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Topic Review
Plastic Sand as a Construction Material
Plastic waste pollution poses a serious environmental concern. At the same time, the cement industry is among the biggest sources of CO2 emissions, which poses another environmental challenge. Plastic sand bricks could be a workable solution for combating issues related to solid waste. The compressive strength decreased with increasing ratios of plastic to sand. Plastic sand bricks weighed less than the conventional bricks.
  • 9.0K
  • 10 Jun 2022
Topic Review
Olefins Production via Steam Cracking:Effect of Operating Parameters
Various parameters need to be considered to optimize a pyrolysis reactor for the production of ethylene and propylene. These parameters are included temperature, residence time, steam-to-hydrocarbon ratio, and feedstock composition. A higher reaction temperature results in a higher yield of ethylene, a shorter residence time, and higher reaction velocities. A low operating pressure is preferred for this process because of the gas phase reaction inside the reactor tubes and the production of more gaseous molecules for its reactions to the right. The reactor pressure must be kept as low as possible (between 170 and 250 kPa). The gas pressure in the reactor tube outlet is indirectly adjusted by the suction process gas pressure of the compressor in the compression section, downstream of the process. As mentioned earlier, to reach lower hydrocarbon pressures, process steam is co-fed with the hydrocarbon feed to reduce the hydrocarbon partial pressure and lower coke deposition. The addition of steam decreases the partial pressure of the hydrocarbon feed and favors the formation of primary products.
  • 5.3K
  • 16 Dec 2021
Topic Review
Mass Transfer in Packed-Bed Columns
This review provides a thorough analysis of the most famous mass transfer models for random and structured packed-bed columns used in absorption/stripping and distillation processes, providing an overview of the equations to calculate the mass transfer parameters, i.e.: gas-side coefficient per unit surface ky [kmol·m-2·s-1], liquid-side coefficient per unit surface kx [kmol·m-2·s-1], interfacial packing area ae [m2·m-3], which constitute the ingredients to assess the mass transfer rate of packed-bed columns. This work also provides the ranges of model validity and applicability together with their main pros and cons and the criticalities behind these models, which mostly rely on the assessment of fluid-dynamics parameters such as liquid film thickness, liquid hold-up and interfacial area, or the real liquid paths or any mal-distributions flow. 
  • 5.1K
  • 01 Sep 2021
Topic Review
Copper Heap Leaching
Heap leaching is a firm extractive metallurgical technology facilitating the economical processing of different kinds of low-grade ores that are otherwise not exploited.
  • 5.1K
  • 13 Oct 2021
Topic Review
Deep Eutectic Solvents (DES)
Deep eutectic solvent (DES) are a highly non-ideal mixture of two biodegradable components (HBA and HBD) associated with strong hydrogen bonding interactions. 
  • 5.0K
  • 08 Mar 2022
Topic Review
Effect of Temperatures on Polyphenols during Extraction
Polyphenols are a set of bioactive compounds commonly found in plants. These compounds are of great interest, as they have shown high antioxidant power and are correlated to many health benefits. Hence, traditional methods of extraction such as solvent extraction, Soxhlet extraction and novel extraction technologies such as ultrasound-assisted extraction and subcritical water extraction (SWE) have been investigated for the extraction of polyphenols.
  • 4.3K
  • 09 Mar 2022
Topic Review
CO2 Separation Techniques
Energy plants, industries, as well as other sources of carbon dioxide (CO2) result in global warming and affect the planet. CO2 is separated from flue gas during combustion using a variety of advanced separation techniques. There are several techniques involved, such as absorption, adsorption, chemical looping, membrane separation, and cryogenics.
  • 3.9K
  • 13 Dec 2022
Topic Review
Screen-Printed Electrodes
Screen printed electrodes(SPE) are disposable, low-cost and portable devices that include a miniaturized display of the working, reference and counter electrodes; based on conductive substrates like carbon nano allotropes (e.g. graphite, graphene) and metals (e.g. Au, Ag, Pt). This configuration is optimized to work with micro-volumes of samples. Their range of applications includes electrochemical analysis in environmental, clinical and agri-food fields.
