Improving the adsorption of arsenic (V) by akaganeite nanoparticles

KAREN GARCÍA TELLEZ; ANA E. TUFO; ELSA E. SILEO; C.A. BARRERO

LIMA

Congreso; XII Latin American Conference of the Application of the Mössbauer Effect. (LACAME); 2010

Improving the adsorption of arsenic (V) by akaganeite nanoparticles The problem of arsenic contamination in water is receiving worldwide attention due to their adverse effects. Of the two valence states of arsenic, arsenite (As III) is the most difficult to remove from water, since this has a charge close to neutral, but it is easily oxidized with agents such as chlorine and others to form arsenate (As V). Previous studies have found that iron oxides can be used as adsorbents for these pollutants. However, among these oxides, akaganeite has been the least studied. The adsorption process involves the interaction of adsorbing species with surface hydroxyl groups of iron oxides. Therefore, the modification of the surface of the particles plays an important role. In the present work, the effect of the substituent and the means of akaganeite synthesis on the adsorption of As (V) was evaluated. The modifications of the physical properties of akaganeite when prepared in the presence of Al and Cu ions and urea when it is obtained by the hydrolysis of FeCl3 solutions were investigated by different techniques. XRD, RT and 77K Mossbauer spectrometry, FTIR and TGA demonstrated that akaganeite is the only compound being formed independent of the type and concentration of the metallic cations and urea. EDS measurements on the solid obtained indicate that the Al content in the samples precipitated is less than 1%, and that the presence of urea modifies the composition and content of Cl. SEM analysis indicates that the presence of Al increases the size of b-FeOOH particles. The micrographs also show that particles are formed by the agglomeration of smaller particles. Very small differences in some of the crystallographic, Mossbauer and infrared parameters for samples obtained in the presence of Cu, and Al ions at concentrations less than 10 mol% nominal, were observed. However at 30 mol% nominal, the presence of Al is able to reduce the average grain size of the final products. The presence of urea does not help to incorporate in an appreciable amount the Al into the akaganeite structure at least in the concentration ranges studied here. In contrast, urea drastically affect the grain size of the products by reducing them. The adsorption kinetics of As (V) was made at pH 4.00 and 25 °C under N2 atmosphere and constant stirring, using a concentration of 40 ppm As. The percentage of As adsorbed followed the following sequence: b-FeOOH < b-(Al,Fe)OOH < b-FeOOH-urea < b-(Al,Fe)OOH-urea. The maximum adsorption was for b-(Al,Fe)OOH- 0.4 M urea. References: K.E. Garcia, C.A. Barrero, A.L. Morales, J.M. Greneche, Materials Chemistry and Physics 112 (2008) 120?126. C.A. Barrero, K.E. García, A.L. Morales, J.M. Greneche, Physica B 389 (2007) 88?93. C.A. Barrero, K. E. Garcia, A.L. Morales, S. Kodjikian and J. M. Greneche, J. Phys.: Condens. Matter 18 (2006) 6827?6840.