How are you deliginifing the wood at the moment? If you are heating it, you will most likely be getting break down products like 5-Hydroxymethylfurfural (5-HMF) and 2-Furaldehyde (2-FA) from the Cellulose and Hemicellulose which have a brown colour. I would suggest that you look at some methods used in the paper and pulping industry such as the Kraft process. Hope that helps.

You must discolored brown pulp with oxygen and peroxide bleaching and deligification agents such as and hydrogen peroxide.

Bleach it with NaClO2 + HAc in my opinion is more effective than the bleaching with H2O2, Is teh method proposed by TAPPi to calculate the holocelulose content on fibers/pulps. Best regards

U may use household bleach to make ur biomass in white color. Dewaxed-- u may try to Soxhlet process as suggested by Jon (Tappi test method: Solvent extraction in wood pulp).

I have tried sochlet process before delignification, but I still getting cellulose with brown color

Hi Noer, The soxhelt process is not to remove ligning is to remove waxes/oils, so it´s not likely to have a color change after this process. Now what you have to make is the TAPPI method to determine holocelulose. Briefly, yo have to add 80 mL of water /2,5 grams of solid. keep the temperature at 70 C and every hour during 6 hours add 0.5 mL of acetic acid and 2.6 mL of NaClO2 at 25%; - you should see after 2-3 hours how your sample is going whiter- . CAUTION!!!!!! The NaClO2 degradates to Cl2 which is a toxic gaz!!! In my opinioon once you see that the fiber is white you can stop, doesn´t make sense to keep it overnight as suggested by TAPPI method. In case of any doubt do not hesitate con contacting me.

Best regards

Multistep alkali-acid pretreatment processes may require for extracting cellulose and hemicellulose.

You may get details on bellow links (materials and methods)

www.aensiweb.com/anas/2009/5-11.pdf

http://ojs.cnr.ncsu.edu/index.php/BioRes/article/viewFile/3637/2016

Hexane?

Bleaching process to convert the brown pulp to a white ... hydrogen peroxide, and ozone, ClO2, Cl2 to remove residual lignin from the pulp

Peroxide bleaching:

into bags, weigh 10 g a.s. pulp. Weighed quantity of NaOH (charge 1.5% on pulp absolutely dry (a.s.) and MgSO4 (charge 0.2%/) were separately dissolved in water to maintain the consistency of 10%.

Measure the pH! Unless pH 11, treatment with H2SO4 (about 1% solution), the successive addition. If the pH of about 11, was added hydrogen peroxide (charge to 3%), an aqueous solution and mixed thoroughly, the pH measured.

Then transfer to a plastic bag and the suspension is thoroughly mixed.

Bag is closed, so that the space for the escaping gas, placed in a heated oven (80 ° C) for 90 minutes. The sample was purged with water.

PAA -peracetic acid bleaching

pH 4-6, 10 % consistency, peracetic acid (charge to 1%), temperature 80°C, reaction time 90 min.

ozone bleaching - procedure _effect of brightness_ publication_Effect of pH and temperature on the optical properties in ozonization oxygen delignified hardwood kraft pulp - my researchgate

Dear noer

are you want produce a dissolving pulp garde or paper grade exactly?

Their application are different together.

Dear Noer

Please refer the following attachments for your kind references,

To remove the natural colors from biomass, you have to bleach them with several steps of using chemicals under heat treatment, Adequate amount of biomass/ chemical solutions is very important in order to efficient bleach of your biomass.

Good luck

Another one

Dear Noer,

You can increase the dosage of sodium chlorite and acetic acid during bleaching at 70 degree for 2 hours. After you obtain a white holocellulose, you can further hydrolyse with 17.5 % NaOH at 25 degree for 30 min then diluted to 8.75 % of NaOH for another 30 min (normally basic hydrolysis give a very white cellulose fiber). Hope this would help.

Hazwan

Use of sodium chlorite + acetic acid (3:1, wt/wt) at 70oC may help you. This process is used in paper industries to complete discoloration (delignification) of wood. After removal of lignin completely further you have to remove hemicellulose to obtain pure white cellulose.

I agree with Prasenjit Bhaumik. The most effective method is Chloride method.

sodium chlorite + acetic acid 70-80 C is widely used. Pay attention to biomass/liquid ratio..most use 5% (w/v).

I have begun dewaing with hexane, the alkali step, neutralize and use sodium chlorite next....I obtained several holocelulosis from several types of biomass. Check my project reports for pictures.take care and good luck.