Alginate bead microreactors integrated with SDS-MIL-88A and Cu-biochar for adsorption-coupled Fenton-like degradation...

Herein, this study provides a solution to the shortcomings of most heterogeneous Fenton/Fenton-like catalysts, such as high dispersibility and difficulty of separation from the reaction medium. The activity of the Fenton MIL-88A catalyst was enhanced by the functionality of sodium dodecyl sulfate (SDS), and the efficiency of the Fenton-like biochar catalyst was improved by copper doping. The highly efficacious SDS-MIL88A/Cu-BC catalyst was impregnated into the sodium alginate (SA) and shaped into a bead form, yielding the SDS-MIL88A/Cu-BC@SA beads. Various characterization instruments confirmed the successful synthesis of the SDS-MIL88A/Cu-BC@SA beads. The SDS-MIL88A/Cu-BC@SA was applied in the Fenton-like decomposition of the antibiotic tetracycline (Tc) drug, and the optimal reaction conditions were scrutinized after sequential catalytic experiments. The SDS-MIL88A/Cu-BC@SA beads achieved 95.12% Tc decomposition within 60 min, with 44.91% adsorption at pH = 7, dose of the beads = 20 mg, Tc concentration = 50 mg L^-1, system temperature = 20 °C, and H₂O₂ = 100 mg L^-1. In addition, TOC analysis showed approximately 65.9% TOC removal, confirming the partial mineralization of Tc molecules and supporting the formation of smaller degradation intermediates during the adsorption-coupled Fenton-like process. The kinetic investigations of the Fenton-like decomposition of Tc by SDS-MIL88A/Cu-BC@SA obeyed the Second-order model. The proposed mechanistic study suggested that the adsorption of Tc occurs via coordination bonds, hydrogen bonding, n-pi interactions, pi-pi interactions, and Lewis acid-base interactions. Furthermore, the Fenton-like degradation of Tc occurred through the activation of H₂O₂ by ferrous, monovalent copper ions and EPFRs, with the recovery of the active metal species by SDS and EPFRs. The recyclability examination of the SDS-MIL88A/Cu-BC@SA beads revealed that the decomposition % of Tc was over 85% after the fifth catalytic run.