ایمان اکبرپور

Over the past few years, due to the shortage of forest resources as well as the increasing consumption of paper and paperboard, many pulp and paper manufacturers have developed the use of different sources of recycled (secondary) fibers. Therefore, recycling of paper is an effective and eco-friendly way to preserve forest resources, which eventually save the natural diversity and energy. The use of biotechnology in various sectors of the cellulosic products industries such as bio-pulping, bio-bleaching, bio-deinking, bio-wastewater treatment, etc. has been considered and good achievements have been obtained in this field. One of the most important applications of biotechnology in the cellulosic industries is the use of enzymes in the processing of recycled fibers. The use of enzymatic technologies, as environmental friendly process, has led to changes in industrial processes as much as possible and indicated great potential in solving many problems of recycled fibers, especially problems related to waste paper deinking, pulp drainage rate, fiber hornification, refining and stickies materials. In general, deinking with enzymes under acidic or neutral conditions declines the chemicals usage and reduces the yellowing of recycled paper under conventional alkaline deinking conditions. Today, the use of cellulosic enzymes (cellulase and hemicellulase) and oxidative enzymes (such as laccase) as well as amylase and pectinase have shown acceptable results for deinking different types of waste paper and most experiments in semi-industrial as well as industrial units have shown that deinking with them can reduce the cost of chemicals, increase the separation of ink particles

The recycling of different paper and paperboard products can supply the major shortage of cellulosic raw materials needed for the production of pulp and paper, and it can be important from the economic and environmental point of view. Using recycled pulp in papermaking reduces the quality of the final paper. Therefore, the use of enzyme pre-treatment separately or combined sequences as well as pulp bleaching can be effective in improving the quality properties of the final paper obtained from recycled pulp. This research was conducted with the aim of investigating the effect of enzyme pre-treatment with cellulase and laccase sequence on the bleachability of the resulting pulp with hydrogen peroxide, and the quality of the final pulp after bleaching system were investigated.

At first, the mixture of waste newspaper and magazine papers were deinked using enzyme pre-treatment (combined sequence of cellulase and laccase) as well as conventional chemical method. Enzymatic pre-treatment was done as experimental treatments C1L1 (cellulase usage: 0.1% and duration time: 10 minutes; laccase usage: 20u and duration time: 120 minutes), C1L2 (cellulase usage: 0.1% and duration time: 10 minutes; laccase usage: 40u and duration time: 120 minutes), C2L1 (cellulase usage: 0.1% and duration time: 20 minutes; laccase usage: 20u and duration time: 120 minutes) and C2L2 (cellulase usage: 0.1% and duration time: 20 minutes; laccase usage: 40u and duration time: 120 minutes) under specific process conditions. Also, control pulp (without adding chemicals or enzymes) and chemically deinked pulp samples were also prepared and then bleaching of deinked pulp was accomplished using hydrogen peroxide bleaching system including 2% hydrogen peroxide, 2% sodium hydroxide, 2% sodium silicate, 0.2% DTPA chelating agent and 0.1% magnesium sulfate in separate plastic bags under process conditions of 10% consistency, 70°C temperature and 2 hours in a water bath. At the end, the optical and strength characteristics of the bleached pulp were evaluated.

The results of the evaluation of bleached pulp with hydrogen peroxide after deinking with conventional method and also cellulase and laccase enzyme pre-treatment sequences showed that the use of enzyme pre-treatment in deinking improves the overall performance of the hydrogen peroxide bleaching process and resulted in the papers with better optical and strength characteristics after bleaching compared to pulp pre-deinked by conventional chemical method. C2L2 and C2L1 pre-treatments in combined enzymatic treatments after bleaching with hydrogen peroxide led to an improvement in brightness by 11.12% (increase of about 5 units) and 9.5% (increase of about 4 units), respectively. In these pretreatments, the whiteness of the paper increased by 31.92% and 24.54% (an increase of about 9 and 6 units), respectively. Also, the yellowness of the paper decreased by 40.19% and 44.25%, respectively, and the opacity of the paper reduced by 37.74% and 23.97%, respectively. Also, in experimental runs of C2L1 and C2L2, the paper tensile index increased 29.17% and 35.64%, respectively (40.64 Nm/g and 38.7 Nm/g, respectively), breaking length enhanced by 64.42% and 99%, respectively (5.92 km and 4.89 km), and the paper burst index also increased by 70.85% and 92.37% (3.81 mN.m2/g and 4.29 kPa.m2/g), respectively. The tear indices of paper in these runs were determined on average about 6.82 mN.m2/g and 6.62 mN.m2/g, which are a little lower compared to the chemically deinked pulp after bleaching, but in the pretreatment with the combined sequence C2L1, the tear index of paper was almost equivalent to that of chemically deinked pulp.

