Zeolite directly formed after 1 month in polluted soil according to the process of the invention [US Patent 8,435,487] (from Belviso et al., 2010).
Effect of zeolite mass on the removal of Mn using 100, 250, 500 and 1000 ml of contaminated solution [US Patent 8,435,487] (from Belviso et al., 2013, submitted).
SEM and EDX spectra of zeolites formed according to the process indicates the presence of Pb entrapped into the mineral structure or precipitated onto its surface. BE images (Backs-cattered Electron images) show no brightness change of zeolite surface suggesting that Pb is not locally concentrated. [US Patent 8,435,487] (from Belviso et al., 2012
Zeolites are characterized by high cation exchange capacity, large surface area and open structure. These characteristics make them very useful in various uses and employed in particular to solve environmental problems linked to the immobilization of toxic elements. The method deals with an inerting fly ash by conversion in zeolite. The zeolite obtained could be used to remove contamination from water and soil as well as in concrete and cement manufacturing, glass ceramic production and as builder for detergent..
The technology can be used to make useful material (zeolites) from waste material (fly ash). Fly ash is the most abundant coal combustion by-product. Due to the presence of inorganic pollutants it is classified as an hazardous residue. Specifically, it is possible to obtain:• elimination of fly ash hazard by conversion in zeolites • reduction in the quantity of fly ash to be disposed in landfill • elimination of costs for large-scale use of distilled water for production of zeolites from fly ash• drastic reduction in cost of energy as with sea water higher amount of zeolite formed at low temperatures• increase in the yield of zeolites production, comparing with that obtained using distilled water.
Heavy metals immobilization in zeolites synthesized from fly ash at low temperature using seawater
Detailed Technology Description
This invention relates to a process for synthesizing geopolymers and zeolites from fly ash. In particular, it relates to a process for synthesizing X-type zeolites.
Zeolites are hydrated aluminosilicate minerals characterized by a three-dimensional open structure that makes them very useful in various practical uses and employed in particular to solve environmental problems linked to the immobilization of toxic elements. This use is closely linked to their cation exchange capacity (CEC), to the large surface area and to the typical structural characteristics (porosity) that in case allow any absorption and encapsulation of the pollutant. Synthetic zeolites are characterized by a cation exchange capacity and by absorption capacities similar to, and in some cases greater than, natural zeolites.
Fly ash is a by-product of thermal power plants composed of mineral material refractory to combustion and of residual components for which combustion of the initial coal takes place incompletely. In particular, fly ash is characterized by three types of constituents: minerals (mainly quartz and mullite, subordinately hematite and magnetite), unburned coal particles and prevalent amorphous aluminosilicate phase. By virtue of its disordered atomic structure, of its porous nature and of its abundance, glass represents the main constituent involved in chemical reactions associated with the use of fly ash in geopolymer and zeolite synthesis.
The invention is ready for pilot production scale-up.
· Number:US8435487 B2
· Title:SYNTHESIS OF ZEOLITE FROM FLY ASH
Collaboration type sought
Different types of zeolites can be synthesized, although the X-type zeolite, or faujasite, is particularly interesting as regards characteristics and possible uses, as it presents high cation exchange capacity due to its structure characterized by pores of large dimensions.
Over the last decades, numerous methods have been proposed for geopolymer and zeolite synthesis starting from fly ash. The differences concern type of alkaline solutions, molarity of alkaline agents, solution/fly ash activation ratio, temperature, reaction time, pressure and incubation type. Two known processes are: a hydrothermal process and a hydrothermal process with fusion pre-treatment at high temperatures (500°C). The hydrothermal process with fusion pre-treatment at high temperatures presents a greater conversion of fly ash into zeolite compared to the hydrothermal process alone, and in any case the formation of zeolite X under 60°C is not documented. Data present in the literature in fact show experimental evidence of the formation of X-type zeolites with fusion pre-treatment only starting from incubation temperatures of over 60°C. In this process too the use of distilled or tap water increases process costs.
There is, therefore, the need for an X-type zeolite production process that solves the problems of the low yields in synthesis and of the high costs of processes for synthesizing zeolites X known in the art.
These problems are solved by the present invention with a synthesis process that utilizes sea water and low incubation temperatures.