desoption te of ), the im is to hve high H + dsoption te, nd theefte constnt ctivted cbon/wte ph within the given time limit. It is noted tht thee e no fixed eltionships between the mesued ph esults nd the ctivtion tempetue nd time. It cn lso be obseved tht the ph te esults of the Fee Stte ctivted cbon nd Witbnk sem 4 ctivted cbons e simil with egds to the initil dsoption tes nd finl desoption tes. 42 JANUARY 2012 VOLUME 112 The Jounl of The Southen Aficn Institute of Mining nd Metllugy

7 The peption of ctivted cbon fom South Aficn col J o u n l P p e Figue 6 ph mesuements Fee stte ctivted cbon Tble II Witbnk Sem 4 initil dsoption tes (ph/min) Witbnk Sem 4 1 h 2 h 3 h 600 C C C Tble IV Fee Stte initil dsoption tes (ph/min) Fee Stte 2 h 3 h 600 C C C Tble III Witbnk Sem 4 finl desoption tes (ph/min) Witbnk Sem 4 1 h 2 h 3 h 600 C C C Tble V Fee Stte finl desoption tes (ph/min) Fee Stte 2 h 3 h 600 C C C Concluding emks Duing this investigtion, ctivted cbon ws peped fom two diffeent types of South Aficn col. An ctivtion method ws chosen nd ctivted cbon smples wee peped t diffeent tempetues nd ctivtion peiods. The ctivted cbons wee chcteized ccoding to BET sufce e, ph, nd phenol dsoption, the esults comped to the Noit RO 0.8 contol smple. Although the sufce e mesuements did not compe well with tht of the contol smple, ph nd phenol dsoption studies of the peped ctivted cbons poved tht they exhibit the sme dsoption chcteistics. The BET sufce e esults tht wee obtined fo the ctivted cbon smples peped fom the Witbnk Sem 4 col smples, peped t the lowe ctivtion tempetue (600 C) nd ctivtion time (1 hou) indicted vey low sufce es (ppoximtely 5 m2/g). Smples peped t highe tempetues (800 C) nd longe ctivtion times (3 hous) hd highe sufce es (ppoximte 340 m2/g). Theefoe it cn be concluded tht fo the Witbnk Sem 4 col, highe ctivtion time nd tempetue will esult in ctivted cbon poduct hving highe sufce e. The highest sufce e tht could be obtined fo the Fee Stte w col ws the smple ctivted t 800 C nd 2 hous, which esulted in BET sufce e of ppoximtely 190 m2/g. The conclusion egding the effect of ctivtion time nd tempetue is thus not simil to the cse of the Witbnk Sem 4 ctivted cbon, whee high ctivtion tempetues nd ctivtion time delive smple with high BET sufce e. When the bove esults e comped with sufce e esults obtined fo the Noit RO 0.8 contol smple (757 m2/g), it cn be seen tht only the ctivted cbon peped fom the Witbnk Sem 4 w mteil coesponded well. Fom the esults obtined fom phenol dsoption studies fo the Witbnk Sem 4 ctivted cbon, it ws found tht thee is stong eltionship between the extent to which the smple ws ctivted (ctivtion time nd tempetue) nd phenol dsoption chcteistics. With incesing ctivtion time nd tempetue, n incese in the mount of phenol dsobed is ppent. Simil dsoption esults wee obtined when the Witbnk Sem 4 ctivted cbon The Jounl of The Southen Aficn Institute of Mining nd Metllugy VOLUME 112 JANUARY

