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The integrating of hemicelluloses pre-extraction measure prior to pulping and the subsequent alkaline pulping of the extracted residue is evaluated as the possible method to turn to mush factory biorefinery. Hemicellulose was pre-extracted from sugar cane bagasse ( SCB ) through dilute sulphuric acid or mild alkalic procedures. The effects of sulphuric acid or Na hydrated oxide concentration, temperature and clip on hemicellulose hydrolysis were studied utilizing a statistical experimental design. Xylan content of 62 % on dry mass was hydrolyzed from SCB with 0.5 % v/v H2SO4, 140 & A ; deg ; C and 60 proceedingss and 88.6 % of xylan on dry mass was extracted with 2.3M NaOH, 65 & A ; deg ; C and 180 proceedingss. Acid hydrolysis of SCB showed that, hemicelluloses can be quantitatively extracted from SCB, nevertheless subsequent sodaAQ pulping of residue reduced the mush belongingss even when little fraction of hemicellulose was extracted on the stuff. Selective hydrolysis of 11 % xylan with autohydrolysis improved the sodaAQ mush output by 2.8 % at kappa figure 20.9 compared to the control at kappa figure 22.8. The mush brightness, explosion and tear index was improved by 5.3 % , 5.0 % and 18.7 % severally. SodaAQ pulping of 73 % xylan extracted residue with alkalic methods improved the mush output by 10.8 % at kappa figure 15.5 compared to the control. The brightness of the mush was higher by 24.0 % and the tear index was superior by 56.4 % . Breaking length and the best index of the mush were reduced by 10.6 % and 9.3 % severally ; nevertheless they are in an acceptable scope. These consequences allow the extraction of a part of hemicellulose from SCB with autohydrolysis and alkaline methods prior to sodaAQ pulping owing to the betterment in physico-chemical belongingss of the mush.

Keywords: biorefinery, hemicelluloses extraction, sugar cane bagasse, sodium carbonate pulping, sodaAQ pulping, mush quality, handsheets strengths

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Introduction

Sugarcane bagasse ( SCB ) represents an alternate fibre input into the South African mush industry. Around 70 000 dozenss of uncolored and 60 000 dozenss of faded bagasse mush classs are produced per annum [ 1 ] . The sodium carbonate is the preferable method for chemical sulfurs free SCB pulping in South Africa. SCB consists about of 43 % cellulose, 25 % hemicellulose which is chiefly xylan and 25 % lignin [ 2-4 ] . In add-on to lignin, about 70 % of the hemicelluloses are dissolved in the black spirits watercourse during the cookery procedure. Presently the black spirits watercourse and their debasement merchandises are typically concentrated and combusted to bring forth the heat and power demands for the mush factory [ 5 ] . In the burning procedure, hemicellulose is underutilised sing the lower heating value of hemicellulose ( 13.6 MJ.kg-1 ) to that of lignin ( 27 MJ.kg-1 ) [ 6 ] .

Fractionation of lignocellulosic biomass into its three major constituents, cellulose hemicellulose and lignin has been proposed as the first measure of biomass refinement to high value-added merchandises [ 7, 8 ] . Within the mush factory biorefinery construct, extraction of hemicelluloses from suited biomass prior to pulping, followed by the agitation of the monomeric sugars with genetically engineered barm to bring forth bioethanol, could lend to turn to the turning biofuel demand [ 6 ] . The extracted hemicelluloses oligomers or polymers may so be used as a feedstock for paper additives, polymers and chemicals [ 9-11 ] . At the same clip, extraction of hemicelluloses enhanced mush production by bettering the overall alkaline pulping processes. Cooking clip can be reduced and cooking liquor impregnation enhanced. Such integrating of hemicelluloses extraction improved mush belongingss and improved production capacity, as already demonstrated in recovery furnace limited Kraft mush Millss [ 5 ] .

