Preparation of functionalized magnetic graphene oxide/lignin composite nanoparticles for adsorption of heavy metal ions and reuse as electromagnetic wave absorbers

Graphene oxide/magnetic lignin-based nanoparticles (GO-MLNPs) were successfully prepared for adsorbing heavy metal ions. Then the spent adsorbents (M2+@GO-MLNPs) were unprecedentedly applied as efficient electromagnetic wave absorption (EMWA) materials. The structures and performances of the prepared GOMLNPs were comprehensively characterized with various analytical methods. Adsorption experiments were studied in detail to identify the influence of various factors. The maximum adsorption capacities (Qmax) of Pb2+ and Ni2+ ions would be up to 147.88 and 110.25 mg/g, respectively. Notably, the adsorption rate could be maintained over 85% after 5 sorption-desorption cycles. After the adsorption, in order to reduce the secondary pollution, the spent adsorbents were recycled as novel EMWA materials via carbonization process (M2+@GO-CMLNPs). Surprisingly, the reflection loss (RL) of Ni2+@GO-CMLNPs reached-39.2 dB at 4.56 GHz under the thickness of 5.0 mm. In short, the low-cost and renewable GO-MLNPs not only have the large adsorption capacity of heavy metal ions but also can be reused after adsorption process as efficient electromagnetic wave (EMW) absorbers.

Automated summary

Graphene oxide/magnetic lignin-based nanoparticles were prepared and used for adsorbing heavy metal ions, and also applied as efficient electromagnetic wave absorption materials. The maximum adsorption capacities of Pb2+ and Ni2+ ions were found to be high, and the adsorption rate could be maintained even after multiple cycles. The spent adsorbents were recycled and utilized as electromagnetic wave absorbers through carbonization process. The reflection loss of Ni2+@GO-CMLNPs was remarkably high at 4.56 GHz.