Fabrication of robust ceramic supported polymeric composite nanofiltration membrane for heavy metal contaminated wastewater treatment

Nanofiltration (NF) membranes with positive charge are essential for efficient removal of heavy metals and salts from waste water. In this work surface modified positively charged novel `ceramic-supported-polymeric' (CSP) composite NF membranes were fabricated with the copper ions embedded crosslinked polyethyleneimine polymer matrix over tubular ceramic substrate using facile dipcoating method. EDX, ATR-FTIR, XPS, FESEM, AFM and contact angle analyses were performed to characterize the chemical structures and morphologies of the prepared membranes. The composite NF membrane exhibited satisfactory pure water permeability (PWP) of 8.1 L.m(-2).h(-1).bar(-1) and promising salt (87.19 % and 74.41 % for Mg2+ and Ca2+, respectively) and heavy metal ion rejections (91.73 %, 83.15 % and 75.50 % for Zn2+, Ni2+ and Cd2+, respectively). Activation energy and overall size-exclusion-dehydration phenomena along with steric hindrance and Donnan electrostatic exclusion plays an important role for heavy metals and salts rejection. In addition, the membrane showed excellent antifouling properties (>99 % humic acid removal) with high flux recovery ratio (77.6 %) and low flux decline ratio (33 %) for 5 h operations (3rd cycle) together with outstanding antibiofouling ability towards Brevibacillusagri and Leclerciaadecarboxylata. Furthermore, excellent chemical stability of the membrane suggests its potential appli-cation for waste water treatment under critical conditions

Removal of heavy metals by surface tailored copper ion enhanced ceramic-supported-polymeric composite nanofiltration membrane

Ceramic-supported-polymeric (CSP) composite membranes combine the benefits of robust ceramic support with tunable surface properties of polymeric active layer. The present work reports the fabrication of novel CSP composite nanofiltration membranes wherein surface ionization of the membrane active layers has been carried out by a facile process of chelating copper ions with the crosslinked polyethyleneimine polymer matrix of membrane top layer. Different concentrations of copper chloride solutions were used and their effect on mem-brane surface properties was investigated using EDX, XPS and AFM analyses. Performance of the membranes in removal of both cationic and anionic heavy metals, namely, Ni(II), Cd(II), Pb(II), Zn(II), As(V) and Cr(VI) from aqueous solution was studied. Excellent removal (> 95%) of all the heavy metals and optimum flux was achieved in case of GPCu0.5 membrane (surface modified with 0.5 wt% copper chloride solution). No significant decrease in flux and rejection rate of the membrane during 10 h high pressure (8 bar) operation suggested longevity of the membrane. The slow release of copper ions indicated the much-expected anti-biofouling nature of the mem-brane. Appreciable rejection behavior of the copper ion enhanced CSP composite membrane towards multiple heavy metals demonstrates its potential for practical water treatment application

Removal of cadmium by in-situ Cu nanoparticle enhanced ceramic-supported-polymeric composite NF membrane

A novel ceramic-polymer composite nanofiltration membrane was fabricated using in-situ generated Cu nanoparticles by dip coating over modified ceramic support tube. The prepared membrane was used for Cd (II) removal from contaminated water. Generation of in-situ Cu NPs on/in the membrane was characterized by SEM and XPS analysis. Incorporation of NPs formed by in-situ chemical reduction technique improved the pore size of modified ceramic substrate towards NF range (similar to 1 nm). The positively charged composite NF membrane exhibited satisfactory performance with respect to pure water permeability (8.09 L m(-2) h(-1) bar(-1)) and Cd(II) rejection of 95.5%. (C) 2021 Elsevier Ltd. All rights reserved

Powder metallurgical processing of equiatomic AlCoCrFeNi high entropy alloy: Microstructure and mechanical properties

