Chemimechanical Pulp Research Articles

Evaluating chemi-mechanical pulping processes of agricultural residues: High-yield pulps from wheat straw for fiber-based bioproducts

This work evaluates the feasibility of APMP (alkaline peroxide mechanical pulping) and CTMP (chemi-thermomechanical pulping) of wheat straw as small-scale, low-capital expenditure pulping process to produce high-yield pulps for fiber-based bioproducts. APMP and CTMP wheat straw pulps were characterized in terms of pulping yield, freeness, ISO brightness, and fiber morphology. Additionally, both pulps were evaluated for tissue paper applications and benchmarked against BEK (bleached eucalyptus kraft) market pulp. APMP wheat straw pulps presented higher yield (75.2 – 79.8 %) compared to CTMP (69.1 – 80.6 %), depending on cooking chemicals and chemical charge during the chemical impregnation stage. The final brightness of APMP pulps varied from 36.4 % to 37.8 % ISO when sodium hydroxide and hydrogen peroxide were used as pulping agents without additional chemical additives. However, the brightness of APMP pulps can be increased up to 49.7 % ISO by using additional chemical additives such as EDTA (chelating agent), sodium silicate (peroxide stabilizer), or by employing a multi-stage chemical impregnation strategy. Both pulps produced fibers with similar morphological properties. A comparison of tissue-making properties showed that APMP pulps produced bulkier handsheets with higher water absorption capacity and better softness than CTMP pulps. However, CTMP pulps exhibited a higher tensile index than APMP pulps for a given pulp freeness. The results indicate that non-wood fibers, such as those derived from wheat straw, could be a promising alternative for use in fiber-based bioproducts such as hygiene tissue.

Characterization of Asoka (Saraca Indica L.) branch wood for pulp and paper manufacturing

Asoka (Saraca indica L.) branch wood was evaluated for its chemical composition, morphological features, kraft pulping behavior, and physical properties. The Asoka used in this study contained low amounts of cellulose and hemicellulose, but higher amounts of lignin and ash. It was found that the morphological indices of Asoka branch wood were mostly adequate for pulping and papermaking. The pulping of this wood was performed using chemi-mechanical pulping (CMP), conventional kraft pulping, and soda pulping processes under different conditions, i.e., active alkali and anthraquinone (AQ) addition. The results showed that alkaline pupling and CMP provided low screened yield values. Acceptable kappa numbers and reject levels were obtained at 22% active alkali of soda and kraft-AQ pulpings. CMP pulp showed higher brightness and screened yield than that of alkaline pulps. Alkaline pulpings of Asoka branch wood provided slightly different strength properties of paper sheets than those of CMP pulp. Based on the findings, it can be concluded that Asoka branch wood is more suitable as a raw material for mechanical pulping than it is for alkaline pulping.

Life cycle carbon analysis of packaging products containing nonwood residues: A case study on linerboard and corrugating medium

Circularity is creating momentum toward utilizing waste feedstock in a myriad of applications. The paper industry is not an exception to this trend, and packaging products made from agricultural or agro-industrial residues are receiving more attention now than ever. Additionally, negative consumer perceptions of tree felling are accelerating the acceptance of these fibers. Nevertheless, adopting these residues raises the issue of whether they constitute a better alternative to fight climate change than wood. Answering this question is imperative to ensure that pledges to reduce carbon footprints across the industry are fulfilled. This paper aims to estimate the carbon footprint of corrugating medium and linerboard containing wheat straw and sugarcane bagasse pulp compared to analogous wood-based materials. The goal was also to understand how methodological decisions to allocate emissions to nonwood residues can affect the results. This study includes a life cycle carbon analysis spanning from cradle to grave, which comprises stages for residue production, pulping, paper-making, waste management, and corresponding transportation. For the proposed case study, the results suggest that straw- and bagasse-based medium and linerboard can present a higher carbon footprint than products made from virgin and recycled wood fibers. The main driver is the production of nonwood chemimechanical pulp. In addition, the lower capacity of nonwood residues to be recycled increases the overall impact. Finally, decisions around emissions allocation highly influence the results. This study helps mitigate part of the uncertainty around the environmental sustainability of corrugating medium and linerboard made from the selected nonwood residues.

