Immobilization of Tetrabromobisphenol A On Pinecone-Derived Biochar
In the past decades, Tetrabromobisphenol A (TBBPA), one of brominated flame retardants (BFR), has been widely used in a variety of commercial and industry applications to improve fire resistance, and it is also commonly used in fire safety of laminates in printed circuit boards, plastics in electrical and electronic equipment. Due to its large part of world production of BFRs for covering around 60% of the total BFR market and the use of TBBPA is currently not restricted in many countries including America and China, TBBPA is of great concern as a relatively persistent organic pollutant released through manufacturing, recycling, and disposal of various fabrics and materials. Moreover, many studies suggest that TBBPA at environmentally relevant concentrations can induce a variety of adverse health effects including cytotoxicity, immunotoxicity, hepato-toxicity, disruption of thyroid homeostasis, and has potential to disrupt estrogen signaling. The aqueous toxicity of TBBPA has been demonstrated that the acute 48-h LC50 (lethal concentration of 50%) for Daphnia magna was reported to be 0.96 mg/L, and 96-h LC50 for fish ranged from 0.40 to 0.54mg/L. The acute oral toxicity of TBBPA for mammals is low. However, the International Agency for Research on Cancer has recently upgraded this flame retardant to group 2A (probably carcinogenic to humans) which was based on sufficient evidence of carcinogenicity in experimental animals and strong mechanistic evidence in humans. The immobilization of TBBPA from aqueous solution by pinecone-derived biochars was investigated. The surface structures and functional groups of biochars produced at different temperatures were characterized through synchrotron-assisted FTIR analysis. The adsorption isotherms were well described by the Langmuir model. The adsorption capacity of TBBPA varied as pH and TBBPA initial concentration changed. The influences of inorganic fertilizer ions (NH4+, PO43− and NO3− ) on the immobilization of TBBPA by pinecone biochars were revealed through fractional-factorial assisted analysis. The results indicated the main effects include negative effects of PO43− , positive effects of NH4+ and insignificant effects of NO3− ions in immobilization and there are interactions among these ions, pH and biochar properties. Functionality and surface interaction between biochar and TBBPA were investigated under analysis of kinetic models, contact times, surface composition and synchrotron-based FTIR analysis. The results indicated that the interaction between TBBPA on biochar was mainly caused by hydroxyls. Their interactive effects of acid functional groups could be an important role in the adsorption of TBBPA. Moreover, under the high initial concentration, the adsorption process can be stabilized by other oxygen-containing groups. In addition, this study also revealed that π-π interactions could have insignificant impacts on TBBPA adsorption. The results can help understand migration patterns of TBBPA and analyze the immobilization on biochars in the presence of inorganic fertilizer ions. It will have important implications for environmental risk assessment and wastewater treatment.
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Faculty of Graduate Studies and Research, University of Regina