Removal of Congo red from aqueous solution by adsorption onto different amine compounds modified sugarcane bagasse

Different amine compounds, including ethylenediamine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine, modified sugarcane bagasse (SCB) were prepared to improve its adsorption capacity for anionic dye Congo red. Batch studies were carried out to investigate the effect of various parameters including surface nitrogen content, the amine compounds chain length, contact time, initial concentration, solution pH and salt on the adsorption of Congo red. Results showed that the adsorption capacity of the sorbents did not increase consistently with the increase in the surface nitrogen content, and it varies in the order: unmodified < ethylenediamine-modified < diethylenetriamine-modified ≈ triethylenetetramine-modified ≈ tetraethylenepentamine-modified sugarcane bagasse. The diethylenetriamine-modified sorbent had similar capacity with the triethylenetetramine- and tetraethylenepentamine-modified sorbent. The adsorption mechanism based on electrostatic attraction and steric hindrance was proposed. pH and salt experiment illustrated that the prepared sorbents could be used in a wide pH range (5.0–12.0) and a high-salinity environment (1.0 mol L⁻¹). Dynamic adsorption of Congo red on tetraethylenepentamine-modified SCB fixed-bed column showed that breakthrough time and saturated time were 364 and 1109 min, respectively. The modified SCB could be regenerated efficiently and used repeatedly. It had great potential in the real wastewater treatment.