جستجوی مقالات مرتبط با کلیدواژه « بازیافت » در نشریات گروه « صنایع چوب و کاغذ »

Considering the special position of biomass in providing energy in today's world and the increasing use of these renewable resources, it is expected that the production of ash will increase in the future. Therefore, the importance of biomass ash management and recycling regarding environmental and economic aspects has become more apparent. In this study, the properties of ash obtained from different lignocellulosic biomasses were investigated. For this purpose, two methods of electric furnace and open-air combustion are utilized to prepare ash from six types of lignocellulosic biomass, including rice husk, wheat straw, tree branches, MDF waste, recycled fibers from MDF waste and waste paper pulp. The content, dimensions, color, pH and chemical composition of different biomasses were investigated. The lowest content of ash was observed in recycled fibers and the highest amount of ash was observed in rice husk. All the ashes were alkaline. The color of the ashes obtained by the electric furnace method was brighter than that of open-air combustion. The smallest dimensions of the ash particles were related to the pulp ash of the electric furnace method and the largest dimensions were related to the branch ash obtained by the open-air method. The chemical compositions of the ashes were different. The obtained information is useful in determining the appropriate application of ashes.

Sticky contaminants represent one of the biggest technical challenges in the paper recycling process. These contaminants reduce paper strength, cause plugging of wires and felts, and stick to or deposit on machine parts affecting the runnability of the paper machine In this study, firstly, the sticky deposit of Docter blade dryer blades was subjected to multi-stage extraction with alcohol, aceton, toluene, and tetrahydrofuran solvents respectively. Then the nature of the resulting material and its physicochemical properties was investigated with FTIR analysis, GC-MS, TGA, XRF, SEM.. The results showed that the deposite originates from fiber, polymers such as polyvinyl acetate and styrene butadiene, which are components of hot melt adhesives, and fatty acid/resin esters. Fatty acids and resins are the most common organic compounds in stickies deposite. the possible origin of these compounds are chemical substances (saponified fatty acids), deinking steps and some resins and fatty acids used in the formulation of adhesives or more resistant resins and extractive materials related to Cellulose fibers. The observed minerals are mainly calcium, iron, silica and aluminum, which are present in the formulation of fillers and coating pigments during the papermaking process

Efficient approaches to eliminate or neutralize stickies is one of the topics of recent research. In the current study, some of the most conventional chemical and physical strategies in controlling these contaminants were compared. Control of micro-stickies originated from recycling of OCC using some selected physical approaches (washing, washing-flotation, flotation-washing and flotation) and some selected chemical methods by 4 fixing agents (Alum-PAC-pDADMAC-Cationic Starch) at 0.1-0.5-1 % dosing levels based on oven-dry weight of pulp were investigated. Electrical conductivity, TDS, turbidity, dissolved and colloidal substances (DCS) and COD were measured and compared to evaluate the efficiency of each approaches of micro- stickies removal. The results indicated that the lowest value of electrical conductivity and TDS in the physical methods was related to the flotation-washing stage and in the chemical methods was related to cationic starch 1%. The lowest amount of turbidity in the physical methods was observed in the washing and washing-flotation. Besides, the potential of secondary stickies was the lowest in the washing stage, while the flotation method had the highest potential of secondary stickies. Among the different dosing levels of the fixing agents, the lowest level of turbidity and DCS was determined for pDADMAC with 0.1% addition level, and the lowest amount of potential of secondary stickies was observed for Alum with 0.5% dosage. Both in the physical and chemical methods turbidity and DCS in pH4 was more than neutral pH. In the chemical approach with cationic starch dosage at 1% and in the physical method with the washing-flotation stage, the lowest amount of COD was reached

In this research, producing packaging paper by utilization of various recycled fibers was investigated. Also, the effect of using starch on the characteristics of manufactured papers and the effect of refining on the properties of the papers made from fibers recycled from MDF wastes were studied. Paper samples were produced in grammage of of 75, 120, 127 g/m2. To be ensure of the effectiveness of the starch treatment and the differences between the chemical structure of the fibers, the infrared spectroscopy test was utilized. The mechanical properties of papers were also investigated. The results of the infrared spectroscopy test showed a slight difference in the chemical structure of different recycled fibers. Also, the results showed that the starch treatment has changed the chemical structure of the fibers well, which has led to the addition of a new peak at a wavelength of about 1100 cm-1. The results of paper properties showed the positive effect of utilization of starch. The best combination of fibers for producing paper is to use the mixture of waste paper fibers and old cardboard, and the lowest resistances were observed in papers made from the mixture of old cardboard and recycled fibers from MDF wastes. Refinement of recycled fibers from MDF wastes improved the tensile strength of the manufactured papers, but led to a decrease in the tear resistance of the manufactured papers. Generally, it can be concluded that it is possible to produce packaging paper from recycled fibers from MDF waste in composition with other recycled fibers, but in order to achieve suitable properties in the manufactured papers, it is necessary to refine them along with steaming and effective additives should be used.

In this study, the fibers contained in the medium density fiberboard wastes were recycled using a digester. These fibers were then used to produce cellulose nanocrystals. Morphology, chemical structure and resin residues on fibers were investigated. The acid hydrolysis method was utilized to production cellulose nanocrystals. The properties of nanocrystals made from virgin and recycled fibers were investigated. The results showed changes in the morphology and chemical structure of the recycled fibers. The fibers recycled using digester had better quality as compared to the recycled fibers using conventional recycling method (using autoclave). Elemental analysis showed that after recycling, resin residues remained on the fibers. Due to the shorter duration of heat treatment and the elimination of mechanical separation and better quality of recycled fibers, it can be said that the utilization of digester considered as an efficient method for recycling medium density fiberboard wastes. Investigation of nanocrystalline cellulose properties showed that there was no difference between nanocellulose produced from virgin and recycled fibers and the recycled fibers can be well utilized to production of cellulose nano crystals.

