Some Aspects of Flocculant Use in the Phosphatation Process

The influence on impurity removal exerted by the application of flocculants in the phosflotation process has been investigated. A number of cationic flocculants are shown to enhance the removal of colour and starch. The use of flocculants did not influence the turbidity and conductivity ash of the clarified liquor. Changes in filterability and phosphate content of clear liquor resulting from the application of flocculants are also detailed. Introduction Phosflotation (Phosphatation-flotation) is a widely practised method for the defecation of a raw sugar melt. The process involves the coagulaticln of impurities with a calcium phosphate precipitate followed by the flotation of this coagulum to yield a clear liquor underflow. In recent years, a number of new mate r i a l~ l -~ .~ have been introduced in order to improve the efficiency of the process. An upgrading in the throughput of flotation clarifiers ha:; been achieved by the application of high molecular weight anionic polyacrylamides as flotation aids5 Due to their long chain length and negative charge in solution, these polymers build up large flocs which can be floated at a much enhanced velocity. This ensures a high throughput of turbidityfree liquor. One of the important developments has been the introduction of the Talofloc pro~e:ssl-~ which aims at achieving a large measure of decolorii~ation during defecation. A cationic surfactant (Talofloc) is added prior to the precipitation of phosphate and the final aerated suspension of calcium phosphate coagulum is flocculated by the addition of an anionic polyacrylamide (Taloflote). The advantage of obtaining considerable decolorization in the phosphatation process lies in the greater econom!~ that can be achieved in the subsequent decolorizing stage." The purpose of this study was to investigate the degree of impurity removal that can be achieved with the aid of cationic flocculants. In addition, the effect on the process of a polyacrylamide flotation aid was investigated.