Separation and Purication Technology 74 (2010) 213218

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Activat ing

Edward L Ma Department o , Cleab School of Che dney, N

a r t i c l

Article history:Received 12 JaReceived in reAccepted 4 Jun

Keywords:BambooAdsorptionActivationElementsMicropore

eparethreeating) andporetweem2/go andatio esopo

1. Introdu

Bamboo is a large, woody-grasses member of the family ofBambusoideae encompassing about 1250 species within 75 generaworldwide [1]. Primarily carbon and oxygen (over 90% by weight),bamboo has a variety of applications such as construction and rein-forcing bre

In Hongbuilding facwas estimafrom constrAs they arefolding is clneither reclsolutions toproduct suc

There arsors for actsuch as coamers [6,7]straw [9], pchemical acsalts (e.g. Zreported, fesuch as HC

CorresponE-mail add

preelemental composition remains unclear. The present study differsfrom phosphoric acid, the three selected acids are not only Lewisacids but also powerful oxidants (e.g. HNO3 and H2SO4) and dehy-drating agents (e.g. H2SO4) so that it providesmore information onthe role of chemicals in the activation process for lignocellulosic

1383-5866/$ doi:10.1016/j.s, papers, textiles and boards, food and fuels [1,2].Kong, bamboo is widely used in building construction,ades, wall repairs, decoration and sign erection [2]. Itted that 7500 tonnes of bamboo waste were generateduction and demolition (C&D) operations every year [3].often contaminated by other materials, bamboo scaf-assied as comprising soft non-inertmaterials such thatamation nor recycle is feasible [4]. One of the possiblethis kind of waste is to convert them to a value-addedh as activated carbon for wastewater treatment [5].e many organic materials that can serve as precur-ivated carbons, ranging from conventional materialsl, wood or coconut shell to natural or synthetic poly-and biomass waste such as oil palm shells [8], wheataper-mill sludge [10] and olive residues [11]. Althoughtivation method using phosphoric acid [12] or mineralnCl2, [13]) as activating agents have been extensivelyw studies on activated carbons from common acidsl, HNO3 and H2SO4 were found. The effectiveness of

ding author. Tel.: +852 2358 8412; fax: +852 2358 0054.ress: kemckayg@ust.hk (G. McKay).

materials. This study aims to prepare activated carbons fromwastebamboo scaffolding impregnatedwith thesemineral acids, and fur-ther correlate their physical and chemical characteristics with theproduction parameters.

2. Experimental

2.1. Production of activated carbons

Ten grams of dried bamboo (500710m) were mixed withthree concentrated acids, namely, hydrochloric (37%, w/w), nitric(70%, w/w) and sulphuric (98%, w/w). The impregnation ratio (i.e.the mass ratio between bamboo and acid) was xed at 1 and 4.Themixture was stirred until fuming ceased, then dried in amufefurnace at 378K for overnight.

The mixture was heated to 773, 973 and 1173K in the muf-e furnace (12/75/700, Carbolite) at the heating rate of 5K/minunder owing nitrogen (purity 99.99%). Once the set temperaturehas been reached, the sample was held isothermally for 14h thencooled to 378K. The sample was immersed in deionised water(500mL) with stirring for overnight, ltered by glass-bre mem-brane (GC-50, diameter 45mm, Advantec) and repeatedly ushedwith deionised water until the ltrate pH approached 5.5. After

see front matter 2010 Elsevier B.V. All rights reserved.seppur.2010.06.007ed carbons from bamboo scaffolding us

.K. Muia, W.H. Cheunga,b, Marjorie Valixb, Gordonf Chemical & Biomolecular Engineering, Hong Kong University of Science & Technologymical & Biomolecular Engineering, Chemical Engineering Building J01, University of Sy

e i n f o

nuary 2010vised form 4 June 2010e 2010

a b s t r a c t

A series of activated carbons were prH2SO4. Unlike phosphoric acid, thesecellulosic materials. The effect of oper(the mass ratio between bamboo/acidevaluated for the yield, surface area,impregnation ratio (the mass ratio beandmicropore volume as high as 553vating agent. Lower impregnation ratiarea while increasing impregnation rto the transformation of micro- to menitrogen and sulphur.

