Effect of Membrane Properties on Performance of Membrane Distillation for Ammonia Removal

Zongli Xie,Puyam Singh,Paramita Ray,Tuan Duong,S Maurya,Derrick Ng,K Parashuram,Manh Hoang,A V R Reddy

doi:10.5539/jmsr.v1n1p37

Zongli Xie, Puyam Singh + Show 7 more

Open Access

https://doi.org/10.5539/jmsr.v1n1p37

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Abstract

Membrane distillation (MD) has received much attention in recent years as an alternative technology for the removal of volatile compounds from industrial waters. The microporous hydrophobic membrane utilised in MD allows only vapour passing through and the process selectivity is essentially determined by the liquid-vapour equilibrium conditions existing at the liquid-membrane interface. In this study, a series of asymmetrically structured polyvinylidene fluoride (PVDF) hollow fibre membranes were fabricated and tested for the removal of ammonia from simulated industrial wastewater. The asymmetric membranes contain very thin skin layer with macrovoids supported underneath. Hollow fibre MD modules with membrane area of 0.06 m2 have been assembled and tested for dilute aqueous solutions containing ammonia at concentrations <1000 mg/L. The membranes were characterised in terms of porosity, thickness, hydrophobicity, water permeability, surface roughness and zeta potential. Sweep gas MD configuration was employed for all experiments and >90% ammonia removal could be achieved. The results from the MD experiments were compared and the effect of membranes characteristics was discussed.

Highlights

Membrane distillation (MD) is a thermal process driven by the vapor pressure difference of volatile components between the two surfaces of a non-wetted hydrophobic membrane
In our previous work (Xie, et al, 2009), we have demonstrated potential application of sweep gas MD for removing ammonia from industrial wastewater by using commercial PTFE membrane
Membranes 851 and 853 were fabricated from the same dope solution (PVDF 12%, ethylene glycol (EG) 8% and NMP 80%, w/w) by varying extrusion and winding rate while the membrane 861 were fabricated from a different dope solution (PVDF 15 %, PVP 2% and DMF 83%, w/w)

Summary

Introduction

Membrane distillation (MD) is a thermal process driven by the vapor pressure difference of volatile components between the two surfaces of a non-wetted hydrophobic membrane. The hydrophobic nature of the membrane prevents penetration of the aqueous solution into the pores, resulting in a vapour-liquid interface at the pore entrance (Bougeecha, et al, 2002). Sweep gas MD has received increasing attentions in removing volatile compounds from aqueous streams (Qin et al, 1996; Semmens, et al, 1990; Tan, et al, 2006; Zhu et al, 2005). This is especially beneficial for recycling industrial wastewater containing low level of volatiles. Some common polymers which could be used as the MD membrane materials include polypropylene (PP), polytetrafluoro ethylene (PTFE), and polyvinylidene fluoride (PVDF)

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