Volume 35, Issue 3

Sulfide ions (S −2 ) derived from Na 2 S in black liquor, after the pulping process, is the source of production H 2 S during of black liquor recovery cycle in Kraft pulp and paper industries. Tow adsorbents (Cu-PAC, Cu-GAC) by loading Cu +2 on powder activated carbon (PAC) and granular activated carbon (GAC) were synthesized to created more adsorption sites and were improved their selectivity for removing S −2 from black liquor with 3 level of sulfidity (18, 20 and 22 %). The adsorbents were characterized by BET, FTIR, SEM, and EDX. Adsorption of S −2 for Cu-PAC and Cu-GAC were fitted well with Freundlich and Langmuir isotherm model respectively and both of the adsorbents followed pseudo-second-order kinetic. The results of thermodynamic parameters showed the endothermic process. The removal efficiency results showed Cu-PAC has better performance than Cu-GAC. This is due to the higher specific surface area of Cu-PAC, which has led to more adsorption sites for S −2 . By considering appropriate temperature conditions and direct effect of the S −2 on the production of H 2 S during of black liquor recovery cycle, Cu-PAC will be able to prevent H 2 S production and odorous the black liquor recovery cycle by removing 79.89 % of the S −2 .

Effect of different proportions of bark in mixed hardwood (about 70 % eucalyptus and 30 % poplar) chips on pulp and papermaking properties was studied. Increased proportion of bark in raw material chips resulted in increased active alkali consumption, increased reject content in pulp and reduced pulp yield after kraft pulping. The unbleached pulp obtained with higher proportion of bark in mixed hardwood chips also has higher kappa number, lower brightness and viscosity as compared to pulp obtained with bark free mixed hardwood chips. The soda loss and ash content in pulp were severely increased from 12.8 kg/t to 312 kg/t of pulp and 0.7 % to 21.1 %, respectively with the increase of bark portion from 0 to 100 % in raw material furnish. The physical strength properties like tensile, burst and tear indices in the pulp obtained from bark were reduced by 58.5 %, 60.7 % and 68.4 %, respectively as compared to that with bark free mixed hardwood.

Cellulose can be directly dissolved in cold alkali without derivatization. However, this requires low cellulose molecular weight, i. e. low pulp viscosity, preferably below 300 mL g −1 . This can be achieved by for example acid or enzymatic hydrolysis of the dissolving pulp. However, it would be beneficial to manufacture pulp with sufficiently low viscosity without an additional treatment stage prior to dissolution. Unit processes in pulping can be operated in such a way as to reduce the molecular weight of cellulose. The approach of the study was to modify the conditions in unit pulping processes in order to obtain a low pulp viscosity of fully bleached prehydrolysis kraft pulp. A high charge of alkali in the oxygen delignification reduced the cellulose molecular weight significantly. Increased temperature, 120 °C compared to 98 °C, had also a significant effect on viscosity. By performing peroxide bleaching at acidic pH, the viscosity could be sufficiently reduced even when oxygen delignification was performed at lower temperature. However, for high brightness, a chlorine dioxide stage is needed.

Chlorine dioxide is classified by the World Health Organization as a fourth-generation A1, widely used, safe, and effective disinfectant. It is widely used in bleaching, water treatment, oil extraction, aquaculture, plants, fruits and vegetables, meat products, preservation of aquatic products, food sterilization and sterilization industries. The technology of chlorine dioxide produced by the combination reduction method is widely used in domestic papermaking related companies. In order to promote the application of chlorine dioxide, the effects of storage conditions on the stability of chlorine dioxide solution prepared by the combination reduction method and the experimental study of decomposition kinetics were studied. Experiments have shown that high temperature, high pH and high initial concentration accelerate the decomposition of chlorine dioxide solution, and the addition of sodium dihydrogen phosphate (NaH 2 PO 4 ) and dimethyl sulfoxide (DMSO) can inhibit the decomposition of chlorine dioxide. The kinetic experiments showed that the decomposition rate of chlorine dioxide was secondary to ClO 2 and was −0.406 for [H+][{\mathrm{H}^{+}}]. The apparent activation energy of chlorine dioxide solution decomposition reaction was 26.7 kJ·mol −1 , and the decomposition rate equation of chlorine dioxide was established.

