Cellulose nanocrystals (CNCs) as a renewable and biodegradable nanomaterial have wide application value. In this work, CNCs were extracted from bleached chemical pulp using two stages of isolation (i.e. formic acid (FA) hydrolysis and 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO) mediated oxidation) under mild conditions. In the first stage, FA was used to remove hemicellulose, swell cellulose fibers, and release CNCs. The FA could be readily recovered and reused. In the second stage, the CNCs isolated by FA were further modified by TEMPO-mediated oxidation to increase the surface charge of CNCs. It was found that the modified CNCs with more ordered crystal structure and higher surface charge had better redispersibility and higher viscosity in aqueous phase. Therefore, the modified CNCs could be more effective when used as rheology modifier in the fields of water based coating, paint, food etc.

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Sulfated zirconia hydroxide shaping by extrusion is studied based on elucidating the impact of zeta-potential and rheological characteristics on physical and chemical properties of technical catalysts. Zeta potential measurements of sulfated zirconium hydroxide prior and after poly­(vinyl alcohol) (PVA) additions were made. Rheological curves of sulfated zirconium hydroxide suspensions with different amounts of PVA were recorded at different zeta-potential values. The addition of PVA nonlinearly decreased shear yield stress. Experimental data were quantified with the Krieger–Dougherty equation. The influence of a boehmite-type binder on the zeta-potential confirmed that the surface properties of the particles to a large extent are determined by the presence of binder. The pore structure of shaped catalysts was unaffected by rheological parameters when zeta-potential is close enough to zero. At the same time deviations of the zeta potential from the zero-value afforded more uniform pore size distribution.

The traditional method to isolate cellulose nanocrystals (CNCs) is to subject cellulosic materials to strong acid hydrolysis by mineral acids, which usually causes problems such as corrosion of equipment, the need for large amounts of water, the difficulty of acid recovery, and over‐degradation of cellulose. Thus, a green and sustainable approach for the preparation of CNCs was developed where mild acid hydrolysis with diluted oxalic acid was used. The reaction kinetics of different preparation parameters, such as reaction temperature, oxalic acid dose, addition of HCl, and reaction time were thoroughly investigated. A high yield of up to 85 % was achieved by mild oxalic acid hydrolysis in comparison to the yield of 35 % using the most common approach with sulfuric acid hydrolysis. The CNCs from the above approach have a high thermal stability, that is, a maximum thermal degradation temperature of 350 °C in comparison to 200 °C when sulfuric acid hydrolysis was used. Importantly, oxalic acid solutions were readily recovered, and exhibited consistently high performance in several continuous runs of reaction. The hydrolysates contained mostly monomeric sugars, which could be further utilized for chemical or biofuel production.

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