In this study properties of fibers recycled from MDF wastes as one of the potential important resources as raw materials for MDF production were investigated.
For this purpose, two different methods including ohmic heating (for 2 and 4 min) and hydrothermal method (at 105˚c for 150 min) were utilized for recycling the wastes of MDF and original fibers were studied as control sample.
The chemical composition of fibers (lignin, cellulose and hemicellulose content), as effective variable on quality of fibers was measured. Also for probing the chemical characteristic of fiber surface, FT-IR test was utilized. In addition, the wettability of fibers also was determined by measuring the contact angels between fibers surface and water drop.
The results showed that the chemical composition of fibers is changed within recycling process. Most changes were occurred in hemicellulose and extractives content. The results of FT-IR test revealed the existence of more carbonyl groups and furfural and lower amount of hydroxyl groups in recycled fibers compared to original fibers which caused by esterification process. The wettability of fibers was decreased after recycling process especially in hydrothermal method.

This paper reports the effects of recycling on physical and mechanical properties of wood flour high-density polyethylene composites. Composite materials containing HDPE, wood flour, and Maleic Anhydride polyethylene (MAPE) were manufactured and subjected to a recycling process consisting of up to four times grinding and reprocessing under industrial conditions. A wide range of analytical methods including bending tests, modulus of elasticity, impact strength, water absorption tests, fiber length measurement and also scanning electron microscopy were employed to understand the effects of recycling on wood flour-HDPE composites. The results revealed that the recycled composites had lower bending strength and modulus of elasticity values, as compared to the reference counterparts, whereas the once recycled composites showed a higher impact strength compared to both the reference and other more recycled composites. Results, as well, indicated that generally the recycled composites had lower water absorption values as compared to the reference ones.

In this study, fibers recycled via two different methods; hydrothermal and ohmic heating were used to manufacture medium density fiberboard (MDF). The purpose of this study was to determine the effect of recycling method on practical properties (bending strength, modulus of elasticity, internal bonding and screw holding in edge and surface and thickness swelling after 24 hours water immersion) of the boards. Also, a morphological analysis was done to evaluate the influence of recycling process on fiber dimensions. Also the existence of UF residues were observed by SEM.
The results related to classification and dimension analyze of fibers confirmed the negative influence of recycling process on quality of fibers. Also degree of deterioration in hydrothermal recycling was higher than that of ohmic recycling due to sever condition of heating.
Furthermore, the results showed that recycling of MDF wastes via ohmic heating method resulted in better physical and mechanical propertied as compared to the hydrothermal method. Overall results showed that MDF panels made from recycled fibers via ohmic heating method exceed the minimum values required by EN standards (EN 622-5, 2006) for all properties except thickness swelling. About ohmic heating method, increasing the time of ohmic heating led to improving the practical properties of recycled MDF boards. It was observed by SEM that much more residues of cured UF resin adhesive were existed on the surface of recycled fibers via hydrothermal method. According to the results it can be said that ohmic heating method is a useful process for recycling the wastes of MDF.

The aim of this study is investigate the effect of Tapioca and Corn cationic starch on the mechanical characteristics of paper from old corrugated containers. The paper recycling decrease its properties and affected on the paper quality. For promoting these fibers may be effective the use of different treatments. Cationic starch is effective treatment for recycled fibers Promotion.
In this study, the cationic starch of Tapioca and Corn, each at three different levels 0.5, 1 and 1.5 % and comparison with samples (without cationic stretch). Hand sheets with a grammag of 120 g/m2 were made and their strength properties were measured. As well as, the absorption rates of two kinds of starch on the pulp were calculated using the Acid- Phenol method. The results indicated that the use of 1.5% of Tapioca starch and 1% Corn starch had an optimum effect in increasing the strength of the produced paper. Concerning the comparison of these different types of starch, the tapioca starch was more effective than the corn starch.

In this research، the influence of paper drying condition، as one of the most important variable in paper recycling، on the characteristics of fibers was studied. In this respect، bagasse soda pulp was collected from Pars Paper mill in Khozestan province and handsheets were made. The control hand sheet samples were dried at room temperature and the rest of the handsheets were dried using drum dryer set at 60° C for 3 hours، 100° C for 50 minutes and 120° C for 25 minutes to reach the same moisture content as the sheets dried at room temperature. Then، these handsheets were slushed in water and the pulp properties were determined. The results showed that with increasing the drying temperature، cellulose content did not change while hemicelluloses were reduced. Although the assessment of changing the lignin content with micro kappa method showed an increasing trend، but based on previous literature، it was concluded that the result are not justified. Also، the results indicated that changing the degree of polymerization and crystallinity did not show a consistent trend، showing initial reduction following by increased values. These results were attributed to interaction effect of drying temperature and time.

Cellulose fibers undergo a series of irreversible changes i. e hornification when exposed to cycles of wetting and drying. In this study، the effect of recycling on physical and chemical properties of chemimechanical pulp (CMP) and neutral sulfite semi-chemical (NSSC) pulp was evaluated. The pulps were recycled three times. Hornification was measured by Water retention value. The results indicated that water retention value and carboxyl groups were decreased due to recycling، hornification also increased during cycles of wetting and drying. Changes in crystalline structure of the pulp during first cycle of recycling were investigated by ATR- FTIR. The crystallinity index increased to some extent، when compared to virgin pulp. Recycling influence on the fiber length was not significant. Hornification introduced as a main cause of poor properties of recycled paper. Also، reduction of carboxyl groups could be one of the causes for lowering water retention value and decrease in strengths.