Development of Solid Ceramic Dosimeters for the Time-Integrative

Sep 26, 2017 - (14) However, there have been no existing studies on the effects of physicochemical characteristics of contaminants as well as the impa...
1 downloads 10 Views 908KB Size
Subscriber access provided by Queen Mary, University of London

Article

Development of Solid Ceramic Dosimeter for the Time Integrative Passive Sampling of Volatile Organic Compounds in Waters Riza Gabriela Bonifacio, Go-Un Nam, In-Yong Eom, and Yongseok Hong Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b03678 • Publication Date (Web): 26 Sep 2017 Downloaded from http://pubs.acs.org on October 1, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Environmental Science & Technology is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 31

Environmental Science & Technology

1

Development of Solid Ceramic Dosimeter for the Time Integrative Passive

2

Sampling of Volatile Organic Compounds in Waters

3

Riza Gabriela Bonifacio1, Go-Un Nam1, In-Yong Eom2, Yong-Seok Hong1,*

4 5 6

1

7 8

Gyeongsan-si, Gyeongsangbuk-do, Republic of Korea 2

9 10 11

Department of Environmental Engineering, Daegu University, 201 Daegudae-ro, Jillyang-eup,

Department of Chemistry, Daegu Catholic University, 330 Geumrak-ri, Hayang-eup, Gyeongsan-si, Gyeongsangbuk-do, Republic of Korea

*

Corresponding author: YS. Hong, email: [email protected], tel: 053-850-6694, fax: 053-8506699

12 13

Abstract

14

Time-integrative passive sampling of volatile organic compounds (VOCs) in water can now be

15

accomplished using a solid ceramic dosimeter. A non-porous ceramic, which excludes the

16

permeation of water, allowing only gas-phase diffusion of VOCs into the resin inside the

17

dosimeter, effectively captured the VOCs. The mass accumulation of 11 VOCs linearly increased

18

with time over a wide range of aqueous phase concentrations (16.9 to 1100 µg L-1) and the

19

linearity was dependent upon the Henry’s constant (H). The average diffusivity of the VOCs in

20

the solid ceramic was 1.46×10-10 m2 s-1 at 25 °C, which was 4 orders of magnitude lower than

21

that in air (8.09×10-6 m2 s-1). This value was 60% greater than that in the water-permeable porous

22

ceramic (0.92×10-10 m2 s-1), suggesting that its mass accumulation could be more effective than

1

ACS Paragon Plus Environment

Environmental Science & Technology

23

that of porous ceramic dosimeters. The mass accumulation of the VOCs in the solid ceramic

24

dosimeter increased in the presence of salt (≥ 0.1 M) and with increasing temperature (4 to

25

40 °C), but varied only slightly with DOM concentration. The solid ceramic dosimeter was

26

suitable for field test and measurement of time-weighted average concentrations of VOC

27

contaminated waters.

28 29

Keywords: volatile organic compounds, time integrative passive sampling, ceramic dosimeter,

30

water and groundwater monitoring, diffusion

31 32

1. Introduction

33

Volatile organic compounds (VOCs) are widely known to contaminate not only the

34

atmosphere, but also water and soil systems. Most known VOCs such as benzene derivatives and

35

chlorinated organics are carcinogenic1 and thus pose environmental threats and health risks.

36

Although they are easily vaporized under normal atmospheric conditions, their leakage into the

37

subsurface environment leads to the contamination of soil and groundwater systems2. Moreover,

38

VOCs are of lower molecular weight than most persistent organic pollutants and are therefore

39

more soluble and easily transported to other environments such as surface water3. The number of

40

studies on VOC contamination has significantly increased over the last few decades4 suggesting

41

the importance of their impact at the present time. Therefore, it is critical to detect and

42

appropriately quantify these contaminants in the environment.

