Synergistic and competitive adsorption of cationic and anionic dyes on polymer modified yeast prepared at room temperature

Poly (allylamine) modified yeast was prepared and used as an adsorbent for removal of cationic dye (rhodamine B) and anionic dye (congo red) from aqueous solution in single and binary dye systems. XPS and zeta potential analysis showed that the polymer was modified on the sorbent surface and isoelectric point of the sorbent increased from 3.2 to 9.5 after modification. Adsorption test showed that the amine groups modified yeast had higher adsorption capacity and affinity toward congo red than rhodamine B in single and binary system, revealing the electrostatic adsorption mechanism. In the single dye system, the adsorption capacities of the modified sorbent for congo red and rhodamine B were 0.24 and 0.03 mmol/g, respectively. In the binary system, rhodamine B adsorption was promoted by the presence of congo red (synergistic effect), but congo red adsorption was not promoted by the presence of rhodamine B. Antagonistic effect was observed for congo red adsorption at comparative high concentration of rhodamine B. It was for the first time to find that the ratio of the adsorption capacities for congo red and rhodamine B on the modified yeast was proportional to the ratio of the initial concentration of the two dyes. Total adsorption capacity of the modified yeast increased linearly both with the increase of the initial concentration of the two dyes. (C) 2015 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.