In this study, the ability to bleaching hemicellulose-deinked pulp was investigated in comparison with conventional chemical method. Initially, the mixed recycled pulp pre-treated with hemicellulase enzyme at different levels of usage, treatment time and pH values (under other constant process conditions) was bleached and experimental runs included H2T3 (usage 0.2% (based on dry weight of recycled pulp); Treatment time 60 minutes and pH range 6.5-7) and H3T2 (usage 0.5% (based on dry weight of recycled pulp); Treatment time 50 minutes and pH range 6.5-7) were selected as the best treatments. Then, the selected pulps were bleached using hydrogen peroxide under constant process conditions and their bleachability was compared with conventional chemical pulp. Based on the results achieved, the bleachability of hemicellulose-deinked pulps was better than that of chemically deinked pulp, and the resulting papers had a higher brightness and whiteness as well as less yellowness, but the opacity of these papers was decreased during bleaching. Also, pre-treated pulps with hemicellulase showed the papers with higher tensile and burst indices after bleaching stage so that for H2T3 and H3T2 enzymatic runs, the increase in tensile index was 13.22% and 12.59%, and in burst index was 3.66% and 6.22%, respectively. While the tensile and burst indices for chemically deinked pulp after bleaching was improved by 10.17% and 16%, respectively. Also, the reduction in paper tear index for H2T3 and H3T2 enzymatic runs after bleaching was 12.45% and 8.06%, respectively, compared to chemically deinked pulp (4.44%). Based on the overall results obtained by comparing the quality properties of papers made from different pulps bleached with hydrogen peroxide, H2T3 run has resulted in more bleachability and much better optical and strength properties.

The aim of the current study was to investigate the effect of using different charges of calcium hydroxide (as an alternative alkali source for sodium hydroxide) in hydrogen peroxide bleaching system of recycled pulp on paper strength properties and chemical oxygen demand (COD) of wastewater. The pulp mixture including recycled 70% newspaper and 30% magazine was deinked using a conventional (chemical) system and then bleached using a conventional hydrogen peroxide system under specified process conditions. The results indicated that the use of calcium hydroxide was relatively effective in enhancing the paper strength properties so that at the usage range of 2-4% calcium hydroxide, no significant reduction was observed in strength properties. On the other hand, with increasing the charge of calcium hydroxide to more than 4%, the strength properties of the paper increased relatively compared to the control sample (conventional peroxide bleaching system including sodium hydroxide alkali). Maximum values of tensile (35.64 Nm/g) and burst (2.98 kPa.m2g-1) indices were determined in experimental run C5 (10% calcium hydroxide) and maximum tear index (6.88 mN. m2g-1) was observed in experimental run C1 (2% calcium hydroxide). The amount of wastewater COD was much less than the control sample when sodium hydroxide was removed completely and replaced by calcium hydroxide in hydrogen peroxide bleaching, so that with increasing calcium hydroxide usage from 2% to 10%, the wastewater COD amount was still less than the control sample. Also, the results of the evaluation of the scale amount in the experimental run included 2% calcium hydroxide in comparison with the control sample indicated that the amount of scale in the bleaching wastewater was 145.24 mg/ml with 2% calcium hydroxide and in the control sample was obtained 32.87 mg/ml.

