Structuring of ZnTiO3/TiO2 Adsorbents for the Removal of Methylene Blue, Using Zeolite Precursor Clays as Natural Additives

Abstract

Adsorption is an effective method of removing harmful pollutants from air and water. In the present study, zeolites prepared by sol-gel method from two Ecuadorian clays were combined with precursor clays and the ZnTiO3/TiO2 semiconductor for adsorbing methylene blue (MB) as a water contaminant. The synthesized compounds were characterized using powder X-ray diffraction, X-ray fluorescence, scanning electron microscopy, energy dispersive X-ray, and surface area measurement. These compounds were combined to form cylindrical extrudates of 0.2 cm (diameter) and 1.0 cm (length). The adsorption characteristics of the composites were measured using batch sorption studies as a function of pH, initial concentration, and contact time. The pseudo-second-order model and the Langmuir isotherm model were better suited to the adsorption process. The equilibrium state was achieved around 180 min of adsorption, and a pH of 7 was established as the optimal operating condition. The maximum adsorption values of the dye were obtained with the composites derived from G-Clay, whose average adsorption capacity was 46.36 mg g−1, in contrast with composites derived from R-Clay, whose average adsorption value was 36.24 mg g−1. The results reflect that synthesized composites could be used potentially for the removal of cationic dye from wastewater.

DFT Study of Methylene Blue Adsorption on ZnTiO3 and TiO2 Surfaces (101)

“…In a previous experimental paper, we reported the synthesis and characterization of the ZnTiO 3 /TiO 2 nanocomposite. This heterostructure was indexed to a hexagonal phase with space group R-3(148) for ZnTiO 3 and a tetragonal phase with space group I4 1 /amd(141) for TiO 2 (anatase) [39,40]. In these studies, we also reported the ability of ZnTiO 3/ TiO 2 to remove the methylene blue (MB) dye in aqueous systems, and it was contrasted with the results obtained for pure TiO 2 (anatase).…”

La-Doped ZnTiO3/TiO2 Nanocomposite Supported on Ecuadorian Diatomaceous Earth as a Highly Efficient Photocatalyst Driven by Solar Light

“…The relatively high surface area of the DE-immobilized ZTO/La nanocomposite could be a promising material for adsorption and photocatalysis, as well as for other applications. In fact, preliminary studies on the adsorption capacity and photocatalytic activity of the ZTO compound showed promising results for methylene blue (MB) removal in aqueous systems under irradiation with ultraviolet light [ 83 , 90 ]. Although the powdered materials usually have a higher SSA, in this study, the extrudates were chosen to adsorb MB due to their appropriate mechanical and chemical stability, which facilitated their recovery at the end of the process and their reuse after several cycles.…”

“…The ZnTiO 3 /TiO 2 (ZTO) and ZnTiO 3 /TiO 2 /La (ZTO/La) nanocomposites were synthesized following a modified sol-gel method described in previous studies [ 83 , 90 ]. To obtain the ZTO nanocomposite, a quantity of titanium (IV) isopropoxide (TiPO) in isopropyl alcohol (iPrOH) (70 v / v %) was dispersed at room temperature.…”

“…The procedure was repeated using a methylene blue reference solution without extruded adsorbents to eliminate any photolysis effects causing discoloration of the solution due to natural light. The adsorbed quantity q e of methylene blue was calculated by means of Equation (3): where C 0 (mg L −1 ) and C e (mg L −1 ) represent the initial and equilibrium concentration, respectively; v (L) is the volume of the solution; and w (g) is the mass of the adsorbent [ 83 ].…”

“…Each semiconductor substantially affects the surface charge of the material and therefore increases or weakens its photocatalytic capacity [ 30 ]. Among the numerous semiconductor combinations, the integration of ZnTiO 3 with TiO 2 has previously been reported as a promising alternative for the adsorption and photocatalytic degradation of MB in wastewater [ 82 , 83 ]. Although ZnTiO 3 has proven to be the most versatile perovskite-type oxide for various applications [ 84 ], the physical and chemical properties of the ZnTiO 3 /TiO 2 heterojunction have been shown to be greater than those of the individual components, evidently resulting from the modification of their electronic states [ 85 ].…”