Modeling and scaling up of the Cr(VI) adsorption process by using mexicalcite natural mineral in a packed bed column

Abstract

The natural mineral known as Mexicalcite is native to the southern region of Mexico, and due to its abundance and accessibility characteristics, as well as its insolubility in water, it is recommended as an adsorbent material. For such reasons, in this work Mexicalcite was used as adsorbent material to remove Cr(VI) in a packed bed column. The effects of the parameters: bed column height (Z), flow rate (Q), and the initial chromium concentration (C0), on the adsorption capacity (q) and removal percentage (%R) were evaluated. The results show minimal changes in adsorption capacity, specifically a 4% difference; with a mean value of 4.98 mg/g. However, maximum removal percentage was obtained for a high height in the bed column, where there is more contact time. However, low removal percentages were obtained for high flow rate, where the contact time is considerably less. The maximum removal was 94.09%, which was obtained with the highest packed bed height (Z= 6cm), initial concentration (C0= 25 mg/L), and lowest flow rate (Q= 2mL/min). The process was modeled using the Thomas, Adams-Bohart and Yoon-Nelson models. With the BDST model, it was possible to scale up the adsorption process and double the original column dimensions. In addition, the column dimensions were obtained theoretically, to operate continuously for 120 h. Finally, the chromium concentration at the outlet was 0.1 mg/L, using a value of 2 for the bed height/column diameter ratio (Z/d).