Today, use of recycled fiber is currently an important lignocellulosic source for paper production. In conventional (chemical) deinking and bleaching processes, sodium hydroxide (NaOH) and hydrogen peroxide (H2O2) are commonly used as the active alkali and bleaching agent, respectively. In this research, the recycled waste papers (70% ONP/30% OMG) were repulped by conventional method and deinked by combined washing and flotation processes. The prepared pulps were bleached with a conventional bleaching using calcium hydroxide (Ca(OH)2), as a substitute for NaOH, at different levels of 2 (C1), 4 (C2), 6 (C3), 8 (C4), and 10% (C5). In addition to determining its optimal amount of consumption, its performance in H2O2 bleaching compared to NaOH was evaluated. Conventional bleaching with H2O2 was also performed separately in the presence of NaOH, as a basis agent (control sample), and the optical and physical properties of standard handsheets (60 gm-2) were evaluated. The results of using Ca(OH)2 in place of NaOH in recycled pulp bleaching showed that its usage was desirable in terms of brightness value and similar physical properties, compared to those of conventional H2O2 bleaching system, while improving the performance of the bleaching process in the presence of NaOH. In general, experimental runs of C1 and C2 showed the highest degree of brightness, thickness (caliper), and bulk, but with increasing the usage of Ca(OH)2 to more than 4%, the papers with weaker optical and physical properties achieved.

In the current research, enzymatic modification of OCC pulp with Bacillus sp. amylase was evaluated. Amylase was added at different levels of 0.5, 0.1, 0.2 and 0.3% (based on oven-dried weight of recycled paper) to OCC pulp under constant conditions included consistency of 10%, temperature of 50°C, time duration of 1 hour, and at a pH range of 6.9-7. To neutralize the residual enzyme, hydrogen peroxide 0.05% (based on oven-dried weight of pulp) was applied. The refining of pre-treated OCC pulp with different levels of amylase was done at the constant revolution of 2000. The dewatering and physical properties of amylase pre-treated OCC pulps as compared to control pulp (non-treated pulp with enzyme) for two refined and unrefined conditions were evaluated. Obtained results showed that amylase pre-treatment improved pulp freeness by 11-22% compared with the control sample. The highest freeness (600 ml, CSF) was achieved with 0.2% amylase. Refining of both amylase pre-treated OCC pulp and the control sample reduced the pulp freeness, but dewatering capability increased with an increase in amylase usage. The use of Amylase resulted in a paper with slightly higher caliper, higher bulk, but similar air resistance, compared with control run. An increase in amylase usage from 0.5% to 0.3% along with refining decreased caliper and bulk and increased air resistance of paper. Also, the results of the evaluation of different times of amylase treatment of unrefined OCC pulp (at a constant concentration of 0.1%) on a caliper, bulk as well as air resistance indicated that the duration of 90 minutes was the optimal time. In general, the combined treatment of amylase (0.05-0.1%) and PFI refining (at the constant revolution of 2000) indicated the pulps with better quality in terms of dewatering and physical characteristics in comparison with control OCC pulp.

Nanocelluloses, nanosized starches, and nanostructured chitins are the most abundant renewable biobased nanomaterials. These compounds were introduced as performance-enhancing agents for many future products due to their unique nanostructured properties. But, it was not yet determined how these specific properties influence biobased nanomaterial safety because they depend on many parameters. So far, few factors have been identified, such as their interactions with cells and organisms and exposure routes. Biobased nanomaterials are considered safe compounds due to their natural origin and environmental compatibility of their bulk forms. Published results on the safety of biobased nanomaterials show that they are generally not toxic to humans or the environment. However, they are not inert compounds and may also interact with the surrounding (for example, inflammatory effects in animal experiments. Among other factors, particle size and shape, aggregation characteristics, degree of branching, and specific surface properties, may affect the interactions of biological nanomaterials with cells and organisms. In addition, due to the significant variation in the properties of biobased nanomaterials, the toxicity test results obtained for the analyzed samples have been reported as valid. But this still requires more research and knowledge about the interactions of nanomaterials with living organisms. Therefore, the safety of biobased nanomaterials should be evaluated on a case-by-case basis, and the current guidelines and protocols for the use of nanomaterials need to be sufficiently developed. In addition, manufacturers of biobased nanomaterials should ensure the safety of their products during the whole life cycle of products, similar to products based on them. Nanoparticles are very reactive due to their small size and large surface area. This feature increases the risk of fire and explosion compared to larger particles. The most important methods for controlling exposure to nanoparticles are risk elimination, replacement of high-risk materials and processes with low-risk materials and processes, enclosure, engineering controls, management controls, and the use of personal protective equipment.

