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This study evaluated impact of untreated dye effluent on heavy metal uptake by Amaranthus cruentus L. under field condition. Amaranths grown for two consecutive dry seasons were irrigated with dye effluent concentrations of 0 (control) 10, 20, 30 and 40%. Effluent concentrations were analyzed for physico-chemical and heavy metal properties. The result showed that heavy metals taken up and accumulated in amaranths tissues increased significantly ( p ≤ 0.05) with dye effluent concentration. Heavy metals accumulated more in edible shoots than roots except chromium. Bioaccumulations of heavy metals in 2012 were in several folds higher than in 2011 dry season. In the second season, regardless of effluent sources, dye concentration of 20% gave the highest accumulations of Manganese (Mn), Iron (Fe) and Zinc (Zn) in the edible shoots. The highest accumulations of heavy metals were higher than 0.3 mg kg −1 allowable limits in vegetables by Food and Agricultural Organization/World Health Organization/Federal Environmental Protection Agency. Irrigation of vegetable with untreated dye effluent should be discouraged due to potential health risks on human and general contamination of the environment. [ABSTRACT FROM AUTHOR]

Graphene oxide can be used to store energy, as electrodes and purify industrial and domestic wastewater as photocatalysts and adsorbents because of its remarkable thermal, electrical, and chemical capabilities. Toward understanding graphene oxide (GO) based nanomaterials considering the background factors, the present review study investigated their characteristics, preparation methods, and characterization processes. The removal of contaminants from wastewater has recently been a focus of attention for materials based on GO. Progress in GO synthesis and surface modification has shown that they can be used to immobilize enzymes. It is possible to immobilize enzymes with varying characteristics on graphene-oxide-based substrates without sacrificing their functioning, thus developing a new environmental remediation platform utilizing nano biocatalysts. GO doping and co-doping with a variety of heterogeneous semiconductor-based metal oxides were included in a brief strategy for boosting GO efficiency. A high band-gap material was also explored as a possibility for immobilization, which shifts the absorption threshold to the visible range and increases photoactivity. For water treatment applications, graphene-based nanomaterials were used in Fenton reactions, photocatalysis, ozonation, photo electrocatalysis, photo-Fenton, and a combination of photon-Fenton and photocatalysis. Nanoparticles made from GO improved the efficiency of composite materials when used for their intended applications. As a result of the analysis, prospects and improvements are clear, especially when it comes to scaling up GO-based wastewater treatment technologies. [Display omitted] • Nano-based graphene oxide (GO) is useful in effective wastewater treatment. • To develop GO to treat wastewater, bottom-up and top-down approaches can be used. • Electro-chemical, mechanical, and surface properties of GO are pollutant traps. • GO plays an important role in adsorption-based water treatment systems. [ABSTRACT FROM AUTHOR]

A non-ligninolytic fungus Myrothecium sp. IMER1 and its bilirubin oxidase (BOX) were evaluated for their ability to decolorize an alkaline dye effluent. The strain was capable of decolorizing dye effluent at various concentrations of 20, 33.3, 50 and 66.7% (v/v) in the pH basic range of 9.5-10.0, but high dye effluent concentration in the medium resulted in low colour removal rate. The biomass production and BOX activity of Myrothecium sp. IMER1 were inhibited during decolorization. Spectra analyses of culture supernatants and colour changes in fungal cells suggested that dyes in the effluent were removed by Myrothecium sp. IMER1 mainly due to enzymatic reaction. Thus, biodegradation was the major dye decolorization mechanism, rather than inactive surface adsorption. BOX was able to decolorize dye effluent effectively over a pH range of 4-10, and maximum decolorization of dye effluent was observed at pH 7.0. In addition, colour removal efficiency was higher at neutral and alkaline pH than at acid pH. In the presence of 2,2-Azinobis (3-ethylbenzothiazolin-6-sulfonic acid) (ABTS) as a redox mediator, a marked increase was obtained in decolorization at the various pH values tested. The germination of Phaseolus mungo seeds was inhibited with dye effluent but not with the dye effluent treated by Myrothecium sp. IMER1 or BOX, indicating the less toxic nature of the treated dye effluent to the plants. Therefore, both this non-ligninolytic strain and its extracellular BOX will be potential candidates for wastewater treatment of dye effluents, especially alkaline dye effluents. [ABSTRACT FROM AUTHOR]