Biopolymer-based composite adsorbent beads for the removal of methylene blue dyes

Abstract

Dyes containing waste streams are the most common pollutants found in wastewater, posing a severe threat to both the ecosystem and the environment. Adsorption emerges as one of the most effective and widely applied treatments for removing dyes due to its simple operation, high efficiency, and low cost. Sodium alginate, as a biopolymer, is one of the alternative adsorbents used in the adsorption process. However, the lack of active sites and low rigidity limits the adsorption capacity performance of this biopolymer. This study aims to introduce biopolymer-based composite adsorbent beads for removing methylene blue (MB) dye from an aqueous solution. Herein, TA/PANI/SA composite adsorbent beads consisting of tannic acid (TA) and polyaniline (PANI) were prepared by the cross-linking method of sodium alginate (SA) with the presence of divalent cations in calcium chloride. Characterization was performed using FTIR analysis to determine the changes in surface-modified composite beads. The results indicated that the removal efficiency of MB dye exhibited a significant enhancement of up to 72% when compared to untreated alginate beads, which only achieved approximately 30% removal. It was also found that the interactions occurred during the cross-linking process as well as during the adsorption process of MB dye onto the composite adsorbent beads. The adsorption mechanisms of MB dye by composite adsorbent beads include electrostatic interaction, π-π interactions, and hydrogen bonding. The improvement in the removal efficiency and the possibility of interactions during the cross-linking process suggested that the biopolymer-based composite beads have great potential to be used as adsorbents for removing dye in an aqueous solution.