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During the last decade, there is a growing interest in developing efficient photocatalysts with a visible light sensitivity. Herein, visible-light-driven photoactivity of CrFeO3 prepared by nitrate route was studied. The photocatalysis was evaluated through the Ni2+ reduction. The X-ray diffraction (XRD) is characteristic of a single phase crystallizing in the ilmenite structure with a good crystallinity. It was characterized by the SEM, TEM/HRTEM, FTIR spectroscopy and thermal analysis (TG). The optical and dielectric constants are determined from the diffuse reflectance data. The refractive index (n), extinction coefficient (k), relaxation time (τ), dissipation factor (tan δ) and optical conductivity are extracted. The forbidden band Eg (= 1.65 eV), was computed and confirmed by different methods. The electrical conductivity (σ) augments exponentially with 1000/T and activation energy of 0.22 eV was calculated. The p-type conduction is evidenced from the capacitance measurements with a flat band potential (Efb = −0.38 VAg/AgCl) and a hole concentration (NA = 5.87 × 1018 cm−3). The novel hetero-system CrFeO3/TiO2 showed improved efficiency by 47% compared to CrFeO3. An optimal mass ratio CrFeO3/TiO2 (25%/75%) gives to a Ni2+ reduction of 88% at pH ∼ 7.2 within 4 h irradiation for an initial Ni2+ concentration of 15 mg/L. A first order kinetic was found from the Ni2+ photoreduction with a half photocatalytic life of 61 min−1 and a higher photodegradation under sunlight is obtained. More interestingly, the photocatalyst showed a good stability and recyclability after four runs.

In the last years, the development of photocatalysts has gained a growing interest in the photoelectrochemical conversion. Here, we report a hetero-junction organic/inorganic (Polyaniline (PANI)) on n type Silicon substrate prepared by electrophoretic deposition (EPD). ZnO nanorods (NRs) are grown by chemical bath deposition (CBD) on seed layer of ZnO prepared by dip coating onto the PANI layer. The relief and morphological properties are investigated by both atomic force microscope (AFM) and scanning electron microscopy (SEM). The forbidden bands (Eg) of 1.12 and 3.26 eV are obtained for PANI and ZnONRS respectively. The optical and dielectric constants are determined by the diffuse reflectance where the extinction coefficient (k), the refractive index (n), optical conductivity, dissipation factor and relaxation time are extracted. The semi conductivity is highlighted by the capacitance measurement; a flat band potential (Efb = 0.541 V) for ZnONRs-PANI is deduced from the Mott-Schottky plot. The contributions of the bulk and grain boundaries of the electrode are evidenced from the electrochemical impedance spectroscopy (EIS). The as-fabricated samples show improved photoactivity compared to PANI and ZnONRs. Indeed, the hetero-junction exhibits a high stability and recyclability for the photodegradation of Orange II (OII) after six cycling runs. The current research offers a new understanding of designing a high performance of the photocatalyst under solar light based on PANI for the wastewater treatment.

The widespread occurrence of drugs in the aquatic environment has raised concerns over the last decades about the mechanisms to be used to remove these emerging contaminants because of their harmful effects on the water quality and human health. This current research was aimed to explore the preparation of an activated carbon from kernel oil treatment residues of Argania Spinosa for the removal of amoxicillin (AMX) from water. The conditions for synthesizing the activated carbon (AC-RS) were used: an impregnation weight ratio of char to KOH 1:1 at activation temperature of 800 °C for 1 h of activation time, which gave a BET surface area and total pore volume of 1618 m2 g−1 and 0.763 cm3 g−1, respectively. The effect of AMX/AC-RS interactions as well as the operating conditions (time, solution pH, initial concentration, and temperature) on the adsorption capacity was also studied. The adsorption of AMX onto AC-RS, with maximum adsorption capacity of 303.03 mg g−1, is much higher compared to several adsorbents reported in the literature. The high amount of AMX absorbed by AC-RS at pH 6 mainly results from the adsorption sites involved in the electrostatic attraction force, π-π hydrophobic interaction, and hydrogen bonding. The regeneration study ascertained the fact that AC-RS was reusable even after four consecutive cycles and the efficiency remains higher than 70%. Therefore, the optimized batch parameters were employed for the AMX removal in real wastewater, a percentage of 77.2% was obtained.