  • 3.7K
  • 21 Apr 2021
Topic Review
Dyes from Microorganisms
"Dyes from Microorganisms" means production of pigments using single cell microorganisms. It is gaining traction as a sustainable alternative to conventional synthesis.
  • 3.7K
  • 24 Feb 2022
Topic Review
Starch-Based Biodegradable Films for Food Packaging
The use of biodegradable packaging material as an alternative to conventional petrochemical-based polymers is based on the environmental issues associated with conventional materials. Starch-based biodegradable films can be applied in food packaging. It was evident that starch stands out among biopolymers due to its abundance and cost effectiveness.
  • 3.6K
  • 07 Apr 2022
Topic Review
Waste Plastic Recycling and Technology
Plastic waste recycling refers to the waste management process that collects plastic waste materials and turns them into raw materials reused to produce other valuable products. Recycling is not only a method for disposing of plastic waste, but it is also an effective process to minimize the need for virgin plastics, which can help lessen global warming. According to the ASTM Standard D5033, plastic recycling can be categorized as primary, secondary, tertiary, and quaternary recycling. Based on the mechanism of the methods, plastic waste recycling can be classified as mechanical, chemical, and biological recycling. Chemical recycling, such as catalytic and thermal processes, can convert plastic waste into value-added chemicals/fuels. This process is a potential method to reduce plastic waste as a primary source of environmental issues.
  • 3.3K
  • 04 Aug 2022
Topic Review
Reverse Water Gas Shift Reaction
The catalytic conversion of CO2 to CO by the reverse water gas shift (RWGS) reaction followed by well-established synthesis gas conversion technologies could be a practical technique to convert CO2 to valuable chemicals and fuels in industrial settings. For catalyst developers, prevention of side reactions like methanation, low-temperature activity, and selectivity enhancements for the RWGS reaction are crucial concerns. Cerium oxide (ceria, CeO2) has received considerable attention due to its exceptional physical and chemical properties. 
  • 3.2K
  • 09 Oct 2022
Topic Review
Metal Sulfide Precipitation
Metal sulfide precipitation can efficiently recover several metals and metalloids from different aqueous sources, including wastewaters and hydrometallurgical solutions. 
  • 3.2K
  • 04 Jan 2022
Topic Review
Abiotic and Biotic Polymer Degradation Mechanisms
Polymer degradation is defined as an irreversible change of the chemical structure, physical properties, and visual appearance due to the chemical cleavage of the polymer’s constitutive macromolecules by one or more mechanism. More than one mechanism can simultaneously take place due to the action of external factors, and one mechanism can be more dominant than others at any time. External factors associated with the environment, such as heat, humidity, radiation, and acidic or alkaline conditions, could modify the degradation process and its rate. The degradation process can alter polymer properties such as mechanical, optical, electrical, discoloration, phase separation or delamination, erosion, cracking, and crazing. The four main abiotic mechanisms associated with polymer degradation are mechanical, thermal (or thermo-oxidative), photo (photo-oxidative), and hydrolytic (chemical) degradation, some of which can be assisted by catalysis. In addition, ozone degradation (chemical) is considered a mechanism of degradation for polymers but is less common. The biotic degradation involves the action of microorganisms by enzymatic action.
