Optimal design of a simulated-moving-bed chromatographic process for high-purity separation of acetoin from 2,3-butanediol in a continuous mode.

For the high-purity production of acetoin or 2,3-butanediol (BD) from related fermentation processes, it is essential to accomplish a detailed separation between acetoin and BD in an economical mode. To address this issue, we aimed to develop a highly-efficient simulated-moving-bed (SMB) process for the continuous-mode separation of acetoin from BD with high purity and small loss. As a first step for this task, the adsorption and mass-transfer parameters of acetoin and BD on a proven adsorbent were estimated while assuming that BD isomers (meso-BD and DL-BD) would be identical in adsorption and mass-transfer behaviors. The resultant parameters from such estimation were applied to the optimal design of the acetoin-BD separation SMB. The designed SMB was then experimentally investigated, which revealed that some sign of BD isomerism occurred in the SMB column-profile data and thus had an adverse effect on the SMB separation performance. To resolve this problem, the individual parameters of BD isomers were determined on the basis of the SMB column-profile data and an inverse-method principle. The resulting parameters of BD isomers were used in the re-design of the target SMB, which was then experimentally checked for its separation performance. It was confirmed that such SMB re-designed in consideration of BD isomerism was quite effective in the continuous-mode separation of acetoin from BD with high purity (> 99.2%) and small loss (< 1.52%).

Relationship between desorbent usage and the recovery of a target product in three-zone simulated moving bed processes designed under the conditions of positive and negative flow-rate-ratios of liquid to solid phases.

For a simulated moving bed (SMB) chromatographic process, it has been common knowledge that as desorbent usage increases, the level of separation capability (i.e., the purity and recovery of a target product) continues to improve and then eventually reaches almost a constant level. To check whether there are any exceptional cases concerning such a generally accepted relationship, the effect of desorbent usage on the recovery of a target product under the condition of high purity was investigated using a three-zone SMB process for separation of xylobiose (X2) from a ß-xylosidase reaction output. It was found that the considered SMB represented some unusual relationship between desorbent usage and X2 recovery, which also took quite a different pattern according to the searching region for optimal SMB operation parameters. If the optimal operation parameters are determined in the region of positive flow-rate-ratios ("m+ approach"), the use of a larger amount of desorbent than required to make X2 recovery reach a constant level can rather lead to a little reduction in X2 recovery. If the optimal operation parameters are selected in the region of negative flow-rate-ratios ("m- approach"), there exists an optimal desorbent usage, beyond which a further increase in desorbent usage can bring about a significant reduction in X2 recovery. Comparison of the two design approaches reveals that the m- approach can lead to higher X2 recovery and much lower desorbent usage than the m+ approach. Furthermore, such merits of the m- approach over the m+ approach became greater with increasing the SMB throughput.

Continuous-mode separation of fucose and 2,3-butanediol using a three-zone simulated moving bed process and its performance improvement by using partial extract-collection, partial extract-recycle, and partial desorbent-port closing.

If a multi-component monosugar mixture including fucose was used as the substrates for the Klebsiella oxytoca fermentation, it could offer the following two benefits simultaneously; (i) the removal of all monosugars other than fucose, and (ii) the acquisition of 2,3-butanediol (BD). To utilize such two benefits in favor of the economical efficiency of the fucose production process, it is essential to accomplish a high-purity separation between fucose and BD on the basis of a highly-economical mode. To address this issue, we aimed to develop a simulated moving bed (SMB) process for continuous-mode separation of fucose and BD with high purities. It was first found that an Amberchrom-CG71C resin could become a suitable adsorbent for the separation of interest. The intrinsic parameters of fucose and BD on such proven adsorbent were determined, and then applied to the optimal design of the fucose-BD separation SMB. The capability of the designed SMB in ensuring high purities and high yields was experimentally verified. Finally, we devised two potential strategies to make a further improvement in product concentrations and/or desorbent usage while keeping the purities and yields of fucose and BD almost unchanged. The first strategy was based on partial extract-collection and partial extract-discard, which was found to result in 33% higher BD product concentration. The second strategy was based on partial extract-collection, partial extract-recycle, and partial desorbent-port closing, which could lead to 25% lower desorbent usage, 33% higher BD product concentration, and 7% higher fucose product concentration.

Optimization of production rate, productivity, and product concentration for a simulated moving bed process aimed atfucose separation using standing-wave-design and genetic algorithm.

