Characterization studies of red mud modification processes as adsorbent for enhancing ferricyanide removal.

In this study, waste solids of the alumina industry (red mud) have been modified and utilized as a ferricyanide adsorbent which is characterized by XRD, XRF, FTIR, SEM, EDX, ICP and BET analysis. The four modification methods including the processes of washing with seawater (B), acid treatment Bauxsol (ATB), activated ATB using ammonia (ABA), and activated Bauxsol using cetyltrimethylammonium bromide (CTAB) (ABC) were evaluated to increase the reactivity of red mud (RM) for ferricyanide removal. The ferricyanide adsorption capacity was obtained at 12.40, 6.84, 2.95, 2.50 and 0.44 (mg/g) for ABC, ATB, ABA, B and RM, respectively. The CTAB with a concentration above the critical micelle concentration changed the negative charge of red mud to positive charge. It decreased the negative charge repulsion force between the Bauxsol surface and ferricyanide ions. The adsorption capacity of ferricyanide was decreased from 12.40 to 2.75 (mg/g) with increasing the adsorbent amount from 0.5 to 5 (g). The results showed that the activated Bauxsol using CTAB could be effectively used as a new adsorbent for ferricyanide ions from wastewaters.