As(III) removal from aqueous medium in fixed bed using iron oxide-coated cement (IOCC): Experimental and modeling studies

Continuous fixed bed studies were undertaken to evaluate the efficiency of iron oxide-coated cement (IOCC) as an adsorbent for the removal of As(III) from aqueous solution under the effect of various process parameters like bed depth (10–20 cm), flow rate (4.3–12 ml min−1) and initial As(III) concentrations (0.5–2.7 mg l−1). The results showed that the total As(III) uptake decreased with increasing flow rate and increased with increasing initial As(III) concentration. Also, the total As(III) removal percentage increased with the increase in bed depth. The dynamics of the adsorption process was modeled by bed depth service time (BDST), mass transfer, Thomas and Yoon–Nelson models. The BDST model fitted well with the experimental data in the initial region of the breakthrough curve but showed slight deviations above break points. Though the experimental data points and the data points predicted using the mass transfer model followed a similar trend, they slightly deviated from each other. The Thomas and Yoon–Nelson model predictions were in very good agreement with the experimental results at all the process parameters studied indicating that they were very suitable for IOCC column design. The apparent mechanism of As(III) removal in the IOCC column were ion exchange and physisorption on the adsorbent surface.