Removal of aniline using lignin grafted acrylic acid from aqueous solution

Significant adsorption performance of a modified lignin, lignin-graft-acrylic acid (L-g-AA) for aniline removal was investigated through batch experiments. The results showed that L-g-AA possesses strong adsorption ability for aniline with interaction of hydrogen bond and electrostatic interaction. The equilibrium adsorption data was well represented by the Freundlich isotherm model and the saturated adsorption capacity could reach a maximum of 79.1 mg/g at 15 °C. The adsorption process was found to follow pseudo-second-order kinetics. The activation energy (Ea) was found to be 8.09 kJ/mol. Increasing the adsorption temperature would result in lower adsorption capacity. The significant thermodynamic parameters such as Gibbs free energy (ΔG), enthalpy change (ΔH) and entropy change (ΔS) were calculated. The negative value of ΔH and positive value of ΔG show the exothermic and non-spontaneous nature of adsorption respectively. It was also observed that L-g-AA possessed excellent reusability for aniline removal after 8 adsorption–desorption cycles in 0.1 mol/L hydrochloric acid which acted as a desorption medium. The work demonstrates that L-g-AA developed in the present study is a promising sorbent of aniline in water.

• Lignin-graft-acrylic acid as adsorbent for aniline.
• Saturated adsorption capacity could reach a maximum of 79.1 mg/g.
• The recovery is greater than 96% after 8 desorption–adsorption cycles.