Enhancement of Physical Characteristics of Styrene-Acrylonitrile Nanofiber Membranes Using Various Post-Treatments for Membrane Distillation.

Insufficient mechanical strength and wide pore size distribution of nanofibrous membranes are the key hindrances for their concrete applications in membrane distillation. In this work, various post-treatment methods such as dilute solvent welding, vapor welding, and cold-/hot-pressing processes were used to enhance the physical properties of styrene-acrylonitrile (SAN) nanofiber membranes fabricated by the modified electrospinning process. The effects of injection rate of welding solution and a working distance during the welding process with air-assisted spraying on characteristics of SAN nanofiber membranes were investigated. The welding process was made less time-consuming by optimizing system parameters of the electroblowing process to simultaneously exploit residual solvents of fibers and hot solvent vapor to reduce exposure time. As a result, the welded SAN membranes showed considerable enhancement in mechanical robustness and membrane integrity with a negligible reduction in surface hydrophobicity. The hot-pressed SAN membranes obtained the highest mechanical strength and smallest mean pore size. The modified SAN membranes were used for the desalination of synthetic seawater in a direct contact membrane distillation (DCMD). As a result, it was found that the modified SAN membranes performed well (>99.9% removal of salts) for desalination of synthetic seawater (35 g/L NaCl) during 30 h operation without membrane wetting. The cold-/hot-pressing processes were able to improve mechanical strength and boost liquid entry pressure (LEP) of water. In contrast, the welding processes were preferred to increase membrane flexibility and permeation.

Corrosion mitigation of mild steel in hydrochloric acid solution using grape seed extract.

Plant extracts have gained a lot of attention due to their ecofriendly nature for corrosion inhibition. In this study, we examined the inhibition performance of grape seed extract as an eco-environmental inhibitor for mild steel in hydrochloric acid medium. Electrochemical impedance spectroscopy, potentiodynamic polarization, and electrochemical noise techniques were employed to study mild steel's electrochemical behavior in the hydrochloric acid solutions containing grape seed extract. Results depicted that grape seed extract could successfully inhibit the corrosion of mild steel. Besides, water droplet contact angle, field-emission scanning electron microscopy coupled with energy dispersive spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy were utilized to study the surface of mild steel specimens after dipping in acidic solutions. Electrochemical impedance results showed a corrosion efficiency of about 88% in 300 ppm of grape seed extract. Also, results revealed more compact corrosion products with improved integrity in the presence of grape seed, which confirmed electrochemical test results.

Fabrication and investigation of silica nanofibers via electrospinning.

Electrospinning is a versatile and cost-effective method for fabricating nanofibers of different materials suitable for various applications. In this work, silica nanofibers have produced using the electrospinning method followed by the heat treatment. To fabricate silica nanofibers, polyvinylpyrrolidone (PVP), tetraethyl orthosilicate (TEOS) and Butanol were used to prepare the dope solutions. The optimized concentration for polymer in the dope solutions was then measured at 0.1 g/ml. The electrospinning process was conducted under the optimum circumstances of voltage, injection flow, tip to collector distance, ambient temperature (25 °C) and the humidity of 47%. Having conducted the thermal analysis (TG/DTA), electrospun fibers were exposed to thermal analysis in three different temperatures of 500, 700, and 1000 °C for 5 h. Following this, the morphology and the diameter of the fibers, as well as the chemical composition and the crystallinity of each sample were analyzed using scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FT-IR), and x-ray diffractometry (XRD), respectively. The noteworthy conditions of 700 °C and 5 h of heat treatment (i.e., calcination) have provided satisfactory results in terms of silica nanofibers morphology and fibers; diameter, i.e., 110 and 600 nm. For cytotoxicity assay, murine fibroblast cells L929 were cultured on a mat of as-spun silica nanofibers. After 24 h and 48 h cultivation time, samples showed no evidence of cytotoxicity effect, which will be a promising result.