A novel magnetic geopolymer-based adsorbent prepared from heated glauconite and separated magnetite: Experiments and statistical physics treatment for crystal violet

Sinai copper ore with 9.48 % of Fe2O3 was treated using a laboratory-scale mineral processing techniques that included size reduction (below 75 mu m) and a wet low intensity drum-type magnetic separation. After this treatment method, the separated magnetite product containing about 85 % of Fe2O3 was extracted. A mixture of heated glauconite (900 degrees C/2h) and the extracted magnetite was activated by sodium silicate (Na2SiO3) to obtain a novel glauconite-based magnetic geopolymer (namely GMG). Several analytical techniques (i.e., XRD, XRF, FESEM, FTIR, EDX, TEM, elemental mapping, and zeta potential) were used in the characterization of GMG and its performance for crystal violet (CRV) remediation was studied. The equilibrium data at pH 8.0 and 25 - 50 degrees C were fitted to a statistical physics multilayer model and classical isotherm equations to understand the CRV adsorption mechanism. The theoretical calculations indicated that GMG can adsorb 1.12 to 1.39 of CRV molecules per functional group (n), suggesting the presence of a multi-interaction mechanism and vertical adsorption orientation on GMG surface. For this basic dye, the estimated saturation adsorption capacities (Qsat) ranged from 684 to 612 mg/g, and an exothermic binding interaction was associated with the removal of this dye molecule. The adsorption energies (Delta E) ranged between 15.05 and 36.74 kJ/mol, indicating that physical forces, such as electrostatic interactions and hydrogen bonds, governed the GMG-CRV interactions. After fourth adsorption-desorption cycles, the regenerated GMG showed 74 % of its adsorption capacities, which suggested the suitability of this adsorbent to be regenerated and reused multiple times in water treatment. Overall, the combination between the separated magnetite and glauconite was an effective approach for the remediation of effluents that contain dye molecules