The Science of Water NanoSens水科学nanosense.pptVIP

Nanofiltration Environmental scientists and engineers are creating nanomembranes to filter contaminants from water cheaply and effectively Water Filtration Methods Sand, Gravel, and Charcoal Filtration Pouring water through sand, gravel, or charcoal are simple and inexpensive methods of cleaning water Small Contaminants Pass Through Sand, gravel, and charcoal don’t filter out some contaminants, like bacteria viruses industrial pollutants agricultural pollutants salt Question Membrane Filter Technology I A membrane is a thin material that has pores (holes) of a specific size Membranes trap larger particles that won’t fit through the pores of the membrane, letting water and other smaller substances through to the other side Membrane Filter Technology II There are four general categories of membrane filtration systems Microfiltration Ultrafiltration Nanofiltration Reverse Osmosis Membrane Filter Technology III Microfiltration Typical pore size: 0.1 microns (10-7m) Very low pressure Removes bacteria, some large viruses Does not filter small viruses, protein molecules, sugar, and salts Ultrafiltration Typical pore size: 0.01 microns (10-8m) Moderately low pressure Removes viruses, protein, and other organic molecules Does not filter ionic particles like lead, iron, chloride ions; nitrates, nitrites; other charged particles Nanofiltration Typical pore size: 0.001 micron (10-9m) Moderate pressure Removes toxic or unwanted bivalent ions (ions with 2 or more charges), such as Lead Iron Nickel Mercury (II) Reverse Osmosis (RO) Typical pore size: 0.0001 micron (10-10m) Very high pressure Only economically feasible large scale method to remove salt from water Salty water cannot support life People can’t drink it and plants can’t use it to grow How RO Works Osmosis is a natural process that moves water across a semipermeable membrane, from an area of greater concentration to an area of lesser concentration until the concentrations are equal To move water from