Sorptive treatment of explosives and heavy metals in water using biochar

Transcription

1 2013 US Biochar Conference U. Mass, Amherst, MA, USA October 14, 2013 Sorptive treatment of explosives and heavy metals in water using biochar Seok-Young Oh 1*, Yong-Deuk Seo 1, Hyun-Su Yoon 1, Myong-Keun Yoon 1, and Dong-Wook Kim 2 1 Department of Civil and Environmental Engineering University of Ulsan, South Korea 2 Department of Environmental Engineering Kongju National University, South Korea

2 Develop indirect benefits from biochar: Environmental application Sorbent: toxic metals & organic pollutants Catalyst: redox mediator for organic pollutants Application for Environmental Remediation Technology

3 Reduction of RDX by dithiothreitol in the presence of biochar RDX Formaldehyde RDX, reductant-free control (biochar only) RDX, biochar-free control (dithiothreitol only) Concentration (mm) Time (hr) (Oh et al., 2013, ET&C)

4 Treatment of AMD by Biochar Concentration (mg/l) (a) Cu Zn ph ph Concentration (mg/l) (Al, Mn) (b) Al Fe Mn SO Concentration (mg/l) (Fe, SO 4 2- ) Time (hr) Time (hr) (Oh et al., 2013, Environ Eng Sci)

5 Mechanisms on removal of inorganic contaminants from water by biochar Carbon fraction Sorption via electrostatic force according to PZC (e.g., surface functional group) Ion exchange between ionizable protons and metal cations Delocalized π-electrons of carbon (Cπ electrons in graphene layer) Non-carbon fraction Sorption to mineral impurities Basic nitrogen group Neutralization by mineral impurities (e.g., CaCO 3, MgCO 3 ) (Uchimiya et al., 2010, J. Agric. Food. Chem; Lu et al., 2012, Water Res.)

6 (Lu et al., 2012, Water Res)

7 Mechanisms on removal of organic contaminants from water by biochar Carbon fraction - π- π Electron donor-acceptor (EDA) interactions Non-carbon fraction Partitioning to non-carbonized fraction - Hydrophobicity - Surface functional groups (Chun et al., 2004, ES&T; Zhu and Pignatello, 2005, ES&T)

8 Energetic Compounds: explosives

9 Hypothesis Biochar may be used as a sorbent to effectively remove toxic explosives and metals from contaminated water.

10 Objectives To characterize various types of biochar as sorbents To evaluate sorption capacity of the biochars for toxic metals (As, Cd, Cu, Pb, and Zn) and explosives (DNT, TNT, and RDX)

11 Reference BC materials Granular activated carbon (GAC) ph= 6.4, S.A.= m 2 /g PZC=6.9, CEC=11.6 meq/100g C: 80.0%, H: 1.0%, O: 11.2%, N: 0.7% Graphite ph= 3.7, S.A.= 13.6 m 2 /g PZC=4.9, CEC=5.4 meq/100g C: 97.44%, H: 0.06%

12 Biochar production: Poultry litter (PL) Pyrolysis (400 o C, 4 h) Biosolid (BS) PL and BS biochar

13 Biochar production: Fallen leaves (Oak tree) Used coffee ground FL Biochar CF Rice straw Corn stalk Pyrolysis (550 o C, 4 h) RS CS

14 Characteristics of PL biochar Elemental analysis (by elemental analyzer) C: 35.1%, H: 2.3%, O: 5.2%, N: 2.7% BET surface area (S.A.): 11.0 m 2 /g ph: 9.8 PZC: 8.2 CEC: 72.5 meq/100g = 26.6 (d=0.335 nm) graphite Intensity (CPS) f q f c c f d f q f c q d (Oh et al., 2013, ET&C)

15 Characteristics of BS biochar Elemental analysis (by elemental analyzer) C: 22.9%, H: 0.4%, O: 13.6%, N: 0.5% Surface area (S.A.): m 2 /g ph: 8.3 PZC: 7.1 CEC: 8.6 meq/100g = 26.6 (d=0.335 nm) graphite Intensity (CPS) f q ff q c c q

16 Characteristics of FL, CF, RS, and CS biochars Types of biochar ph BET SA (m 2 /g) CEC (meq/1 00g) PZC E.A. (%) C H O N FL biochar RS biochar CS biochar CF biochar

17 SEM images of FL, CF, RS, and CS biochars FL CF RS CS

18 XPS spectra of BC materials and biochars intensity (a. u.) C-C ev C-O ev C=O ev GAC Graphite PL biochar BS biochar FL biochar CF biochar RS biochar CS biochar Binding Energy(ev)

