Optimising water and phosphorus management in the urban environmental sanitation system of Hanoi, Vietnam

Many areas in the world face clean water scarcity problems and phosphorus reserves are likely to be depleted in the near future. Still, a large amount of clean water is used to transport excreta through sewer systems. Most of the wastewater generated worldwide is discharged untreated into aquatic systems and leads to water pollution and loss of valuable nutrients. In Hanoi, Vietnam's capital city, high population and economic growth as well as industrialisation have led to a decrease in groundwater level and to serious river and lake pollution. A probabilistic model, simulating the impact of measures on groundwater abstraction and nutrient recovery, was used to determine the impact of policy changes in Hanoi. The results obtained reveal that harmonising environmental sanitation and agricultural systems with one another will considerably increase nutrient recovery for food production, lower expenditure for artificial fertilisers and reduce the nutrient load into the environment. The model can be applied in urban areas of developing countries to assist in the design of environmental sanitation concepts.     

Comparisons of fish meat extract desalination by electrodialysis using different configurations of membrane stack

The desalination of fish meat extract was performed via electrodialysis based on different membrane stack configurations (i.e., conventional electrodialysis or packed-bed electrodialysis) at a constant current. The salt removal and brix change showed that the diluted fish meat extract could be effectively desalted using electrodialysis, while the mostly nutritional ingredients remained in the dilution. Compared with the conventional electrodialysis (ED), a lower membrane stack potential meant lower energy consumption and higher current efficiency for the same salt removal in the packed-bed electrodialysis (PBED). The results indicated that the PBED might be more suitable for use in the fish meat extract desalination due to the effects of ion exchange resins in enhancing ion electromigration and mitigating membrane fouling.     

Inverted mesa-type quartz crystal resonators fabricated by deep-reactive ion etching

In this letter, we present experimental data showing Q change versus thickness for a quartz-crystal resonator fabricated with deep-reactive ion etching. Measurements show that Q increases as etch depth increases, and further that Q can be optimized as a function of etch depth and diameter of the resonator.     

Influence of annealing treatments on the essential work of fracture of biaxially drawn poly(ethylene terephthalate)

The biaxial sequential stretching process of poly(ethylene terephthalate) produces films with a fibrillar microstructure in which fibrils are parallel to the transverse extrusion direction. The mechanical properties of such films are strongly anisotropic due to both the orientation of crystallites and the properties of the intrafibrillar and interfibrillar amorphous phases. The idea is to modulate the properties of the amorphous phase without altering the fibrillar structure by annealing treatments. The morphology (crystallinity and orientation of the crystalline phase) of the annealed films is characterized and their mechanical properties (tensile tests and essential work of fracture) are tested in the longitudinal direction (parallel to the micro fibrils) and in the transverse direction (perpendicular to the micro fibrils). The crystalline phase orientation is the key parameter governing modulus anisotropy. Concerning crack propagation, annealing treatments lead to opposite evolution of the specific essential work of fracture parameter (w_e) in the longitudinal and transverse directions. Thus, it is possible to erase fracture propagation anisotropy through an adequate annealing treatment. Copyright © 2012 Society of Chemical Industry     

“Green” biocomposites based on cellulose diacetate and regenerated cellulose microfibers: Effect of plasticizer content on morphology and mechanical properties

In the present study, a new process route was developed for cellulose diacetate (CDA) based biocomposites by melt processing. The new strategy developed in this work, makes use of two different plasticizers: a primary “external-type” or “non-reactive-type” plasticizer, triacetin (TA), added prior to extrusion to enhance the “processing window” of the polymer and a secondary “internal-type” or “reactive-type”, Glycerin Polyglycidyl Ether (GPE), added during the extrusion step to reduce the amount of potential volatiles or leachable products in the final product and to help in the reduction of viscosity and thus further improving processability. The thermo-mechanical properties and the morphology of biocomposites with Lyocell microfibers, other wood based fillers, which are typically considered as a reference to produce “green” biocomposites from natural resources, have been analyzed.     

Green Nanoarchitectonics Using Cleistocalyx Operculatus Leaf Extract in the Preparation of Multifunctional Graphene Oxide/Fe3O4/Ag Nanomaterials for Water Decontamination and Disinfection

The demand for clean water has been increasing around the world. In this study, graphene oxide/Fe₃O₄/Ag nanomaterials with different graphene oxide:Fe₃O₄ ratios were prepared and determined the best formulations for water treatment. Ag nanoparticles were incorporated into the materials by a green reduction method using Cleistocalyx Operculatus leaf extract for the first time. The synthesized materials were characterized by FTIR, Raman, XRD, FESEM, EDX and VSM methods. The characterizations confirm that the materials have been prepared successfully with various element compositions and can be separated by outer magnetic fields. The results show that the GF31A sample with graphene oxide:Fe₃O₄ ratio of 3:1 and about 5 wt.% Ag in the composition exhibits the highest efficiency for chemical oxygen demand (COD), total nitrogen (TN) and PO₄^3? removals. This material also induces good antibacterial and antifungal activity on harmful gram (+), gram (?), and fungi microorganisms such as Staphylococcus aureus, Salmonella enterica, Candida albicans with small IC₅₀ values (from 1.5 to 11.1 mg/L). More than 70% of COD, TN, PO₄^3? and 100% of E. coli have been removed from two real water samples treated with GF31A (0.1 g/100 mL). The results reveal that GF31A is a potential agent for water treatment application. Besides the newly using of Cleistocalyx Operculatus in the synthesis, this is also the first time various graphene oxide/Fe₃O₄/Ag materials have been systematically investigated for both water decontamination and disinfection with the ease of magnetically separation.

Graphical Abstract