1. Novel Porous Material for the Removal of Heavy Metals from Water
Olivia Rush, Mohsen Manjili, Marcia Silva
Results
Focus
Method
Mercury
Lead
Generations of industrial pollution left many fresh water sources awash with harmful contaminants. The main contaminants include heavy metals such as mercury and lead, bacteria, and suspended solids. Current methods for water treatment use chlorine to kill bacteria but do little to remove heavy metals. Having high concentrations of heavy metals in drinking water is especially dangerous due to their ability to inhibit brain development and cause chronic illness. The purpose of the Silva group at WaTA (Water Technology Accelerator) is to identify and remove fresh water contaminants sustainably.
Functionalization requires thorough cleaning, sonication with chemical additives, and repeated heating and cooling steps. This process coats the material, altering its surface reactivity and optimizing its microstructure.
Calculated vs. Experimental equilibrium adsorption plots for lead and mercury. Top plots follow the Langmuir model, while bottom plots follow the Freundlich model.
SEM images of porous material before (left) and after (right) functionalization. Nanostructures are visible on it’s surface.
Lead
The Batch Test consists of Pb/Hg solution and coated material in a sealed, Erlenmeyer flask. The flask is then secured to a shaker, where it shakes for an allotted time.
Batch Test
Constant
Variable
Volume
RPM
Adsorbent mass
Initial Concentration pH
Temperature
Diameter
Time
Column Test
Constant
Variable
Volume
Flow Rate
Sample Interval
Temperature pH
Diameter
Initial Concentration
Time
Adsorbent mass
Desorption cycle
Population of Americans served by water systems with reported violations of the Lead and Copper Rule (2015)
Source: Environmental Protection Agency, 2015
Cycle 1
Cycle 2
Cycle 3
Cycle 4
Removal efficiency
63%
61%
59%
Regeneration cycles for Pb removal with refunctionalization between column tests (above) and regeneration efficiency.
Introduction
The Column Test allows gravity fed filtration through the adsorbent at the bottom of a glass column. Samples are taken over time to measure performance.
A pebble-like, porous material with the natural ability to adsorb toxins from water. When functionalized, it can be far more efficient at adsorbing heavy metals. The Silva group chose to focus on specifically lead and mercury removal due to its overwhelming presence in world waterways. A combination of controlled experiments mimicking common water filtration technology were used to test the novel material’s efficiency. In addition, cyclical desorption and refunctionalization helped to understand the limits of its regeneration and therefore sustainability.
Conclusions
Adsorption data showed acceptable fit to Langmuir and Freundlich isotherm models.
Estimated equilibrium concentration were in agreement with experimental values.
Functionalized particles retained their adsorption capacity in multiple cycles of desorption process.
Acknowledgements
This research was supported by NSF WEP/IUCRC grant. We thank our colleagues from Global Water Center, Biology department and School of Freshwater Sciences (UW-Milwaukee), Patrick Anderson and Heather Owen , who provided insight and expertise that greatly assisted the research.
Desorption is the process of removing absorbed Pb/Hg. This process requires thorough cleaning with concentrated acid
The raw material (left) is functionalized and used in all tests. Particle diameters ranged from microns.
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The Experimental Process After testing, specialized equipment measures the residual concentration of Mercury or Lead.