Kinetic and Dynamic Aspects of Arsenic Adsorption by Fe(III)-Loaded Sponge

Abstract

Nowadays there is a great concern about new adsorbent materials for either the removal or fixation of arsenic species because of their high toxicity and the health problems associated with such species. In this paper the kinetics of absorption of As(V) on Fe(III)-loaded sponge have been studied and the results are compared with those of other natural and synthetic adsorbents. Arsenate was adsorbed very rapidly by Fe(III)-loaded sponge with saturation being reached in less than ten minutes. Arsenate was also adsorbed by Fe(III)-loaded Lewatit-TP-207 and non-loaded Purolite A100S ion-exchange resins but the times required to reach total saturation of the adsorbent were more than 100 minutes. The experimental data followed first-order kinetics. The extraordinarily superior kinetics are postulated to be related to the open-celled internal structure of the sponge material. The effect of flow rate on the dynamic removal of As(V) was studied in a fixed-bed column reactor for Fe(III)-loaded sponge and Fe(III)-loaded resin. The adsorption of As(V) on fixed-bed columns of adsorbent also indicated better kinetic properties for the sponge. Column studies showed a good correlation between the experimental data and the calculated breakthrough curves obtained by the Wolborska and Clark models. Application of the Wolborska model to the data at low C/C 0 ratios enabled the determination of the kinetic coefficient of mass transfer for the sponge and resin materials at the different flow rates used and gave a good prediction of the 5% breakthrough times. Furthermore, the breakthrough curves were well described by the Clark model at the ratios of concentration of effluent to influent up to 0.5 for the sponge and 0.3 for the Fe(III)-loaded resin. Above these levels, a large deviation occurred for the resin adsorption. Thus, the sponge was found to be kinetically effective and favored for As(V) adsorption from solution over the conventional adsorbents used and for most of the adsorbents reported in the bibliography.