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Membrane Technology Review: Materials, Costs, and BenefitsVictoria Hernandez, Chemical Engineering, Class of 2018
Tirupalavanam Ganesh, PhD, Assistant Dean, Engineering EducationSchool for Engineering of Matter, Transport, and Energy
Membrane Materials Used to Treat Drinking Water and Wastewater: Pros and Cons
IntroductionThis research is focused on the Engineering theme of Sustainability and the Grand Challenge of Providing Access to Clean Water. Population growth and climate change both have an impact on global water supply[1]. Utilizing new sources of water is becoming increasingly important. Membrane technology allows for the use of previously untreatable water resources, as well as the recycling of wastewater to be used again as drinking water. Membrane technology has the potential to revolutionize the water treatment process, with minimal use of chemicals and energy[2], and preservation of the chemical and biological properties of materials in the water, [3] allowing for nutrient extraction.
Membrane MaterialsGoals[1]:• Maximize selectivity and productivity• Reduce fouling, therefore increase membrane life• Minimize cost to manufacture • Be operational on a large scale
Materials (See Table 1)• Polymer: Integrally Skinned and Thin Film Composite• Inorganic: Mesoporous Ceramic• Nanomaterials• Biomaterials
A Comparison of Membrane Pros and Cons for Different Membrane Materials (Table 1) [1]
ProsWell establishedStrongWithstands cleanings
Fouling resistant Long Life
Integrally Skinned
Membranes
Thin Film Composite
Reactive/Catalytic Surface
Zeolite Coatings Mixed Matrices
Nanoparticle Thin-Film
Composites
Zeolite Thin-Film
CompositesAquaporins Aligned
NanotubesBlock
Copolymers
Mesoporous Ceramic
Membranes
ConsExpensiveNot good for drinking water
Low packing density
ProsSmooth surfaces
fouling resistantCheapEasy to
manufacture
ConsLimited temp.
and pH rangeChlorine
intolerantBio-degradable
ProsFilm over polymer
membrane reduces fouling
Film is separate from membrane
ConsSimilar fouling
problems as with polymer membranes
ProsSelf-cleaningEnhanced
selectivity
ConsHigher costLow packing
densityEnergy
requirements
ProsThermo-chemical
stabilityFouling resistantTunable
selectivity
ConsThin coatings less
efficientDefect proneExpensive
ProsBest of both
organic and inorganic
Selective tuningBiofouling
resistant
ConsExpensiveRelatively newShort-lived anti-
microbial particles
ProsProductivity
increaseFouling resistantAntimicrobial
activity
ConsExpensiveReduced
selectivitySome types show
decreased permeability
ProsIncreased
permeabilityDecreased fouling
ConsExpensive (but
minimal material requirements)
ProsStrongerLower energy
costIncreased
selectivity and productivity
ConsExpensiveDifficult to
produce in large amounts
ProsFar superior
productivity and selectivity
ConsExpensiveDifficult to extract
large amounts
ProsCan be scaled upPotential for self-
cleaningSoftMore selective/
productive
ConsProne to defectsWeaker
Background• Tertiary water treatment[4] • Used in place of flocculation, sedimentation, adsorption, ion exchangers, extraction, distillation[2] (see figure 1)• Impacted by pressure and electrochemical gradients[2] • Operated under cross- flow and dead-end flow[3] (see figure 2)
Further ResearchStudy zeolite materials more closely and their potential uses in the water treatment process. Investigate the potential benefits zeolites can bring to membrane technology, including studying both their coatings and thin film composites.
References[1] M. Pendergast, E. Hoek. “A review of water treatment membrane nanotechnologies,” Energy & Environmental Science, vol. 4, pp. 1946-1971, April 2011.[2] “Membrane Technology,” Water Treatment Solutions, Lenntech, 1998-2015. [Website]. Available: http://www.lenntech.com/membrane-technology.htm. Accessed: March 30, 2015.[3] H. Friedrich, V. Mertsch. “Basics of Membrane Technology,” in Membrane Technology for Waste Water Treatment, 2nd Edition, vol. 2, Ministry for Environment and Nature Conservation, Agriculture and Consumer Production of the Federal state of North Rhine-Westphalia: 2003, pp. 27-55.[4] V. Gupta et. al. “Chemical treatment technologies for waste-water recycling – an overview,” RSC Advances, vol. 2, pp. 6380-6388, April 2012.
Dead-End Flow Cross-Flow
Microfiltration• Bacteria and some
viruses• Oil emulsions• Yeast and Fungi
Ultrafiltration• Viruses• Proteins• Polysaccharides• Colloidal Solids• Nucleic Acids
Nanofiltration• Antibiotics• Mercury• Ions (multivalent)
Reverse Osmosis• Organic Acids• Ions (univalent)
Figure 1: Stages of Filtration in which membranes are most commonly used (above) [3]
Decreasing Pore Size
Figure 2: Dead-end flow (left) vs Cross-flow (right)