Treatment with dilute acid, hot H2O, alkaline/peroxide and other methods has generated technological involvement to pull out hemicellulosic constituents from SCB [ 4, 12-14 ] . However, it has to be noted that, certain physical belongingss of mush require hemicellulose in the fibre matrix [ 15, 16 ] . The coveted sum of hemicelluloses required in the mush merchandise depends wholly on the type of biomass, pulping procedure and the terminal usage of the mush [ 8 ] . Therefore, while developing the hemicellulose pre-extraction procedure, one should see non merely the output and the composing of extracted hemicellulose but besides the mush belongingss produced from hemicellulose pre-extracted solid residue.

The first aim of this survey was to look into the most favorable reaction conditions under which hemicelluloses could be extracted with dilute sulfuric acid or mild alkalic conditions from hemicellulose-rich sugar cane bagasse grown in South Africa, prior to alkaline pulping. In following the biorefinery attack, the 2nd aim was to mush the solid residue utilizing sodium carbonate or sodaAQ pulping methods to find the consequence of hemicelluloses pre-extraction on mush and paper quality. The best extraction method was described as the 1 in which maximal hemicelluloses was recovered while at the same time the quality of the mush was maintained at coveted degrees.

Material and experimental

Material

Sugarcane bagasse ( Saccharum officinarum ) was provided by a local industry TSB ( Mpumalanga, South Africa ) .The sugar cane bagasse ( SCB ) was depithed and conditioned at 23 & A ; deg ; C and 55 % comparative humidness before usage. Sodium hydrated oxide used for extraction of hemicelluloses ( xylan ) and pulping procedure was purchased from Merck. BUSPERSE 2262 Anthraquinone ( AQ ) was donated by Buckman Laboratories, Hammarsdale, South Africa.

Compositional analysis

The depithed SCB was prepared in a Retsch factory to 40 mesh size. Oven-dry mass ( DM ) was obtained utilizing an oven at 105±2 & A ; deg ; C until a changeless mass was achieved. The composing of the natural stuff was determined utilizing two methods: the standard methods of the Technical Association of the Pulp and Paper Industry ( TAPPI ) ( T264 om-88, T 211 om-85, T222 om-88 ; T 223 cm-84 ) [ 17 ] and the standard Laboratory Analytical Procedures for biomass analysis provided by the National Renewable Energy Laboratory ( NREL ) ; Colorado, USA [ 18 ] .

Xylan pre-extraction

Extraction of xylan from SCB by dilute sulphuric acid or mild NaOH ( alkaline ) methods was studied. Under acerb hydrolysis, the depithed SCB of 40 g and the acerb solution were assorted in the coveted parts and introduced into the micro reactors ( bombs ) . The filled bombs were placed in a digester of 15 dm3 capacity enclosed by heating jackets. The reaction temperatures selected were monitored with thermocouples. Alternatively, alkalic extractions were carried out in 500 milliliters schott bottles and kept at coveted temperature and clip in a shaking H2O bath. The ratio of solid to liquid was 1 g: 6mL. The pre-extraction conditions were varied consistently harmonizing to the cardinal composite design as presented in Table 1 [ 19 ] . The designs were created and evaluated in STATISTICA 7.1 ( Statsoft Inc. , Tulsa, USA ) . Three checks in the Centre point were carried out to gauge the random mistake required for the analysis of discrepancy ( ANOVA ) .

At the terminal of the coveted extraction clip, the reaction vass ( bombs and schott bottles ) were cooled in H2O. The indissoluble residue after acerb extraction was collected by filtration on a 100 mesh screen, whereas after alkalic extraction the fibers were squeezed by manus to retrieve the xylan. The solid residues were exhaustively washed with H2O and air dried. The oven dry mass cellulose, xylan and lignin contents of the solid residue were determined. The xylan-rich hydrolyzate was collected and a sample was filtered through 0.2 ?m membranes and analyzed for its content of monomeric sugars, soluble oligomers and byproducts. Aminex HPX-87H Ion Exclusion Column equipped with a Cation-H cartridge ( Biorad, Johannesburg, RSA ) was used. The column was operated at 65 & A ; deg ; C with a nomadic stage of 5mM sulfuric acid and a flow rate of 0.6 mL/min.

