| Summary: World Health Organization (WHO) has classified arsenic as the most toxic chemical with carcinogenic effects and WHO has established a value of 10 μg/L arsenic as the maximum contaminant level for arsenic in potable water. Many methods have been developed to remove arsenic from water (i.e. precipitation and adsorption). Adsorption technique is gaining popularity due to its simplicity, potential for regeneration and readily availability of many low-cost adsorbents.
This study describes a study of the sorptive removal of arsenic from boron water by synthetically prepared Fe-Hydrotalcite (FeHT), nanomagnetite based Fe-Hydrotalcite (FeHT-NM) as layered double hydroxide and commercial Nanomagnetite (NM). The synthesis of FeHT and FeHT-NM was achieved by a co-precipitation method. The reaction products were characterized by XRD, TEM, SEM and magnetic susseptibility analysis. The influences of solution pH, initial arsenic (As(V) and As(III)) concentration and adsorbent dosage were investigated. The results indicate that the adsorption of arsenic by NM were affected only slightly at initial pH values of ≤pH 9. The adsorption of arsenic by FeHT was independent of initial pH values. The addition of FeHT to water at different pH values was found to have a buffering effect. The amount of arsenic removed from boron solutions was not change by increasing the boron concentration for all adsorbents. The experimental studies show that adsorption of arsenic can be obtained over a short period of time. The adsorption of As(V) on NM was rapid with 96.6% removal of As over an initial period of only 15 min. The pseudo second order kinetic model was found to fit better to the experimental data. The results obtained from the isotherm analysis indicated that the Langmuir model describes the arsenic adsorption isotherm data onto adsorbents best. According to results of As experiments, NM, FeHT ve FeHT-NM has a high arsenic removal efficiency, with the ability to reduce the concentration of arsenic in the aqueous solution from an initial value of 300 μg/L to <10 μg/L (i.e. below the limit value specified by WHO).
Key Words: Arsenic removal, adsorption, layered double hydroxide (LDH), Nanomagnetite, isotherm, kinetic, magnetic seed. |