To verify a linear relation between normalized mechanical property and moisture ratio, in-plane tensile tests were performed on four types of paperboard from different manufacturers. Tensile properties were normalized with respect to the property at standard climate (50 % RH, 23 °C). Short-span Compression Tests were also performed to investigate if the relation was linear also for in-plane compression. The tests were performed at different relative humidity (20, 50, 70 and 90 % RH) but with constant temperature (23 °C) in MD and CD, respectively. The linear relation was confirmed for the normalized mechanical properties investigated. In fact, when also the moisture ratio was normalized with the standard climate, all paperboards coincided along the same line. Therefore, each mechanical property could be expressed as a linear function of moisture ratio and two parameters. Moreover, an in-plane bilinear elastic-plastic material model was suggested, based on four parameters: strength, stiffness, yield strength and hardening modulus, where all parameters could be expressed as linear functions of moisture ratio. The model could predict the elastic-plastic behavior for any moisture content from the two parameters in the linear relations and the mechanical properties at standard climate.

This work reports the evaluation of a tactile sensor for the potential of using it to measure the compliance of folding cartons. A tactile sensor would make it possible to measure the mechanical behavior locally around the contact point, in contrast to existing methods that measure the global mechanical behavior of the carton. Research on the haptic sense has shown that the local mechanical behavior is more important than the global behavior when humans assess compliance of objects. It is shown that the response of the tactile sensor correlates strongly with the bending stiffness of the board, but also with geometric features. A method for reducing the 22-dimensional output of the sensor to single meaningful feature using linear discriminant analysis is proposed and tested. The results show that the sensor is a good candidate for a method that incorporates both cutaneous and kinaesthetic information in the measure of carton compliance.

The present work reports on a method for the determination of hydrophobic degree of paper packaging material by tracer-assisted headspace gas chromatography. The method was based on adding 40 μL of methanol-water drop on the paper surface for 20 s. After removing the excess water by turning the sample vertically, the sample is placed in a vial and the amount of residual tracer attached on the material surface was accurately quantified by full evaporation headspace gas chromatography. The results show that the present method has a good precision (less than 4.1 %). The present method is simple and accurate and it can be an efficient tool for testing the hydrophobic degree of paper packaging material in batch.

Two wet-end starches (potato and barley), one surface sizing starch (barley) and one coating binder starch (barley) were jet-cooked. Samples were collected and stored at 90, 60 and 40 °C. 1 H NMR-relaxometry and viscometry were used to monitor the jet-cooked solutions as they cooled to room temperature. Samples stored at different temperatures were also monitored using 1 H NMR-relaxometry and viscometry. A sediment formed into the surface sizing and coating binder starches stored at 90 °C. The sediment and supernatant were separated and collected, and measured using 1 H NMR-relaxometry. The T2{T_{2}} relaxation rates of jet-cooked starches showed significant differences between potato and barley starches, as had also been examined in previous studies. The NMR method was also sensitive to differences in solids content and chemical modification (degree of cationization, degree of oxidation and molecular weight). The cooking temperature, cooking speed and viscosity did not influence T2{T_{2}} relaxation rates. The sediment separated from the surface sizing and coating binder starches held at 90 °C had a significantly higher relaxation rate than the supernatant, indicating that the sediment contained a high amount of retrograded starch.

A synergistic process with steam explosion pretreatment (SEP) followed by sodium carbonate-oxygen cooking (SCOC) upon bamboo was evaluated for its effect on separating hemicellulose and lignin from bamboo while preserving cellulose, providing cellulose substrate susceptible to chemicals in producing platform chemicals such as levulinic acid. The results showed that through the SEP with 2.5 MPa for 10 min, the hemicellulose content reduced by 60.85 %, the specific surface area of bamboo fiber increased to 1.9494 m 2g-1 from 0.8061 m 2g-1 of raw material. The synergistic SEP-SCOC significantly removed 73.33 % lignin, and yielded 73.9 % cellulose under the optimal condition of SEP with 2.5 MPa for 10 min and followed by SCOC with 30 % total titratable alkali (TTA) at 180 °C for 2 h and 2 MPa oxygen pressure. The results also proved the total lignin removal was improved by 8.07–18.95 % for the steam exploded bamboo fibers than the untreated one, indicating SEP increased the accessibility of cooking reagents to fibre during subsequent SCOC process. Furthermore, the low value of biological oxygen demand (BOD) and chemical oxygen demand (COD) in the final spent liquor indicated the lower pollution level of the process.

