Arsenic removal by solar oxidation in groundwaters of Los Pereyra, Tucumán province, Argentina

D?HIRIART J.; GARCÍA M. G; HIDALGO M. DEL V; LITTER M.I; BLESA M. A

México DF, México

Congreso; International congress of Natural arsenic in groundwaters of Latin America; 2006

UNAM

Shallow groundwaters from Los Pereyra, Tucumán, are normally used for human consumption. These waters show arsenic concentrations that exceed the Argentine standard requirements for drinking water. The SORAS method (Solar Oxidation and Removal of Arsenic) is based on the photochemical oxidation of As(III) to As(V) produced by reactive oxygen species formed in Fe/citrate containing systems, followed by As(V) adsorption onto the precipitated iron (hydroxides). SORAS method provides an economical technology to eliminate arsenic until the allowable limits. In the present work, the efficiency of As removal by solar oxidation was assessed using synthetic waters of known ionic composition and shallow groundwater samples. As the concentration of iron in the tested waters is very low and the photooxidation of As (III) at pH between 6 and 8 is favoured by citrate, studies changing the sources of iron and amounts of citrate were made. Citrate was added in the form of lemon juice. Tests carried out with synthetic waters of similar composition to the study waters showed an excellent removal, ranging between 90-60%. The efficiency of removal was much lower in well waters, between 60-30%. Results showed the influence of the water matrix and the source of iron supply, both factors related to the precipitation of iron (hydr)oxides. The influence of organic matter, HCO3- content and the initial As concentration on the precipitation of (hydr)oxides and on the AsO43- adsorption was assessed. An increase in the concentration of HCO3- enhanced As removal and Fe(III) precipitation, whereas an increase of organic matter produced only a slight decrease in both factors. Removal efficiency decreased with the increase of the initial As concentration. The effect of different Fe sources on the efficiency was analyzed using synthetic goethite, Fe-oxide rich sandstones and pelites, packing wire, and nails. Removal varied between 30 to 90% depending on the experimental conditions and the nature of the iron source. Results obtained using nongalvanized packing wire are prominent, due to the short solar exposure time and the absence of color or turbidity in the final treated water. The effect of different Fe sources on the efficiency was analyzed using synthetic goethite, Fe-oxide rich sandstones and pelites, packing wire, and nails. Removal varied between 30 to 90% depending on the experimental conditions and the nature of the iron source. Results obtained using nongalvanized packing wire are prominent, due to the short solar exposure time and the absence of color or turbidity in the final treated water. The effect of different Fe sources on the efficiency was analyzed using synthetic goethite, Fe-oxide rich sandstones and pelites, packing wire, and nails. Removal varied between 30 to 90% depending on the experimental conditions and the nature of the iron source. Results obtained using nongalvanized packing wire are prominent, due to the short solar exposure time and the absence of color or turbidity in the final treated water. The effect of different Fe sources on the efficiency was analyzed using synthetic goethite, Fe-oxide rich sandstones and pelites, packing wire, and nails. Removal varied between 30 to 90% depending on the experimental conditions and the nature of the iron source. Results obtained using nongalvanized packing wire are prominent, due to the short solar exposure time and the absence of color or turbidity in the final treated water. The effect of different Fe sources on the efficiency was analyzed using synthetic goethite, Fe-oxide rich sandstones and pelites, packing wire, and nails. Removal varied between 30 to 90% depending on the experimental conditions and the nature of the iron source. Results obtained using nongalvanized packing wire are prominent, due to the short solar exposure time and the absence of color or turbidity in the final treated water. The effect of different Fe sources on the efficiency was analyzed using synthetic goethite, Fe-oxide rich sandstones and pelites, packing wire, and nails. Removal varied between 30 to 90% depending on the experimental conditions and the nature of the iron source. Results obtained using nongalvanized packing wire are prominent, due to the short solar exposure time and the absence of color or turbidity in the final treated water. The effect of different Fe sources on the efficiency was analyzed using synthetic goethite, Fe-oxide rich sandstones and pelites, packing wire, and nails. Removal varied between 30 to 90% depending on the experimental conditions and the nature of the iron source. Results obtained using nongalvanized packing wire are prominent, due to the short solar exposure time and the absence of color or turbidity in the final treated water. 3- content and the initial As concentration on the precipitation of (hydr)oxides and on the AsO43- adsorption was assessed. An increase in the concentration of HCO3- enhanced As removal and Fe(III) precipitation, whereas an increase of organic matter produced only a slight decrease in both factors. Removal efficiency decreased with the increase of the initial As concentration. The effect of different Fe sources on the efficiency was analyzed using synthetic goethite, Fe-oxide rich sandstones and pelites, packing wire, and nails. Removal varied between 30 to 90% depending on the experimental conditions and the nature of the iron source. Results obtained using nongalvanized packing wire are prominent, due to the short solar exposure time and the absence of color or turbidity in the final treated water.iron source. Results obtained using nongalvanized packing wire are prominent, due to the short solar exposure time and the absence of color or turbidity in the final treated water.