Huu Doan

A Review on Breathing Behaviors of Metal-Organic-Frameworks (MOFs) for Gas Adsorption

Metal-organic frameworks (MOFs) are a new class of microporous materials that possess framework flexibility, large surface areas, “tailor-made” framework functionalities, and tunable pore sizes. These features empower MOFs superior performances and broader application spectra than those of zeolites and phosphine-based molecular sieves. In parallel with designing new structures and new chemistry of MOFs, the observation of unique breathing behaviors upon adsorption of gases or solvents stimulates their potential applications as host materials in gas storage for renewable energy. This has attracted intense research energy to understand the causes at the atomic level, using in situ X-ray diffraction, calorimetry, Fourier transform infrared spectroscopy, and molecular dynamics simulations. This article is developed in the following order: first to introduce the definition of MOFs and the observation of their framework flexibility. Second, synthesis routes of MOFs are summarized with the emphasis on the hydrothermal synthesis, owing to the environmental-benign and economically availability of water. Third, MOFs exhibiting breathing behaviors are summarized, followed by rationales from thermodynamic viewpoint. Subsequently, effects of various functionalities on breathing behaviors are appraised, including using post-synthetic modification routes. Finally, possible framework spatial requirements of MOFs for yielding breathing behaviors are highlighted as the design strategies for new syntheses.

A facile method to tune zeolite L crystals with low aspect ratio

We demonstrate an alternative route to tune the morphology of zeolite L crystals using C(2)H(5)OH as the co-solvent in the synthesis gel. A low aspect ratio (0.2 to 0.4) of zeolite L crystals was obtained at lower synthesis temperature (150 °C) and shorter synthesis duration (3 days).

Fouling in Membrane Filtration and Remediation Methods

The growth of the membrane technologies has fell far behind the initial anticipation, one of the major obstacles, which hinders more widespread of its application, is that the filtration performance inevitably decreases with filtration time. This phenomenon is commonly termed as membrane fouling, which refers to the blockage of membrane pores during filtration by the combination of sieving and adsorption of particulates and compounds onto the membrane surface or within the membrane pores. Pore blockage reduces the permeate production rate and increases the complexity of the membrane filtration operation. This is the most challenging issue for further membrane development and applications.

Prediction of power consumption and performance in ultrafiltration of simulated latex effluent using non-uniform pore sized membranes

Tha aim of the present study was to develop a series of numerical models for an accurate prediction of the power consumption in ultrafiltration of simulated latex effluent. The developed power consumption model incorporated fouling attachment, as well as chemical and physical factors in membrane fouling, in order to ensure accurate prediction and scale-up. This model was applied to heterogeneous membranes with non-uniform pore sizes at a given operating conditions and mem- brane surface charges. Polysulfone flat membrane, with a membrane molecular weight cutoff (MWCO) of 60,000 dalton, at different surface charges was used under a constant flow rate and cross-flow mode. In addition, the developed models were examined using various membranes at a variety of surface charges so as to test the overall reliability and accuracy of these models. The power consumption predicted by the models corresponded to the calculated values from the experimental data for various hydrophilic and hydrophobic membranes with an error margin of 6.0% up to 19.1%.

The influence of aggregation of latex particles on membrane fouling attachments & ultrafiltration performance in ultrafiltration of latex contaminated water and wastewater.

The goal of the present study was to investigate the influence of latex particle aggregation on membrane fouling attachments and the ultrafiltration performance of simulated latex effluent using Cetyltrimethyl Ammonium Bromide (CTAB) as a cationic surfactant. Hydrophilic polysulfone and ultrafilic flat heterogeneous membranes, with molecular weight cut off (MWCO) of 60,000 and 100,000, respectively, as well as hydrophobic polyvinylidene difluoride with MWCO of 100,000, were used under a constant flow rate and cross-flow mode in ultrafiltration of latex solution. In addition, a polycarbonate flat membrane with uniform pore size of 0.05μm was likewise used during the experiment. The effects of CTAB on the latex particle size distribution were investigated at various concentrations, different treatment times, and diverse agitation duration times. The effects of CTAB on the zeta potential of membrane surfaces and latex particles were also investigated. The data obtained indicate that the particle size distribution of treated latex effluent experienced significant shifts in the peaks toward a larger size range caused by the aggregation of particles. As a result, the mass of fouling contributing to pore blocking and the irreversible fouling were noticeably reduced. The optimum results occurred in the instance when CTAB was added at the critical micelle concentration of 0.36g/L, for the duration of 10min and with minimal agitation. Notably, a higher stirring rate had an overall negative effect on the membrane fouling minimization.