ction such im/ locate /seppur

acid activation

cKaya,

r Water Bay, Kowloon, Hong Kong SAR, ChinaSW 2006, Australia

d from bamboo by chemical activation with HCl, HNO3 andacids are not commonly used as an activating agent for ligno-variables such as activation temperature, impregnation ratioholding time were investigated. The resultant carbons weresize distribution, pH, elemental composition and ash. At ann bamboo/acid) of 1, activated carbon with BET surface areaand 0.239 cc/g was obtained at 1173K using H2SO4 as an acti-shorter holding timewere favourable to the yield and surfacenhanced mesoporosity of the carbons. This can be attributedres in the presence of higher basic element contents such as

2010 Elsevier B.V. All rights reserved.

gnation in terms of textural characteristics as well as

214 E.L.K. Mui et al. / Separation and Purication Technology 74 (2010) 213218

Table 1Effect of temperatureon theyieldandsurfaceareaofbamboocarbons (impregnationratio =1).

Acid Temperature (K) Yield (%) SBET-N2 (m2/g) Sabsolutea (m2/100g)

HCl 79

11

HNO3 79

11

H2SO4 79

11

a Sabsolute = Y

drying there-weighed

2.2. Charac

2.2.1. SurfaThe surf

gen sorptioThe total sufrom the Bmesopore vthe total po0.96) and ththe determ

2.2.2. ElemThe elem

mine the caof the sampcombustionthe modiecontent is dposition plu

2.2.3. pHAmodi

to determinadded to 10for anotherlter paper3235K w

3. Results

3.1. Yield

Temperaand producperature, athe absolutimpregnatioptimum arvation temp

Fig. 1 shnation ratiotrend thatless of theratio of 1, twhich chanfrom 1 to 4

Fig. 1.

ternimprecausthe h.7%.en thpregnated carbons decreased from 23.8% to 18.3% as theg time varied between 1 and 4h. ForHNO3-impregnated car-ncreasing the holding time reduced the yield from 13.7% to

low yield of carbons obtained from using HNO3 as an acti-agent (none of the carbons have yields higher than 15%) canibuted to the reaction between concentrated nitric acid andmboo components, cellulose and hemicellulose, whichwereted to a highly reactive product known as cellulose nitrite]

5 +3HNO3 C6H7(NO2)3O5 +3H2O (1)2 is the derivative thermogram of HNO3-impregnated bam-d demonstrates the rapid reaction occurring at temperatureof ca. 523 and 623K, when the impregnation ratio was 1.the impregnation ratio was increased to 4, the peak decom-73 38.1 183 697273 27.6 366 10,10273 23.4 482 11,289

73 37.5 151 566373 21.5 152 326873 19.9 295 5871

73 26.5 399 10,57473 22.4 466 10,43873 21.1 554 11,689

ield SBET-N2 100.

washed carbon in an oven at 378K, the carbon wasand taken as product.

terisation of activated carbons

ce area and pore volumeace area and pore volume were determined by nitro-n at 77K in the surface analyser (SA-3100, Coulter).rface area and micropore volume can be determinedET- and t-plot method, respectively [14] whereas theolume can be determined by the difference betweenre volume (volume of nitrogen adsorbed at the P/Po e micropore volume. The Kelvin equation was used forination of pore size distribution [14].

ental composition and ash contentental analyser (Vario EL III, Varian) was used to deter-rbon, hydrogen, nitrogen and sulphur (CHNS) contentsle. The ash content of the sample was determined byin a mufe furnace (925K, 4h) in accordance with

d standard test method ASTM D2866-04 [15]. Oxygenetermined by the difference between elemental com-s ash.

ed ASTM standardmethod D3838-99 [15] was adoptede the pH of the sample. One gram of dried sample wasmL of boiling deionised water. The slurry was boiled15min in a sealed tube and ltered by pre-moistened(Whatman #2, 110mm diameter). The ltrate pH atas taken as the sample pH.

and discussion

ture is one of the major parameters affecting the yieldt quality of the carbons. To evaluate the effect of tem-

lar patHNO3-time bWhenonly 7

WhHCl-imholdinbons, i6.6%.

