Impact of synthesized amino alcohol plasticizer on the morphology and hydrophilicity of polysulfone ultrafiltration membrane

Lignin particles as green pore-forming agents for the fabrication of microporous polysulfone membranes

Templating polymeric membranes with micro-nano-scaled solid materials is an effective method to simultaneously improve the water flux and retention ratio. However, the fabrication of a green, recyclable, and size-controlled template material remains a challenge. Here, a new green pore-forming agent, lignin particles (LP), was developed to prepare porous polysulfone (PSF) membranes via the phase inversion technique. A series of LP have uniform sizes from ~200 nm to ~1800 nm. The performances of the templated PSF membranes cast at different sizes and contents of LP were examined for their surface and crosssection morphologies. The LP-templated PSF membranes displayed a remarkable enhancement in flux, porosity, and moisture content. Particularly, the PSF membranes cast with LP from ~200 to 1800 nm broke the traditional trade-off to a certain degree, which possessed stable retentions of bovine serum albumin (> 85 %) and significantly improved water flux (174.275 to 254.775 L m^-2 h^-1). In addition, the LP pore-forming agent is low-cost and environmentally friendly as it was prepared from industrial by-products and can be easily recycled. Overall, this study shows that lignin particles are green pore-forming agents that can be used for the fabrication of porous polymeric membranes with improved performance for water treatment.

Enhancement of antifouling properties, metal ions and protein separation of poly(ether-ether-sulfone) ultrafiltration membranes by incorporation of poly ethylene glycol and n-ZnO

Composite polymeric membranes with enhanced anti-fouling properties, antimicrobial activities and flux were produced via the phase inversion technique using poly (ether-ether-sulfone) (PEES)/polyethylene glycol (PEG) and n-ZnO. SEM and ATR-FTIR spectroscopy were used to study the morphological and chemical properties of the resulting ultrafiltration membranes. PEG and n-ZnO concentration has an effect on membrane morphologies, ultrafiltration performance, thermal characteristics, metal ion separation studies, surface hydrophilicity and anti-fouling capabilities. The permeate flux increased when the PEG concentration was raised. This results revealed that adding PEG and n-ZnO to membranes increased their surface hydrophilicity and anti-fouling properties. The inclusion of 1.5 wt % n-ZnO and 5 wt % PEG to the pristine PEES membrane resulted in a higher flux of 233.76 L m^-2 h^-1, 70.09 % of water content, 47.46° of contact angle, the porosity of 30.20 %, and hydraulic resistance of 0.22 kPa/Lm^-2h^-1. Anti-fouling properties of the fabricated membrane were assessed using a model foulant BSA, which revealed a high flux recovery ratio value. As a result, the PEG and n-ZnO incorporated membrane is more hydrophilic than the virgin membrane. In addition, the prepared PEES/PEG/n-ZnO membrane showed a significant increase in metal ions and protein rejection. Furthermore, an antibacterial test of the membrane revealed that the PEG and n-ZnO composite membrane outperformed the bare PEES membrane in terms of antibacterial capabilities. Overall, the findings reveal that combining n-ZnO and PEG resulted in a membrane with improved anti-fouling capabilities and hydrophilicity, making it suitable for water purification.

Ultra-low pressure PES ultrafiltration membrane with high-flux and enhanced anti-oil-fouling properties prepared via in-situ polycondensation of polyamic acid

