08 March 2011
Posted in Center Information
rsenic in landfill leachate poses a potential problem to landfills in Florida during final leachate disposal when concentrations are above allowable limits. From a list of 68 solid waste directors in Florida, 26 responded to our email or telephone queries and 7 identified arsenic as a problem during final leachate disposal. These sites included Alachua County, Lake County, Marion County, Martin County, Orange County, Polk County and Santa Rosa County. For all, leachate was treated offsite at either a waste water treatment plant or by deep well injection. These sites paid hauling and disposal fees and faced surcharges due to leachate characteristics like concentrations of arsenic and BOD. Mineral oxides sorbents that have been gaining wide use in arsenic removal during drinking water treatment were examined in this study for their potential to remove arsenic from landfill leachate, an onsite treatment option. Though physical characteristics of Bayoxide E33 (iron oxide), ADSORBSIA GTO (titanium oxide) and Kemiron (iron oxide) were done in this study, emphasis was placed on Kemiron which has a local distributor in Florida that was interested in this application. BET surface area of Kemiron is 39.8 m2/g and Electron Dispersive Spectroscopy (EDS) studies found Kemiron to be 40.37% iron and 42.25 % oxygen by mass. Leachate (filtered) obtained from Polk County’s North Central Landfill did not affect the sorption of 800 ppb arsenate (As(V)) onto 1 g/L Kemiron between pH 5 and 9. Batch systems for arsenate (As(V)), arsenite (As(III)) and selenite (Se(IV)) removal from aqueous solutions as a function of pH, ionic strength, and particle size (< 38 μm and between 250 and 425 μm) were investigated and showed typical anionic behavior whereas As(III) sorption showed a maximum around pH 8. Langmuir isotherms best described the As(V) and Se(IV) removal at pH 7 with maximum adsorption capacity of 82 mg/g and 52 mg/g respectively. As(V) and Se(IV) sorption decreased as pH increased and both anions were unaffected by sodium nitrate (NaNO3) background electrolyte. As(V) sorption decreased in the presence of Se(IV), increased in the presence of Ca and remained unchanged in the presence of sulfate or carbonate. Though Bayoxide E33 had a higher surface area (95 m2/g) than Kemiron, its sorption capacity for As(V) under similar conditions was significantly lower. Rate of uptake experiments show that the capacity of 250-425 μm particles to sorb As(V) to be significantly lower than the 38 μm particles.