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 GO-MLNPs 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.