The effectiveness of a simulated moving bed (SMB) technology in the continuous separation of fucose from a multi-component monosugar mixture, which stemmed from defatted microalgae, has recently been identified. To guarantee high economical efficiency of such fucose-production method, the comprehensive optimization of the relevant fucose-separation SMB process needs to be accomplished such that its production rate (Prate) and/or productivity (Prod) can be maximized while meeting the requirements on fucose product concentration (Cprod,F) and pressure drop (ΔPSMB). To resolve this issue, the SMB optimization program based on standing-wave-design method and genetic algorithm was prepared and then applied to the fucose-separation SMB optimization. It was found that the Prate, under a given particle size, could reach its maximum when the column length was selected to create a balance between the effects of the two limiting factors related to Cprod,F and ΔPSMB. It was also found that the Prate was governed by fucose yield, if the SMB would be in need of a relatively high Cprod,F; otherwise, the Prate was governed by feed flow rate. If the particle size of the SMB adsorbent was fixed at one of the commercially available ones, the SMB conditions leading to the highest Prate and the highest Prod coincided with each other. By contrast, if the particle size was included as one of optimization variables, the Prate and Prod represented a trade-off relationship. Finally, it was confirmed from the simultaneous optimization for Prate and Prod that the increase of particle size improved Prate at the cost of Prod, thereby causing the maximum Prod to be always attained at a smaller particle size than the maximum Prate regardless of the target Cprod,F level.

Standing wave design and optimization of a simulated moving bed chromatography for separation of xylobiose and xylose under the constraints on product concentration and pressure drop.

The feasibility of a simulated moving bed (SMB) technology for the continuous separation of high-purity xylobiose (X2) from the output of a ß-xylosidase X1→X2 reaction has recently been confirmed. To ensure high economical efficiency of the X2 production method based on the use of xylose (X1) as a starting material, it is essential to accomplish the comprehensive optimization of the X2-separation SMB process in such a way that its X2 productivity can be maximized while maintaining the X2 product concentration from the SMB as high as possible in consideration of a subsequent lyophilization step. To address this issue, a suitable SMB optimization tool for the aforementioned task was prepared based on standing wave design theory. The prepared tool was then used to optimize the SMB operation parameters, column configuration, total column number, adsorbent particle size, and X2 yield while meeting the constraints on X2 purity, X2 product concentration, and pressure drop. The results showed that the use of a larger particle size caused the productivity to be limited by the constraint on X2 product concentration, and a maximum productivity was attained by choosing the particle size such that the effect of the X2-concentration limiting factor could be balanced with that of pressure-drop limiting factor. If the target level of X2 product concentration was elevated, higher productivity could be achieved by decreasing particle size, raising the level of X2 yield, and increasing the column number in the zones containing the front and rear of X2 solute band.

Design of simulated moving bed for separation of fumaric acid with a little fronting phenomenon.

The production of fumaric acid through a biotechnological pathway has grown in importance because of its potential value in related industries. This has sparked an interest in developing an economically-efficient process for separation of fumaric acid (product of interest) from acetic acid (by-product). This study aimed to develop a simulated moving bed (SMB) chromatographic process for such separation in a systematic way. As a first step for this work, commercially available adsorbents were screened for their applicability to the considered separation, which revealed that an Amberchrom-CG71C resin had a sufficient potential to become an adsorbent of the targeted SMB. Using this adsorbent, the intrinsic parameters of fumaric and acetic acids were determined and then applied to optimizing the SMB process under consideration. The optimized SMB process was tested experimentally, from which the yield of fumaric-acid product was found to become lower than expected in the design. An investigation about the reason for such problem revealed that it was attributed to a fronting phenomenon occurring in the solute band of fumaric acid. To resolve this issue, the extent of the fronting was evaluated quantitatively using an experimental axial dispersion coefficient for fumaric acid, which was then considered in the design of the SMB of interest. The SMB experimental results showed that the SMB design based on the consideration of the fumaric-acid fronting could guarantee the attainment of both high purity (>99%) and high yield (>99%) for fumaric-acid product under the desorbent consumption of 2.6 and the throughput of 0.36L/L/h.

Improvement of the performances of a tandem simulated moving bed chromatography by controlling the yield level of a key product of the first simulated moving bed unit.