Phase formation, microstructural evolution and the mechanical properties of novel multi-component equiatomic AlCoCrFeNi high entropy alloy synthesized by high energy ball milling followed by spark plasma sintering have been reported here. The microstructure of the mechanically alloyed (MA) powder and sintered samples were studied using X-ray diffraction, scanning electron and transmission electron microscopy, whereas the detailed investigation of the mechanical properties of the sintered samples were measured using micro and nano hardness techniques. The fracture toughness measurements were performed by applying single edge V notch beam (SEVNB) technique. The MA powder shows the presence of FCC (tau) and BCC (kappa) solid solution phases. Extended ball milling (up to 60 h) does not change the phases present in MA powder. The sintered pellets show phase-separated microstructure consisting of Al-Ni rich L1(2) phase, alpha' and tetragonal Cr-Fe-Co based sigma phase along with Al-Ni-Co-Fe FCC solid solution phase (epsilon) for sample sintered from 973 to 1273 K. The experimental evidences indicate that BCC (kappa) solid solution undergoes eutectoid transformation during sintering leading to the formation of L1(2) ordered alpha' and sigma phases, whereas FCC (tau) phase remains unaltered with a slight change in the lattice parameter. The hardness of the sample increases with sintering temperature and a sudden rise in hardness is observed 1173 K. The sample sintered at 1273 K shows the highest hardness of similar to 8 GPa. The elastic modulus mapping clearly indicates the presence of three phases having elastic moduli of about 300, 220 and 160 GPa. The fracture toughness obtained using SEVNB test shows a maximum value of 3.9 MPa m(1/2), which is attributed to the presence of brittle nanosized sigma phase precipitates. It is proposed that significant increase in the fraction of sigma phase precipitates and eutectoid transformation of the tau phase contribute to increase in hardness along with better densification at higher sintering temperatures

Development of high performance pervaporation desalination membranes: A brief review

Water scarcity rises as the level of water pollution continues to increase with the progress of urbanization, industrialization and exponential growth of population. Therefore, saline water of the sea should also be made suitable rather than river water to meet the huge global demand of clean and safe drinking water. Pervaporation (PV) desalination, among many purification and separation processes, is a promising technology to reduce the crisis of global drinking water supply. From this perspective, the key success of PV desalination relies on its remarkable salt rejection from highly saline water with appropriate flux to obtain fresh water by using a suitable membrane. In this review we aim to provide a comprehensive assessment of PV desalination membrane materials, transport phenomena, the advantages of the process over comparable technologies (e.g., fractional distillation, membrane distillation, reverse osmosis) and the advantages of crosslinking during the preparation of composite membranes. This review further highlights the advantages of inorganic ceramic substrates as a support of composite membranes and the use of hydrophilic polymers as active layer for preparing stable and robust crosslinked PV desalination membranes.(c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved

Histone H3K9 acetylation level modulates gene expression and may affect parasite growth in human malaria parasite Plasmodium falciparum

Three-dimensional positioning of the nuclear genome plays an important role in the epigenetic regulation of genes. Although nucleographic domain compartmentalization in the regulation of epigenetic state and gene expression is well established in higher organisms, it remains poorly understood in the pathogenic parasite Plasmodium falciparum. In the present study, we report that two histone tail modifications, H3K9Ac and H3K14Ac, are differentially distributed in the parasite nucleus. We find colocalization of active gene promoters such as Tu1 (tubulin-1 expressed in the asexual stages) with H3K9Ac marks at the nuclear periphery. By contrast, asexual stage inactive gene promoters such as Pfg27 (gametocyte marker) and Pfs28 (ookinete marker) occupy H3K9Ac devoid zones at the nuclear periphery. The histone H3K9 is predominantly acetylated by the PCAF/GCN5 class of lysine acetyltransferases, which is well characterized in the parasite. Interestingly, embelin, a specific inhibitor of PCAF/GCN5 family histone acetyltransferase, selectively decreases total H3K9Ac acetylation levels (but not H3K14Ac levels) around the var gene promoters, leading to the downregulation of var gene expression, suggesting interplay among histone acetylation status, as well as subnuclear compartmentalization of different genes and their activation in the parasites. Finally, we found that embelin inhibited parasitic growth at the low micromolar range, raising the possibility of using histone acetyltransferases as a target for antimalarial therapy

Histone H3K9 acetylation level modulates gene expression and may affect parasite growth in human malaria parasite Plasmodium falciparum

