Enhanced anti-wetting, slippery-surface membranes engineered for long-term operation with hypersaline synthetic and seawater feeds in membrane distillation

Aftab Ahmad Khan,김종오 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.96 No.-

This study aimed to prepare a membrane by engineering a “slippery” surface on a polyethersulfone (PES)membrane for long-term, direct-contact membrane distillation (DCMD). Membrane surfaces andwettability were analyzed usingfield-emission scanning electron microscopy, atomic force microscopy,and attenuated total reflection–Fourier-transform infrared spectroscopy. Contact angles and liquid entrypressures also were measured. The wetting and fouling-resistance competence of the modified PESmembrane (PES-M) in DCMD was assessed using two hypersaline feed solutions, i.e., multiple salts(2000 mg L 1 [CaSO4 + CaCO3 + CaCl2 2H2O + NaCl]) + 20 mg L 1 humic acid (MSHA-F) and Busan seawaterfeed. The effectiveness of the PES-M membrane against the MSHA-F solution was evaluated over multiplecycles. The membrane was cleaned after each 50-h cycle and successfully reused for three consecutivecycles after cleaning with a clean-in-place method. The PES-M membrane displayed robust performanceagainst both feeds, particularly against MSHA-F for 150 h, during which it lost only 20%flux and showed afinal conductivity of 68.8 mS/cm. The PES-M membrane is a resilient candidate that can resist fouling andwetting.

Optogenetics Applications for Treating Spinal Cord Injury

Aftab Ahmad,Sadia Ashraf,Shoji Komai 대한척추외과학회 2015 Asian Spine Journal Vol.9 No.2

Cases of spinal cord injury (SCI) are increasing all over the world; and in USA alone, there are 273,000 patients, which not only leads to morbidity and mortality but also results in a great economic burden. Many approaches are being used at the pre-clinical and clinical level to treat SCI including therapeutic agents, surgical decompression, stem cell therapy etc. Recently, a new approach called optogenetics has emerged in which light sensitive proteins are used to switch neurons on and off, and this approach has great potential to be used as therapy due to its specificity and rapid response in milliseconds. Few animal studies have been performed so far in which the respiratory and bladder function of rats was restored through the use of optogenetics. On the basis of promising results obtained, in the future, this approach can prove to be a valuable tool to treat patients with SCI.

Amphiphobicity evaluation of fluorinated sillica modified polyethersulfone membrane by concentrating the emulsified feed in membrane distillation

Aftab Ahmad Khan,Muhammad Irfan Siyal,Chang-Kyu Lee,Chansoo Park,Jong-Oh Kim 대한환경공학회 2019 대한환경공학회 학술발표논문집 Vol.2019 No.-

Hybrid organic-inorganic functionalized polyethersulfone membrane for hyper-saline feed with humic acid in direct contact membrane distillation

Khan, Aftab Ahmad,Siyal, Muhammad Irfan,Lee, Chang-Kyu,Park, Chansoo,Kim, Jong-Oh Elsevier 2019 Separation and purification technology Vol.210 No.-

<P><B>Abstract</B></P> <P>In this study, hybrid organic-inorganic functionalized polyethersulfone (PES) membrane was prepared for treating hyper-saline feed solutions containing humic acid (HA) foulant. The membrane modification was carried out by dip-coating with silica nanoparticles, followed by vacuum filtration coating with 1H,1H,2H,2H-perfluorodecyl triethoxysilane and polydimethylsiloxane. The membranes were characterized by field emission scanning electron microscope, atomic force microscope, Fourier transform infrared, and thermal gravimetric analyses. The evaluation of membranes with water contact angle, liquid entry pressure, direct contact membrane distillation (DCDM), and stability tests, proved the durable amphiphobic nature of the modified PES membrane (PDMS-FAS/SiNPs). The membrane performance was respectively better from that of commercial polypropylene (PP) and polyvinylidene fluoride (PVDF) membranes. In the DCMD of a feed solution of 1 M NaCl and 10 mg L<SUP>−1</SUP> HA, the flux of the PDMS-FAS/SiNPs membrane remained consistent (17 LMH), with a permeate conductivity of 33.96 µS cm<SUP>−1</SUP>. The optimized modified membrane showed better performance in terms of permeate flux, salt rejection, and anti-fouling behavior in DCMD. These wonderful results of functionalized PDMS-FAS/SiNPs PES membrane are attributed to the step-wise simple, and inexpensive dip-coating followed by vacuum filtration coating using efficient hybrid organic-inorganic material combination.</P> <P><B>Highlights</B></P> <P> <UL> <LI> PES membrane functionalization using hybrid organic-inorganic material. </LI> <LI> Dip and vacuum filtration coating methods were used for membrane modification. </LI> <LI> Consistent rejection of hyper-saline feed solution containing humic acid. </LI> <LI> Functionalized PES membrane performance compared with other membranes. </LI> <LI> Modified PES membrane was more durable than commercially available PP and PVDF. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Optimization of membrane modification using SiO₂ for robust anti-fouling performance with calcium-humic acid feed in membrane distillation