One of the trustworthy processes for ternary separation is a tandem simulated moving bed (SMB) process, which consists of two subordinate four-zone SMB units (Ring I and Ring II). To take full advantage of a tandem SMB as a means of recovering all three products with high purities and high economical efficiency, it is important to understand how the separation condition in Ring II is affected by that in Ring I, and further to reflect such point in the stage of designing a tandem SMB. In regard to such issue, it was clarified in this study that the Ring I factors affecting the Ring II condition could be represented by the yield level of a key product of Ring I (YkeyRingI). As the YkeyRingI level became higher, the amount of the Ring I key-product that was reloaded into Ring II was reduced, which affected favorably the Ring II separation condition. On the other hand, the higher YkeyRingI level caused a larger dilution for the stream from Ring I to Ring II, which affected adversely the Ring II separation condition. As a result, a minimum in the desorbent usage of a tandem SMB occurred at the YkeyRingI level where the two aforementioned factors could be balanced with each other. If such an optimal YkeyRingI level was adopted, the desorbent usage could be reduced by up to 25%. It was also found that as the throughput of a tandem SMB became higher, the factor related to the migration of the Ring I key-product into Ring II was more influential in the performances of a tandem SMB than the factor related to the dilution of the stream from Ring I to Ring II.

Highly efficient recovery of xylobiose from xylooligosaccharides using a simulated moving bed method.

Xylobiose (X2), which is currently available from xylooligosaccharides (XOS), has been reported to have outstanding prebiotic function and to be highly suitable for application in food industries. This has sparked an interest in the economical production of X2 of high purity (> 99%) in food and prebiotic industries. To address such issue, we developed a highly-efficient chromatographic method for the recovery of X2 from XOS with high purity and high recovery. As a first step for this work, an eligible adsorbent for a large-scale separation between X2 and other XOS components was selected. For the selected adsorbent, a single-column experiment was carried out to determine the intrinsic parameters of all the XOS components, which were then used in the optimal design of the continuous X2-recovery process based on a simulated moving bed (SMB) chromatographic method. Finally, the performance of the designed X2-recovery SMB process was verified by the relevant SMB experiments, which confirmed that the developed process in this study could recover X2 from XOS with the purity of 99.5% and the recovery of 92.3% on a continuous-separation mode. The results of this study will be useful in enabling the economical production of high-purity X2 on a large scale.

Effect of adsorbent particle size on the relative merits of a non-triangular and a triangular separation region in the optimal design of a three-zone simulated moving bed chromatography for binary separation with linear isotherms.

The design approaches for a three-zone simulated moving bed (SMB) chromatography with linear isotherms can be classified into two categories, depending on whether the SMB design is based on a classical region (i.e., triangular region of the triangle theory) in the first quadrant (m2, m3) plane or on a non-triangular separation region in the third quadrant (m2, m3) plane. The SMBs based on the classical and the non-triangular design approaches, which are named here as (m(+))_SMB and (m(-))_SMB respectively, are compared in this study using the Pareto solutions from the simultaneous optimization of throughput and desorbent usage under the constraints on product purities and pressure drop. The results showed that the (m(-))_SMB approach led to significantly lower desorbent usage than the (m(+))_SMB approach, which was due to the fact that the flow-rate-ratios from the (m(-))_SMB approach are extremely lower than those from the (m(+))_SMB approach. This factor also enables the (m(-))_SMB to have a significantly lower pressure drop, thereby making its throughput less restricted by a pressure-drop constraint. Due to such advantage of the (m(-))_SMB, it can make a further substantial improvement in throughput by modulating its adsorbent particle size properly. This issue was investigated using a model separation system containing succinic acid and acetic acid. It was confirmed that if the adsorbent particle size corresponding to the boundary between a mass-transfer limiting region and a pressure-drop limiting region is adopted, the (m(-))_SMB can lead to 82% higher throughput and 73% lower desorbent usage than the (m(+))_SMB.

Continuous recovery of valine in a model mixture of amino acids and salt from Corynebacterium bacteria fermentation using a simulated moving bed chromatography.

