Tunable synthesis of polyethylene polyamine modified lignin and application for efficient adsorption of Fe2+ in super acid system

Lignin-Based Platform as a Potential Low-Cost Sorbent for the Direct Air Capture of CO2

The urgent need to address the current climate crisis has led to concerted efforts to develop low-cost and sustainable methods to remove carbon dioxide from the atmosphere. Carbon capture and storage (CCS) and negative emissions technologies (NET's) offer the most promising paths forward to offsetting global emissions. In this study, we explore the potential of kraft lignin, a readily available biomaterial, as a low-cost alternative for the development of a CO2 sorbent. The approach leverages the known ability of amines to reacting with carbon dioxide and forming a stable compound. Commercially available kraft lignin was modified with diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA) using a one-pot synthesis approach via the Mannich reaction. The sorbent was evaluated for porosity, accessible amine density, and nitrogen content. The CO2 capture experiments revealed that the resulting sorbent can capture 0.80 (±0.03) mmol of CO2 per gram of sorbent.

Influence of structure and functional group of modified kraft lignin on adsorption behavior of dye

Utilization of kraft lignin to produce bio-based adsorptive material for effective dye adsorption from industrial wastewater is essential to fulfilling the significant environmental protection needs. Lignin is the most abundant byproduct material with a chemical structure containing various functional groups. However, the complicated chemical structure makes it somewhat hydrophobic and incompatible, which limits its direct application as an adsorption material. Chemical modification is a common way to enhance lignin properties. In this work, the kraft lignin was modified through direct amination using Mannich reaction and oxidization followed by amination as new route of lignin modification. The prepared lignins, including aminated lignin (AL), oxidized lignin (OL), and aminated-oxidized lignin (AOL), as well as unmodified kraft lignin, were analyzed by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), elemental analysis and ¹H-nuclear magnetic resonance measurements (¹HNMR). The adsorption behaviors of modified lignins for the malachite green in aqueous solution were investigated well and discussed, as well as the adsorption kinetics and thermodynamic equations. Compared with other aminated lignin (AL), the AOL displayed a high adsorption capacity of 99.1 % dye removal, due to its more effective functional groups. The change in structure and functional groups on the lignin molecules during oxidation and amination had no effect on its adsorption mechanisms. The adsorption process of malachite green on different kinds of lignin belongs to endothermic chemical adsorption, which mainly consists of monolayer adsorption. The modification of lignin through oxidation followed by amination process, afforded kraft lignin a broad potential application in the field of wastewater treatment.

Steel slag as a potential adsorbent for efficient removal of Fe(II) from simulated acid mine drainage: adsorption performance and mechanism

Acid mine drainage is an extraordinarily acidic and highly heavy metal ion-contaminated leachate, seriously threatening the environment. In this work, an industrial solid waste of steel slag is the adsorbent to remediate the simulated acid mine drainage containing a large amount of Fe(II) ions. Due to the excellent physicochemical properties and structures, steel slag exhibited remarkable Fe(II) removal performance. Its maximum removal efficiency was up to 100%. The initial pH, the dosage and particle size of steel slag, and initial concentration of heavy metal ions on Fe(II) removal efficiency were determined. The pseudo-second-order model and Freundlich isotherm model well described the adsorption behavior of steel slag, implying that the adsorption of Fe(II) by steel slag was mainly multilayer chemisorption. The thermodynamic study demonstrated that the adsorption process was endothermic and spontaneous; the enthalpy change was calculated to equal 91.21 kJ/mol. Mechanism study showed that the entire removal process of Fe(II) by steel slag was completed by electrostatic adsorption, chemical precipitation, and surface complexation in cooperation, and the chemical precipitation was the dominant mechanism. Meaningfully, this study provides a valuable strategy and path for engineering applications of AMD remediation by steel slag, which is prospective as an ideal candidate for Fe(II) ions elimination, inspiring the future development of "Treating the wastes with wastes."