Laser-assisted synthesis of metakaolin/Pd nanocomposite and its application as catalyst in wastewater remediation

Abstract

Developing industrial activity and changing climate worldwide increase water contaminants and reduce safe water resources. Therefore, wastewater treatment and the removal or reduction of water contaminants have become important challenges. Affordable nanocatalysts for wastewater treatment are an effective solution to overcome this problem. Fabrication of a new type of metakaolin/Pd nanocomposite (MK/Pd) facilitates the reduction of noxious methyl orange and Cr(VI). This nanocomposite was manufactured based on the deposition of Pd NPs on the MK. In this study, the MK was first synthesized through a one-step heat treatment process at -750 °C for 4 h. Meanwhile, the laser ablation of Pd target in deionized water was also applied as a fast and chemical-free technique to prepare colloidal Pd nanoparticles (NPs). The samples were analyzed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and BET analysis. The structural investigations indicated that MK surfaces with rough platy morphology were decorated with Pd NPs with an average crystallite size of 42 nm. The catalytic performance of the MK/Pd was also investigated for the reduction of methyl orange (MO) and Cr(VI) in an aqueous medium employing sodium borohydride or formic acid. The progress of reactions was monitored using UV–Vis spectroscopy, suggesting that the as-fabricated nanocomposite delivers very rapid reduction of both Cr(VI) (45 s) and MO (400 s). Compared to MO, Cr(VI) reduced ten times faster.