Flotation Deinking Process Research Articles

Deinking of Black Toner Ink from Laser Printed Paper by Using Anionic Surfactant

The objective of this research was to synthesize natural anionic surfactant from renewable material and use of this surfactant for ink removal from printed paper via flotation deinking in paper recycling process. The work included the preparation of the castor seed raw material, extraction of castor oil, preparation of anionic surfactant and deinking flotation of waste printed paper. Foamability and foam stability, critical micelle concentration and hydrophilic lipophilic balance of the surfactant was characterized and used to evaluate its fundamental deinking ability properties for the purpose of deinking flotation. The hydrophilic-lipophilic balance (HLB) of the fatty acid soap of 19.48, average Foamability height of 49cm and critical micelle concentration (CMC) of 0.0065M was obtained. Lab scale flotation deinking process was done and the basic flotation parameters like flotation time, fatty acid soap dosage and pH were optimized for evaluating deinking efficiency. The flotation deinking efficiency was probed by measuring the residual ink concentration of the hand sheet via Perkin Elmer spectroscopy before and after deinking flotation. The individual and interaction effects between the basic parameters were studied by using design Expert Software 6.0.8. For the deinking flotation, the maximum ink removal efficiency was determined to be 78.02% at the flotation time of 90min, fatty acid soap dosage of 1.5% and pH of 9. Increasing flotation time from 30min up to 90 min and decreasing fatty acid dosage from 3% to 1.5% and increasing of pH from 3 up to 9 were found to have increased the ink removal efficiency.

Modeling and prediction of flotation performance using support vector regression

Continuous efforts have been made in recent year to improve the process of paper recycling, as it is of critical importance for saving the wood, water and energy resources. Flotation deinking is considered to be one of the key methods for separation of ink particles from the cellulose fibres. Attempts to model the flotation deinking process have often resulted in complex models that are difficult to implement and use. In this paper a model for prediction of flotation performance based on Support Vector Regression (SVR), is presented. Representative data samples were created in laboratory, under a variety of practical control variables for the flotation deinking process, including different reagents, pH values and flotation residence time. Predictive model was created that was trained on these data samples, and the flotation performance was assessed showing that Support Vector Regression is a promising method even when dataset used for training the model is limited.

Improving Adsorption Deinking by Identifying the Optimum Balance between Polymer Beads and Deinking Chemistry

Ink removal from recovered paper is a very important process in paper and board recycling. The current deinking processes have made obvious contributions to the use of raw materials for the paper and board industries. In contrast to the flotation deinking process, in which small air bubbles are used to remove ink from the pulp, the novel and more energy-efficient method of adsorption deinking technique depends on the attachment and adsorption of ink particles on small polymer beads. The energy savings of adsorption deinking results from the fact that the process is efficient at greater stock consistencies, thus providing water conservation and savings. The present study was carried out to improve the adsorption deinking method by identifying the optimum balance between the deinking chemistry and the polymer beads. Different types of deinking solutions and polymer beads were used for this study with newsprints and mixture of newsprints and magazines. It was found that EGA 3000 solution and polyethylene terephthalate beads worked well with newspaper pulp.

Deinking of inkjet digital nonimpact printing

Pigmented nonimpact (inkjet) printing is a concern in conventional flotation deinking, due to the problems associated with the hydrophilic, submicron-size pigment particles of the ink. Preliminary experiments were conducted to evaluate the efficiency of a conventional flotation deinking process in detaching those inkjet particles from the fiber surfaces and network. A Denver D-12 laboratory flotation cell was used to test 100% old newsprint paper (ONP) with the ISO brightness target set to 58, which makes a paper recyclable. The inkjet-printed ONP was floated to 47 ISO brightness by the INGEDE Method 11. It was enhanced to 50 ISO brightness using flotation, with the addition of nonionic surfactant for better repulping. In addition, a patented electric field technology was used for further improving the floated ISO brightness to 52.5—yet still short of the 58 target for recycling. This improvement was reached with small air bubble sizes, which are more likely to collide and interact with ink particles, causing additional ink to be brought up to the surface of the water pool. The increasing problem of deinkability from digital nonimpact inkjet printing means that additional technical efforts are needed to overcome the crossroad between environmental concerns and technological progress. Papermills, inkjet suppliers, printer manufacturers, and academic and industrial deinkers should take collective action to meet the challenges to future success.

