BULETINUL INSTITUTULUI POLITEHNIC DIN IAŞI Publicat de Universitatea Tehnică „Gheorghe Asachi” din Iaşi Tomul LVIII (LXII), Fasc. 1, 2012 SecŃia CHIMIE şi INGINERIE CHIMICĂ PERFORMANCES OF NATURAL POLYELECTROLYTES BASED ON STARCH IN AGGREGATION AND STABILIZATION OF AQUEOUS COAL-CONTAINING SYSTEMS BY CARMEN ZAHARIA ∗ “Gheorghe Asachi” Technical University of Iaşi, Faculty of Chemical Engineering and Environmental Protection Received: November 14, 2011 Accepted for publication: December 9, 2011 Abstract. The paper presents some preliminary aggregation-stabilization studies of some coal-containing colloidal systems (un-oxidated and oxidated coal with H 2 O 2 ) as a result of starch action as flocculation agent or coagulation aid. There were used coal dispersion samples of different turbidity, at different pH values, with or without coagulant (aluminium sulphate, 10 -1 -10 -4 M) or flocculant (starch solution, 5-35 mg/L) doses. In these experiments were determined the relative absorbance progress of aqueous systems, but also the critical values of pH and coagulant/starch concentration for initiating aggregation of aqueous colloidal systems (coagulation/flocculation), and also those corresponding to stabilization of colloidal systems (action of starch as stabilization agent or solid protection agent). Key words: aggregation, colloidal coal-containing aqueous suspension, flocculation, natural polyelectrolyte, stabilization, starch. ∗ Corresponding author; e-mail: czah@ch.tuiasi.ro