BACKGROUNDOne of the most harmful pollutants to human health present in natural water is arsenic. In this work magnetic silica/magnetite nanoparticles functionalized with aminopropyl groups incorporating Fe3+ (S1-F3) were investigated for their suitability as materials to adsorb As5+ and As3+ from polluted groundwater. RESULTSMagnetite nanoparticles obtained by a co-precipitation method were coated with a mesoporous silica layer generated by hydrolysis and condensation of tetraethyl orthosilicate. The resultant material was grafted with amino derivatives coordinated with Fe3+. The synthesis was confirmed by FT-IR, TGA and BET analyses. After analysis of the affinity of solids with different degrees of functionalization towards arsenate and arsenite species, the material S1-F3 resulted in maximum arsenic adsorption capacities (14.70.3mg As(3+)g(-1) and 121 +/- 4.1mg As(5+)g(-1)). The adsorption equilibrium was satisfactorily described by the Langmuir model and exhibited low sensitivity to temperatures in the range 288-308K. Kinetic data were correlated with a pseudo-second-order kinetic model based on solid capacity that considers the rate of the surface reaction as the rate-limiting step. CONCLUSION

The promising results confirm that the material S1-F3 is an effective adsorbent for the removal of arsenate from polluted water. More research is being conducted to analyse the influence of competing anions and sorbent regeneration. (c) 2014 Society of Chemical Industry.