Application of Bi12ZnO20 Sillenite as an Efficient Photocatalyst for Wastewater Treatment: Removal of Both Organic and Inorganic Compounds

Abstract

This work aims to synthesize and characterize a material that can be used as an effective catalyst for photocatalytic application to remove both organic and inorganic compounds from wastewater. In this context, sillenite Bi12ZnO20 (BZO) in a pure phase was synthesized using the sol–gel method. Before calcination, differential scanning calorimetry (DSC) analysis was done to determine the temperature of the formation of the sillenite phase, which was found to be 800 °C. After calcination, the phase was identified by X-ray diffraction (XRD) and then refined using the Rietveld refinement technique. The results prove that BZO crystals have a cubic symmetry with the space group I23 (N°197); the lattice parameters of the structure were also determined. From the crystalline size, the surface area was estimated using the Brunauer-Emmett-Teller (BET) method, which was found to be 11.22 m2/g. The formation of sillenite was also checked using the Raman technique. The morphology of the crystals was visualized using electron scanning microscope (SEM) analysis. After that, the optical properties of BZO were investigated by diffuse reflectance spectroscopy (DRS) and photoluminescence (PL); an optical gap of 2.9 eV was found. In the final step, the photocatalytic activity of the BZO crystals was evaluated for the removal of inorganic and organic pollutants, namely hexavalent chromium Cr(VI) and Cefixime (CFX). An efficient removal rate was achieved for both contaminants within only 3 h, with a 94.34% degradation rate for CFX and a 77.19% reduction rate for Cr(VI). Additionally, a kinetic study was carried out using a first-order model, and the results showed that the kinetic properties are compatible with this model. According to these findings, we can conclude that the sillenite BZO can be used as an efficient photocatalyst for wastewater treatment by eliminating both organic and inorganic compounds.

Synthesis and Characterization of TiO2 Nanotubes (TiO2-NTs) with Ag Silver Nanoparticles (Ag-NPs): Photocatalytic Performance for Wastewater Treatment under Visible Light

“…In addition, these substances are not completely metabolized by organisms. The immediate consequence is that a certain unmetabolized amount ends up directly in the soil and in surface water [4,5].…”

“…Thus, the sources of pharmaceutical substances in the environment are hospital and domestic discharges, which end up in wastewater treatment plants where they are not 2 of 12 completely degraded and therefore discharged into surface water. The concentrations in the receiving environment can thus vary according to the biodegradability of the molecules as well as the capacity of the water treatment stations to eliminate or transform them, as these are designed and mainly sized to treat the so-called physicochemical parameters "conventional" (suspended solids, BOD 5 , DCO, nitrogen, phosphorus) [5]. The immediate consequence of such a situation is that for the past fifteen years, drug residues have been found in river water because some treatment plants are still not equipped with effective processes to retain or degrade them [6][7][8][9][10].…”

Advanced Photocatalytic Treatment of Wastewater Using Immobilized Titanium Dioxide as a Photocatalyst in a Pilot-Scale Reactor: Process Intensification

“…Within the framework of this study, we will be working on the effluents of the Chu de Rennes (a capacity of 10,000 inhabitants in waste equivalent), investigating the question of the origin of various micropollutant substances within the Research of Dangerous Substances in Water (RDSW) framework. The major problems posed by these micropollutants is their toxicity, that is, the carcinogenic, mutagenic, reprotoxic (CMR) character of some of them [9]. Because of this toxicity, they have an impact on the environment (animals and plants) as well as on humans [10].…”

A Review of the Use of Semiconductors as Catalysts in the Photocatalytic Inactivation of Microorganisms

“…The photocatalytic reaction is initiated when the semiconductor photocatalyst is excited by photons after irradiation by the light source. These photons cause the electrons (e − ) on the surface photocatalyst to become 'excited' in the valance band if the energy of the photons (E hυ ) is greater than or equal to the bandgap (Eg) [26][27][28]; this causes the e − to jump into the conduction band. Once the e − have absorbed to the conduction band (e CB − ), a positive hole is formed on the valence band (h VB + ), according to the following equation:…”