Effect of chitosan and cationic polyacrylamide on optical and mechanical properties of paper made from chemi-mechanical pulps

The influences of nano-chitosan and cationic polyacrylamide (cPAM) on the optical and mechanical properties of paper made from chemi-mechanical pulp (CMP) were investigated. Bleached chemi-mechanical pulp (CMP) was selected as the control sample. The cPAM was considered at four levels (0%, 0.25%, 0.5%, and 0.75%), while chitosan was added to the CMP suspension at three levels (0%, 1%, and 2%). Paper test specimens were prepared according to TAPPI standards with a basis weight of 60 g/m2, and their optical and mechanical properties were measured. The results indicated that the opacity, greenness, tear strength, burst strength, and Gurley seconds were increased, whereas brightness, water absorption, and a* factor were decreased by increasing the amount of cPAM. Adding chitosan to CMP increased the a* factor, tear strength, breaking length, burst strength, Gurley seconds, water absorption, and greenness in the resulting paper. When polyacrylamide and nano-chitosan were added simultaneously to CMP, the brightness, water absorption, and greenness of the resulting paper decreased, but opacity, burst strength, tear strength, and air resistance had an appropriate increase. In all treatments, the best results were found at 1% chitosan and 0.5% cPAM due to favorable optical and mechanical properties.

Chemi-mechanical pulping with selective fiber separation using 2D correlation near-infrared spectroscopy

Chemi-mechanical pulping with selective fiber separation using 2D correlation near-infrared spectroscopy

Investigation into the characteristics of bagasse processed with 3C-DES and the production of chemimechanical pulp for pulp molded

Pulp molded generated from renewable bagasse as biodegradable packaging materials has been widely viewed as an eco-friendly and cheap way to substitute the current huge consumption of nondegradable plastics, and deep eutectic solvents (DES) pretreatment are a promising approach to obtain high-yield pulp efficiently and sustainably. However, mainstream binary-component DES still suffers issues of high viscosity and corrosiveness. This study put forward a ternary-component DES (3C-DES) with the addition of ethylene glycol (EG) into choline chloride (ChCl) and P-toluenesulfonic acid (PTSA) and examined pretreatment performance and optimal DES ratio for thread rolling bagasse via compositional analysis and physicochemical characterization. Moreover, density functional theory calculations were used to reveal structures and weak interactions of different ratios of 3C-DES, and a novel 3C-DES pretreatment chemical-mechanical pulp and pulp molded were finally prepared. The results indicate that the 3C-DES with ChCl:PTSA:EG molar ratio of 1:1:3 is most effective, evidenced by more than 97.94% lignin removals. The 3C-DES pretreated mechanical pulp exhibits superior fiber properties, whereas the hot-pressed pulp molded shows excellent physical properties and thermal stability. Thus, the proposed 3C-DES has great potential to obtain high-yield high-performance pulp molded with low cost and environmental sustainability.

Disposable bamboo fiber meal boxes characterized by efficient preparation, excellent performance, and the potential for beneficial degradation

Disposable plastic meal boxes account for a significant proportion of global plastic pollution, which has caused an increasingly urgent need for substitution with biodegradable plant fiber-molded meal boxes. Compared to other chemical-mechanical pulp pre-treatment methods, steam explosion is a more efficient and clean approach for the preparation of molded meal boxes. In this study, disposable bamboo fiber meal boxes made from steam-exploded pulp (SEP) were prepared using steam explosion. The results showed that the meal boxes prepared using this method had a compact interweaving structure, good tensile performance (with a tensile modulus 1.9 times higher than that of meal boxes prepared using chemical-mechanical pulp (CMP)), excellent water resistance (with a permeability 0.58 times lower than that of CMP), high compression strength, and excellent toughness. After being discarded, SEP was found to have no adverse effects on the soil pH or electrical conductivity (EC) during the degradation process. Furthermore, it could increase the levels of major nutrients for plant growth, such as N and P, improve the C/N ratio, enhance microbial activity, and improve soil fertility. Moreover, the CO2 release rate during the entire degradation process was found to be low. Thus, the bamboo fiber meal boxes developed in this study can alleviate the environmental pressure caused by the greenhouse effect, thereby achieving a green life cycle of highly efficient preparation, stable use, and beneficial degradation.

