Hamburg, Univ., Diss., 2003. / Computerdatei im Fernzugriff.

Hamburg, Univ., Diss., 2003. / Computerdatei im Fernzugriff.

Hamburg, Universiẗat, Diss., 2003.

No description available.

Separation of hydrophilic inks such as pigmented inkjet and flexographic inks has been an issue in paper recycling since the beginning of their use. The use of inkjet printing is continuing to increase, and it does not appear that this increase will stop anytime soon. Because of this, it is essential to find an adequate method of deinking these inks for the recycling of paper products. There has been a significant amount of research on methods of improving deinking of these inks, but none have been effective up to this point. Additionally, there has been a significant amount of research studying the effects of deinking parameters on these inks, but there are still gaps in this knowledge. A thorough investigation of deinking chemicals and parameters was conducted in this research along with an investigation of the behavior of the hydrophilic inks during the paper recycling, such as the detachment and reattachment of the ink. Through this analysis, two novel deinking methods were developed to decrease the redeposition and improve the separation of these inks. These methods were adsorption deinking and Liquid Phase Plasma (LPP) treatment. Both of these methods were shown to improve the deinkability of hydrophilic inks. However, LPP treatment was also seen to have a negative impact when hydrophilic inks were mixed with traditional hydrophobic inks. It was hypothesized and shown that LPP treatment has a positive impact on deinking of hydrophilic inks but a negative impact on traditional inks, which led to the development of the adsorption deinking method that can deink both hydrophilic and traditional inks.

University, Diss., 2003--Stuttgart.

Deinking flotation is an important part of the recycling process for used fibers, in which liberation is a key step in preparing the ink particles to be separated from fibers. The pigments of oil-based inks are hydrophobic and, therefore, can be readily separated from hydrophilic fibers by flotation, which is designed to selectively collect hydrophobic particles on the surface of air bubbles. On the other hand, the pigments in water-based inks are hydrophilic; therefore, they cannot be separated from fibers by flotation. Furthermore, the pigments in water-based inks are much smaller than those in oil-based inks and readily redeposit onto the fiber surfaces after they are liberated during the pulping process. Team members and I developed a novel method of measuring the degree of liberation of oil-based ink by ζ-potential measurement. The same method has been used to determine the degree of liberation of water-based ink. It has been found that adding a polyelectrolyte during the pulping stage greatly increases the liberation by increasing the disjoining pressure in the thin liquid film (TLF) of water confined between the pigment and fiber while at the same time preventing re-deposition. After the liberation, the pigments are then hydrophobized by adsorbing a surfactant on the surface to greatly improve flotation deinking. Finally, different types of flotation equipment were tested to identify the optimal flotation system to use in the deinking process. / Department of Energy grant DE-EE0007897, awarded to the REMADE Institute. / Master of Science / Paper recycling is a key way to participate in the circular economy. Part of the process of recycling paper is to remove any ink on the surface of the paper so that a clean white sheet of paper can be produced for additional uses. There are two types of ink commonly used for printing, oil-based and water-based. The latter seeing more and more adoption as climate goals continue to be a focus of society. One of the processes that is used in this process is deinking flotation, where the ink is separated from the fiber, attached to a bubble, floated to the surface, and separated from the fiber. The current work focuses on improving the ability to separate the ink from the fiber, improving the ability of the ink particle to attach to the bubble, and improving the equipment that is used for the separation. The work found that using common dispersants used in the mineral industry, novel reagents, and alternate equipment greatly increased the efficiency of the deinking process.

Firing an underwater spark discharge generates an expanding plasma which causes a spherical shockwave to propagate through the surrounding water. The shockwave can have many effects, including resonance effects on bubbles, mechanical destructive effects on solid surfaces and living organisms, and sonochemical oxidative effects on particles and chemical species present in the water. This phenomenon has been shown to improve the efficiency of ink removal in a laboratory flotation deinking cell, while simultaneously decreasing fiber loss. These process improvements are attributed to the sonochemical oxidation of ink particle surfaces, caused by shockwave-induced cavitation. This finding is supported by zeta potential measurements. Sparking was found to reduce the zeta potential of ink particles by up to 20 mV. When sparking was performed during deinking, no effect was found on either ink removal or solids loss. However, when the pulp was pretreated with sparking before flotation, a significant improvement was seen in the brightness gain. Further, fiber loss was decreased by up to 25% in a single flotation stage. The economics of this process are attractive; payback is on the order of three months based on fiber savings alone. Also, at about 1.5 kJ per spark, the power requirements are minimal with respect to the benefit derived.