8 The peption of ctivted cbon fom South Aficn col dsoption esults wee comped to those obtined fo the Noit RO 0.8 ctivted cbon. The initil dsoption esults fo the ctivted cbon peped t 800 C fo 3 hous showed the closest esemblnce to the dsoption chcteistics of the Noit RO 0.8 ctivted cbon. The eltionship between BET sufce e nd phenol dsoption cn lso be seen in the ctivted cbons peped fom the Fee Stte col. With incesing ctivtion time nd tempetue, n incese in the mount of phenol dsobed is obseved. When these esults wee comped to the dsoption esults fom the Noit RO 0.8 ctivted cbon, simil tends e obseved. The ctivted cbon peped t 800 C nd 2 hous hd the highest dsoption te. This specific smple lso hd on vege highe BET sufce e comped to the othe Fee Stte ctivted cbon smples. Fom the ph mesuements it cn be concluded tht both the Witbnk sem 4 w mteil nd the Fee Stte w col yielded n H-type ctivted cbon which coesponds well with wht the litetue pedicts. The Witbnk Sem 4 ctivted cbon ph comped well with the contol cbon, but fo the Fee Stte cbon, the vlue decesed fte the mximum solution ph hd been eched. Futhe studies should focus on mnufctuing ctivted cbon fom South Aficn col, pplying it fo dsoption, nd exploing wys in which the ctivted cbon cn be successfully ectivted fo epeted use in n dsoption pocess. South Aficn col lso inheently contins lge mount of minel mtte. It cn be seen tht this figue is s high s 35% (fom the poximte nlysis of Fee Stte col). Methods should be exploed to detemine if eduction in sh content of South Aficn col cn delive n ctivted cbon with enhnced dsoption popeties comped to those of col without sh eduction. A Fouie tnsfom infed spectoscopy (FTIR) nlysis of the ctivted cbon smple cn detemine the functionl goups on the sufce of the cbon. This should be incopoted into futue studies to help to bette explin the dsoption behviou of the ctivted cbon s shown by ph mesuements nd phenol dsoption studies. Key chcteistics tht influence the suitbility of ctivted cbon fo use in poduction plnt i.e. hdness (dubility), pticle shpe (impotnt fo sceening), nd potentil fo fouling by ognics should lso be consideed in futue studies. Refeences 1. SNELL, F., HILTON, C. nd ETTRE, L. Encyclopedi of Industil Chemicl Anlysis, vol. 8. InteScience, New Yok, pp. 2. KIRK, R. nd OTHMER, D. Encyclopedi of chemicl technology, vol. 4. InteScience, New Yok, ALMANSA, C., MOLINA-SABIO, M., nd RODRIGUEZ-REINOSO, F. Adsoption of methne into ZnCl 2 -ctivted cbon deived discs. Micopoous nd Mesopoous Mteils, vol. 76, pp LORENC-GRABOWSKA, E., GRYGLEWICZ, G., nd GRYGLEWICZ, S. Development of mesopoosity in ctivted cbons vi col modifiction using C- nd Fe-exchnge. Micopoous nd Mesopoous Mteils, vol. 76, pp BANDOSZ, T. Effect of poe stuctue nd sufce chemisty of vigin ctivted cbons on emovl of hydogen sulphide. Cbon, vol. 37, pp DASTGHEIB, S. nd ROCKSTRAW, D. 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Fuel, vol. 78, pp HULSTON, J., CHAFFEE, A.L., BERGINS, C., nd STRAUSS K. Compison of physico-chemicl popeties of vious lignites teted by mechnicl theml expession. Col Peption, vol. 25, no. 4, pp LI, Y., LU, G.Q. nd RUDOLPH, V. Compessibility nd fctl dimension of fine col pticles in eltion to poe stuctue chcteistion using mecuy Poosimety. Pticle nd Pticle Systems Chcteiztion, vol. 16, pp FAUST, S.D. nd ALY, O.M. Chemisty of wte tetment. Buttewoth, Boston, pp. 26. PINHEIRO, H.J. A techno-economic nd histoicl eview of the South Aficn col industy in the 19th nd 20th centuies nd nlyses of col poduct smples of South Aficn collieies Bulletin 113. South Aficn Bueu of Stndds, Petoi, pp. 44 JANUARY 2012 VOLUME 112 The Jounl of The Southen Aficn Institute of Mining nd Metllugy