  • 3.0K
  • 27 Oct 2022
Topic Review
Removal of Purines from Beer
Beer corresponds to a fermented alcoholic beverage composed of several components, including purine compounds. These molecules, when ingested by humans, can be catabolized into uric acid, contributing to uric acid’s level increase in serum, which may lead to hyperuricemia and gout. To assure a proper management of this disease, physicians recommend restrictive dietary measures, particularly by avoiding the consumption of beer. Therefore, it is of relevance to develop efficient methods to remove purine compounds from alcoholic beverages such as beer. There are several enzymatic, biological, and adsorption methods reported envisaging purine compounds’ removal. Some enzymatic and biological methods present drawbacks, which can be overcome by adsorption methods. Within adsorption methods, adsorbent materials, such as activated carbon or charcoal, have been reported and applied to beer or wort samples, showing an excellent capacity for adsorbing and removing purine compounds. By ensuring the selective removal of purine compounds from this beverage, beer can be taken by hyperuricemic and gouty patients, avoiding restrictive dietary measures, while decreasing the related healthcare economic burden. 
  • 2.8K
  • 23 Nov 2021
Topic Review
Power Generation in Sewage-Water Treatment Plants
Sewage-water treatment comprehends primary, secondary, and tertiary steps to produce reusable water after removing sewage contaminants. However, a sewage-water treatment plant is typically a power and energy consumer and produces high volumes of sewage sludge mainly generated in the primary and secondary steps. The use of more efficient anaerobic digestion of sewage water with sewage sludge can produce reasonable flowrates of biogas, which is shown to be a consolidated strategy towards the energy self-sufficiency and economic feasibility of sewage-water treatment plants. Anaerobic digestion can also reduce the carbon footprint of energy sources since the biogas produced can replace fossil fuels for electricity generation. 
  • 2.7K
  • 05 May 2022
Topic Review
Odor Measurement Methods
Odor pollution related to industrial activities (e.g., chemical industries, oil and gas extraction and refining facilities, waste treatment and disposal facilities) is nowadays acknowledged as a serious environmental concern. Indeed, odors are currently subjected to control and regulation in many countries. Such regulations rely on the possibility of measuring odors. The methods that have been developed and standardized over the last years to measure odors, thereby including sensorial and instrumental techniques, are here described, thereby focusing on their applicability and limitations.
  • 2.5K
  • 08 Feb 2022
Topic Review
Brine Management
Desalination brine is extremely concentrated saline water; it contains various salts, nutrients, heavy metals, organic contaminants, and microbial contaminants. Conventional disposal of desalination brine has negative impacts on natural and marine ecosystems that increase the levels of toxicity and salinity. These issues demand the development of brine management technologies that can lead to zero liquid discharge. Brine management can be productive by adopting economically feasible methodologies, which enables the recovery of valuable resources like freshwater, minerals, and energy.
  • 2.3K
  • 20 Jun 2022
Topic Review
Hydrogen Economy
Environmental issues make the quest for better and cleaner energy sources a priority. Worldwide, researchers and companies are continuously working on this matter, taking one of two approaches: either finding new energy sources or improving the efficiency of existing ones. Hydrogen is a well-known energy carrier due to its high energy content, but a somewhat elusive one for being a gas with low molecular weight. The so-called "Hydrogen Economy" is based on the use of hydrogen as an energy source. This entry examines the current electrolysis processes for obtaining hydrogen, with an emphasis on alkaline water electrolysis.
  • 2.2K
  • 18 Sep 2021
Topic Review
CO2 and H2S Separation Technologies
The emerging economic activities, modernization of technology and progressive transition from coal utilization to low-carbon fuel drive the rising energy demand. Natural gas is well-known as clean energy resources for electricity generation and fuel for transportation. Currently, CO2 and H2S content in gas fields accounts for up to 90% and 15%, respectively. Apart from fulfilling the market demand, the removal of these contaminants from natural gas is critical due to their corrosive natures, low heating value of natural gas and  greenhouse gas effect. To date, numerous gas fields remain unexplored due to high presence of contaminants. Several technologies such as absorption, adsorption, membrane separation and cryogenic distillation have been developed for natural gas sweetening. This entry comprehensively discussed the mechanisms and state-of-the-art of these conventional technologies.
  • 2.2K
  • 03 Mar 2022
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