Chemically Activated Cow Bone for Increased Fluoride Removal in the Context of Life Cycle Assessment (LCA) of Fluoride Adsorbent Teshome L.

Transcription

1 Chemically Activated Cow Bone for Increased Fluoride Removal in the Context of Life Cycle Assessment (LCA) of Fluoride Adsorbent Teshome L. Yami Advisors: Elizabeth C. Butler (Dr.), David A. Sabatini (Dr.) CEES, University of Oklahoma 2015 OU International WaTER Conference September 22, 2015 Norman, Oklahoma 1

2 Outline Introduction Objectives Methods Results and discussion Conclusions 2

3 Introduction Elevated fluoride concentration affects human health. Bone char has been widely evaluated for fluoride removal; low capacity needs further enhancement. Chemical activation of biomaterials produces higher specific surface areas than thermal activation; has not been studied for cow bone. Production of fluoride adsorbents can cause negative environmental impacts; Life Cycle Assessment (LCA) can evaluate environmental impacts. Bone deformation Cow bone Bone charring Bone char 3

4 Objectives Improve the fluoride adsorption capacity of cow bone using chemical activation in place of thermal activation. Evaluate environmental impacts of fluoride adsorbents; identify life cycle stage with greatest negative environmental impacts. Methods Cow bones were exposed to varying concentrations of chemical activating agents: H 2 SO 4 acid H 3 PO 4 acid KOH ZnCl 2 4

5 Methods CAB was evaluated in batch tests and characterized to explain increased fluoride removal capacity. Quantity of CAB regained after chemical activation and their associated production cost was evaluated Field column studies were conducted to evaluate the performance of the adsorbents. Environmental impacts of fluoride adsorbents were evaluated using LCA. 5

6 Results and discussion: Batch isotherms of CAB 11 A B Adsorbent 30% HSCB 30% HPCB 30% ZnCB 30% KCB 50% KCB Bone char Q 1.5 (mg/g) Chemical activation using sulfuric and phosphoric acid achieved four fold higher fluoride adsorption capacity than bone char Potassium hydroxide activation produced three fold adsorption capacity than bone char 6

7 Results and discussion: Field testing of CAB Conducted column study using two ground waters in Rift Valley, Ethiopia Note: C o = 10 mg/l RW1- Well # 1 RW2 Well # 2 Media Bed volumes BC-RW1 100 WHO Guideline value 1.5 mg/l BC-RW % KCB- RW1 50% KCB- RW Field test result same as the laboratory (four fold higher fluoride removal capacity than bone char) 7

8 Results and discussion: Effect of chemical activation Results Chemical and activation discussion: of cow Effects bone: of chemical activation Did not increase SSA Did not change PZC (same as bone char) However, it increased fluoride adsorption capacity of cow bone (four fold) than bone char Combined chemical and thermal activation: Adsorbent 30% HSCB % ZnCB % KCB % KCB-540 Bone char Q 1.5 (mg/g) Increased fluoride adsorption capacity compared to bone char Had similar results (four fold increase) as chemical activation alone One step chemical activation is preferred 8

9 14 Results and discussion: Effect of chemical activation Observed new minerals: Bassanite and monetite These minerals were not present in bone char These minerals are thought to be responsible for increased F- removal capacity; subject of ongoing research. 9

10 Results and discussion: Adsorbent mass recovery and production cost Table 1 Quantity of material retained Adsorbent Mass before activation (g) Mass After activation (g) Percentage of mass retained (%) 30% HSCB % HPCB % KCB % KCB Bone char Chemical activation produces higher mass of adsorbent per unit mass of starting material than thermally activated cow bone (Table 1). The total costs of production of chemically and thermally activated cow bone were found to be $0.30/ kg and $0.83/ kg, respectively. 10

11 Results and discussion: LCA Table 2 Adsorbent mass required to meet the functional unit (kg) Adsorbents Q 1.5 (mg/g) Total mass of adsorbent (kg) Ref. Activated alumina Brunson, unpublished Bone char Brunson & Sabatini, 2009 Amended wood char Brunson and Sabatini, in review Treated alum waste Sujana et al., 2005 Aluminum oxide amended wood char (AOWC) had the highest overall negative environmental impact in all impact categories due to its low fluoride adsorption capacity (Table 2.) Bone char and treated alum waste had the lowest environmental impact due to their higher adsorption capacity compared to AOWC (Table 2.) 11

12 Results and discussion: Process contribution Damage assessment of adsorbents conducted considering raw materials acquisition, adsorbent manufacturing, and waste management, life cycle stages indicated that: Raw materials acquisition is the life cycle stage that contributed most to negative environmental impact of AOWC to human health, ecosystems quality, and resources. For activated alumina (AA), adsorbent manufacturing life cycle stage contributed most to negative environmental impact to human health, and resources. 12

13 Results and discussion: LCA For activated alumina, transportation by ship had lower impact than aircraft transport for respiratory inorganics impact categories Respiratory inorganics 13

14 Conclusions CAB had four-fold higher capacity than thermally activated bone char; batch and field. Formation of monetite and bassanite during chemical activation of cow bone is thought to be responsible for the four- fold increase in fluoride adsorption. CAB achieved a higher mass of adsorbent per unit starting material due to less fines lost than thermal activation. 14

15 Conclusions CAB was found to be a cost-effective production process. Higher fluoride adsorption capacity reduces environmental impacts Transportation of adsorbents from abroad produced higher impacts; locally produced high efficiency adsorbents are desirable Regeneration could mitigate the impacts for human health and ecosystems. 15

16 Acknowledgements This work was funded by the WaTER Center, Sun Oil Company Endowed Chair, Ken Hoving Graduate College Fellowship and the National Science Foundation (NSF) (CBET ). Special thanks to Junyi Du, Laura R. Brunson (Dr.) and Jim F. Chamberlain (Dr.) for their collaboration on the LCA work. I would also like to thank Anisha Nijhawan for her in put on this work. References Amini M, Kim M, Karim CA, Thomas R, Majid A, Klaus NM, Mamadou S, and CJ Annette (2008) Statistical modeling of global geogenic fluoride contamination in groundwaters. Environ Sci Technol 42 (10): Apambire WB, Boyle DR, & Michel FA (1997). Geochemistry, genesis, and health implications of fluoriferous groundwaters in the upper regions of Ghana. Environmental Geology, 33(1), Ayoob S Gupta, AK & Bhat VT (2008). A conceptual overview on sustainable technologies for the defluoridation of drinking water. Critical Reviews in Environmental Science and Technology, 38(6), Brunson LR, Sabatini DA (2009) An evaluation of fish bone char as an appropriate arsenic and fluoride removal technology for emerging regions. Environ Eng Sci 26(12): Jagtap S, Yenkie MK, Labhsetwar N & Rayalu S. Fluoride in drinking water and defluoridation of water. Chem Rev 2012; 112(4),

17 Questions? 17