Equilibrium, Kinetic and Thermodynamics Studies of Adsorption of Aniline Blue from Aqueous Media Using Steam-Activated Carbon Prepared from <i>Delonix regia</i> Pod

Abstract

The adsorption capacity of steam activated carbon prepared from Delonix regia pods SADRC for adsorption of Aniline Blue (AB) from aqueous solution was investigated under various experimental conditions. Batch study was conducted to assess the potential of the activated carbon for the removal of Aniline Blue from aqueous solution. Activated carbon prepared from Delonix regia pods was characterized using Scanning Electron Microscope (SEM) and Fourier Transform Infrared (FTIR) Spectrophotometry before and after adsorption. The FTIR, spectra of SADRC pod before and after Aniline Blue adsorption were compared to study the impact of the Aniline Blue on the activated carbon developed from the Delonix regia pod. The stretching vibration band at 2169.54 cm -1 may be due to strong CN, while the stretching vibration band at around 1580 - 1650 cm -1 may be due to C=C stretching vibration. The bands around 1350 and 426.49 cm -1 are due to C-N and –SO 3 H group, respectively; this further suggests that some functional groups may be present on the surface of the carbon due to the low temperature of carbonization (300°C) of the adsorbent. Equilibrium isotherm studies were carried out by varying the following four parameters: initial concentration of Aniline Blue dye solution, solution pH and adsorbent dose. The equilibrium data obtained were more fitted to Langmuir than Freundlich isotherm models. The correlation coefficient value (R 2 ) of the pseudo first order kinetics ranged from 0.08 to 0.85 while the R 2 of the pseudo second order kinetics ranged from 0.963 to 0.997 at all the temperatures and initial concentrations considered. This suggests that the adsorption kinetics of Aniline Blue onto SADRC can be represented with pseudo second order kinetic model. This study showed that Delonix regia pod could be effectively used as an adsorbent for the removal of Aniline Blue from aqueous solutions over a wide range of concentration and temperature.