In the preparation of tannin extract from chestnut wood chips there is present in the extract, along with the tannin, certain insoluble non-tannin constituents. If allowed to remain in the extract, these materials make the tanning solution unsuitable for use in the manufacture of leather.

To accomplish the separation of the non-tannin constituents from the tannin, the Lead Corporation of Lynchburg, Virginia, now employs a process of concentration and mechanical settling. For the past twenty years the company has been engaged in research to develop a better process. The investigations have been concentrated mainly on the idea of varied forms of mechanical separation. So far no solution to the problem has been found, thereby giving rise to the opinion that perhaps mechanical separation is the wrong approach to the problem.

In a preliminary study of this problem 6), research work has been done at V.P.I. using several new approaches, the most important of these being electrophoresis and adsorption. Of these two procedures, adsorption save indications of having the greater potentialities. The following thesis will deal with additional research work using coals of varying grades as an adsorbing medium.

The American Viscose Company of Roanoke, Virginia has installed units for clarifying the spinning bath solutions. The units incorporate coal as an adsorbing medium. The process is extremely successful and therefore strengthens the belief that it may be applicable to the clarification of tannin extract solutions.

Adsorption methods are often applied industrially to remove impurities, especially if they are present in low concentrations. Small amounts of impurities often interfere with processes such as crystallization, filtration, and distillation, but by the application of adsorption the impurities may be separated and the fault corrected. Often times adsorbents are used to recover valuable constituents, which otherwise would be lost completely or require for more costly processing.

Separation by adsorption is made possible because of the fact that different materials differ in the degree to which they are adsorbed by a given adsorbent.

The object of the research work is to investigate the possibility of developing an economically feasible process, based on adsorption, using coal as the adsorbent, for the separation of the insoluble non-tannin constituents present in a fresh tannin extract.