Mechanisms of collector chemistry in flotation deinking: Parts I, II, and III.Application: New insights into the mechanism of flotation deinking using surfactants. Part I examines the effects of three surfactants; Part II identifies the conditions that maximize aggregation of ink particles; Part III looks at the mechanisms favoring preferential removal of ink over fiber. Paper recycling Paper recycling is the process of recovering waste paper and remaking it into new paper products. There are three categories of paper that can be used as feedstocks for making recycled paper: mill broke, pre-consumer waste, and post-consumer waste. is, in theory, a simple two-step process. First you treat the secondary fiber to separate inks and contaminants from recoverable fibers, then you remove the contaminants. Flotation deinking is an efficient method of removing larger ink particles (10-150 [micro]m), with the process achieving maximum efficiency for particles measuring 15-50 [micro]m. Thus the ideal flotation chemistry is one that causes small, detached ink particles to aggregate into larger hydrophobic hydrophobic /hy·dro·pho·bic/ (-fo´bik) 1. pertaining to hydrophobia (rabies). 2. not readily absorbing water, or being adversely affected by water. 3. agglomerates that are readily captured by rising air bubbles. In flotation deinking, a surfactant Surfactant Definition Surfactant is a complex naturally occurring substance made of six lipids (fats) and four proteins that is produced in the lungs. It can also be manufactured synthetically. (typically a fatty acid fatty acid, any of the organic carboxylic acids present in fats and oils as esters of glycerol. Molecular weights of fatty acids vary over a wide range. The carbon skeleton of any fatty acid is unbranched. Some fatty acids are saturated, i.e. or soap), an activator (calcium), and the ink particles interact to promote attachment of ink particles to rising air bubbles. The surfactant is thought to interact with the ink by either adsorption adsorption, adhesion of the molecules of liquids, gases, and dissolved substances to the surfaces of solids, as opposed to absorption, in which the molecules actually enter the absorbing medium (see adhesion and cohesion). on the ink or as a precipitated particle. Study objective This study attempts to provide some insights into the mechanism of flotation deinking using surfactants. Part I investigates the mechanism of interaction between different anionic an·i·on n. A negatively charged ion, especially the ion that migrates to an anode in electrolysis. [From Greek, neuter present participle of anienai, to go up : ana-, ana- surfactants, calcium, ink particles, and air bubbles. In Part II, the aggregation of ink particles under different conditions is reported as particle size distributions. Part III examines flotation and preferential removal of ink in the presence of paper fibers. Part I: Ink floatability Using a soap that is more soluble than those used in past studies, the authors were able to perform experiments with and without precipitation of the surfactant with the calcium activator. The results demonstrate that flotation deinking is enhanced by surfactant adsorption on ink particles, synergized by coadsorption of calcium. Figure 1 show the proposed mechanism of collector chemistry. Good flotation efficiencies were obtained in the absence of precipitation, thus eliminating the mechanism of surfactant precipitate as the responsible agent for ink attachment to air bubbles. [FIGURE 1 OMITTED] Part II: Ink aggregation Laboratory results demonstrated that aggregation of ink particles is enhanced by the presence of fatty acids and calcium, which is consistent with the improved flotation observed under the same conditions outlined in Part I. Fatty acids are effective in flotation deinking because their carboxylate carboxylate, n a carboxylic acid salt, ester, or ion. groups have a special affinity tar calcium, and their interaction promotes synergistic adsorption onto hydrophobic ink particles. Calcium bridging plays a role in particle agglomeration ag·glom·er·a·tion n. 1. The act or process of gathering into a mass. 2. A confused or jumbled mass: , as seen in Fig. 1. Part III: Differential flotation of ink and fibers Preferential flotation of ink is the fundamental objective in flotation deinking of secondary fiber. The highly synergistic adsorption of fatty acids and calcium on ink particles promotes agglomeration and removal from the system, as seen in Parts I and II of this study. Significant adsorption of the surfactant also occurs on the fibers, but the fibers do not interact with the carboxylate and calcium ions in the same manner as the ink particles. The preferential coadsorption of fatty acid with calcium on ink particles--but not onto paper fibers--explains the preferential removal of the ink in flotation deinking. Riviello and Faisant were graduate research assistants while at the University of Oklahoma University of Oklahoma, abbreviated OU, is a coeducational public research university located in the U.S. state of Oklahoma. Founded in 1890, it existed in Oklahoma Territory near Indian Territory 17 years before the two became the state of Oklahoma. . Scamehorn is the Asahi Glass chair in chemical engineering, and director, Institute for Applied Surfactant Research, University of Oklahoma, 100 E. Boyd, Rm. T-335, Norman OK 73019-1004, USA. Christian, now deceased, was a George Lynn Cross George Lynn Cross (May 12 1905–December 31 1998) was the seventh and longest serving President of the University of Oklahoma from 1943 to 1968. His academic specialty was botany. He was an outspoken proponent of World War II who felt democracy should be defended at all costs. research professor in chemistry and former director of the Institute, Faisant is now a graduate student at CUST, Department Genie Physique, Institut des Sciences de I'lngenieur de Clermont--Ferrand, Clermont--Ferrand, France. Riviello is now an assistant perfumer with Firmenich, SA, Route des Jeunes, 1, CH-1211, Geneva Geneva, canton and city, Switzerland Geneva (jənē`və), Fr. Genève, canton (1990 pop. 373,019), 109 sq mi (282 sq km), SW Switzerland, surrounding the southwest tip of the Lake of Geneva. 8, Switzerland. Address correspondence to Scamehorn by email at scamehor@ou.edu |
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