A novel sulfonated polybenzothiazole-based adsorbent for simultaneous capture of organic dyes from aqueous solution

In this study, we synthesized a novel sulfonated polybenzothiazole (sPBT) which permitted the development of a sodium alginate-based composite (SA-sPBT), and this composite demonstrated promising potential as an adsorbent for the simultaneous removal of Malachite Green (MG) and Neutral Red (NR) from aqueous solutions. Experimental results revealed that SA-sPBT exhibited excellent adsorption performance for MG and NR in both single and binary dye systems. The adsorption isotherms of MG and NR in single-dye systems were well described by the Langmuir model. Kinetic studies showed that both MG and NR adsorption aligned with pseudo-second-order and pseudo-first-order models, respectively. Thermodynamic analyses indicated that the adsorption processes for both dyes were endothermic, spontaneous and feasible. The statistical physics model revealed distinct adsorption behaviors: in single-component systems, NR was adsorbed predominantly via pure non-parallel orientations, while MG exhibited no pure non-parallel orientation at a single adsorption site on SA-sPBT. In the binary dye system, competitive adsorption was observed, with NR showing higher adsorption energy compared to MG, leading to its preferential attachment to adsorption sites. Mechanistic insights were further explored using FT-IR, XPS and DFT calculations, confirming the efficacy of the SA-sPBT composite for organic dye removal from wastewater.