Deinking Chemicals Research Articles

A comparative study of conventional chemical deinking and environment-friendly bio-deinking of mixed office wastepaper

Bio-deinking is an environmentally friendly process that improves the pulp and paper properties and reduces chemical consumption during the recycling of waste paper. This study was performed to evaluate the efficacy of enzyme by Penicillium sp. AKB-24. Chemical deinking of MOW showed freeness (CSF), pulp brightness (ISO), deinking efficiency, and dirt count by 426±4 ml, 75.55±0.1%, 82.13±0.7%, and 733±24 mm2/m2 respectively at optimum repulping parameters. The physical strength properties including burst index, tear index, tensile index and double fold numbers were found 2.97±0.14 kPa.m2/g, 11.14±0.61 mN.m2/g, 46.60±1.99 N.m/g, and 36±2 respectively during chemical deinking of MOW. The deinking chemicals including NaOH, Na2SiO3, and H2O2 were replaced with crude enzyme by Penicillium sp. AKB-24 during enzymatic deinking of MOW. Enzymatic deinking of MOW resulted in an improvement in pulp freeness by 18.30% compared to chemical deinking while the dirt count value decreased by 32.60% during enzymatic deinking of MOW. Physical strength properties such as burst index, tensile index, and double fold numbers were improved by 16.07%, 14.54% and 8.57% respectively while tear index was decreased by 11.61% during enzymatic deinking of MOW compared to chemical deinking.

A pollution reducing enzymatic deinking approach for recycling of mixed office waste paper.

The efficiency of xylano-pectinolytic enzymes, co-produced by a single microbial strain Bacillus pumilus, was analysed for the recycling of mixed office waste paper through deinking and compared with the alkaline chemical deinking method. Enzymes showed maximum deinking at pH 8.5, pulp consistency of 10%, xylanase-pectinase dose of 12 and 4 IU per gram pulp, respectively, after 120 min of deinking period, and temperature at 50 °C. A chemi-enzymatic approach was employed with xylano-pectinolytic enzymes and various concentrations of deinking chemicals, which showed that enzyme-treated mixed office waste pulp requires only 40% chemicals for deinking, in order to get the almost same level of various handsheets properties, as obtained by the chemical method with 100% chemicals. Similarly, the effluent load of BOD and COD contents was also decreased by 17.90 and 19.75%. This combinational approach of deinking significantly improved the various properties of the handsheets and resulted in gain of 7.5, 9.38, 6.33 and 11.65% in tear factor, burst factor, breaking length and viscosity of the handsheets, while the effective residual ink concentration analysis of deinked handsheets of mixed office waste paper showed deinking efficiency of 22.45%, which revealed the removal of ink particles during enzymatic deinking steps.

Improved de-inking of inkjet-printed paper using environmentally friendly atmospheric pressure low temperature plasma for paper recycling

Nowadays, due to environmental pollution and natural energy consumption caused by waste paper, many researches are being conducted on the reuse of printed-paper. To recycle the paper, de-inking has to be performed. In this article, in order to reduce the use of the commonly used de-inking chemicals, the effect of an atmospheric pressure helium plasma treatment on the de-inking enhancement of printed-paper is studied. Through colorimeter and UV-visible spectrometer measurements the plasma treatment is shown to speed up the de-inking. While SEM observations and FTIR measurements suggest that the paper quality is retained upon plasma treatment, the increase of surface hydrophilicity measured by water contact angle measurements, compared to non-treated paper, is believed to enhance the fiber swelling of the paper and lead to a faster ink removal.

An efficient eco-friendly approach for recycling of newspaper waste.

In this study, a chemical reduction strategy was explored for deinking of newspaper waste using xylano-pectinolytic catalysts. A remarkable reduction of 40% in toxic chemicals consumption was obtained by introducing this enzymatic approach of deinking along with improved level of various physical and optical properties. Similarly, a reduction of 18.89% and 17.68% in BOD, COD values of effluent has also been noticed. This combined deinking methodology also resulted in a gain of 5.82% in breaking length, 6.45% in tear factor, 8.57% in burst factor and 9.64% in viscosity, which greatly improved the quality of the handsheets. The study revealed that enzymatic deinking followed by chemical deinking with 40% less chemicals consumption, could be an effective method for reducing the negative impact over the environment caused by 100% deinking chemicals. This is the first report of newspaper waste deinking using xylano-pectinolytic catalysts produced concurrently in the same production media by a bacterial isolate using agricultural wastes as carbon sources.

