Abstract
The adsorption capacity of the medication methylthioninium chloride (MC) from aqueous solution onto sunflower seed shells (SSS), a low cost and abundant alternative adsorbent, was investigated in a batch system. The surface properties of the adsorbent were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), specific surface area (by using the Brunauer–Emmett–Teller equation), the liquid displacement method and pHPZC. The ability of SSS to remove the medication was assessed through kinetic, thermodynamic and equilibrium investigations. The adsorption efficiency of the SSS adsorbent for the removal of MC was evaluated considering the effects of its concentration, temperature, adsorption contact time, and the pH of the medium. The results obtained from the kinetic and isotherm studies show that the adsorption of the MC on SSS follows pseudo-second-order kinetics (R² > 0.99) and the Temkin isotherm model (R² = 0.97), respectively. The thermodynamic study showed that the adsorption was endothermic and spontaneous, according to its physisorption mechanism. The mathematical modeling of this process was carried out by using the surface response methodology of Box–Behenken. It was possible to deduce a statistically reliable regression equation that related the adsorption yield to the chosen operating parameters, that is, the initial MC concentration, the adsorbent dosage and the pH. Analysis of the variance indicated that the most influential parameters were the SSS dosage, the pH and their interaction and showed the optimal values for ensuring the best adsorption capacity of 95.58%.
Highlights
There has been a great deal of concern about the detection of pharmaceuticals and personal care products in soil, sediments, surface and groundwater [1] as they have become major pollutants due to their low biodegradability, high persistence, and facile bioaccumulation [2]
Sci. 2020, 10, 3271 pharmaceutical field, but it is used in several other industrial fields including textiles, leather, cosmetics, paper, printing, plastic and food [7,8,9].methylthioninium chloride (MC) is often present in the various effluents that are discharged into the environment
Two approaches were used, the first was the evaluation of MC adsorption on seed shells (SSS) by kinetic, thermodynamic and equilibrium studies; and the second was modeling with an experimental
Summary
There has been a great deal of concern about the detection of pharmaceuticals and personal care products in soil, sediments, surface and groundwater [1] as they have become major pollutants due to their low biodegradability, high persistence, and facile bioaccumulation [2]. Among these products, methylthioninium chloride (MC), which is part of a type of medication derived from phenothiazines, has been widely used in a variety of medical treatments, such as methemoglobinemia [3] and lymphatic mapping/sentinel lymphadenectomy in staging melanoma and breast cancer [4]. The continuous release of this pollutant into the environment significantly affects human health and aquatic systems [9,10]
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