RESUMEN
The effect of ZnO nanoparticles (ZnO NPs), with different concentrations in simulated water, on the activity of sulfate-reducing bacteria (SRB) and their adhesion behaviour on stainless-steel surfaces, with and without visible light treatment, were investigated. The results showed that the concentration of ZnO NPs and light treatment greatly influenced the antibacterial performance of the NPs. In the water solution without light treatment, the low concentration (no more than 1 mg/L) of ZnO NPs in the aqueous solution promoted the growth of SRB, and the amount of biofilm attached to the stainless-steel surface increased. As the concentration increased, ZnO NPs exhibited antibacterial effects. In water under visible light irradiation, ZnO NPs showed antibacterial performance at all the concentrations studied (0.5~50 mg/L), and the antibacterial efficiency increased with the increase in the concentration of NPs. The determination results of the reactive oxygen species showed that light treatment can stimulate ZnO NPs in water to generate ·OH and O2·-, which exhibited good antibacterial properties. The adhesion amount of SRB on the stainless-steel surface was inversely proportional to the antibacterial efficiency of ZnO NPs.
RESUMEN
The corrosion behavior of brass in TiO2 and Al2O3 nanofluids using a simulated cooling water (SCW) as the base solution and sodium dodecyl benzene sulfonate (SDBS) as the dispersant was studied by electrochemical measurements and surface analysis in this paper. It was found that SDBS could be adsorbed on the brass surface to form a protective film and have a corrosion inhibition effect on brass in SCW. In the SCW-SDBS-TiO2 nanofluid, some negatively charged TiO2 nanoparticles were attached to the brass surface and no obvious SDBS adsorption film was found, and the SDBS in this nanofluid had almost no corrosion inhibition on brass. In the SCW-SDBS-Al2O3 nanofluid, the brass surface was covered by a uniformly distributed SDBS film containing some Al2O3 nanoparticles which were positively charged, and the corrosion inhibition of brass was significantly improved in this nanofluid. It is concluded that the adsorption of SDBS on the brass surface in nanofluids is related to the charge status of the nanoparticles, which makes brass have different corrosion resistance in various nanofluids.
RESUMEN
The effects of Al2O3 nanoparticles on the precipitation behavior of CaCO3 and on the anti-scale performance of 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) in CaCO3 growth solution were studied by means of solution analysis, gravimetric methods, scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. The results illustrate that Al2O3 nanoparticles had little effect on the concentration of calcium ions in the test solution without PBTCA, but significantly changed the form and morphology of calcium carbonate crystals, which were transformed from calcite to aragonite. As a commonly used and effective scale inhibitor, PBTCA showed good Ca2+ retention ability in the test solution, distorting the calcite crystal lattice and promoting the formation of vaterite. When Al2O3 nanoparticles co-existed with PBTCA in the test solution, calcium carbonate was more likely to precipitate, and the Ca2+ retention ability of PBTCA reduced. A newly designed gravimetric method was used to evaluate the scale inhibition performance of Al2O3 nanoparticles on the heat exchange surface. When the concentration of Al2O3 nanoparticles reached 1 g/L, the surface scale inhibition efficiency of Al2O3 nanoparticles exceeded 80%.
RESUMEN
The surface states of brass in simulated cooling water (SCW) containing or free of sodium dodecyl benzene sulfonate (SDBS) and TiO2 nanofluid were analyzed by means of scanning electron microscope (SEM), energy spectrum analysis (EDS) and X-ray diffraction (XRD). The concentrations of Cu and Zn ions in the solution after brass immersion were analyzed using a plasma emission spectrometer. The relationship between the surface states and corrosion resistance of brass was investigated by electrochemical impedance spectroscopy (EIS). The results showed that the brass surface was mainly covered with zinc compound Zn5(OH)6(CO3)2 as corrosion product in SCW. In SCW containing SDBS, a large amount of SDBS was adsorbed on the brass surface. In TiO2 nanofluid, the brass surface was relatively bare and mainly contained cuprous oxide. There was no obvious adhesion of SDBS aggregates and no accumulation of zinc compound on brass surface in TiO2 nanofluid. TiO2 nanoparticles inhibit the adsorption of SDBS on brass surface. Solution analysis results showed that the concentrations of Cu and Zn ions in TiO2 nanofluid was obviously higher than that in SCW and SCW containing SDBS, indicating that most of corrosion products of brass dissolved into the nanofluid. The EIS results illustrated the brass electrode had a larger reaction resistance in SCW containing SDBS, indicating the good protective performance of the adsorbed SDBS film on brass surface. The reaction resistance of the brass electrode was the smallest in TiO2 nanofluid, which illustrated that TiO2 nanoparticles in solution promoted the corrosion of brass.
RESUMEN
The influence of Al2O3 nanoparticles on corrosion inhibition of benzotriazole (BTA) in brass/ simulated water system was studied by potentiodynamic polarization curve and electrochemical impedance spectroscopy (EIS). The results show that BTA has good corrosion inhibition effect on brass. Al2O3 nanoparticles could reduce the corrosion inhibition performance of BTA. The higher the concentration of Al2O3 nanoparticles in simulated water, the lower corrosion inhibition performance of BTA. The isothermal adsorption of BTA on brass surface in simulated water and Al2O3 nanofluids was analyzed. The results indicated that the adsorption of BTA on brass surface followed the Langmuirs' adsorption isotherm, the adsorption Gibbs free energy ΔG was less than -40 kJ/mol, corresponding to chemical adsorption, in both simulated water and Al2O3 nanofluids. The -ΔG value of BTA on brass surface decreased in Al2O3 nanofluids, indicating the weakening of the BTA adsorption on the brass surface. Surface analysis of brass samples by optical microscope and X-ray diffraction confirmed the above results.
RESUMEN
Humic substances (HS) are a major fraction of dissolved organic matters in wastewater. The effect of HS on phosphorus removal by struvite precipitation was investigated using synthetic wastewater under different initial pH values, Mg/P molar ratios and HS concentrations. The composition, morphology and thermal properties of harvested precipitates were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM) and thermo-gravimetric analysis (TGA), respectively. It showed that inhibition effect of HS reached its maximum value of 48.9% at pH 8.0, and decreased to below 10% at pH>9.0. The increase of Mg/P ratio enhanced phosphorus removal efficiency, and thus reduced the influence of HS on struvite precipitation. At pH 9.0, the inhibitory effect of initial HS concentration matched the modified Monod model with half maximum inhibition concentration of 356mgL(-1), and 29% HS was removed in conjunction with struvite crystallisation. XRD analysis revealed that the crystal form of struvite precipitates was changed in the presence of HS. The morphology of harvested struvite was transformed from prismatic to pyramid owing to the coprecipitation of HS on crystal surface. TGA results revealed that the presence of HS could compromise struvite purity.
