What exactly do we mean by Ultrafiltration, and for what processes can it be used? Ultrafiltration is a process by which one uses a pressure-driven process utilizing a specific-sized membrane to separate macromolecular weights of a solution, allowing the transfer of the low molecular weight (permeate). Ultrafiltration is exclusively defined by the pore size range (0.1 – 0.001 microns) (Dhawan). Ultrafiltration is used in a wide array of applications, such as food and beverage, chemical, pharmaceutical, medical, drinking water, wastewater and etc. This research review will focus on industrial applications, and transport processes that make ultrafiltration unique, as well as the industry standard for separation.
The rapid development of ultrafiltration for industrial processes is possible by the advent of anisotropic, high-flux membranes capable of distinguishing among molecular sizes of 10 A to 10 µ size ranges (Porter, 1972). The high molecular solute which flows through, but does not pass through the membrane is released as retentate (concentrate). The solution that passes through the membrane is known as permeate, which is shown Figure 1. This figure demonstrates the basic structure of a hollow membrane where the feed of the material you want to separate enters, and where the permeate (ultrafiltrate), and retentate exits. In different industrial processes one may want to retain the permeate, retentate, or combination of both.
Mass Balance, Momentum Balance and Flux
Figure 1: Flows and fluxes in a hollow fiber for ultrafiltration (Yeh, 2009)
Let us take a closer look at what drives ultrafiltration from a mathematical point of view. In Figure 1, the feed solution is being driven by a volumetric flow rate (qi/Ni), pressure (∆Pi), and concentration (Ci). This feed solution produces a mass balance which results in the flux (J) vs fiber (dz):
(Yeh, 2009)
The momentum balance must be accounted for also:
(Yeh, 2009)
It can be presumed that the volumetric flow rate will be reduced similarly to the Hagen–Poiseuille equation, due to the laminar flow within the tube in Yeh, H. experiment in 2009, he takes into account convection as well as mass, and momentum balance:
(Yeh, 2009)
Equation 3 assumes that the volumetric flow rate is relatively large compared to that of the permeation rate. This occurs mainly in an exponential model along the membrane tube. This model simply states that when working with a pressure-drive ultrafiltration process, as pressure is increased, a ceiling (limiting) flux will occur regardless of increasing the pressure. We know that the relationship between membrane pressure (∆ρ) and the permeate flux leads us to the following conclusion (Yeh, 2009).
The concept of gel filtration is very practical. The column contains porous beads through which the solvent and proteins can go through. Large proteins cannot access the internal volume (the solution within the beads) so it goes through the external volume (the solution that is outside of the
The water concentration is now even on the inside and out. This process is called osmosis. Part B: Aim: To investigate the action of a differentially permeable membrane. Method: See attached.
The side of the membrane that has the higher concentration is said to have the concentration gradient. It drives diffusion because substances always move down their concentration gradient. The pressure gradient also plays a role in diffusion. Where this is a pressure gradient there is motion of molecules. The pressure gradient is a difference in pressure between two different points.
The experiment is aimed at giving a better understanding of the osmosis process and the different conditions in which osmosis occurs. INTRODUCTION When a cell membrane is said to be selectively permeable, it means that the cell membrane controls what substances pass in and out through the membrane. This characteristic of cell membranes plays a great role in passive transport. Passive transport is the movement of substances across the cell membrane without any input of energy by the cell.
Osmosis is the facilitated diffusion of water across the cell membrane of a cell. The inside layer of the cell membrane is hydrophilic, meaning water cannot easily pass through the membrane. The cell membrane has to have aquaporins, which are water channel proteins, that move the water across the membrane. If there is a water and salt solution outside the cell, the salt can enter the cell by diffusion, but the cell membrane is not permeable to the water. Because there is more solute solution inside the cell, there is less water. The aquaporins move the water across the membrane until equilibrium is reached.
Stephenson, R., & Blackburn, J. J. (1998). The Industrial Wastewater Systems Handbook. New York: Lewis Publishers.
Comment on class result with respect to differences in filter types, differences in filter assemblies, and overall on the confidence you would have in using this type of sterilisation process in preparation of pharmaceutical products. List the factors that may cause contamination during filtration. (20 marks)
Once the mixture had been completely dissolved, the solution was transferred to a separatory funnel. The solution was then extracted twice using 5.0 mL of 1 M
Activity 3: Investigating Osmosis and Diffusion Through Nonliving Membranes. In this activity, through the use of dialysis sacs and varying concentrations of solutions, the movement of water and solutes will be observed through a semipermeable membrane. The gradients at which the solutes NaCl and glucose diffuse is unproportional to any other molecule, therefore they will proceed down their own gradients. However, the same is not true for water, whose concentration gradient is affected by solute ...
Despite being a necessary source, water's density and volume in large quantities provides a challenge for NASA. Many years ago when space missions were much shorter, NASA was able to provide a large amount of fresh clean water for a small crew. However, as space missions continue to lengthen -with trips far beyond our planets orbit and even to Mars- and their participants multiply, providing fresh water for missions of such grand proportions would occupy a large amount of space and prove to be quite heavy. NASA quickly realized that this old way of doing things was no longer practical. So, instead of attempting to bring large quantities of fresh water into space, NASA took to creating water purification systems that could recycle their limited amount of
Trickling Filters and Membrane Bioreactors are focused on in this paper. Trickling Filters: Trickling Filter (TF) reactors consist of a vertical column packed with biofilm supporting media.
π is equal to the osmotic pressure, V is equal to the cell volume and B is the intracellular solids (Hall). Ponder’s R value is the ratio of intracellular solvent volume to the water in its environment; R=(Vi -b)/W. These two equations are related because Ponder’s R value is a measure of how much of an osmometer a cell is while the van’t Hoff relation shows what the osmotic pressure is, both inside and outside the cell. Overall cell membrane permeability can be measured by Ponder’s R value while the osmotic pressure differentials between the external environment and the internal environment are seen with the van’t Hoff relation (Hall). Cells evolved to become great osmometers, but not perfect osmometers, in order to provide a way for solutes to move along permeable membranes. The van’t Hoff relation permits organisms to live in environments of varying osmolarity because regulating solute concentration within a cell can increase or decrease the cell’s affinity for osmosis (Darnell et al). Ponder’s R value, on the other hand, shows how a cell can never become a perfect osmometer. If a cell could become a perfect osmometer, it could cause cell lysis or shrinkage of the cell (Hall). The avoidance of perfect osmometry can be seen within the human erythrocyte as a small portion of cell water will not take part in an osmotic exchange due to tonicity within its
The bacteria and wastewater is mixed in an aeration tank and therefore the contaminants are removed by action of sorption and series of breakdown by the bacteria.
1999, 71, 181-215. Minear, R., Amy, G.. Water Disinfection and Natural Organic Matter: History and Overview. ACS Symposium Series -. 1996, 649, 1-9. Richardson, S. Water Analysis: Emerging Containments and Current Issues. Journal of Analytical Chemistry. 2003, 75, 2831-2857.
The aim for this experiment is to find the most cost effective method for purifying hard water.