Management needs to assure delivery of quality products and services and have records of proof. Software programs tailored to your business are a good way to increase productivity and quality. Described here are some software programs designed for activated carbon (AC) users and manufacturers. These software programs increase productivity, quality, archival of records and solve some refractory problems.
Fast AC adsorption performance predictions
Available software is useful for both gas- and aqueous-phase AC applications to quickly determine if carbon can solve problem(s), and how much AC is needed.
Typically, AC users want to remove contaminants from gas-, vapor-, water- or solvent-phases. Using their list of contaminants and concentrations, software is available to rapidly decipher AC performance. Determining contaminants’ breakthrough order and volumes for each contaminant are critical information. Knowing the amount of carbon to clean up a given amount of environmental contamination is rendered. This software program was developed based on 1914 Michael Polanyi model principles for Physical Adsorption. Many scientists have confirmed and advanced derivatives of his adsorption model, up to present day.1
To open this software a user selects gas- or aqueous-phase. To apply this software to solve problems, a user needs to install molecular weight of each compound (up to 30 of interest), with individual concentrations (in gas- or aqueous-phase), adsorbate saturation concentration at process temperature, each refractive index and process temperature. Software is designed to provide individual AC loadings at equilibrium, when influent and effluent are equal and the AC is no longer removing contaminants, and sequential order of AC column breakthrough and volume at breakthrough.
This software provides information at the user’s real-world process temperature and contaminants’ concentrations. Software provides information about isotherms at different temperatures. The rule of thumb is: Higher temperature results in faster AC column elution and lower AC loading capacity at equilibrium. This software provides faster and more economical AC evaluations for expected results from applications, compared to classical American Society for Testing (ASTM) test methods.2
The gas-phase mode delivers the impact of process humidity on organics physical adsorption. Users put in compound names and humidity to get a two page report containing three columns of data, comprised of compound concentration and loading with and without humidity. Small water soluble molecules are sensitive to humidity.
ASTM isotherms software
Classical ASTM Isotherm test methods do not provide software programs to interpret and evaluate lab results obtained by following these standard methods. Software is designed to be compliant with ASTM test methods and provides automated data calculations, graphical and tabular outputs as well as data interpretation and maintains archival records.3
ASTM Isotherm aqueous methods are based on contacting increasing amounts from a few mg to g quantity of 325-mesh carbon with the same volume of liquid. Carbon is ground to a fine powder to decrease time it takes to reach equilibrium. Grinding does not affect the AC pore nano-sized structures, but rather facilitates faster carbon use, increased capacity and reaches final equilibrium quicker.
Nine carbon samples and a blank are put into Erlenmeyer flasks; then a constant amount of contaminated liquid is added to 10 flasks and shaken for 24 hours. You need to perform a few preliminary runs to maximize the carbon dosages and the amount of time to reach equilibrium. Carbon dosages, which take out all of the contamination or none, are not useful. Ideally, you need to use carbon dosages which result in 10-90 percent contaminant removal.
At the end of shaking for 24 hours, or more if needed, the carbon is separated from the liquid and the liquid-phase contaminants are determined. An example of an aqueous isotherm data set and data Freundlich plot (Log-Log) is provided in Figure 1 and Table 1. If you made all of these calculations and graphing by hand, it would take over two to three hours, possibly resulting in errors. Software provides automated calculations, graphing and archiving with increased information accuracy.
Also, this software is useful for ASTM, American Water Works Association (AWWA) and other isotherm based methods — such as methods designed to evaluate AC decolorization performance.
ASTM particle sizing distribution software
Using standard methods can be good for quality control because they harmonize data from different laboratories. Again, ASTM has a well-designed standard method for AC particle size distribution, but leaves processing of raw data up to the users. We have supplied ASTM compliant designed software, which provides tabular and graphical outputs and interprets data, as well as maintained computer archives. An example data set and cumulative graphical output is shown in Figures 2 and Table 2.4
Municipal drinking water plants often purchase granular activated carbon (GAC) based on: Mean particle diameter, effective size and uniformity coefficient. Specifications are designed to obtain water gravity flow through GAC beds Terms are defined as follows:
- Mean particle diameter is the property of AC that influences pressure drop. MPD is the weighted average particle size in millimeters, of a granular adsorbent, which is computed by multiplying the percent retained in a size fraction by the respective mean sieve opening, then summing these values and dividing by 100.