Each of the xylan rich filtrate obtained after alkalic extractions was concentrated to about 1/3 by rotary evaporator at 40 & A ; deg ; C. The filtrates were so dialyzed for 3 yearss against de-ionized H2O utilizing dialysis tubing cellulose membrane holding 12kDa molecular weight cut off ( MWCO ) . The samples were so conditioned in liquid N and were eventually freeze dried. The oven dry mass of the samples was determined.

Table 1

Sequence of experiments harmonizing to a cardinal composite design for

dilute H2SO4 and NaOH pre-extraction of xylan from sugar cane bagasse

Micro pulping of sugar cane bagasse residue

Solid residues run 9 and run 15 obtained after acerb hydrolysis were subjected to soda or sodaAQ micro pulping to pre-screen the pulping behavior of pre-extracted residues. Pulping of the non extracted SCB ( control ) was performed for comparing intent. Run 15 was preferred since maximal glucan content was observed in the solid residue after acerb hydrolysis, as illustrated in Fig 3A. Run 9 was selected since merely H2O ( Autohydrolysis ) was used during hydrolysis procedure. Prior to pulping the solid residues were exhaustively washed with H2O to take the acid and air dried. Alternatively, alkalic pre-extracted residue tally 6, and run 15 were besides subjected to sodaAQ pulping. In contrast to acid hydrolysis, no lavation was done to alkaline pre-extracted residues prior to pulping. The moisture residues were straight subjected to pulping and there was no add-on of NaOH during pulping.

All the pulping experiments were carried out ( Table 2 and Table 3 ) in micro bombs. The maximal cookery temperature was kept changeless at 170 & A ; deg ; C and the solid to liquor ratio was fixed at 1g: 7mL for all pulping experiments. Temperature and reaction clip were monitored during the procedure. Cooking clip was measured from the minute the system reached the maximal temperature. At the terminal of cookery, the fibres were separated from the black spirits and washed through a 10mesh screen, to divide culls from the fibres, the recognized mush was collected on a 100 mesh screen. The mush was so screened in a Packer slotted research lab screen. Entire mush output and culls were determined as a per centum of original dry mass of the natural stuff. Pulp kappa figure was determined by standard TAPPI methods T236.

Pulping for handsheets doing

Based to the best consequences obtained from the micro pulping experiments, solid residue tally 9 ( hot H2O, 120 & A ; deg ; C and 40 min ) and run 15 ( 1.5 M NaOH, 65 & A ; deg ; C and 40 min ) obtained after hot H2O hydrolysis and alkalic extraction severally were subjected to sodaAQ pulping for handsheets doing. Pulping was carried in a 15L batch type digester. SodaAQ mush were generated by exposing 1000g ( DM ) pre-extracted SCB residue to 14 % Na hydrated oxide and 0.1 % Anthraquinone ( AQ ) for 30 proceedingss at 170 & A ; deg ; C. At the terminal of the cookery procedure, the fibres were treated as explained above. Pulp features and strength belongingss were determined by TAPPI Standard methods [ 17 ] . Pulps were beaten in a Valley beater harmonizing to Tappi Standard T200 om-89 and the drainage rate in Schopper Riegler ( EsSR ) was measured harmonizing to Tappi T227 om-99. The manus sheets of papermaking belongingss were formed harmonizing to Tappi T205 om-88 utilizing British Standard manus sheet devising equipment. Burst index, interrupting length, and tear strength of the handsheets were measured by TAPPI Standard no T403 om-91, T404 om- 87, and T414 om-88, severally. The brightness was in ISO criterions utilizing a coefficient of reflection photometer ( Zeiss Elrepho 65843, Germany ) .

