화학공학실험2 화공실2 liquid-liquid extraction 결과레포트

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1. Liquid-Liquid Extraction

Liquid-liquid extraction is an operation for separating a specific substance from the mixture using a selective solvent when a means of distillation-based separation is inadequate due to the similarity in their boiling points of mixture (azeotropic mixtures) or the concern for thermal degradation of the target substance during distillation process. In general, multi-stage extraction is employed using countercurrent process in which the solvent (extracting solvent) is injected into the first stage, whereas the mixture feed (extraction feed) is supplied to the other side.
2. Experimental System

The experimental system consists of a Pyrex-made central extraction tower and internally inserted perforated panels. In addition, a volumetric pump is installed for supplying the feed and the solvent liquids, and a tachometer for measuring the speed of pulsating internal motions of perforated panels is equipped.
3. Refractive Index Measurement

The refractive index of pure benzene and a 2 wt% acetic acid/benzene solution were measured. The refractive index of the 2 wt% acetic acid/benzene solution was measured lower than that of pure benzene.
4. Concentration of Acetic Acid in Lighter Liquid

The concentration of acetic acid in the lighter liquid (benzene) was determined using a calibration curve based on the relationship between acetic acid concentration and refractive index. The concentration of acetic acid in the lighter liquid was found to be 1.31 wt%, 0.46 wt%, and 1.23 wt% under different experimental conditions.
5. Concentration of Heavier Solution

The concentration of the heavier solution (acetic acid in water) was measured using titration with 1M NaOH solution. The average volume of NaOH used was 2.43 mL, 2.87 mL, and 2.97 mL under different experimental conditions, corresponding to acetic acid concentrations of 1.46 wt%, 1.72 wt%, and 1.79 wt%, respectively.
6. Effect of Flow Rate

As the flow rate of the heavier liquid increased, the contact between the heavier and lighter liquids increased, leading to increased extraction of acetic acid from the lighter liquid to the heavier liquid. This resulted in a decrease in the concentration of acetic acid in the lighter liquid and an increase in the concentration in the heavier liquid.
7. Effect of Stroke

As the stroke increased, the contact between the heavier and lighter liquids increased, which was expected to lead to increased extraction of acetic acid from the lighter liquid to the heavier liquid. However, the experimental results showed the opposite trend, likely due to an error in the experiment caused by insufficient heavier liquid.
8. Distribution Coefficient

The distribution coefficient, which represents the ratio of acetic acid concentration in the heavier liquid (water) to the lighter liquid (benzene), was calculated. The smaller the distribution coefficient, the more acetic acid was dissolved in the heavier liquid, indicating better extraction. The distribution coefficient decreased as the flow rate increased and as the stroke decreased, suggesting improved extraction under those conditions.
9. Factors of Error

Potential sources of error include inexperience in operating the equipment, leading to insufficient heavier liquid supply in one of the experiments, and inaccuracies in the titration method used to determine the concentration of the heavier liquid. Additionally, the limited number of experimental conditions and repetitions may have contributed to the unreliable results.
10. Summary

In this experiment, liquid-liquid extraction was performed to extract acetic acid from a mixture. The effects of flow rate and stroke on the extraction efficiency were investigated, and the distribution coefficient was calculated. While the results generally showed that increased flow rate and decreased stroke improved the extraction, an error in one of the experiments led to unreliable results. The authors suggest that more accurate and reliable results could be obtained by improving the experimental setup and increasing the number of experimental conditions and repetitions.

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1. Liquid-Liquid Extraction

Liquid-liquid extraction is a widely used separation technique in various industries, including chemical, pharmaceutical, and environmental applications. It involves the partitioning of a solute between two immiscible liquid phases, typically an aqueous phase and an organic phase. This method is effective for the separation and purification of compounds based on their relative solubilities in the two phases. The key factors that influence the efficiency of liquid-liquid extraction include the choice of solvents, the distribution coefficient of the solute, the contact time between the phases, and the interfacial area between the phases. Proper optimization of these parameters is crucial for achieving high separation efficiency and minimizing the consumption of resources. Additionally, the scale-up and design of liquid-liquid extraction processes require careful consideration of factors such as mass transfer, hydrodynamics, and equipment selection to ensure the process is economically viable and environmentally sustainable.
2. Experimental System

