Adsorption potential of polymer metal oxide composites for crystal violet and basic fuchsin: isotherm, kinetics, and thermodynamic studies

Abstract

Dyes are water-soluble color contaminants. The presence of color contaminants is known to disturb the lifecycle of the marine ecosystem. To deal with the dye contamination issue and to meet the increasing demands for sustainability three biomaterial-based adsorbents have been investigated using previously synthesized biomaterial-based composites i.e., β-cyclodextrin (β-CD) polymer-metal oxide composites namely β-CD-epichlorohydrin-tetrafluroterephthalonitrile polymer/zinc ferrite composite (β-CDZnF), carboxymethyl cellulose-β-CD-succinic acid/nickel cobaltite composite (β-CDCMCNC), and carboxymethyl cellulose-β-CD-epichlorohydrin-tetrafluroterephthalonitrile/zinc oxide composite (β-CDCMCZO) for the adsorptive removal of two cationic dyes [i.e., crystal violet (CV) and basic fuchsin (BF)]. All three adsorbents were known to possess similar adsorption removal for both CV and BF, due to structural similarity between these two dyes. The Langmuir maximum adsorption capacity for CV and BF using these adsorbents was 302–472 mg g− 1, indicating good adsorptive removal potential (T = 30 °C). Under optimized conditions, the adsorptive removal of dye was accompanied by a negative ΔGo value ranging from − 26.7 to -34.3 kJ mol− 1 indicating spontaneity, which was enhanced with rising temperatures. Comparing the equilibrium time, β-CDZnF (45–60 min) was found to be superior adsorbent over β-CDCMCNC (120–150 min) and β-CDCMCZO (120–150 min). In the presence of Na+, K+, Mg2+, and Ca2+, a notable decline in the adsorption performance of all composites was observed with a higher decline in the presence of divalent Mg2+ and Ca2+ salts and the decline was more evident with increasing the salt concentrations, indicative of competitive adsorption due to attraction towards the negative composite surface (negative zeta potential pH > 3). The regeneration-reuse investigations suggested that the composites maintained their adsorption for CV and BF with no drastic decline in the performance up to five cycles (retaining R% > 75%). The findings of this study are valuable for researchers aiming to address dye contamination using eco-friendly and reusable materials with data-driven tools like artificial neural networks (ANN) to enhance the efficiency of water purification technologies and save experimental trials using predictive modeling. Composite adsorbents containing ZnO, ZnFe2O4, or NiCo2O4 filler in β-CD based polymeric matrix show significant adsorption with Langmuir qm ranging 302 < qm<472 mg g−1. After five regeneration reuse cycles β-CDZnF, β-CDCMCNC, and β-CDCMCZO retained BF or CV qe 247–252, 225–233, and 113–119 mg g−1, respectively, indicating high performance maintenance. Faster adsorption of CV and BF achieved using β-CDZnF adsorbent with 60 min compared to β-CDCMCNC and β-CDCMCZO (120–150 min). ANN trained algorithm for effective adsorption capacity predictions eliminating the need for time and resource consuming experiments.

Topics & Concepts