New group of polymers have been synthesized that are conductive of electricity so they called conducting polymers. Polyaniline and polypyrrole conducting polymers are the most important. Polyaniline is one of the most used in production of Paper- Conductive Polymer Composites that due to its low cost and easy availability of raw materials, easy synthesis, good environmental stability and controllable electrical conductivity has been considered. Conducting papers with using polymerization of Polyaniline and Polypyrrole on paper using an oxidizing agent is produced. There is a wide range of uses for paper in electrical. Examples of these applications include: insulations for integrated circuits in electronic devices, insulations for radio wires, insulations for electricity cables and transformers electricity, or as dielectric paper for various types of capacitors, electronic and optical devices, rechargeable batteries, energy storage devices, After conducting polymers investigated in this paper, different methods of preparing and conducting paper applications are discussed.

Enzymatic deinking has been suggested as an environmentally friendly alternative to complement and replace for conventional chemical deinking. In the present research, the effect of hemicellulase from Aspergillus niger has been evaluated on paper quality of mixed 70% old newspaper (ONP) and 30% old magazine (OMG) pulp. Hemicellulose was used at different charges of 0.1 (H1), 0.2 (H2), 0.5 (H3) and 1 (H4) percentages based on oven dry weight of pulp and different times of 40 (T1), 50 (T2), and (T3) under constant conditions of %10 consistency, temperature 55-60 °C at pH range of 6.5-7 and then the pulps were washed and floated. The results showed that compared to undeinked pulp (C1) and chemical deinked pulp (C2), papers with higher brightness, whiteness and appropriate opacity could be achieved at % 0.2 enzyme concentration and duration time of 60 min (H2T3) and also % 0.5 enzyme concentration and duration time of 50 min (H3T2). Also, the results of assessments indicate that the highest tensile index (32.271 and 30.017 Nm/g), breaking length (3.131 and 2.974 km) and stiffness (3.94 and 4.12 mN) were observed in treatments of H2T3 and H3T3, and the highest tear index (7.688 and 7.34 mN.m2/g) was observed in treatments of H1T1 andH1T2 respectively. These results are more desirable than paper produced with treatment samples of C1 and C2. In general, achieved results from this research indicate that hemicellulase has a good potential to improve the quality of mixed recycled ONP and OMG waste papers vs. standard conventional system.

In this research, the effect of different concentrations of Pectinase has been investigated on deinking of old newspaper (ONP). ONP re-pulped at 5% consistency for 10 min in disintegrator (with 2650 rpm). Enzymatic treatment of recycled ONP pulp was done under constant conditions (10% consistency, duration time of 20 min, pH range of 4.5-5) at different Pectinase concentrations (0.05, 0.1, 0.2, 0.3 and 0.5% based on oven-dry weight of waste paper). The optical and physical properties of the standard paper (60 g/m2) made from treated pulps with different concentrations of Pectinase were evaluated in comparison with paper produced from control pulp (untreated ONP pulp by Pectinase). The results showed that using Pectinase in deinking of ONP led to a slight increase in the brightness and the yellowness and decrease the opacity. The brightness was improved to 43.83 ISO% (about one percent increase), but the yellowness decreased to 18.61 ISO% (about 3.5 percent) with increase in Pectinase dosage from 0.05% to 0.2%. The brightness reduced and the yellowness increased at higher concentrations than 0.3% Pectinase. The highest opacity (99.49 ISO%) was achieved using 0.5% Pectinase. The results of physical properties showed that, paper air resistance and density improved with increase in Pectinase dosage. Also treatment of pulp with 0.3% Pectinase has been resulted in the papers with higher burst and tear indices compared to control pulp.

