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.
36. According to the results of Experiment 1, as the pH was increased from trial to trial, the time needed to remove 90% of the Cr6+ from the solution:
Your Answer is
Correct Answer is F
Explanation
Looking at figure 1, it is found that as the pH increases, the more Cr6+ left in the same time, the less Cr6+ is removed. So the higher the pH, the longer it takes to remove 90% of Cr6+