جستجوی مقالات مرتبط با کلیدواژه « brightness » در نشریات گروه « جنگلداری »

presented researches during recent years, showed that using biotechnological base methods, specially using industrial enzymes for processing of waste papers is considered as a suitable approach to improve optical and mechanical properties of recycled papers. In this research deinking of offset printed waste newspapers using lipase enzyme was studied.
In this research enzymatic deinking of the recycled newspapers was investigated using lipase at three-time level as 60, 120 and 180 min, and three level of enzyme use as 3, 6 and 9 U/g O.D pulp at neutral pH value. Washing method was used to remove ink particles.
Comparison of the optical, physical and strength properties of the made handsheets showed that enzymatically deinking could enforce the strength properties (tear and burst strengths) in the related handsheets compared to those of the control sample. In addition, lipase-deinked pulps showed higher brightness and lower yellowness than the control sample. However, opacity of enzymatic treated pulps decreased with prolongation of treatment time compared to the control sample.
It can be generally concluded that enzymatic deinking using lipase is an appropriate method to improve the optical and strength properties of offset printed waste newsprints. It seems that increasing the amount of enzyme treatment in more than 9 units of enzyme per gram of dry pulp had a significant reduction in the opacity content of dry pulp compared to the control sample and Increasing the treatment time will also be effective in this reduction.

Background and goals: This research changed into achieved with the intention of manufacturing dissolving pulp or alpha-cellulose from bagasse. Alpha-cellulose is generally used for making cellulose derivatives with advantage of being soluble in commonplace solvents in recognize to cellulose. Dissolving pulps have high alpha-cellulose and brightness, but very low hemicelluloses, ash, and extractives, with uniform molecular weight distribution.
Substances and Bagasse chips were pretreated beneath slight acidic situation the use of acetic acid at most temperature of a hundred 165 ºC, to obtain yield loss stages of approximately 20 and 30 percent in pre-extraction level. Bleachable pulps at kappa wide variety decrease than 12 had been created from each the pre-extracted samples, the usage of soda-AQ pulping technique at most cooking temperature of a hundred 165 ºC. The pulp samples produced under optimum situations, have been bleached by chlorine free bleaching (ECF) with AD0EpD1P bleaching sequence. The properties have been decided on the basis of policies TAPPI. In the end, a statistical evaluation of the effects of exams finished on dissolving pulps created from SPSS software program and t-test two samples become used. in this look at, dissolving pulp carries numerous alpha-cellulose from depithed Bagasse with acid pre-extraction and the soda-AQ pulping procedure turned into prepared. While that within the acid pre-extraction yield loss improved from 20 to 30, the alpha cellulose production increased but the degree of polymerization declined. In produce dissolving pulp, in addition lignin, hemicelluloses are also undesirable impurities, so the more material will be removed from the purity cellulose pulp increases, but with increasing destruction of the hemicellulose in the pre-extraction, may be cellulose chain additionally damaged, although alpha-cellulose to increase the degree of polymerization to be associated with high drop. Bagasse dissolving pulp having ninety two percentage alpha-cellulose with DP of 870, can also have restrained packages in making derivatives such as cellulose acetate and cellulose nitrates, however it is able to be used to supply decrease demand products such as viscose rayon and carboxymethyl cellulose. But, the yield and ash dissolving pulp were first-class. The outcomes of this studies evaluation with other research inside the discipline of dissolving pulp manufacturing and additionally considering that the bagasse produced in massive quantities inside the south of the united states, imparting a number of the pulp or alpha cellulose the used inside the manufacture of viscose rayon, as a minimum, can be planned based on bagasse as uncooked cloth.

The old newsprint, as an important grade of waste papers, usually has been produced from chemicalmechanical pulp (CMP). Although the effect of paper aging on different properties of recycled pulp has been investigated from long time ago; but, few studies have been observed about the effect of this phenomenon on recycling of CMP paper. In this study, accelerated aging was applied on Hardwood CMP newspaper by 2 levels of temperature (50 and 100˚c) and 2 levels of time (24 and 48 hours). Results showed that accelerated aging applying 100˚c in 24 and 48 hours (about half of a decade and more) impose an intense reduction tensile strength, burst strength and tear strength indices as well as folding endurance strength of recycled pulp. Also, accelerated aging in 50˚c for 24 and 48 hours (about six months until one year) did not show any special effect on mentioned mechanical properties. Moreover, thermal accelerated aging didn’t have any significant effect on brightness of deinked CMP pulp. In general, it can be concluded that CMP waste papers less than one year old can preserve or even upgrade their mechanical properties after recycling, but aging more than half of a year will have detrimental effect on these properties

