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 (Kphoto) 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.

Computational DFT study of magnetite/graphene oxide nanoadsorbent: Interfacial chemical behavior and remediation performance of heavy metal hydrates from aqueous system.

Herein, magnetite/graphene oxide hybrid (MGO) was facilely synthesized and analyzed by various techniques such as X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, Brunauer, Emmett, and Teller surface area analyzer, and Raman spectroscopy. A computational density functional theory (DFT) has been applied for the first time to determine the removal mechanism of zinc (Zn2+ ), nickel (Ni2+ ), and chromium (Cr6+ ) hydrates onto the prepared MGO. The adsorption binding energy and geometries of the metal hydrates with oxygen functional group (i.e., hydroxyl, epoxide, carboxylic, carbonyl groups, and magnetite on the MGO surface) were estimated. The complexes configurations comprised via sitting the metal ion perpendicular and above the MGO surface. The zinc hydrate portended to bind more strongly than Ni2+ and Cr6+ . Zinc hydrate is favorable to coordinate with hydroxyl and carboxylic group than the other functional groups. The pseudo-second-order kinetic and Langmuir isotherm models are well convenient for kinetics and isotherm sorption process, respectively. The results determined that the sorption of heavy metals by nanostructure MGO was observed in the following order: zinc > nickel > chromium as revealed by the DFT computations. The maximum adsorption capacity of Zn2+ , Ni2+ , and Cr6+ was 333, 250, and 200 mg/g, respectively. Thermodynamic constants depicted that the sorption process is naturally instantaneous and exothermic. The calculated predicted results are fitted with the experimental results. PRACTITIONER POINTS: Combination of MGO with DFT calculations in the sorption of Zn, Ni, and Cr hydrates. MGO applied on the removal of Zn+2 , Ni+2 , and Cr+6 with high sorption capacity. DFT calculations revealed that Zn hydrate is more favorably adsorbed than others. DFT calculations proved that ZnOH is favorable to coordinate with OH and COOH groups. DFT calculation offers guidance on the mechanism of coordination of heavy metals.