Membrane-Based Technologies for the Up-Concentration of Municipal Wastewater: A Review of Pretreatment Intensification Sep. Purif. Rev. (IF 4.714) Pub Date : 2018-06-06 Thiago A. Nascimento; Fernando Fdz-Polanco; Mar Peña
Municipal wastewater has a high content of recoverable energy, distributed within particulate and soluble organic matters. It is estimated that the anaerobic treatment of that content and the recovery of biogas energy could supply at least enough power to render a wastewater treatment plant electrically self-sufficient. Therefore, an intensification of wastewater pretreatment could separate and concentrate the organic matter in order to improve the anaerobic stabilization of both the solids and the water streams. In light of this, membrane-based processes have been considered as novel technologies in order to recover carbon from municipal wastewater. In this work, direct membrane filtration, forward osmosis and dynamic membrane have been reviewed as possible membrane-based technologies for the up-concentration of wastewater. A literature overview has been performed in order to elucidate the main operational parameters and to compare the advantages and downsides of every pretreatment reported up until now.
Bio-Inspired Supramolecular Membranes: A Pathway to Separation and Purification of Emerging Pollutants Sep. Purif. Rev. (IF 4.714) Pub Date : 2018-08-13 Faran Nabeel; Tahir Rasheed; Muhammad Bilal; Chuanlong Li; Chunyang Yu; Hafiz M. N. Iqbal
Supramolecular membranes based separation and/or purification is an emerging technology with tunable capabilities for several applications. The proposed applications include water desalination, wastewater treatment, and separation and purification of emerging pollutants alleviating the global issue of freshwater scarcity. Advanced water purification and separation methods are required on priority to meet the demand of a growing world population. Owing to their unique physiochemical and structural properties in combination with reversible and highly selective nature, supramolecular materials are gaining research interests to engineer multifunctional separation membranes. These materials give excellent properties to the separating membranes when used with commercial crosslinked polyamide network membranes and are cost-effective from the operational viewpoint. Herein, an effort has been made to review several types of supramolecular biomimetic membranes that include pressure-driven membranes, bio-inspired supramolecular water channels, aquaporin, advanced planar aquaporin, vesicular aquaporin-based biomimetic membranes, and catecholamine-based supramolecular membranes. Several nanopore-sized materials are being developed based on aquaporin water channels, and mussel inspired catecholamines for high-performance separation membranes. This review also evaluates these technologies identifying recent progresses and commercial aspects in nanofiltration and reverse osmosis applications.
Membrane-based Separation in Flow Analysis for Environmental and Food Applications Sep. Purif. Rev. (IF 4.714) Pub Date : 2018-08-20 Inês C. Santos; Raquel B. R. Mesquita; António O. S. S. Rangel
Membrane-based separation techniques have been used as an efficient process for analyte separation or enrichment and matrix removal. By coupling these techniques to flow-based analysis, sample preparation and analyte detection can be automated and miniaturized. Different membrane separation techniques are available but the most used in flow analysis are gas diffusion, dialysis, supported liquid membranes and polymer inclusion membranes. The current state of the art of membrane-based separations hyphenated with flow techniques is presented along with a discussion of the applications to environmental and food analysis. Moreover, a brief description of gas diffusion, dialysis and membrane extraction techniques is also included.
ASTM Standard Modified Fouling Index for Seawater Reverse Osmosis Desalination Process: Status, Limitations, and Perspectives Sep. Purif. Rev. (IF 4.714) Pub Date : 2018-09-19 Yongxun Jin; Hyunkyung Lee; Chanhyuk Park; Seungkwan Hong
Fouling indices have been extensively investigated in membrane applications, for evaluating the feed-water fouling potential and providing guidelines for the pretreatment process. For the past few decades, the silt density index (SDI) has been adopted as the most mature fouling index in many seawater reverse osmosis desalination plants. Recently, a modified fouling index (MFI) has gained attention since it compensates for the defects of the SDI. Its publication by ASTM Standard promoted more settlements in practical applications. To gain insight into the use of a membrane-fouling index, this paper reviewed SDI and MFI applications in laboratory-, pilot-, and plant-scale verifications, under conditions likely to be encountered in seawater desalination. The main focus was on the historical development of the fouling indices from theoretical basis to full-scale applications and the identification of future opportunities to expand their reliability in real applications. In particular, the practical implications associated with plant operation were documented to support an in-depth understanding of the MFI values.