Khan, Aftab Ahmad,Khan, Imtiaz Afzal,Siyal, Muhammad Irfan,Lee, Chang-Kyu,Kim, Jong-Oh Elsevier 2019 Environmental research Vol.170 No.-

<P><B>Abstract</B></P> <P>The goal of this study was to prepare a robust anti-wetting and anti-fouling polyethersulfone (PES) membrane for the rejection of a highly saline (NaCl and CaCl<SUB>2</SUB>·2H<SUB>2</SUB>O) feed solution containing humic acid (HA) in direct contact membrane distillation (DCMD). Response surface methodology (RSM) was used to determine the optimum formulation of the used materials. The variable factors selected were polydimethyl siloxane (PDMS) and silica (SiO<SUB>2</SUB>); liquid entry pressure (LEP) and contact angle (CA) were selected as responses. Scanning electron microscopy (SEM) analysis confirmed the SiO<SUB>2</SUB> deposition and Fourier-transform infrared spectroscopy (FTIR) test evidenced the new functional groups i.e., Si–OH, siloxane, and C–F bond vibrations at 3446, 1099 cm<SUP>−1</SUP>, and 1150–1240 cm<SUP>−1</SUP> respectively on the membrane surface. The average roughness (Ra) was increased four times for the coated membranes (0.202–0.242 µm) as compared to that for pristine PES membrane (0.053 µm). The optimum PES-13 membrane exhibited consistent flux of 12 LMH and salt rejection (> 99%) with anti-fouling characteristic in DCMD using the feed solution of 3.5 wt% NaCl + 10 mM CaCl<SUB>2</SUB>·2H<SUB>2</SUB>O + 10 mg L<SUP>−1</SUP> HA. The PES-13 membrane may therefore be a key membrane for application in DCMD against CaCl<SUB>2</SUB>·2H<SUB>2</SUB>O-containing salty solutions with HA.</P> <P><B>Highlights</B></P> <P> <UL> <LI> PES membrane was prepared for application in DCMD using silica nanoparticles. </LI> <LI> Response surface methodology was employed to optimize the coating formulation. </LI> <LI> Modified membranes were resistant to fouling against calcium-humic acid feed. </LI> <LI> The high fluxes for PES-13 membrane were recorded with all three feed solutions. </LI> </UL> </P>

Algal extracts based biogenic synthesis of reduced graphene oxides (rGO) with enhanced heavy metals adsorption capability

Shahbaz Ahmad,Aftab Ahmad,Sikandar Khan,Shujaat Ahmad,Idrees Khan,Shah Zada,Pengcheng Fu 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.72 No.-

Efficient reduction of GO was performed, using cellular extracts of three algal strains. The rGO werecharacterized by SEM, TEM, UV-Visible spectroscopy, XRD, FTIR, Raman spectroscopy, Zeta potential andredox potentials. The rGO were then used as decontaminating agents for heavy metals (Cu and Pb), inwaste water. GO reduced via JSC-1 have removed up to 93% Cu and 82% Pb (adsorption capacity of93 mg g 1 and 82 mg g 1, respectively), by 211-9a have removed 74% (74 mg g 1) Cu and 89% (89 mg g 1)Pb, while by 211-11n have adsorbed 91% (91 mg g 1) Cu and 95% Pb (95 mg g 1), within 30 min.

