Plasma-deposition of α-FeOOH particles on biochar using a gliding arc discharge in humid air: a green and sustainable route for producing oxidation catalysts

Non-thermal atmospheric plasma of the gliding arc type was used as a tool for goethite-on-biochar hybrid material preparation. Biochars were first prepared by carbonizing raffia bamboo (the leafstalk of raffia palm) pith at 300 °C (BC3), 500 °C (BC5) and 700 °C (BC7). A suspension of each biochar in Fe²⁺ aqueous solution was then exposed to a plasma discharge burning in humid air. α-FeOOH particles were thus formed and spontaneously deposited on the biochar surface. In order to investigate the effect of plasma species on the support during goethite deposition, biochars were also treated with plasma in the absence of Fe²⁺ ions and then characterized. Results revealed a substantial hydroxylation and slight N-doping of biochar after plasma treatment. The prepared composite materials were tested in oxidative degradation of nitroresorcinol. The catalytic performances were in the order Fe-BC3 < Fe-BC7 < Fe-BC5 according to the abatement efficiency and half-time values obtained for each catalyst. This study establishes that waste biomass and atmospheric air can be simultaneously valorised for green production of heterogeneous catalysts.

Non-thermal atmospheric plasma of the gliding arc type was used as a tool for goethite-on-biochar hybrid material preparation.

Altering fiber density of cockscomb-like fibrous silica-titania catalysts for enhanced photodegradation of ibuprofen

Fibrous silica-titania (FST) catalysts were synthesized by microemulsion followed by silica seed-crystal crystallization methods under various molar ratios of toluene to water (T/W). The catalysts were characterized by XRD, UV-DRS, FESEM, TEM, AFM, N₂ adsorption-desorption, FTIR, and ESR. The results revealed that altering the T/W ratio affected the growth of the silica and titania and led to different size, fiber density, silica-titania structure, and number of hydroxyl groups, as well as oxygen vacancies in the FSTs, which altered their behavior toward subsequent application. Photodegradation of ibuprofen (IBP) are in the following order: FST(6:1) (90%) > FST(5:1) (84%) > FST(7:1) (79%) > commercial TiO₂ (67%). A kinetics study using Langmuir-Hinshelwood model illustrated that the photodegradation followed the pseudo-first-order and adsorption was the rate-limiting step. Optimization by response surface methodology (RSM) showed that the pH, initial concentration, and catalyst dosage were the remarkable parameters in photodegradation of IBP. The FST (6:1) maintained its photocatalytic activities for up to five cycles reaction without serious catalyst deactivation, and was also able to degrade other endocrine-disrupting chemicals, indicating its potential use for the treatment of those chemicals in wastewater.

Environmentally benign synthesis of CuInS2/ZnO heteronanorods: visible light activated photocatalysis of organic pollutant/bacteria and study of its mechanism

Due to its high light absorption coefficient and appropriate bandgap, CuInS₂ (CIS) has been receiving much attention as an absorber material for thin film solar cells and also as a visible light photocatalyst. Herein we present heterostructured CIS/ZnO nanorods (NRs) in an attempt to enhance light absorption and facilitate charge separation/transfer in the photocatalysis system. CIS nanoparticles (NPs) were directly deposited on ZnO nanorod arrays (NRAs) to fabricate heterostructured CIS/ZnO NRAs using an environmentally benign, non-hydrazine solution reaction. These heterostructured NRAs are immobilized on FTO glass, which has additional merits of recyclability and bias-applicability. The ideal type-II band structure of CIS/ZnO enables efficient charge separation/transfer, which is confirmed by PL (photoluminescence) decay measurements. Also, the 1D-ZnO NR structure facilitates fast charge transfer along with enhancing light absorption via light scattering. These synergistic effects improved the photocatalytic activity in both organic dye and bacteria decomposition. The photodecomposition efficiency was further enhanced with an aid of external bias. The underlying photocatalytic mechanism was also investigated through controlled experiments under various scavenging conditions. The results suggest that reactive oxygen species (ROS) formed by multistep reduction of O₂ play a main role in photocatalysis, while hole-induced photodecomposition is relatively deactivated due to the band structure of the heterostructures of CIS/ZnO.

Enhanced photodegradation of dyes and mixed dyes by heterogeneous mesoporous Co–Fe/Al2O3–MCM-41 nanocomposites: nanoparticles formation, semiconductor behavior and mesoporosity

Fabrication of mono and bimetallic nanoparticles by in situ sol–gel cum hydrothermal method for photo degradation of dyes and mixed dyes.

Interaction between copper and carbon nanotubes triggers their mutual role in the enhanced photodegradation of p-chloroaniline

Copper (Cu, 1–5 wt%) was loaded onto carbon nanotubes (CNTs) by a simple electrochemical method.

Synergistic interactions of Cu and N on surface altered amorphous TiO2 nanoparticles for enhanced photocatalytic oxidative desulfurization of dibenzothiophene

Amorphous TiO₂ (AT) nanoparticles were prepared by a simple sol–gel method and subsequent incorporation with 5–20 wt% copper via an electrochemical method in the presence of tetraethylammonium perchlorate gave an active CuO/TiO₂ (CAT) photocatalyst.

New insights into self-modification of mesoporous titania nanoparticles for enhanced photoactivity: effect of microwave power density on formation of oxygen vacancies and Ti3+ defects

Mesoporous titania nanoparticles (MTN) were successfully prepared by a microwave (MW)-assisted method under various power densities.