A solar evaporator fabricated from corncob waste for the desalination of seawater and removal of oil/herbicides from contaminated water.

Corncob (CC) based solar evaporators were employed to desalinize seawater brought from the Vallarta coast in Mexico. The pure CC produced an evaporation-rate and evaporation-efficiency of 0.63 kg m-2 h-1 and 38.4%, respectively, under natural solar light. Later, the CC was coated with carbonized CC (CCCE evaporator) or was coated with graphene (CCGE evaporator). Those evaporators were used for the desalination of seawater and obtained higher evaporation rates of 1.59-1.67 kg m-2 h-1, and higher evaporation efficiencies of 92-94% (under natural solar light). The desalination experiments were repeated under artificial solar light and the evaporation-rates/evaporation-efficiencies slightly decreased to 1.43-1.52 kg m-2 h-1/88-92%. The surface analysis of the evaporators by FTIR, XPS and Raman revealed that the CCGE evaporator had on its surface a lower content of defects and a higher amount of OH groups than the CCCE evaporator. Therefore, the CCGE evaporator had higher evaporation-rates/evaporation-efficiencies in comparison with the CCCE evaporator. Furthermore, we purified water contaminated with three different herbicides (fomesafen, 2-6 dichlorobenzamide and 4-chlorophenol at 30 ppm) by evaporation and using natural solar light. Interestingly, the CCCE and CCGE evaporators also removed the herbicides by physical adsorption with efficiencies of 12-22.5%. Moreover, the CCGE evaporator removed vegetable oil from contaminated water by adsorption and its maximum adsorption capacity was 1.72 g/g. Overall, our results demonstrated that the corncob-based evaporators studied here are a low-cost alternative to obtain clean water under natural solar light and this one was more effective for the desalination of seawater than the artificial sunlight (Xe lamp).

Using NIR irradiation and magnetic bismuth ferrite microparticles to accelerate the removal of polystyrene microparticles from the drinking water.

Magnetic bismuth ferrite (BiFO) microparticles were employed for the first time for the removal of polystyrene (PS) nano/microplastics from the drinking water. BiFO is formed by porous agglomerates with sizes of 5-11 µm, while the PS nano/microparticles have sizes in the range of 70-11000 nm. X-ray diffraction studies demonstrated that the BiFO microparticles are composed of BiFeO3/Bi25FeO40 (the content of Bi25FeO40 is ≈ 8.6%). Drinking water was contaminated with PS nano/microparticles (1 g L-1) and BiFO microparticles were also added to the contaminated water. Later, the mixture of PS-particles + BiFO was irradiated with NIR light (980 nm). Consequently, PS nano/microparticles melted on the BiFO microparticles due to the excessive heating on their surface. At the same time, the NIR (near infrared) light generated oxidizing agents (∙OH and h+), which degraded the by-products formed during the photocatalytic degradation of PS nano/microparticles. Subsequently, the NIR irradiation was stopped, and a Neodymium magnet was utilized to separate the BiFO microparticles from the water. This last procedure also permitted the removal of PS nano/microparticles by physical adsorption. Zeta potential measurements demonstrated that the BiFO surface was positively charged, allowing the removal of the negatively charged PS nano/microparticles by electrostatic attraction. The combination of the photocatalytic process and the physical adsorption permitted a complete removal of PS nano/microparticles after only 90 min as well as a high mineralization of by-products (≈95.5% as confirmed by the total organic carbon measurements). We estimate that ≈23.6% of the PS nano/microparticles were eliminated by photocatalysis and the rest of PS particles (≈76.4%) by physical adsorption. An outstanding adsorption capacity of 195.5 mg g-1 was obtained after the magnetic separation of the BiFO microparticles from the water. Hence, the results of this research demonstrated that using photocatalysis + physical-adsorption is a feasible strategy to quickly remove microplastic contaminants from the water.

Morphological and Mechanical Properties of Electrospun Polycaprolactone Scaffolds: Effect of Applied Voltage.

The aim of this work is to investigate the effect of the applied voltage on the morphological and mechanical properties of electrospun polycaprolactone (PCL) scaffolds for potential use in tissue engineering. The morphology of the scaffolds was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and the BET techniques for measuring the surface area and pore volume. Stress-strain curves from tensile tests were obtained for estimating the mechanical properties. Additional studies for detecting changes in the chemical structure of the electrospun PCL scaffolds by Fourier transform infrared were performed, while contact angle and X-ray diffraction analysis were realized for determining the wettability and crystallinity, respectively. The SEM, AFM and BET results demonstrate that the electrospun PCL fibers exhibit morphological changes with the applied voltage. By increasing the applied voltage (10 to 25 kV) a significate influence was observed on the fiber diameter, surface roughness, and pore volume. In addition, tensile strength, elongation, and elastic modulus increase with the applied voltage, the crystalline structure of the fibers remains constant, and the surface area and wetting of the scaffolds diminish. The morphological and mechanical properties show a clear correlation with the applied voltage and can be of great relevance for tissue engineering.

Physicochemical characterization of several types of naturally colored cotton fibers from Peru.

Elemental composition, physical dimensions (length and apparent diameter), and crystallinity of different types of naturally colored cotton (NCCs) fibers from Peru were investigated using a CHNS organic elemental analyzer, optical microscopy and X-Ray Diffraction (XRD). Spectroscopic studies involving Fourier Transform Infrared Spectroscopy and X-Ray photoelectron spectroscopy (XPS) were conducted; and the thermal stability of cotton samples were also investigated. Results from organic elemental analyzer and XPS showed that cotton samples contain mainly carbon, oxygen and hydrogen, but darker color samples also presented nitrogen. It was also found that the white cotton sample exhibited the longest fibers whereas the darker color samples showed the shortest values in length. Interestingly, the crystallinity seems also decrease with color intensity of NCCs. Finally, the thermal stability of white cotton fibers was similar to those obtained for the NCCs.

Dynamics of carbon nanotube alignment by electric fields.

The dynamics of multiwall carbon nanotube (MWCNT) alignment inside viscous media using electric fields is investigated. Electrical current measurements were performed in situ during the application of an electric field to liquid solutions of deionized water or dissolved polymer containing MWCNTs. The variation of electrical current over time was associated to the dynamics of the MWCNT network formation. The influence of the electric field magnitude and frequency on the MWCNT network formation was studied. MWCNT migration towards the negative electrode was observed when a direct current electric field was applied, whereas formation of an aligned MWCNT network was achieved for an alternating current electric field. The increase of the electric field frequency promotes a faster formation of an aligned MWCNT network and thinner MWCNT bundles. A higher viscosity of the liquid medium yields slower MWCNT alignment evidenced by a slower change of electrical current through the viscous system. An analytical model based on the dielectrophoresis-induced torque, which considers the viscosity of the medium, is also proposed to explain the dynamics of MWCNT alignment. Furthermore, aligned MWCNT/polysulfone solid composites were fabricated and electrically characterized. The solid composites presented anisotropic electrical conductivity, which was more evident for low MWCNT concentrations (0.1-0.2 wt%).