Membrane Engineering for Water Engineering

New imidazolium-based ionic liquids for mitigating carbon steel corrosion in acidic condition

Two environmentally friendly inhibitors of imidazolium-based ionic liquids namely 3-benzyl-1-hexadecyl-1H-imidazol-3-ium chloride (IL-H), and 3-(4-chlorobenzyl)-1-hexadecyl-1H-imidazol-3-ium chloride (IL-Cl) were manufactured and their chemical structures were confirmed by spectra tools (FT-IR, and 1H NMR). The utilizing of these two new ionic liquids as green corrosion inhibitors for low carbon steel (LCS) in 1.0 M HCl under altered experimental conditions. Mass loss (ML), potentiodynamic polarization (PP), AC impedance spectroscopy (EIS) and surface morphology are take place in this study. The protection performance found to increase with increasing ionic liquid dose and temperature, reaching 92.9% and 95.1% for IL-H and IL-Cl at 120 ppm, respectively. Based on the PP records, the investigated ionic liquids behave as mixed-type inhibitors, influencing both anodic and cathodic responses. The inhibitory activity from these explored ionic liquids was stimulated by their adsorption on the effective surfaces of the steel surface in accordance with the Langmuir adsorption isotherm. The Density Functional Theory (DFT) method is used to analyze the relationship between quantum chemical calculations and the protection efficiency of ionic liquids.

Nanoparticles Modified With Cationic Thiol Surfactant as Efficient Inhibitors for the Corrosion of Carbon Steel

In this work, we report synthesis, characterization and corrosion inhibition properties of cationic thiol surfactant-capped silver (SC-Ag-NPs) and gold (SC-Au-NPs) nanoparticles. SC-Ag-NPs and SC-Au-NPs were characterized using regular techniques include TEM. Corrosion study was carried out using carbon steel (CS) in 3.5% NaCl aqueous solution and characterized using multiple electrochemical techniques. Our results suggest that the paint containing SC-Ag-NPs and SC-Au-NPs endow efficient corrosion protection to the CS. Especially, SC-Au-NPs based paint form a stronger barrier between the metal and the corrosive ions, leading to better inhibition properties.

Novel Photocatalytic PVDF/Nano-TiO₂ Hollow Fibers for Environmental Remediation

Polyvinylidene difluoride (PVDF) mixed matrix membranes loaded with inorganic TiO₂ nanoparticles have received increasing attention in the last few years as self-cleaning membranes for possible application in wastewater treatment and seawater filtration. These novel membranes show increased hydrophilicity, stability and catalytic activity under UV-A irradiation. In this work, PVDF-TiO₂ hollow fibers were prepared by employing new strategies for enhancing the stability of the TiO₂ dispersion, reducing particle agglomeration and improving their distribution. The spinning conditions for producing ultrafiltration hollow fiber membranes from PVDF material and nano-TiO₂ were investigated. Finally, the optimized fibers have been characterized and tested for methylene blue (MB) degradation in water and salty seawater, revealing good permeability, long-term stability under UV-A irradiation, and photo-catalytic activity in both test solutions.

Interactions of Organics within Hydrated Selective Layer of Reverse Osmosis Desalination Membrane: A Combined Experimental and Computational Study

In this work we have examined a computational approach in predicting the interactions between uncharged organic solutes and polyamide membranes. We used three model organic molecules with identical molecular weights (100.1 g/mol), 4-aminopiperidine, 3,3-dimethyl-2-butanone (pinacolone) and methylisobutyl ketone for which we obtained experimental data on partitioning, diffusion and separation on a typical seawater reverse osmosis (RO) membrane. The interaction energy between the solutes and the membrane phase (fully aromatic polyamide) was computed from molecular dynamics (MD) simulations and the resulting sequence was found to correlate well with the experimental rejections and sorption data. Sorption of the different organic solutes within the membrane skin layer determined from attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) nicely agreed with interaction energies computed from molecular simulations. Qualitative information about solute diffusivity inside the membrane was also extracted from MD simulations while ATR-FTIR experiments indicated strongly hindered diffusion with diffusion coefficients in the membrane about 10^-15 m²/s. The computational approach presented here could be a first step toward predicting rejections trends of, for example, hormones and pharmaceuticals by RO dense membranes.

