Adsorption Data Analysis| Measuring the Equilibrium Concentration (Ce), Time| Adsorption Experiments

Summary

In this tutorial, Dr. Sak Khan explains how to accurately determine the equilibrium concentration (C value) in absorption experiments. He emphasizes that equilibrium concentration is reached when absorption and desorption rates become equal, typically after a period of time. Through a time-dependent experiment, data is collected, and formulas are used to calculate absorption capacity (QT) and percent removal. The graph of percent removal over time helps identify the equilibrium time, where absorption stabilizes. In this case, after 60 minutes, the equilibrium concentration is found to be 28.4 mg/L. This method ensures precise measurement for further analysis in modeling and kinetics.

Takeaways

• 😀 Equilibrium concentration (C value) is determined by conducting a time experiment, not just by calibration curves based on absorption data.
• 😀 The key to measuring equilibrium concentration is finding the equilibrium time, which occurs when absorption and desorption rates become equal.
• 😀 Equilibrium time is identified when the removal percentage stabilizes, meaning no significant absorption occurs after a certain period.
• 😀 For this specific experiment, equilibrium time was determined to be around 60 minutes, after which absorption slowed down significantly.
• 😀 The experiment was run for 3 hours, with sampling intervals that became longer as the time progressed, starting from 5 minutes and extending to 180 minutes.
• 😀 The removal percentage is calculated using the formula: (C0 - CT) / C0 × 100, where C0 is the initial concentration and CT is the concentration at time T.
• 😀 Absorption increases initially but levels off after 60 minutes, indicating that this is the point of equilibrium.
• 😀 The concentration at the equilibrium time (60 minutes) in this experiment was found to be 28.4 mg/L.
• 😀 The goal of the experiment is to determine when maximum removal is achieved and when further removal becomes negligible.
• 😀 Running the experiment over a longer period allows for better observation of when the absorption and desorption processes reach equilibrium.
• 😀 The equilibrium concentration value is essential for later use in ISO modeling and kinetics analysis.

Q & A

What is the main purpose of the video?

The video explains how to determine the equilibrium concentration (C value) in an absorption experiment, correcting common misconceptions about the process.

What is the difference between the absorption concentration and the equilibrium concentration?

Absorption concentration is determined from the calibration curve using absorption data, while equilibrium concentration is the concentration at the point where absorption and desorption rates become equal, after running the experiment for a sufficient period of time.

How do you determine the equilibrium time in an absorption experiment?

Equilibrium time is determined by observing when the absorption rate stabilizes and no longer increases significantly. In the video, this was seen at around 60 minutes.

What experimental conditions were used in the described absorption experiment?

The experiment used RO6 dye at an initial concentration of 100 ppm, activated carbon as the absorbent, a 30°C temperature, agitation at 150 RPM, and a 3-hour duration with various time intervals for sampling.

Why is it important to run the experiment for an extended period of time?

Running the experiment for a longer period ensures that equilibrium is reached, allowing for accurate measurement of the equilibrium concentration, as absorption continues until it stabilizes.

What formula is used to calculate the adsorption capacity (QT) at any given time?

The adsorption capacity (QT) is calculated using the formula: QT = (C0 - Ct) * Volume / Mass, where C0 is the initial concentration, Ct is the concentration at time t, and Mass and Volume refer to the adsorbent mass and solution volume.

How is the percent removal of the substance calculated?

Percent removal is calculated using the formula: Percent Removal = ((C0 - Ct) / C0) * 100, which expresses the efficiency of absorption at any given time.

At what point did the absorption rate stabilize in the experiment?

The absorption rate stabilized after about 60 minutes, where the removal rate became constant, indicating the equilibrium time was reached.

How does the video suggest determining the equilibrium concentration?

The equilibrium concentration is determined at the point when the absorption rate stabilizes, which in this case occurred at 60 minutes. At this point, the concentration was 28.4 mg/L.

What role does the equilibrium concentration play in further studies?

The equilibrium concentration is crucial for subsequent modeling, such as ISO modeling and kinetics, helping to understand the material's absorption behavior over time.