Magnetic lignin-based carbon nanoparticles and the adsorption for removal of methyl orange

Among the available biomass materials, lignin is the second most abundant. Due to its high carbon content, it is widely used in developing materials used in numerous application such as sensors and supercapacitors. Recent studies show low utilization of lignin materials especially in households as energy sources rather than commercial applications. This has resulted in a great waste of lignin materials.  As such, enhancing the commercial applications of lignin is highly desirable. Alternatively, polymer functionalized magnetic materials have attracted significant attention of scientists owing to their effectiveness. Presently, several functionalization methods such as adsorption and indirect modification have been developed for magnetic materials. Unfortunately, they are limited to some extent thus insufficient for numerous applications. Therefore, researchers have been looking for alternatives and have identified lignin-based magnetic carbon nanomaterials as a promising solution.

To this note, South China University of Technology scientists: Dr. Ying-zhi Ma, Dr. Da-feng Zheng, Dr. Zhen-ye Mo, Rui-jing Dong and Professor Xue-qing Qiu from the College of Chemistry and Chemical Engineering synthesized the magnetic lignin based on the carbon nanoparticles. Fundamentally, the synthesize was based on precipitation and carbonization techniques. Specifically, they further investigated whether the prepared magnetic lignin-based carbon nanoparticles were suitable for application as a methyl orange adsorbent. Their main aim was to promote the use of lignin in different commercial applications. Their research work is currently published in the research journal, Colloids and Surfaces A: Physicochemical and Engineering Aspects.

Briefly, Dr. Da-feng Zheng and his colleagues commenced their experimental work by coating the lignin material on an iron oxide surface through precipitation method. Next, magnetic carbon nanoparticles were produced by calcinating the resulting lignin-iron oxide at high temperatures. Additionally, several methods including FTIR, X-ray diffraction among others were used to validate and characterize its properties such as the structures, magnetism, and morphology. Eventually, they actualized their study by comparing the adsorption of the magnetic lignin-based carbon nanoparticles for methyl orange to those obtained in the initially developed pseudo-second order and Langmuir models.

The authors observed that the adsorption of methyl orange in magnetic lignin-based carbon nanoparticles was similar to that observed in Langmuir and pseudo-second-order models. For instance, the resulting monolayer adsorption exhibited the highest adsorption capacity standing at 113.0mg/g. Furthermore, it was worth noting that it was possible to adsorb methyl orange at ambient conditions especially at a temperature below 35⁰C. This was attributed to the fact that the adsorption process was an exothermic and entropy reduction process. Although the adsorption process was much more efficient in acidic conditions, it could still be supported in an almost neutral environment.

In summary, the South China University of Technology scientists successfully demonstrated the effectiveness of magnetic lignin-based carbon nanoparticles as an efficient adsorbent. Apart from being suitable for both acidic and neutral conditions, it can be easily regenerated thus will ensure effective utilization of natural resources for sustainable development. Altogether, the study will advance the development of more efficient adsorbents suitable for industrial and household application like dye removal from waste effluents.