Adsorption potential of CuO-embedded chitosan bead for the removal of acid blue 25 dye
Ismaila Olalekan Saheed, Nuraliah Irdina Zairuddin, Syaza Atikah Nizar, Megat Ahmad Kamal Megat Hanafiah, Ahmad Faiz Abdul Latip, Faiz Bukhari Mohd Suah
Abstract
Anthraquinone-based anionic dyes like acid blue 25 (AB25) are among the problematic class of pollutants in wastewaters that are detrimental to human health and aquatic organisms. Chitosan (CS), a biopolymer with rich amino and hydroxyl groups is a potential adsorbent for anionic dye but its instability in acidic medium is its major drawback. In this work, the potential of an innovative and sustainable chitosan-copper oxide bead (CS-CuO) developed to adsorb AB25 from aqueous environment was assessed. The batch adsorption process was studied for significant operational variables, and the CS-CuO was methodically characterised using XRD, FTIR, TGA, SEM and EDX. Unlike CS, the prepared CS-CuO was stable in an acidic and basic medium. XRD pattern of CS-CuO revealed an amorphous and crystalline phase. The micrograph of CS showed a non-porous membranous surface, while CS-CuO shows a relatively rough and irregularly shaped sheet-like structure perforated with pores network. The functional groups O−H, C═O, C−O and N−H on the CS-CuO support its attachment to AB25 dye as reflected in change of absorption signals on FTIR spectra. Electrostatic attraction between AB25 and CS-CuO was most favoured at pH 6 where highest AB25 removal occurs. The adsorption capacity of 294.1 mg/g was obtained for the adsorption process at initial dye concentration of 100 mg/L at pH 6. Langmuir isotherm model and pseudo-second-order kinetics best described the adsorption. The spent CS-CuO was better regenerated in the basic solution (0.1 M NaOH), and its reusability gave 80 % desorption capacity at 3rd cycle.