Some extractive compounds from wood, adhesives which are difficult to remove during pulp washing and cause adhesive residues on process equipment. In preparing pulp from hardwoods, These compounds are the source of numerous problems such as the formation of sticky materials, impurities remain in the paper pulp and paper break in paper machine. In addition, remain these compounds on paper caused problems such as creation dark spots and paper fibers stick on the cylinder surface, paper breaks and clogging with and felt. Also the extractives may react with chemical bleaching and produce changed and oxidized products. Changed extractives are causing pitch problem and have a negative impact on pulp brightness. In this study, the effect of hot water and alkali pretreatment on bleach ability of hornbeam CMP pulp was studied.
Methods and materials:Hornbeam wood chips prepared from Mazandaran wood and paper mill. Treated with hot water and alkali done in three levels of 0.5, 2 and 3.5 percent with the aim of removing the extractives before pulping process and then prepared pulp from control and pre-treated wood chips with the same conditions and CMP process and bleached with hydrogen peroxide. Handmade paper produced from the resulting pulp and papers optical properties before and after bleaching and strength properties of produced papers before bleaching was examined.
The sample pre-treated with stable temperature and time, the mass loss during pretreated with hot water is less than pre-treated with alkali and in the alkali treatment, the mass loss increased with increasing alkali percent. In both pretreated cases, pre treated hornbeam chips pulp yield is more than control sample. The refining rounds and energy consumption of paper pulp produced from alkali pretreated chips is more than pulp from wood chips pre-treated with hot water. The brightness of hot water and alkali pre-treated samples before and after bleaching Increased compared to the control sample. During alkali pre-treated, with increasing the percentage of alkaline, pre-treated samples also showed an increase brightness. Before bleaching, opacity of sample pre-treated with hot water had low increase and in general, significant differences between the samples treated with hot water and control at the level of 5% was no observed. The sample pre-treated with stable temperature and time, the hornbeam tensile index increased. Pretreatment with alkali also increases the tensile index. Burst index increased by hot water pretreatment. Pre-treated with alkali also increase burst index. Samples pre-treated with hot water and alkali showed that tear index increased and rised with the alkaline percentage increase.
Hornbeam wood chips pre-treated with hot water and alkali caused wood chips mass reduce and increase CMP wood pulp yield compared to the control. Brightness of pretreatment samples before and after bleaching increased than the control sample. Opacity in the samples pretreated with hot water increased and decreased during the treatment with alkaline solution. In those pre-treated with hot water and alkaline solution than the control sample, hornbeam paper pulp tear index increased but in burst index and tear strength was no difference significant.

The pulp color reversion, at the end of bleaching, and non-totally consumption of peroxide are two problems in high-yield pulp bleaching. In this study, the effect of TAED, at the end phase of bleaching, on process and pulp properties was investigated. Hardwoods chemi-mechanical pulp (CMP) (85% yield), was bleached by mono-stage alkali peroxide process. Treatments comprising three different charges of peroxide (1.5, 2 and 3%) and alkali (sodium hydroxide) (1.12, 1.5 and 2.25) with and without using TAED at the end phase of bleaching i.e. the last 10 minutes. The results indicated that, the pulp brightness and bleaching selectivity increased by chemical charge rising, but with decreasing slope procedure. The chemical charge rising led to an increase in residual peroxide and filtrate COD load. TAED using, through reduction of alkali darkening reaction, caused to improve the brightness and selectivity, and reduce the COD load. Residual peroxide amounts of treatments, which have TAED treatment, were significantly decreased.

Flotation deinking is the prominent technology for ink removal from waste paper. In this study, flotation deinking was carried out applying two levels of sodium hydroxide and five levels of hydrogen peroxide on a mixture of waste papers consisting of: 30, 30 and 40 weight percent OMG, ONP and MOW, respectively. The deinking efficiency was evaluated based on brightness, yellowness and dirt count of hand sheets. The results showed that increasing hydrogen peroxide dosage can increase hand sheets brightness, however, at higher hydrogen peroxide levels, the brightness was reduced probably due to the presence of more NaOH and the limitation of hydro peroxide efficiency for chromophore elimination. Optimal ratio of H2O2/NaOH, significantly increase the efficiency of deinking at lower alkali usage. This research showed that higher deinking efficiency may not be necessarily reached applying more chemicals, but optimal chemicals ratio plays an important role in deinking efficiency.