Novel activation of peroxymonosulfate by biochar derived from rice husk toward oxidation of organic contaminants in wastewater

In this study, novel activation of peroxymonosulfate (PMS) by biochar derived from rice husk (generally considered useless agricultural wastes in Vietnam) toward organic pollutants from wastewater was investigated. The basic properties of biochar were characterized through field-emission scanning electron microscopy (FE-SEM), elemental analysis (EA) and gas adsorption analysis (BET). Operating parameters including PMS concentration, dose of biochar and initial concentration of target pollutants (tetracycline and bisphenol A) were systematically studied. The results showed that biochar derived from rice husk effectively activated of PMS, leading to high degradation of organic pollutants in wastewater. The degradation efficiency of organic pollutants increased with increasing PMS concentration and amount of biochar. The reuse of rice husk biochar and the possible mechanism for PMS activation were proposed accordingly. In addition, the evaluation of potential available rice husk biomass in Vietnam was discussed. These findings suggest a novel rice husk biochar for activation of PMS toward toxic organic pollutants from wastewater

Selective flotation separation of ABS/PC from ESR plastic wastes mixtures assisted by ultrasonic catalyst/H2O2

The present study investigated the potential recycles of acrylonitile butadiene styrene terpolymers (ABS) from their blends with polymethylmehtacrylate (PMMA), polyCarbonate (PC) and high impact polyStyrene (HIPS) using flotation separation assisted by ultrasonic catalyst/H2O2. The effect of various factors such as H2O2 dose, duty cycle and contact time of the ultrasonication on the recovery rate and purity of ABS/PC were conducted. The results showed that H2O2 dose significantly influenced on the recovery rate of ABS/PC and the optimized H2O2 dose was found at 2%. The recovery rate and the purity of submerged ABS/PC reached 99.5 and 98.6%, respectively, at 300 s of contact time. The duty cycle and the contact time of the ultrasonification also exhibited highly effective for the recycle of ABS/PC from the plastic waste mixtures. The radical scavengers and the mechanism of flotation separation of ABS/PC by ultrasonic catalyst/H2O2 were proposed. Additionally, the economic potential and environmental impacts were discussed. These findings are crucial for flotation separation of ABS/PC from the plastic waste mixtures assisted by ultrasonic catalyst/H2O2 with high recovery rate and purity of ABS/PC in order to produce further value added products as well as reduce the environmental impact of plastic waste. - 2019 Elsevier Ltd.Scopu

Improvement of hydrogen production under solar light using cobalt (II) phosphide hydroxide co-doped g-C3N4 photocatalyst

Graphitic carbon nitride (g-C3N4) has been extensively studied as a model of photocatalyst material for water splitting. This study investigates potential of cobalt (II) phosphide hydroxide co-doped g-C3N4 (Co-P/C3N4) for solar water splitting to produce hydrogen gas as a clean energy source. Characterizations of the materials were done using X-ray diffraction, Scanning Electron Microscopy, X-ray Photoelectron Spectroscopy, and UV–visible spectroscopy (UV–Vis). Under solar light, the hydrogen production rates per hour using Co-P/C3N4 were 386.8 µmol/g which is 14-fold higher than that of g-C3N4 (28.1 µmol/g). The co-doping of cobalt (II) phosphide hydroxide onto g-C3N4 rapidly improved light harvesting capacity and photo-generated charge carrier separation, leading to increase photocatalytic H2 production. In addition, the reusability of Co-P/C3N4 was confirmed by performing the photocatalytic hydrogen production for five cycles. The material consistently produced H2 without any significant loss in hydrogen productivity. Based on these results, Co-P/C3N4 could be utilized as promising photocatalyst material for production of clean energy.This work was supported by Qatar University under Grant Number GCC-2017-007.Scopu

Room-Temperature Lasing Action in GaN Quantum Wells in the Infrared 1.5 ?m Region

Large-scale optoelectronics integration is strongly limited by the lack of efficient light sources, which could be integrated with the silicon complementary metal-oxide-semiconductor (CMOS) technology. Persistent efforts continue to achieve efficient light emission from silicon in extending the silicon technology into fully integrated optoelectronic circuits. Here, we report the realization of room-temperature stimulated emission in the technologically crucial 1.5 ?m wavelength range from Er-doped GaN multiple-quantum wells on silicon and sapphire. Employing the well-acknowledged variable stripe technique, we have demonstrated an optical gain up to 170 cm-1 in the multiple-quantum well structures. The observation of the stimulated emission is accompanied by the characteristic threshold behavior of emission intensity as a function of pump fluence, spectral line width narrowing, and excitation length. The demonstration of room-temperature lasing at the minimum loss window of optical fibers and in the eye-safe wavelength region of 1.5 ?m are highly sought after for use in many applications including defense, industrial processing, communication, medicine, spectroscopy, and imaging. As the synthesis of Er-doped GaN epitaxial layers on silicon and sapphire has been successfully demonstrated, the results laid the foundation for achieving hybrid GaN-Si lasers, providing a new pathway toward full photonic integration for silicon optoelectronics. - 2018 American Chemical Society.N.Q.V. acknowledges the support from NSF (ECCS-1358564). The materials growth effort at TTU was supported by JTO/ ARO (W911NF-12-1-0330)