Flotation Deinking of Xerographic and Laser-Printed Paper: Influence of Surface-Active Substances

In present time, recycled paper from xerographic and laser-printed wastepaper plays an important role as alternatives to paper from virgin pulp because of their good pulp quality and high amount of wastepaper each year. This type of paper is classified as Mixed Office Wastepaper (MOW). The xerographic and laser-printed inks are usually called “toner” which its formulation is different from conventional ink. This work aimed to investigate paper recycling by flotation deinking process. The flotation experiments were conducted using SDS (sodium dodecyl sulfate) and Triton X-100 (C14H22O(C2H4O)n). The experimental results demonstrated that ink removal was more efficient with the use of non-ionic surfactant (Triton X-100) than anionic surfactant (SDS). The efficiency of ink removal was determined by ERIC and the pulp’s brightness. In addition, the quality of de-inked pulps was evaluated by pulp physical properties such as burst strength, tear strength and tensile strength.

Understanding the Role of Surface Active Substances in Flotation Deinking Mills by Coupling Surfactant and Ink Balance With Process Simulation

Surfactants are largely present in papermaking/recycling processes. They are added intentionally or come with raw materials or process/functional additives. Once they have reached the process, they build-up in the circuits and, depending on their surface activity and concentration, they can have adverse effects on deinking and on the whole papermaking process, such as excessive frothing, depression of ink floatability, and paper sizing/retention difficulties. In this paper, the removal of apparent surface active chemicals (ASAASAASAC) is first evaluated in different flotation deinking mills through mass balances using surface tension measurements and a specific methodology. Mill data show that, in two-stage deinking lines, ASAASAASAC are slightly concentrated in the second stage, contributing to an increase in pulp frothing behavior, in flotation loss, and in some cases to a low ink removal efficiency. Trends observed in deinking mills are then interpreted using experimental data obtained at the laboratory scale in the presence of a model surfactant, and by process simulation. The effect of ASAASAASAC concentration on the efficiency of the flotation deinking process is explained in terms of their effect on particle and water transport sub processes, namely, flotation, entrainment, frothing, and drainage.

Review of Patented Electric Field Technology with Application to Non-Impact Printing

Office waste papers with non-impact printing are difficult to deink. It contains dye, pigment, binders dispersed in solvent which was not responding to conventional flotation cell treatment very well. To focus on green and sustainability of printing industry, deinking of recycled paper containing these inks by using patented technology in a flotation cell with anode and cathode is described. The deinking of non-impact printed inks vs. traditional printed inks is reviewed. The deinking efficiency of non-impact printed inks can be improved substantially by introducing an electric field to the conventional flotation process. The electric field exerts a force on the charged ink particles and it also generates fine bubbles due to the electrolysis of water. Electric field could improve the efficiency of convention flotation deinking process in detaching ink from fiber surface and network. This is because physiochemical and hydrodynamic forces do not provide enough detachment force in the flotation process. Using a combined electrolytic and flotation cell has the advantage of removing the ink from both surface and network based on charge difference between ink and fiber.

A Simple Flotation De-Inking Experiment for the Recycling of Paper

Flotation de-inking technology is used in the paper recycling process to preferentially remove hydrophobic contaminants, such as inks and toners from a slurry of fibers in water. In the process fine air bubbles are introduced into the suspension and the hydrophobic contaminants, preferentially attached to the bubble–water interface, are carried to the top of the flotation vessel and are skimmed away in a reject stream. Clean fibers are taken from another port of the vessel as the accept stream. This short article describes a simple, inexpensive method to execute in the laboratory a batch type flotation de-inking process on wastepaper. In the experiment, wastepaper is dispersed in water and then de-inked using a laboratory flotation apparatus readily assembled from common lab equipment. The product streams are collected on filter paper to determine the contaminant removal efficiency and the fiber yield. The experiment is useful for middle or high school science courses or introductory-level college environ...

