Response surface methodology, based on the four-factor, three-level Box-Behnken design, has been utilized to facilitate a more systematic understanding of the solution and processing parameters of solution blown polyethylene oxide (PEO) micro/nanofibers. The factors investigated include air pressure, solution concentration, nozzle diameter, and injection rate. Fiber diameters, ranging from 137 to 1982 nm, are associated with these variables by applying a response surface model. The linear coefficients of air pressure and solution concentration, the interactive effect between air pressure and injection rate as well as the quadratic terms of nozzle diameter and injection rate are demonstrated statistically significant. Verification of the response surface model is successfully accomplished. Consequently, this study puts forward an overview of the effect of solution and technical parameters on solution blown submicron PEO fibers and provides a train of thought for fabricating other micro/nanofibers.

In this work, we investigated the turbulent airflow field of a solution-blowing annular jet using the computational fluid dynamic approach, captured the fiber flapping motion with a high-speed camera, and then correlated the fiber morphology with the physical quantities of the airflow field and fiber motion. The characteristics of the average flow fields of various nozzle configurations under different air pressures were calculated and compared. The simulations demonstrated that higher air pressure results in higher velocity and turbulent fluctuations. The experiments showed that polymer jet attenuation is due to the effects of stretching, bending instability, flapping motion, and solvent evaporation. The fiber diameters were found to decrease and become more uniform as the air pressure increased. However, the fiber morphology became worse, with the emergence of some fiber strands under even higher air pressures.

Carbon nanotube (CNT) fibers have the potential to serve as continuous nano-fillers for structural and functional composite materials, yet there exists the interfacial problem that has hindered the development of continuous fiber reinforced composites for a long time. Here, a method to overcome this challenge by coating a thick CNT sponge around a single-walled nanotube (SWNT) fiber is presented, and then infiltrating polymers into the sponge to construct a SWNT@polymer coaxial cable. It has been found that the residual stress-induced deposition of amorphous carbon as an intermediate layer between the underlying SWNT fiber and the subsequently coated multiwalled nanotube (MWNT) sponge plays a key role in interfacial properties, and together with well-dispersed CNT in the polymer matrix, a superior interfacial shear strength (>12 MPa), enhanced tensile strength and toughness is achieved. These coaxial cables demonstrate high mechanical damping ability and can serve as stretchable conductors maintaining high electrical conductivity during large-strain cyclic deformation. These results indicate a promising route toward developing continuous CNT fiber-based composites with wide applications as structural and multi-functional composite materials.

In this work, we prepared amidoxime-functionalized polyacrylonitrile (APAN) micro/nanofibers by modifying solution-blown PAN fibers with hydroxylamine hydrochloride, and investigated the adsorption performance of the APAN fibers for Cd(II), Cr(III), Cu(II), Ni(II), Pb(II) and Zn(II) from aqueous solutions. Batch experiments and quantitative analysis were conducted considering initial pH and contact time as controlling parameters. The equilibrium data were better explained by the Langmuir model with maximum adsorption capacities of 185, 204, 105, 104, 345 and 91 mg/g for Cd(II), Cr(III), Cu(II), Ni(II), Pb(II) and Zn(II), respectively. The adsorption kinetics were found to follow the pseudo-second-order kinetic model. The calculated thermodynamic parameters demonstrated that the adsorption of metal ions onto APAN fibers is feasible, spontaneous and endothermic. The five adsorption-desorption cycle experiments showed that APAN micro/nanofiber adsorbent exhibits good reusability, and has a potential application for the removal of heavy metals from wastewater.

In this study, the Box-Benkhen design and response surface method (RSM) were applied to evaluate and optimize the operating variables during the treatment of tetrahydrofuran (THF) wastewater by Fenton process. The four factors investigated were initial pH, Fe(2+) dosage, H2O2 dosage and reaction time. Statistical analysis showed the linear coefficients of the four factors and the interactive coefficients such as initial pH/Fe(2+) dosage, initial pH/H2O2 dosage and Fe(2+) dosage/H2O2 dosage all significantly affected the removal efficiency. The RSM optimization results demonstrated that the chemical oxygen demand (COD) removal efficiency could reach up to 47.8% when initial pH was 4.49, Fe(2+) dosage was 2.52 mM, H2O2 dosage was 20 mM and reaction time was 110.3 min. Simultaneously, the biodegradability increased obviously after the treatment. The main intermediates of 2-hydroxytetrahydrofuran, γ-butyrolactone and 4-hydroxybutanoate were separated and identified and then a simple degradation pathway of THF was proposed. This work indicated that the Fenton process was an efficient and feasible pre-treatment method for THF wastewater.