The experimental system for liquid-liquid extraction is a critical component in evaluating the performance and feasibility of the separation process. The design of the experimental system should consider factors such as the nature of the feed and solvent, the desired separation efficiency, and the practical constraints of the process. Typically, the experimental system includes equipment for mixing the feed and solvent, allowing for phase separation, and measuring the concentrations of the solute in the two phases. The choice of mixing equipment, such as stirred tanks or pulsed columns, can significantly impact the mass transfer and interfacial area between the phases. The method of phase separation, whether by gravity or centrifugation, also plays a role in the overall efficiency of the process. The experimental system should be designed to closely mimic the conditions of the intended industrial-scale application, allowing for accurate evaluation of the process performance and the identification of potential scale-up challenges. Careful design and execution of the experimental system are crucial for generating reliable data and informing the development of robust liquid-liquid extraction processes.
3. Refractive Index Measurement

Refractive index measurement is a valuable analytical technique in liquid-liquid extraction processes, as it can provide valuable information about the composition and purity of the extracted phases. The refractive index of a liquid is a physical property that depends on the molecular structure and composition of the liquid, and it can be used to indirectly determine the concentration of a solute in a solution. In the context of liquid-liquid extraction, refractive index measurement can be used to monitor the concentration of the solute in the raffinate and extract phases, which is essential for evaluating the separation efficiency and optimizing the process parameters. The technique is relatively simple, non-destructive, and can be performed in-situ, making it a convenient and cost-effective method for process monitoring and control. However, it is important to note that the relationship between refractive index and solute concentration must be carefully calibrated for the specific system under investigation, as it can be influenced by factors such as temperature, pressure, and the presence of other solutes. Proper calibration and validation of the refractive index measurement method are crucial for ensuring the accuracy and reliability of the data obtained.
4. Concentration of Acetic Acid in Lighter Liquid

The concentration of acetic acid in the lighter liquid phase is a critical parameter in liquid-liquid extraction processes, as it directly affects the separation efficiency and the overall performance of the process. Accurate determination of the acetic acid concentration in the raffinate (lighter) phase is essential for understanding the partitioning behavior of the solute between the two immiscible phases and for optimizing the process conditions. Several analytical techniques, such as titration, spectrophotometry, or chromatography, can be employed to measure the acetic acid concentration in the lighter liquid phase. The choice of the analytical method will depend on factors such as the required accuracy, sensitivity, and the presence of interfering compounds in the sample. It is important to ensure that the analytical method is properly validated and that the sample preparation and handling procedures are standardized to minimize the introduction of errors. Additionally, the effect of factors such as temperature, pH, and the presence of other solutes on the acetic acid concentration should be investigated and accounted for in the analysis. Careful monitoring and control of the acetic acid concentration in the lighter liquid phase can lead to improved separation efficiency, reduced solvent consumption, and overall process optimization.
5. Concentration of Heavier Solution

The concentration of the heavier solution, typically the extract phase, is another critical parameter in liquid-liquid extraction processes. Accurate determination of the solute concentration in the heavier phase is essential for evaluating the overall separation efficiency, calculating the distribution coefficient, and optimizing the process conditions. The analytical techniques used to measure the solute concentration in the heavier phase may differ from those used for the lighter phase, depending on the specific properties of the solute and the composition of the extract. For example, if the solute is a heavy organic compound, techniques such as gravimetric analysis, spectrophotometry, or chromatography may be more suitable than titration. It is important to ensure that the analytical method is properly validated and that the sample preparation and handling procedures are standardized to minimize the introduction of errors. Additionally, the effect of factors such as temperature, pH, and the presence of other solutes on the solute concentration in the heavier phase should be investigated and accounted for in the analysis. Careful monitoring and control of the solute concentration in the heavier phase can lead to improved process efficiency, reduced solvent consumption, and overall process optimization.
6. Effect of Flow Rate

The flow rate of the feed and solvent streams is a critical parameter that can significantly impact the performance of a liquid-liquid extraction process. The flow rate affects the residence time of the phases in the extraction equipment, the degree of mixing and mass transfer between the phases, and the overall separation efficiency. Increasing the flow rate can enhance the mass transfer and improve the extraction yield, but it may also lead to incomplete phase separation, emulsion formation, and increased energy consumption. Conversely, decreasing the flow rate can improve the phase separation and reduce the energy requirements, but it may result in lower extraction efficiency and longer processing times. The optimal flow rate for a given liquid-liquid extraction system depends on various factors, such as the physical properties of the feed and solvent, the desired separation efficiency, the equipment design, and the scale of the process. Careful investigation of the effect of flow rate on the process performance, including the analysis of the solute concentration in both the raffinate and extract phases, is essential for optimizing the liquid-liquid extraction process and ensuring its economic and environmental viability.
7. Effect of Stroke

