Elsevier

Journal of Hazardous Materials

Volume 168, Issues 2–3, 15 September 2009, Pages 1422-1429
Journal of Hazardous Materials

Static and dynamic sorption of phenanthrene in mangrove sediment slurry

https://doi.org/10.1016/j.jhazmat.2009.03.043Get rights and content

Abstract

The static and dynamic sorption of phenanthrene (Phe) in three types of mangrove sediment slurries (sandy, silty and muddy) were described by three models, namely linear model, Freundlich adsorption isotherm model and Langmuir adsorption isotherm model. The Freundlich adsorption isotherm was the best model to describe the static sorption behavior of Phe in mangrove sediment slurry with the regression coefficients ranging from 0.96 to 0.99. In static sorption, the sorption capacity and sorption intensity were reduced with the inoculation of Sphingomonas, a PAH-degrading bacterial isolate, suggesting that the inoculum even though inactive and/or dead would enhance bioavailability of Phe. On the other hand, the static sorption of Phe was significantly enhanced at high salinity (20 ppt) while no difference was found at low salinities ranging from 5 to 15 ppt. During the dynamic sorption process, i.e. with biodegradation by indigenous microorganisms and the inoculation of Sphingomonas, linear regression was the most suitable model to describe Phe sorption behavior. The partition coefficient α was the highest in silty sediment, followed by sandy sediment and the muddy sediment had the lowest value. These results indicated that the sorption behavior of Phe changed from non-linear to linear when biodegradation took place and the silty mangrove sediment slurry had the highest sorption affinity.

Introduction

The efficiency and effectiveness of bioremediation always vary among contaminated sites, due to the heterogeneity of soil/sediment and their effects on the sorption and desorption patterns of the organic contaminant especially the hydrophobic one such as polycyclic aromatic hydrocarbons (PAHs). PAHs, because of their strong hydrophobicity, are generally associated with the non-aqueous phase in soil/sediment. Luthy et al. [1] reported that the organic compartments in soil determined the sorption behavior of the highly hydrophobic compounds. In saturated soil, partitioning to total organic matter (TOM) or organic carbon was often the main interaction; however, the sorption of hydrophobic contaminants to clay minerals was dominant in dry soil [2], [3], [4]. Hwang and Cutright [5] found that clay in soil was a dominant factor affecting the sorption behavior of PAHs in sediment slurry. Because of the strong association of PAHs with organic fraction and/or clay minerals in soil/sediment, the amount of PAHs available in the aqueous phase is relatively small and depends on the sorption–desorption equilibrium between aqueous and non-aqueous phases.

The static sorption behavior of PAHs onto soil/sediment has been described by three models. They are the linear model [6], [7], the Freundlich model [8], [9] and the Langmuir model [10], [11]; and these models were evaluated under different situations [12], [13]. Salinity was found to be one of the significant factors affecting the biodegradation of PAHs [14], [15], [16], [17]. The physico-chemical properties of soil/sediment, in particular, the amount and nature of organic matter and clay minerals are also important factors leading to different sorption behavior. Mangrove sediment, subject to tidal flushing is often under alternate wet and dry cycles, is known to be rich in organic matter and clay minerals, thus it is unique and different from other soil types [18]. The mangrove sediment properties are also heterogeneous, vary from sites to sites even in a small city like Hong Kong with an area around 1000 km2 [18]. However, the research on sorption–desorption of PAHs in mangrove sediment is rare although many studies reported the biodegradation of PAHs in mangrove sediment [19], [20], [21].

The sorption behavior of PAHs is never static because the PAHs in the aqueous phase will be continuously degraded by the microorganisms in soil/sediment, and the adsorbed compound will be gradually transferred to the aqueous phase [22], [23], [24], [25]. The sorption behavior during biodegradation is therefore dynamic and the three models for static sorption may not be applicable. The present study aims to (i) investigate the static sorption behavior of phenanthrene (Phe), a model 3-ring PAH, in different types of mangrove sediment slurries with and without the inoculation of Sphingomonas sp., a PAH-degrading bacterial isolate; (ii) study the effect of salinity on the static sorption of Phe in silty sediment slurry and (iii) explore the dynamic sorption behavior of Phe during biodegradation by indigenous microorganisms with the inoculation of Sphingomonas sp.

