Adsorption of humic acid by amine-modified nanocellulose: an experimental and simulation study

The purpose of this study was to evaluate the adsorption of humic acid (HA) by amine-modified nanocellulose. At first, nanocellulose was synthesized by acid hydrolysis, and then was modified by N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane. In the next step, HA and amine-modified nanocellulose were incubated at different conditions (pH, incubation time, temperature, and concentration). Furthermore, we used molecular dynamic (MD) simulation for observation of adsorption at molecular scale. For this purpose, HA and amine-modified nanocellulose were prepared by HyperChem software (Hypercube, Inc., USA), and inserted in Ascalaph Designer 1.8.69 software. Once equilibrium was reached, interactions were simulated for 1,000 ps. Finally, different parameters such as interaction energy, potential energy, and root-mean-square displacement (RMSD) were measured. This study demonstrated that the adsorption of HA was pH-, temperature-, dose-, and time-dependent. Based on simulation results, the interaction energy was reduced, but potential energy and RMSD were increased at the final stage of simulation, which indicated the adsorption of HA. The authors suggest amine-modified nanocellulose for removal of HA in wastewater.