Surface rheology and foaming properties of sodium oleate and C 12(EO) 6 aqueous solutions

The dynamic surface tension (DST) and the surface viscoelastic modulus of sodium oleate aqueous solutions at different concentrations were measured using an image analysis tensiometer based on the oscillating bubble technique. The diffusion coefficient of oleate moieties was calculated from DST measurements and the surface viscoelastic modulus using the Langmuir–Szyszkowski and the diffusion-controlled adsorption models. The viscoelastic moduli obtained from model calculations were compared with the corresponding experimental values. The diffusion coefficient of C 12(EO) 6 in water and the parameters of the Langmuir–Szyszkowski adsorption isotherm were taken from the literature and used to calculate the surface viscoelastic modulus of its aqueous solutions at different concentrations. The foaming properties of both C 12(EO) 6 and sodium oleate solutions, viz., the foam conductance and the water volume fraction in the foam, were measured using a commercial Foamscan device. Foaming experiments with C 12(EO) 6 and sodium oleate solutions were carried out either under static conditions; i.e., the foam conductance and the water volume fraction were measured as a function of time after the generation of a fixed volume of foam, or under dynamic conditions; i.e., the foam conductance and the water volume fraction were measured during foam formation. The variations in the foam permeability as a function of surfactant concentration were related to the viscoelastic properties of the air/water interface and to the presence of micelles in the foam films. With foams in which the water volume fraction was higher than 0.05, the foam electrical conduction could be described using a simple parallel resistor model and their conductance measurements were related to the foam water volume fraction. The results related to water drainage under static conditions were used to interpret water drainage under dynamic conditions. Preliminary conjectures on the influence of foam permeability and water volume fraction on the yield of the flotation deinking process were drawn from these results.

Ultrasonic treatment to improve the quality of recycled pulp fiber

The effect of ultrasound on the quality of recycled fibers was investigated. Ultrasound was applied to recycled pulp fiber suspension before ink removal by conventional flotation. The ultrasonic treatment induced an increase in the sedimentation volume of the fiber, which implies that the flexibility and bulkiness of the fiber increase. The water retention value of the ultrasonically treated fiber recovered from the loss caused by the recycling. These facts are due to a beating effect of the treatment. The paper sheets prepared from the ultrasonically treated fiber suspension showed higher sheet density, tensile strength, and brightness than that from an untreated fiber suspension. The process, which consists of ultrasonic treatment for 1 min following flotation deinking, requires about 1.4 times as much energy as the conventional flotation deinking process, but it induced 20% improvement in brightness. The results indicate that the ultrasonic treatment is effective in improving recycled fiber quality.

Mathematical modelling of the flotation deinking process

The overall flotation deinking process can be divided into four basic microprocesses: 1. (1) collision or capture of an (ink) particle by an air bubble 2. (2) adhesion of an (ink) particle to the air bubble by sliding 3. (3) development of a three-phase contact at the air bubble/water/particle interface, and 4. (4) bubble/particle stability or instability after an aggregate is formed each of these microprocesses have an associated probability that they will occur successfully in a flotation cell. In this paper, the associated probabilities of each microprocess are employed in the development of a kinetic- or population balance-type model of the overall flotation process. The overall model contains two kinetic constants: the first, k 1 governs the overall probability of a free ink particle successfully intercepting and adhering to an air bubble; the second, k 2 is a measure of the probability that a bubble/particle aggregate pair will become unstable and split to yield a “new” free ink particle. The solution to the kinetic model is presented in terms of k 1 and k 2, which are themselves functions of system parameters such as bubble and particle physical properties (e.g., diameter, density), fluid properties (e.g., viscosity, surface tension), etc. From this solution, a definition of a theoretical flotation efficiency, as well as other system performance parameters are presented.