Thevatingbe attrtwo baconver[16,17

C6H10O

Fig.boo anrangeWhenbasis of 100 grams of carbon was used in estimatinge surface area that is generated in the carbon at theon ratio of 1. The result is presented in Table 1. As shownea generation is achieved at 1173K, therefore the acti-erature was set at that point.ows the yields of activated carbons with two impreg-s (Xp =1 and 4). The yield of carbons all exhibited theyield decreased with increasing holding time, regard-acid used or impregnation ratio. At the impregnationhose HCl-impregnated carbons showed a higher yieldged from 24.6% to 22.6% as the holding time increasedh. The H2SO4-impregnated carbons exhibited a simi-

positionocctemperaturthe yield w

It appeaatively con12.0% even4. When thto 8.0%. Suctive natureresulted inlignin) withface. The reYields of activated carbons from acid-impregnated bamboo.

that decreased at a higher rate from 23.3% to 15.0%. Theegnated carbons appeared very sensitive to the holdinge a sharp drop in yield between 2 and 3hwas observed.olding timewas extended to 4h, the yield of carbonwas

e impregnation ratio was increased to 4, the yield ofurredateven lower temperature (ca. 500K).At elevatede cellulose and its nitrite were removed quickly so thatas greatly reduced.rs that the yield of H2SO4-impregnated carbons is rel-centration-dependent. The yield was found as low asthe holding time was 1h at the impregnation ratio ofe activation was extended to 4h, the yield was reducedh a big difference can be attributed to the strong oxida-of H2SO4. Increasing the impregnation ratio from 1 to 4thorough breakdown of bamboo components (such asthe formation of oxygen complexes over residue sur-

latively open porous structure of the residue combined

E.L.K. Mui et al. / Separation and Purication Technology 74 (2010) 213218 215

Fig. 2. Derivatrate: 5K/min).

Fig. 3. Nitroge

with increaatoms and c

In generon the holdis also conHCl-impregcarbons imp

3.2. Surface

3.2.1. SurfaFig. 3 sh

boo carbonisotherms cthe relativemicroporoumesopore b

Table 2treated witthe highestclear that psurface areaquently sea

The effeshowed a dbons. In thewith the hoarea of 463burn-off totrend wasbonised prestructure encontinuous

Using HNwere found

Table 2Surface area and pore volume of bamboo carbons.

Acid Impregnationratio

Time(h)

Vmic(cc/g)

Vmes(cc/g)

Smic(m2/g)

Smes(m2/g)

SBET-N2(m2/g)

1 1 0.166 0.021 362 16 3782 0.214 0.026 463 19 4823 0.181 0.043 385 35 4204 0.168 0.046 366 34 400

4 1 0.173 0.054 369 37 4062 0.220 0.038 472 27 4993 0.171 0.036 383 14 3974 0.170 0.049 361 37 398

1

4

1

4

m2/gin thacidmiceatedmponentmo

of ligive thermogram of HNO3-bamboo mixture under nitrogen (heating

n isotherms of three acid-impregnated bamboo carbon (Xp = 1).

sed oxygen complexes promoted the removal of carbononsequently lowered the yield of carbons.al, the yield of carbons is predominantly dependenting time and acid used. Increasing impregnation ratiosidered to have a negative effect on the yield. Thenated carbons have higher yields compared with otherregnated by HNO3 or H2SO4.

