Chromium adsorption efficiency by functional polymeric nanocomposite membrane: A case study for environmental sustainability

Graphene oxide (GO) is increasingly used and inevitably released into aquatic environments, facilitating its interaction with traditional pollutants such as heavy metal ions. However, the potential effect of GO on the toxicity of heavy metal ions to aquatic animals is unknown. This work aims to assess the toxicity of heavy metal ions (Cu(ii), Cd(ii), and Zn(ii)) on Daphnia magna (D. magna) in the presence of GO. GO nanoparticles remarkably reduced the concentrations of heavy metal ions by adsorption and decreased the metal accumulation in D. magna. The maximum desorption rate of heavy metal ions from metal-adsorbed GO was below 5%. At pH 7.8, with addition of 2 mg L−1 GO, the 72 h median lethal concentration (LC50) values of Cu(ii), Cd(ii), and Zn(ii) were increased from 14.3, 38, and 780 μg L−1 to 36.6, 72, and 1010 μg L−1, respectively. The analyses of oxidative stress indicators suggested that the oxidative damage to D. magna by heavy metal ions was reduced after addition of GO at pH 7.8. Moreover, a higher pH level in the growing range (6.5 to 8.5) of D. magna led to weaker toxicity of metal ions with GO addition due to more adsorption and less bioaccumulation. The results revealed the role of GO nanoparticles in the mitigated toxicity of heavy metal ions in the aquatic environment.

This paper reports the development of nonwoven fabric by needle-punching technique for filter press application in textile effluent treatment plant. For filter press development, the nonwoven fabric was reinforced with the nylon scrim as the central layer in order to withstand the filtration pressure. The nonwoven fabrics were developed using different denier polyester fibres and changing punch density. The influence of fibre fineness and punch density on the properties of nonwovens was investigated. The filtration parameters such as filtration efficiency, dewatering efficiency, blinding tendency and cake discharge properties of the developed nonwoven filter fabrics filter fabrics were evaluated and compared with existing woven fabric filter media. The influence of calendering on the filtration properties of the nonwovens was also studied. The results showed that bursting strength of the developed nonwovens increased with increase in fibre fineness and decrease in punch density. It was also found that the air permeability of the developed nonwovens varied inversely in relation to punch density and the proportion of fine fibres. It was observed that developed nonwovens had 8% higher filtration efficiency and 6% higher dewatering efficiency compared to the existing woven fabric filter media. The blinding resistance and cake discharge properties were slightly lower than that of woven fabric filter. It was found that calendering improves filtration properties of the developed nonwoven fabrics.

Pyrene derivatives are regularly proposed for use in biochemistry as dyes due to their photochemical characteristics. Their antibacterial properties are, however, much less well understood. New complexes based on 4-[(E)-2-(1-pyrenyl)vinyl]pyridine (PyPe) have been synthesized with metal ions that are known to possess antimicrobial properties, such as zinc(II), cadmium(II), and mercury(II). The metal ion salts, free ligand, combinations thereof, and the coordination compounds themselves were tested for their antibacterial properties through microdilution assays. We found that the ligand is able to modulate the antibacterial properties of transition metal ions, depending on the complex stability, the distance between the ligand and the metal ions, and the metal ions themselves. The coordination by the ligand weakened the antibacterial properties of heavy metal ions (Cd(II), Hg(II), Bi(III)), allowing the bacteria to survive higher concentrations thereof. Mixing the ligand and the metal ion salts without forming the complex beforehand enhanced the antibacterial properties of the cations. Being non-cytotoxic itself, the ligand therefore balances the biological consequences of heavy metal ions between toxicity and therapeutic weapons, depending on its use as a coordinating ligand or simple adjuvant.

