Enhanced removal of humic acids (HAs) from aqueous solutions using MWCNTs modified by N-(3-nitro-benzylidene)-N-trimethoxysilylpropyl-ethane-1,2-diamine on Equilibrium, thermodynamic and kinetics

In this study, multi-walled carbon nanotubes modified by N-(3-nitro-benzylidene)-N-trimethoxysilylpropyl-ethane-1, 2-diamine (NBATSPED-MWCNTs) was prepared as a low-cost and non-toxic adsorbent. These  materials was characterized by different techniques such as SEM, XRD and FT-IR and subsequently was used for the removal of humic acids (HAs) from aqueous solution. The influence of various operational parameters such as pH, initial (HAs) concentration and contact time in batch systems was investigated on the use of NBATSPED-MWCNTs. The kinetic results demonstrated that the pseudo-second- order equation is the best model to analyze the adsorption mechanism. The isotherm analysis showed that the equilibrium data are well fitted to the Langmuir isotherm model with maximum adsorption capacities of 12.5 mg g-1 of the adsorbent for removal of HAs. The overall adsorption process was exothermic and spontaneous in nature. The thermodynamic functions (ΔSº, ΔHº, ΔGº) of the studied reaction are calculated using activated complex theory and show that adsorption(HAs) onto (NBATSPED-MWCNT) process requires heat.