Abstract
Dual function polymer materials with immobilized Sphingobium Chorophenolicum (SpC) bacterium cells are reported herein that undergo tandem adsorption and biodegradation of phenolic compounds. The cross-linked polymer materials contain β-cyclodextrin (β-CD) with incremental hexamethylene diisocyanate (HDI) cross-linker at variable mole ratios (X = 1, 3, or 6), denoted as HDI-X systems. The adsorptive uptake properties of the insoluble HDI-X polymers (X = 3 and 6) with various phenolic compounds [pentachlorophenol (PCP), 2,4,6-trichlorophenol (TCP), and 2,4,6-trimethylphenol (TMP)] were studied using batch adsorption isotherms. The molecular selective phenol removal (SR) capacity of the HDI-3 and HDI-6 materials was evaluated by electrospray ionization mass spectrometry (ESI-MS). The results were compared against granular activated carbon (GAC) and native β-CD, where 1D/2D 1H NMR spectral characterization of the complexes formed between phenolic guests and a soluble polymer (HDI-1) in aqueous solution provide insight on the intermolecular interactions and the role of cross-linking effects. Immobilization of SpC onto HDI-3 was shown to form a composite polymer/bacterium material. The composite system displays synergistic removal effects due to tandem PCP adsorption and SpC biodegradation to yield by-products such as 2,6-dichloro-1,4-hydroquinone (DCHQ). Apoptosis and cytotoxicity of DCHQ were evaluated using three breast cancer cell lines.
Highlights
Chlorophenols and chloroarenes have been widely used as low-cost and effective pesticides in agriculture and the timber industry over the last century (Dorsey and Tchounwou, 2004)
A key contribution of this study relates to the characterization of the adsorption properties of cross-linked polymer systems and their potential utility as bacterial supports for the in-situ removal and biodegradation of phenolic waterborne contaminants
The adsorptive uptake properties for PCP with the insoluble hexamethylene diisocyanate (HDI)-X polymers (HDI-3 and−6) at ambient pH and 295 K were compared with a commercial granular activated carbon (GAC) adsorbent (Figure 1A)
Summary
Chlorophenols and chloroarenes have been widely used as low-cost and effective pesticides in agriculture and the timber industry over the last century (Dorsey and Tchounwou, 2004). The production of pentachlorophenol (PCP) stands at ca. 50, 000 metric tons yearly despite its ban in the 70’s by Japan and Sweden, as a consequence of fish contamination and other related health concerns (Geyer et al, 1986). A subsequent ban by the USA Environmental Protection Agency (US-EPA) in 1987 resulted due to toxicity concerns to fish, livestock, and humans (Wild et al, 1993; Dorsey and Tchounwou, 2004). Exposure of PCP to humans often occurs via the skin, respiratory and gastrointestinal tracts, where the health effects of PCP relate to its long half-life The carcinogenicity of PCP is attributed to the formation of key reactive metabolites such as quinone, hydroquinone and semiquinone compounds
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