Three-dimensional positioning of the nuclear genome plays an important role in the epigenetic regulation of genes. Although nucleographic domain compartmentalization in the regulation of epigenetic state and gene expression is well established in higher organisms, it remains poorly understood in the pathogenic parasite Plasmodium falciparum. In the present study, we report that two histone tail modifications, H3K9Ac and H3K14Ac, are differentially distributed in the parasite nucleus. We find colocalization of active gene promoters such as Tu1 (tubulin-1 expressed in the asexual stages) with H3K9Ac marks at the nuclear periphery. By contrast, asexual stage inactive gene promoters such as Pfg27 (gametocyte marker) and Pfs28 (ookinete marker) occupy H3K9Ac devoid zones at the nuclear periphery. The histone H3K9 is predominantly acetylated by the PCAF/GCN5 class of lysine acetyltransferases, which is well characterized in the parasite. Interestingly, embelin, a specific inhibitor of PCAF/GCN5 family histone acetyltransferase, selectively decreases total H3K9Ac acetylation levels (but not H3K14Ac levels) around the var gene promoters, leading to the downregulation of var gene expression, suggesting interplay among histone acetylation status, as well as subnuclear compartmentalization of different genes and their activation in the parasites. Finally, we found that embelin inhibited parasitic growth at the low micromolar range, raising the possibility of using histone acetyltransferases as a target for antimalarial therapy

Plasmodium falciparum GCN5 acetyltransferase follows a novel proteolytic processing pathway that is essential for its function

The pathogenesis of human malarial parasite Plasmodium falciparum is interlinked with the timely controlled gene expression during its complex life cycle. Therefore, epigenetic mechanisms are of paramount importance for parasite gene expression. PfGCN5 histone acetyltransferase (HAT), an essential enzyme, acetylates histone 3 and regulates global gene expression in the parasite. Here, we show the existence of a novel proteolytic processing of PfGCN5 that is crucial for its activity in vivo. We find that a cysteine protease like enzyme is required for the processing of PfGCN5 protein. Immunofluorescence and immuno-EM analysis suggest that the processing event occurs around the digestive vacuole of the parasite following the classical ER-Golgi secretory pathway before it reaches nucleus. Furthermore, blocking of PfGCN5 processing leads to the concomitant reduction of protein occupancy at the gene promoters with reduced H3K9 acetylation level, highlighting the important correlation between the processing event and its activity. Altogether, our study reveals a unique processing event of a nuclear protein PfGCN5 with unforeseen role of a food vacuolar cysteine protease with possibility of the development of new antimalarials against these targets

Impaired reciprocal regulation between SIRT6 and TGF-β signaling in fatty liver

Dysregulated transforming growth factor-beta (TGF-β) signaling contributes to fibrotic liver disease and hepatocellular cancer (HCC), both of which are associated with fatty liver disease. SIRT6 limits fibrosis by inhibiting TGF-β signaling through deacetylating SMAD2 and SMAD3 and limits lipogenesis by inhibiting SREBP1 and SREBP2 activity. Here, we showed that, compared to wild-type mice, high-fat diet-induced fatty liver is worse in TGF-β signaling-deficient mice (SPTBN1 ) and the mutant mice had reduced SIRT6 abundance in the liver. Therefore, we hypothesized that altered reciprocal regulation between TGF-β signaling and SIRT6 contributes to these liver pathologies. We found that deficiency in SMAD3 or SPTBN1 reduced SIRT6 mRNA and protein abundance and impaired TGF-β induction of SIRT6 transcripts, and that SMAD3 bound to the SIRT6 promoter, suggesting that an SMAD3-SPTBN1 pathway mediated the induction of SIRT6 in response to TGF-β. Overexpression of SIRT6 in HCC cells reduced the expression of TGF-β-induced genes, consistent with the suppressive role of SIRT6 on TGF-β signaling. Manipulation of SIRT6 abundance in HCC cells altered sterol regulatory element-binding protein (SREBP) activity and overexpression of SIRT6 reduced the amount of acetylated SPTBN1 and the abundance of both SMAD3 and SPTBN1. Furthermore, induction of SREBP target genes in response to SIRT6 overexpression was impaired in SPTBN1 heterozygous cells. Thus, we identified a regulatory loop between SIRT6 and SPTBN1 that represents a potential mechanism for susceptibility to fatty liver in the presence of dysfunctional TGF-β signaling