Table 3

Sequence of experiments for sodium carbonate pulping

of xylan extracted sugar cane bagasse

Table 3

Sequence of experiments for sodaAQ pulping of xylan extracted

sugar cane bagasse oven dry mass

Consequences

Raw stuff composing

The composing of sugar cane bagasse ( SCB ) is shown in Table 4. The glucan ( 46.0 % ) , lignin ( 18.2 % ) , xylan ( 23.6 ) , arabinans ( 2.4 ) , ash ( 2.6 % ) , ethanol/cyclohexane ( 1.7 % ) and H2O soluble extractives ( 2.4 % ) were observed. Since xylan was the major pentosan, it was the considered sugar through out this survey. This information was used to bring forth the full extraction recovery output described below.

Table 4

Chemical composing of sugar cane bagasse

Liquid fraction after xylan pre-extraction

The composing of the liquid fraction obtained after acid and alkalic pre-extraction of xylan from SCB is illustrated in Fig. 1A and 1B severally. The concentrations were expressed in g/100g and extraction per centum to esteem the polymer content in dry natural stuff. The outputs obtained after acerb hydrolysis varied within the scope 0.3-11.1 g/100g ( ~1.2- 42.9 % ) as shown in Fig. 1A. The concentration of the sugars increased to 0.3 -15.98 g/100g ( ~1.2-62 % ) when the prehydrolyzate obtained after acerb hydrolysis was treated with 4 % sulphuric acid at 121 EsC. In all the experiments the concentration of glucan and acerb soluble lignin in the liquid fraction was less than 1 g/100g.On the other manus, alkalic conditions resulted to the xylan concentration varied within the scope of 9.8 to 22.8 g/100g ( ~ 43.3-88.6 % ) as shown in Fig 1B.

Fig. 1. Entire glucan and xylan output expressed as g/100g of the original stuff in the liquid fraction under different sulphuric acid ( A ) and NaOH ( B ) extraction conditions.

ANOVA analysis supplying information on which procedure variable had important consequence during pre-extraction are presented by multiple arrested development equations ( 1 and 2 ) . In the equations, XA, XT, Xt and XS are the coded values of the operational variables sulphuric acerb concentration ( % v/v ) , temperature ( EsC ) , abode clip ( proceedingss ) and NaOH concentration ( M ) severally. All the interactions were important at 95 % assurance degree and the deficiency of tantrum of the theoretical accounts was undistinguished. The square of the correlativity coefficient ( R2 ) for per centum xylan obtained under acidic conditions ( Y1 ) and per centum xylan obtained under alkalic conditions ( Y2 ) was 0.98 and 0.82 severally, explicating 98 % and 82 % of the variableness in the responses.

Y1 ( % ) = 4.7+ 3.8XA + 3.5XT + 3.3Xt + 2.1XAXt + 1.6XTXA ( 1 )

Y2 ( % ) = 19.1 + 5.2XS + 3.9XT – 3.7 XTT ( 2 )

All the procedure variables showed strong influence on xylan hydrolysis under acidic conditions ; as indicated in the multiple arrested development equation 1. The xylan extractions under alkalic conditions, was influenced by both NaOH concentration and temperature as shown in equation 2.

Response surfaces described by the above theoretical account equations were fitted to the experimental information points refering the xylan recovery as shown in Fig. 2. The response surfaces showed that the addition in variable values would increase the output of cured xylan. However, Fig 2B indicated a decrease in xylan output when the temperature exceeded 90 & A ; deg ; C under alkalic conditions.

Fig. 2. ( A ) Estimated response surface for xylan output obtained after sulphuric acerb hydrolysis demoing the influence of temperature and acerb concentration for a abode clip of 40 proceedingss. ( B ) Estimated response surface for xylan output obtained after NaOH extraction demoing the influence of temperature and NaOH concentration for a abode clip of 180 proceedingss.

Solid fraction after pre-extraction

The recovery scope of sugars on dry weight footing retained in the solid residue after acid and alkalic pre-extraction of SCB is shown in Fig. 3. Glucan and acerb indissoluble lignin retained in the solid residue after acerb pre-extraction ranged between 41 to 54 g/100g ( 90 % -118 % ) and 16-19 g/100g ( 76-104 % ) severally. For alkalic conditions the scope for glucan and acerb indissoluble lignin was 51 to 60 g/100g ( 110-130 % ) and 6 to 17 g/100g ( 33 % -93 % ) severally. The xylan retained in the solid residue ranged between 14 to 25 g/100g ( 56-97 % ) after acerb hydrolysis and the scope was 2 to 16 g/100g ( 8-62 % ) after alkalic extractions.

