Optimized formulation of NiFe2O4@Ca-alginate composite as a selective and magnetic adsorbent for cationic dyes: Experimental and modeling study

Abstract

This paper reports a data-driven modeling methodology undertaken to establish the optimal formulation of NiFe2O4@Ca-alginate composite designed for adsorption applications. Adsorbents were produced as anisotropic plate-like particles that were applied for removal of Rhodamine-6G (Rh6G) and Methylene Blue (MB) cationic dyes from aqueous solutions. Data-driven models were developed to establish the composition-performance relationships and to optimize the formulation of the composite adsorbent. The optimal formulation of NiFe2O4@Ca-alginate composite implied a content of 16% (w/w) NiFe2O4 nanoparticles into the alginate matrix. Likewise, kinetics, isotherms and thermodynamics studies were carried out and reported in this paper. The optimal adsorbent (NiFe2O4@Ca-alginate) yielded a remarkable maximal sorption capacity equal to 1243 mg/g (for MB uptake) and 845 mg/g (for Rh6G) at the room temperature (298 K). Dubinin-Radushkevich (D-R) isotherms revealed the mean free energy of sorption ranging from 7.23 to 9.26 (kJ/mol) suggesting that the mechanism of adsorption was based on both physical interactions and ion exchange. This evidence was also corroborated by the molecular docking simulations that highlighted valuable insights regarding the intermolecular interactions between alginate chains and cationic dyes.