The effect of hemicellulose pre-extraction on the wood viscoelasticity and its implications on the fiber separation mechanism in Chemi-mechanical pulping

Chemi-mechanical pulping (CMP) is a typical high-yield pulping technology to produce various papers and paperboards due to its high yield and high fiber properties. However, it is challenging to further improve its energy efficiency without the scarification of fiber quality. To attack this challenge, herein we study the effects of different hemicellulose pre-extraction on the viscoelasticity of wood cell wall, the energy efficiency, and product properties in chemi-mechanical pulping (CMP) process. Hardwood was first pretreated by NaOH to hydrolyze the benzyl ester bonds that link lignin with hemicellulose, aiming to partially remove hemicellulose and weaken the inter-fiber connections. Then, the hemicellulose-extracted wood underwent refining. The chemical distributions of wood, fiber morphologies, fiber surface fibrillation, energy consumption, and paper properties were extensively studied. The results showed that a 40.8% removal of hemicellulose corresponded to a 90.3% reduction in wood storage modulus (E’) and a 68.3% decrease in specific refining energy consumption. Moreover, the weaker connections between microfibrils in the secondary layer, caused by hemicellulose extraction, promoted fiber surface fibrillation during pulp refining. The study elucidates the nonnegligible role of hemicellulose as the linking “bridge” between lignin and cellulose. It also provides a new mechanism in addition to the current classic pulping mechanism including lignin chemical/thermal softening and cellulose swelling in both CMP and chemi-thermomechanical pulp (CTMP). This study offers a feasible and efficient approach to extract hemicellulose from hardwood to reduce the refining energy without scarification of fiber quality, therefore, it holds promise for advanced and greener biorefineries.

A compound enzyme with synergistic interaction to treat cotton stalk chemi-mechanical pulp to improve the properties of wastepaper pulp

A compound enzyme with synergistic interaction to treat cotton stalk chemi-mechanical pulp to improve the properties of wastepaper pulp

Treatment of Eucalyptus chemical-mechanical pulp wastewater by coupling system of advanced catalytic oxidation and biodegradation: Synergistic effect of ozonation photocatalytic-microbial

In addressing the issues concerning the challenging treatment, extensive discharge, substantial organic pollution load, and the intricate composition of chemical-mechanical pulp (CMP) wastewater in the pulp and paper industry, an innovative coupled advanced oxidation and biodegradation techniques known as the intimate coupling of ozone oxidation and photocatalysis-biological treatment (ICOPB) was developed for CMP wastewater remediation. The focus of the present research was to explore the optimization of this system, to comprehend the degradation mechanisms, and to understand microbial reaction behavior. Moreover, the study evaluated the degradation efficiency of four potential mechanisms inherent to ICOPB, which include adsorption, photocatalysis, biological treatment, and coupled photocatalytic-biological indirect wastewater treatment. Under the optimal conditions, wherein the O3 concentration was maintained at 35 mg/min, the carrier filling rate was kept at 5 %, pH was held at 7, and aeration was kept at 0.6 L/min, the degradation efficiencies for COD, BOD, and TOC reached 80.7 %, 91.6 %, and 84.6 %, respectively. When compared with the ICOP (intimate coupling of ozone oxidation and photocatalysis) procedure, the ICOPB demonstrates a superior removal efficiency and more comprehensive mineralization. Microbial diversity results indicated that Proteobacteria actively contribute to the subsequent biodegradation of CMP wastewater treated with the ICOPB system. As revealed by the GC–MS analysis and toxicity assessments of intermediate products, ICOPB notably amplified the rate of organic matter degradation and concurrently reduced the toxicity of the effluents. In conclusion, the findings of this research offer an innovative method for the effective degradation of CMP wastewater, thereby addressing a significant environmental concern in the pulp and paper industry.

Analysis of causes for high hydration and low drainage rate of wheat straw chemi-thermo-mechanical pulp

The wheat straw chemi-mechanical pulp has the characteristics of high yield, good mechanical performance and low production cost. However, there are significant problems in the papermaking process by such as high pulp hydration, poor drainage, and large energy consumption during the paper drying-process. It was found that during the chemical mechanical pulping of wheat straw, due to the residual alkali and temperature, the hemicellulose in the pulp was continuously dissolved, some of it entered the water phase, and some of it migrated to the fiber surface. Which reflected in the raise in cation demand for anionic substances in the aqueous phase, the increase in carboxyl content on the surface of pulp fibers, and the aggravation in hydration degree. Further research found that the high valence metal ions can combine the carboxylate radical on the hemicellulose molecule in the aqueous phase with the carboxylate radical on the pulp surface to form a covalent bond, so that the hemicellulose entering the aqueous phase can be re-adsorbed to the fiber surface, thus further increasing the degree of pulp hydration. Carboxymethyl starch was used to simulate hemicellulose, and the hemicellulose re-adsorption phenomenon verification experiments were reproduced in a calcium ion environment. The above findings indicate that during the production of wheat straw chemi-mechanical pulp process, the hemicellulose dissolved and re-adsorption not only leads to the increase of pulp hydration, but also results in poor water filtration during paper formation. Therefore, this study can provide a theoretical basis for optimizing the production process of chemi-mechanical pulp of wheat straw and controlling the technology and method of pulp hydration.

