Highly efficient removal of chromium (VI) through adsorption and reduction: A column dynamic study using magnetized natural zeolite-polypyrrole composite

A composite of magnetized natural zeolite and polypyrrole (MZ-PPY) was synthesized and used to explore Cr(VI) removal from aqueous solution and environmental water. A column dynamic set up was employed to analyse adsorption breakthrough performance under different process conditions. Material characterization was done to assess morphology and functional groups and to elucidate Cr(VI) removal mechanism. Results indicate that Cr(VI) removal is a function of bed mass, flowrate and initial Cr(VI) concentration. Sharp breakthrough curves were obtained which are fingerprints of reaction kinetics controlled adsorption process. Consequently, three simple kinetic models; Yoon–Nelson, Thomas and Bohart–Adams were applied to the experimental data to predict the breakthrough curves and to determine the characteristic parameters of the column that are useful for process design. The Yoon–Nelson and Thomas models were found to appropriately describe the breakthrough curves. From material characterization, Cr(VI) removal proceeded mainly by adsorption and reduction. Meanwhile using adsorbent exhaustion rate (AER) as performance indicator, a low value of 0.25 was obtained for environmental water from a chrome mine suggesting that MZ-PPY is a highly efficient adsorption media.