Physicochemical characterization of Pakistani clay for adsorption of methylene blue: Kinetic, isotherm and thermodynamic study

This study focuses on the investigation and characterization for adsorption property of the clay sample collected from river Kasho of district Bannu, Khyber Pakhtunkhwa, Pakistan. The as received clay was investigated via a series of characterization techniques such as XRD, TG-DSC, XRF, FT-IR and SEM-EDS. The characterization of raw sample revealed the presence of clay as well as non-clay accessory minerals. In this study, low cost adsorbent (clay) used for the removal of a cationic dye (methylene blue) as the model pollutant from aqueous solution. For adsorption performance, batch adsorption technique was utilized at various conditions such as initial dye concentration (50–300 mg/L), contact time (10–380 min), solution pH (2–10), and temperature (25–45 °C). Kinetic study exhibited that experimental data were fitted well Pseudo second order (PSO) model and intra-particle diffusion (IPD) as the rate determining step. Equilibrium isotherm data were described well using Langmuir model by giving a maximum capacity of adsorption (qm= 270 mg/g). Thermodynamic study exhibited that the adsorption process shows spontaneity. The results indicate that the clay could be employed in waste-water treatment for the removal of cationic pollutants and dyes.