Present applications of titanium dioxide for the photocatalytic removal of pollutants from water: A review.

Recent developments of two-dimensional graphene-based composites in visible-light photocatalysis for eliminating persistent organic pollutants from wastewater

Graphene coupled TiO2 photocatalysts for environmental applications: A review.

Aims Zinc oxide nanoparticles (ZnONPs) were successfully synthesized using the culture filtrate of the endophytic fungus Alternaria tenuissima as a rapid, eco-friendly and cost-effective method. Methods and results The rapid synthesis of ZnONPs was completed after 20 min as confirmed by UV-Vis spectroscopy. The synthesized ZnONPs showed a single-phase crystalline structure. Dynamic light scattering analysis showed that the synthesized ZnONPs were monodispersed and the recorded polydispersity index value was 0·311. Zeta potential value of -23·92 mV indicated the high stability of ZnONPs. Transmission electron microscope revealed the spherical shape and the mean particle size was 15.45 nm. Functional groups present in the prepared samples of ZnONPs were confirmed by Fourier transform infrared spectroscopy. Additionally, the biological activities of in vitro antimicrobial, anticancer, antioxidant as well as the photocatalytic activities were evaluated. ZnONPs showed broad spectrum of antimicrobial potential against all the tested plant and human pathogens. Based on the MTT assay, ZnONPs inhibited the proliferation of normal human melanocytes, human breast and liver cancer cell lines with IC50 concentrations of 55·76, 18·02 and 16·87 µg ml-1 . ZnONPs exhibited promising antioxidant potential with 50% inhibitory concentration of 102·13 µg ml-1 . Moreover, ZnONPs showed efficient degradation of methylene blue dye. Conclusions The synthesized ZnONPs showed promising activities that can be better explored in the near future for many medical, agricultural and industrial applications. Significance and impact of the study This study suggests a new and alternate approach with the excellent biotechnological potentiality for the production of ZnONPs which could open up the way for the industrial manufacture of nanoparticles using microbial platforms.

Biosynthesis of zinc oxide nanoparticles with antimicrobial, anticancer, antioxidant and photocatalytic activities by the endophytic Alternaria tenuissima

Increased population and industrialization generate a large number of organic pollutants that create problems on the planet earth. The level of freshwater is reducing which has pushed the society to reuse/recycle wastewater. Eco-friendly and economically sound treatment of industrial wastewater has attracted global attention and hence is a thrust area of research. Organic compounds rich wastewater can be used to generate bioenergy and value-added products from the resource recovery point of view. Wastewater treatment(s) can be used to trap energy from industrial effluents in form of biofuel, bioenergy and biogas. Recovered products can be used in various ways such as recovered nutrients for (bio)fertilizer production and algal biomass for bioplastic production. Microbial electrochemical technology is a promising approach for resource recovery. This review article aims to present and discuss trends and scientific developments about recovery of value-added products from dye industry effluent. It also provides state-of-art technical information about technologies for remediation of pollutants from dye industry effluent with emphasis on nanotechnological approaches and microbial electrochemical technologies (METs). It narrates literature on classification and properties of dyes, effects of dye pollutants on environment and human health and factors affecting degradation of dyes. Generation of bioenergy and recovery of valuables from dye industrial wastewater along with challenges and perspectives of this research area have been covered.

Trends in dye industry effluent treatment and recovery of value added products

We report the synthesis of TiO2/Graphene oxide nanocomposites (2%, 4%, 6% and 8%) by liquid phase deposition of titania on graphene oxide (GO) nanosheets. This chemical method of synthesis was used due to hydrophobic/hydrophilic incompatibility of GO with metal oxides. The fabricated TiO2/GO nanocomposites were successfully characterized using various diffraction, electron microscopy and spectroscopic techniques i.e. X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Energy-Dispersive X-Ray (EDX), Ultra-Violet Visible, Diffuse Reflectance Spectroscopy (DRS) and Fourier Transform Infra Red (FTIR). Photocatalytic activity against methylene blue dye and ciprofloxacin was carried out by the synthesized nanocomposites under sun light spectrum. Results were revealed that average crystallite size (12.42 nm, and 12.50 nm) was observed for the synthesized pure TiO2 and TiO2/GO (8%) nanocomposites respectively with crystalline nature and spherical morphology. Moreover, synthesized TiO2/GO (8%) nanocomposites were found to have larger surface area (91.25 m2g-1) and narrow energy band-gap values (2.47 eV) than that of pure TiO2 (55.93 m2g-1 and 3.06 eV) respectively. Furthermore, the TiO2/GO (8%) nanocomposites exhibited fastest and highest rate of photocatalytic degradation of methylene blue among all composites (2%, 4%, and 6%) and pure TiO2 in much reduced period. Their excellent photocatalytic activity against synthetic dye and ciprofloxacin under the spectrum of visible region was attributed to thin two dimensional sheet support, larger surface area, narrow band gap, higher adsorption capacity and good electron acceptability of GO. Hence, the fabricated nanocomponents could be proved valuable photocatalytic system to safe our environs from the intimidations of toxic waste products produced by different industries.

Zunaira Arshad

Papers

Synthesis of TiO2/Graphene oxide nanocomposites for their enhanced photocatalytic activity against methylene blue dye and ciprofloxacin