Fig. 3. Entire glucan and xylan output expressed as g/100g of the original stuff in the solid fraction under different sulphuric acid ( A ) and NaOH ( B ) extraction conditions.

3.5. Pulping of xylan extracted sugar cane bagasse

Solid residues run 9 ( H2O, 120 & A ; deg ; C, 40 min ) and run 15 ( 0.3 % v/v, 120 & A ; deg ; C,40 min ) obtained after acerb hydrolysis were subjected to soda or sodaAQ micro pulping. Conditionss used for pulping are described under experimental process. The mush output, kappa figure and reject degree of the mush obtained after soda pulping of both extracted and not extracted SCB ( control ) are shown in Table 5A. The mush outputs recorded from the control were 32.4-34.5 % , compared to 35.1-39.7 % and 35.4-37.4 % of Run 9 and Run 15 severally. The kappa figure of the control pulps ranged between 33.5-34.8 points and the cull degrees range was 6.0-9.9 % . Run 9 resulted to pulps with kappa figure ranged between 32.0-33.2 points and the cull degrees were 4.4-8.0 % . Kappa figure of mushs produced from Run 15 ranged between 36.9-38.4 points and the cull degrees were 9.4-A2.7 % .

Table 5B list the comparative mush features obtained after sodaAQ pulping of both extracted and control SCB. The mush outputs recorded from the control were of 31.9-46.2 % , accompanied with reject degree of 4.9-9.9 % and a kappa figure of 31.3-31.9 points. Run 9 and Run 15 resulted to mush outputs of 36.5-53.6 % and 38.3-39.9 % with kappa figure of 28.6-29.4 and 36.9-38.4 points severally. The reject degrees of the mushs were 0.5-11.5 % and 9.0-13.1 % for Run 9 and Run 15 severally.

The consequences obtained from alkaline extracted residue tally 6 ( 2M NaOH, 40 & A ; deg ; C ) and run 15 ( 1.5 M NaOH, 65 & A ; deg ; C ) are shown in Table 5C. The mean mush output, kappa figure and reject degree obtained from Run 6 was 37.7±2.8 % , 16.8±1.0 points and 2.8±0.4 % severally. Run 15 resulted to average mush output of 40.1±2.0 % accompanied with reject degree of 2.1±0.3 % and a kappa figure of 15.8±0.3 points.

Table 5A

Soda pulping consequences for 11 % ( Hot H2O, 120 EsC, and 40 min ) and 23 % ( 0.3 % v/v H2SO4, 120 EsC, and 40 min ) xylan extracted sugar cane bagasse

Table 5B

SodaAQ pulping consequences for 11 % ( Hot H2O, 120 EsC, and 40 min ) and 23 % ( 0.3 % v/v H2SO4, 120 EsC, 40 min ) xylan extracted sugar cane bagasse

Table 5C

SodaAQ pulping consequences for 73 % ( 1.5M NaOH, 65 EsC, 240 min ) and 79 % ( 2M NaOH, 40 EsC, 240 min ) xylan extracted sugar cane bagasse

Based on the best pulping pre-screen consequences, autohydrolyzed run 9 and alkaline extracted run 15 were pulped with 14 % NaOH, and 0.1 % AQ for 30 proceedingss in a pilot graduated table for handsheets doing.The non extracted SCB was pulped for comparing. The belongingss of the mush are presented in Fig. 4. Screened mush outputs obtained from the control, alkalic pre-extracted and autohydrolyzed SCB were 40.12 % , 44.97 % and 41.28 % severally. The mush viscousnesss in centipoise were 7.2, 7.1 and 5.5 and the kappa Numberss of the mushs were 22.8, 20.9, and 15.5 severally. Pulping of non extracted SCB resulted to the reject degree of 15.7 % compared to 3.3 % of NaOH pre-extracted residue and 14.7 % of autohydrolyzed residue.