Improved photocatalytic decomposition of methyl ethyl ketone gas from indoor air environment by using TiO2/graphene oxide

This study investigates the potential application of synthesized TiO2-graphene (Ti/GO) for the decomposition of methyl ethyl ketone (MEKT) in an indoor air environment. XRD and UV-vis studies on the materials confirmed that GO is successfully reduced by TiO2. The effect of various parameters such as catalyst dose, the inlet concentration of MEKT, relative humidity (RH) and gas flowrate were investigated. TiO2-graphene showed greatly improved photocatalytic degradation of the MEKT gas (96.8%) from the indoor air, as compared to commercial TiO2 (32.7%) due to its lower band gap energy, larger specific surface area and the synergistic effect of the graphene nanosheet. The relative humidity was a key factor for the removal of MEKT by photocatalytic oxidation under visible light. The possible photocatalytic mechanism for the removal of MEKT from indoor environments using TiO2-graphene has been discussed in detail. The results are crucial for designing high-performing TiO2-graphene photocatalysts for the degradation of volatile compounds (VOCs) from indoor environments. - 2019 IOP Publishing Ltd.Scopu

Noble metal -doped graphitic carbon nitride photocatalyst for enhancement photocatalytic decomposition of antibiotic pollutant in wastewater under visible light

This study the noble metal (Ag)-doped graphitic carbon nitride (g-C3N4) photocatalyst was synthesized via a facial thermal condensation method. The structure and surface elements distribution of synthesized materials were characterized using XRD, SEM, XPS, UV–vis and N2 adsorption-desorption experiment. The doping of Ag not only decreased the band-gap energy and particle size, but also enhanced the separation of charge carriers and decreased the electron/hole recombination in the g-C3N4 structure. The photocatalytic activity of Ag-doped g-C3N4 was investigated using oxytetracycline (OTC) as a model pollutant. The loading of 7% Ag onto g-C3N4 showed highest photocatalytic degradation efficiency of OT. The synthesized photocatalyst showed extremely high stability after 5 cycles as confirmed through various characterization techniques such as SEM and XRD. Eventually, several degradation intermediates of OTC were identified, and possible decomposition pathways were proposed. The 7-AgCN also was applied for the degradation of complex antibiotic wastewater, the removal efficiencies of OTC within 120 min was 98.7%. Overall, this work provides a novel strategy for the green synthesis of Ag-supportedg-C3N4, and its promising application prospect in environmental remediation.This research is funded by Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 104.05-2018.354 . Appendix AScopu

Ag-doped graphitic carbon nitride photocatalyst with remarkably enhanced photocatalytic activity towards antibiotic in hospital wastewater under solar light

In this study a novel Ag-doped graphitic carbon nitride (g-C3N4) photocatalyst was synthesized and applied as high efficient material under solar light towards emerging antibiotic pollutant in hospital wastewater. The tetracycline (TC) was chosen as a target pollutant and the content of Ag doping at 3 mmol revealed the highest photocatalytic degradation efficiency of TC (96.8%) after 120 min under solar light irradiation. The photoluminescence and UV–vis analysis confirmed the enhancement of charge separation and transfer in the graphitic carbon structure after Ag-doping. The removal efficiency of TC using g-C3N4 and Ag-doped g-C3N4 (AgCN) under dark conditions was only 25.6 and 31.8%, respectively. While under solar light conditions, the removal efficiency of TC increased to 68.3 and 96.8% for g-C3N4 and AgCN, respectively. The reusability process showed that AgCN displayed extremely high stability after 6 cycles without significant drop in antibiotic degradation efficiency. The application of AgCN was tested for treatment of TC from hospital wastewater and it showed high removal efficiency of 89.6% within 120 min reaction time. In addition, the intermediates generated and reduction of total organic carbon (TOC) during the photocatalytic reaction were detected to support information of possible TC removal mechanism.This research is funded by Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 104.05-2018.354 . Appendix AScopu