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Ion Flotation for Color Removal From Kraft Mill Effluent DONALD W. HERSCHMILLER, Project Engineer Envirocon, Ltd. Calgary, Alberta, Canada RICHARD M.R. BRANION, Assistant Professor Department of Chemical Engineering University of British Columbia Vancouver, B.C., Canada INTRODUCTION Pulp and paper wastewater treatment, in its present form, involves the removal of settleable solids and the stabilization of the biodegradable organic fraction of the effluents. The methodology for these two objectives has now been developed to a substantial degree. This treatment does not, however, affect certain properties such as effluent color. This underlies the need for at least another step in the conventional treatment scheme, a tertiary stage to remove, or partially remove, the color containing, relatively non-biodegradable portion of the effluent. Historically (1), this fraction was considered to be relatively innocuous to aquatic life. However, recent work (2,3) has shown that reduced light penetration and the altered spectrum of the light which does penetrate to a measured depth may affect aquatic growth. The soluble, non-biodegradable portion of the pulp mill effluent is composed primarily of wood extractives and lignin degradation products which are formed during the pulping and bleaching processes. A large portion of this material is chromophoric. The purification technique which is the subject of this paper was for the most part, related to just the removal of this chromophoric material. Available information (4) indicates that the chromophores in pulp mill effluents are largely, lignin derived. In the lignin degradation process quinonoid type compounds are usually produced. Figure 1 illustrates a few of the general types of chromophoric structures present in kraft pulping wastes. Figure 2 illustrates some possible sites of degradative attack under the, comparatively, much less harsh conditions of the pulp bleaching operations. The chemicals used in bleaching have been shown (3) to convert lignin to o- or p-quinoid type structures which can then undergo further reactions. Figures 3 and 4 show both a specific example and a generalized mechanism for this procedure. An interesting property of kraft mill wastewater is exhibited by Figure 5 which is a plot of total mill effluent color (or absorbance) versus the hydrogen ion concentration of the effluent. This property, coupled with the fact that a portion of the chromophoric material posses structures very similar to those of such common pH indicators as phenolphthalein, congo, red, or phenol read lead the investigators (4) to the conclusion that "the effluent behaves, in a sense, as a pH indicator" and thus "a substantial portion of the chromophoric material" must posses a negative charge, at least under alkaline conditions. Based on this conclusion the work reported in this paper was undertaken, using the ion flotation technique with a cationic surfactant as the foundation upon which to build. It is interesting to note, at this point, that other investigators (5), proceeding from a slightly different vantage point, embarked on similar studies. Preliminary experiments with this ion flotation technique for kraft pulp mill effluent decolorization proved to be successful. In itself, this event presented a problem; would it be better to investigate a few specific areas, in depth, or to explore the technique as widely as possible? After reviewing all considerations, the latter course of action was chosen. 224
Object Description
Purdue Identification Number | ETRIWC197323 |
Title | Ion flotation for color removal from kraft mill effluent |
Author |
Herschmiller, Donald W. Branion, Richard M. R. |
Date of Original | 1973 |
Conference Title | Proceedings of the 28th Industrial Waste Conference |
Conference Front Matter (copy and paste) | http://earchives.lib.purdue.edu/u?/engext,23197 |
Extent of Original | p. 224-233 |
Series | Engineering extension series no. 142 |
Collection Title | Engineering Technical Reports Collection, Purdue University |
Repository | Purdue University Libraries |
Rights Statement | Digital object copyright Purdue University. All rights reserved. |
Language | eng |
Type (DCMI) | text |
Format | JP2 |
Date Digitized | 2009-06-02 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Resolution | 300 ppi |
Color Depth | 8 bit |
Description
Title | page 224 |
Collection Title | Engineering Technical Reports Collection, Purdue University |
Repository | Purdue University Libraries |
Rights Statement | Digital object copyright Purdue University. All rights reserved. |
Language | eng |
Type (DCMI) | text |
Format | JP2 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Transcript | Ion Flotation for Color Removal From Kraft Mill Effluent DONALD W. HERSCHMILLER, Project Engineer Envirocon, Ltd. Calgary, Alberta, Canada RICHARD M.R. BRANION, Assistant Professor Department of Chemical Engineering University of British Columbia Vancouver, B.C., Canada INTRODUCTION Pulp and paper wastewater treatment, in its present form, involves the removal of settleable solids and the stabilization of the biodegradable organic fraction of the effluents. The methodology for these two objectives has now been developed to a substantial degree. This treatment does not, however, affect certain properties such as effluent color. This underlies the need for at least another step in the conventional treatment scheme, a tertiary stage to remove, or partially remove, the color containing, relatively non-biodegradable portion of the effluent. Historically (1), this fraction was considered to be relatively innocuous to aquatic life. However, recent work (2,3) has shown that reduced light penetration and the altered spectrum of the light which does penetrate to a measured depth may affect aquatic growth. The soluble, non-biodegradable portion of the pulp mill effluent is composed primarily of wood extractives and lignin degradation products which are formed during the pulping and bleaching processes. A large portion of this material is chromophoric. The purification technique which is the subject of this paper was for the most part, related to just the removal of this chromophoric material. Available information (4) indicates that the chromophores in pulp mill effluents are largely, lignin derived. In the lignin degradation process quinonoid type compounds are usually produced. Figure 1 illustrates a few of the general types of chromophoric structures present in kraft pulping wastes. Figure 2 illustrates some possible sites of degradative attack under the, comparatively, much less harsh conditions of the pulp bleaching operations. The chemicals used in bleaching have been shown (3) to convert lignin to o- or p-quinoid type structures which can then undergo further reactions. Figures 3 and 4 show both a specific example and a generalized mechanism for this procedure. An interesting property of kraft mill wastewater is exhibited by Figure 5 which is a plot of total mill effluent color (or absorbance) versus the hydrogen ion concentration of the effluent. This property, coupled with the fact that a portion of the chromophoric material posses structures very similar to those of such common pH indicators as phenolphthalein, congo, red, or phenol read lead the investigators (4) to the conclusion that "the effluent behaves, in a sense, as a pH indicator" and thus "a substantial portion of the chromophoric material" must posses a negative charge, at least under alkaline conditions. Based on this conclusion the work reported in this paper was undertaken, using the ion flotation technique with a cationic surfactant as the foundation upon which to build. It is interesting to note, at this point, that other investigators (5), proceeding from a slightly different vantage point, embarked on similar studies. Preliminary experiments with this ion flotation technique for kraft pulp mill effluent decolorization proved to be successful. In itself, this event presented a problem; would it be better to investigate a few specific areas, in depth, or to explore the technique as widely as possible? After reviewing all considerations, the latter course of action was chosen. 224 |
Resolution | 300 ppi |
Color Depth | 8 bit |
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