Coupling laccase/PHB and Ca2+ treatment enable high-strength straw chemi-mechanical pulp

Non-wood fibers (e.g., straw) show a large volume in China, which effectively offsets the shortage issue of the forest resource, especially as raw material in the pulping and papermaking industry. The chemi-mechanical pulp (CMP) from the straw is significantly developed due to the advantages of high pulp yield, mechanical strength, and low cost. While the large-amount lignin exposed the pulp fiber surface of straw CMP negatively affects the bonding between its fibers, thus restricting the further improvement of its physical properties. Herein, we developed an environmentally friendly strategy of coupling the laccase/PHB and Ca2+ treatments to modify the chemical and structural properties of fibers toward the high-strength straw CMP. The laccase/PHB treatment removes the lignin of the straw CMP with a Kappa number decrease from 108.28 of the original sample to 75.65 with an 8 u/g dosage of laccase at a 3% PHB system. The removal of lignin with a stiff property also modifies the fiber morphologies of straw CMP, including increasing the measured fiber curl index from 8.0% to 8.5%, and the kink angle from 129° to 137°. Simultaneously, the introduced Ca2+ triggers the strong bonding with the anionic groups of straw CMP fibers, which creates enough, multiple bonds in this fiber system. The coupling laccase/PHB and Ca2+ treatments boost the mechanical strength of the straw CMP, more specifically, the tearing index, tensile index, and bursting index increase from 3.51 mN•m2/g, 20.01 N•m/g, and 1.57 KPa•m2/g of original pulp to 4.56 mN•m2/g, 29.80 N•m/g, and 2.26 KPa•m2/g, respectively. This integrated strategy of laccase/PHB and Ca2+ treatment provides a valuable guideline for improving the strength performance of plant fibers, beyond the straw CMP.

Enhanced production of sugars and UV-shielded lignin/PAN fiber mats from chemi-mechanical pulps

This study investigated poplar pretreatments by chemi-mechanical pulping (CMP) under different beating degrees and alkali concentrations. The enzyme-mediated hydrolysis of pretreated poplar was enhanced by deacetylation and delignification. Meanwhile, the remaining lignin residues were used to produce lignin/polyacrylonitrile (PAN) fiber mats by electrospinning. These mats exhibited excellent mechanical and UV-blocking performance when the lignin was obtained from pulps under milder alkali concentrations (5 g/L). 31P nuclear magnetic resonance (31P NMR) and two-dimensional heteronuclear single-quantum correlation nuclear magnetic resonance (2D HSQC NMR) data revealed that increasing the beating degree at low alkali concentration during the CMP process led to the cleavage of β-O-4′ interunit linkages and re-condensation in lignin, releasing several phenolic groups. Lignin with more linear β-O-4′ interunit linkages and lesser phenolic groups, obtained from treatment of CMP with lower alkali concentration (5 g/L) and beating degree (20°SR), resulted in the corresponding lignin/PAN fiber mats exhibiting better mechanical performance. Further, lignin, along with the increased phenolic-OH and COOH, and p-hydroxybenzoate (PB) units with a more extended conjugate structure, derived from CMP under lower alkali concentration (5 g/L) and higher beating degree (45°SR), led to a stronger ultraviolet (UV) absorption in the corresponding lignin/PAN mats. To summarize, this study reports a mild and low-pollution biomass pretreatment method (CMP) that can efficiently regulate the lignin structure and exhibit efficient anti-ultraviolet properties. The corresponding UV-blocking fiber mats can be potentially used as materials for wearable fabrics.

On-Site X-ray Fluorescence Spectrometry Measurement Strategy for Assessing the Sulfonation to Improve Chemimechanical Pulping Processes.

