THE USE OF DYE ADSORPTION RATE TO DETERMINE THE REMAINING SERVICE LIFE OF ACTIVATED CARBONS Presented by Adam Redding, PhD Tuesday, October 27 th, 2015 CA-NV AWWA AFC 2015 2015 Evoqua Water Technologies LLC
Presentation Overview Activated Carbon Background General properties Importance of pore size distribution The Dye Test Performance prediction Identifying carbon age Conclusions 2015 Evoqua Water Technologies LLC PAGE 2
Preview: Part I: Predicting 1,2-dichloroethane breakthrough. Norm. Breakthrough = (62 * Iodine) + (504 * Dye) - 64500 2015 Evoqua Water Technologies LLC PAGE 3
Preview: Part II: Quantifying organic fouling Lake Ontario. Dye Number 2015 Evoqua Water Technologies LLC PAGE 4
Preview: Part II: Quantifying organic fouling Ohio River. Dye Number 2015 Evoqua Water Technologies LLC PAGE 5
Activated Carbon In a Nutshell Common Sources Coal Bituminous Anthracite Lignite Coconut Shell Wood Properties Strong affinity for organic contaminants. Performance determined by porosity and surface chemistry. Porosity varies with source material and activation method. Surface chemistry varies with activation method. 2015 Evoqua Water Technologies LLC PAGE 6
Activated Carbon: Porosity Pore volume distribution shows internal structure of carbon. Capacity is determined by micropores. Adsorption Rate is determined by mesopores. Increased mesopores results in increased performance. 2015 Evoqua Water Technologies LLC PAGE 7
Enhanced Coconut-Based Carbon: Porosity 2015 Evoqua Water Technologies LLC PAGE 8
Is a difference visible? 2015 Evoqua Water Technologies LLC PAGE 9
The Dye Method A sample of ground carbon is mixed with a known concentration of dye. The dye and carbon are allowed to mix for 90 minutes. The amount of dye that adsorbs in 1 hour is calculated by measuring the remaining amount of dye at set intervals. 2015 Evoqua Water Technologies LLC PAGE 10
The Dye Method 2015 Evoqua Water Technologies LLC PAGE 11
The Dye Method: Rationale Desires for Method Simple minimal requirement for equipment. Quick yields a result within several hours. Reproducible multiple tests yield comparable results. Why use a dye? Concentration can be determined photometrically by measuring absorption at a specific wavelength. Multiple types and molecular sizes available to probe carbon structure. 2015 Evoqua Water Technologies LLC PAGE 12
The Dye Method: Details GAC ground and wet sieved to 325 400 US Mesh. Phosphate buffer used to maintain ph 7.2. 0.1% weight carbon solution Stir plate used to maintain uniform mixture. Carbon allowed to wet for at least 20 minutes prior to start. Dye dosed at time zero and samples pulled at intervals thereafter. Concentration determined via spectrophotometer. 2015 Evoqua Water Technologies LLC PAGE 13
The Dye Method: Results v. Time (hr) 2015 Evoqua Water Technologies LLC PAGE 14
The Dye Method: Results v. Square Root Time (hr 1/2 ) 2015 Evoqua Water Technologies LLC PAGE 15
The Dye Method: Interpretation Intraparticle Diffusion Model Loading ( mg / g) = IDC Time( hr) IDC = Intraparticle Diffusion Rate Constant = Dye Number Important Test Conditions Dye concentration in solution must remain relatively constant during test period. Loading of dye on carbon surface must not be so high as to be approaching a maximum. 2015 Evoqua Water Technologies LLC PAGE 16
Putting the Dye Method to Use: Groundwater treatment for 1,2-Dichloroethane Carbon A B C D E Source Material Coconut Virgin Reagg. Bituminous Virgin Non- Reagg. Bituminous React. Non- Reagg. Bituminous Lignite Apparent Density (g/ml) Iodine Number (mg/g) Dye Number (mg/g) 1,2-DCA Breakthrough (BV) Normalized Breakthrough (BV/AD) 0.49 0.59 0.51 0.49 0.39 1220 950 890 900 700 36 47 36 42 96 14220 10577 4510 5839 10577 29020 17927 8843 11916 27121 2015 Evoqua Water Technologies LLC PAGE 17
Groundwater treatment for 1,2-Dichloroethane: Using Either Iodine or Dye Number to Predict Performance Iodine Number Dye Number 2015 Evoqua Water Technologies LLC PAGE 18
Groundwater treatment for 1,2-Dichloroethane: Using Iodine and Dye Number to Predict Performance Norm. Breakthrough = (62 * Iodine) + (504 * Dye) - 64500 2015 Evoqua Water Technologies LLC PAGE 19
The Dye Test: a one trick pony? Many utilities using carbon to treat taste & odor and/or disinfection byproduct precursors. No readily available method for determining degree of fouling from organic matter. Needs to use full-scale (unground) grains as to not change influence of fouling. Longer contact time needed since grains are larger: sieve out 20x30 fraction to speed up the process Measures Diffusion Rate Organic fouling slows diffusion Fouling increases with carbon age Dye adsorption should slow with age 2015 Evoqua Water Technologies LLC PAGE 20
Lake Ontario Utility: Hypothesis supported? 2015 Evoqua Water Technologies LLC PAGE 21
Hypothesis supported? Maybe 2015 Evoqua Water Technologies LLC PAGE 22
Hypothesis supported? Yes. 2015 Evoqua Water Technologies LLC PAGE 23
How does the virgin carbon fit the trend? Lake Ontario Utility More data is needed for younger carbons! 2015 Evoqua Water Technologies LLC PAGE 24
Hypothesis supported: Ohio River Water? 2015 Evoqua Water Technologies LLC PAGE 25
Dye adsorption results: first 6 hours 2015 Evoqua Water Technologies LLC PAGE 26
Data reduced to calculate IDC ( Dye Number ) 2015 Evoqua Water Technologies LLC PAGE 27
Hypothesis supported? Yes. 2015 Evoqua Water Technologies LLC PAGE 28
What about Iodine Number? Shows drop in performance but does not continue steadily with age. Capacity does not appear to diminish consistently. Cannot alone be used to show how spent each contactor/carbon has become. 2015 Evoqua Water Technologies LLC PAGE 29
The Dye Number: Recap Dye Number indicates level of enhancement. Acts as a predictor of performance. Offers an advanced specification method for the water utility. Provides additional value beyond the Iodine Number. Can quantify level of fouling as a function of carbon age. 2015 Evoqua Water Technologies LLC PAGE 30
Thank you for your attention. Questions? Adam M Redding, PhD Scientist, Activated Carbon Products Evoqua Water Technologies LLC 201 S Potter Street Bellefonte, PA 16823 E-mail: adam.redding@evoqua.com 2015 Evoqua Water Technologies LLC
Additional Supporting Data 2015 Evoqua Water Technologies LLC PAGE 32