19 FT-IR spectra of BC materials and biochars

20 Batch experiments Screw cap 40 ml vial Sorbent: biochars, graphite, or GAC (0.05 ~ 5.0 g) 20 ml of solution including 1) As, Cd, Cu, Pb, or Zn - Initial concentration 100 ~ 200 mg/l - Initial ph 5 ~ 5.5 2) DNT, TNT, or RDX - Initial concentration 25 ~ 50 mg/l - Initial ph 7 Duplicates Control without sorbents - At 25 o C rpm shaking - Duplicate sampling - Equilibrium time: Metals: 24 h Explosives: 3-6 h

21 Chemical analysis Metals: AAS (AAnalyst 700, Perkin Elmer) Explosives: HPLC (Ultimate 3000, Dionex) following an EPA method 8330

22 Langmuir sorption isotherm: Cu q (mg/g) ph GAC BS biochar PL biochar 2 GAC BS biochar PL biochar C e (mg/l) Geosorbent (g)

23 Langmuir sorption isotherm: Zn q (mg/g) 6 4 GAC BS biochar PL biochar ph GAC BS biochar PL biochar C e (mg/l) Zn Geosorbent (g) Zn

24 Maximum sorption capacity in Langmuir sorption isotherm (unit: mg/g) Cd Cu Pb Zn As Graphite GAC PL biochar BS biochar FL biochar RS biochar CS biochar CF biochar

25 Langmuir sorption isotherm: TNT and RDX q (mg/g) 8 6 GAC BS biochar PL biochar q (mg/g) GAC BS biochar PL biochar C e (mg/l) TNT C e (mg/l) RDX

26 Maximum sorption capacity in Langmuir sorption isotherm (unit: mg/g) DNT TNT RDX Graphite GAC PL biochar BS biochar FL biochar RS biochar CS biochar CF biochar

27 Correlation coefficient (R 2 ) between properties of biochar and maximum sorption capacity ph BET SA CEC PZC C H O N O/C H/C Cd Cu Pb Zn As DNT TNT RDX

28 Correlation coefficient (R 2 ) between XPS spectrum ratio of biochar and maximum sorption capacity log[(c-o + C=O + COO)/(C-C)] log(cd) log(cu) log(pb) log(zn) log(as) log(dnt) log(tnt) log(rdx) N/A

29 Blocking of surface functional group: FL and RS biochar Blocking of carboxyl functional group - Saturation with methanol for 6 h - Centrifuging and washing with DIW (x3) Blocking of hydroxyl functional group - Saturation with 1% HCHO for 24 h - Centrifuging and washing with DIW (x3) Dry biochar at 40 o C (6-12 h)

30 Maximum sorption capacity after blocking of surface functional groups: FL biochar (mg/g) No blocking Carboxyl-blocked Hydroxyl-blocked Cd Cu Pb Zn DNT TNT RDX

31 Maximum sorption capacity after blocking of surface functional groups: RS biochar (mg/g) No blocking Carboxyl-blocked Hydroxyl-blocked Cd Cu Pb Zn DNT TNT RDX

32 Conclusions Biochar shows a porous structure, and have a high surface area and embedded carbonate minerals, favorable for the sorptive removal of toxic metals and explosives. Compared to GAC, biochar is competitive as a sorbent for removing Cd, Cu, Pb, and Zn from contaminated water. Compared to graphite and GAC, biochar can also sorb explosives from water.

33 Conclusions Correlation analysis shows that sorption capacity of biochar for cationic toxic metals (Cd, Cu, Pb, & Zn) is related with CEC, O/C, and H/C. It also shows that sorption capacity of explosives is related with BET S.A. and carbon content. XPS analysis and blocking experiments suggest that surface functional groups may be responsible for the sorption of cationic metals to biochar surface. In contrast, carbon contents can account for the sorption of explosives possibly through π-π EDA interaction and hydrophobic sorption.

34 Conclusions Our results suggest that application of biochar can be an attractive & alternative option in environmental remediation through sorption and immobilization.

35 Acknowledgments National Research Foundation of Korea Grant ( ) Ulsan Green Environment Center Grant (2012) BK21 Plus ( )

36 Current work Effect of surface treatment (acid or oxidant) on properties of biochar and sorption capacity Effect of pyrolysis temperature on properties of biochar and sorption capacity Various types of contaminants: pharmaceuticals, halogenated solvents, and pesticides Bio-Energy production from pyrolysis

37 Any Questions?