In this research, Old Magazine (OMG) recycled fiber and glass fiber (GF) were mixed at different levels of 10%, 20%, 30% and 40% (based on weight) with two levels of 50% and 60% Polypropylene (PP) and then the produced composites evaluated compared to those from net Polypropylene. On the basis of obtained results from normalization equations in different treatments done, two treatments has been selected at a point of the better physical and mechanical properties and then chemically modified by maleic anhydride Polypropylene (MAPP) at two levels of 0 and 4%. Achieved results showed that treatments including the ratios 20:20:60 and also 20:30:50 (GF, OMG, PP, respectively) were resulted in the composites with improved physical and mechanical properties. Utilizing MAPP caused to improve the mechanical properties of composites and decrease of thickness swelling, water absorption in two optimum treatments before determined. Scanning electron microscopy results showed that in the composites contain of MAPP, Fibers were desirably compounded with Polypropylene.

In the present research, the effect of different peroxide charges and reaction times were investigated in hydrogen peroxide bleaching of mixed old newsprint and old magazine deinked pulp. In the beginning, mixed recycled papers were pulped using conventional method and then deinked by flotation. In addition, deinked pulps (mixture ratio of 70% ONP and 30% OMG) were bleached with hydrogen peroxide at different charges of 0.5, 0.75 and 1% from peroxide and times of 30, 60 and 90 min under constant process conditions. The bleached pulps refined with laboratory PFI mill to freeness of 300 ml, CSF and then standard handsheets (60gm-2) were made from them. The residual peroxide existing in bleaching liquor, chemical oxygen demand (COD) of bleaching effluent and also the paper quality properties (optical, physical and strength properties) were measured according to respected standards. Obtained results indicated that with increase in bleaching times, the residual peroxide in liquor was decreased but the differences of them was insignificant (P<0.01) with increase in peroxide charge. Also effluent COD was enhanced significantly with increase in the both peroxide charges and bleaching times. When the peroxide charge and also the bleaching time were added, the paper brightness had increased significantly but opacity was not significantly changed (P<0.01). Increasing the bleaching agent of peroxide has not been shown any significant influence on the paper strength properties. However increasing the bleaching time led to significant improve in these properties.

This research was accomplished to investigate the bleaching of combined old newspapers (ONP) and old magazines (OMG) deinked by sodium dithionite. The bleaching of pulp was performed using a 0.5, 0.75, and 1% sodium dithionite and different times of 30, 60 and 90 min. The pulps were refined up to freeness of 300 ml, CSF and standard handsheets made from them. The optical and mechanical properties of paper and COD of bleaching effluent were measured according to TAPPI standard methods.The results showed that the brightness of paper was increased significantly with increase in the time and sodium dithionite charge. When the charge of bleaching agent increased, the mechanical properties of paper and COD pollution load of bleaching effluent were increased and paper bulk and opacity decreased but these changes were not statistically significant. Increasing in bleaching time from 30 to 90 min resulted in a significant improvement in tensile, burst and tear indices and decrease the opacity of paper.

This research was performed to investigate of different endoglucanase levels and enzymatic treatment times on the beatability and drainage rate of OCC pulp. Endoglucanase enzyme with different dosages including 1u، 2u and 3u (on oven dry based pulp) at different times of 0. 5، 1، 1. 5 and 2 hours under constant process conditions added to OCC pulp in two states namely refined and unrefined. Treated pulps under different conditions were evaluated at the point of beatability and drainage rates. The results showed that addition of enzyme caused to improve (confidence level of 95%) freeness and drainage rate، compared to control sample but improvement of freeness with increasing of endoglucanase dosages was not observed significantly. The results of the effect of different enzyme levels at different refining levels was shown that addition of different enzyme dosages to pulps refined at different levels، caused to improve freeness and drainage rate. With increasing the degree of pulps refining (higher levels of refining)، the effect of enzyme concentration was observed a little to improve freeness and drainage rate. Also in total refining levels، longer treatment by enzyme from up to 1 hours (using optimum dosage 1u) was led a significant effect on increasing the freeness while there was not a significant decrease of freeness at longer times than 1 hour.