Polyamic acid (PAA) is a flexible polymer and has abundant valuable hydrophilic groups. Herein, we developed an ultra-low pressure ultrafiltration (UF) membrane by integrating PAA into the polyethersulfone (PES) matrix via the "in-situ polycondensation" method. PAA was well compatible with PES and distributed uniformly in the membrane. The introduction of PAA improved membrane hydrophilicity. Meanwhile, the membrane pore structures were also refined. The membrane exhibited an excellent permeability under ultra-low pressure due to its improvement of hydrophilicity and pore structures. Under 0.3 bar, compare with the water flux of PES membrane, PES/PAA membrane improved nearly 2 times (571.05 L/(m²·h)), with a high BSA rejection (≥90%). Even under a lower pressure, 0.1 bar, >300 L/(m²·h) still can be achieved. Interestingly, the membrane we developed could maintain a high performance after drying, and then is very suitable for dry preservation. PES/PAA membrane showed a high oil removal (≥92%) and could remove oil from water effectively. Besides, the membrane exhibited excellent anti-oil-fouling properties. The flux recovery rate of PES/PAA (70.0%) far exceeds that of PES (37.9%) after three filtration and cleaning cycles. The membrane we developed is very valuable in oily wastewater treatment.

Efficient and scalable synthesis of 1,5-diamino-2-hydroxy-pentane from L-lysine via cascade catalysis using engineered Escherichia coli

BACKGROUND

1,5-Diamino-2-hydroxy-pentane (2-OH-PDA), as a new type of aliphatic amino alcohol, has potential applications in the pharmaceutical, chemical, and materials industries. Currently, 2-OH-PDA production has only been realized via pure enzyme catalysis from lysine hydroxylation and decarboxylation, which faces great challenges for scale-up production. However, the use of a cell factory is very promising for the production of 2-OH-PDA for industrial applications, but the substrate transport rate, appropriate catalytic environment (pH, temperature, ions) and separation method restrict its efficient synthesis. Here, a strategy was developed to produce 2-OH-PDA via an efficient, green and sustainable biosynthetic method on an industrial scale.

RESULTS

In this study, an approach was created for efficient 2-OH-PDA production from L-lysine using engineered E. coli BL21 (DE3) cell catalysis by a two-stage hydroxylation and decarboxylation process. In the hydroxylation stage, strain B14 coexpressing L-lysine 3-hydroxylase K3H and the lysine transporter CadB-argT enhanced the biosynthesis of (2S,3S)-3-hydroxylysine (hydroxylysine) compared with strain B1 overexpressing K3H. The titre of hydroxylysine synthesized by B14 was 2.1 times higher than that synthesized by B1. Then, in the decarboxylation stage, CadA showed the highest hydroxylysine activity among the four decarboxylases investigated. Based on the results from three feeding strategies, L-lysine was employed to produce 110.5 g/L hydroxylysine, which was subsequently decarboxylated to generate a 2-OH-PDA titre of 80.5 g/L with 62.6% molar yield in a 5-L fermenter. In addition, 2-OH-PDA with 95.6% purity was obtained by solid-phase extraction. Thus, the proposed two-stage whole-cell biocatalysis approach is a green and effective method for producing 2-OH-PDA on an industrial scale.

CONCLUSIONS

The whole-cell catalytic system showed a sufficiently high capability to convert lysine into 2-OH-PDA. Furthermore, the high titre of 2-OH-PDA is conducive to separation and possesses the prospect of industrial scale production by whole-cell catalysis.

New Understanding of the Difference in Filtration Performance between Anatase and Rutile TiO2 Nanoparticles through Blending into Ultrafiltration PSF Membranes

The blending of nanomaterials into a polymeric matrix is a method known for its ability, under certain circumstances, to lead to an improvement in membrane properties. TiO₂ nanoparticles have been used in membrane research for the last 20 years and have continuously shown promise in this field of research. Polysulfone (PSf) membranes were obtained through the phase inversion method, with different TiO₂ nanoparticle concentrations (0, 0.1, 0.5, and 1 wt.%) and two types of TiO₂ crystalline structure (anatase and rutile), via the addition of commercially available nanopowders. Research showed improvement in all studied properties. In particular, the 0.5 wt.% TiO₂ rutile membrane recorded an increase in permeability of 139.7% compared to the control membrane. In terms of overall performance, the best nanocomposite membrane demonstrated a performance index increase of 71.1% compared with the control membrane.

