Synergistic effect of maghemite and titania nanoparticles in PVA-alginate encapsulated beads for photocatalytic reduction of Pb(II)

In this paper, maghemite (γ-Fe2O3) and titanium oxide (TiO2) nanoparticles were synthesized by hydrothermal and coprecipitation methods, respectively. These nanoparticles were combined together in various ratios (1:10, 1:20, 1:60, 1:80, and 1) and embedded in polyvinyl alcohol (PVA)-alginate beads. These beads were tested for photocatalytic behavior in eliminating toxic Pb(II) from the aqueous solution. The photocatalytic experiments were performed under sunlight irradiation and without sunlight. Several operating conditions such as initial Pb(II) concentration, pH, contact time, and TiO2: γ-Fe2O3 ratios were investigated to evaluate their effect on the process. The recycling attributes of these beads were also investigated. The results revealed that 100% of the Pb(II) was eliminated in 100 min at pH 7 under sunlight when the ratio of TiO2:γ-Fe2O3 was kept to 1. The PVA-alginate maghemite and titania beads showed better efficiency for Pb(II) removal than PVA-alginate titania beads and PVA-alginate maghemite beads. X-ray photoelectron spectroscopy (XPS) analysis also revealed that Pb(II) removal was via photocatalytic reduction due to the presence of Pb(0) in the high-resolution scan at 130–160 eV. Also, the PVA-alginate titania and maghemite beads can be readily isolated from the aqueous solution after the photocatalytic process and reused for at least 6 times without significant losses in their initial properties. The reduction of Pb(II) with PVA-alginate titania and maghemite beads fitted the Langmuir–Hinshelwood (L–H) kinetic model at a correlation coefficient (R2) of 0.9923

Pulsed Eddy Current: Feature Extraction Enabling In-situ Calibration and Improved Estimation for Ferromagnetic Application

Steel pipes in process plant applications are often covered with insulation or weather protection that make inspection di_cult because the additional layers need to be penetrated to inspect the pipes' structure. The pulsed eddy current (PEC) method was devised as a means of inspection through the surface layers. However, the performance of a PEC system is dependent on the electrical and magnetic properties of the pipe material, which are generally unknown. Therefore, the use of a calibration block from a different steel will give inaccurate results. The concept of calibrating using 0 values obtained during inspection has undoubtedly been discussed in the literature. However, no comprehensive work was dedicated to using -1 to carry out calibration on inspected structure. The linear relationship of the -1 feature with the thickness squared, d2, is first established using analytical solutions, and the calibration is carried out using the feature values obtained in air and the reference signal. The performance of this technique is assessed and compared with the conventional 0 technique. Although both features exhibit similar immunity towards lift-off, 0 technique requires normalisation procedure, which contributes to determining more configuration parameters. Experimental results also suggest the relative advantage of using -1 feature in both wall thickness estimation and influences of noises

Photoreduction of Pb(II) ions from aqueous solution by titania polyvinylalcohol–alginate beads

Knowing the photocatalytic reduction of heavy metal ions in waters is of interest and putting this to practical options for improving the environment performance. The purpose of this study was to assess effectiveness of the titania polyvinylalcohol–alginate beads (TPVAABs) as photocatalyst in the removal of Pb(II) ions from aqueous solution, compared to the maghemite polyvinylalcohol–alginate beads (MPVAABs). This study performed the tests of photoreduction of Pb(II) ions by both TPVAABs and TPVAABs in batch experiments. The results showed that the use of TPVAABs could be effective to remove Pb(II) ions from aqueous solution with 98% efficiency after 135 min of reaction time under sunlight irradiation, compared with 98.3% efficiency for the use of MPVAABs. The desorption of Pb(II) ions for the first cycle of adsorption/desorption appeared to be optimal for the TPVAABs recovery. The photocatalytic reduction of Pb(II) ions by TPVAABs can be used repeatedly more than seven cycles of adsorption/desorption. The present study reported photoreduction treatment system to remove Pb(II) ions from aqueous solution by TPVAABs, as well as by MPVAABs, represents a rapid and reliable method to strengthening physicochemical process of treating metal-contaminated wastewater in the future

Mass transfer kinetics of Cd(II) ions adsorption by titania polyvinylalcohol-alginate beads from aqueous solution

Kinetic assessment of the photoreduction of Cd(II) ions in aqueous solution is of interest and thus can most definitely help us make better measures of the scientific concepts to improving the environmental performance. This study showed that the use of titania polyvinylalcohol-alginate beads (TPVA-ABs) as photocatalyst could be effective to remove Cd(II) ions from aqueous solution. The efficiency of Cd(II) ions removal can be expected at 100% for an initial Cd(II) concentration of 50 mg L−1, compared with the efficiencies of 91.2 and 83.6% for the initial Cd(II) concentrations of 100 and 200 mg L−1, respectively, after 3-h reaction time under sunlight irradiation. The desorption capacities of Cd(II) ions in TPVA-ABs were verified for five consecutive cycles of adsorption/desorption to be less than 3% of the reduced Cd(II) ion removal efficiency. Photoreduction of Cd(II) ions by the TPVA-ABs can be used repeatedly at least for five cycles of adsorption/desorption and showed very little loss of its initial properties. The present study scrutinised mass transfer kinetics of Cd(II) ions adsorption by the TPVA-ABs promotes a rapid method to strengthening the adsorption process of treating Cd-contaminated wastewater in the future

Photocatalytic degradation of spilled oil in sea water using maghemite nanoparticles

Maghemite nanoparticles (γ-Fe2O3) were successfully synthesized by co-precipitation method as to remove toluene from sea water. The obtained sample was characterized with X-ray diffraction and transmission electron microscopy which showed that the size of particles was in the average of 9 nm. Further, Fourier transform infrared spectroscopy was performed to ensure successful coating process. The influence of other physico–chemical parameters such sunlight, initial toluene concentrations (5, 10, and 15% V/V), and equilibrium contact time (120 min) were also studied. The results showed that 90% of toluene could be removed within a period of 120 min and the toluene solution with initial concentration of 5 mg/L has shown to have the best removal efficiency

Photocatalyst treatment for lead(II) using titanium oxide nanoparticles embedded in PVA-alginate beads

In this paper, titanium oxide nanoparticles were produced using the hydrothermal method and embedded in PVA–alginate beads to remove Pb(II) ions from aqueous solutions. The kinetics of the photocatalyst process was elucidated by varying operating parameters such as pH (3, 7 and 10) and initial Pb(II) concentrations (25, 50, 100 and 200 mg/L). The findings revealed that 99.1% of the Pb(II) was removed within 150 min and maximum removal occurred in initial concentration of 25 mg/L at pH 7. The titania PVA-alginate beads can be readily isolated from the aqueous solutions after the photocatalytic process and reused for at least seven times without significant loss in their initial properties. In addition, the reduction of Pb(II) from wastewater using titania PVA-alginate beads fitted the Langmuir–Hinshelwood kinetic model with a correlation coefficient (R2) of 0.9931. © 2015 Balaban Desalination Publications