GB569306A - Improvements in or relating to processes of treating an impure solution or liquid containing organic material, particularly processes of purifying sugar solutions and the like - Google Patents

Abstract

A process for treating an impure acidic liquid containing organic materials, particularly an acidic sugar or dextrose solution obtained in the acid conversion of starch products in the production of sugar, or in the treatment of aqueous wood extracts, comprises treating the liquid first with an active carbonaceous material, particularly a decolourizing carbon, and then with an acid-adsorbing or acid-removal body. After treating the liquid, if necessary, with a hydrogen-exchange body, e.g. a zeolite prepared by the treatment of wood, lignite, coal, or other carbonaceous material with strong sulphuric acid, or a cation-exchange body such as a condensation product of a polyhydric phenol and formaldehyde, whereby the inorganic salts are converted into the corresponding acids, it is passed through a bed of granular activated carbon where colouring-matter and other organic colloids and dissolved organic impurities are removed. The liquid is subsequently passed through the acid-adsorption body, which may consist of a m-phenylene-diamine-formaldehyde, aniline-aldehyde, guanidine-formaldehyde, or dicyandiamide resin or an oxide of iron or aluminium. The liquid when passed through the carbon bed should have a pH value less than 7 and preferably less than 4.3, and the carbon can then be reactivated when exhausted by treatment with a dilute alkali solution, e.g. a 0.5-5 per cent solution of sodium hydroxide. The solution used may be that which has already been used in regenerating the acid-absorbing material. Prior to reactivation, the carbon is preferably washed with water, and after treatment with hot or cold alkali, it can be treated with acid, e.g. sulphuric or hydrochloric acid or, preferably, carbon dioxide, to facilitate removal of the alkali by further washing. The alkali solution can be treated for recovery of the contained substances. In order to prevent inversion of the sugar, a small amount of alkaline substance may be added to restore the pH value to at least 7, any carbon dioxide dissolved in the liquor being preferably first removed by aeration. Specification 554,826 and U.S.A. Specification 2,151,883 are referred to.