The effect of hydrogen ion concentration upon the absorption of dyes by cellulose and fillers

Graduation date: 1934The dyeing of paper is one of the most important\ud processes in the manufacture of that material. Fully 95 percent\ud of the paper that is produced is colored to a greater or\ud lesser extent, and in many eases the reproduction of a shade\ud is essential. That pH is an important factor in the dyeing\ud of paper has been realized, but very little has been done to\ud determine the quantitative effect. This latter was the purpose\ud of this work, and in order that the nature of the process\ud be more fully realized, theories of dyeing were discussed.\ud Experimental results are as follows:\ud The adsorption of Methylene Blue from water solutions\ud of different concentrations was studied and found to follow\ud Freundlich's adsorption law.\ud Adsorption of Methylene Blue at different pH values,\ud where the pH was controlled by means of McIlvaine's buffers,\ud showed a rather steady increase with increased pH, with the\ud exception that on alumina the adsorption rose to a maximum\ud and thereafter decreased. With the same dye, but with the pH varied by means\ud of Al₂(SO₄)₃ - NaOH solutions, adsorption followed, for all\ud cases, the same trend as for alumina above.\ud Adsorption of Victoria Green increased continuously\ud with increased pH when the pH was regulated by Al₂(SO₄)₃ - NaOH solutions. In the higher pH values the adsorption on\ud the fillers and cellulose did not differ materially from\ud the adsorption on alumina alone. Albolith and china clay,\ud however, showed a relatively great affinity for the dye at\ud lower pH values.\ud A study of Alizarine Blue, with pH controlled by\ud Al₂(SO₄)₃ - NaOH solutions, demonstrated that the maximum\ud adsorption was between a pH of about 5.8 and 6.6. Adsorption\ud was very great in this range, but in no case much greater\ud than on alumina alone.\ud Adsorption of Orange R. O., with pH controlled as\ud above, proceeded much as for Alizarine Blue, the maximum\ud adsorption falling between about pH 4.9 and 5.4. Adsorption\ud on albolith and china clay was much greater than on alumina\ud alone, but for the other substances this was not true. Adsorption of the dye was not so great as for Alizarine Blue.\ud A colloidal viewpoint was adopted, as far as possible,\ud for the explanation of the process of dyeing in the cases\ud studied.\ud That alumina is very important in the dyeing of paper\ud was demonstrated