HCl

HNO3

H2SO4

to 359tionednitricand heat elevlosic cocompoopeneddownarea and pore size distribution

ce areaows a typical isotherm of three acid-impregnated bam-s activated at 1173K under nitrogen. They are Type Iharacterised by a plateau which is nearly horizontal aspressure increased, showing that the solid is primarilys [14]. The narrow hysteresis suggests the presence ofut this has limited contribution to the overall porosity.compares the surface area development of bambooh various acids. As shown sulphuric acid demonstratedsurface areas at the impregnation ratio of 1. It is alsorolonged activation periods appear to result in lowerowing to the excessive burn-off of carbon that conse-

led off the pores at the surface.ct of holding time on the micropore surface area (Smic)ecreasing trend in HCl- and H2SO4-impregnated car-case of HCl-impregnated carbons, the Smic increased

lding time from 1 to 2h, reached the maximum surfacem2/g at that point, then decreased with the extent of366m2/g. For H2SO4-impregnated carbons, a similarobserved that can be attributed to the partially car-cursors prior to activation, which the relatively poroushanced the carbon burn-off and decreased surface arealy from 507m2/g at 1h to 337m2/g at 4h.O3 as an activating agent, the micropore surface areasto be increased with the holding time from 169m2/g

For carbratios produtimes at the4, the micrfrom 1 to 2impregnatethe holdingof two carbIn the caseincreased sarea (346mat a holdinga portion oeven sealedcontinuous

Owing tH2SO4, theand tabulatratio has limgradual dec

Table 3Textural chara

Impregnatio

1241 0.079 0.025 169 15 1832 0.126 0.026 272 23 2953 0.162 0.023 352 18 3704 0.167 0.052 359 42 401

1 0.117 0.026 248 22 2702 0.219 0.069 411 78 4883 0.146 0.087 310 65 3754 0.113 0.043 242 34 276

1 0.236 0.045 507 42 5492 0.239 0.045 514 39 5533 0.226 0.033 487 26 5134 0.158 0.040 337 31 368

1 0.090 0.047 189 38 2262 0.108 0.044 234 35 2693 0.161 0.046 346 37 3834 0.140 0.118 298 77 375

as the holding time varied between 1 and 4h. As men-e previous section, the reaction between concentratedand bamboo converted components mainly cellulosellulose to reactive cellulose nitrite which is removedtemperatures. The initial decomposition of these cellu-nentsallowedbetterdecompositionof anotherbamboo, lignin, after the removal of cellulose nitrite, because itre pores for the release of volatiles during the break-nin bonds.ons activated with HCl and HNO3, higher impregnationced carbons with better porosity using shorter holding

expense of lower yields. At the impregnation ratio of

opore surface areas rst increased with holding timeh and the maximum surface areas for HCl- and HNO3-d carbonswere 472m2/g and 411m2/g, respectively, attime of 2h. Beyond that point the micropore volumesons collapsed, leading to the decline in surface area.of H2SO4-impregnated carbons, micropore surface areateadily with the holding time. The maximum surface2/g) and micropore volume (0.161 cc/g) were obtainedtime of 3h then dropped to 298m2/g at 4h, showing

f micropores transformed to meso- or macropores oroff as a result of the collapse of pore walls with theremoval of carbon atoms.o the higher surface area of carbons activated witheffect of impregnation ratio was further investigateded in Table 3. It appears that increasing impregnationited effect to the pore development but resulted in aline in surface area and micropore volume. When the

cteristics of activated carbons from H2SO4-impregnated bamboo.

n ratio (Xp) SBET-N2 (m2/g) Vmic (cc/g) Vmes (cc/g)

554 0.238 0.045310 0.120 0.034268 0.108 0.044

216 E.L.K. Mui et al. / Separation and Purication Technology 74 (2010) 213218

Fig. 4. Pore sibamboo.

impregnatirather thanthe reductienlargemenXp =4), in wvolume weenlarged tolower imprmicroporos

3.2.2. PoreFig. 4 i

impregnateDependingferently widecreasewipeaks in thsite trend wtime. This cenhanced mpores. Similcoal [18] an

