Long-term stability and reusability of molecularly imprinted polymers

Molecularly imprinted materials are man-made mimics of biological receptors. Their polymer network has recognition sites complementary to a substrate in terms of size, shape and chemical functionality. They have diverse applications in various chemical, biomedical and engineering fields such as solid phase extraction, catalysis, drug delivery, pharmaceutical purification, (bio)sensors, water treatment, membrane separations and proteomics. The stability and reusability of molecularly imprinted polymers (IPs) have crucial roles in developing applications that are reliable, economic and sustainable. In the present article the effect of crosslinkers, functional monomers and conditions for template extraction on the long-term stability and reusability of IPs was systematically investigated. Adsorption capacity, selectivity, morphology and thermal decomposition of eleven different l-phenylalanine methyl ester imprinted polymers were studied to reveal performance loss over 100 adsorption-regeneration cycles. Furthermore, crosslinker and functional monomer specific reversible and irreversible decomposition of imprinted polymers as a result of adsorbent regeneration were investigated through adsorption studies, electron microscopy, N2 adsorption and thermogravimetric analysis. A decomposition mechanism was proposed and revealed using NMR spectroscopy. Solutions to avoid or overcome the limitations of the most common crosslinkers, functional monomers and extraction techniques were proposed and experimentally validated. © The Royal Society of Chemistry 2017

Exploring and exploiting the effect of solvent treatment in membrane separations

It is well-known that solvent treatment and preconditioning play an important role in rejection and flux performance of membranes due to solvent-induced swelling and solvent adsorption. Investigations into the effect of solvent treatment are scarce and application specific, and were limited to a few solvents only. This study reveals the trend in solvent treatment based on solvent polarity in a systematic investigation with the aim to harness such effect for intensification of membrane processes. Nine solvents with polarity indices ranging from 0.1 to 5.8 (hexane to acetonitrile) were used as treatment and process solvents on commercial Borsig GMT-oNF-2, Evonik Duramem 300, and emerging tailor-made polybenzimidazole membranes. TGA-GCMS, HS-GC-FID, and NMR techniques were employed to better understand the effect of solvent treatment on the polymer matrix of membranes. In this work, apart from the solvent treatment’s direct effect on the membrane performance, a subsequent indirect effect on the ultimate separation process was observed. Consequently, a pharmaceutical case study employing chlorhexidine disinfectant and antiseptic was used to demonstrate the effect of solvent treatment on the nanofiltration-based purification. It is shown that treatment of polybenzimidazole membranes with acetone resulted in a 25% increase in product recovery at 99% impurity removal. The cost of the process intensification is negligible in terms of solvent consumption, mass intensity, and processing time

Sustainable wastewater treatment and recycle in membrane manufacturing

Tackling the wastewater challenge in polymer membrane manufacturing with a continuous adsorption process.</p