PAHs for Sediment Remediation Dr. Mei Xin, Dr. Susnata Samanta, - - PowerPoint PPT Presentation

• Dr. Mei Xin, Dr. Susnata Samanta, David Flannery

(Cabot Corporation, Boston, MA)

• Dr. Danny Reible

(Texas Tech. University, Lubbock, TX)

January 10, 2017

Evaluation of Activated Carbons for Sequestration of PCBs and PAHs for Sediment Remediation

A rich and unique history

▪ Over 130 years in operation

▪ Founded 1882 ▪ NYSE: CBT since 1968

▪ Global specialty chemicals and performance materials company ▪ 45 manufacturing sites in 21 countries ▪ Core technical competencies in fine particles and surface modification ▪ FY2016 sales: $2.4B

About Cabot Corporation

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Cabot Norit Activated Carbon

▪ World’s largest producer of activated carbon ▪ Manufacturing since 1916

▪ 9 plants

▪ Sold globally ▪ Cabot makes activated carbon from many raw materials, including:

▪ Lignite coal ▪ Bituminous coal ▪ Coconut shell ▪ Wood ▪ Peat

▪ Products used widely in potable water and wastewater treatment

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What is activated carbon?

• Large internal surface area
• 1 teaspoon (5 g) has the same surface

area as a football field (1,000m2/g)

• Large internal pore volume (cc's/g)
• Large adsorption capacity

Characteristics

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Activated carbon forms

POWDER GRANULAR

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EXTRUDATE

Activated Carbon for Sediment Remediation

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Objective

 Freundlich sorption isotherms (Kf, 1/n) and adsorption kinetics for PCBs and

PAHs required for sediment remediation design with activated carbons

 Information for engineering firms to aid in design of sediment remediation

caps using CAPSIM

1.

Adsorption capacity vs. kinetics

2.

Relative performance of PAC vs. GAC

3.

Impact of natural organic matter (NOM) on contaminant adsorption

4.

Relative performance of carbons from different raw materials

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To provide information to help in design of caps

Experimental Design

Topic Description Sample prep

• All experiments conducted in separate batches for 1L (PAH)

and 250 ml (PCB) water solutions in amber bottles Water matrix

• 1L deionized water (DI) plus 350 mg of instant ocean salt and

100 mg of sodium azide

• NOM loaded water: Suwannee River NOM (50 mg into 1L

water solution) Activated carbons

• Powdered AC (PAC), granular AC (GAC)
• Raw materials: lignite, bituminous, coconut shell

Contaminants

• PAHs: naphthalene, phenanthrene, pyrene, benzo(a)pyrene

(EPA 8270)

• PCB congeners: 18, 52, 77, 101, 118, 151 (77, 118: dioxin-like)

(PDMS (polydimethylsiloxane) fiber extraction / GCMS) CAPSIM Model

• All modeling used CAPSIM developed by Prof. Danny Reible

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Bench Scale Adsorption Results

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Kinetics Study – PAC vs. GAC

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 At equilibrium state, PAC and GAC adsorb same amount of PAHs  PAC and GAC both show fast adsorption for low molecular weight PAHs

(naphthalene MW 128)

 PAC shows much faster adsorption than GAC for high molecular weight PAHs

(pyrene MW 202 )

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Freundlich Adsorption Isotherms

Lignite carbon is resilient to NOM impact

· Lignite carbon was exposed to NOM 25ppm for 30 days prior to the adsorption measurement

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Compared to lignite carbon, coconut shell carbon is more sensitive to NOM impact

PHENANTHRENE PCB 118

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25 50 75 100 5 10 15 AC Capacity NOM /AC Capacity DI, % PCB-118 Conc. (ng/L) Coconut AC Lignite AC 25 50 75 100 125 150 50 100 150 AC Capacity NOM /AC Capacity DI, % Phenanthrene Conc. (ug/L) Coconut AC Lignite AC