Deinking process water flotation: An innovative solution to improve deinking and papermaking processes efficiency

High and uncontrolled surface active substances (SAS) concentrations in deinking line process waters strongly disturb flotation deinking. Indeed, their adsorption at air/water and ink/water interfaces stabilizes air bubbles and ink particles, reducing ink collection during flotation. In addition, foam stabilization promoted by SAS reduces froth drainage and consequently enhances suspended solids losses. All in all, selectivity of flotation is negatively affected by excessive SAS concentrations. Floating process water with adapted technology, a patented solution, is an efficient way to decrease SAS concentration and thereby recover flotation deinking selectivity. This concept was tested at industrial scale with success. First loop clear filtrates of a deinked pulp line (for newsprint production) were floated. At steady state, this treatment allows a 20% reduction of the SAS concentration in first loop process water. Evaluation of ink removal selectivity at pre-flotation and post-flotation showed a significant improvement in comparison with reference values. During the trial, the mill could either produce pulp with lower ink content and consequently higher brightness (50 ppm effective residual ink concentration [ERIC] less, corresponding to a 1 brightness point increase) for similar losses, or similar pulp quality with 1% to 2% yield improvement, representing a huge cost reduction. In addition, beneficial side effects were reported, such as reduced deinking chemicals consumption (soda, silicate, and bleaching agents) and better paper machine runnability, especially in terms of stickies breaks.

Deinking of Digital Prints: Effect of Near-Neutral Deinking Chemistry on Deinkability

This article demonstrates the effect of near-neutral deinking chemicals on the outcome of a deinking process. More specifically, we demonstrate that good deinkability of digital prints, i.e. liquid-electrophotographic (LEP), dry-electrophotographic and inkjet (IJ) prints, at the laboratory scale, can be achieved with effective near-neutral deinking chemistry that is based on readily available commercial chemicals. The deinking results meet or exceed the target levels, such as ink speck contamination (i.e. dirt area), ink elimination, filtrate darkening, color shade and luminosity, as defined by the European Recycling Paper Council’s deinking scorecard. It is noteworthy that the proposed chemistry has a prominent effect on reducing the dirt area of LEP print media and suppressing the filtrate darkening of dye-based IJ print media. Experimental results using the proposed deinking chemistry compare favorably to those obtained with alkaline deinking chemistry.

Interactions between cationic polyelectrolyte and pulp fines

Papermaking pulps are a mixture of fibres, fibre fragments, and small cells (parenchyma or ray cells), usually called pulp fines. The interactions between pulp fines and a cationic copolymer of acrylamide and acryloxyethyltrimethyl ammonium chloride were investigated based on solid-liquid isotherms prepared under different turbulence, and subsequent advanced surface characterization using X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The surface charge and surface area of pulp fine substrates were measured by methylene blue sorption-XPS analysis and nitrogen adsorption combined with mercury porosimetry, respectively. The driving force behind polyelectrolyte adsorption was the amount of the surface anionic charge, whereas surface area appeared to be of less importance. Based on a comparison of solid-liquid and XPS sorption isotherms, different polyelectrolyte conformations were suggested, depending on the types of fines: A flatter conformation and partial cell-wall penetration of polyelectrolytes on kraft fines from freshly prepared pulp, and a more free conformation with extended loops and tails on lignocellulosic fines from recycled pulp. Additionally, ToF-SIMS imaging proved that recycled pulp fines contained residual de-inking chemicals (primarily palmitic acid salts) that possibly hinder the electrostatic interactions with polyelectrolytes.