EPIS, DOMINIONS AND ZIGZAG THEOREM IN COMMUTATIVE GROUPS

Shah, Aftab Hussain,Nabi, Muneer,Ahanger, Shabir Ahmad The Kangwon-Kyungki Mathematical Society 2022 한국수학논문집 Vol.30 No.3

In this paper, we introduce the notion of tensor product in groups and prove its existence and uniqueness. Next, we provide the Isbell's zigzag theorem for dominions in commutative groups. We then show that in the category of commutative groups dominions are trivial. This enables us to deduce a well known result epis are surjective in the category of commutative groups.

IDENTITIES PRESERVED UNDER EPIS OF PERMUTATIVE POSEMIGROUPS

Shah, Aftab Hussain,Bano, Sakeena,Ahanger, Shabir Ahmad The Kangwon-Kyungki Mathematical Society 2022 한국수학논문집 Vol.30 No.2

In 1985, Khan gave some sufficient conditions on semigroup identities to be preserved under epis of semigroups in conjunction with the general semigroup permutation identity. But determination of all identities which are preserved under epis in conjunction with the general permutation identity is an open problem in the category of all semigroups and hence, in the category of all posemigroups. In this paper, we first find some sufficient conditions on an identity to be preserved under epis of posemigroups in conjunction with any nontrivial general permutation identity. We also find some sufficient conditions on posemigroup identities to be preserved under epis of posemigroups in conjunction with the posemigroup permutation identity, not a general permutation identity.

Synthesis of Polypyrrole Nano/Microspheres Using Cobalt(III) as an Oxidizing Agent and Its Ammonia Sensing Behavior

Zahoor Ahmad,Muhammad Aziz Choudhary,Aneela Mehmood,Riffat Wakeel,Tashfeen Akhtar,Muhammad Aftab Rafiq 한국고분자학회 2016 Macromolecular Research Vol.24 No.7

Polypyrrole (ppy) has been synthesized by employing [Co(NH3)6]Cl3 as a new oxidizing agent under basic condition in aquous solution. The optimized ratio of monomer to oxidizing agent has been taken as 1:2. The reaction was allowed to continue for 24-48 h at room temperature. The as synthesized ppy displayed well defined morphology, which was seemed as time dependent. It was nanospheres at 24 h, micro/nano mixture at 36 h and microspheres and microfibers at 48 h. The FTIR confirmed the formation of ppy due to the presence of characteristics broader ring and N-H stretching vibrations. The XRD showed the development of crystallites only within the fibrous ppy. The thermal and structural correlation was determined using TGA and DSC techniques alongwith SEM. The polymer was found to be considerably more stable as compared with similarly synthesized using other such oxidants. The conductivity of pure polymer and effect of NH3 over its conductivity was analyzed by four probe technique. Its strong potential of NH3 sensing has been confirmed from this technique due to showing linear increase in its conductivity. These results demonstrated that cobalt(III) is a potential oxidizing agent to produce thermally stable nano/microspheres of ppy. Moreover, the material was found quite useful for its characteristics of NH3 sensing that can be applied for other nitrogenous bases.

Overexpression and Purification of PreS Region of Hepatitis B Virus Antigenic Surface Protein adr Subtype in Escherichia coli

Abbas, Naaz,Ahmad, Aftab,Shakoori, Abdul Rauf Korean Society for Biochemistry and Molecular Biol 2007 Journal of biochemistry and molecular biology Vol.40 No.6

PreS domain of Hepatitis B virus (HBV) surface antigen is a good candidate for an effective vaccine as it activates both B and T cells besides binding to hepatocytes. This report deals with overexpression and purification of adr subtype of surface antigen that is more prevalent in Pakistan. PreS region, comprising 119 aa preS1 region plus a 55 aa preS2 region plus 11 aa from the N-terminal S region, was inserted in pET21a+ vector, cloned in E. coli $DH5\alpha$ cells and expressed in E. coli BL21 codon+ cells. The conditions for over expression were optimized using different concentrations of IPTG (0.01-5 mM), and incubating the cells at different temperatures (23-$41^{\circ}C$) for different durations (0-6 h). The cells were grown under the given optimized conditions (0.5 mM IPTG concentration at $37^{\circ}C$ for 4 h), lysed by sonication and the protein was purified by ion exchange chromatography. On the average, 24.5 mg of recombinant protein was purified per liter of culture. The purified protein was later lyophilized and stored at $-80^{\circ}C$.