Nitrogenous disinfection by-products (N-DBPs) in chlorinated drinking water are receiving increasing attention due to their elevated toxicities. An effective strategy to control N-DBP formation is to reduce their nitrogenous precursors (amino acids) before disinfection. This work was undertaken to study free amino acid l-tyrosine adsorption onto two activated carbons synthesized from date pits. The amino acid is plentiful in low-molecular weight algal organic matter, which helps the formation of nitrogenous and carbonaceous disinfection by-products during water treatment. The equilibrium adsorption of l-tyrosine was studied on well-characterized activated carbons prepared by KOH (ACK) and ZnCl2 (ACZ) activation, possessing textural properties evaluated by SEM analysis, N2 adsorption–desorption isotherms and FT-IR spectroscopy. Batch experiments were conducted to determine the activated carbons’ adsorption capacities. The effect of contact time, initial adsorbate concentration, solution pH, and temperature were studied. The Langmuir model gave the best fit for the experimental data of l-tyrosine with a maximum monolayer adsorption capacity of 178.57 and 102.04 mg·g−1 on ACK and ACZ, respectively. Thermodynamic parameters ΔG°, ΔH° and ΔS° were also estimated for the adsorption study. The adsorption was spontaneous and exothermic, and involved physisorption.

Over the last decade, there is a growing interest in developing visible light active polymer conductors. Herein, the visible-light-driven photocatalytic activity of Pani-ZnO nanoparticles were fabricated by in situ polymerization. The adsorption and photo-electrochemical properties were evaluated for the photodegradation of two dyes namely Orange G (OG) and methyl Orange (MO) at different pHs. The synthetized polymers were characterized by scanning electron microcrospy (SEM) and diffuse reflectance. To provide further insights into the synergistic effect, the optical and dielectric constants allow to calculate the refractive index, optical conductivity, extinction coefficient (k), dissipation factor (tan δ) and relaxation time (τ). These properties were exploited to study the charge transfer and electronic properties of Pani-ZnO nanoparticles. The as-fabricated samples showed improved photoactivity compared to Pani alone. The optimal ZnONPs ratio (30 wt%. Pani-ZnO 30%) gives the higher degradation under sunlight, and the hetero-system exhibits high stability and recyclability for the dye oxidation. The current research offers a new understanding of designing high performance of Pani based photocatalysts for the water treatment.

The hetero-system CoAl2O4/ZnO was successfully used for the photo-degradation of Congo Red (CR), a hazardous and recalcitrant dye. The spinel was prepared by nitrate route and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermal analysis (TG). The electrical conductivity augments exponentially with the inverse of absolute temperature and activation energy of 0.19 eV was computed. n-type conduction is evidenced from the anodic photocurrent at the semiconductor/electrolyte junction, thus improving the separation of electron /hole (e-/h+) pairs by the interfacial electric field. The quenching experiments were carried and the results demonstrate that the radical O2•- is the responsible active specie for the CR photooxidation. The solar photocatalysis over the hetero-system CoAl2O4/ZnO exhibits an increased performance in the CR degradation due to ZnO activation by the UVA part of the solar light. An elimination conversion of 97% was obtained after 4 h at room temperature for a CR concentration of 20 mg/L. The TOC analysis (66.9%) indicates that the dye CR is effectively mineralized on the hetero-system upon solar light. The kinetic indicates that the Langmuir-Hinshelwood (L-H) model is well adapted to the experimental data. A first order kinetic was found from the photo oxidation with a photocatalytic half-life of 29 min.

The objective of this work is to investigate the optical and dielectric properties of the synthetized cobalt aluminate (CoAl2O4) by chemical route using nitrates as reagents. The X-ray diffraction shows a single spinel phase with a good crystallinity. The diffuse reflectance spectrum R (λ) recorded in the range (200–900 nm) enable us to calculate the refractive index n (λ), optical conductivity (σopt), extinction coefficient (k), dissipation factor (tan δ) and relaxation time (τ). The optical gap (Eg = 1.83 eV), was evaluated and confirmed by several methods. The n-type conductivity is evidenced from the capacitance-potential plots, which leads to flat band potential of -0.43 VSCE and an electron density of 1.44 × 1017 cm−3. As application, the photo-degradation of Congo Red (CR) a persistent and hazardous dye was successfully realized, yielding a depollution parentage of 94 % within 240 min for an initial concentration of 10 mg L−1.