Environmental pollution is a severe and challenging problem all over the world because of the rapid progress in science, technology and industries. The presence of metallic ions in water is of great concern because these pollutants are hazardous to ecosystem due to their high toxicity, nonbiodegradability and their accumulation in the biosphere. In the present study the potential of unmodified leaves of Ficus benghalensis (Fb) and nitrilotriacetic acid modified leaves of Ficus benghalensis (FbNTA) as green adsorbent for removal of chromium [Cr (VI)] from aqueous solution was investigated. The equilibrium studies were systematically carried out in a batch process which covered various process parameters such as effect of pH, contact time, temperature, adsorbent dose, agitation rate and initial ion concentration of Cr (VI). The adsorption isotherm study showed that Langmuir model (R2 = 0.9802) for unmodified green adsorbent and Freundlich model (R2 = 0.9997) for NTA modified green adsorbent provides an appropriate description of metal ion sorption process. The adsorption kinetics was found to follow pseudo-second-order rate kinetic model for modified and unmodified green adsorbent. Thermodynamic study revealed that the biosorption process for removal of Cr (VI) by using Fb was endothermic, non-spontaneous and proceeded with increased randomness whereas by using FbNTA it was endothermic, spontaneous and proceeded with increased randomness. All the experimental results revealed that NTA modification enhanced the adsorption capacity of leaves of Ficus benghalensis due to the chelating ability of NTA thus suitable for Cr (VI) removal from aqueous condition.
