Graphene supported heterogeneous catalysts: An overview

Energy harvesting is a topic of intense interest that aims to convert ambient forms of energy such as mechanical motion, light and heat, which are otherwise wasted, into useful energy. In many cases the energy harvester or nanogenerator converts motion, heat or light into electrical energy, which is subsequently rectified and stored within capacitors for applications such as wireless and self-powered sensors or low-power electronics. This review covers the new and emerging area that aims to directly couple energy harvesting materials and devices with electro-chemical systems. The harvesting approaches to be covered include pyroelectric, piezoelectric, triboelectric, flexoelectric, thermoelectric and photovoltaic effects. These are used to influence a variety of electro-chemical systems such as applications related to water splitting, catalysis, corrosion protection, degradation of pollutants, disinfection of bacteria and material synthesis. Comparisons are made between the range harvesting approaches and the modes of operation are described. Future directions for the development of electro-chemical harvesting systems are highlighted and the potential for new applications and hybrid approaches are discussed.

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Control of electro-chemical processes using energy harvesting materials and devices.

The goal of this work is to use the photo-catalyst NiO-ZnO doped onto nano zeolite X (NZX) with a p-n heterojunction semiconductor structure in the photo-catalytic degradation of Eriochrome Black T (EBT) and Methyl Orange (MO) under UV-light irradiation Nano-zeolite crystals were synthesized by hydrothermal crystallization Ion exchanging of the prepared Nano zeolite in an aqueous solution containing Ni(II) and Zn(II) cations and calcinations of the ion-exchanged material at 450 °C led to the formation of NiO-ZnO-NZX catalyst The samples were characterized by XRD, UV/vis-DRS, FT-IR, TEM and BET The composites exhibited significantly enhanced photo-degradation activity for the degradation of (EBT) and (MO) A synergistic effect of mixed p–type NiO and n–type ZnO oxides incorporated in NZX has been noticed on the photo-degradation process Several influencing process parameters, such as the NiO-ZnO ratio, pH, initial dyes concentrations, dosage of photo-catalyst, were also investigated The extent of degradation was estimated from the residual concentration by spectrophotometrically and it was confirmed by the reduction of chemical oxygen demand (COD)

Efficiently enhancing photocatalytic activity of NiO-ZnO doped onto nanozeoliteX by synergistic effects of p-n heterojunction, supporting and zeolite nanoparticles in photo-degradation of Eriochrome Black T and Methyl Orange

Reduced graphene oxide (RGO) on TiO2 for an improved photoelectrochemical (PEC) and photocatalytic activity

In this work, magnetic Fe2O3/TiO2 monoliths were successfully synthesized through nanocasting method followed by wet impregnation for the removal of remazol brilliant red X-3BS (RbX) dye and widely used pesticide (Fipronil). The activity of such catalyst combined with the photo-Fenton catalysis was assayed under the UV light irradiation. The effect of various parameters such as pH, catalyst dosage, H2O2 concentration, pollutant concentration and treatment time were also investigated. The optimal pH value (pH 3), H2O2 concentration (60 mM) and catalyst dosage (2 g/L) leads the higher degradation efficiency of RbX (90.57%) within 180 min time. Whereas, it has been found that fipronil exhibited highest degradation efficiency of 88.71% at pH 3 using 10 mM of H2O2 concentration, 1.5 g/L of the catalyst in 120 min time. The Fe2O3/TiO2 monoliths showed remarkable photocatalytic activity as compared to Fe2O3 and TiO2 monoliths. This is attributed to the fact that TiO2 combined with Fe2O3 leads to the effective separation of photo excited carriers which result better degradation efficiency. The kinetics of RbX and fipronil degradation by supported Fe2O3/TiO2 monoliths followed the first-order mechanism. Moreover, synthesized monoliths showed excellent stability and reusability for four cycles of degradation. In addition, the monolithic Fe2O3/TiO2 photo-catalyst can be easier to recover after the treatment process which is more relevant to the practical application point of view.

Synthesis of Fe2O3/TiO2 monoliths for the enhanced degradation of industrial dye and pesticide via photo-Fenton catalysis

Several studies have reported the adverse effects of recalcitrant compounds and emerging contaminants present in industrial effluents, which are not degradable by ordinary biological treatment Many of these compounds are likely to accumulate in living organisms through the lipid layer At concentrations above the limits of biological tolerance, these compounds can be harmful to the ecosystem and may even reach humans through food chain biomagnification In this regard, advanced oxidation processes (AOPs) represent an effective alternative for the removal of the pollutants This study focused on the AOP involving the use of ultraviolet radiation in homogeneous and heterogeneous systems Based on the literature review, comparisons between natural and artificial light were established, approaching photoreactors constructive and operational characteristics We concluded that the high availability of solar power in Brazil would make the implementation of the AOP using natural solar radiation for the decontamination of effluents feasible, thereby contributing to clean production and biodiversity conservation This will serve as an important tool for the enforcement of environmental responsibility among public and private institutions

Solar energy for wastewater treatment: review of international technologies and their applicability in Brazil

Evaluation of photocatalytic activities of supported catalysts on NaX zeolite or activated charcoal.

Synthesis and characterization of new NaX zeolite-supported Nb, Zn, and Fe photocatalysts activated by visible radiation for application in wastewater treatment

Fernanda F. Brites-Nóbrega

Papers

Solar energy for wastewater treatment: review of international technologies and their applicability in Brazil

Evaluation of photocatalytic activities of supported catalysts on NaX zeolite or activated charcoal.

Synthesis and characterization of new NaX zeolite-supported Nb, Zn, and Fe photocatalysts activated by visible radiation for application in wastewater treatment