Minimizing the fiber property distribution would have the potential to improve the pulp properties and the process efficiency of chemimechanical pulp. To achieve this, it is essential to improve the level of knowledge of how evenly distributed the sulfonate concentration is between the individual chemimechanical pulp fibers. Due to the variation in quality between pulpwood and sawmill chips, as well as the on-chip screening method, it is difficult to develop an impregnation system that ensures the even distribution of sodium sulfite (Na2SO3) impregnation liquid. It is, therefore, crucial to measure the distribution of sulfonate groups within wood chips and fibers on a microscale. Typically, the degree of unevenness, i.e., the amount of fiber sulfonation and softening prior to defibration, is unknown on a microlevel due to excessively robust or complex processing methods. The degree of sulfonation at the fiber level can be determined by measuring the distribution of elemental sulfur and counterions of sulfonate groups, such as sodium or calcium. A miniaturized energy-dispersive X-ray fluorescence (ED-XRF) method has been developed to address this issue, enabling the analysis of sulfur distributions. It is effective enough to be applied to industrial laboratories for further development, i.e., improved image resolution and measurement time.

Characterization of MDF produced with bolaina (Guazuma crinita Mart.) wood residues from plantation

Bolaina (Guazuma crinita Mart.) is one of the most widely used plant species in the forest plantations in Ucayali, Peru. The production of bolaina wood has increased, consequently the generation of wood residues has also risen. Fortunately, this waste can be used as raw material to manufacture other products. This study aims to produce test boards that can achieve at least, the minimal requirements of European and American standard for medium-density fiberboards (MDF) produced using two types of pulps, namely refiner mechanical pulp (RMP) and chemi-mechanical pulp (CMP), from bolaina wood residue obtained from a 5 to 8-year-old forest plantation and using two types of resins: urea-formaldehyde (UF) and emulsion polymer isocyanate (EPI). To manufacture RMP and CMP, wood residues were pretreated through water and 5% sodium hydroxide (w/w) soaking respectively for 24 h. The fiber morphological parameters of both pulps were analyzed using the Morfi compact equipment. Additionally, woods and pulps were also chemically characterized. The solid contents of the resins were 65% for UF and 23% for EPI diluted with distilled water. Both resins were applied with a dose of 10% (w/w). Four types of MDF were prepared: RMP-UF, CMP-UF, RMP-EPI, and CMP-EPI. The results confirmed the feasibility of preparing MDF with wood residues (5% bark) of bolaina as the raw material. In terms of the contributions of resins, MDF with EPI exhibited better physical and mechanical properties than that manufactured with the UF. The pulps, RMP and CMP, had similar performance in MDF. The RMP-EPI and CMP-EPI boards exhibited the best properties.

Developing an Efficient Processing System Treatment for the High Concentration of Eucalyptus Chemical Mechanical Pulp Wastewater.

The current wastewater treatment method shows low efficiency in treating wastewater with high concentrations of chemical mechanical pulp (CMP). Therefore, a chlorine dioxide Pretreatment Anaerobic Treatment (DPAT) was developed and applied to treat the CMP wastewater to obtain higher efficiency, obtaining the following results: The biodegradability of CMP wastewater improved after chlorine dioxide pretreatment. The COD of wastewater treated with chlorine dioxide was reduced from 5634 mg/L to 660 mg/L. The removal rate for chemical oxygen demand (COD) was 88.29%, 29.13% higher than the common anaerobic treatment. The reasons for the high efficiency of the DPAT treatment were that chlorine dioxide pretreatment removed the toxic substances in the original wastewater and thereby promoted the proliferation and growth of the anaerobe. The results show that pretreatment with chlorine dioxide can effectively enhance the biodegradability of high-concentration CMP wastewater. Therefore, DPAT treatment of high-concentration CMP wastewater is beneficial to environmental protection.

Evaluation of the effects of transition metal ions on the optical aging and whiteness of chemimechanical pulp

The negative effects of metal ions were addressed relative to the whiteness characteristic of chemomechanical pulp samples prepared. Proper solutions were considered to mitigate this adverse effect. The chemomechanical pulp samples were supplied in an unbleached form. The samples were wetted using ethylene diamine tetra acetic acid (EDTA) chelating agent, and then each of the samples was wetted with EDTA after drying with solutions containing the transitional metal ions. The results showed that the greatest whiteness reduction resulted from Fe2+ ions, whereas the smallest effect resulted from Al3+ ions. Wetting of the samples in various concentrations of the chelating agent (EDTA) had an optimum value in improving the whiteness characteristic of the paper. Thereafter, no change was created in whiteness improvement and brightness stability by increasing the concentration of EDTA. Increasing the aging time reduced the whiteness characteristic of the chemomechanical pulp.