The economical efficiency of valine production in related industries is largely affected by the performance of a valine separation process, in which valine is to be separated from leucine, alanine, and ammonium sulfate. Such separation is currently handled by a batch-mode hybrid process based on ion-exchange and crystallization schemes. To make a substantial improvement in the economical efficiency of an industrial valine production, such a batch-mode process based on two different separation schemes needs to be converted into a continuous-mode separation process based on a single separation scheme. To address this issue, a simulated moving bed (SMB) technology was applied in this study to the development of a continuous-mode valine-separation chromatographic process with uniformity in adsorbent and liquid phases. It was first found that a Chromalite-PCG600C resin could be eligible for the adsorbent of such process, particularly in an industrial scale. The intrinsic parameters of each component on the Chromalite-PCG600C adsorbent were determined and then utilized in selecting a proper set of configurations for SMB units, columns, and ports, under which the SMB operating parameters were optimized with a genetic algorithm. Finally, the optimized SMB based on the selected configurations was tested experimentally, which confirmed its effectiveness in continuous separation of valine from leucine, alanine, ammonium sulfate with high purity, high yield, high throughput, and high valine product concentration. It is thus expected that the developed SMB process in this study will be able to serve as one of the trustworthy ways of improving the economical efficiency of an industrial valine production process.

Simulated moving bed separation of agarose-hydrolyzate components for biofuel production from marine biomass.

The economically-efficient separation of galactose, levulinic acid (LA), and 5-hydroxymethylfurfural (5-HMF) in acid hydrolyzate of agarose has been a key issue in the area of biofuel production from marine biomass. To address this issue, an optimal simulated moving bed (SMB) process for continuous separation of the three agarose-hydrolyzate components with high purities, high yields, and high throughput was developed in this study. As a first step for this task, the adsorption isotherm and mass-transfer parameters of each component on the qualified adsorbent were determined through a series of multiple frontal experiments. The determined parameters were then used in optimizing the SMB process for the considered separation. Finally, the optimized SMB process was tested experimentally using a self-assembled SMB unit with four zones. The SMB experimental results and the relevant computer simulations verified that the developed process in this study was quite successful in the economically-efficient separation of galactose, LA, and 5-HMF in a continuous mode with high purities and high yields. It is thus expected that the developed SMB process in this study will be able to serve as one of the trustworthy ways of improving the economic feasibility of biofuel production from marine biomass.

Optimal design and experimental validation of a simulated moving bed chromatography for continuous recovery of formic acid in a model mixture of three organic acids from Actinobacillus bacteria fermentation.

The economically-efficient separation of formic acid from acetic acid and succinic acid has been a key issue in the production of formic acid with the Actinobacillus bacteria fermentation. To address this issue, an optimal three-zone simulated moving bed (SMB) chromatography for continuous separation of formic acid from acetic acid and succinic acid was developed in this study. As a first step for this task, the adsorption isotherm and mass-transfer parameters of each organic acid on the qualified adsorbent (Amberchrom-CG300C) were determined through a series of multiple frontal experiments. The determined parameters were then used in optimizing the SMB process for the considered separation. During such optimization, the additional investigation for selecting a proper SMB port configuration, which could be more advantageous for attaining better process performances, was carried out between two possible configurations. It was found that if the properly selected port configuration was adopted in the SMB of interest, the throughout and the formic-acid product concentration could be increased by 82% and 181% respectively. Finally, the optimized SMB process based on the properly selected port configuration was tested experimentally using a self-assembled SMB unit with three zones. The SMB experimental results and the relevant computer simulation verified that the developed process in this study was successful in continuous recovery of formic acid from a ternary organic-acid mixture of interest with high throughput, high purity, high yield, and high product concentration.

Enhanced performance of a three-zone simulated moving bed chromatography for separation of succinic acid and lactic acid by simultaneous use of port-location rearrangement and partial-feeding.

The performance of a three-zone simulated moving bed (SMB) chromatographic process for separation of succinic acid and lactic acid has been improved to a certain extent in previous researches by applying either a partial-feeding (PF) or a port-location rearrangement (PR) to its operation. To make a further improvement, the strategy of applying both PF and PR simultaneously to the three-zone SMB operation was proposed in this study. The results from both equilibrium-theory analysis and detailed simulation proved that the proposed strategy, which was called PF-PR in this article, had the benefit of a synergy between the individual merits of PF and PR in the three-zone SMB performance. As a consequence, the PF-PR mode could surpass the PF and the PR modes by a wide margin and the classical mode by a dramatic margin in the aspects of separation performance and throughput.

Comparison of the relative merits of port-location rearrangement and partial-feeding as the strategy for improving the performances of a three-zone simulated moving chromatography for separation of succinic acid and lactic acid.