Corn derivative mesoporous carbon microspheres supported hydrophilic polydopamine for development of new membrane: Water treatment containing bovine serum albumin

A new mixed matrix membrane (MMM) was prepared by incorporating biological mesoporous carbon microspheres (mCMSs) from corn starch polysaccharide-supported hydrophilic polydopamine (PDA), as a mesoporous and large-surface area filler, selective modifier, and pore-forming agent, into polyvinylidene fluoride (PVDF) matrix in presence of polyethylene glycol (PEG) as a hydrophilic agent. The structural parameters of the prepared membranes were characterized via FE-SEM, BET/BJH, XRD, FT-IR, and AFM analyses, sorption experiments, water permeability assessments, porosimetry tests, flux recovery ratio (FRR) evaluations, and contact angle measurements, with the so-called central composite design (CCD) been successfully applied for optimization and investigation of the effects of the operational parameters. The results were then applied to treat double-distilled water containing bovine serum albumin (BSA) utilizing a cross-module set-up. Based on the findings, the content of the mCMS-PDA in the PVDF matrix significantly affected the contact angle, pure water flux (PWF), FRR, and BSA removal. In this respect, the PWF of the PVDF-PEG-mCMS-PDA increased from 10.25 to 27.78 L/m² h with increasing the mCMS-PDA content, with the peak FRR (93.84%) of the PVDF-PEG-mCMS-PDA seen at maximum surface hydrophilicity of the membrane.

MOFs for the treatment of arsenic, fluoride and iron contaminated drinking water: A review

Over the last few decades, the global pollution of surface and groundwater poses a serious threat not only to human beings but also towards aquatic lives due to the presence of emerging contaminants. Among the others, the presence of arsenic, fluoride, and iron are considered as the most common toxic pollutants in water bodies. The emergence of metal organic frameworks (MOFs) with high porosity and surface area is represented as significant inclusion into the era of entrapping contaminants present in drinking water. In the present review article, an in-depth insight is provided on the recent developments in the removal of arsenic, fluoride, and iron from drinking water using MOFs. Various aspects related to the synthesis, latest technologies adopted for the modifications in the synthesis process and advanced applications of MOFs for the removal of such contaminants are explicitly discussed. A detailed insight was provided to understand the mechanism of various interactions of MOFs with arsenic and fluoride. With respect to arsenic, fluoride, and iron removal the ultrastructural morphology of MOFs is assessed based on different molecular arrangements. Further, commercial aspects of various MOFs are presented in order to highlight the process feasibility. Finally, various perspectives and challenges involved in process scale up are comprehensively narrated with an aspiration of futuristic developments. The paper will be beneficial to the readers for acquiring a piece of in-depth knowledge on MOFs and its various synthesis approaches along with remarkable achievements for the removal of arsenic, fluoride, and iron from contaminated drinking water.

A high-flux and anti-interference dual-functional membrane for effective removal of Pb(II) from natural water

The development of high efficiency filter membranes, particularly those capable of removing trace heavy metals from drinking water sources, is a global challenge. In this study, a dual-functional membrane (P_mG_n@PVDF) was successfully developed by doping graphene oxide (GO) and then depositing polydopamine (PDA). The pure water flux (Jw) was 188 LMH/bar and Pb(II) could be effectively removed in the water volume of 2106.36 L m^-2. Both PDA and GO performed positive functions. PDA layer exhibited a high affinity toward Pb(II) by chelating with amino groups. And doping GO maintained a high pure water flux, which had been decreased by the extra PDA layer. In addition, the effective treatment volume of Pb(II) was elevated to 5029.06 L/m² by the co-existence of citric acid, since neutral PbHL coordinated with neutral NH₂ and cationic PbL- interacted with NH₃⁺ through electrostatic attraction. Furthermore, P_mG_n@PVDF showed the excellent anti-interference performance in high salt and nature organic matters solutions. Thus, this novel dual-functional membrane could be considered as a competitive alternative of NF/RO for the efficient and advanced removal towards heavy metals from natural water.