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The long-term studies of osmotic membrane distillation.

ABSTRACT: The results of osmotic membrane distillation carried out for 2.5 years were presented in this work. The influence of the process conditions, such as temperature and brine concentration on the permeate flux, was investigated. The saturated NaCl solutions and distilled water were used as a stripping solution and feed, respectively. A continuous regeneration of stripping solution was conducted using a method of natural evaporation from the surface of Bia?ecki rings to the air surrounding the installation. The possibilities of application of Accurel PP S6/2 hydrophobic polypropylene membranes were tested. It was studied whether a saturation stripping solution does not cause scaling and wettability of membranes. It was found that most of the pores in the used membranes were non-wetted, and the salt retention over 99% was maintained during a study period. However, the obtained permeate flux was decreased by 10-20%. The SEM examinations revealed that it was caused by amorphous deposit, which was formed on the membrane surface on the brine side. The SEM-EDS analysis demonstrated that the deposit composition mainly included Si and O.

SUBMITTER: Gryta M

PROVIDER: S-EPMC5760615 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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The long-term studies of osmotic membrane distillation.

Gryta Marek M

Chemicke zvesti 20170803 1

The results of osmotic membrane distillation carried out for 2.5 years were presented in this work. The influence of the process conditions, such as temperature and brine concentration on the permeate flux, was investigated. The saturated NaCl solutions and distilled water were used as a stripping solution and feed, respectively. A continuous regeneration of stripping solution was conducted using a method of natural evaporation from the surface of Białecki rings to the air surrounding the instal ...[more]

PMID: 29367800

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Project description:Membrane distillation (MD) has shown promise for concentrating a wide variety of brines, but the knowledge is limited on how different brines impact salt scaling, flux decline, and subsequent wetting. Furthermore, past studies have lacked critical details and analysis to enable a physical understanding, including the length of experiments, the inclusion of salt kinetics, impact of antiscalants, and variability between feed-water types. To address this gap, we examined the system performance, water recovery, scale formation, and saturation index of a lab-scale vacuum membrane distillation (VMD) in long-running test runs approaching 200 h. The tests provided a comparison of a variety of relevant feed solutions, including a synthetic seawater reverse osmosis brine with a salinity of 8.0 g/L, tap water, and NaCl, and included an antiscalant. Saturation modeling indicated that calcite and aragonite were the main foulants contributing to permeate flux reduction. The longer operation times than typical studies revealed several insights. First, scaling could reduce permeate flux dramatically, seen here as 49% for the synthetic brine, when reaching a high recovery ratio of 91%. Second, salt crystallization on the membrane surface could have a long-delayed but subsequently significant impact, as the permeate flux experienced a precipitous decline only after 72 h of continuous operation. Several scaling-resistant impacts were observed as well. Although use of an antiscalant did not reduce the decrease in flux, it extended membrane operational time before surface foulants caused membrane wetting. Additionally, numerous calcium, magnesium, and carbonate salts, as well as silica, reached very high saturation indices (>1). Despite this, scaling without wetting was often observed, and scaling was consistently reversible and easily washed. Under heavy scaling conditions, many areas lacked deposits, which enabled continued operation; existing MD performance models lack this effect by assuming uniform layers. This work implies that longer times are needed for MD fouling experiments, and provides further scaling-resistant evidence for MD.

Dataset Information

The long-term studies of osmotic membrane distillation.

Publications

The long-term studies of osmotic membrane distillation.

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