Low temperature one-pot synthesis of Cu-doped ZnO/Al2O3 composite by a facile rout for rapid methyl orange degradation

Preparation and characterization of a novel cobalt-substitution cadmium aluminate spinel for the photodegradation of azo dye pollutants

Modern-year organic contaminants have been highly observed in ecosystems since they are not removed entirely and remain dangerous. Semiconductor binary oxide photocatalysts have been well accredited as capable technology for ecological contaminants degradation in the existence of visible irradiation. In this research, novel Co ions doped CdAl₂O₄ materials were fabricated by a facile co-precipitation approach. The fabricated pure and Co-doped CdAl₂O₄ exhibited the typical peaks of CdAl₂O₄ with the E_g of 3.66, 3.24, 2.57, and 2.41 eV respectively. The HR-TEM microstructures revealed that the Co (0.075 M) doped CdAl₂O₄ has rod-like morphology, and some places are spherical with particle sizes reaching 21 nm. The PL peaks of the Co (0.075 M)-CdAl₂O₄ are much lesser than that of the other dopant and pure CdAl₂O₄, representing much more effectual separation of generated e^- and h⁺ at the interface which in fact outcomes in superior expected photodegradation behaviours. The Co (0.075 M)-CdAl₂O₄ catalyst demonstrated the highest performances of 92 and 94% toward the degradation of both dyes, respectively, owing to the lowest e^- and h⁺ recombination rate. The Co (0.075 M) doped CdAl₂O₄ photocatalyst revealed outstanding reusability and stability under visible irradiation, retaining the performance of about 83 and 86% after the fifth consecutive run of BB and BG elimination. A probable photodegradation mechanism of Co (0.075 M) doped CdAl₂O₄ was suggested since the photoexcited h⁺, OH^- and O₂^- species contributed to the removal process, and that was affirmed by the scavenging test and ESR analysis. This research offers new ways to improve the photodegradation performance of the Co-doped CdAl₂O₄ catalyst that will be employed in pharmaceutical applications and wastewater treatment.

Photocatalysis for Organic Wastewater Treatment: From the Basis to Current Challenges for Society

Organic pollutants such as dyes, antibiotics, analgesics, herbicides, pesticides, and stimulants become major sources of water pollution. Several treatments such as absorptions, coagulation, filtration, and oxidations were introduced and experimentally carried out to overcome these problems. Nowadays, an advanced technique by photocatalytic degradation attracts the attention of most researchers due to its interesting and promising mechanism that allows spontaneous and non-spontaneous reactions as they utilized light energy to initiate the reaction. However, only a few numbers of photocatalysts reported were able to completely degrade organic pollutants. In the past decade, the number of preparation techniques of photocatalyst such as doping, morphology manipulation, metal loading, and coupling heterojunction were studied and tested. Thus, in this paper, we reviewed details on the fundamentals, common photocatalyst preparation for coupling heterojunction, morphological effect, and photocatalyst’s characterization techniques. The important variables such as catalyst dosage, pH, and initial concentration of sample pollution, irradiation time by light, temperature system, durability, and stability of the catalyst that potentially affect the efficiency of the process were also discussed. Overall, this paper offers an in-depth perspective of photocatalytic degradation of sample pollutions and its future direction.

Preparation of solar-enhanced AlZnO@carbon nano-substrates for remediation of textile wastewaters

Photoactive aluminum doped ZnO (AlZnO) was synthesized by sol-gel method. After that, AlZnO photocatalyst was deposited on five carbon-based materials (CBMs) using ultrasonic route followed by solid-state mixing using ball mill. The CBMs used were polyaniline (PANI), carbon nitride (CN), carbon nanotubes (CNT), graphene (G), and carbon nanofibers (CNF). The crystal phases, elemental compositions, morphological, and optical properties of the AlZnO@CBMs composites were investigated. Experimental results revealed that two of AlZnO@CBMs composites exhibited superior bleaching efficiency (100% removal) and photocatalytic stability (three cycles) for 50 μmol/L Methylene Blue (MB) contaminated water after 60 min irradiation in visible light at pH 6.5, 0.7% H₂O₂, and 5 g/L inorganic salts. Under optimum conditions, AlZnO@CBMs nanocomposites were employed for the treatment of mixed dyestuffs composed of MB, Methyl Orange (MO), Astrazone Blue FRR (BB 69), and Rhodamine B (RhB) dyes under dark, ultraviolet, visible, and direct sunlight. For mixed dyestuffs, the AlZnO@G achieved the highest dye sorption capacity (60.91 μmol dye stuffs/g) with kinetic rate 8.22 × 10^-3 min^-1 in 90 min via multi-layer physisorption (Freundlich isotherm) on graphene sheet. In additions, AlZnO@CN offered the highest photo-kinetic rate (K_photo) of ~54.1 × 10^-3 min^-1 (93.8% after 60 min) under direct sunlight. Furthermore, the selective radical trapping experiment confirmed that the holes and oxidative superoxide radicals are crucial on dyes photodegradation pathway. Owing to their superior performance, AlZnO@G and AlZnO@CN nanocomposites can offer an effective in-situ solar-assisted adsorption/photocatalytic remediation of textile wastewater effluents.

Facile sonochemical-assisted synthesis of Cu/ZnO/Al2O3 nanocomposites under vacuum: Optical and photocatalytic studies

This paper reports on the synthesis of Cu/ZnO/Al₂O₃ nanocomposites via a facile sonochemical-assisted approach using new starting reactants. This study was conducted to synthesis and photocatalytic evaluation of the Cu/ZnO/Al₂O₃ nanocomposite in vacuum conditions. The XRD results showed that Cu/ZnO/Al₂O₃ and CuO/ZnO/Al₂O₃ nanocomposites could be obtained after annealing at 600 °C for 3 h in vacuum conditions and in the air, respectively. The effects of Cu:Zn:Al ratio, ultrasonic irradiation, power, time, and capping agent on the product composition and morphology were also studied. Finally, the efficiency of various as-synthesized Cu/ZnO/Al₂O₃ nanocomposites for decolorization of methylene blue were evaluated. According to the results, using ultrasonic irradiation and annealing under vacuum, the efficiency is improved up to 100%. Because in this situation Cu/Cu₂O/ZnO/Al₂O₃ is formed, which has a better absorption (due to Cu₂O) and conductivity (due to Cu) than CuO/ZnO/Al₂O₃ for the photocatalysis process.