A novel nanofiber composite nanofiltration membrane was fabricated through coating calcium alginate hydrogel on electrospun polyhydroxybutyrate/carbon nanotubes (CaAlg-c-PHB/CNT) nanofiber membrane. The CaAlg-c-PHB/CNT nanofiber composite membrane was investigated by means of SEM, FTIR, Raman, XRD, DSC, TGA, zeta potential and water contact angle (WCA) measurements. The tensile tests of the CaAlg-c-PHB/CNT nanofiber composite membrane were performed in dry and wet state. The filtration properties of the CaAlg-c-PHB/CNT nanofiber composite membrane were measured in term of flux and rejection rate at operation pressure ranged from 0.1 to 0.7 MPa. The antifouling properties were investigated by emulsified oil–water and BSA solution separation. Results showed that the CaAlg-c-PHB/CNT nanofiber composite membrane with 1 wt% CNT had the highest tensile strength and initial Modulus with the value of 6.14, 5.12 and 142.64, 127.5 MPa in dry and wet state, respectively. The water contact angle was decreased remarkably from 83.6° to 17.8° after calcium alginate hydrogel coating. The pure water flux (PWF) was increased from 68.61 to 150.72 L/m2 h with operation pressure increased from 0.1 to 0.7 MPa. Five dyes with different molecular weight ranged from 400 to 900 g/mol were selected for filtration test. The rejection rate could maintain over 90% for dyes with the molecular weight higher than 600 g/mol under 0.5 MPa. The CaAlg-c-PHB/CNT nanofiber composite membrane showed good antifouling performance for both oil and protein. These results indicated that the CaAlg-c-PHB/CNT composite nanofiber membrane can be used as an effective nanofiltration membrane operated at high pressure for dye removal.

Jute fibers were grafted with acrylic acid by using the direct gamma irradiation technique, which used as an adsorbent substrate for the toxic heavy metal ions such as Hg 2+ and Pb 2+ from their aqueous solutions. The structure and crystallinity of the grafted jute fibers were characterized by using Fourier‐transform infrared spectroscopy and X‐ray diffraction, respectively. The effect of pH range of the metal ion solutions, contact time, and the adsorption kinetics of the adsorption process were investigated. The effect of the initial concentration of dissolved metal ions and the adsorption isotherm for both Langmuir and Freundlich adsorption models were also investigated. From the results, it can be concluded that the adsorption process obeys the second‐order kinetic reaction and follows the Langmuir adsorption isotherm model, while, about 86 and 80% of Pb 2+ and Hg 2+ , respectively, were adsorbed at pH 5 and 6 after a contact time of 60 min. J. VINYL ADDIT. TECHNOL., 24:339–346, 2018. © 2017 Society of Plastics Engineers

In this study, polypropylene meltblown nonwoven fabrics with different structure parameters such as fiber diameter, pore size, and areal density were prepared by the industrial production line. The morphology of meltblown nonwoven fibers was evaluated by using scanning electron microscope, and the diameter of fibers was analyzed by using image-pro plus software from at least 200 measurements. The pore size of nonwoven fabric was characterized by a CFP-1500AE type pore size analyzer. The filtration efficiency and pressure drop were evaluated by TSI8130 automatic filter. The results showed that the pressure drop of nonwoven fabrics decreased with the increase in pore size; the filtration efficiency and the pressure drop had a positive correlation with the areal density. However, when the areal density is in the range of 27–29 g/m2, both filtration efficiency and pressure drop decreased with the increase of areal density; when the areal density was kept constant, the filtration efficiency decreased as the pore size decreased; when the pore size of the meltblown nonwoven fabric is less than 17 μm, the filtration efficiency increased as the pore diameter decreased; when the pore diameter of the nonwoven fabric is larger than 17 μm. In a wide range, the pressure drop decreased as the fiber diameter decreased.

