PDF Publication Title:
Text from PDF Page: 053
Black plate (275,1) sorbentyion-exchange materials for removing radioactive strontium from liquid radioactive waste and very hard groundwaters. In hard groundwaters, the presence of fairly high concentrations of e.g. Ca2 þ and Mg2 þ cations competes for and reduces the uptake of Sr2 þ . This is a very informative paper, and covers the background to this topic well183. The use of natural zeolites for the purpose of radioactive decontamination on the large scale (using 500,000 tonnes of zeolite) after the Chernobyl disaster was referred to earlier5,7,8. Nano-pore titanium silicate materials ETS-10 and ETAS-10 with different TiyAl ratios were used successfully to remove heavy-metal cations (Cu2 þ , Co2 þ , Mn2 þ and Zn2 þ ) from their aqueous solutions, and the data were fitted by various adsorption equations of which the Langmuir – Freundlich isotherm proved best. Thermodynamic measurements suggest that while the adsorption is endothermic (positive DH, negative DG), the positive entropy of adsorption indicates that the cations are not taken-up in stable sites on the surfaces of these materials, probably because of the increase in translational energy that is gained when they are displaced from their primary adsorption sites184. The contamination of soils and groundwaters by Zn2 þ and Pb2 þ (from tin-solder) from run-off of rain from galvanised roofs is a matter of growing concern. Both clinoptilolite and geotextile filters have been employed in attempts to intercept these toxic cations. While the geotextile filter is ineffective is retaining these heavy metal cations, perhaps not surprisingly, the clinoptilolite filter retained 97% of their initial concentration185. Naturally occurring Turkish zeolite minerals which contained 45% clinoptilolite and 35% mordenite were used to remove lead and zinc cations from their aqueous solutions186. The potential application of natural Turkish clinoptilolite to removing Co2 þ , Cu2 þ , Zn2 þ and Mn2 þ from the wastewaters of metal finishing processes has also been described187. A significant improvement of the ability of natural clinoptilolite to take-up Zn2 þ was reported if the zeolite was first exchanged with Na þ cations by chemical conditioning with 1 M NaCl solution188. The ‘‘radiation removal’’ of lead from aqueous solutions has been described. In essence, an aqueous solution of Pb2 þ cations is treated with various sorbent materials (activated carbon, bentonite and zeolite) and exposed to radiation from an electron beam. While the results are somewhat variable as to the efficacy of the irradiation in its effect on lead removal, a substantial increase in the effective- ness of the process is indicated when the solution is saturated with www.scienceprogress.co.uk Properties and applications of zeolites 275PDF Image | Properties and applications of zeolites
PDF Search Title:
Properties and applications of zeolitesOriginal File Name Searched:
003685010x12800828155007.pdfDIY PDF Search: Google It | Yahoo | Bing
CO2 Organic Rankine Cycle Experimenter Platform The supercritical CO2 phase change system is both a heat pump and organic rankine cycle which can be used for those purposes and as a supercritical extractor for advanced subcritical and supercritical extraction technology. Uses include producing nanoparticles, precious metal CO2 extraction, lithium battery recycling, and other applications... More Info
Heat Pumps CO2 ORC Heat Pump System Platform More Info
| CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com | RSS | AMP |