Investigations on the batch performance of cationic dyes adsorption by citric acid modified peanut husk

Abstract

A citric acid modified peanut husk (MPH) was used as adsorbent for removal of neutral red (NR) and methylene blue (MB) from aqueous solution. A batch system was applied to study the behavior of NR and MB adsorption in single and binary systems on MPH. Such studies were conducted by varying various parameters such as the initial dye concentration, the pH, the salt concentration, the temperature, and the contact time. Adsorption kinetic data were fitted using pseudo-first-order equation, pseudo-second-order equation, and intraparticle diffusion model. The process mechanism was found to be complex, consisting of both surface adsorption and pore diffusion. The effective diffusion parameter Di values estimated in the order of 10-8 cm2/s indicated that the intraparticle diffusion was not the rate-controlling step. The NR adsorption isotherm follows the Langmuir model, while MB adsorption follows the Freundlich isotherm. The thermodynamics parameters of adsorption systems indicated spontaneous and endothermic process. In binary system, NR and MB exhibited competitive adsorption. The adsorption of NR or MB is considerably reduced with an increasing concentration of the other. The quantity of MB adsorbed is more strongly by NR due to the higher affinity of MPH for the latter.