Effective removal of Antimony from aqueous solution using Forager Sponge® and SPION-loaded onto Forager Sponge®

There is a growing interest in antimony (Sb) recovery due to the fact that over 90% of the supplies of this metalloid comes from China, so the European Union and EE.UU are import-dependent of this product. Furthermore, antimony is also a non-desirable product in copper refining processes, creating important problems in the electrorefining plants. Therefore, Sb recovery is essential to the proper treatment of copper ores, and for the production of flame retardants, plastic and semiconductor in the European industry. New materials based on nanoparticles have been developed with the main objective of improving Sb sorption capacity and make possible its effective recovery. The system that has been used in this work is based on SuperParamagnetic Iron Oxide Nanoparticles (SPION) onto a Forager sponge®. This sponge is an open-celled cellulose sponge with weak amine groups, which is able to effectively remove different metals in a selective manner from solutions. The advantages of the use of this sponge are well known, so to enhance its sorption capacity and its selectivity, SPION has been loaded on the sponge, which has been shown as an appropriate system to heavy metals sorption. The aim of the present work is to evaluate the sorption capacity of Sb, as Sb(III) and Sb(V), in the Forager sponge® and in the SPION-Forager sponge® systems and their possible application to the recovery and removal of this metalloid in the best selective way from wastewater. Different SPION synthesis pathways for its proper loading onto the Forager sponge® have been checked. In order to evaluate the sorption capacity kinetic and isotherms, studies have been performed. Afterwards, different batch experiments were run to compare both adsorption material systems, and to determine the influence of the aqueous antimony speciation. So, 25 mg of each adsorbent material were agitated in the presence of 2.5 mL of Sb(III) and/or Sb(V) synthetic solutions at pH 5. At this pH, the Sb(III) is dissolved in its corresponding neutral form, Sb(OH)3, and Sb(V) is present in its anionic form, Sb(OH)6-. Preliminary results show that the presence of SPION in the sponge change the selectivity of this material, increasing the adsorption capacity from 31 to 40 mg of Sb/g of the adsorbent for Sb(V). On the contrary, Sb(III) decrease its adsorption capacity from 40 to 30 mg of Sb/g of adsorbent. Different electrical surface characteristics of both sponges can give such differences on their behavior onto Sb(III) and Sb(V) separation, giving some different selectivity depending if using the original sponge or the SPION-loaded one.