Passage VI

Biosorption is a process that uses certain biological materials (biomass) to remove metal ions from a solution. Three experiments were done to study the removal of the chromium ion Cr⁶⁺ from aqueous solutions using a biomass composed of crushed shells of the fruit Litchi chinensis. In each trial in each experiment, the following steps were performed:

1. In a flask, 1.0 g of fresh biomass was added to 100 mL of an aqueous solution having a particular pH and Cr⁶⁺ concentration.

2. The flask was capped, and the contents were shaken for a particular time at a particular temperature.

3. Periodically, shaking was stopped so that a 0.01 mL sample could be removed from the flask. This sample was analyzed to determine the percentage of Cr⁶⁺ remaining in the solution.

Experiment 1

In each of Trials 1-4, an aqueous solution with an initial concentration of 100 mg/L was tested at a temperature of 30°C. The pH was varied from trial to trial. The results are shown in Figure 1.

Experiment 2

In each of Trials 5-7, an aqueous solution with an initial Cr⁶⁺ concentration of 100 mg/L was tested at a pH of 1.0. The temperature was varied from trial to trial. The results are shown in Figure 2.

Experiment 3

In each of Trials 8-11, an aqueous solution at a pH of 1.0 was tested at a temperature of 30°C. The initial Cr⁶⁺ concentration was varied from trial to trial. The results are shown in Figure 3.

Figures adapted from Ismael Acosta-Rodriguez et al., “Removal of Hexavalent Chromium from Solutions and Contaminated Sites by Different Natural Biomasses." ©2013 by Ismael Acosta-Flodrfguez et al.