High-Quality Deinked Pulps via Alkaline-based HPMA Deinking Chemistry

In this paper we present an alkaline-based deinking chemistry (coded HPMA), which facilitates deinking of digital as well as conventional print media. The novel method presented here, HPMA, uses traditional alkaline deinking chemicals including sodium hydroxide and sodium silicate, but with the substitution of a readily-available emulsifier, a non-ionic surfactant, for the traditional fatty acid. The chemistry is based on methodical structural-physical understanding of properties of digital inks applied to deinking chemicals and deinking processes, to achieve high-quality deinked pulps at lab scale. The resultant chemical composition serves effectively as a release agent for the ink from the paper fibers and a collecting agent to agglomerate the particles to achieve ink particulates with the desired size range and provides the desired interfacial interaction with the foam for eventual removal during the flotation. High quality deinked pulps of HP-Indigo ElectroInks, HP Inkjet pigment/dye-based inks and HP dry toners were successfully obtained via HPMA. Similarly good results were obtained for traditional offset inks and mixed office waste with HPMA, suggesting the generic nature of our deinking chemistry.

Heavy Metals in the Products of Deinking Flotation of Digital Offset Prints

This study was undertaken to investigate the suitability of applying the conventional method of chemical deinking flotation of digital offset prints and ecological implications of the disposal of digital offset prints, with special emphasis on the content of heavy metal cations. The EDXRF method was used to determine the concentrations of Pb, Zr, Sr, As, Co, Zn, Cu, Ni, Fe, Mn, Cr, V, Ti, Ca, and K cations in handsheet ashes after flotation as well as in ashes of foams separated from cellulose suspension in the flotation phase. The same method was applied to determine the concentrations of Pb, Cr, Mn, Fe, Ni, Cu, Zn, and Co in process water filtrates obtained from the cellulose suspension after flotation and in foam filtrates. Centrifuging and coagulation previously treated flotation process water, while foam filtrates were centrifuged. Concentrations of Pb, As, Sr, Zr, K, Ca, Ti, V, Cr, Mn, Fe, Cu, and Zn were determined in the sediments obtained by centrifuging process water. The trials were done with unprinted substrates without deinking chemicals, with unprinted substrates in the presence of deinking chemicals and with printed substrates in the presence of deinking chemicals. Cation analysis revealed that deinking chemicals facilitate release of cations from the substrate and their transition into process water. Concentrations of most cations in the flotation process water, in foam water as well as in the sediment of the process water of printed substrate flotation deinking were lower than those obtained by flotation of unprinted substrate suspension. Polymer particles of ElectroInk incompletely separated from cellulose fibers prevent release of cations from cellulose fibers into process water. Deinking chemicals do not affect release of cations from ElectroInk particles, so the substrate is the main source of increased concentration of cations in the water of digital offset print deinking. The major part of cations in process water is bound to the colloid particles of the filler (CaCO3) released by substrate disintegration and to particles of fine fibers.

Surface chemicals concepts of flotation de-inking

This review outlines the important parameters, which influence the flotation de-inking and discusses the surface chemical aspects of the process. Although, it has been established increasing temperature and pH facilitate the release of ink particles from the fibre during pulping (prior to flotation), it has not yet been completely established to what extent these parameters increase or decrease the efficiency of the primary flotation step. In fact, increasing temperature appears to decrease the flotation rate and also an increase in pH can retard the flotation due to a reduction in capture efficiency between the air bubbles and the ink particles decreasing the flotation in the cell. In addition, the size, shape and roughness of the ink particles influence this bubble/particle capture mechanism. Bubble frequency and bubble size is influenced by surface tension (type and concentration of frother) but X-ray studies also indicate that the fibre consistency can influence the bubble shape and flow patterns causing channelling and re-circulation of bubble flow in the cell. Tests with different gases (oxygen and nitrogen instead of air) show no significant gains in optical and mechanical properties of the fibre. Fatty acids with higher chain length and lower degree of saturation are less soluble and ensure lower carry-over but less foaming and also less fibre recovery. The primary mechanisms of fatty acid flotation involves precipitation of calcium soap, followed by micro-encapsulation of ink through a hetero-coagulation mechanism, followed by the bubble/ink particle capture step. In the use of nonionic surfactant, cloud point and HLB are important parameters, which influence brightness, washing and flotation efficiency. Optimum flotation occurs with slight excess of fatty acid to reduce surface tension and optimum calcium levels ensuring that most of the calcium is removed in the process. A lower calcium level gives lower stock loss but a high calcium has a detrimental effect, causing scaling and deposition. A critical nonionic/fatty acid balance is needed to minimize stock loss during the flotation. New chemicals need to be developed to increase selectivity, reduce entrainment and increase the process efficiency. Also, the underlying knowledge linking structural/function relationship for de-inking chemicals in relationship to the heterogenity at the pulps needs to be established. Further progress could help in the treatment of higher fibre content pulps, reducing water and chemical consumption and reducing redeposition of the ink on the fibre.

