Extent and mechanisms of brominated and chlorinated flame retardant emissions associated with the treatment of waste electronics, furnishings and building materials

Stubbings, William Andrew (2016). Extent and mechanisms of brominated and chlorinated flame retardant emissions associated with the treatment of waste electronics, furnishings and building materials. University of Birmingham. Ph.D.

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Abstract

The work conducted in this thesis examines the potential for emissions of flame retardants (FRs) from a range of treated end-of-life materials during and following disposal. A series of standardised leaching experiments were developed and conducted to study FR leaching from a range of waste flame retarded products, including: textiles, EPS and XPS building insulation foams, cathode-ray tube plastics and polyurethane furniture foams (PUF). The leaching tests were conducted using a range of leaching fluids, with the view of simulating the characteristics of real landfill leachates. A number of different test parameters were examined, such as a variety of dissolved humic matter concentrations, landfill relevant pHs between 5.8 and 8.5, landfill relevant temperatures, the effect of agitation, contact durations and longer term cycles of periodic wetting and draining of waste. It is apparent from these experiments that despite the relatively hydrophobic physicochemical properties of brominated FRs (BFRs), they are able to leach from waste materials at substantial concentrations. Concentrations of ƩPBDEs (polybrominated diphenyl ethers) in the leachate from the leaching experiments in this study ranged from 14,000 – 200,000 ng L-1, while concentrations of ƩHBCDD (hexabromocyclododecane) ranged from 170 ng L-1 – 13,000 ng L-1 in textile leaching experiments and from 13,000 ng L-1 – 4,200,000 ng L-1 in building insulation foam experiments. BFR leaching appears to be a second order process, whereby a period of initially intense dissolution of more labile BFR is followed by a slower stage corresponding to external diffusion of the soluble residue in the material. Tris (chloroisopropyl) phosphate (TCIPP) is more readily soluble in water than the BFRs studied, and leaching of TCIPP from PUF appears to be a first order process. Concentrations of TCIPP in the leachate from the leaching experiments in this study ranged from 13 mg L-1 – 130 mg L-1. In serial batch leaching experiments, >95 % of TCIPP was depleted from the flexible PUF after the sixth batch (168 h total contact). Hence, leaching is potentially a very significant pathway for TCIPP emissions to the environment. A small survey of waste soft furnishings from a variety of UK domestic and office locations was also conducted, to help determine the total FR content entering the UK waste stream as a result of the disposal of soft furnishings. The predominant FR detected was TCIPP. Closed test chamber experiments investigating the effect of temperature on volatilisation of TCIPP from polyurethane foam were conducted. These experiments show volatilisation of TCIPP from PUF to increase exponentially with temperature and to constitute an additional potentially significant pathway for emissions from UK MSW landfills, with TCIPP emissions via volatilisation from landfilled PUF estimated to range between ~200 and ~3,800 tonnes yr-1.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):