Currently most deinking technologies are dependent upon flotation and dissolved air flotation (DAF) technology in order to separate inkjet ink from fiber and water. Much of this technology is based on ink that is extremely hydrophobic. This made flotation and DAF very easy to use because the ink in the water would very easily move with the air in flotation and be brought to the surface, after which the ink can be skimmed and the pulp can be used. Now that small scale printing has become the norm, there has been a move to high quality, small scale printing. This involves the use of a hydrophilic ink. Hydrophilic ink cannot be easily separated from water and fiber the same way the hydrophobic ink can be. With low concentrations of hydrophilic ink in the process water stream, it can be absorbed into the process but as the hydrophilic ink concentration rises alternative methods will be needed in order to separate inkjet ink from water. One solution is to find a method to effectively increase ink particle size. This will enable the ink particles to be filtered or to have an increase ecacy of removal during flotation. In this thesis, one solution is discussed about how electric field and electric plasma technologies can be used to increase particle size and help purify process water in recycle mills. This plasma treatment can very effectively bring ink particles together so that they may be separated by another method. There are two methods by which this may take place. One is polymerization and the other is electro-coagulation. These processes can work side by side to bring ink particles together. This plasma treatment process creates free radicals by stripping off hydrogen atoms from surrounding organic matter. These free radicals then react with the high alkene bond content within the ink to create a very large covalently bonded molecule. This is the new mechanism that is being investigated in this thesis. The other action that is taking place is electro-coagulation. Plasma treated ink can be filtered out using a cellulose acetate or cellulose nitrate membrane or they can be filtered using paper or fiber glass filters as well. The extent at which these can be filtered out is dependent on the size of the pores of the filter. In this study, it was shown that the plasma treatment was able to clean water with a fairly small amount of energy. It was also found that treatment time and concentration had very little eect on the outcome of the treatment ecacy. One factor that did have an effect was the pH. At very high pH values the process became noticeably less eective. The high pH essentially eliminated the electro-coagulation aspect of the treatment process and also hurt the polymerization aspect as well because of lower amount of hydrogen atoms available for the plasma to create free radicals. A model of the process was used to try to give the reader an idea of the ecacy that the process would have in an industrial scale process. The model assumes that two types of ink particles exist. One is ink that has a radical and another in which the ink does not have a radical. The model also assumes that if ink is at all polymerized, ink is filtered out with the 0.8 micron filter. The model assumes three reactions; initialization, propagation and partial termination. The partial termination is a result from the general chemical structure of ink. Ink has many double bonds in its general structure which makes termination very unlikely to occur, so the model assumes that on average when two radials interact that only one is eliminated. This model is only supposed to give the reader an idea of the ecacy of the process. The numbers provided in the model will change very significantly in a different system. The evidence behind polymerization aspect of the process comes from two main sources. One is the small molecule analysis from methanol after being exposed to the plasma and the other from the plasma being exposed to allyl alcohol. The small molecule analysis shows that the process generates free radicals on organic molecules. Methanol was exposed to the plasma and then the resulting GC/MS analysis showed that 1,2-ethanediol was present, this showed that the electric discharge process was able to create free radicals on organic molecules in the liquid phase. Using a similar process the plasma discharge process was exposed to a mixture of allyl alcohol, water and propanol and water in two separate experiments. The difference between these two molecules is an alkene bond that is between the carbon two and carbon three atoms. The particle size of both samples was then analyzed and it was shown that the solution with allyl alcohol had an average particle size about an order of magnitude larger than the solution with propanol in it. Because of all the evidence discussed here and in the rest of the thesis we believe that the plasma treatment of ink has both polymerization and electro-coagulation aspect. This process could also be a potential solution to the water soluble ink problem that will soon face the recycling industry.

No description available.