Fig. 4. Pulp belongingss of non extracted and extracted sugar cane bagasse on pilot graduated table sodaAQ pulping procedure. The NaOH concentration =14 % , AQ = 0.1 % , T = 170 & A ; deg ; C, t = 30 min

Handsheets physical belongingss

The explosion index, tear index, interrupting length and ISO brightness belongingss of handsheets produced from sodaAQ mushs are shown in Fig 5. It has been observed that strength belongingss increased with increasing grade of crushing expressed in & A ; deg ; SR. The sequence of presentation of the consequences will be for the control, alkaline and autohydrolyzed mush severally. The explosion index scope was ( 2.4-4.7 kPa.m2/g ) , ( 1.4-4.3 kPa.m2/g ) , and 1.7-5.0 kPa.m2/g ( Fig. 5A ) . The tear index scope was ( 3.3-4.4 mN.m2/g ) , ( 8.8-9.8 mN.m2/g ) and 4.7-4.8 mN.m2/g ( Fig. 5B ) . The interrupting length belongings of the handsheets ranged between ( 2.4-5.0 kilometer ) , ( 1.3-4.5 kilometer ) and 1.8-5.0 kilometer ( Fig. 5C ) . The optical brightness of handsheets ranged between ( 39.3-43.5 % ISO ) , ( 51.7-55.8 % ISO ) , and 41.5-44.2 % ISO ( Fig.5D ) .

Fig. 5. Handsheets belongingss as the map of drainage in EsSR of sugar cane bagasse after sodaAQ pulping.

Discussion

The composing of the liquid fraction recovered after hydrolysis of SCB with dilute sulphuric acid is presented in Fig 1A. Analysis of the consequences revealed that xylan hydrolysis was improved when both acerb concentration and temperature were increased from 0.1 to 0.5 % and from 100 to 140 & A ; deg ; C severally at 60 proceedingss. The sugars were largely oligosaccharides with the maximal output of 42.87 % and this value increased to 62.07 % when the prehydrolyzate was later treated with 4 % sulphuric acid at 121 & A ; deg ; C. Pessoa et al. , extracted about 70 % of hemicelluloses in SCB by sulphuric acid on a laboratory graduated table at 140 & A ; deg ; C [ 20 ] . Attempts to increase temperature above 140 & A ; deg ; C to retrieve more xylan as suggested by the statistical analysis in Fig 2A resulted to the debasement of xylan. This was shown by the presence of 0.3 g/L furfural at temperatures of 154 & A ; deg ; C. Neureiter et al. , reported that temperature showed the highest impact on the formation of debasement merchandises during dilute acerb hydrolysis of SCB [ 4 ] . Uniting the analysis of the liquid fraction with the consequences obtained in the analysis of the solid residue in Fig 3B, it can be observed that high recovered xylan fraction corresponded to the high glucan content ( 111.9 % ) retained in the solid residue. This consequence is of import for the use of the solid residue for mush and paper devising. The lignin content in the solid residue at this point was 86.3 % . Similar consequences of high glucan recovery ( 89 to 126 % ) during liquid hot H2O pre-treatment of SCB was reported [ 21 ] . Cellulose and lignin are immune to assail by dilute acids at low temperatures, although little fraction of lignin ( about 10 % ) can be dissolved in the procedure [ 20, 22 ] .

In comparing, alkalic conditions have been shown to better its potency for xylan extraction ( Fig 1B ) . The maximal xylan recovered up to 88.6 % under 2.34 M NaOH and 65 & A ; deg ; C was observed. The statistical correlativity presented in Fig 2B against temperature and NaOH concentration showed that increased in temperature beyond 65 & A ; deg ; C would diminish the xylan recovery output. Optimum xylan recovery was accompanied by high disintegration of lignin, where merely 49 % lignin was obtained in the solid residue. For mush factory biorefinery to be effectual, the lignin content of the extracted hemicellulose should be comparatively low, and the DP of cellulose and lignin responsiveness in the extracted french friess remains high during subsequent pulping [ 6 ] . Treatment of non wood stuff under alkalic conditions at room temperature has been reported to solubilised up to 50 % of lignin nowadays in the stuff [ 23, 24 ] . Brienzo et al. , extracted 94.5 % hemicellulose from SCB associated with more than 88 % lignin utilizing alkalic peroxide [ 14 ] .

