Preparation of Lignin-Based Magnetic Adsorbent From Kraft Lignin for Adsorbing the Congo Red

Advances in lignin-based biosorbents for sustainable wastewater treatment

The heavy metals, pesticides and dyes in agriculture and industry caused serious water pollution have increased the urgency for the advancement of biomass-based adsorbents due to their merits of low cost, high efficiency, and environmental sustainability. Thus, this review systematically examines the recent progress of lignin-based adsorbents dedicated to wastewater purification. Commencing with a succinct exposition on the intricate structure and prevalent forms of lignin, the review proceeds to expound rational design strategies tailored for lignin-based adsorbents coupled with adsorption mechanisms and regeneration methods. Emphasis is placed on the potential industrial applications of lignin-based adsorbents, accentuating their capacity for recovery and direct utilization post-use. The future challenges and outlooks associated with lignin-based adsorbents are discussed to provide novel perspectives for the development of high-performance and sustainable biosorbents, facilitating the effective removal of pollutants and the value-added utilization of resources in a sustainable manner.

In-situ preparation of lignin/Fe3O4 magnetic spheres as bifunctional material for the efficient removal of metal ions and methylene blue

In this paper, magnetic composite of lignin/Fe3O4 spheres were synthesized via a straightforward one-step in-situ solvothermal method showing good capacity for adsorbing heavy metal ions and dyes. The physicochemical properties of lignin/Fe3O4 spheres are analyzed using a range of techniques such as SEM, XRD, FTIR, VSM, TG, and BET. Lignin/Fe3O4 spheres exhibited high adsorption capacities of 100.00, 353.36 and 223.71 and 180.18 mg/g for Cu (II), Ni (II) and Cr (VI) metal ions and methylene blue (MB) with equilibrium attained within 60 min. After the recycling experiments, lignin/Fe3O4 spheres still possesses excellent superparamagnetic properties and displays high adsorption capacity. The lignin/Fe3O4 spheres are an efficient and continuous adsorbent to remove heavy metal ions of Cu (II), Ni (II), Cr (VI) and cationic dyes of methylene blue in wastewater, which proves the great potential in practical pollutants treatment applications for water systems.

Adsorption Studies on the Removal of Anionic and Cationic Dyes from Aqueous Solutions Using Discarded Masks and Lignin

The carbon materials derived from discarded masks and lignin are used as adsorbent to remove two types of reactive dyes present in textile wastewater: anionic and cationic. This paper introduces the results of batch experiments where Congo red (CR) and Malachite green (MG) are removed from wastewater onto the carbon material. The relationship between adsorption time, initial concentration, temperature and pH value of reactive dyes was investigated by batch experiments. It is discovered that pH 5.0-7.0 leads to the maximum effectiveness of CR and MG removal. The equilibrium adsorption capacities of CR and MG are found to be 232.02 and 352.11 mg/g, respectively. The adsorption processes of CR and MG are consistent with the Freundlich and Langmuir adsorption models, respectively. The thermodynamic processing of the adsorption data reveals the exothermic properties of the adsorption of both dyes. The results show that the dye uptake processes follow secondary kinetics. The primary adsorption mechanisms of MG and CR dyes on sulfonated discarded masks and alkaline lignin (DMAL) include pore filling, electrostatic attraction, π-π interactions and the synergistic interactions between the sulphate and the dyes. The synthesized DMAL with high adsorption efficiency is promising as an effective recyclable adsorbent for adsorbing dyes, especially MG dyes, from wastewater.

Low Molar Mass Dextran: One-Step Synthesis With Dextransucrase by Site-Directed Mutagenesis and its Potential of Iron-Loading

Iron dextran is a common anti-anemia drug, and it requires low molar mass dextran as substrate. In this work, we selected 11 amino acid residues in domain A/B of DSR-MΔ2 within a 5-angstrom distance from sucrose for site-directed mutagenesis by molecular docking. Mutation of Q634 did not affect the enzyme catalytic activity, but showed an obvious impact on the ratio of low molecular weight dextran (L-dextran, 3,000–5,000 Da) and relatively higher molecular weight dextran (H-dextran, around 10,000 Da). L-dextran was the main product synthesized by DSR-MΔ2 Q634A, and its average molecular weight was 3,951 Da with a polydispersity index <1.3. The structural characterization of this homopolysaccharide revealed that it was a dextran, with 86.0% α(1→6) and 14.0% α(1→4) glycosidic linkages. Moreover, L-dextran was oxidized with NaOH and chelated with ferric trichloride, and an OL-dextran-iron complex was synthesized with a high iron-loading potential of 33.5% (w/w). Altogether, mutation of amino acids near the sucrose binding site of dextransucrase can affect the chain elongation process, making it possible to modulate dextran size.