Preparation of activated carbon/chitosan/Carica papaya seeds composite for efficient adsorption of cationic dye from aqueous solution

Abstract

In this study, activated carbon/chitosan/Carica papaya seeds (CHASPAC) composite was prepared by coating chitosan (CH) with activated carbon (AC) and Carica papaya seeds (ASP). The composite was characterized by IRFT, XRD, ATD/DTG and SEM, and then used as adsorbent for methylene blue (MB). Kinetic studies revealed that the pseudo-second-order and Elovich models were better described the adsorption process than the pseudo-first-order kinetic model. The equilibrium data were best agreeing with the Langmuir isotherm. The maximum adsorption capacity of CHASPAC 302.01 mg g−1 at pH=8 and at 30°C was higher than 93.97, 196.36 and 233.74 mg g−1 determined for CH, AC and ASP respectively. Thermodynamic study indicated favorable and spontaneous process with enthalpy 1.217 kJ mol−1 and entropy 132.544 J mol−1 K−1, suggesting endothermic process and increase in disorder at solid-liquid interface. Regeneration study of composite revealed the adsorption efficiency greater than 90% after five adsorption/desorption cycles attempted, hence, CHASPAC composite has a great reuse potential and could be used as efficient adsorbent for dyes removal from wastewater.