A polyamine(PA) fixing agent, and a cationic polyacrylamide(CPAM) retention aid are used individually as well as in combination to treat the old newsprint pulp, and the focused beam reflectance measurement(FBRM) is used to measure the quantity, the size and the size distribution of the colloidal particles in the pulp filtrate, to reveal the combinative effect of the fixing agent and the retention aid on the controlling of the dissolved and colloidal substances(DCS) in the papermaking pulp raw material. It is indicated that when the PA is used singly to treat the pulp, some colloidal agglomerates will be formed which are not fixed with the fiber or not trapped in the fiber mat, thus they reside in the pulp filtrate; when the CPAM is used singly, its charge will be neutralized easily by the DCS, therefore, its ability to reduce the quantity of colloidal particles in the pulp will be weakened greatly, and larger colloidal agglomerates will not form; when the PA and the CPAM are used in combination, those agglomerates formed by the PA but resided in the aqueous phase will be further retained onto the fiber by the CPAM, in this course, the quantity of the colloidal particles will be reduced and larger colloidal agglomerates that form in the PA treatment will not form.

fixing agent  /  retention aid  /  cooperative control  /  pulp  /  dissolved and colloidal substances