Carbonstion of acidvolumes inclation enhanarrow peawas furtherdiminishing

A comp(holding timFor carbons

ore sient im

itedar treze distribution of activated carbons from acid-impregnated (Xp = 1)

on ratio was raised to 2, the widening of existing poresopening of new pores occurred which is reected in

Fig. 5. Pat differ

has lima similon of surface area and micropore volume. Such poretproceededwith the increaseof impregnation ratio (i.e.hich the micropore volume decreased but mesopore

nt up again where part of the micropores were furthermesopores. Based on this observation it appears thategnation ratio, for example, Xp =1, is favourable to theity development as well as surface area.

size distributionllustrates the pore size distribution of three acid-d bamboo carbons at the impregnation ratio of 1.on the acid used, the pore size distribution varied dif-th time. For HCl, the micropore volume was found toth the holding time. It can be seen from the diminishinge micropore region from 1 to 4h. For HNO3, an oppo-as observed that the micropore volume increased withan be attributed to the acid intercalation effect whichicropore structure rather than widening the existingar phenomenon have been reported in acid-pretreatedd bagasse [19].from H2SO4-impregnated bamboo involve a combina-intercalation and pore enlargement. The microporereased steadily from1 to 2h duringwhich acid interca-nced the porosity development as shown in the sharp,ks at diameter around 0.7nm. When the holding timeextended to 4h, existing pores collapsed that led topeaks as well as the drop in micropore volume.

arison between carbons at two impregnation ratiose: 2h) on the pore size distribution is shown in Fig. 5.activatedwithHCl, increasing theamountof acid added

With onratio of 4 exthose produnation ratioto the formburn-off ofimpregnatiThe situatioratio affecteadditional HAs shown insubstantialaround 0.7these peaks

Summartive to thesurface areacids used,at both low

3.3. Elemen

Table 4carbons preent acids.

Regardlewas found tcarbon in pcontent ofalso decreaze distribution of activated carbons from acid-impregnated bamboopregnation ratios (holding time: 2h).

effect on the micropore volume (as both curves follownd) but it is advantageous in enhancing mesoporosity.

e exception at 3h, all HCl-impregnated carbons in thehibited higher mesopore volumes in comparison withced in the ratio of 1. In the case ofHNO3, higher impreg-enhanced themesoporosity of carbons that can be dueation of nitrogen-oxygen complexes that catalysed thecarbon. This can be seen from the smooth curve at theon ratio of 4 at pore diameters around 0.9 and 1.1nm.n is different in H2SO4-carbons as the impregnationdmicroporosity rather thanmesoporosity. It is because2SO4 added resulted in excessive burn-off of carbon.Fig. 5c, lower ratio (i.e. Xp =1) produced active carbons

ly microporous which featured in peaks at diametersand 0.95nm. When the impregnation ratio increased,diminished and revealed the collapse of micropores.ising, increasing impregnation ratio is considered effec-mesopore development but may be detrimental to thea due to the collapse of micropores. Amongst all theH2SO4 is considered superior in developing mesoporesand high impregnation ratios.

tal composition

demonstrates the elemental composition of activatedpared at 1173K from bamboo impregnatedwith differ-

ss of the acid used, the carbon content of all sampleso decrease with the holding time due to the burn-off ofrolonged activation at high temperature (1173K). Theheteroatoms such as nitrogen, hydrogen and sulphur,sed with time for the same reason. Oxygen, however,

E.L.K. Mui et al. / Separation and Purication Technology 74 (2010) 213218 217

Table 4Elemental composition and pH of bamboo carbon.

