| Summary: |
We propose in this project to develop the voltametric techniques using the hanging mercury drop electrode (HMDE) which are specially adequate for the ionic speciation in natural and groundwater matrices. This methodology has a very low cost in terms of the necessary instruments when compared to the methods mentioned above and allows the direct speciation of As without any sophisticated sample treatment (allowing to keep the original As(III) to As(V) ratio without perceptible changes). It is a method appropriated to be applied in areas and laboratories with lower economic capacity; it can be easily taught and later used on an everyday base by technicians with average qualifications. The limits of detection are sufficiently low to match the objectives of this project.
There are three primary categories of available treatment processes.
Sorption Treatment Processes:
- Ion Exchange
- Activated Alumina
- Iron Based Sorbents
Membrane Treatment Processes:
- Reverse Osmosis
Precipitation/Filtration Processes:
- Enhanced Conventional Gravity Coagulation/Filtration
- Coagulation-Assisted Microfiltration (CMF)
- Coagulation-Assisted Direct Filtration (CADF)
- Oxidation/Filtration
- Enhanced Lime Softening
Activated alumina is expensive and needs a pH correction and specialized staff . The coagulation-precipitation processes also need previous pH correction and the limit concentration of 0,01 mg/L is difficult to attain. The ion exchange resins need important investments and its applicability depends upon the competition with other anions present in the water. The reverse osmosis allows the simultaneous removal of other ions but has extremely high costs. We intend to research emerging economic technologies - specially the usage of granular iron hydroxides and hybrid sorbents - generally designated by Iron Based Sorbents (IBS).
The research will focus on the usage of multifunctional permeable reactive barriers (MPRB) based on IBS and comprehending a two  |
Summary
We propose in this project to develop the voltametric techniques using the hanging mercury drop electrode (HMDE) which are specially adequate for the ionic speciation in natural and groundwater matrices. This methodology has a very low cost in terms of the necessary instruments when compared to the methods mentioned above and allows the direct speciation of As without any sophisticated sample treatment (allowing to keep the original As(III) to As(V) ratio without perceptible changes). It is a method appropriated to be applied in areas and laboratories with lower economic capacity; it can be easily taught and later used on an everyday base by technicians with average qualifications. The limits of detection are sufficiently low to match the objectives of this project.
There are three primary categories of available treatment processes.
Sorption Treatment Processes:
- Ion Exchange
- Activated Alumina
- Iron Based Sorbents
Membrane Treatment Processes:
- Reverse Osmosis
Precipitation/Filtration Processes:
- Enhanced Conventional Gravity Coagulation/Filtration
- Coagulation-Assisted Microfiltration (CMF)
- Coagulation-Assisted Direct Filtration (CADF)
- Oxidation/Filtration
- Enhanced Lime Softening
Activated alumina is expensive and needs a pH correction and specialized staff . The coagulation-precipitation processes also need previous pH correction and the limit concentration of 0,01 mg/L is difficult to attain. The ion exchange resins need important investments and its applicability depends upon the competition with other anions present in the water. The reverse osmosis allows the simultaneous removal of other ions but has extremely high costs. We intend to research emerging economic technologies - specially the usage of granular iron hydroxides and hybrid sorbents - generally designated by Iron Based Sorbents (IBS).
The research will focus on the usage of multifunctional permeable reactive barriers (MPRB) based on IBS and comprehending a two stage treatment: the previous oxidation of As and its in-situ fixation by IBS. The barriers to be considered will be of the funnel and gate type. The active sorbent will fill up the gate. As the reaction is irreversible the gates must be easily movable for substitution. It is aimed to reach an economic technology which can be adapted to small communities or to isolated populations. |