Nitrilotriacetic acid modified bamboo charcoal (NTA-MBC): An effective adsorbent for the removal of Cr (III) and Cr (VI) from aqueous solution

Abstract

In the present study, nitrilotriacetic acid (NTA) was used as a chelating agent for surface modification of bamboo charcoal (BC). Nitrilotriacetic acid modified bamboo charcoal (NTA-MBC) was applied as an adsorbent for the removal of trivalent and hexavalent chromium from aqueous solution. Batch mode adsorption studies were performed using various parameters such as pH, contact time, adsorbent dose, initial metal ion concentration and temperature. The adsorption data were analyzed using Langmuir, Freundlich and Temkin isotherms. Maximum adsorption capacity of NTA-MBC obtained from Langmuir isotherm was found to be 1000 mg/g for Cr (III) at pH 3 with adsorbent dose of 1 g/l and 270 mg/g for Cr (VI) at pH 3 with adsorbent dose of 2 g/l. Thermodynamic studies of adsorption of both Cr (III) and Cr (VI) indicated that the nature of adsorption process was spontaneous and endothermic in nature. Enhanced adsorption capacity of NTA-MBC can be attributed to the formation of 1:1 or 1:2 complexes by NTA present on the surface of bamboo charcoal with Cr (III) and Cr (VI) in aqueous solution. The adsorption phenomenon was observed to follow pseudo second order kinetics model. The surface characteristics of NTA-MBC were examined using SEM, BET and FT-IR. The NTA-MBC was also examined for its application in purification of water through the column studies and observed to be a promising material for packing of columns in water treatment plants.