The polyacrylonitrile/polyvinylidene fluoride (PAN/PVDF) nanocomposite fiber membranes were prepared by the coaxial electrospinning technology using PVDF as the core layer and PAN as the skin layer. Structure optimization of PAN/PVDF nanocomposite fiber membrane was carried out by adding three different nanoparticles of nano-silica powder, fumed silica and silica sol to the PAN/PVDF nanocomposite fiber membrane and changing the extrusion speed of the skin-core layer solution. Meanwhile, its pore structure parameters, surface morphology, hydrophilicity and mechanical properties were studied by BET, SEM, water contact angle, fiber strength meter and so on. The results show that the conductivity of the solution after adding silica sol to the solution reaches 32.90 μL/cm, the PAN/PVDF nanocomposite fiber membrane has the best mechanical properties, and the longitudinal breaking strength reaches 13.02 MPa. The quality factor of mask cloth containing silica sol reaches 0.0236, which is much larger than the quality factor of pure polypropylene (PP) non-woven, which is 0.0127, and the filterability is significantly increased.

Recently, because of the outbreak of COVID‐19, the demand for various types of filter elements in protective materials has increased globally. Furthermore, new requirements for the filtration performance of PM2.5 liquid (oil) particles have been put forward. In this work, Superhydrophobic and superoleophobic composite nanofibers with excellent filtration capacity for oil and salt particles are developed through the modification of polyacrylonitrile (PAN) by fluoro‐polyurethane (FPU) doping. The results show that the PAN/FPU composite nanofibers doped with 9 wt% FPU has a uniform fiber morphology with a diameter of 240 ± 30 nm. Compared to the pure PAN nanofibers, the water‐based contact angle of PAN/FPU increases from 90 ± 5° to 151 ± 5°, and the oil‐based contact angle increases from 58 ± 2° to 152 ± 3°. Importantly, at a high flow rate of 95 L min−1, the filtration efficiency of the PAN/FPU nanofiber membrane for 0.3 µm oil particles increases from 92 ± 1% to 99.2 ± 0.1%. After cyclic loading, the filtration efficiency of 0.3 µm oil particles remains above 98%. Meanwhile, the filtration efficiency for 0.3 µm salt particles remains at 98.23 ± 0.1%. The PAN/FPU nanofiber membrane developed in this work is effective in applications and has good market prospects as a protective filtration material.

Designed multifunctionalized magnetic mesoporous microsphere for sequential sorption of organic and inorganic pollutants

Separation of proteins and toxic heavy metal ions from aqueous solution by CA/PC blend ultrafiltration membranes

Design of high efficiency PVDF-PEG hollow fibers for air filtration of ultrafine particles

Construction of MoS2 nanoarrays and MoO3 nanobelts: Two efficient adsorbents for removal of Pb(II), Au(III) and Methylene Blue

Novel functionalized and/or grafted crosslinked chitosan adsorbents were synthesized and used to remove several toxic heavy metal ions such as nickel, lead, chromium, and cadmium ions from contaminated water. The chitosan biopolymer was functionalized by maleic anhydride (CS_MA) acting also as a crosslinking agent. Glutaraldehyde-crosslinked chitosan (CS_GA) grafted with poly(methyl methacrylate) (CS_MMA) was also synthesized. The synthesized adsorbents were characterized using a variety of analytical techniques such as SEM, TGA, and FTIR, which confirmed their chemical structures and morphology. The adsorption capacity of the adsorbents was analyzed under various conditions of contact time, adsorbent dose, initial concertation, temperature, and pH and evaluated against those of pure chitosan (CS) and the crosslinked chitosan(CS_GA). The ultimate removal conditions were 0.5 g/100 mL adsorbent dose, an initial metal ion concentration of 50 ppm, a temperature of 45 °C, and pH 9. CS_MMA had the highest removal percentages for all metal ions, ranging from 92% to 94%. The adsorption was demonstrated to fit a pseudo-first-order model that followed a Langmuir adsorption isotherm. The results highlight the capacity of the synthesized polymers to efficiently remove major toxic contaminants at low cost from contaminated water, present especially in low-income areas, without harming the environment.

Selective recovery of mercury by Procion Brown MX 5BR immobilized poly(hydroxyethylmethacrylate/chitosan) composite membranes

The adsorption and photocatalytic degradability of poly(lactic acid)/modified copper-based metal-organic frameworks meltblown fiber membranes on volatile organic compounds