Cranfield Water Science Institute

Cranfield, United Kingdom

Cranfield Water Science Institute

Cranfield, United Kingdom
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Heile S.,Cranfield Water Science Institute | Heile S.,Osnabruck University of Applied Sciences | Rosenberger S.,Osnabruck University of Applied Sciences | Parker A.,Cranfield Water Science Institute | And 2 more authors.
Journal of Membrane Science | Year: 2014

A hollow fibre membrane contactor (HFMC) comprised of nonporous symmetric ultrathin wall polydimethylsiloxane (PDMS) fibres has been studied for biogas upgrading to establish if the ultrathin wall can enable low resistance to mass transfer coupled with enhanced selectivity for carbon dioxide (CO2). For a feed gas CO2 mole fraction of 80%, a CO2 flux of 1.25×10-4molm-2s-1 was recorded which was higher than expected and is ostensibly due to the thin wall and the absence of a support layer which can limit gas transfer due to concentration polarisation. Maximum CO2 flux was recorded at the highest liquid velocity tested due to a reduction in the thickness of the liquid phase boundary layer. Resistance in series analysis demonstrated that by limiting liquid phase resistance, mass transfer was controlled by the PDMS membrane and selectivity toward CO2 was analogous to the ideal selectivity imparted by PDMS. In comparison, mass transfer was liquid phase controlled for a microporous HFMC that comprised of fibres with equivalent wall thickness. Whilst PDMS presents a higher theoretical selectivity when compared to the gas filled pore of a microporous fibre, higher selectivity was provided by the microporous fibre due to the solvents selectivity, which established that selectivity is dependent upon the controlling phase boundary. Though higher CO2 fluxes were achieved with microporous fibres, ultrathin PDMS fibres are potentially beneficial for gases with a low CO2 mole fraction due to their greater resistance to wetting. However, at higher CO2 mole fraction, PDMS HFMC are only viable by increasing CO2 flux through overpressure or reduction in wall thickness, though the feasibility is impingent upon validating the fibres mechanical integrity for both conditions. © 2013 Elsevier B.V.


Pratt C.,Landcare Research | Parsons S.A.,Cranfield Water Science Institute | Soares A.,Cranfield Water Science Institute | Martin B.D.,Cranfield Water Science Institute
Current Opinion in Biotechnology | Year: 2012

Biologically and chemically mediated adsorption and precipitation processes offer a range of approaches for removing phosphorus (P) from agricultural, domestic and industrial effluents. Technologies implemented at full-scale include filtration by adsorbent media, such as steel slag, and recovery of phosphorus as struvite, which has been successfully commercialised as a fertiliser. Other promising technologies under investigation include P removal by polymers and nanomaterials as well as struvite formation by bacteria. There is a need to focus future research on improving the efficiency of P removal by adsorption and precipitation. This can be achieved by techniques such as regenerating filters, polymers and nanomaterials for renewed P removal. Research is also needed to optimise the fertiliser potential of struvite precipitates. © 2012 Elsevier Ltd.

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