Green and Low-cost Production of Thermally Stable and Carboxylated Cellulose Nanocrystals and Nanofibrils Using Highly Recyclable Dicarboxylic Acids

The overall goal of this procedure is to demonstrate the integrated production of carboxylated, thermally stable cellulose nanocrystals with cellulose nanofibrils from cellulosic feedstock using solid dicarboxylic acids with easy acid recovery. This method is to help us answer the question how to produce with nanomaterials. The main advantages of this technique is that the results of materials are similarly highly most stable, carboxylated, and the acids we use can be easily recycled, therefore to achieve even stability.

To begin the procedure, place 40mL of deionized water and a magnetic stir bar into a three-neck, round-bottomed flask. Heat the water to 85 degrees Celsius with a liquid glycerol bath. Then, add 60g anhydrous maleic acid to the flask and stir until completely dissolved to obtain a 60 weight percent moleic acid solution.

Heat the solution to 100 degrees Celsius while stirring. Then, add 10g of oven-dried, bleached, eucalyptus kraft pulp, and stir the mixture for one hour to hydrolyze the pulp. During hydrolysis, prepare a vacuum filtration flask and buchner funnel with filter paper.

Then, add 160mL of 80 degrees Celsius DI water to the reaction flask to terminate hydrolysis. After an hour has elapsed, take a 2mL aliquot of the acid hydrolyzate for concentration analysis. Immediately collect the solids by vacuum filtration.

Wash the solids with DI water and retain the filtrate for acid recovery. Transfer the washed solids to a centrifuge bottle and add DI water to obtain an approximately 1%by weight mixture. Centrifuge the pulp mixture at 11, 960G for 10 minutes, and then discard the supernatant.

Continue washing the solids by centifugation until the supernatant appears turbid. Resuspend the solids in the turbid supernatant. Dialyze the mixture against DI water until the conductivity of the pulp mixture is close to that of DI water.

Then, centrifuge the dialyzed sample at 3, 500 G for 10 minutes. Decant the supernatant to separate the aqueous dispersion of CNCs from the fibrous cellulosic solid residue. Then, prepare a 0.5%by weight fiber suspension in DI water using the fibrous cellulosic solid residue.

Pass the suspension through a 200 micrometer homogenizer chamber at 100 millipascals three times, And then through an 87 micrometer chamber at 100 millipascals twice to obtain CNFs by mechanical fibrillation. To determine the nanomaterial length and diameter distributions, first sonicate a 0.01 weight percent suspension of CNCs or CNFs for two minutes. Apply a drop of the suspension to a mica AFM substrate and allow the sample to air dry.

Acquire AFM images in vibrating tapping mode. Once the images include at least 100 individual CNCs or CNFs, process the images with analysis software to obtain the size distributions. Next, combine a suspension containing 50mg of cellulose nanomaterials with 120mL of one millimolar sodium chloride.

Perform conductometic titration with 0.2mL portions of 10 millimolars sodium hydroxide at 30 second intervals and determine the inflection point. Calculate the caarboxylic acid group content of the sample. Purge the instrument furnace with high purity nitrogen at 20mL per minute.

Next, dry CNC and CNF samples at 50 degrees Celsius for four hours to prepare for thermogravimetric analysis. Load 5mg of a dry cellulose nanomaterial sample into the instrument. Heat the furnace from room temperature to 600 degrees Celsius at a rate of 10 degrees Celsius per minute, and evaluate sample decomposition with the instrument's software.

Check the thermal stability of the CNC and CNF samples at 105 degrees Celsius for four and 24 hours. Use wide-angle x-ray defraction and FTIR spectrophotometry to further characterize the cellulose nanomaterial samples. Using this procedure, CNCs and CNFs were produced from bleached eucalyptus kraft pulp, and unbleached mixed hardwood kraft pulp.

Hydrolysis with dicarboxylic acids such as moleic acid reduced fiber length without significantly affecting fiber diameter. The CNC yield was comparatively low when moleic acid was used. CNFs were obtained by mechanical fibrillation of the fibrous cellulosic solid residue from hydrolysis, and were correspondingly longer and thinner than the CNCs.

While attempting this procedure, it is important to remember to use dialysis to separate the CNCs. After its development, this technique will pave the way for the scientists in the field of material science, medical science and electronic industry to develop body parts and using this material. After watching this video, you should have a good understanding how to produce similarly stable carboxylated cellulose nanomaterials using dicarboxylic acids.

Don't forget, and always remember, working with a concentrated acid can be extremely hazardous, so precautions have to be taken while performing this procedure.