Abstract:
|
One of the most important ecological problems is the eutrophication, this process consist in
the uncontrolled growing of algae and phytoplankton, which can destroy entire aquatic
ecosystems. The reason of this process is the excess of nutrients, as for example,
phosphate coming from human activities.
This project focus on the study of synthetic zeolites capacity to absorb phosphate from
wastewater. Zeolites are porous minerals of the alumina-silicates family with high capacity of
cations exchange. They can be natural or synthetic and present a tetrahedral structure that
can include alkali or alkaline earth metals, those metals can improve the capacity to absorb
determinates contaminants. The zeolite used for this work is a calcium zeolite (Ca-Ze)
obtained from a synthetic sodium zeolite (NaP1). The NaP1 is produced using fly ashes as
raw material, by hydrothermal process.
The objective of the project is to evaluate: the elimination of phosphate, the equilibrium and
kinetic data, using agitated reactors, and the integration of the sorption process with a
separation process, using ultrafiltration membrane in different operating conditions. The
evaluated operation conditions are designed to simulate the treatment of residual waters
coming from industries, households and agricultural fields.
Other experiments as kinetic, isotherms and point zero charge are done to characterize the
zeolite used in the ultrafiltration plant and to make a comparison with other zeolites and
adsorbents used for phosphate removal.
Analysis results of phosphate loaded samples give information about the phosphate
adsorption mechanisms and the adsorption capacity in different working conditions. The
formation of calcium-phosphate minerals, brushite, is the principal phenomena during
adsorption, it is favoured by low pH as seen in the results.
The analytical techniques used are UV-visible spectrophotometry for phosphate analysis,
ionic chromatography for the analysis of different ions presents in the water, X ray diffraction
for zeolite sample analysis. |