Acid Impregnation ratio Time (h) Elemental composition (wt.%) Ash (wt.%) Basic elementsN + S (wt%)

Acidic elementsH + Oa (wt%)

pH

N C S H Oa

HCl 1 3334

4 2255

HNO3 1 568

14

4 11111313

H2SO4 1 2335

4 8111216

a Oxygen co

exhibited athe form of

Whenustion ratio inmineral imthe volumereleased frchloride), pthat increas

Using Htal composway that hitent. For HNdecreased ffrom 1 to 4hbon contentime interv(2.863.34%presence ofcarbon burnH2SO4. Whholding timcontent fromered to thewas increasbiomass cowhen the a[20] pointe3-D structuconcentratiburnt-off caacid and bio

[CnHxOy] +

s alsoeralrepapHin nto inores imre [21 0.68 83.62 0.41 1.37 10.482 0.67 80.67 0.21 1.29 13.383 0.53 78.72 0.01 1.24 15.644 0.45 74.64 0.01 1.35 18.81

1 0.82 88.02 0.24 1.97 8.952 0.56 82.72 0.12 1.66 14.943 0.54 79.91 0.12 1.63 17.804 0.47 78.79 0.07 1.59 19.08

1 3.34 77.47 0.19 1.54 11.732 3.08 75.82 0.18 1.29 13.563 2.91 67.52 0.01 1.28 19.734 2.86 67.05 0.01 1.27 14.80

1 3.07 67.25 1.09 1.36 15.762 2.39 65.74 0.74 1.32 17.923 2.37 62.88 0.52 1.28 19.344 2.11 62.25 0.49 1.22 20.05

1 0.39 76.96 0.50 2.01 17.192 0.67 75.32 0.84 1.92 18.203 0.81 74.98 0.92 1.87 17.664 0.80 71.68 2.27 1.66 18.19

1 1.81 69.51 2.24 1.24 16.292 1.56 64.82 2.40 1.22 18.693 1.49 64.27 2.40 1.22 17.774 0.88 61.83 2.36 1.21 17.42

ntent determined by difference.

n opposite trend owing to the formation of oxides inash following the removal of carbon atoms.ingHCl as an activating agent, increasing the impregna-creased the carbon content because the HCl removedpurities that retarded the carbon burn-off. The higherof HCl added the more the catalytic minerals were

om the carbon matrix (possibly forming soluble metalreventing the direct contact betweenmetals and carboned the burn-off in prolonged activation.

Thiare genbons p

The1173Ktendedwere mcarbonliteratuNO3 as activating agent exhibited different elemen-ition at different impregnation ratios. It behaves in agher the impregnation ratio, the lower the carbon con-O3 at the impregnation ratio of 1, the carbon content

rom 77.47% to 67.05% when the holding time increased.When the impregnation ratio was raised to 4, the car-

t decreased from 67.25% to 62.25% in the same holdingal. Combined with the relatively high nitrogen contentat Xp =1; 2.113.07% at Xp =4), this suggests that theoxidative nitrogen-oxygen complexes enhanced the-off. A similar pattern can be observed in the case ofen the impregnation ratio was xed at 1, increasinge from 1 to 4h resulted in a slow decrease in carbon76.96% to71.68%. Thecarboncontentwas further low-

range of 69.51% to 61.83% when the impregnation ratioed to 4. This suggests amore vigorous reaction betweenmponents (mainly hemicellulose, cellulose and lignin)mount of acid added was increased. As Caballero et al.d out, sulphuric acid promoted the breakdown of there of lignin. Guo et al. [21] further suggested that highon of sulphuric acid may lead to surplus of H2O thatrbons at elevated temperature. The reaction betweenmass component is expressed as [21]:

H2SO4 H2O + Selement + [CnHxOy+3] (2)

