Deinking Of Pulp Research Articles

Combining small-scale screening methods to predict microorganism floatability

Flotation is a common physico-chemical solid-liquid separation technology. It is applied in classical fields like minerals processing, pulp deinking and wastewater treatment and novel fields like biotechnology. The success of flotation is influenced by flotation key parameters. The aim of this study was to present a set of small-scale screening methods for the key flotation parameters particle size, particle hydrophobicity, bubble size and direct particle-bubble interaction. Experiments were performed with the model microorganism S. cerevisiae. Flotation was done in complex fermentation media and in isotonic saline, at varying pH and after flocculant addition. The goal, to combine small-scale laboratory methods to explain, predict and optimize yeast flotation results was achieved. Combining the methods can be used prospectively for wide screening of potential flotation additives, such as collectors, frothers and flocculants and to optimize microorganism floatability.

Bio-deinking of mixed office waste paper by Penicillium citrinum NCIM-1398 and its comparative study with conventional chemical deinking

Penicillium citrinum NCIM-1398 is a co-producer of endo β-1,4-glucanase, xylanase, and amylase enzymes. The synergistic effect of the enzymes present in the cocktail was found to be advantageous in deinking white mixed office waste (MOW) paper. Enzymatic deinking of MOW reduced the dependence on chemicals by up to 50% during chemical deinking and improved optical properties compared with the chemical deinking process. The chemi-enzymatic approach improved pulp brightness by 12.6% compared with MOW pulp. The ERIC (Effective residual ink concentration) value was reduced by up to 39.2%, whereas the strength properties of tear index, tensile index, and burst index achieved gains of 3.2%, 9.9%, and 6.2%, respectively, compared with the control. Whereas chemi-enzymatic treatment showed a reduction of 67.1% in COD and 61.8% in BOD, and there was an increase of 15.4% in total solid of effluents respectively, compared with the respective controls. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) studies revealed that the pulp was modified by enzymatic and chemi-enzymatic treatments, which facilitate ink removal during deinking of pulp.

Enhanced biobleaching efficacy and heavy metal remediation through enzyme mediated lab-scale paper pulp deinking process

The biological deinking method using microbial enzymes is quite promising and rather eco-friendly. In this paper, we discuss about the impact of enzymatic deinking of newspaper pulp using ligno-cellulosic (cellulase, xylanase and laccase) and lipolytic enzymes. The individual treatment of paper pulp with enzymes (cellulase/xylanase) could enhance the paper brightness to about 32.86% whereas combinational effect could enhance only about 28.67%. There was a release of chromophores from phenolic and hydrophobic compounds released during the deinking process. Physico-chemical parameters of effluents were also found to be within the standard limits and the metals like iron, lead and zinc were not detected in the enzyme assisted deinking effluent sample. The heavy metals in the paper pulp was found to be reduced after enzyme treatment. The obtained effluent was found have low phytotoxicity and was safe for agricultural applications. Hence, the present report was found to be a suitable enzymatic deinking process which was eco-friendly that results in non-toxic effluents. The method also provides an avenue in water resource recycling within industries.

Low Molecular Weight Xylanase from Trichoderma viride VKF3 for Bio-bleaching of Newspaper Pulp

Xylanase is a major enzyme used in the paper and pulp industries for bio-bleaching applications. There are possibilities for xylanase with better properties suitable for industrial applications. This paper focused on a potential xylanolytic fungus, Trichoderma viride VKF-3, obtained from a mangrove soil sample. Optimum conditions for xylanase production were tested by culturing T. viride VKF3 under varying carbon and nitrogen sources, medium pH, and incubation temperature. The isolate T. viride VKF3 achieved a maximum of 3.045 IU/mL of xylanase activity by utilizing coconut oil cake as a substrate. During purification, 84% yield was obtained with 40% ammonium sulphate. The enzyme activity was confirmed through zymogram analysis, and a band was observed at 14 kDa. The xylanase facilitated maximum hexenuronic acid release with a 30% enzyme dosage following 4 h of incubation. Moreover, the Kappa number tended to decrease with increased enzyme dosage and incubation time. There was a Δ brightness of 11% following 4 h of enzymatic treatment. Strength properties, such as the tensile, burst indices, and folding endurance, was improved during the xylanase assisted deinking of pulp. Hence, the present xylanase was found to be suitable for the bio-bleaching of newspaper waste via an eco-friendly process.

Production of thermo-alkali-stable laccase and xylanase by co-culturing of Bacillus sp. and B. halodurans for biobleaching of kraft pulp and deinking of waste paper.

