From Waste to Biosorbent: Removal of Congo Red from Water by Waste Wood Biomass

The aim of the study was to screen the waste wood biomass of 10 wood species as biosorbents for synthetic dye Congo Red (CR) removal from water and to single out the most efficient species for further batch biosorption experiments. Euroamerican poplar (EP), the most efficient species achieving 71.8% CR removal and biosorption capacity of 3.3 mg g−1, was characterized by field emission scanning electron microscopy (FE-SEM) and Fourier transform infrared spectroscopy (FTIR). Different factors affecting the biosorption process were investigated: initial biosorbent concentration (1–10 g dm−3), contact time (5–360 min), initial CR concentration (10–100 mg dm−3), and the initial pH (pH = 4–9). The results showed that CR removal efficiency increased with the increase of biosorbent concentration and contact time. Increase of initial CR concentration led to an increase of the biosorption capacity, but also a decrease of CR removal efficiency. The highest CR removal efficiency was achieved at pH = 4, while at pH = 9 a significant decrease was noticed. The percentage of CR removal from synthetic wastewater was 18.6% higher than from model CR solution. The Langmuir model fitted well the biosorption data, with the maximum biosorption capacity of 8 mg g−1. The kinetics data were found to conform to the pseudo-second-order kinetics model.