Kinetics, isotherms, and mechanism of Cr(VI) adsorption by polyaniline/sunflower stem pith composite adsorbent

In the present study, a polyaniline/sunflower stem pith (PANI/SSP) composite was synthesized using in situ polymerization and used as an adsorbent for the detoxification of Cr(VI) from sewage. The work involved batch experiments to investigate the effect of operating parameters such as contact time, pH, temperature, adsorbent dosage, and initial concentration of Cr(VI) on the extent of adsorption by PANI/SSP. The composite was characterized by ATR-FTIR, SEM, TEM, TG-DTG, and XPS. The adsorption process followed the Langmuir isotherm model, and the calculated saturated adsorption amounts obtained from the model ranged from 27.73 to 42.96 mg/g with temperature increasing from 298 to 338 K. Kinetic studies demonstrated that the pseudo second order model is able to provide a realistic description of the adsorption kinetics. A thermodynamic analysis indicated that the removal of Cr(VI) by PANI/SSP is endothermic (Delta H-O = 37.38 KJ/mol). The regenerated PANI/SSP can be reused successfully for four successive adsorption-desorption cycles. Hence, we conclude that PANI/SSP can be used as an adsorbent for the detoxification of Cr(VI)-contaminated water.