Membrane Distillation of Saline Water Contaminated with Oil and Surfactants.

Wirginia Tomczak,Marek Gryta

doi:10.3390/membranes11120988

Abstract

Application of the membrane distillation (MD) process for the treatment of high-salinity solutions contaminated with oil and surfactants represents an interesting area of research. Therefore, the aim of this study is to investigate the effect of low-concentration surfactants in oil-contaminated high-salinity solutions on the MD process efficiency. For this purpose, hydrophobic capillary polypropylene (PP) membranes were tested during the long-term MD studies. Baltic Sea water and concentrated NaCl solutions were used as a feed. The feed water was contaminated with oil collected from bilge water and sodium dodecyl sulphate (SDS). It has been demonstrated that PP membranes were non-wetted during the separation of pure NaCl solutions over 960 h of the module exploitation. The presence of oil (100–150 mg/L) in concentrated NaCl solutions caused the adsorption of oil on the membranes surface and a decrease in the permeate flux of 30%. In turn, the presence of SDS (1.5–2.5 mg/L) in the oil-contaminated high-salinity solutions slightly accelerated the phenomenon of membrane wetting. The partial pores’ wetting accelerated the internal scaling and affected degradation of the membrane’s structure. Undoubtedly, the results obtained in the present study may have important implications for understanding the effect of low-concentration SDS on MD process efficiency.

Highlights

Membrane distillation (MD) is a separation process, where water vapor molecules and/or volatile compounds flow from a hot aqueous solution through pores of a hydrophobic membrane due to the difference in the partial pressure across a membrane, as a result of the temperature gradient [1]
It has be shown that the MD process can be successfully used for treating high‐salinity solution it has been shown that MD can be successfully applied for desalination g/L, salt retention of 99% was noted
It was demonstrated that increasing the membrane’s wall thickness from 0.4 to 1.5 mm resulted in a twofold reduction in the MD process performance and greater resistance to degradation

Summary

Introduction

Membrane distillation (MD) is a separation process, where water vapor molecules and/or volatile compounds flow from a hot aqueous solution through pores of a hydrophobic membrane due to the difference in the partial pressure across a membrane, as a result of the temperature gradient [1]. MD has gained a growing interest in research and commercial development, mainly in the field of desalination and wastewater treatment. This is because it offers technological advantages, including:. The MD process was invented in 1963 [48] and has been carried out using commercial membranes around 2006 [49], implementations at the large-scale are still limited. This is related to the fact that state-of-the-art MD, similar to other membrane separation processes, still has limitations. Contributions of numerous investigations have highlighted issues related to the MD process, such as pore wetting and membrane scaling that lead to significant reductions in the cost-effectiveness of the process [50]

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