Green Chemistry is a relatively new emerging field that strives to work at the molecular level to achieve sustainability. The field has received widespread interest in the past decade due to its ability to harness chemical innovation to meet environmental and economic goals simultaneously. Green Chemistry has a framework of a cohesive set of Twelve Principles, which have been systematically surveyed in this critical review. This article covers the concepts of design and the scientific philosophy of Green Chemistry with a set of illustrative examples. Future trends in Green Chemistry are discussed with the challenge of using the Principles as a cohesive design system (93 references).

Green Chemistry: Principles and Practice

Antibacterial activity of zinc oxide nanoparticles (ZnO-NPs) has received significant interest worldwide particularly by the implementation of nanotechnology to synthesize particles in the nanometer region. Many microorganisms exist in the range from hundreds of nanometers to tens of micrometers. ZnO-NPs exhibit attractive antibacterial properties due to increased specific surface area as the reduced particle size leading to enhanced particle surface reactivity. ZnO is a bio-safe material that possesses photo-oxidizing and photocatalysis impacts on chemical and biological species. This review covered ZnO-NPs antibacterial activity including testing methods, impact of UV illumination, ZnO particle properties (size, concentration, morphology, and defects), particle surface modification, and minimum inhibitory concentration. Particular emphasize was given to bactericidal and bacteriostatic mechanisms with focus on generation of reactive oxygen species (ROS) including hydrogen peroxide (H2O2), OH− (hydroxyl radicals), and O2 −2 (peroxide). ROS has been a major factor for several mechanisms including cell wall damage due to ZnO-localized interaction, enhanced membrane permeability, internalization of NPs due to loss of proton motive force and uptake of toxic dissolved zinc ions. These have led to mitochondria weakness, intracellular outflow, and release in gene expression of oxidative stress which caused eventual cell growth inhibition and cell death. In some cases, enhanced antibacterial activity can be attributed to surface defects on ZnO abrasive surface texture. One functional application of the ZnO antibacterial bioactivity was discussed in food packaging industry where ZnO-NPs are used as an antibacterial agent toward foodborne diseases. Proper incorporation of ZnO-NPs into packaging materials can cause interaction with foodborne pathogens, thereby releasing NPs onto food surface where they come in contact with bad bacteria and cause the bacterial death and/or inhibition.

/pdf/review-on-zinc-oxide-nanoparticles-antibacterial-activity-2smaigi8sc.pdf

Review on Zinc Oxide Nanoparticles: Antibacterial Activity and Toxicity Mechanism.

https://eva.fing.edu.uy/pluginfile.php/55828/mod_resource/content/1/kalogiru.pdf

Solar thermal collectors and applications

An introduction to heat transfer

Band bending in semiconductors: chemical and physical consequences at surfaces and interfaces.

Experimental and theoretical simulations of a novel sustainable desalination process have been carried out. The simulated process consists of pumping seawater through a solar heater before flashing it under vacuum in an elevated chamber. Vacuum is passively created and then maintained by the hydrostatic balance between pressure inside the elevated flash chamber and outdoor atmospheric pressure. Experimental simulations were carried out using a pilot unit built to depict the proposed desalination system. Theoretical simulations were performed using a detailed computer code employing fundamental physical and thermodynamic laws to describe the separation process, complimented by experimentally based correlations to estimate physical properties of the involved species and operational parameters of the proposed system setting it apart from previous empirical desalination models. Experimental and theoretical simulation results matched well, validating the developed model. Feasibility of the proposed system rapidly increased with flash temperature due to increased fresh water production and improved heat recovery. In addition, the proposed desalination system is naturally sustainable by solar radiation and gravity, making it very energy efficient.

