Synthesis of lignin- amine from the waste of pilot plant bioethanol as a green bioadsorbent for lead removal

The investigation of bio-liquid fuels as a sustainable fuel has garnered significant attention. However, because of high production cost, other co-products need to be investigated. The pretreatment process of second-generation (2G) bioethanol produces black liquor that contains lignin. In this paper, we report a direct bubbling and a two-step acidification process for lignin isolation from black liquor of the pilot scale bioethanol production and its utilization as lead adsorber. This research investigated how Pb (II) ions adsorbed onto new modified lignin recovered from black liquor called dimethylamine-soda lignin. Alkaline pretreatment at 150 °C and 5 kg/cm³ by using a 450 L reactor was used to extract the lignin from oil palm (Elaeis guineensis) empty fruit bunches (OPEFB). The acidic precipitation was achieved by adding 3% HCl until the pH reached 2, and the air bubbling was done at a rate of 2 L/min. By applying dimethylamine-acetone-formaldehyde to soda lignin in the Mannich reaction, lignin derivative was produced. The Fourier-transform infrared spectroscopy, scanning electron microscopy, and Brunauer, Emmett, and Teller methods were used to characterize all types of lignin. The analyses confirmed the formation of dimethylamine-lignin, as indicated by a 19-fold increase in the total nitrogen content in the modified lignin. Pb (II) adsorption was verified by pseudo-first-order and second-order reactions. Dimethylamine-soda lignin had the adsorption capability for lignin extracted from acid and the air bubbling technique, 6.0 and 6.8 mg/g, respectively. The outcomes demonstrate that the eco-friendly aminated lignin can effectively lower Pb (II) in the solution, making it a suitable adsorbent for removing lead from aqueous media.

Graphical abstract