Adsorption kinetics, isotherm and reusability studies for the removal of cationic dye from aqueous medium using arginine modified activated carbon

In the present work, we have successfully developed 2-amino-5-guanidinopentanoic acid modified activated carbon (AGDPA@AC) for the effective removal of methylene blue (MB) dye from aqueous medium. The AGDPA@AC was characterized using different instrumental techniques viz., SEM, EDX, FTIR, TGA and zeta potential. The influence of different parameters viz. pH, initial MB concentration, contact time and temperature on the adsorption capacity was investigated. The maximum adsorption capacity of MB of on AGDPA@AC was found at pH 8 and 120 min. The maximum Langmuir adsorption capacity of AGDPA@AC was 219.9 mg/g at 25 °C. The adsorption followed Langmuir isotherm and pseudo-second order kinetic models well. The result of thermodynamic data showed that the adsorption was spontaneous and exothermic in nature. The binding of MB dye onto AGDPA@AC surface was through electrostatic interactions. Regeneration studies indicated that the adsorbent could successfully retain MB, even after four cycles. The adsorption percent of AGDPA@AC for MB dye was 75% even after four adsorption-desorption cycles.