Highly effective removal of cobalt from aqueous solution via reusable nanocomposite of metal organic frame work and activated algae encapsulated onto double layer biopolymer

Abstract

A significant number of researchers are focused on identifying effective methods for removing Co(II) ions from industrial wastewater. Nevertheless, current removal techniques often inadvertently eliminate other valuable metals, potentially resulting in economic disadvantages. A novel metal–organic framework has been synthesized using thorium and activated algae, encased in a double-layer hydrogel of chitosan and alginate (TMACA). Several methods were used to thoroughly characterize the adsorbent’s characteristics, such as XRD, FT-IR, XPS, FESEM, EDX, and nitrogen adsorption/desorption isotherms, to elucidate its textural characteristics. A detailed examination of nitrogen adsorption and desorption isotherms provided valuable insights into the textural characteristics of TMACA hydrogel beads. The specific surface area was quantitatively evaluated at around 1216.41 m²/g, indicating significant surface interaction potential, while the total hole volume was quantified at 0.747 cm³/g. These metrics imply that the TMACA hydrogel beads possess a notably efficient porous structure. Furthermore, the calculated average radius of particle was found to be 1.12 nm. This study analyzed how dosage, original concentration, pH, and temperature affect adsorption. The outcomes showed that the adsorption mechanism followed the pseudo-second-order model and the Langmuir isotherm. With an energy of 31.8 kJ.mol⁻¹, chemisorption was the primary adsorption process. Higher temperatures increased metal adsorption, indicating the procedure is endothermic besides spontaneous. Through calculated tests, the adsorption process was significantly improved by using the Box-Behnken design utilising response surface methods in Design-Expert software. The study parameters included 0.02 g of TMACA hydrogel beads per 25 ml, pH of 6, and an adsorption capability of 445.8 mg/g aimed at the Co(II) solutions. The results showed that the adsorbent showed consistent stability and that its effectiveness in removing impurities did not decrease after five consecutive cycles of adsorption and desorption. Additionally, the substance maintained its initial chemical composition both before and after its reuse, demonstrated reliable effectiveness, and exhibited stable X-ray diffraction (XRD) characteristics throughout the process.