Orlando Rojas


Research Interests

Nanopolysaccharides (based on cellulose, chitin, starches and others)
Bacterial nanocelluloses
Cellulose derivatives
Lignins, colloidal lignins, nanolignins and their uses
Renewable biopolymers (hemicelluloses, proteins, chitin and chitosan, alginates and others)
Multiphase systems (emulsions, foams, dispersed systems), gels, aerogels
Films, filaments and hybrid materials
Bioactive systems
Fiber processing
Pulp and paper

Relevant Thesis-Based Degree Programs

Affiliations to Research Centres, Institutes & Clusters


Graduate Student Supervision

Master's Student Supervision

Theses completed in 2010 or later are listed below. Please note that there is a 6-12 month delay to add the latest theses.

Integrated bioprocessing concept: hemp hurd valorization by co-production of lignified nanomaterials, lactic acid and binderless fiberboards (2024)

This work seeks to conceptualize a novel pilot process for valorizing hemp hurd residues. Presented here are three proof-of-concept investigations and a simple gross profit analysis to motivate the development of a zero-waste, integrated biomaterials production process for co-production of lignified cellulose nanomaterials, lactic acid, and binderless fiberboards. The nanomaterials are produced by oxalic acid hydrolysis of unwashed ground hemp hurd to produce thermally resistant nanomaterials in two output streams separated by centrifugation. The colloidal supernatant from nanomaterial production is concentrated and dried by spray-freeze drying before inclusion in melt-processed PA-6 nanocomposites, which are tested for their mechanical properties. Binderless boards are produced by fluidized grinding of hemp hurd in a mass colloider followed by filtration and hot pressing in enclosed press molds. These boards are then tested for their material properties and compared to ANSI Basic Hardboard standards. The hydrolysate left over after nanomaterial production is combined with filtrate from the binderless board grinding process and a fermentation is conducted with Lactiplantibacillus plantarum to study productivity of lactic acid caused by introduction of hydrolysate to media. The results from these three sets of experiments are used to inform a mass balance and gross profit analysis on the integrated process concept proposed. A valorization factor of >7.4 is reported, based on a 1000 kg/day pilot-scale process. This finds daily gross profit between $3490-$8900, when only the input costs and output wholesale values of products are considered. The M1250 binderless fiberboard produced exceeded ANSI standards for type 1 hardboard. Nanocomposites of PA-6 with 1% loading showed a 21 ±2% increase in ultimate tensile strength, and a 71 ±1% increase in elastic modulus compared to the neat PA-6.

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Surface interactions between chitin nanocrystals and an anionic surfactant : from fundamentals to applications (2023)

We elucidate the interactions between positively charged chitin nanocrystals (ChNC) and an anionic surfactant, sodium dodecyl sulfate (SDS), and report on their role in the stabilization of Pickering emulsions. ChNC/SDS interactions were systematically investigated by using electrophoretic mobility, surface tensiometry, and quartz crystal microgravimetry. The results indicate that SDS molecules undergo different regimes when adsorbing on the chitin nanoparticles. At low SDS concentration, a monolayer is assembled on the surface of ChNC, attributed to the hydrophobic effect and electrostatic interactions. We suggest that with the increased SDS concentration, adsorption in the form of bilayer or patchy bilayers occurs followed by the formation of adsorbed hemi-micelles and micelles. We further suggest that hydrophobic interactions play a critical role in defining the transitions presented by the adsorbed species and their conformations. At the highest SDS concentrations tested, we observe charge neutralization and flocculation, in the form of SDS/ChNC aggregates. Remarkably, at given concentrations, the adsorbed SDS introduces hydrophobicity to the chitin nanoparticles, which opens the opportunity to achieve tailorable conditions for Pickering stabilization. Hence, a facile method is proposed by in-situ surface modification, using the physical adsorption of SDS on ChNC, which extends the potential of renewable nanoparticles in the area of complex fluids, for instance, in the formulation of household and healthcare products.

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