Fe(II)-MSA functionalized Au nanoparticle on natural zeolites as effective reducing agent for Cr(VI) ions

Hexavalent chromium (Cr(VI)) ions are typical species found in wastewater released from various industries, e.g. electroplating, leather tanning, and canning industries, which causes serious risks to the environment. Therefore, Cr(VI) ions should be reduced into a less-toxic species, i.e. Cr(III) [1, 2]. This present investigation deals with the preparation of Indonesian natural zeolite (INZ) modified by Au nanoparticles and Fe(II)-mercaptosuccinic acid (MSA) complexes as reducing agents for Cr(VI) to Cr(III) ions. These materials were characterized using XRD, SEM-EDS, UV-Vis DRS, and FTIR. It was revealed that Au nanoparticles play a role as bridging agent of INZ and Fe(II)-MSA. The purpose of this modification is to provide flexible and easily accessible reducing sites, i.e. Fe(II) in heterogeneous system. Therefore, the reducing materials can be easily separated at the end of reaction. The reduction of Cr(VI) ions was indicated by the decay of absorbance at λ_max of 350 nm based on the measurement using UV-Vis Spectrophotometer. The prepared materials could reduce 1.1×10^-4 M Cr(VI) up to 90% at pH of 4.7 for 20 minutes. In this system, Cr(VI) reduction followed a first order reaction rate with the apparent rate constant, k_app, of 0.095 min^-1.