 Meso and macro-pores of lignite carbon minimize NOM impact  NOM impact on lignite and coconut carbons is consistent with

results from potable water and wastewater treatment plants

CAPSIM Model Simulations

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CAPSIM Cap Design Model Parameters

Parameter range analyzed in this project Parameter Description Low Medium High Reactive cap Sand + activated carbon Used for all scenarios (15 cm cap + 30 cm sediment) % Activated Carbon Mass % of activated carbon in cap 1% 5% 10% Upwelling rate Fresh water up-flow in sediment (cm/day) 1 3 PAH concentration PAH concentration in pore water (µg/l) 100

• 3000

PCB concentration PCB concentration in pore water (ng/l) 1

• 100

NOM Natural organic matter in pore water (ppm)

• 25

Half-life rate Mass transfer rate of contaminant to AC Local equilibrium 1 day 30 days

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CAPSIM Modeling – Naphthalene

PAHs and PCBs quickly breakthrough a 100% sand cap

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Sand (15 cm) Sediment (30 cm)

Upwelling Rate Upwelling Rate

Sand cap without activated carbon at low and high upwelling rates



LIGNITE PAC



COCONUT PAC

CAPSIM Modeling – Naphthalene

Lignite and coconut PAC performance is similar

(10% PAC, 1 cm/day upwelling, 25 ppm NOM)

 No PAH breakthrough after 100 years with either activated carbon

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

LIGNITE PAC



COCONUT PAC

CAPSIM Modeling – PCB 101

Lignite and coconut PAC performance is similar

(5% PAC, 1cm/day upwelling, 25 ppm NOM)

 No PCB breakthrough after 100 years with either activated carbon

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

PAC



GAC

CAPSIM Modeling – PCB 77

PAC is better than GAC at high upwelling rate

(20%AC, 3cm/day upwelling, 25ppm NOM)

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Carbons made from different feedstocks perform the same under both conditions



LIGNITE PAC



BITUMINOUS PAC

CAPSIM Modeling - Pyrene

Need more bituminous AC to achieve the same performance as lignite AC for high MW PAHs

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 Conditions: 1% AC, 1 cm/day upwelling rate, no NOM  When carbon dose is 5%, there is no significant difference between

lignite and bituminous carbons

Conclusions

Investigation Conclusions Capacity vs. Kinetics

• Adsorption capacity is the same for PAC and GAC although GAC may absorb less due to

slower kinetics of sorption

• HOCs have low solubility and migrate slowly, so kinetics is not important if low upwelling

PAC vs. GAC

• Adsorption rate of HOCs is much faster with PAC
• PAC may be a better solution than GAC for PCBs if there is high upwelling rates because

kinetics become very important Impact of NOM

• NOM at 25 mg/L reduces performance of coconut carbon by up to a factor of 5
• NOM at 25 mg/L has negligible impact on performance of lignite carbon
• Conclusion – consider lignite carbon rather than coconut carbon in NOM

Feedstocks

• All carbons perform about the same for PAHs and PCBs when there is no upwelling
• All GACs perform the same (quick breakthrough) when there is very high upwelling

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For further information, please contact:

Billy Barron Regional Marketing Manager Cabot Norit Activated Carbon T +1 678 297 1549 M +1 470 281 8465 Billy.Barron@cabotcorp.com One Point Royal 4400 North Point Parkway Suite 200 Alpharetta, Georgia 30022 www.cabotcorp.com Battelle Conference Booth #431

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Acknowledgements

• Prof. Danny Reible, PhD PE BCEE NAE

Donovan Maddox Distinguished Engineering Chair Texas Tech University Tariq Hussain Ph.D. Candidate Texas Tech University

• Dr. Magdalena Rakowska

Postdoc Researcher Texas Tech University Xiaolong Shen Ph.D. Candidate Department of Chemical Engineering The University of Texas at Austin

Questions?

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