Heavy metals (copper and iron) and nutrients (nitrate and phosphate) removal from aqueous medium by microalgae Chlorella vulgaris and Scendesmus obliquus, and their biofilms.

Microalgae have been discovered as an environmental-friendly and cost-effective solution for heavy metal treatment issues. This study illustrated the bioremediation of two heavy metals (e.g. copper and iron) and nutrients (e.g. nitrate and phosphate) uptake by freshwater microalgae Chlorella vulgaris (C. vulgaris) and Scendesmus obliquus (S. obliquus), and their 50-50% mix culture under the suspension and biofilm conditions. After one week of culture in 1L Erlenmeyer flasks, under the Organization for Economic Co-operation and Development (OECD) guideline, various concentrations of copper and iron were added to the culture bioreactors and their concentrations changes were studied. The results obtained showed that C. vulgaris, S. obliquus, and mix culture removed 98.25-99.9%, 98.75-99.1%, and 98.61-99.9% of copper and 90.22-94.05%, 85.68-99.19%, and 91.67-97.85% of iron, respectively. The results suggested that copper has more toxicity effects than iron. C. vulgaris showed to be the most vulnerable among cultures. S. obliquus showed to be more resistant to copper and iron stress situations. Mix culture showed better efficiency in iron uptake. It also demonstrated that there is a limit to nitrate uptake. Increasing heavy metal concentrations may increase nutrient uptake as long as it doesn't reach a toxic amount. Also, biofilm structure showed an effective role in heavy metal resistance.

Recent Developments of Electrospinning-Based Photocatalysts in Degradation of Organic Pollutants: Principles and Strategies.

Electrospinning is a simple and cheap process for forming one-dimensional (1D) nanofibers with controllable size, morphology, and chemistry. Besides these, the ultrahigh surface area with industrialization capability has attracted extensive interest in the research community. On the other hand, a photocatalytic process is a promising method for degrading organic pollutants that cannot be removed by conventional wastewater treatment. This review focuses on the recent progress of electrospun nanofibers for the photocatalytic degradation of water pollutants. The linkage between the electrospinning technique and the photocatalytic process is classified into two main categories: (1) polymeric electrospun nanofibers as a sacrificed template to form 1D photocatalysts and (2) polymeric electrospun nanofibers as a carrier of photocatalyst materials. We have thoroughly discussed the principles and fundamental issues of electrospinning as well as two main strategies to design and fabricate nanofiber-based photocatalysts for the ideal photodegradation of organics pollutants. The results of data mapping using VOSviewer demonstrated the recent trend and the importance of this field among researchers and engineers. Moreover, we have elaborated on the limitations and potential benefits of the two categories of electrospinning-based photocatalyst fabrication and practical application that will open new directions for future research.

Well-designed Ag/ZnO/3D graphene structure for dye removal: Adsorption, photocatalysis and physical separation capabilities.

In this research, adsorption and photocatalytic degradation process were utilized to remove organic dye from wastewater. To accomplish that, a newly-designed ternary nanostructure based on Ag nanoparticles/ZnO nanorods/three-dimensional graphene network (Ag NPs/ZnO NRs/3DG) was prepared using a combined hydrothermal-photodeposition method. The three-dimensional structure of graphene hydrogel as a support for growth of ZnO nanorods was characterized using field emission scanning electron microscopy (FESEM). In addition, diameter of silver nanoparticles grown on the ZnO nanorods with the average aspect ratio of 5 was determined in the range of 30-80 nm by using transmission electron microscopy (TEM). The X-ray diffraction (XRD) pattern was revealed hexagonal Wurtzite structure of ZnO nanorods and the (1 1 1) lattice plane of the face-centered cubic (FCC) of the silver nanoparticles. The dye adsorption capacity of the synthesized 3DG was evaluated at about 300 mg/g using kinetic study. The photocatalytic dye degradation under both UV and visible light irradiation exhibited an enhanced activity of the prepared ternary Ag/ZnO/3DG sample in comparison to ZnO/3DG and 3DG structures. Different charge-carrier scavengers were utilized to elucidate the synergistic effect of adsorption and visible-light photocatalytic degradation mechanism for dye removal. The facile photocatalyst recovery as well as the high elimination rate of dye is promising for future applications such as efficient removal of organic contaminants from industrial wastewater under solar irradiation.

Group 6 transition metal dichalcogenide nanomaterials: synthesis, applications and future perspectives.

Group 6 transition metal dichalcogenides (G6-TMDs), most notably MoS2, MoSe2, MoTe2, WS2 and WSe2, constitute an important class of materials with a layered crystal structure. Various types of G6-TMD nanomaterials, such as nanosheets, nanotubes and quantum dot nano-objects and flower-like nanostructures, have been synthesized. High thermodynamic stability under ambient conditions, even in atomically thin form, made nanosheets of these inorganic semiconductors a valuable asset in the existing library of two-dimensional (2D) materials, along with the well-known semimetallic graphene and insulating hexagonal boron nitride. G6-TMDs generally possess an appropriate bandgap (1-2 eV) which is tunable by size and dimensionality and changes from indirect to direct in monolayer nanosheets, intriguing for (opto)electronic, sensing, and solar energy harvesting applications. Moreover, rich intercalation chemistry and abundance of catalytically active edge sites make them promising for fabrication of novel energy storage devices and advanced catalysts. In this review, we provide an overview on all aspects of the basic science, physicochemical properties and characterization techniques as well as all existing production methods and applications of G6-TMD nanomaterials in a comprehensive yet concise treatment. Particular emphasis is placed on establishing a linkage between the features of production methods and the specific needs of rapidly growing applications of G6-TMDs to develop a production-application selection guide. Based on this selection guide, a framework is suggested for future research on how to bridge existing knowledge gaps and improve current production methods towards technological application of G6-TMD nanomaterials.