of the carbLewis baseadsorbent s

(Basicsuspe

(Acidicsusp

In summwere foundprepared bas an activalow carbonreaction beproduced athe carbon

Heteroaments), nitrshown implatter two eincreased thcharacteris

4. Conclus

Chemicabon from bH2SO4, pro.44 1.09 11.85 5.96

.78 0.88 14.67 5.51

.86 0.54 16.88 5.45

.74 0.46 20.16 5.09

.70 1.06 10.92 5.12

.79 0.68 16.60 4.94

.78 0.66 19.43 4.89

.98 0.54 20.67 4.74

.73 3.53 13.27 4.72

.07 3.26 14.85 5.11

.55 2.92 21.01 5.66

.01 2.87 16.07 5.78

.47 4.16 17.12 7.26

.89 3.13 19.24 7.41

.61 2.89 20.62 7.45

.88 2.60 21.27 7.56

.95 0.89 19.20 4.74

.05 1.51 20.12 4.42

.76 1.73 19.53 4.62

.40 3.07 19.85 5.32

.91 4.05 17.53 6.76

.31 3.96 19.91 6.65

.85 3.89 18.99 6.64

.30 3.24 18.63 6.23

explainedwhy the sulphur contents of carbons atXp =4ly over 2.2%, which is substantially higher than the car-red by HCl or HNO3 (sulphur content less than 1%).of bamboo carbons prepared at different conditions atitrogen is summarised in Table 4. Generally the pHcreasewith theamountof acidadded. It isbecause therebasic elements (i.e. nitrogen and sulphur) retained inpregnated with higher amount of acid. As suggested in224], higher nitrogen content increased the basicity

on to a certain extent which can be explained by thecharacteristics postulated in literature [19], leaving theurface positively or negatively charged:

nsion) C S+OH + H+ C S+ +H2O (3)ension) C OH+ C O +H+ (4)ary, the effects of holding time and impregnation ratiosignicant in the elemental composition of carbons

y acids regardless of the acid used. When using H2SO4ting agent, higher impregnation ratio often resulted inbut high sulphur contents. This can be attributed to thetween bamboo components and sulphuric acid, whichsurplus of water and sulphur (Eq. (2)) that promotedconversion.toms such as hydrogen, oxygen (both are acidic ele-ogen and sulphur (both are basic elements), have beenortant to the pH of bamboo carbons, particularly thelements, which higher nitrogen and sulphur contentse overall basicity of carbons because of the Lewis base

tics.

ions

l activation process was used to prepare activated car-amboo. Three commonly used acids, HCl, HNO3 andduced activated carbon having well developed porosi-

218 E.L.K. Mui et al. / Separation and Purication Technology 74 (2010) 213218

ties. It was found that carbons generally had higher microporearea at the activation temperature of 1173K in lower impregna-tion ratio (e.g. Xp =1) and shorter holding time (e.g. 2 h). Comparedwith HCl and HNO3, H2SO4 has shownmore effective in the devel-opment of microporosity. Increasing impregnation ratio, however,wasexpected toproducecarbonswithhigherpHandmesoporosity.

Acknowledgements

The authors are grateful to the Research Grant Council (RGC)and Green Island Cement (GIC) for providing the nancial supportfor this research project.

References

[1] J.M.O. Scurlock, D.C. Dayton, B. Hames, Bamboo: an overlooked biomassresource? Biomass Bioenergy 19 (2000) 229244.

[2] P.Y. Wong, Safety and reliability of bamboo scaffolding, M.Phil. Thesis, HongKong University of Science & Technology, Hong Kong SAR, 2002.

[3] C.S. Poon, A.T.W. Yu, L.H. Ng, On-site sorting of construction and demolitionwaste in Hong Kong, Resources Conserv. Recycl. 32 (2) (2001) 157172.

[4] Environmental Protection Department, Monitoring of Solid Waste in HongKong Waste Statistics for 2007, Environmental Protection Department, HongKong SAR, 2007.

[5] A.W.M. Ip, J.P. Barford, G. McKay, Production and comparison of high sur-face area bamboo derived active carbons, Bioresources Technol. 99 (18) (2008)89098916.

[6] E.L.K. Mui, D.C.K. Ko, G. McKay, Production of active carbons from waste tyres a review, Carbon 42 (2004) 27892805.

[7] H. Marsh, F. Rodriguez-Reinoso, Activated Carbon, Elsevier, Amsterdam, 2006.[8] J. Guo, A.C. Lua, Adsorption of sulphur dioxide onto activated carbon prepared

from oil-palm shells with and without pre-impregnation, Sep. Purif. Technol.30 (3) (2003) 265273.

