Adsorption of methyl red on activated carbon derived from custard apple (Annona squamosa) fruit shell: Equilibrium isotherm and kinetic studies
Abstract Activated carbon prepared from custard apple (Annona squamosa) shell by K2CO3 (ACCO3) and H3PO4 (ACPO4) activation were used to study the removal of methyl red (MR) from aqueous medium. The BET surface area, pore volume and pore size of the ACCO3 was 431.3 m2/g, 0.054 cm3/g and 21.63 A and that of ACPO4 was 1065.0, 0.269 cm3/g and 31.91 A, suggesting mesoporous nature of the activated carbons. The FT IR spectra established the occurrence of COOH and OH functional groups. SEM images suggested porous and heterogeneous surface. The contact time, adsorbent dose, initial concentration of MR, initial solution pH and temperature were optimized by batch method. The isotherm modeling of the adsorption data over the concentration range (80 130 mg/L) at 303, 313 and 323 K was performed using non linear regression analysis. The data best described by Langmuir isotherm over the entire concentration range. The negative DGdeg and positive DHdeg values indicated spontaneous and endothermic adsorption process. The kinetic modeling revealed that the experimental data followed the pseudo first order and pseudo second order rate equations for ACPO4 and ACCO3, respectively.