Biological support media influence the bacterial biofouling community in reverse osmosis water reclamation demonstration plants

The diversity of the bacterial community developed in different stages of two reverse osmosis (RO) water reclamation demonstration plants designed in a wastewater treatment plant (WWTP) in Tarragona (Spain) was characterized by applying 454-pyrosequencing of the 16S rRNA gene. The plants were fed by secondary treated effluent to a conventional pretreatment train prior to the two-pass RO system. Plants differed in the material used in the filtration process, which was sand in one demonstration plant and Scandinavian schists in the second plant. The results showed the presence of a highly diverse and complex community in the biofilms, mainly composed of members of the Betaproteobacteria and Bacteroidetes in all stages, with the presence of some typical wastewater bacteria, suggesting a feed water origin. Community similarities analyses revealed that samples clustered according to filter type, highlighting the critical influence of the biological supporting medium in biofilm community structure.

Effect of chemical oxidation on the sorption tendency of dissolved organic matter to a model hydrophobic surface

The application of chemical oxidants may alter the sorption properties of dissolved organic matter (DOM), such as humic and fulvic acids, proteins, polysaccharides, and lipids, affecting their fate in water treatment processes, including attachment to other organic components, activated carbon, and membranes (e.g., organic fouling). Similar reactions with chlorine (HOCl) and bromine (HOBr) produced at inflammatory sites in vivo affect the fate of biomolecules (e.g., protein aggregation). In this study, quartz crystal microbalance with dissipation monitoring (QCM-D) was used to evaluate changes in the noncovalent interactions of proteins, polysaccharides, fatty acids, and humic and fulvic acids with a model hydrophobic surface as a function of increasing doses of HOCl, HOBr, and ozone (O3). All three oxidants enhanced the sorption tendency of proteins to the hydrophobic surface at low doses but reduced their sorption tendency at high doses. All three oxidants reduced the sorption tendency of polysaccharides and fatty acids to the hydrophobic surface. HOCl and HOBr increased the sorption tendency of humic and fulvic acids to the hydrophobic surface with maxima at moderate doses, while O3 decreased their sorption tendency. The behavior observed with two water samples was similar to that observed with humic and fulvic acids, pointing to the importance of these constituents. For chlorination, the highest sorption tendency to the hydrophobic surface was observed within the range of doses typically applied during water treatment. These results suggest that ozone pretreatment would minimize membrane fouling by DOM, while chlorine pretreatment would promote DOM removal by activated carbon.

Kinetic study of seawater reverse osmosis membrane fouling

Reverse osmosis (RO) membrane fouling is not a static state but a dynamic phenomenon. The investigation of fouling kinetics and dynamics of change in the composition of the foulant mass is essential to elucidate the mechanism of fouling and foulant-foulant interactions. The aim of this work was to study at a lab scale the fouling process with an emphasis on the changes in the relative composition of foulant material as a function of operating time. Fouled membrane samples were collected at 8 h, and 1, 2, and 4 weeks on a lab-scale RO unit operated in recirculation mode. Foulant characterization was performed by CLSM, AFM, ATR-FTIR, pyrolysis GC-MS, and ICP-MS techniques. Moreover, measurement of active biomass and analysis of microbial diversity were performed by ATP analysis and DNA extraction, followed by pyro-sequencing, respectively. A progressive increase in the abundance of almost all the foulant species was observed, but their relative proportion changed over the age of the fouling layer. Microbial population in all the membrane samples was dominated by specific groups/species belonging to Proteobacteria and Actinobacteria phyla; however, similar to abiotic foulant, their relative abundance also changed with the biofilm age.