Paper strengthening agent is more and more important in the current papermaking industry. In this study, carboxymethyl starch-grafted-polyacrylamide (CMS-g-PAM) was synthesized via grafting polyacrylamide onto carboxymethyl starch (CMS), and added in a recycled pulp furnish to make handsheets. The structure and surface morphology of CMS-g-PAM were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy. The effects of CMS-g-PAM dosage and addition way on the properties of the paper were investigated. The results showed that CMS-g-PAM could improve the paper mechanical properties through both wet end addition and surface spraying, and surface spraying had a better improvement at the same dosage. CMS-g-PAM was more effective in improving paper mechanical properties than CMS, when it comes to the same addition way and the same dosage. SEM analysis demonstrated that CMS-g-PAM could increase the inter-fiber bonding.

The work presented in this paper is focussed on study of structure and properties of coating layers based on natural pigments (ground calcium carbonate and clay) and butadiene acrylonitrile latex as binder in correlation with functional properties of the final coated paper. It is quantified the influence of binder content and pigment type on the structural and liquids penetration properties of coating layer. The obtained results confirm that by increasing of binder content in the coating formulations a reduced efficiency of light-scattering and increased roughness for coated surfaces is obtained. At the high binder amounts (over 15 pph), the coating layer porosity is reduced and as result a lower liquids penetration in the coated papers is obtained.

With the increasing popularity of coated paper, it has been more widely used in printing, publishing, product packaging and commercial promotion. However, coated paper is prone to cracks after printing and folding which exposes to a white area which is referred to as fold cracking. This study investigated the coating properties of paper and coating factors influencing the fold cracking and aimed to provide guidance on how to reduce the problems of fold cracking. This paper mainly discusses the effects of pigment proportion, binder dosage, solids content, coating thickness and calendering pressure on fold cracking of coated paper after printing. Experiments show that when the coating consisted entirely of calcium carbonate, the degree of fold cracking is most serious. With the addition of kaolin, the fold cracking reduces. When the ratio of the number of parts of calcium carbonate to kaolin is 25/75, the area of fold cracking reaches its minimum value of 10.28 %. With increasing solids content of the coating, the fold cracking decreases initially and then increases. When the solids content is 55 %, the fold cracking reaches a minimum. Increased latex content reduced coating thickness and an increase in calendering pressure gradually reduce the degree of fold cracking.

Coatings are generally applied for opacity, smoothness and gloss on the paper surface. Pigments such as CaCO 3 , Kaolin-Clay and Zeolite are used, and natural or synthetic binders are used. In this study, coatings using the CaCO 3 , Kaolin-Clay and Zeolite pigments on 80 gr/m 2 high grade papers were made. PVOH was used as binder. Following coating, papers were processed through supercalendering and printed with inkjet printer. Using INGEDE method 11p. recycling process printed papers were deinked. The optical properties of the recycled papers obtained after the deinking treatment, were compared with the unprinted papers. At the end of the study, the effect of coating on paper surface and the recycling performances of the inkjet printed papers were revealed. It was determined that the papers in which zeolite was used as a pigment were better, in terms of both surface properties and recycling performance when surface properties and recycling performance of coated papers were examined. When all the results were compared, it was found that the performances of coatings for which zeolite was used were much better than coatings such as CaCO 3 and Kaolin-Clay, both in terms of surface coating properties such as opacity, roughness and gloss and recycling results such as brightness.

Flexographic sleeves are made using various materials, including a sub-group with extremely durable polyurethane foam shock-absorbing layer. During exploitation, the sleeves are exposed to cyclic dynamic loading, and the flexographic printing process is highly sensitive to the changes in pressure. Deformation of printing elements occurs due to the almost two times higher residual strain of the exploited sleeves. Changes in the residual strain induce occurrence of the hysteresis losses, which lead to heat generation. The forces impacting the material are not strong enough to induce permanent deformation in the microstructure. Therefore, the leading cause of the change lies in the molecular structure of the parent polymer of the polyurethane foam cell walls, whose resilience is declining. The thickness of the exploited sleeves tends to be around 8 % lesser. In addition to high-frequency cyclic loads during printing, the adhesive layer of self-adhesive sleeves undergoes reduction in the share of acrylates, phthalates and rosin, thereby reducing the adhesive strength and the force needed to initiate the de-adhesion by half. The knowledge of mechanisms of change in certain characteristics of the sleeves enables predicting their service life and increasing the stability of the printing process through possible corrections of other process parameters.

