Poly(ethylene-co-vinyl alcohol) Functional Nanofiber Membranes for the Removal of Cr(VI) from Water

Abstract

Poly(ethylene-co-vinyl alcohol) (EVOH) nanofibers with average diameter of 260 nm were initially fabricated through the melt-blending extrusion of immiscible blends. The resulting films obtained by layer deposition technology were then functionalized by in situ oxidative polymerization of pyrrole monomer in hydrochloric acid solution for hexavalent chromium [Cr(VI)] adsorption from water. Scanning electron microscopy and Fourier-transform infrared spectroscopy were used to characterize the morphology and structure of functionalized nanofiber membranes. Adsorption experiments were conducted to test the effects of solution pH, dose of adsorbents, water temperature, adsorption contact time, and initial concentration of Cr(VI) and to determine the Cr(VI) adsorption mechanism. The experimental results denoted that the adsorption process was endothermic, spontaneous, and highly pH dependent, and the kinetics data fitted well with a pseudo-second-order model. The adsorption equilibrium time was less than 100 min, and the maximum adsorption capacities were 90.74 mg/g from the adsorption kinetics study. The adsorption isotherm data followed the Langmuir isothermal model. Desorption results exhibited excellent reusability of the membrane for Cr(VI) adsorption.

Mussel‐inspired magnetic adsorbent: Adsorption/reduction treatment for the toxic Cr(VI) from simulated wastewater

“…This result could be explained that the active sites on the surface of the Fe 3 O 4 @PCBA could adsorb Cr(VI) easily and quickly in the original stage. As the extension of time, more and more internal spare adsorption sites are exposed owing to the swell of coated PCBA polymer, and then more and more Cr(VI) ions can diffuse into and interact with the interior of Fe 3 O 4 @PCBA, resulting in the removal amount increasing slowly until adsorption equilibrium . Adsorption of PCBA for Cr(VI) with time going was similar to Fe 3 O 4 @PCBA in the same condition, but adsorption amount of PCBA for Cr(VI) was about 200 mg/g within 6 h which was due to the accumulation of PCBA causing the slow diffusion of Cr(VI) into it.…”

“…As shown in Figure (a), the adsorption ability of Fe 3 O 4 @PCBA for Cr(VI) was significantly decreased with solution pH increasing. Thus, the pH 2.5 was chosen as an optimal condition for the subsequent experiments …”

“…Thus, the pH 2.5 was chosen as an optimal condition for the subsequent experiments. 37,39 In Figure 3(b), the maximum Cr(VI) removal capacity was obtained by using 50 mg of Fe 3 O 4 @PCBA, which gradually decreased with the increase of adsorbent amount. With the weight of Fe 3 O 4 @PCBA increasing, the number of active sites increased while the ratio of Cr(VI) to active sites decreased, leading to unsaturated adsorption and gradually decreased adsorption capacity.…”

Aminated EVOH nanofiber membranes for Cr(vi) adsorption from aqueous solution

“…36 The EVOH resin and CAB were dried at 80 C in a vacuum drying oven for 24 h before experiment. EVOH and CAB were mixed with the weight ratio of 25/75 by the corotating twin-screw extruder (SHJ-20, Nanjing Giant Machinery Co. Ltd) with the melting zone temperature ranging from 190 to 220 C. The blends were extruded by a take-up device, then water-cooled to ambient temperature.…”

Sulfonated poly(arylene ether nitrile)/polypyrrole core/shell nanofibrous mat: an efficient absorbent for the removal of hexavalent chromium from aqueous solution

“…Until now, many technical approaches, including ion exchange, 7,8 electrocoagulation, 9 membrane filtration, [10][11][12] and adsorption [13][14][15][16][17] have been developed for Cr(VI) removal. Among these methods, adsorption has recently become an important technique for removing hexavalent chromium from wastewater, due to its effective removal of heavy metal ions and great flexibility in design and operation.…”