Abstract
Pure rutile TiO2 nanoparticles (Rt) were combined with exfoliated black clay (BC) to prepare a new composite for water decontamination, in particular, for the uptake of methylene blue (MB) and methyl orange (MO) dyes. The as-prepared Rt/BC was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Field emission scanning electron microscopy (FESEM) techniques, and the dyes’ adsorption isotherms at three temperatures (i.e., 25, 40, and 50 °C) were studied. The results indicated that Rt/BC displayed a high removal performance for MO (96.7%) and MB (91.4%) at pH 3.0 and 8.0, respectively. Adsorption data of MB and MO were adjusted by a double layer model at all temperatures. The theoretical parameters of this statistical physics model were interpreted to understand the MO and MB adsorption mechanisms at the molecular level. The removed molecules per active site (n) of Rt/BC ranged from 1.12 to 1.29 for MB and 1.47 to 1.85 for MO, thus representing parallel orientation and multi-interactions mechanisms (i.e., van der Waals forces, hydrogen bonding, and electrostatic interactions were involved). The Rt/BC composite had a density of surface adsorption sites of 100 mg/g. The aggregation of MO molecules was high and increased their adsorption capacities (Qsat = 294–370 mg/g) compared to that of MB (Qsat = 214–249 mg/g). Adsorption energies were 9.70–20.15 kJ/mol, and these values indicated that MO and MB adsorption processes were endothermic and occurred via physical interactions. Overall, the low cost, high regeneration performance, and stability of Rt/BC support its application as a promising adsorbent for organic pollutants from wastewaters.
Highlights
Different industrial activities, such as textiles, printing, food, and cosmetics, use organic dyes as coloring materials to supply products with distinctive colors [1,2,3,4]
The X-ray diffraction analysis (XRD) pattern of rutile TiO2 nanoparticles (Rt)/BC composite displays diffracting lines corresponding to black clay and titanium oxide rutile nanoparticles (Figure 2a)
The minor variations in the montmorillonite and kaolinite peaks intensities could be associated with the interface between rutile nanoparticles and H2 O2 -activated black clay
Summary
Different industrial activities, such as textiles, printing, food, and cosmetics, use organic dyes as coloring materials to supply products with distinctive colors [1,2,3,4]. TiO2 nanoparticles are widely employed in decreasing the concentrations of dyes through degradation and adsorption techniques because of their chemical inertness, non-toxicity, and high capability of interaction with organics in waters [21,22,23,24,25,26,27]. The energetic and steric parameters related to the advanced statistical physics models (ASPMs) can delineate the adsorption interactions between the investigated dyes and the adsorbent surface at a molecular scale [9,13]. The steric and energetic parameters from the advanced statistical physics models were employed to clarify the performance of Rt/BC for MB and MO dyes’ removal and provide new insights on the adsorption mechanisms considering the molecular level
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