Membrane Crystallization for Process Intensification and Control:A Review

Crystallization is a fundamental separation technology used for the production of particulate solids.Accurate nucleation and growth process control are vitally important but difficult.A novel controlling technology that can simultaneously intensify the overall crystallization process remains a significant challenge.Membrane crystallization(MCr),which has progressed significantly in recent years,is a hybrid technology platform with great potential to address this goal.This review illustrates the basic concepts of MCr and its promising applications for crystallization control and process intensification,including a state-of-the-art review of key MCr-utilized membrane materials,process control mechanisms,and optimization strategies based on diverse hybrid membranes and crystallization processes.Finally,efforts to promote MCr technology to industrial use,unexplored issues,and open questions to be addressed are outlined.

Synthesis and Separation Performance of Y-type Zeolite Membranes by Pre-Seeding Using Electrophoresis Deposition Method

Y-type zeolite membranes were synthesized by a two-step approach in which a particle seed layer was prepared by electrophoresis deposition(EPD) at first, followed by densification through secondary growth. The pre-seeding adopted the directing agent for Y-type zeolite synthesis serving as seeds. The effects of aging time of the directing agent, electrophoresis voltage and electrophoresis deposition time on seed layers quality as well as the quality of zeolite membranes were investigated. The results indicated that the zeolite seeds derived from the directing agent could be evenly deposited on substrate under certain EPD conditions. The XRD patterns of the seeded substrates after the secondary growth showed that the pure as-synthesized Y-type zeolite membranes had successfully grown on the substrates. The SEM images indicated that the substrate was covered by the highly intergrown zeolite crystals when the seeding solution employed the directing agent with an aging time of 2 days. The separation performance of zeolite membrane was evaluated using a CO_2/N2 mixture(with a mole ratio of 1:1) at different temperatures. Furthermore, the pervaporation measurements were carried out for the dehydration of isopropanol aqueous solutions with different mass fractions. The as-synthesized Y-type zeolite membranes exhibited a relatively high selectivity of water from isopropanol and sustainable permeation flux.

Progress in membrane distillation crystallization： Process models, crystallization control and innovative applications

Membrane distillation crystallization （MDC） is a promising hybrid separation process that has been applied to seawater desalination, brine treatment and wastewater recovery. In recent years, great progress has been made in MDC technologies including the promotion of nucleation and better control of crystallization and crystal size distribution. These advances are useful for the accurate control of the degree of supersaturation and for the control of the nucleation kinetic processes. This review focuses on the development of MDC process models and on crystallization control strategies. In addition, the most important innovative applications of MDC in the last five years in crystal engineering and pharmaceutical manufac- turing are summarized.

High-efficient crystal particle manufacture by microscale process intensification technology

High-end crystal manufacture has drawn a permanent concern on the high-efficient manufacture of crystal particles,especially in fine chemical,pharmaceutical,electronics,biological and relative engineering fields.In recent years,a series of microscale process intensification(MPI)technologies have been widely used in crystal particles preparation via addressing the control of nucleation and growth process.Herein,we review the research progresses of microscale process intensification technology from three aspects,microfluidics devices,microscale force field technology and membrane-based microchannels and interface transfer process.Firstly,the principle of microfluidic and relative microscale device on improving micro-mixing and mass transfer are briefly described.The advantage of microfluidic in continuous nano particle preparation is outlined.Microscale external force field(ultrasonic,high-gravity,electric and magnetic fields)is then introduced as another novel approach for ultrafine nanoparticles and continuous drug crystallization process.Further,in view of the micro-scale intensified mass transfer and microscale interfacial force field established on membrane technology,the basic mechanism of membrane crystallization(microscale 2D supersaturation degree control,auto seed detachment,microporous membrane dispersion,etc.)is reviewed.The process coupling and design strategy aiming for enhancing the manufacture capacity is also illustrated.Finally,the developing tendency and key challenges of high-efficient crystal particle preparation technology via microscale processes are overviewed.

Activation in the initial stage of oxygen permeation in SrCo_(0.9)Ta_(0.1)O_(3-δ)

Mixed conducting perovskite oxide SrCo_（0.9）Ta_（0.1）O_（3-δ）（SCT） is synthesized by solid-state reaction method.The activation in the initial stage of oxygen permeation through the SCT membrane is investigated.The results show that the activation in the initial stage of oxygen permeation has activate-memory,the first activation can only help to reduce active time of the next cycles,but it is helpless to increase the final oxygen permeation flux.XRD characterization shows that the imperfect perovskite phase structure is gradually improved and the crystal lattice has made some self-adjustment under the permeation conditions,therefore,the oxygen permeation flux of SCT disk membrane increases gradually and till it reaches a steady state.