Boron Removal from Silicon Using Secondary Refining Techniques by Metallurgical Method Sep. Purif. Rev. (IF 4.714) Pub Date : 2018-10-01 Jijun Wu; Ding Yang; Min Xu; Wenhui Ma; Qiang Zhou; Zhenfei Xia; Yun Lei; Kuixian Wei; Shaoyuan Li; Zhenjie Chen; Keqiang Xie
Impurity removal, the purification process from metallurgical grade silicon (MG-Si) required to obtain solar grade silicon (SoG-Si), is crucial to the preparation of silicon-based solar cells. Some processes for boron removal by metallurgical method were reviewed. Secondary refining techniques, including gas blowing, slag treatment, plasma refining, solvent refining and other refining silicon techniques were summarized. The effects of gas species and slag systems on boron removal efficiency were emphatically discussed. Experimental and theoretical investigations show that a united technique of combining water vapor and oxygen gases blowing with slag treatment containing chloride or fluoride has achieved an amazing improvement for boron removal from molten silicon. Plasma refining and solvent refining also display high efficiency but acid leaching treatments, vacuum volatilization, electron beam and directional solidifications are hardly effective to boron removal. As for the potential industrial application of this united technique, the authors propose that some experimental and theoretical studies in dynamics should be further explored.
Natural Surfactants and Their Applications for Heavy Oil Removal in Industry Sep. Purif. Rev. (IF 4.714) Pub Date : 2018-05-22 Nathalia Maria P. Rocha e Silva, Hugo M. Meira, Fabíola Carolina G. Almeida, Rita de Cássia F. Soares da Silva, Darne G. Almeida, Juliana M. Luna, Raquel D. Rufino, Valdemir A. Santos, Leonie A. Sarubbo
The cleaning of machinery, petroleum storage tanks and equipment leads to the accumulation of petroleum products in the environment. The removal of grease adhered to motors is a specific challenge. Cleaning processes require direct application of surfactants or solvents, which most often generate further environmental problems due to the accumulation of these toxic substances. The majority of available surfactants are synthesized from petroleum derivatives. However, environmental laws have motivated the development of natural surfactants as an alternative to existing products. Biosurfactants can be obtained from microorganisms and plants. Biodegradable detergents can also be obtained through chemical synthesis. This review presents different alternatives for obtaining biodetergents as well as their industrial applications for the removal of heavy oils and the reduction of cleaning and labor costs in industries.
Microfiber Nonwovens as Potential Membranes Sep. Purif. Rev. (IF 4.714) Pub Date : 2018-05-31 Yasar Kiyak, Benoît Mazé, Behnam Pourdeyhimi
This article provides an overview of the membrane bioreactor technology where nonwovens can be applied as an alternative medium for separation. The main objective is to identify the nonwoven characteristics leading to higher removal efficiency, higher flux, and lower fouling behavior. The general limitations associated with common nonwoven separation media are related to the large pore and wide pore size distributions. Consequently, due to their large pore network, nonwovens often behave as a depth filter structure. Common nonwovens having large fibers cannot replace microfiltration membranes yet. Further refinements of these structures are necessary for developing a suitable replacement.
Economic Framework of Membrane Technologies for Natural Gas Applications Sep. Purif. Rev. (IF 4.714) Pub Date : 2018-10-25 V. Martin-Gil, M.Z. Ahmad, R. Castro-Muñoz, V. Fila
Natural gas is one of the most highly used resources, not only as a fuel but also as a raw material for many industrial processes. In addition, it is an environmental friendly fuel due to its lower greenhouse gas emission than that of coal or oil. However, it is a nonrenewable energy source and the quality of the available resources is expected to deplete continuously. In this scenario, membrane technologies can play an important role in the purification of the reduced and contaminated resources, competing with the current technologies owing to their simpler adaptability to different feed compositions, lower energy consumption and investment costs. In this review, the current state of the natural gas sources, including nonconventional resources (tight/shale gas and biogas), is explored, along with the current market status of the conventional natural gas. A comparison between the conventional purification technologies and membrane processes is provided, together with the currently available commercial membranes as well as new materials. Furthermore, the latest materials in research stage are reviewed, pointing out their limitations to the current membranes technologies. Finally, future research trends to overcome the current membrane technology limitations are proposed, and the conclusions are addressed.
Separation Technologies for Salty Wastewater Reduction in the Dairy Industry Sep. Purif. Rev. (IF 4.714) Pub Date : 2018-07-23 G. Q. Chen, S. L. Gras, S. E. Kentish
The wastewater discharged by cheese manufacturing processes is highly saline. This waste is generated from whey demineralization, chromatography and clean-in-place processes. Salty effluent can be diluted with other effluents and discharged as trade waste but the high salinity can trigger penalties imposed by local water authorities. Alternatively, such waste can be sent to evaporation ponds, but in some areas in Australia, environmental impacts regarding land degradation, odor and dust have prevented further pond construction. Similar concentrate and brine management issues are emerging in the seawater desalination and mining industries. This paper reviews a range of commercial and emerging separation technologies that may be suitable to both reduce the costs of salty wastewater treatment and to improve the recoveries of dairy and salt-based products. These technologies have been commercialized or applied at a laboratory scale to the fields of desalination and brine concentration. Each technology is discussed in terms of its principle of operation and suitability for treating high-salinity dairy wastewater. The potential energy requirement and processing cost of each technology is identified with respect to feed water salinity, to provide additional insights into the energy and cost efficiencies of these technologies.