Wavelength-tailored light-emitting diodes reduce damage to sensory properties of light-exposed milk.

Photooxidation has long been affecting nutrient and sensory quality of fluid milk. Light oxidation starts from the activation of photosensitive compounds, followed by generation of singlet oxygen that reacts with vitamins, proteins, and lipids in milk. It is hypothesized that wavelength-tailored light schemes possessing spectral properties capable of avoiding excitation maxima of common photosensitizers in milk could slow the chemical degradation of light-exposed milk and thus preserve consumer acceptability. A series of 6 consumer tests with sample sizes from 95 to 119 participants tested hedonic responses to fluid milk samples exposed to light of varying wavelength spectra. For milk in clear plastic bottles (polyethylene terephthalate or high-density polyethylene), consumer panels generally liked milk exposed to light-emitting diodes eliminating wavelengths below 520 or 560 nm more than standard white light, or those eliminating other wavelength bands. This higher degree of liking coincided with panelists citing fewer off-flavors or aromas from these samples. Taken together, these observations suggest such light schemes can protect milk from light damage to some extent. Wavelength-tailored light schemes used in this study did not offer effective protection for milk in glass bottles. Dissolved oxygen, color, riboflavin loss, and hexanal content were instrumentally evaluated, but results failed to indicate significant signatures of light damage in milk compared with sensory measures. The appearance of milk bottles illuminated by the slightly greenish or yellowish light were less liked by consumers, suggesting further efforts on consumer education may be necessary if these light schemes were to be installed in retail dairy coolers.

A supported dendrimer with terminal symmetric primary amine sites for adsorption of salicylic acid.

The aim of this work is to evaluate the uptake of salicylic acid (SA), an emerging pollutant, using a nano-polar dendrimer containing highly branched terminal symmetric amine groups immobilized on mixed-oxide nanoparticles of SiO2-Al2O3. Several variables, including the effect of initial SA concentration, contact time, temperature, initial pH, adsorbent dosage, interfering ions, and the hydrophobicity of the adsorbent (SANP-G1.0) were studied. Because of the electrostatic and hydrogen bonding interactions between SA and the amine functional sites of the nano-polar dendrimer, the adsorbent featured a remarkable SA uptake capacity of over 254.5 mg/g after 5 min contact time. The solution pH had a considerable impact on SA uptake by SANP-G1.0, with optimal uptake occurring around pH 2-5. Kinetic and isotherm studies confirmed that SA removal could be fit with the Sips and pseudo-second-order kinetic models, respectively, implying that a chemical process dominates SA uptake by the SANP-G1.0. The uptake of SA decreased at elevated temperature, demonstrating that this is a chemically and naturally exothermic process between 15 and 80 °C. The uptake efficiency of the reused nanodendrimer was 54% after the tenth adsorption-desorption cycle. Moreover, the SANP-G1.0 showed a high capacity for adsorbing SA from Cayuga Lake water. We studied the possible mechanism of SA uptake, including the effect of interfering ions, using zeta potential, X-ray photoelectron spectroscopy, infrared spectroscopy, and the hydrophobicity of the nanodendrimer. The prepared supported dendrimer, featuring high chemical and mechanical stability, demonstrates good reusability for SA adsorption from aqueous media. An artificial neural network (ANN) model was also designed to simulate SA uptake by SANP-G1.0. The results revealed an excellent fit between the ANN-modeled and experimental data, with a correlation coefficient (R2) of 0.9841.

Adsorption of mercury ions from wastewater by a hyperbranched and multi-functionalized dendrimer modified mixed-oxides nanoparticles.

In this paper, a novel heterogeneous nanodendrimer with generation of G2.0 was prepared by individual grafting of diethylenetriamine, triazine and l-cysteine methyl ester on the modified aluminum-silicate mixed oxides as a potent adsorbent of Hg(II) ions from aqueous media. The prepared nanodendrimer was characterized by nuclear magnetic resonance spectrum (1H NMR and 13C NMR), Fourier transform infrared spectroscopy (FT-IR), Diffuse reflectance UV-Vis spectroscopy (DR UV-Vis), zeta potential (ζ), inductively coupled plasma atomic emission spectroscopy (ICP-AES), transmission electron microscopy (TEM), scanning electron microscopy (SEM), nitrogen adsorption experiments at -196°C and elemental analysis. Equilibrium and kinetic models for Hg(II) ions removal were used by investigating the effect of the contact time, adsorbent dosage, initial Hg(II) ions concentrations, effect of solution's temperature, interfering ions, and initial pH. The contact time to approach equilibrium for higher removal was 6min (3232mgg-1). The removal of Hg(II) ions has been assessed in terms of pseudo-first- and -second-order kinetics, and the Freundlich, Langmuir and Sips isotherms models have also been applied to the equilibrium removal data. The removal kinetics followed the mechanism of the pseudo-second order equation, where the chemical sorption is the rate-limiting step of removal process and not involving mass transfer in solution, which was further proved by several techniques such as zeta potential, FT-IR and DS UV-vis. The thermodynamic parameters (ΔG, ΔH and ΔS) implied that the removal of mercury ions was feasible, spontaneous and chemically exothermic in nature between 15 and 80°C. The nanodendrimer indicated high reusability due to its high removal ability after 15 adsorption-desorption runs. The adsorption mechanisms of Hg(II) ions onto the nanodendrimer was further studied by diverse techniques such as FTIR, EDS, zeta potential, DR UV-Vis spectroscopy and SEM. The possible mechanism of the Hg(II) ions adsorption onto the nanodendrimer could be carried out through the various paths such as electrostatic interaction, complexation, toxic metal chelation and ionic exchange, which eventually resulted in the hydrolysis and precipitation of the adsorbed Hg(II). The l-cysteine methyl ester nanodendrimer could also remove the mercury ions from the Persian Gulf water even after five times of recycling.

Preparation of iron nanoparticles-loaded Spondias purpurea seed waste as an excellent adsorbent for removal of phosphate from synthetic and natural waters.

The synthesis and characterization of nanoscale zerovalent iron particles (NZVI) supported on Spondias purpurea seed waste (S-NaOH-NZVI) was performed for the adsorption of phosphate (P) ions from waste waters. The effects of various parameters, such as contact time, pH, concentration, reusability and temperature were studied. The adsorption of phosphate ions has been studied in terms of pseudo-first- and -second-order kinetics, and the Freundlich, and Langmuir isotherms models have also been used to the equilibrium adsorption data. The adsorption kinetics followed the mechanism of the pseudo-second-order equation. The thermodynamic parameters (ΔG, ΔH and ΔS) indicated that the adsorption of phosphate ions were feasible, spontaneous and endothermic at 25-80 °C. No significant loss of activity was observed; confirming that the S-NaOH-NZVI has high stability during the adsorption process even after 12th runs. The suggested adsorbent in this paper was also implemented to remove P from the Persian Gulf water. XRD, FTIR and EDX analysis indicated the presence of Fe3 (PO4)2⋅8H2O (vivianite) on the S-NaOH-NZVI@P surface.