Using the acclimated activated sludge from the pulping middle-stage effluent, the effect of pH shock on the micro-oxygen activated sludge system with a nano-magnetic powder/graphene oxide composite was studied. The results showed that the removal rates of chemical oxygen demand (COD Cr ) and ultraviolet adsorption at 254 nm (UV 254 ) decreased. Also, the sludge settling performance was poor due to the impact of pH, but the impact resistance of nano-magnetic powder/graphene oxide group (MGO group) was higher and the recovery was faster. Results of high throughput sequencing indicated that the diversity of microbial community was reduced by the impact of pH, but it was significantly higher in MGO group than in the blank group. The dominant bacteria after pH shock or recovery in both of the system had a large difference. The percentage of the dominant bacteria in the MGO group was higher than that in the blank group. The MGO group had higher electron transfer system (ETS) activity which made the system having a strong pH impact resistance.

The fundamental reason for the environmental pollution caused by the papermaking industry is the inadequate treatment of the black liquor. How to dispose of the lignin macromolecules, which is the main pollutants in the black liquor, is the key to addressing the environmental pollution. At present, cross-flow membrane filtration is one of the effective ways to retain and recycle lignin macromolecules in black liquor. The paper proposes the adoption of a dynamic blade cross-flow membrane filtration equipment provided by German BOKELA company to treat papermaking black liquor. The experiment shows that when the black liquor is treated with dynamic blade rotation cross-flow, the membrane with a molecular weight cut-off of nanofiltration (NP010) delivers the best retaining effect, with 28 % more lignin in black liquor than that in untreated black liquor. Meanwhile, when the blade rotational speed reaches 300 rpm and the transmembrane pressure is 0.5 or 2 bar, the flux of black liquor through nanofiltration NP010 is relatively desirable.

The bleaching sector of the wood pulp industry is its largest effluent generator. The aim of this study was to reuse the bleaching filtrate in order to reduce water consumption. The experiment was conducted by simulating the D 0 (EP)D 1 bleaching sequence and recirculating different amounts of filtrate from the oxidation stage to control the pulp consistency of the delignification stage (pre-O). Physical, mechanical, chemical and optical properties of the pulp were studied. The accumulation of the non-process elements (NPE) and their effects were evaluated with the Aspen-Plus® computer simulator. The results of the computational modeling were satisfactory. The recirculation of filtrates increased the saturation index of the system by 19 %, but remained at sub-saturation levels. The pulp viscosity and elongation remained statistically stable. Recirculation of up to 50 % of the filtrate did not produce differences in pulp brightness; however, there were slight losses in the pulp resistances. In order to maintain 84 % ISO brightness, there was a higher consumption of the bleaching reagents. Up to 50 % of recirculation of the filtrates was accomplished without jeopardizing the system and the pulp quality and resulted in a savings of 55 m 3  h −1 of water – 7 % of the consumption of the entire mill.

Slippery liquid-infused porous surfaces or SLIPS were first introduced in 2011 by Wong et al. who reported a bioinspired self-repairing surface with remarkable slippery properties. Generally, production of these surfaces includes fossil-based or expensive materials and processes that are available mainly in laboratory scale. In this study, slippery surfaces with sliding angles of less than 10° are obtained using fibre-based material – paperboard – that is commercially available in large-scale and also cheap compared to substrates generally used in this field. The hierarchical nanostructure that is a necessary condition for appropriate droplet mobility was obtained by the liquid flame spray method. This method is fast, scalable, has a variety of optimization parameters and can be utilized in roll-to-roll technology that is traditional in paper industry. In this work, paperboard serves not only as a substrate, but also as a reservoir for the lubricant, thus it is important to evaluate the affinity of the material for the oils and estimate the capillary movement. Therefore, Cobb and Klemm methods were used when choosing a paperboard material. In addition to synthetic oils, rapeseed oil was also utilized as a lubricant, which potentially leads to eco-friendly and recyclable slippery liquid-infused porous surfaces.