A high-performance
modified lignin adsorbent was prepared through
coprecipitation of ferrous, ferric, and permanganate with lignin in
sodium hydroxide solution. The structural characteristics of the synthesized
lignin-Fe/Mn binary oxide blend nanocomposite (L-F/M) and its performance
on the methylene blue (MB) removal from aqueous solution were evaluated.
Influence factors of adsorption effects were analyzed including pH,
contact time, dye concentration, temperature, and thermodynamics.
The pseudo-second-order kinetic model well described the adsorption
kinetics, and the adsorption isotherms best fitted the Langmuir model
with a maximum adsorption capacity of 252.05 mg g–1 at 298 K. The adsorption mechanism showed that the L-F/M introduced
the metallic element and negative charges to the lignin surface, which
improved the adherence of MB via hydrogen bonding, electrostatic interaction,
and coordination. Moreover, the removal ratio of MB maintained 81.2%
after being used in five adsorption–desorption cycles. Results
indicated that the L-F/M obtained was an efficient candidate for dye
wastewater treatment.