The three-zone simulated moving bed (SMB) chromatographic process for separation of succinic acid and lactic acid, which has been developed previously, was based on a classical port-location arrangement (desorbent→extract→feed→raffinate) and a classical feeding mode (full-feeding). To improve the performance of the three-zone SMB process, it is worth utilizing the strategy of either a port-location rearrangement (desorbent→feed→raffinate→extract) or a partial-feeding. To investigate which of the two strategies is more effective, the three-zone SMBs based on the port-location rearrangement (PR) and the partial-feeding (PF) were optimized each under equal conditions and then the two strategies were compared in terms of product purities or throughput. The result showed that the PR strategy led to higher purities or higher throughput than the PF strategy in regard to the previously reported three-zone SMB system. To check whether such trend is still valid in other separation systems, the above optimization works were repeated while varying only the selectivity between two feed components. It was confirmed that the PR strategy is definitely superior to the PF strategy. However, such superiority of the PR over the PF strategy is lessened as the selectivity becomes lower. If the selectivity is significantly low, the PR strategy is rather outperformed by the PF strategy.

Experimental evaluation of the effect of a modified port-location mode on the performance of a three-zone simulated moving-bed process for the separation of valine and isoleucine.

The removal of isoleucine from valine has been a key issue in the stage of valine crystallization, which is the final step in the valine production process in industry. To address this issue, a three-zone simulated moving-bed (SMB) process for the separation of valine and isoleucine has been developed previously. However, the previous process, which was based on a classical port-location mode, had some limitations in throughput and valine product concentration. In this study, a three-zone SMB process based on a modified port-location mode was applied to the separation of valine and isoleucine for the purpose of making a marked improvement in throughput and valine product concentration. Computer simulations and a lab-scale process experiment showed that the modified three-zone SMB for valine separation led to >65% higher throughput and >160% higher valine concentration compared to the previous three-zone SMB for the same separation.

Improving performance of a tandem simulated moving bed process for sugar separation by making a difference in the adsorbents and the column lengths of the two subordinate simulated moving bed units.

A tandem simulated moving bed (SMB) process for removal of sulfuric acid and acetic acid from sugars has been developed previously. This process consisted of two four-zone SMB units (Ring I and Ring II), in which the same adsorbent (Dowex99 resin) and the same column length were used. To improve the performance of such a tandem SMB process for sugar separation, it is worth adopting the strategy of making a difference between the column lengths of Ring I and Ring II. The results showed that such strategy could allow the adsorbent beds of both Ring I and Ring II to be fully utilized at the same time, which was impracticable in the previous tandem SMB mode. As a result, the tandem SMB based on such strategy could achieve higher productivity than the previous tandem SMB mode. In addition, the use of different adsorbents (Amberchrom-CG161C in Ring I and Dowex99 in Ring II) was proposed as the second strategy, which was confirmed to be highly effective in improving the productivity of the tandem SMB for sugar separation. Finally, a third strategy was proposed by combing the first and the second strategies. It was found that compared to the previous tandem SMB mode, the third strategy led to more than eleven times the productivity under the constraint of pressure drop ≤100 psi. This was mostly because the third strategy had a remarkable advantage over the previous tandem SMB mode in the aspects of bed utilization and selectivities, which stemmed from the use of different column lengths and the use of different adsorbents respectively.

Development of a non-triangular separation region for improving the performance of a three-zone simulated moving bed chromatography for binary separation with linear isotherms.

For a three-zone simulated moving bed (SMB) chromatography with linear isotherms, the feasible set of operating parameters for complete separation is known to exist within a triangular region of the triangle theory that is formed in the operating parameter plane spanned by the flow-rate-ratios in the separation zones (II and III), which are commonly denoted as m(2) and m(3). Such an operating region for complete separation region, however, has been established only in the first quadrant (m(2), m(3)) plane, where m(2)>0 and m(3)>0, until now. In this study, a new complete-separation region was developed in the third quadrant (m(2), m(3)) plane, where m(2)<0 and m(3)<0, regarding a three-zone SMB process for the first time. The results showed that the new separation region created in the third quadrant (m(2), m(3)) plane took a non-triangular shape. The operating parameters within such a non-triangular separation region were capable of guaranteeing complete separation for an ideal system with no mass-transfer effects. For a non-ideal system with considerable mass-transfer effects, the operating parameters that were selected with a sufficient margin from the boundaries of the non-triangular separation region led to high purities. One of the noteworthy features in the pattern of solute migration for such case was that both low-affinity and high-affinity solutes reached their corresponding product ports after taking a turn around the SMB bed once. Finally, it was confirmed from the results of SMB optimization based on genetic algorithm and detailed model that the operating parameters in the third quadrant (m(2), m(3)) plane, if chosen properly, could ensure higher purities or higher throughput than the optimal operating parameters in the first quadrant (m(2), m(3)) plane.

