Monitoring and Extraction of Arsenic Ions from Water
Development of Arsenic Extraction Technology Based on Magnetic Nanocomposite Use, Monitoring As(III) and As(V) in Waters
Tech Area / Field
- CHE-ANL/Analytical Chemistry/Chemistry
- ENV-MIN/Monitoring and Instrumentation/Environment
- ENV-WPC/Water Pollution and Control/Environment
- INS-DET/Detection Devices/Instrumentation
3 Approved without Funding
National Academy of Sciences of Kyrgyzstan / Institute of Chemistry and Chemical Technology, Kyrgyzstan, Bishkek
- Institut Catala de Nanotecnologia, Spain, Bellaterra\nUniversidad Complutense de Madrid, Spain, Madrid
Project summaryThe aim of the project is to develop environmentally sound technology for drinking water purification from arsenic, express-monitoring of inorganic arsenic speciation and automatic smart portable “one-button” arsenic sensing device.
With regard to analytical control the aim of the project is to develop a highly sensitive electrochemical sensor, express monitoring of valence forms of arsenic, smart portable voltammetric analyzer based on modern element base which can be used for laboratory and field analysis and work with high-precision metering devices on the principle of "one button» and fully automated measuring cycles that do not requiring intervention and the control of the operator during analysis procedure. As a result, the project will develop electronic and electrochemical components of the analyzer; original software that enables to handle compact automatic metering devices of high accuracy for the introduction of standard additions of a determined element; environmentally friendly high sensitive strip sensors, express methods of determining both the total contents of arsenic and its inorganic valent forms (As (III) and As (V)) in different types of waters.
For the removal of arsenic ions from water a low-cost magnetic sorbent material prepared by coating Fe3O4 magnetic nanoparticles with humic substances (HS) will be proposed. Recent research of project participants indicated that HS has high affinity to Fe3O4 nanoparticles, and sorption of humic acids HA on the magnetite nanoparticles enhanced the stability of nanodispersions by preventing their aggregation (Zaripova, 2008). Abundant in natural aqueous systems, HA has a skeleton of alkyl and aromatic units that attach with carboxylic acid, phenolic hydroxyl, and quinone functional groups (23). As these functional groups have high complex capacity with any speciation of the ecotoxicants, HA can be applied to remove arsenic ions from water. Being magnetic, the Fe3O4/HA can be simply recovered from water with magnetic separations at low magnetic field gradients within a few minutes.
Theoretical basis for the development of the sensory aspect of the analytical control method are the studies of the project participants, in particular, research and developement of a new generation of electrochemical sensors (Brainina., 1999, 2002, 2004; Stozhko, 1998, 2005 -2008; Malakhova, 2010). The studies showed that it is the sensor (electrode) that has a significant impact on shaping the analytical signal in electrochemical methods of analysis. The condition and structure of its surface, assigned by production, processing and modification, directly affect electrode processes and the properties of the sensor as a whole. The studies determined the patterns of the influence of solid surface microrelief and ways of modifying the electrode on the structure and electrochemical activity of the modifier. According to the pattern, the most electrochemically active ultramicro-and nanostructures of the modifier are formed from the compounds immobilized on a microscopically inhomogeneous and defective graphite –containing surface. It was proved that the transition from macro to micro and nano-structured sensor surface leads to significant improvement in electroanalytical values of element determination. First proposed a method for forming ensembles of ultramicro-and nanoparticles of metal by the discharge of metal ions from compounds, which are localized on the graphite-containing surface, was pioneered to use. The sensor surfaces ultramicro-and nanostructured with metals- modifiers facilitate the processes of discharge-ionization of metals, reduce the half-width of the peaks, increase sensitivity and selectivity of SV-determination, improve metrological indicators of electrochemical analysis.
Theoretical basis for the development of hardware and methods of analytical monitoring of arsenic are the studies of the project participants in the field of developing laboratory and portable voltammetric analyzers for determination of toxic elements; original thick film environmentally friendly graphite containing sensors, analysis techniques and software. Within the framework of the ISTC project #342-1 they developed and produced a pilot sample of the laboratory IBM-compatible voltammetric analyzer, which consists of an electronic unit, an electrochemical unit and the PC. The device can work in the modes of sample preparation, accumulation of the determined element on the electrode surface, signal measurement, regeneration of the electrode surface as well as interprete electrochemical curves. The performance of the analyzer on RS232 channel, reading and interpretation of measurement results are ensured by software implemented as Windows - applications with multi-window interface (MDI). (Brainina et al., 1999). The pilot sample enabled to design and certify the laboratory inversion-voltammetric complex IVA-5 (Russian State Standard Certificate #9953 dated 03 May 2001) used for determination of various elements (Cu, Pb, Cd, Zn, Ni, Cr, W, Mo, Mn, etc.) in natural, drinking and waste water, soil, air, food and food raw materials, biological fluids, cosmetic and medicinal preparations (Brainina et al, 2002; Miroshnikova et al, 2002).
The basis of the development under this project proposal is previous studies of the project participants, in particular, concerning structure, reactivity and detoxifying ability of humics toward heavy metals and radionuclides, methods of synthesis and testing of the metalopolymer nanocomposites, including the metalocomplexes based on humic substances (Jorobekova, 2004; Pomogailo, 2000, 2005, 2006, 2009, Zaripova et al., 2008, Kydralieva, 2007). Due to long term co-operation with foreign collaborators from the National Research Centre for Protection of Health and Environment (Helmholz-Munich Zentrum, GSF, Munich, Germany) and Cranfield University we got deeply engaged with analysis of humics-based materials, including magnetic humics-based nanocomposites. Within framework of ISTC project KR-1316 it has been evinced that Fe3O4 nanoparticles stabilized by humic substances (Fe3O4/HS nanocomposite) efficiently removed radioactive and heavy metal ions U(IV), Cr(III), Mn(II), Zn(II) from contaminated water. The Fe3O4/HS was able to remove over 95% of U(IV) and Zn(II) and over 80% of Cr(III) and Mn(II) in soil water. Being magnetic, the nanoparticles (saturation magnetization of ~30 emu/g) are readily separable using an external magnetic field, while the humic acid coating effectively stabilizes the particles against aggregation. This study revealed that, compared to HS alone, the specially prepared Fe3O4/HS exhibited remarkable enhancement of material stability and contaminant removal efficiency.
In order to achieve our goals, the following tasks need to be solved:
- To develop a highly sensitive electrochemical sensor for express monitoring of valence forms of arsenic;
- To develop methods for determination arsenic (total), arsenic (III) and arsenic (V) in drinking and natural waters;
- To develop smart portable voltammetric analyzer of inorganic arsenic speciation;
- To fabricate and characterize the nanocompositional magnetoactive humics-based materials;
- To assess the complexing and detoxifying ability of the produced humics-based nanomaterials with respect to arsenic under laboratory conditions;
- To evaluate the toxic potential of humics-based nanomaterials.