43

Conventional water sampling involves the use of pumps or grab sampling from surface

44

water and groundwater. Some of the disadvantages of this sampling method are its inability to

2

ACS Paragon Plus Environment

Page 2 of 31

Page 3 of 31

Environmental Science & Technology

45

monitor the contaminant concentration for long periods of time and risk of distorting the

46

contaminant concentrations when purging wells in the case of groundwater sampling. These

47

challenges have been met with the introduction of passive dosimetry5. Passive sampling devices

48

work by the diffusion of contaminants through membranes and are driven solely by changes in

49

the chemical potential. Conventional passive samplers are based on the equilibrium absorption or

50

adsorption and trapping of contaminants and can only be deployed for an extended period of

51

time to measure the time-weighted average (TWA) concentrations, but not for the instantaneous

52

concentrations5. These equilibrium-based passive samplers have been developed, which are able

53

to measure contaminant concentrations based on equilibrium partitioning6. Such samplers are

54

commonly made up of polymeric materials such as polydimethylsiloxane (PDMS) and

55

polyoxymethylene (POM), whose VOC absorption properties have been previously investigated7.

56

On the other hand, kinetic-based passive samplers use materials with a high absorption capacity

57

enclosed in an inert material such as a ceramic. For these samplers, the concentrations are

58

diffusion-based and cumulative over time, which enables the measurement of the time-integrated

59

concentration.

60

One of these sampling devices involves the use of ceramic materials through which the

61

contaminants diffuse into the contained sorbent. Several studies have proven their applicability

62

for time-integrated and long-term water monitoring8–11. The ceramic holds a sorbent with a high

63

absorption capacity to ensure maximum diffusion and the sorbent can vary depending on the

64

contaminants of interest. Moreover, the ceramic dosimeter is inert and does not swell, unlike in

65

the case of polymeric samplers. Its simplicity and robustness obviate the need for the frequent

66

calibration, thereby reducing its cost and increasing its reusability. The sampling of volatile

3

ACS Paragon Plus Environment

Environmental Science & Technology

67

organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs) in groundwater field

68

samples has been carried out using ceramic dosimeters

69

Amberlite IRA-743 have been found to be suitable sorbents for VOCs and PAHs, respectively12.

70

The use of bioassays has also been found to be compatible with the ceramic dosimeters using

71

activated carbon sorbents for PAHs10 and dioxins13. Organophosphorus flame retardants and

72

brominated hydrocarbons in river water samples have been investigated using ceramic

73

dosimeters with HLB (hydrophilic-lipophilic balance) sorbents14. However, there have been no

74

existing studies on the effects of physicochemical characteristics of contaminants, as well as the

75

impacts of environmental variables on the dosimeter performances, which extends the

76

application of the dosimeter to wider range of contaminants and environments.

8–11

. Dowex Optipore L-493 and

77

In the present study, a solid ceramic dosimeter packed with Dowex Optipore resin is

78

developed to monitor the VOC contamination in aqueous systems. Eleven VOCs with a range of

79

Henry’s constants (from 0.052 to 0.682) are selected, including the hydrocarbons found in fuels

80

(benzene, toluene, ethylbenzene, p-xylene and 1, 3, 5-trimethylbenzene), chlorinated solvents

81

and degreasers (trichloroethene, tetrachloroethene, 1,2-dichloroethane, 1,1,2-trichloroethane,

82

chlorobenzene, 1,2-dichlorobenzene) to study the performance of the dosimeter in various

83

environmental conditions. Unlike in previously cited reports where the ceramic is a water-

84

saturated porous membrane, the ceramic employed for this study is a dense solid material which

85

is impervious to water, but allows gas phase VOCs to diffuse through its micropores.

86 87

2. Materials and Methods

88

2.1 Mathematical Background

4

ACS Paragon Plus Environment

Page 4 of 31

Page 5 of 31

Environmental Science & Technology

89

The solid ceramic dosimeter consists of two parts, a ceramic tube and strong sorbent or

90

resin inside of the tube. The diffusion of VOCs in the cylindrical tube is ubiquitously radial and

91

their diffusion in the ceramic is fast due to the small thickness (1 mm) of the ceramic and, hence,

92

the quasi steady state of VOC diffusion can be attained quickly. At steady-state, the diffusion

93

equation becomes a function of the radius r as follows:

94

d  dCg  r = 0, dr  dr 

a