The consequence of xylan pre-extraction on mush output, kappa figure and degree of culls after sodium carbonate and sodaAQ pulping was evaluated. As can be seen in Table 5A the full tested residues resulted to mush outputs less than 40 % with similar kappa figure under sodium carbonate pulping. Soda pulping of alfafa stems resulted to low screened mush output ( 16-21 % ) and high per centum culls ( 18-35 % ) [ 25 ] . Addition of anthraquinone ( AQ ) , during the sodium carbonate pulping procedure improved the outputs, kappa figure and reject degrees of the mush as shown in Table 5B. AQ has maximal consequence on debasement of lignin and stabilisation of celluloses in pulping procedure [ 26 ] . Table 5B showed that autohydrolysis of SCB prior to sodaAQ pulping improved mush belongingss when compared to both the non extracted and acid extracted mush. Comparing the best pulping consequences ( Run 2 in Table 5B ) , autohydrolyzed SCB produced 14 % higher mush outputs than those of not extracted mush and 26 % higher than those of acid extracted mush. The delignification efficiency was besides improved due to autohydrolysis. The kappa figure for autohydrolyzed mush was 5.6 points lower than for the non extracted mush and 9.4 lower than for acid extracted mush. At this point the reject degree for autohydrolyzed mush was merely 0.5 % . It is reported that lignin in SCB is covalently bonded to arabinoxylans through ferulic acid Bridgess [ 23 ] . Solubilization of hemicelluloses under the hot H2O extraction at mild temperatures could hold resulted to the cleavage of the ester linkages between arabinose and the ferulic acid. This resulted to the unfastened construction of the cell wall which promoted the facilitation of cooking chemicals during pulping, therefore high mush outputs and low culls degrees [ 7 ] . Previously a hot H2O pre-extracted SCB with kappa figure 12.4 and screened mush output 52.95 versus kappa 16.6 and screened mush output 53.27 from non extracted SCB was obtained [ 12 ] . The information presented in Table 5B showed that, the combined procedure of hemicellulose pre-extraction with sulphuric acid and sodaAQ pulping is non the best option following the hapless pulping response on separation of merely little fraction of hemicelluloses in prehydrolysis. In comparing, sodaAQ pulping of 73 % xylan extracted SCB resulted to mush output of 40.1 % accompanied with the kappa figure of 15.8 points. Lopez et al. , reported mush output scope of 40.5-45.9 % accompanied with kappa figure scope 12.9-17.7 during sodaAQ pulping of 31-72 % hemicellulose extracted barley straw [ 27 ] .

Based on the best consequences obtained from laboratory graduated table pulping ( Table 5B and 5C ) , sodaAQ of autohydrolyzed and alkalic extracted SCB was performed in a batch type pilot graduated table digester to measure the consequence of xylan extraction on strength belongingss of the mush. The consequences were compared with those of the non extracted SCB mush treated under similar pulping conditions. SodaAQ pulping in a pilot digester reduced the mush output of non extracted and autohydrolyzed SCB by 13.2 % and 23 % severally. This difference could be related with the high pith content in the natural SCB, since depithing was done by manus.

Consequences in Fig 4 showed that mush prepared from alkaline extracted SCB on pilot graduated table improved the output by 10.8 % at kappa figure 15.5 than the control at kappa figure 22. 8 and improved by 8.2 % than autohydrolyzed mush at kappa figure 20.9. The viscousness of alkaline extracted mush was 1.4 % less than the control pulps, demoing minimum cellulose debasement. This consequence is really of import since the alkalic pre-extraction procedure was able to keep the quality of the mush at coveted degrees while at the same time accomplishing acceptable degrees of hemicellulose pre-extraction. The increased cellulose keeping with AQ add-on is caused by stabilisation of cellulose cut downing terminals by oxidization with AQ [ 28 ] . The viscousness of autohydrolyzed mush was lower by 23.6 % than the control, likely due to the cellulose loss through skining reaction during cookery.

