Selectivity and characteristics of direct contact membrane distillation type experiment. II. Membrane treatment and selectivity increase

Morphology and Thermodynamic Study of a Novel Composite Membrane from Waste Polystyrene/Slag: Experimental Investigation

The development of the membrane surface and cross-sectional morphology is pivotal in influencing the effectiveness of membrane separation. In this study, evaluating the separation rates between the solvent and nonsolvent in the casting solution and the related thermodynamic alteration analysis were illustrated. Additionally, the rheological variations were determined by measuring the viscosity of the resulting dope solutions, providing an initial estimation of the phase separation kinetics. Asymmetric polystyrene (PS)/slag composite membrane, incorporating slag waste as an inorganic additive, was developed. Dimethylformamide (DMF) was utilized as the solvent, and sodium dodecyl sulfate (SDS) was employed as an anionic surfactant to facilitate the casting process. A tertiary system diagram approach involving waste PS, DMF, and water introducing slag as an inorganic additive and SDS as a surfactant was attained to promote the separation of the solvent and nonsolvent in the casting solution. These novel composite mixtures exhibited increased thermodynamic instability within the coagulation bath, facilitating the rapid separation of solid membranes from the dope solutions and forming composite membranes with significantly increased porosity (exceeding a 20% increase) compared to that of plain waste materials. The composite membrane characteristics were assessed with the widely used poly(vinylidene difluoride) (PVDF) membrane, showing comparative features and performance when tested on a membrane distillation (MD) cell; it gave a flux of 1 kg/m2·h. These promising characteristics positioned this novel PS/slag composite membrane as a candidate for various water-related applications.

Interplay of the Factors Affecting Water Flux and Salt Rejection in Membrane Distillation: A State-of-the-Art Critical Review

High water flux and elevated rejection of salts and contaminants are two primary goals for membrane distillation (MD). It is imperative to study the factors affecting water flux and solute transport in MD, the fundamental mechanisms, and practical applications to improve system performance. In this review, we analyzed in-depth the effects of membrane characteristics (e.g., membrane pore size and distribution, porosity, tortuosity, membrane thickness, hydrophobicity, and liquid entry pressure), feed solution composition (e.g., salts, non-volatile and volatile organics, surfactants such as non-ionic and ionic types, trace organic compounds, natural organic matter, and viscosity), and operating conditions (e.g., temperature, flow velocity, and membrane degradation during long-term operation). Intrinsic interactions between the feed solution and the membrane due to hydrophobic interaction and/or electro-interaction (electro-repulsion and adsorption on membrane surface) were also discussed. The interplay among the factors was developed to qualitatively predict water flux and salt rejection considering feed solution, membrane properties, and operating conditions. This review provides a structured understanding of the intrinsic mechanisms of the factors affecting mass transport, heat transfer, and salt rejection in MD and the intra-relationship between these factors from a systematic perspective.

Membranes and theoretical modeling of membrane distillation: a review

Membrane distillation (MD) is one of the non-isothermal membrane separation processes used in various applications such desalination, environmental/waste cleanup, food, etc. It is known since 1963 and is still being developed at laboratory stage for different purposes and not fully implemented in industry. An abrupt increase in the number of papers on MD membrane engineering (i.e. design, fabrication and testing in MD) is seen since only 6 years ago. The present paper offers a comprehensive MD state-of-the-art review covering a wide range of commercial membranes, MD membrane engineering, their MD performance, transport mechanisms, experimental and theoretical modeling of different MD configurations as well as recent developments in MD. Improved MD membranes with specific morphology, micro- and nano-structures are highly demanded. Membranes with different pore sizes, porosities, thicknesses and materials as well as novel structures are required in order to carry out systematic MD studies for better understanding mass transport in different MD configurations, thereby improving the MD performance and looking for MD industrialization.

Fuel ethanol production: process design trends and integration opportunities

Current fuel ethanol research and development deals with process engineering trends for improving biotechnological production of ethanol. In this work, the key role that process design plays during the development of cost-effective technologies is recognized through the analysis of major trends in process synthesis, modeling, simulation and optimization related to ethanol production. Main directions in techno-economical evaluation of fuel ethanol processes are described as well as some prospecting configurations. The most promising alternatives for compensating ethanol production costs by the generation of valuable co-products are analyzed. Opportunities for integration of fuel ethanol production processes and their implications are underlined. Main ways of process intensification through reaction-reaction, reaction-separation and separation-separation processes are analyzed in the case of bioethanol production. Some examples of energy integration during ethanol production are also highlighted. Finally, some concluding considerations on current and future research tendencies in fuel ethanol production regarding process design and integration are presented.