Volume 34, Issue 2

Kraft pulps from acacia hybrid, Acacia mangium of 8 years old and Acacia auriculiformis of 6, 8 and 10 years old were pre-treated with oxygen, peroxyformic acid and acid treatment prior to bleaching. The kappa number reduction was 52–63 % by oxygen delignification, 31–35 % by peroxyformic acid (PFA) pre-treatment and 11–13 % by acid pre-treatment. Oxygen delignified pulp required less chlorine dioxide charge to reach target brightness. At the consumption of 30 kg ClO 2 /ton of pulp, the pulp brightness reached to 65–71 % for the untreated pulp, 81–85 % for the oxygen delignified pulp, 81–82 % for the PFA treatment and 79–80 % for acid pre-treated pulp. COD load in bleached effluent was much lower in oxygen delignified pulp. Cold alkali extraction of unbleached and oxygen delignified pulps was also carried out with varying alkali charge to remove hexenuronic acid (HexA) from the pulp. Xylan removal from the pulp was insignificant and resulted in no removal of HexA. Acid pretreatment removed 55.7 % to 17.8 % HexA from acacia hybrid, 57.5 % to 16.3 % from A. auriculiformis of 10 years and 58.6 % to 20.1 % from A. auriculiformis of 6 years old, resulting in improved final pulp brightness.

Chemical additives are used singly or in combination to impart functionality to hygiene paper (suggested). In particular, in the hygiene paper making process, dry strength agent, wet strength agent, softener, and other are widely used. The effects of chemical additives on the softness components were evaluated. In the case of surface softness, there was no change in MMD according to the addition of dry and wet strength agents. The MMD (mean deviation from the average friction of coefficient) was decreased by adding a softener, which is the purpose of its addition to the hygiene paper making process. The softness and wet strength were improved when the wet strength agent was added before the softener. In addition, lotion treatment was applied to the surface of tissue paper. The surface softness component of non-silicone-based lotion was similar or improved, which may overcome the problems of silicon-based lotion.

Fractionation of cellulose fibers is performed within a circular mini-channel (diameter 7 mm) to realize a novel fractionation principle. We show that fractionation within a single-floc regime relies on the formation of a rigid network in cases where the crowding number is chosen to be greater than 60. Fractionation is performed for channel Reynolds numbers Re>Re\mathrm{>} 10,000, and unlike the situation in larger channels, fractionation is found to be relatively independent of ReRe. Experiments show a high dependency of the radial aperture velocity and aperture width on fractionation performance associated with fibers that are longer than 200 µm. By contrast, fibers shorter than 200 µm are only influenced by the volumetric flow rate through the aperture. Our results suggest that fibers smaller than 200 µm are mobile in the near wall region. Fibers longer than 200 µm are, dependent on their length, drawn out of the network by hydrodynamic forces acting on them as a result of the radial fluid velocity caused by the accept flow through the aperture. Our results support a novel fractionation hypothesis that is in contrast to previous findings, which were based on dilute flows and were demonstrated in channels having a larger size.

Nano-lignocellulose (NLC) and lignin-free nanocellulose (nano-holocellulose, NHC) were used in paper coating to investigate their effect on coating layer quality and offset printing. The NLC was produced by microfluidisation of unbleached secondary fibres while the reference NHC was obtained from the same fibre source after lignin removal (OHE P H bleaching), following the same mechanical process. TEMPO-mediated oxidation of the fibres prior to microfluidisation was applied to increase the electrostatic charge and hydrophilicity of the nanofibrils. The coatings, displaying given surface morphology and energy, were applied on Kraft, printing-grade papers at three grammage levels. The structure of the coated and uncoated (reference) papers were accessed (SEM and AFM) and IGT printing was carried out to determine the print density, print gloss, rub-off resistance, surface energy, roughness, ink transfer, dry pick resistance, water interference and set-off. The results highlight the important effect of residual lignin or type of nanocellulose on the coating layer and the development of offset printing properties. It was observed that roughness was a key factor leading to a deterioration of the print properties, predominantly affecting the NLC coating. Considering the lower hydrophilicity of NLC, an alternative dispersion with water-alcohol mixtures is proposed. By using this dispersing medium, tailorable surface coverage, surface smoothness, ink acceptance and improved printability was achieved. We show that under these conditions and compared to NHC, NLC is equally effective as a coating layer.

For improving the physical properties of old corrugated container (OCC) fiber, the laccase/histidine system was used in this paper. Firstly, the paper studied the optimum conditions that the laccase/histidine system modified the OCC fiber, including enzyme dosage, histidine dosage, reaction time, reaction temperature, and pH. Experimental results showed that the optimum reaction conditions of laccase/histidine system for OCC pulp were: dose of enzyme 1 U·g−1{\text{g}^{-1}}, 4 h reaction time, pH 4.5, dose of histidine 1 %. Under the optimum reaction conditions, the tensile and burst indexes of the sheet made from laccase/histidine treatment were increased by 25.2 % and 34.0 %, compared with that of the control sample. The SEM results showed that compared with the control sample, the fibrillation of the fiber modified with laccase/histidine was more obvious. Finally, the content of acid-insoluble lignin of the fiber was determined. The content of acid-insoluble lignin of the control sample was 29.2 %, and the content of acid-insoluble lignin of the fiber treated by laccase/histidine system in optimum reaction conditions was 16.0 %, which decreased by 13.2 %. Laccase/histidine system could improve the physical properties of recycled fiber, alleviate fiber decay, which are of great significance to solve the resource shortage and environment pollution of the paper-making industry.

A recycled newspaper pulp (NPP) was used in the adsorption of a basic textile dye (Sandocryl gold yellow, basic yellow 28: BY28). NPP was deinked and bleached for the homogeneity of the adsorbent and elimination of the anchor. The release of NPP was followed by measuring the absorbance and chemical oxygen demand (COD) in water. The NPP samples were characterized by X-ray diffraction and FT-IR spectroscopy while the morphology was visualized by the SEM technique and the chemical composition determined by the energy dispersive spectroscopy (EDS). The adsorption of BY28 on NPP was investigated by varying the contact time (0–160 min), pH (2–6), biosorbent dose (1–8 g) and initial BY28 concentration (25–200 mg L −1 ); the results show a good yield in the pH range (4–7). The adsorption isotherms were studied by the Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Tempkin models. A maximal NPP adsorption capacity of 91.21 mg g −1 at 20 °C was obtained. The kinetic study showed that the best fit is obtained with the pseudo second order model that correlates suitably the experimental data well.

In this work, a novel environmentally friendly lignin-based adhesive crosslinked with a furfuryl alcohol–glyoxal resin and epoxy resin (EPR) was used to bond particleboard. The results of 13 C nuclear magnetic resonance and matrix-assisted laser desorption–ionization time-of-flight mass spectroscopy indicated that furfuryl alcohol and glyoxal reacted under acidic conditions and that–CH–(OH)–groups may be involved in the crosslinking of the lignin–furfuryl–glyoxal resin, which also easily crosslinked with EPR. The IB strength of the particleboard bonded with LFG + 9 % EPR adhesive was better than that of the particleboard bonded with lignin–furfuryl alcohol (LF) adhesive. Moreover, the modulus of elasticity of the LFG + 9 % EPR adhesive was higher than that of the LF and phenol-formaldehyde adhesives.