Comparison of the internal functionalization and surface modification methods of chemi-mechanical pulp handsheets using nanocellulose, chitosan, and DTPA

The optical and mechanical properties of paper sheets were compared following treatment with biopolymers using two different methods, i.e., internal functionalization and surface modification. Industrial chemi-mechanical pulp was provided, and two groups of paper handsheets were made. The first group of paper sheet samples were prepared with incorporated chitosan in a mixed-in-pulp slurry (at three treatment levels, i.e., 0%, 1%, and 2%), and in the second group, untreated handsheets were spray-coated with either 2% chitosan, 2% nanocellulose, 0.5% DTPA, or a mixed solution (0.5% DTPA + 2% chitosan + 2% nanocellulose). Then, the optical and mechanical properties of the prepared paper sheets were analyzed. The brightness, opacity, and greenness/redness of the samples were measured spectrophotometrically using the CIELab system. Additional properties of the paper, i.e., the water absorption, air permeability, and tear, tensile, and burst resistance, of the treated samples were also measured. The results indicated that the treatments had a considerable effect on the relative mechanical and optical parameters, which resulted in an increase in the mechanical properties, especially when the nano-particles were applied to the mixed-in-slurry process. Inversely, results from the spray-coating method indicated better results for the optical specifications.

Characteristics of calcium lignin from pulping waste liquor and application for the treatment middle-stage wastewater of paper making

ABSTRACT In order to obtain a lignin-based adsorbent with low cost, simple operation and no further modification, a calcium lignin adsorbent was prepared from chemical mechanical pulping (CMP) waste liquor by directly calcification from lime. The calcium lignin was characterized by BET, SEM, TEM, FT-IR and solid-state NMR analyses. The results showed that the molecular structure of the calcium lignin particles did not change when compared to sodium lignin, the formation mechanism of calcium lignin was revealed. The initial COD and lignin contents of CMP waste liquid were 54858 mg/L and 24.39 g/L, the conversion rate of lignin can reach 71.36% when was deal with lime. Thus, most of the lignin resources in the waste liquid were recovered. The middle-stage wastewater (MSWW) of pulping and papermaking was dealt with calcium lignin, the COD removal rate was up to 85.83%. The adsorption isotherms and kinetics were well fitted by the Langmuir model and pseudo-second-order kinetic model, respectively. Lime was regenerated from the used calcium lignin with high-temperature calcination, the conversion rate of calcium ions can reach 83.56%. Overall, the calcium lignin prepared by the one-step method exhibited great potential for effectively removing COD from middle-stage wastewater.

Thermal yellowing of hornbeam chemi-mechanical pulps bleached with hydrogen peroxide and sodium dithionite

The thermal yellowing of hornbeam chemi-mechanical pulps (CMP) after bleaching with ‎hydrogen peroxide and sodium dithionite was investigated. The hornbeam chips were randomly chosen ‎from Mazandaran wood and paper industries. The CMP pulps prepared with 85% yield were separately ‎bleached with diethylenetriamine pentaacetic acid (DTPA), without DTPA, and hydrogen ‎peroxide. Some pulps were bleached with sodium ‎dithionite. The optical ‎properties of prepared hand-sheets of 60 g/m2 after spraying with 0.5% DTPA were measured using TAPPI standard methods. All prepared papers were thermally aged ‎separately in an oven at 105 °C for 0, 10, 20, 30, and 40 h. The optical properties, such as brightness, ‎yellowness, coefficient of absorption, k/s ratio, post ‎color (PC) number, and a* factor, before and after ‎thermal aging were measured. The results showed that from 0 to 40 h, the optical properties ‎of paper increased except brightness and ‎greenness. ‎This increase was more extensive up to 15 h. Additionally, among the various treatments, DTPA treatment in long-term thermal aging and the use of ‎sodium ‎dithionite and hydrogen peroxide in the short-term aging had noticeable effects on brightness ‎‎durability and decrease in the color reversion. Thus, there was an increase in the durability of the paper ‎against thermal deterioration.