Deinking of recycled fibers in a flotation flow loop

Conventional laboratory-scale flotation cells, used to study ink removal from pulp slurries, have various shortcomings. In most cells it is difficult to control physical parameters such as the volume of air intake and the bubble size distribution. Moreover, the hydrodynamic conditions in such cells are different from those in industrial flotation cells. To overcome these difficulties we designed a new laboratory flotation cell, consisting of a flow loop and a flotation chamber. The hydrodynamic conditions at the air inlet point closely resemble those of an injection point in an industrial flotation cell and the amount of air can be accurately measured. Moreover, a viewing window allows observation of bubble sizes to be made. Flotation deinking efficiencies can be obtained either by analyzing the ink removed in the froth or by measuring the cleanliness of the pulp. Effects of fluid velocity and deinking chemicals on bubble size distributions and flotation efficiency are presented, as well as effects of air volume fraction.

Office paper de-inking

Significant developments related to the detachment of the toner particles from the fibers in office paper and the removal of detached ink from pulp are resulting in improved de-inking technology. Recent advances in these areas have occurred in de-inking chemicals, enzyme de-inking, agglomeration, magnetic de-inking and fundamental research on de-inking flotation by the use of atomic force microscopy.

The use of surfactants in de-inking paper for paper recycling

Many de-inking surfactants have been claimed in patents. Alcohol ethoxylates and alkylphenol ethoxylates are commonly used in wash de-inking whereas alcohol alkoxylates and fatty acid alkoxylates are commonly used in flotation de-inking and combined flotation/wash de-inking processes. Dispersed ink particle redeposition onto cellulose fibers is a significant problem. Recent developments have occurred in the improvement of de-inking chemicals and in the.understanding of surface chemistry.

Effects of sodium oleate and calcium chloride on the deposition of latex particles on an air/water interface

Sodium oleate and calcium chloride are used as de-inking chemicals in the flotation of ink particles in a slurry of recycled papers. Together they form calcium oleate particles which increase the efficiency of ink removal. To simulate this process we studied how latex particles, with carboxylated charge groups on their surface to model ink surfaces, deposit on an air/water interface in the presence of calcium oleate. The deposition was observed with the impinging jet technique. At the same time, homo- and heteroflocculation studies of latex and calcium oleate were performed. It was found that deposition occurs when latex particles are heteroflocculated with calcium oleate particles, which occurs near the critical coagulation concentration for homocoagulation of calcium oleate. Direct observations of the deposition process indicate that calcium oleate particles act as a bridge between latex particles and the air/water interface. When calcium chloride is added to a latex-dispersion containing oleate, the formation of calcium oleate particles results in a reduction of oleate adsorbed on the latex particles, thus reducing their surface charge.

パンパシフィック諸国における脱墨技術と脱墨薬品

The present state and the future one of the deinking market and technology in Pan Pacific countries are described in this paper.The production of deinked pulp (DIP) will be rapidly increased in near future in Pan Pacific countries.The deinking with a flotating process has been and will be superior.The impact of DIP production increment is different in each country. It is mainly on the environment and resources problems in ripe countries and on the appropriation for the shortage of pulp sources with improving life in advancing countries.The technological difference in flotation, soaking and dispersion are discussed in correlating with the deinking agent (DIA). The higher G/L (gas by liquid) flotaters have been installed in some Japanese mills. Thus displector type DIA with a good ink detachability, a low foaming and a quick foam disapperance have been developped. The soaking process is useful to produce the high quality DIP, because it is benfitable for deinking by chemical reactions with deinking chemicals. The disperser and/or the kneader are usually installed in many mills. This process is useful to peel the undetached inks from cellulose fiber for deinking ONP (old newsprint). Free inks are finer by this operation and become difficult to be removed on the flotater. The divided addition of DIA is useful to this trouble.The dispersing process is used for adjusting the ink particles distribution in deinking waste toner printed paper. DIA with a strong affinity to toner inks has been developped.