Section snippets

Chemicals and PAH-degrading isolate

Standards of Phe (96%) were purchased from Sigma Chemicals, USA. The stock solution of each PAH compound was prepared by dissolving an appropriate amount of the standard in acetone, with a final concentration of 5000 mg L−1. All solutions were kept in a brown bottle at 4 °C and wrapped with aluminum folds to avoid any light exposure prior to use. Ethyl acetate (A.R.) was bought from Lab Scan Asia Co. Ltd. (Thailand) and was distilled before use. Calcium chloride (CaCl2) and sodium azide (NaN3)

General properties of mangrove sediment

The sediment collected from MP was muddy with 62% clay and a very large surface area of 42.6 m2 g−1, the sediment also had the highest organic matter and nutrient content (Table 1). Conversely, KLH sediment was sandy, with 89% sand and a small surface area of 8.9 m2 g−1. The organic matter content of KLH sediment was also the lowest. Among three sediment types, the properties of HC sediment were somewhat in the middle, it was silty with 24% silt, 21% clay and a surface area of 16.7 m2 g−1.

Static sorption

In all

Discussion

The sorption behavior of PAHs was dependent on the amount and nature of clay minerals and organic matter in sediment/soil [1], [30]. Silt and clay provide larger surface areas and higher cation exchange capacity for the organic pollutant to adsorb onto their surface than sand or bulk soil [2], [31]. The hydrophobic organic pollutant also has a tendency to adsorb onto organic matter. The relative importance of clay and organic matter on the sorption behavior varies from sediment to sediment, and

Conclusions

  • The Freundlich adsorption isotherm was the best model to describe the static sorption behavior of Phe in mangrove sediment slurry while for the dynamic sorption behavior during the process of biodegradation, linear regression was the most suitable model to describe the sorption of Phe onto mangrove sediment.

  • The sorption capacity (kf) and sorption intensity (n) of Freundlich adsorption isotherm were significantly lower in sandy than in muddy and silty sediment slurries and were reduced with the

Acknowledgement

The work described in this paper was supported by a grant from the Research Grants Council of the Hong Kong SAR, China (Project No. CityU 1406/06M).

References (45)

  • J.C. Appert-Collin et al.

    Nonlinear sorption of naphthalene and phenanthrene during saturated transport in natural porous media

    Phys. Chem. Earth Pt. B

    (1999)
  • R.P. Eganhouse et al.

    Solubility of medium molecular-weight aromatic-hydrocarbons and effects of hydrocarbon co-solutes and salinity

    Geochim. Cosmochim. Ac.

    (1976)
  • B.G. Whitehouse

    The effects of temperature and salinity on the aqueous solubility of polynuclear aromatic-hydrocarbons

    Mar. Chem.

    (1984)
  • J. Satyanarayana et al.

    Adsorption studies of caesium on zirconium molybdoarsenate (ZrMAs)

    Waste Manag.

    (1999)
  • R.G. Luthy et al.

    Sequestration of hydrophobic organic contaminants by geosorbents

    Environ. Sci. Technol.

    (1997)
  • C.T. Chiou et al.

    Partition equilibria of nonorganic compounds between soil organic matter and water

    Environ. Sci. Technol.

    (1983)
  • E.M. Murphy et al.

    Influence of mineral-bound humic substances on the sorption of hydrophobic organic compounds

    Environ. Sci. Technol.

    (1990)
  • S.C. Hwang et al.

    Impact of clay minerals and DOM on the competitive sorption/desorption of PAHs

    Soil Sediment Contam.

    (2002)
  • S.H. Woo et al.

    Evaluation of the interaction between biodegradation and sorption of phenanthrene in soil–slurry systems

    Biotechnol. Bioeng.

    (2001)
  • A.P. Khodadoust et al.

    Adsorption of polycyclic aromatic hydrocarbons in aged harbor sediments

    J. Environ. Eng. ASCE

    (2005)
  • L.F. Ping et al.

    Phenanthrene adsorption by soils treated with humic substances under different pH and temperature conditions

    Environ. Geochem. Health

    (2006)
  • O. Braass et al.

    Decontamination of polyaromatic hydrocarbons from soil by steam stripping: mathematical modeling of the mass transfer and energy requirement

    Environ. Sci. Technol.

    (2003)
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