Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Reexamination Certificate
2001-10-31
2003-10-28
Walker, W. L. (Department: 1723)
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
C210S750000, C210S218000, C095S155000, C422S044000, C261S005000
Reexamination Certificate
active
06638428
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of filtration of a solution using a membrane, and particularly to a method of preventing formation of bubbles during filtration operation.
2. Background Art
Suction operation processes are commonly employed techniques in the biological sciences. However, when surfactant- or detergent-containing solution is suctioned through membranes, the solution becomes infused with bubbles. This is quite problematic, since it reduces filtration efficiency, provides poor recovery, requires an additional labor of centrifugation to remove the bubbles, and creates potential contamination to the membrane and surrounding areas. Bubbles can be eliminated when suction power is reduced, however, a portion of solution still exists in the membrane, and it is difficult to recover all solution out of membrane. Although it is possible to recover all the solution by centrifugation without the occurrence of bubbles, this process is not desirable for automation.
High throughput automation is becoming more prevalent and desirable in research, and may often include a filtration step. However, centrifugation is not compatible with the automation process. One way of minimizing user intervention in high throughput automation processes is through utilization of vacuum filtration techniques. The drawback of using the vacuum filtration technique is the appearance of bubbles in the filtered solution.
Therefore, there is a need for an efficient and bubble-free methodology when utilizing a suction operation technique in the rapidly growing high throughput automation platform. Preventing the formation of bubbles during the vacuum filtration process increases sample recovery. In addition, vacuum pressure can be increased and vacuum time can be extended to increase sample recovery during the vacuum filtration process.
SUMMARY OF THE INVENTION
In view of the above, the present invention provides an embodiment wherein a method of filtration comprises: (i) loading a solution-to-be filtrated upstream of a membrane filter, said solution containing components forming bubbles during filtration operation; (ii) covering the solution with a layer of an oil to prevent formation of bubbles from the solution, said oil being non-admixable with the solution and having a lower specific gravity than the solution; (iii) filtrating the solution through the membrane filter wherein the oil stays on the membrane filter; and (iv) recovering a filtrate.
The solution contains detergents or other components, and thus an oil may be slightly admixable depending on the oil. Preferably, the oil is nonpolar and highly hydrophobic. In the above, the oil may be determined to be non-admixable with the solution when, under the filtration condition, the oil passes through the membrane filter when not being wetted with the solution whereas the oil does not pass through the membrane filter when being wetted with the solution. If the oil is highly non-admixable with the solution, the oil does not pass through the membrane even after all collectable filtrate of the solution has passed through the membrane. The membrane is wetted with the solution even after completion of filtration, and the remaining solution on the membrane prevents the oil from passing therethrough. However, if the membrane is highly hydrophilic, the oil may not pass through even if no solution is present. In that case, the oil may be determined to be non-admixable with the solution when, under filtration conditions that the oil passes through a membrane filter when not being wetted with the solution, the oil does not pass through the membrane filter when being wetted with the solution.
The oil may be selected from the group consisting of heavy mineral oil, light mineral oil, almond oil, cinnamon oil, and clove oil.
In an embodiment, the membrane filter is disposable. The solution may be a biological solution such as a cell lysate.
Further, in an embodiment, the filtration is conducted by using a pressure difference between a pressure upstream of the membrane filter and a pressure downstream of the membrane filter, preferably without centrifugation. As long as the downstream pressure is lower than the upstream pressure, filtration can be performed. In an embodiment, the downstream pressure may be a suction pressure. The present invention can also be adapted to centrifuge filtration, although formation of bubbles may not occur in centrifuge filtration.
In another aspect of the present invention, a method is provided for preventing formation of bubbles in filtration operation using a membrane. The method comprises placing a layer of an oil on top of a solution-to-be filtered, wherein said oil has a lower specific gravity than the solution and is non-admixable with the solution, wherein the oil does not pass through the membrane under a designated filtration pressure as lone as the membrane is wetted with the solution.
In still another aspect, a method is provided for preventing formation of bubbles in filtration operation using a membrane, comprising placing a layer of an oil on top of a solution-to-be filtered, wherein the oil has a lower specific gravity than the solution and is non-admixable with the solution to the extent that the oil partially penetrates the membrane under a designated filtration pressure when the membrane is wetted with the solution.
In an embodiment, the oil may have a specific gravity in the range of 0.7-1.1 g/m depending on the specific gravity of the solution-to-be filtered. The specific gravity of the oil may be preferably no more than approximately 1.05 g/ml.
For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention have been described above. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.
Further aspects, features and advantages of this invention will become apparent from the detailed description of the preferred embodiments which follow.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Aspects of the present invention provide a method for the prevention of bubble formation and foaming during filtration operation processes. Specifically, according to some embodiments of the present invention, an oil is over-layered on top of a surfactant- or detergent-containing solution prior to the filtration operation process. The selected oil forms a layer on top of the surfactant- or detergent-containing solution. During the filtration operation process, the oil does not pass through the membrane. As the filtration pressure is pulling the solution down through the membrane, the non-admixability and low specific gravity of the selected oil allow the oil to cover the entire surface of the membrane, sealing the solution and filter surface from air. The prevention of air passage through the filter membrane eliminates the formation of bubbles in the filtered solution. Thus, the recovery of the filtered solution is increased. In addition, the filtration pressure can be increased and the filtration time can be extended to further improve the recovery of the solution. Accordingly, the present invention discloses a methodology for obtaining bubble-free solutions during filtration operation processes.
Thus, in a first aspect, the invention relates to a method of preventing formation of bubbles in a filtration operation comprising placing an oil on top of a solution-to-be filtered, wherein the oil is not admixable with the solution and has a lower specific gravity than the solution so that the oil does not pass through the membrane under a designated filtration pressure.
The solution to be used in the meth
Hitachi Chemical Research Center Inc.
Knobbe Martens & Olson Bear LLP.
Menon Krishnan S
Walker W. L.
LandOfFree
Method of preventing formation of bubbles during filtration... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of preventing formation of bubbles during filtration..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of preventing formation of bubbles during filtration... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3155681