- Effective size is the particle size in millimeters, which corresponds to 10 percent finer on the cumulative particle size distribution curve.
- Uniformity coefficient is the ratio of the particle diameter corresponding to 60 percent finer on the cumulative particle size distribution curve to the particle diameter corresponding to 10 percent finer on the same distribution curve.
Knowing the GAC particle size distribution is necessary in order to provide proper contact of gases or liquids in packed AC beds. Changes in particle size distribution can affect the pressure drop through bed depth and the rate of adsorption in a bed of a given size. Smaller particles provide faster kinetics and sharper mass transfer zones with higher AC loading capacity at equilibrium.
Typically, 100 grams of GAC are put onto a stack of wire meshed screens with a bottom catch pan, and shaken on a Ro-Tap for 10 minutes. Weights on each screen are determined and recorded for entry into the software program. It is important to not blind the screens; if a particle sticks in a wire mesh screen, this inhibits other particles to use this path to the next smaller sized screen below in the stack. This can be avoided by doing a GAC received and dry apparent density (AD). If AD is below 0.350, then only use 50 g of material to charge the screen set; higher AD should use 100 g. Never put more than 200 cc on the top screen before Ro-Tap shaking.
Particles in the micron size are too small for wire mesh sizing. Micron sizes are done by laser micron sizing distribution; this software is not covered in this article.
ASTM hardness and abrasion numbers
This software also facilitates productivity for GAC ASTM hardness number determination methods. Hardness is important for reusing GAC after it is reactivated thermally. Manufacturers can make a family of products by varying furnace activation time — for example, products can vary in density from 0.8 to 0.2 g/cc. Products range in hardness with 0.8 g/cc highest and 0.2 g/cc lowest. Also, 0.2 g/cc has highest total pore volume and 0.8 g/cc lowest total pore volume. These density-hardness activity trade-offs allow manufacturers to provide the best product for different markets.5
Abrasion is more aggressive than hardness. It uses more steel balls than the hardness pan, and is shaken on the Ro-Tap longer compared to ASTM Hardness. For example, you can have two sample runs both with hardness 95, but have abrasion of 84 and 94 after abrasion hardness test method.
Editor’s note: Please be sure to read the rest of this article in our November issue, where Part two will discuss refractive index determination and GAED characterization and benefits.
Acknowledgments:
Henry Nowicki, Ph.D./M.B.A., would like to thank his prior staff — Homer Yute, Dr. Milton Manes and Dr. Mick Greenbank — and present staff — Christopher Brunning and George Nowicki — for contributing to this software and instrumentation.
Sources:
- Milton Manes, Ph.D., Fundamentals of Activated Carbon Adsorption. Available electronically by contacting author.
- ASTM D3860-98 Standard Test Methods for Determination of Adsorptive Capacity of Activated Carbon by Aqueous Phase Isotherm Technique.
- ASTM D5919-96 for Determination of Adsorptive Capacity of Activated Carbon by Micro-Isotherm Technique.
- ASTM D 2862-97 Standard Test Method for Particle Size Distribution of Granular Activated Carbon.
- ASTM D 3802 Standard Test Methods for Ball-Pan Hardness of Activated Carbon.
- Henry Nowicki, et al. Water Conditioning & Purification. Go to wcponline.com and type “Nowicki” into the search box to get reprints.
Henry Nowicki, Ph.D./M.B.A., president of PACS and Activated Carbon Services, provides routine and advanced independent laboratory activated carbon testing, R&D, consulting, expert witness services and short training courses. He also hosted the 34th International Activated Carbon Conference, which took place Sept. 25 – 26, 2014, near Pittsburgh, Pennsylvania, as well as associated carbon courses held Sept. 22 – 27, 2014, and will host the 35th International Activated Carbon Conference in Orlando, Florida, in February 2015. For more information visit Pacslabs.com, call (724) 457-6576 or email [email protected].
