This paper presents a comprehensive literature review of different characteristics of greywater (GW) and current treatment methods. GW is domestic wastewater excluding toilet waste and can be classified as either low-load GW (excluding kitchen and laundry GW) or high-load GW (including kitchen and/or laundry). This review provides information on the quantity of GW produced, its constituents (macro and micro), existing guidelines for wastewater reuse, current treatment methods (from storage to disinfection) as well as related costs and environmental impacts. Moreover some successful examples from various countries around the world are examined. The current preferred treatments for GW use physical and biological/natural systems. Recently, chemical systems like coagulation, adsorption and advanced oxidation processes (AOPs) have been considered and have been successful for low to moderate strength GW. The presence of xenobiotic organic compounds (XOC), which are hazardous micropollutants in GW, is emphasised. Since conventional treatments are not efficient at removing XOC, it is recommended that future studies look at chemical treatment, especially AOPs that have been found to be successful at mineralising recalcitrant organic compounds in wastewater.
of 2600 Wh kg −1 and are recognized as one of high energy density storage devices for practical applications. In LSBs the cathode material is mainly sulfur, which is abundantly available, low cost, environmentally friendly and has high theoretical capacity of 1675 mAh g −1 . [1][2][3][4][5][6] However, the challenging issues associated with sulfur-based cathodes are: 1) the low electrical conductivity of sulfur, 2) the dissolution and shuttling effects of lithium polysulfides (LiPs), and 3) large volume variations during charge/discharge cycles. These bring about low efficiency, poor cycling stability, self-discharge phenomena, and ultimately degradation of the electrode material, all of which currently limit the potential commercialization of LSBs. These drawbacks, especially the difficulty to confine LiPs are the current research priorities in the field of LSBs. [1,7,8] To overcome these problems, a vast amount of research has been carried out in the last decade. The encapsulation of sulfur in a conductive carbon host can effectively improve the electrical conductivity of sulfur. Moreover, carbon offers a physical barrier that encapsulates the LiP intermediates. [9][10][11][12] Nevertheless, such weak physical confinement is not enough to suppress the eventual diffusion of LiPs over time. [13] Due to the polar nature of LiPs, the strategies involving functional polar substrates as Lithium-sulfur batteries (LSBs) are a class of new-generation rechargeable high-energy-density batteries. However, the persisting issue of lithium polysulfides (LiPs) dissolution and the shuttling effect that impedes the efficiency of LSBs are challenging to resolve. Herein a general synthesis of highly dispersed pyrrhotite Fe 1−x S nanoparticles embedded in hierarchically porous nitrogen-doped carbon spheres (Fe 1−x S-NC) is proposed.Fe 1−x S-NC has a high specific surface area (627 m 2 g −1 ), large pore volume (0.41 cm 3 g −1 ), and enhanced adsorption and electrocatalytic transition toward LiPs. Furthermore, in situ generated large mesoporous pores within carbon spheres can accommodate high sulfur loading of up to 75%, and sustain volume variations during charge/discharge cycles as well as improve ionic/mass transfer. The exceptional adsorption properties of Fe 1−x S-NC for LiPs are predicted theoretically and confirmed experimentally. Subsequently, the electrocatalytic activity of Fe 1−x S-NC is thoroughly verified. The results confirm Fe 1−x S-NC is a highly efficient nanoreactor for sulfur loading. Consequently, the Fe 1−x S-NC nano reactor performs extremely well as a cathodic material for LSBs, exhibiting a high initial capacity of 1070 mAh g −1 with nearly no capacity loss after 200 cycles at 0.5 C. Furthermore, the resulting LSBs display remarkably enhanced rate capability and cyclability even at a high sulfur loading of 8.14 mg cm −2 .
Nowadays the development of submicroscale products of specific size and morphology that feature a high surface area to volume ratio, well-developed and accessible porosity for adsorbates and reactants, and are non-toxic, biocompatible, thermally stable and suitable as synergetic supports for precious metal catalysts is of great importance for many advanced applications. Complex porous non-silica metal oxide submicrospheres constitute an important class of materials that fulfill all these qualities and in addition, they are relatively easy to synthesize. This review presents a comprehensive appraisal of the methods used for the synthesis of a wide range of porous non-silica metal oxide particles of spherical morphology such as porous solid spheres, core-shell and yolk-shell particles as well as single-shell and multi-shell particles. In particular, hydrothermal and low temperature solution precipitation methods, which both include various structure developing strategies such as hard templating, soft templating, hydrolysis, or those taking advantage of Ostwald ripening and the Kirkendall effect, are reviewed. In addition, a critical assessment of the effects of different experimental parameters such as reaction time, reaction temperature, calcination, pH and the type of reactants and solvents on the structure of the final products is presented. Finally, the practical usefulness of complex porous non-silica metal oxide submicrospheres in sensing, catalysis, biomedical, environmental and energy-related applications is presented.
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