Magnetically separable solid phase extractor for static anionic dyes adsorption from aqueous solutions

Abstract

Thiourea was successfully deposited on the surface of Fe3O4 nanoparticles (via a one-pot reaction with formaldehyde) for the purpose of developing a new adsorbent (MNPs-TF). The application of MNPs-TF to capture congo red (CR) and methyl orange (MO) as model examples of anionic dyes from their aqueous solutions was assessed. Several physicochemical parameters of pH, MNPs-TF dosage, dyes concentrations, residence time, temperature, and co-interfering ions were exhaustively trialed to comprehend the corresponding distribution of dyes species onto MNPs-TF at the molecular scale. To better interpret the adsorption process, kinetics, isotherm, and thermodynamics were proficiently modeled. Collectively, the findings pave that the dyes removal pathway was favorable in the acidic environment (pH0 = 3.8). Moreover, the kinetics data were more reliable to be matched with pseudo-second-order rate equation, whereas the equilibrium isotherms insights extrapolated that the adsorption process was dominated by Langmuir assumption with maximum loading capacities of 0.56 mmol g−1 and 1.43 mmol g−1 for CR, and MO, respectively. What is more, the temperature profiles studies suggested the exothermic nature of the process. Interestingly, the synthesized adsorbent possessed high recyclability of > 92% up to the 6th cycle. The potency of MNPs-TF as point-of-use color collecting candidates from real dyeing effluents was accomplished.