Carbonized lignosulfonate-based porous nanocomposites for adsorption of environmental contaminants

Jenevieve Yao,Karin Odelius,Minna Hakkarainen

doi:10.1186/s42252-020-00008-8

Jenevieve Yao, Karin Odelius + Show 1 more

Open Access

https://doi.org/10.1186/s42252-020-00008-8

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Abstract

Carbon-based adsorbents possess exceptional adsorption capability, making them an ideal platform for the remediation of environmental contaminants. Here, we demonstrate carbonized lignosulfonate (LS)-based porous nanocomposites with excellent adsorption performance towards heavy metal ions and cationic dye pollutants. Through microwave-assisted hydrothermal carbonization, a green approach was employed to carbonize lignosulfonate to carbon spheres. The LS-derived carbon spheres were then oxidized into nanographene oxide (nGO) carbon dots. A facile two-step procedure that involved the self-assembly of nGO and gelatin into a hydrogel precursor coupled with freeze-drying enabled the construction of three-dimensional (3D) free-standing porous composites without the use of organic solvents or chemical crosslinking agents. The favorable pore structure and abundance of surface functional groups on the nGO/gelatin porous composite proved to substantially facilitate the adsorption of Cu(II) in comparison to conventionally-used activated carbon. Further enhancement of adsorption performance was achieved by introducing additional surface functional groups through a non-covalent functionalization of the porous composite with lignosulfonate. The presence of negatively-charged sulfonate groups increased the Cu(II) equilibrium adsorption capacity (66 mg/g) by 24% in comparison to the non-functionalized nGO/gelatin counterpart. Both functionalized and non-functionalized composites exhibited significantly faster adsorption rates (40 min) compared to many graphene- or GO-based adsorbents reported in literature. In addition to the adsorption of heavy metal ions, the composites also demonstrated good adsorption capacity towards cationic dyes such as methylene blue. This paves the way for a high value-added application of lignin in environmental remediation and opens up new possibilities for the development of sustainable materials for adsorption and water purification.

Highlights

Graphene oxide (GO)-based materials are highly effective adsorbents for environmental remediation, but their widespread use is hindered by the high cost involved in GO synthesis
Porous nanographene oxide/gelatin nanocomposites were developed by a self-assembly strategy utilizing lignosulfonate-derived carbon products as building blocks
100% of the composite is reclaimed after the Conclusions Free-standing three-dimensional (3D) lignin-derived porous nanographene oxide (nGO)-based nanocomposites with excellent adsorption capacity for heavy metal ions and cationic dyes were successfully designed. nGO was derived through a two-step reaction, including carbonization and oxidation of lignosulfonate

Summary

Introduction

Graphene oxide (GO)-based materials are highly effective adsorbents for environmental remediation, but their widespread use is hindered by the high cost involved in GO synthesis. To further enhance the adsorption performance of the composites, additional active sites for adsorption in the form of negatively-charged sulfonate groups are introduced via non-covalent functionalization with lignosulfonate. Characterization of LS-derived carbon products and LSfunctionalized nGO/gelatin composites Apparent porosity was determined using Eq 1, where M1 is the mass of the dry sample, M2 is the mass of the saturated sample after immersion in deionized water, ρ is the density of water, and V is the volume of the saturated sample.

Results

Conclusion