To reduce pollution and cost of treatment for fresh and recycled paper, co-production of xylanase and laccase was carried out in the same production medium using two compatible species of Bacillus. These co-produced enzymes were used for deinking of old newsprint (ONP) and biobleaching of eucalyptusKraft pulp. Solid-state co-cultivation of Bacillus sp. and B. halodurans FNP135 was optimized statistically by response surface methodology for the co-production of xylanase (X) and laccase (L). A significant increase in production of xylanase (2.1-fold, 1,685IU/g) and laccase (2.04-fold, 2,270nkat/g) was observed under optimized conditions viz. pH (10.5), inoculum size (10+10%) and moisture:substrate ratio (0.8:1). Both the enzymes showed identical temperature and pH optima of 70°C and 9, respectively, and were used for deinking of ONP pulp and biobleaching of kraft pulp. In case of ONP pulp deinking, the XL treatment increased brightness (11.8%), freeness (17.8%), breaking length (34.8%), burst factor (2.77%) and tear factor (2.4%). In case of kraft pulp biobleaching, XL treatment showed a significant increase in brightness (13%), whiteness (106.15%) breaking length (49%), burst factor (6.9%), tear factor (23%), and viscosity (11.68%) and reduction in kappa number (15%) after alkali extraction and peroxide stage. This enhancement of pulp properties revealed a synergistic effect of xylanase and laccase produced in one setup.

Enzymatic deinking of secondary fibers: cellulases/hemicellulases versus laccase-mediator system

The use of enzymes has been suggested as an environmentally friendly alternative to complement conventional chemical deinking in the recycling of recovered paper. This study compares the use of cellulases/hemicellulases versus the laccase-mediator system for deinking printed fibers from newspapers and magazines. For this purpose, two commercial enzyme preparations with endoglucanase and endoxylanase activities (Viscozyme Wheat from Aspergillus oryzae and Ultraflo L from Humicola insolens, Novozymes) and a commercial laccase (NS51002 from Trametes villosa, Novozymes), the latter in the presence of synthetic or natural (lignin-related) mediators, were evaluated. The enzymatic treatments were studied at the laboratory scale using a standard chemical deinking sequence consisting of a pulping stage; an alkaline stage using NaOH, sodium silicate and fatty acid soap; and a bleaching stage using hydrogen peroxide. The handsheets were then prepared and their brightness, residual ink concentration, and strength properties were measured. Among the different enzymatic treatments assayed, both carbohydrate hydrolases were found to deink the secondary fibers more efficiently. Brightness increased up to 3-4% ISO on newspaper fibers, being Ultraflo 20% more efficient in the ink removal. Up to 2.5% ISO brightness increase was obtained when magazine fibers were used, being Viscozyme 9% more efficient in the ink removal. Regarding the laccase-mediator system, alone or in combination with carbohydrate hydrolases, it was ineffective in deinking both newspaper and magazine fibers, resulting in pulps with worse brightness and residual ink concentration values. However, pulp deinking by the laccase-mediator system was displayed when secondary fibers from printed cardboard were used, obtaining up to 3% ISO brightness increase and lower residual ink concentrations.

Acoustic microcavitation at surfaces: New results in deinking of paper

Deinking remains an important step in environmentally conscious manufacturing of paper. A novel method based on acoustic microcavitation is used for deinking xerographic ink from paper. Microcavitation evolves microimplosions, which are effective in causing deinking preferentially at ink sites. Acoustic microcavitation is brought about by low megahertz acoustic fields giving rise to micron-sized bubbles that live a few microseconds. In exposing a surface to continuous waves for a defined duration one could obtain cavitation effects in an average, overall sense; the details of nucleation, evolution of inertial events, and the precise interplay of field parameters in effecting cavitation, however, get glossed over. Studying pulsed cavitation using tone bursts at low duty cycles, instead of CW insonification, reveals interesting details of the initiation and evolution of acoustic microcavitation. Experiments indicate that the 2-D context of how a xerographic print is deinked might be useful in inferring some attributes of 3-D pulp deinking. Assuringly, the results indicate that paper fibers are entirely undamaged, and the ink separation leaves them immaculately white, and that acoustic methods for deinking are a viable, chemical free, environmentally responsible means of recycling paper.

Physicochemical characteristics of a new organic soil conditioner from composted sludges from a pulp deinking process

A new organic soil‐conditioner from composted sludge produced from a newspaper deinking process was examined compared with raw uncomposted sludge, its physical and chemical characteristics tested in order to study its effectiveness. The water‐holding capacity of the conditioner was almost 7.6 and 1.8 times higher than that of the pure soil and the raw sludge, respectively, and remained stable at temperatures between 9°C and 27°C. The composted sludge had a 53% organic matter content and 35% in humic substances which was 3.5 and 2.0 times lighter than the pure soil and the raw sludge. Incorporation of this‐material into the soil in concentrations of up to 25% resulted in a 1.7 times increase of the water‐holding capacity of the mixture, whereas 90% of the water‐holding capacity was achieved in less than 10 min. The apparent density of the mixture was decreased and was not affected by the residence time of the samples into the water. The pH of the mixture's eluates was shifted to higher values (pH=7.0). The specific conductivity of the eluates was increased. Due to this parameter, a limit was observed in the use of this conditioner. The amount of ammonium‐nitrogen (NH ‐N), phosphorus (P), calcium (Ca), magnesium (Mg), zinc (Zn), copper (Cu)4, and manganese (Mn) in the eluates increased, while the amount of potassium (K) and iron (Fe) decreased in comparison to what would be expected from the separate contributions of soil and conditioner. Therefore, there exists an interaction between this material and soil that occurs when the conditioner is incorporated into soil.