This research was done to evaluate of cellulase potential to improve the physical properties and drainability of OCC pulp. The OCC pulp with 10% consistency was treated enzymatically under constant conditions of temperature 50°C for 60 min and pH range of 5-5. 5 by different levels of 0. 05، 0. 1، 0. 2، 0. 3 and 0. 5% from cellulase (based on oven dry weight of waste paper). Also OCC pulps were separately pre-treated at different times of 30، 90، 120 and 150 min at given cellulase charge (0. 3%). In addition، enzyme pre-treated OCC pulps were refined mechanically at constant revolution of 2000 rpm. The results showed that without employing refining، enzymatic pre-treatment caused to improve the pulp freeness by about 22% proportional to control sample (non enzyme treated pulp with 470 ml، CSF). Using 0. 3% and 0. 5% were resulted as same as the highest freeness (600 ml، CSF). With increase in cellulase charge from 0. 05 to 0. 3%، the paper with lower calliper and higher density was resulted. Also، in unrefined OCC pulp، use of shorter duration of enzymatic treatment (30-60 min) was resulted in a pulp with higher density and air resistance. Maximum freeness (645 ml، CSF) was attained at 90 min. Increasing the enzyme level followed by refining caused to improve pulp freeness and a range of 0. 05-0. 1% cellulase is advisable as the best level of enzyme usage.

Nowadays with regard to the need of upgrading the paper mill technology and give up the traditional processes and on the other hand، the possibility of using all wood parts، emerging technologies have been introduced. American Value Added Pulping (AVAP) is as new alternative to achieve these aims and sulfite cooking liquor is used in presence of alcohol. Addition of alcohol accelerates the pulping speed، while preserving the cellulose strength. Volatile cooking chemicals are stripped and reused in the cooking process. Energy can be obtained from precipitated lignosulfonates and hydrolyzed hemicelluloses converted to sugar. So that، up to 85. 42 million litre of bioethanol are produced annually from sugar fermentation even more than the conventional system according to estimate done. Also، energy is obtained from residual biomass and this will finally results in a energy self sufficiency in production process. The results indicate that AVAP process plan have several benefits such as high yield (at a range of 41-58%)، producing the pulp with improved bleachability and better refineability، lower operation and capital costs، the possibility of producing the more value-added byproducts (bioethanol and synthetic gases) lower energy consumption and the feasibility of planning a closed system as compared to traditional kraft and sulphite pulps. On the other hand، recovery system of cooking liquour is simpler and easier in AVAP because of the absence of sodium components.

In this study، the effect of enzymatic refining with endoglucanase was investigated on the physical and mechanical properties of OCC pulp. Collected OCC pulps were pre-treated with different endoglucanse dosages (1u، 2u and 3u on o. d. pulp) under constant conditions and then refined at different levels. The effect of different enzyme dosages and refining levels were evaluated separately on the paper physical and mechanical of properties، as compared to control pulp (non treated pulp with enzyme). In unrefined pulps، the results have shown that adding enzyme up to 1u caused to improve the physical and mechanical properties as significant (confidence level of 95%)، compared to control pulp. However using more than uendoglucanase was resulted a significant decrease in both physical and mechanical properties. Achieved results from the effect of different enzyme dosages and refining levels showed that in refined pulps، increase of enzyme level caused to produce a bulky paper and decrease of mechanical properties. In general، the best physical and mechanical properties was obtained using 1u endoglucanase at different refining levels applied.

This study was aimed to investigate the effect of different charges of sodium silicate on chemical deinking of old newspaper. Chemical deinking process was accomplished with 1% hydrogen peroxide, 1% sodium hydroxide, 0.3% DTPA and 0.15% surface active agent at different charges of 0, 1, 2 and 3% sodium silicate on the basis of oven dry waste paper. The results of the optical properties of produced paper showed that the brightness of paper improved (50.9%) and the yellowness decreased (11.33%) with increasing of sodium silicate charge to 2%. Increasing of sodium silicate use from 0.3% did not indicate significant effect on opacity values. The highest opacity (98.8%) was achieved by 1% sodium silicate. The results of the physical properties indicated that increasing of sodium silicate use up to 2% resulted the paper with the highest bulk (2.75 cm3/g). Totally, the consequences of this research in relation to chemical deinking of old newspaper at different charges of sodium silicate showed that use of 2% sodium silicate would lead to produce the paper with higher brightness, caliper and bulk along with desirable opacity.