古紙パルプ 脱墨剤の最近の動向について

The deinking of old news paper (ONP) has been practiced for several decades and recognized to be important in the meaning of environmental protection. Deinking technology has been progressing chemically and/or mechanically in production of high quality paper.The deinking agents are the chemical species which are classified in surface active agent and have an important role during flotation deinking process such as penetrability, ink coagulation ability, foaming ability, and so on. By changing the molecular configuration of the deinking agents, we succeeded in developing a new deinking agent that has a higher penetrability. The higher the penetrability of the deinking agent, the lower the amount of nondetached ink. It is particularly effective against offset printing paper which is favored in the newsprint market in Japan. Furthermore, we could detect a direct evidence of interaction between ink and the new deinking agent by using quartz-crystal microbalance and photoacoustic spectroscopy. The new deinking agent is now in use at some deinking mills in Japan.On the other hand, it is well known that flotation method is poor in removing fine ink particles, approximately under 10 μm. In spite of these particles strongly related to the products quality, they have little affinity for air bubble and making conventional flotation operations ineffective for ink removal. In order to remove the fine ink particles efficiently, it should be coagulated during the flotation process. Considering the problems associated with fine ink particles, we have developed a new type of deinking agent. In this report we also propose a new approach for ink coagulation method by flotation deinking.

Adsorption characteristics of surfactants on secondary wood fiber surface

Surfactant residues in recycled wood fiber from the deinking process can have impact on the subsequent bleaching and papermaking processes by increasing bleaching agents and disturbing papermaking wet-end chemistry. In this paper, the fundamental mechanism of surfactants adsorption characteristics on secondary fiber surface was studied. The adsorption isotherms and kinetics of an anionic surfactant, sodium dodecyl benzene sulfonate (SDBS) and a non-ionic surfactant, Triton X-100 (TX-100) on secondary fiber surface with or without the presence of electrolytes (Mg2+ ions) were studied by using spectrophotometric methods. Results showed that the adsorption isotherm of SDBS could be subdivided into four regions, and the adsorption of SDBS was increased with the presence of Mg2+ ions. While for TX-100, the adsorption isotherm showed typically Langmuir-type adsorption, and its adsorption was decreased with the presence of Mg2+ ions. Kinetic analysis indicated that the adsorption processes both fit pseudo-second-order model well. The adsorption rate of both surfactants was affected by the initial surfactant concentration, electrolyte and temperature. The activation parameters confirmed that the adsorption processes of both surfactants were typically diffusion-controlled and endothermic at a temperature range commonly used for current flotation deinking processes. SDBS and TX-100 mainly adsorbed to the hydrophobic sites of secondary fibers surface, which decreased the fiber hydrophobicity and reduced the fiber loss in the flotation deinking process. The results suggested that the concentration of Mg2+ ions should be maintained at a low level when SDBS was used in the flotation process.

A study on the ink-fiber interfacial interaction in waste printed paper I. The effect of a custom-designed polymeric additive on flotation de-inking of solvent-treated wastepapers

The effect of interaction between solvent and three different kinds of printed wastepaper has been studied. The solubility parameter of the solvent was found to be among the most important in order to obtain an optimum ink-fiber interfacial swelling, necessary for de-inking wastepaper. The degree of ink-fiber interfacial swelling was qualitatively estimated by examining the dispersity of ink particles using an optical microscope. FT-IR analyses were carried out to correlate the degree of dispersion and the ink composition in the printed wastepapers studied. The effect of a selective swelling solvent on the de-inking characteristics of a mixture of old wastepapers was investigated. The solvent treatment of these wastepapers prior to flotation de-inking failed to add any positive effect on the brightness of the de-inked pulp. On the other hand, the incorporation of a custom-designed polymer additive improved the pulp brightness without any solvent treatment. The same additive played a negative role in the presence of a swelling solvent. The function of the polymer additive in the flotation de-inking process is also described.