The effect of contaminated particle sphericity and size on membrane fouling in cross flow ultrafiltration

ABSTRACT The goal of the current research was to critically examine the role of the shape and the size of contaminated particles for an accurate prediction of membrane fouling phenomenon. Polycarbonate flat membranes (PC) with uniform pore sizes of 0.05 and 0.1 µm, in addition to Polysulfone membranes (PS) with molecular weight cut off (MWCO) of 60,000 kDa were used under a constant feed flow rate and a cross-flow mode in ultrafiltration of a latex paint solution featuring a wide range of particle size distribution. The current mathematical model was developed to illustrate the effect of irregularity and polydispersity of latex particles on the mass of fouling and irreversible fouling on membranes. The experimental results established that the sphericity of contaminated particles had a critical effect on the membrane fouling and prediction of transmembrane pressure and total mass of fouling using the homogenous pore size membranes. The Cetyltrimethyl Ammonium Bromide (CTAB) was implemented as a cationic surfactant so as to facilitate the aggregation of latex particles. The results obtained indicated that the particle size had a significant influence on fouling potential at different aggregation levels.

Aquaporin-Based Biomimetic and Bioinspired Membranes for New Frontiers in Sustainable Water Treatment Technology: Approaches and Challenges

Biomimetic and bioinspired membranes are the efficient membrane technology when it comes to multiple usage scenarios, including next generations of biomaterials within the commercial separation applications, as well as, water and wastewater treatment technologies. In recent years, aquaporin biomimetic membranes for water separation have raised considerable interest. These membranes have displayed distinguished properties and outstanding performances, as diverse interactions, varying selective transport mechanisms, superior stability, maximum resistance to membrane fouling, and distinct adaptability. The biomimetic membranes have made significant contributions when it comes to water stress, environmental threats and energy. It has the potential to produce clean water more efficiently than reverse osmosis membranes (RO), while saving up to 80% of the energy used for desalination processes. More than half of the 15000 desalination plants around the world utilize RO technologies, and the implementation of biomimetic membranes on a large scale could save hundreds of millions of dollars in energy cost annually (potential savings of

Mass Transfer Mechanisms and Transport Resistances in Membrane Separation Process

1.45 million/year for 100 ML/day desalination plant). This paper discusses the interplay of the main components of aquaporin biomimetic membranes: aquaporin proteins, block copolymers for aquaporin proteins reconstitution, and polymer-based supporting structures. We focus specifically on the challenges and review recent developments on the interplay between aquaporin proteins and block copolymers. The recent efforts in embedding reconstituted aquaporin proteins in membrane designs that are based on conventional thin film interfacial polymerization techniques are evaluated. In addition, emerging challenges and opportunities for biomimetic membranes are studied from the perspective of current and future applications.

Batch and continuous fixed-bed column biosorption of Cd2+ and Cu2+

One of the major obstacles preventing a more widespread application of membrane technology is the fact that the filtration performance inevitably decreases with filtration time. The understanding of causes of flux decline and the ability of predicting the flux performance is crucial for more extensive membrane applications. Therefore, this review focused on the analysis of the interrelated dynamics of membrane fouling and mass transport in the filtration/separation process. Furthermore, findings from various studies undertaken by many researchers to investigate various aspects of these complex phenomena, were analyzed and discussed. These previous studies form the foundation essential for the alleviation of adverse effect of membrane fouling and emphasize the fact that the development of a complex overlapping approach is needed. Investigations of the mechanisms of mass transfer in low and high pressure membranes, analyses of diffusion mechanisms in the membrane pore together with identifications of transport resistances resulting from membrane fouling will allow for a comprehensive understanding and in-depth knowledge of the fouling phenom‐ enon and applicable mass transfer mechanisms.