All the mush were beaten to better handsheets strength belongingss and the optimal strengths were reached at the crushing grade of 20 EsSR as shown in Fig 5. Alkaline extraction demo a 56.4 % betterment in tear index and a 24 % betterment in optical brightness compared with the control. However, both interrupting length and burst index were reduced by 10.6 % and 9.3 % severally. These belongingss depend on fibre prostration and interfiber adhering [ 29 ] . The decrease in the strength belongingss can be traced back to the high per centum of xylan ( 73 % ) extracted anterior to pulping Hemicelluloses enhanced fiber bonding during whipping of mush [ 10, 16 ] . Decrease in tear index by 2 % and explosion index by 8 % due to sodaAQ pulping of 57 % xylan extracted barley straw has been reported [ 27 ] . In comparing, autohydrolyzed mush showed an betterment in optical brightness, tear and burst index by 5.3 % , 18.72 % and 5.0 % severally than the control. The interrupting length of the mush was 0.4 % less compared to command mush. These consequences are somewhat different to those obtained in the literature during sodaAQ of autohydrolyzed SCB although the pulping conditions in the compared survey were somewhat higher [ 12 ] . The consequences obtained in the referenced survey showed that autohydrolyzed mush improved the optical brightness and tear index by 6 % and 10.6 % compared to the sodium carbonate mush obtained from non extracted SCB. The breakage length and burst index of autohydrolyzed mush were reduced by 21.8 % and 26.3 % severally compared to the control [ 12 ] . This determination could be related to the usage of higher temperatures in the referenced survey ( 160 & A ; deg ; C versus 120 & A ; deg ; C ) combined with higher NaOH concentration ( 15.5 % versus 14 % ) during pulping. The procedure alteration prior to pulping and the pulping cookery conditions may impact the physico-chemical belongingss of mush [ 8, 30 ] .

Of the two pre-extraction methods, autohydrolysis had the high breakage length and explosion index, while alkalic extraction has the highest mush brightness and superior tear index at maximal crushing grade of 20 & A ; deg ; C. In literature, it has been mentioned that, the decrease in explosion and tensile index is non the modification factor for the choice of high paper classs, as long the mush still hold more equal tensile strength [ 29 ] .

Decision

Dilute sulphuric acerb hydrolysis of sugar cane bagasse under low temperature and mild acerb concentration is the efficient method to pull out xylan from sugar cane bagasse. About 62 % of wood sugar can be recovered with 0.3 g/L furfural nowadays in the hydrolysate. However, the remotion of little fraction of xylan ( up to 23 % dry mass ) through dilute sulphuric acerb hydrolysis measure affected the subsequent sodaAQ pulping. Pulp outputs less than 40 % with kappa figure around 35 points were obtained. When 11 % of the orgininal SCB xylose was extracted through autohydrolysis at pilot graduated table, and the residue subjected to sodaAQ pulping, the mush outputs were somewhat improved and the kappa figure of the mush were lower than those of the control. The physical strength belongingss of the mush were improved, except for little decrease in interrupting length by 0.4 % . The combination of 73 % pre-extracted xylan under mild alkalic conditions with subsequent sodaAQ pulping improved the delignification rate. Pulp outputs were high and the kappa figure of the mush was less than 20 points. The viscousness of the mushs were comparable to those of control. These conditions provided mush with higher brightness and superior tear index. On contrary the breakage length and explosion index was reduced. Harmonizing to these consequences both alkalic and hot H2O pre-extraction of sugar cane bagasse had a great potency for the integrating procedure of xylan extraction prior to pulping and subsequent sodaAQ pulping depending on the desired concluding merchandise of the of paper.

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