Poly(dopamine) grafted bio-silica composite with tetraethylenepentamine ligands for enhanced adsorption of pollutants

Abstract In this study, diatomite fossil particles (i.e., bio-silica) was treated with strong acid solution and coated with polydopamine (bio-silica-PDA) using aqueous-based bioinspired coating method. The bio-silica-PDA was grafted with tetraethylenepentamine (TEPA) ligand to increase binding sites on the material surfaces. The biosilica-PDA-TEPA particles was characterized using Fourier-transform infrared spectroscopy (FTIR), Scanning electron microscope (SEM), X-Ray Diffraction (XRD) and Brunauer–Emmett–Teller (BET) method. The adsorption performance of the biosilica-PDA-TEPA particles was studied using a model dye (i.e., Direct Blue 74; DB-74) from aqueous solutions using biosilica-PDA as a control system. Batch system was used to optimize experimental conditions for the removal of DB-74 dye on the sorbents. The adsorption of DB-74 on the biosilica-PDA-TEPA particles was studied in the pH range of 2.0–8.0. The amount adsorbed DB-74 dye on the biosilica-PDA-TEPA was 363.3 mg g −1 (using initial dye concentration 1200 mg L −1 , pH 3.0 and temperature 25 °C). Adsorption of DB-74 dye on biosilica-PDA-TEPA particles fitted well Langmuir model. The equilibrium adsorption time was completed within 10 min and the experimental data was defined well by the pseudo-second-order model. In addition, the biosilica-PDA-TEPA particles presented a good performance after regeneration. This result show that the presented low-cost porous biosilica-PDA-TEPA particles can be a good candidate as a novel sorbent system for removal of micro-pollutants from wastewaters.