Strategy of rearranging the port locations in a three-zone simulated moving bed chromatography for binary separation with linear isotherms.

A three-zone simulated moving bed (SMB) chromatographic process for binary separation, which has been developed previously, was reported to have four ports that are located in the order of desorbent, extract, feed, and raffinate. To make a substantial improvement in the performance of such a three-zone SMB process, the strategy of rearranging the port locations was proposed in this study within a linear isotherm region. The core of the proposed strategy is to transfer the location of the extract port from its classical position (i.e., the position between zones I and II) to the zone III outlet. Simultaneously, the feed and raffinate ports are transferred backwards by one zone. Thus, the order of the proposed port locations follows the order of desorbent, feed, raffinate, and extract. The results from both equilibrium-theory analysis and detailed simulation proved that the proposed strategy was highly effective in improving the product purities or throughput of a three-zone SMB process. Furthermore, it was found that such advantage of the proposed strategy became greater as the difference between the adsorption affinities of the feed components was larger.

Improving performance of a five-zone simulated moving bed chromatography for ternary separation by simultaneous use of partial-feeding and partial-closing of the product port in charge of collecting the intermediate-affinity solute molecules.

The performance of a five-zone simulated moving bed (SMB) chromatographic process for ternary separation has been improved to a certain extent in previous researches by applying either a partial-feeding (PF) or a partial-closing of the extract-2 port (PCE(2)) to its operation. To make a further improvement, the strategy of applying both PF and PCE(2) simultaneously to the five-zone SMB operation was proposed in this study. The results from both equilibrium-theory analysis and detailed simulation proved that the proposed strategy, which was called PF-PCE(2) in this article, had the benefit of a synergy between the individual merits of PF and PCE(2) in the five-zone SMB performance. As a consequence, the PF-PCE(2) mode could surpass the PF and the PCE(2) modes by a wide margin and the standard mode by a much wider margin in the aspects of ternary-separation performance and throughput. For the separation system considered, the PF-PCE(2) mode was found to achieve more than 100% improvement, compared to the standard mode. Furthermore, such advantage of the PF-PCE(2) over all the other modes was greater as the selectivity between the intermediate-affinity and the highest-affinity components was reduced.

Development of a four-zone carousel process packed with metal ion-imprinted polymer for continuous separation of copper ions from manganese ions, cobalt ions, and the constituent metal ions of the buffer solution used as eluent.

A three-zone carousel process, in which Cu(II)-imprinted polymer (Cu-MIP) and a buffer solution were employed as adsorbent and eluent respectively, has been developed previously for continuous separation of Cu²âº (product) from Mn²âº and Co²âº (impurities). Although this process was reported to be successful in the aforementioned separation task, the way of using a buffer solution as eluent made it inevitable that the product stream included the buffer-related metal ions (i.e., the constituent metal ions of the buffer solution) as well as copper ions. For a more perfect recovery of copper ions, it would be necessary to improve the previous carousel process such that it can remove the buffer-related metal ions from copper ions while maintaining the previous function of separating copper ions from the other 2 impure heavy-metal ions. This improvement was made in this study by proposing a four-zone carousel process based on the following strategy: (1) the addition of one more zone for performing the two-step re-equilibration tasks and (2) the use of water as the eluent of the washing step in the separation zone. The operating conditions of such a proposed process were determined on the basis of the data from a series of single-column experiments. Under the determined operating conditions, 3 runs of carousel experiments were carried out. The results of these experiments revealed that the feed-loading time was a key parameter affecting the performance of the proposed process. Consequently, the continuous separation of copper ions from both the impure heavy-metal ions and the buffer-related metal ions could be achieved with a purity of 91.9% and a yield of 92.8% by using the proposed carousel process based on a properly chosen feed-loading time.