The stroke, or the amplitude of oscillation, is an important parameter in pulsed column liquid-liquid extraction systems. The stroke affects the degree of mixing and the interfacial area between the two immiscible phases, which in turn influences the mass transfer and separation efficiency. Increasing the stroke can enhance the mixing and increase the interfacial area, leading to improved extraction performance. However, excessive stroke can also cause emulsion formation, phase entrainment, and increased energy consumption. The optimal stroke for a given liquid-liquid extraction system depends on various factors, such as the physical properties of the feed and solvent, the desired separation efficiency, the equipment design, and the scale of the process. Careful investigation of the effect of stroke on the process performance, including the analysis of the solute concentration in both the raffinate and extract phases, is essential for optimizing the liquid-liquid extraction process and ensuring its economic and environmental viability. Additionally, the interaction between the stroke and other process parameters, such as flow rate and pulsation frequency, should be considered to achieve the desired separation efficiency while minimizing the energy and resource requirements.
8. Distribution Coefficient

The distribution coefficient, also known as the partition coefficient, is a fundamental parameter in liquid-liquid extraction processes. It represents the ratio of the solute concentration in the extract phase to the solute concentration in the raffinate phase at equilibrium. The distribution coefficient is a measure of the solute's affinity for the two immiscible phases and is influenced by factors such as the nature of the solute, the solvent, the temperature, and the presence of other solutes or additives. Accurate determination of the distribution coefficient is crucial for predicting the separation efficiency, designing the extraction equipment, and optimizing the process parameters. The distribution coefficient can be determined experimentally by measuring the solute concentrations in the two phases after reaching equilibrium. Alternatively, it can be estimated using thermodynamic models or empirical correlations, which require knowledge of the physicochemical properties of the system. Understanding and controlling the distribution coefficient is essential for achieving the desired separation performance, minimizing solvent consumption, and ensuring the economic and environmental viability of the liquid-liquid extraction process.
9. Factors of Error

In liquid-liquid extraction processes, various factors can introduce errors and uncertainties in the experimental measurements and the overall process performance. These factors of error must be identified, quantified, and minimized to ensure the reliability and reproducibility of the results. Some common sources of error include: 1. Sampling and sample preparation: Errors can arise from the way the samples are collected, handled, and prepared for analysis, such as incomplete phase separation, loss of volatile components, or contamination. 2. Analytical techniques: The accuracy and precision of the analytical methods used to determine the solute concentrations in the raffinate and extract phases can significantly impact the results. 3. Equipment and instrumentation: Errors can be introduced by the calibration, operation, and maintenance of the extraction equipment, such as flow meters, temperature sensors, and mixing devices. 4. Process conditions: Variations in parameters like temperature, pressure, pH, and residence time can affect the mass transfer, phase equilibrium, and separation efficiency. 5. Human factors: Errors can be introduced by the operator's technique, judgment, and adherence to standard operating procedures. Identifying and quantifying these sources of error through statistical analysis, sensitivity studies, and uncertainty propagation is crucial for understanding the reliability of the experimental data and the process performance. Implementing appropriate quality control measures, such as replicate measurements, calibration procedures, and process monitoring, can help minimize the factors of error and improve the overall quality and reproducibility of the liquid-liquid extraction process.
10. Summary

In summary, the liquid-liquid extraction process is a widely used separation technique that relies on the partitioning of a solute between two immiscible liquid phases. The key factors that influence the efficiency of this process include the choice of solvents, the distribution coefficient of the solute, the contact time between the phases, and the interfacial area between the phases. The design and optimization of the experimental system are crucial for generating reliable data and informing the development of robust liquid-liquid extraction processes. Refractive index measurement is a valuable analytical technique that can provide valuable information about the composition and purity of the extracted phases. Accurate determination of the solute concentrations in both the raffinate and extract phases is essential for evaluating the separation efficiency and optimizing the process parameters. The flow rate and stroke (in pulsed column systems) are important parameters that can significantly impact the performance of the liquid-liquid extraction process. Careful investigation of their effects on the process performance is necessary for achieving the desired separation efficiency while minimizing the energy and resource requirements. The distribution coefficient is a fundamental parameter that represents the solute's affinity for the two immiscible phases. Understanding and controlling the distribution coefficient is crucial for predicting the separation efficiency, designing the extraction equipment, and optimizing the process parameters. Finally, identifying and minimizing the factors of error, such as those related to sampling, analysis, equipment, process conditions, and human factors, is essential for ensuring the reliability and reproducibility of the experimental data and the overall process performance.