Karmen Margeta

Natural Zeolites in Water Treatment – How Effective is Their Use

The unique treedimensional porous structure gives natural zeolites various application possibilities. Because of the excess of the negative charge on the surface of zeolite, which results from isomorphic replacement of silicon by aluminum in the primary structural units, natural zeolites belong to the group of cationic exchangers. Natural zeolites have advantages over other cation exchange materials such as commonly used organic resins, because they are cheap, they exhibit excellent selectivity for different cations at low temperatures, which is accompanied with a release of non-toxic exchangeable cations (K+, Na+, Ca2+ and Mg2+) to the environment, they are compact in size and they allow simple and cheap maintenance in the full-scale applications. The efficiency of water treatment by using natural and modified zeolites depends on the type and quantity of the used zeolite, the size distribution of zeolite particles, the initial concentration of contaminants (cation/anion), pH value of solution, ionic strength of solution, temperature, pressure, contact time of system zeolite/solution and the presence of other organic compounds and anions. For water treatment with natural zeolites, standard procedures are used, usually a procedure in column or batch process. More careful consideration of their superb metal removal properties and awareness of possible regeneration or further use of contaminant/metal-loaded forms can considerably increase their environmental application possibilities, with a focus the reduction of high concentrations of cations and anions in drinking water and wastewater, for surface, underground and public municipal water treatment independently or in combination with others physical - chemical methods.

Phenol oxidation with hydrogen peroxide using Cu/ZSM5 and Cu/Y5 catalysts

Phenol oxidation with hydrogen peroxide using Cu/ZSM5 and Cu/Y5 catalysts In this work, catalytic activity and stability of Cu/Y5 and Cu/ZSM5 zeolites in phenol oxidation with hydrogen peroxide were examined. The catalyst samples were prepared by the ion exchange method of the protonic form of commercial zeolites. The catalysts were characterized by the powder X-ray diffraction (XRD), AAS, while the adsorption techniques were used to measure the specific surface area. The thermal programmed desorption of NH3 (NH3-TPD) was used for measuring the total number of acid sites formed on the surface of zeolites. Catalytic performance of the prepared samples was monitored in terms of phenol, hydrogen peroxide and total organic carbon (TOC) conversion, by-product distribution and a degree of copper leached into the aqueous solution. It was found that the activity of Cu/Y5 catalyst was generally higher than that of Cu/ZSM5 and that unlike Cu/ZSM5, Cu/Y5 catalyzed phenol oxidation more completely.

Development of natural zeolites for their use in water-treatment systems.

This paper gives an overview of research and patents concerning the use of natural zeolites in water-treatment systems in the last ten years. Furthermore, nanocomposite materials made of natural zeolites and organic and polymeric materials are also mentioned as an effective solution in water treatment. An additional emphasis is put on a variety of possibilities for further application of natural zeolite materials for environment protection and preservation.

Revitalization of Hydro Energy: A New Approach for Storing Solar Energy

Currently, the most suitable technology for storing relatively large amounts of solar energy is hydro energy (pumped storage hydroelectricity (PSH)). Given the problem of intermittent solar energy and the inability to ensure a continuous energy supply to customers throughout the year, this chapter analyzes the integration of solar (photovoltaic or solar thermal) and hydro energy. With all known technologies of storage, only hydro energy can balance seasonal surpluses and shortages of solar energy, and in this way ensure continuous energy supply to consumers throughout the year with low environmental impact. The disadvantages of the site-specific construction of this system can be avoided by using geosynthetics for the construction of reservoirs of PSH in virtually all places where there are height differences. A very important polymer material, geomembranes, which belong to the group of geosynthetics (e.g., geotextiles, geogrids, geonets, geosynthetic clay liners, geopipe, geofoam, geocomposites), can significantly contribute to the further development of PSH technology. The results from the case study show that this concept of using hydro energy for solar energy storage could be flexible in design, construction, and operation.