/pdf/theoretical-and-experimental-simulation-of-passive-vacuum-4v0sub94ka.pdf

Theoretical and experimental simulation of passive vacuum solar flash desalination

Transient Numerical Analysis of Storage Tanks Based on Encapsulated PCMs for Heat Storage in Concentrating Solar Power Plants

Summary
Micro-phase change materials (micro-PCMs) are proposed to increase the thermal conductivity and the thermal energy storage capacity of a heat transfer fluid (HTF). In this work, we have selected dimethyl terephthalate (DMT) to be used as a PCM for performance enhancement of a synthetic oil in the temperature range of approximately 100 to 170 °C. Silicon dioxide (SiO2) was used as the microencapsulant, because of its desirable properties as containment material, including thermal stability. The SiO2-coated DMT micro-PCM was characterized to determine relevant properties and its suitability for HTF performance enhancement. The SiO2-coated DMT was found to completely disperse in the synthetic oil, Therminol SP, silicone oil, at and above 100 °C. FTIR, thermal diffusivity and differential scanning calorimetry measurements were carried out on the materials, and these tests demonstrated that the coated particles can be used for HTF enhancement in the temperature range of 100–170 °C and potentially higher temperatures if pressurized pipes/vessels are utilized.

Using the measured thermal diffusivity and known data for density and specific heat capacity, the thermal conductivity of the micro-PCM was calculated. Our calculations indicate that both the thermal conductivity and the thermal energy storage heat capacity of the HTF would be enhanced by the addition of this micro-PCM. It is expected that the thermal conductivity increase will enhance the heat transfer of the fluid when in use at temperatures above and below the melting temperature of the PCM. At the melting point, the latent heat of the PCM will increase the thermal energy storage capacity of the fluid. Copyright © 2016 John Wiley & Sons, Ltd.

Microencapsulated dimethyl terephthalate phase change material for heat transfer fluid performance enhancement

This paper briefly describes the history and status of solar energy education. The energy awareness in the early 1970s led to a concerted research and development effort in solar energy applications. Solar energy education followed these efforts at the advanced college level. However, R&D slowed down in the mid 1980s and solar energy education at the college level followed that trend. Over the last three decades developments in solar energy applications have made it possible to use solar energy for most of our energy needs and even some environmental needs. However, despite the worldwide awareness of environmental degradation, the present public policy does not favor the use of solar energy over conventional fuels. Many solar energy applications do not appear cost effective using conventional financial tools. Therefore, there is a need to educate public policy makers, financial professionals and the general public. This presents an opportunity to develop educational materials, short courses and seminars, to educate public policy makers and financial professionals who are extremely important to increase the use of solar energy, yet who are least familiar with it. There is a great deal of K-12 solar energy educational materials that has been developed in different parts of the world. Advanced information technologies can be used to compile and make this material available throughout the world.

Present Status Of Solar Energy Education

A new desalination scheme has been proposed. The system consists of a saline water tank, a concentrated brine tank, and a fresh water tank placed on ground level plus an evaporator and a condenser located several meters above the ground. The evaporator-condenser assembly, or flash chamber, is initially filled with saline water that later drops by gravity, creating a vacuum above the water surface in the unit without a vacuum pump. The vacuum is maintained by the internal hydrostatic pressure balanced by the atmospheric pressure. The ground tanks are open to the atmosphere, while the flash chamber is insulated and sealed to retain both heat and vacuum. A theoretical simulation of the proposed model was carried out using a detailed model built by employing the fundamental physical and thermodynamic relationships to describe the process and was complimented by reliable empirical correlations to estimate the physical properties of the involved species and the operational parameters of the proposed system. The simulation results show that running the system at higher ,flash temperatures with a fixed flash chamber size will result in faster vacuum erosion leading to less overall evaporation.

D. Yogi Goswami

Papers

Theoretical and experimental simulation of passive vacuum solar flash desalination

Transient Numerical Analysis of Storage Tanks Based on Encapsulated PCMs for Heat Storage in Concentrating Solar Power Plants

Microencapsulated dimethyl terephthalate phase change material for heat transfer fluid performance enhancement

Present Status Of Solar Energy Education

Solar Flash Desalination Under Hydrostatically Sustained Vacuum