[9] R. Chand, T. Watari, K. Inoue, T. Torikai, M. Yada., Evaluation of wheat strawand barley straw carbon for Cr (VI) adsorption, Sep. Purif. Technol. 65 (2009)331336.

[10] N.R. Khalili, J.D. Vyas, W.Weangkaew, S.J. Westfall, S.J. Parulekar, R. Sherwood,Synthesis and characterization of active carbon and bioactive adsorbent pro-duced from paper mill sludge, Sep. Purif. Technol. 26 (23) (2002) 295304.

[11] N. Petrov, T. Budinova, M. Razvigorova, J. Parra, P. Galiatsatou, Conversion ofolive wastes to volatiles and carbon adsorbents, Biomass Bioenergy 32 (2008)13031310.

[12] L.S. Chan,W.H. Cheung, S.J. Allen, G. McKay, Separation of acid dyesmixture bybamboo derived active carbon, Sep. Purif. Technol. 67 (2) (2009) 166172.

[13] I. Kula,M.Ugurlu,H.Karaoglu,A.C. Celik,AdsorptionofCd (II) ions fromaqueoussolutions using activated carbon prepared fromolive stone by ZnCl2 activation,Bioresource Technol. 99 (2008) 492501.

[14] J. Rouquerol, K.S.W. Sing, Adsorption by Powders and Porous Solids: Principles,Methodology and Applications, Academic Press, San Diego, CA, 1999.

[15] ASTM, Refractories, carbon and graphite products; activated carbon, in: ASTM(Ed.), Annual Book of ASTM Standards, vol. 15.01, ASTM, Easton US, 2005,D2866-04.

[16] J. Quinchon, J. Tranchant, Nitrocelluloses: the Materials and Their Applicationsin Propellants, Explosives and Other Industries, Halsted Press, New York, 1989.

[17] J. Akhavan, TheChemistryof Explosives, Royal SocietyofChemistry, Cambridge,UK, 2004.

[18] S.B. Lyubchik, H. Benaddi, V.V. Shapranov, F. Beguin, Activated carbons fromchemically treated anthracite, Carbon 35 (1) (1997) 162165.

[19] M. Valix, W.H. Cheung, G. McKay, Roles of the textural and surface chemicalproperties of activated carbon in the adsorption of acid blue dye, Langmuir 22(10) (2006) 45744582.

[20] J.A. Caballero, A. Marcilla, J.A. Conesa, Thermogravimetric analysis of olivestones with sulphuric acid treatment, J. Anal. Appl. Pyrolysis 44 (1) (1997)7588.

[21] J. Guo, Y. Luo, A.C. Lua, R. Chi, Y. Chen, X. Bao, S. Xiang, Adsorption of hydrogensulphide (H2S) by activated carbons derived from oil-palm shell, Carbon 45(2007) 330336.

[22] Y.H. Li, C.W. Lee, B.K. Gullett, Importance of activated carbons oxygen surfacefunctional groups on elemental mercury adsorption, Fuel 82 (2003) 451457.

[23] J. Machnikowski, B. Grzyb, H. MacHnikowska, J.V. Weber, Surface chemistryof porous carbons from N-polymers and their blends with pitch, Micropor.Mesopor. Mater. 82 (12) (2005) 113120.

[24] M. Valix, W.H. Cheung, K. Zhang, Role of chemical pre-treatment in the devel-opment of super-high surface areas and heteroatom xation in activatedcarbons prepared from bagasse, Micropor. Mesopor. Mater. 116 (13) (2008)513523.

Activated carbons from bamboo scaffolding using acid activationIntroductionExperimentalProduction of activated carbonsCharacterisation of activated carbonsSurface area and pore volumeElemental composition and ash contentpH

Results and discussionYieldSurface area and pore size distributionSurface areaPore size distribution

Elemental composition

ConclusionsAcknowledgementsReferences