Adsorption of Chromium(VI) from Aqueous Solutions Using an Imidazole Functionalized Adsorbent

Abstract

Separation of chromium(VI) from aqueous solutions is investigated using an imidazole functionalized sol−gel adsorbent. This adsorbent has been formed by the sol−gel synthesis method. The speciation diagram of Cr(VI) in an aqueous system with varying pH is studied by analyses of the equilibria equations. Batch adsorption equilibrium studies show a decrease in chromium uptake capacity with increase in pH in the range from 2 to 9, and the uptake capacity at pH 2.5 is found to be 2.93 mmol/g (152 mg/g). The Langmuir adsorption isotherm gives a satisfactory fit of the adsorption data. A kinetics study conducted with different concentrations of chromium(VI) in a batch reactor shows a rapid rate of adsorption. The adsorbent shows a high selectivity toward Cr(VI) and negligible adsorption of Cu(II), Ni(II), and Zn(II). Adsorption tests in a fixed bed column show a sharp breakthrough curve. Stripping of the chromium-loaded column bed is achieved using 4 M HNO3. Twenty cycles of adsorption and desorption process are performed for SOL-IPS adsorbent. The adsorbent maintains 90% of original capacity during 15 cycles, and loss of 25% of capacity until 20 cycles of operation. The imidazole functional adsorbent is demonstrated to be an effective sorbent material for the separation of chromium(VI) from aqueous solutions.