Preparation of Au Nanoparticle Loaded Biochar/Polydopamine Composites for Adsorption of MB and MG Dyes from Aqueous Solution

Au nanoparticles loaded on biochar (PDA-BC/Au) was prepared using adhesion and reduction properties of polydopamine by in-situ reduction method. PDA-BC/Au was characterized by the specific surface area analyzer (BET), the scanning electron microscope (SEM), the transmission electron microscopy (TEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrometry (FTIR). Analysis results prove the successful synthesis of composites decorated with Au nanoparticles in the biochar matrix coating with polydopamine layer. PDA-BC/Au was employed as an adsorbent to remove the cationic dyes (MB and MG) from aqueous solution. The tests confirm that PDA-BC/Au can remove up to 99.0% of MB within 30 min and achieve removal rate over 97.2% of MG after 60 min adsorption. Adsorption kinetics and isotherm models reflect that the adsorption of dyes by PDA-BC/Au has a better fit with pseudo-secondary kinetic equation and the Langmuir adsorption model, displaying chemisorption-dominated single-molecule layer adsorption mechanism. Additionally, after five recycling cycles, the removal rates of PDA-BC/Au for MB and MG only dropped by 3.10 and 2.58% respectively, making clear good stability for long term use. Collectively, the developed PDA-BC/Au adsorbent indicates enormous promise for cationic dye removal and efficient utilization of waste biomass resources.