Comparative Investigation on Photoreactivity and Mechanism of Biogenic and Chemosythetic Ag/C₃N₄ Composites under Visible Light Irradiation

A Ag/C₃N₄ nanocomposite with optimum Ag content is an efficient and green photocatalyst for pollutant degradation under visible light irradiation. In this study, we synthesized Ag NPs using NaBH₄ and the squeezed out liquid (SOL) of plant biomass. The Ag NPs thus obtained have been loaded to C₃N₄ to form Ag/C₃N₄ nanocomposites that show superior photocatalytic performance toward Rhodamine B (RhB) under visible light irradiation. The photocatalytic activity of both biogenic and chemogenic Ag/C₃N₄ nanocomposites with different Ag contents is compared. Results show that the biogenically synthesized Ag/C₃N₄ exhibits better photocatalytic performance than the chemosynthetic composite. Of all the different nanocomposites prepared in this study, Ag₄₈/C₃N₄ (0.048% of Ag content) exhibits excellent photoreactivity, with a reaction rate constant (<i>k</i>) 7-fold higher that the chemosynthetic Ag/C₃N₄. The observed improvement in the photoreactivity is mainly attributed to the high dispersion of Ag NPs on C₃N₄, facilitated by the organic compounds in SOLs. Besides, these organic compounds also enhance the photoreactivity of the catalyst by providing adsorption sited for RhB molecules and by shifting the Fermi level to more negative potential

Preventing the Release of Cu²⁺ and 4‑CP from Contaminated Sediments by Employing a Biochar Capping Treatment

Preventing release of refractory pollutants from contaminated sediments is of growing concern. In situ remediation of sediments becomes more popular because of its low cost and noninterference of benthic ecosystems compared with conventional sediment dredging. In this study, a low-cost rice husk biochar (RHB) was used as a capping material to prevent the release of representative inorganic (Cu²⁺) and organic (4-chlorophenol, 4-CP) pollutants from synthetic contaminated sediments. In addition, the release dynamics of pollutants was investigated under different environmentally relevant conditions. The experimental results indicated that RHB can efficiently suppress the release of Cu²⁺ and 4-chlorophenol from the sediments and a select thickness of RHB can maintain the concentrations of these model pollutants below the national criterion at pH = 5 and 7, even when the concentrations of these pollutants are very high (1600 mg kg^–1 of Cu²⁺ or 100 mg kg^–1 of 4-CP). Fitting the release data of pollutants to the zero order equation, the Elovich equation, the parabolic diffusion law, and the two-constant rate equation demonstrated that a simple model cannot precisely describe the complicated release kinetic process of the pollutants. This study demonstrated a facile remediation application of RHB and helped to provide the information needed for future risk assessments and policy-making

Nitrogen-Doped Porous Carbons Derived from Triarylisocyanurate-Cored Polymers with High CO₂ Adsorption Properties

A series of N-doped porous carbon materials have been successfully prepared by using nitrogen-rich triarylisocyanurate-cored polymers as carbon precursor. The cross-linked networks explain the precursor with high carbonaceous residues in the following carbonization. The influence of KOH dosage and activation temperature on the specific surface area and nitrogen content of the resultant carbon materials is investigated in detail. Eventually, a maximum specific surface area of 2341 m² g^–1 and nitrogen content of 1.7 wt % are achieved in the resultant carbon materials. High CO₂ capacity (30.2 wt % at 273 K/1 bar and 17.2 wt % at 298 K/1 bar) is attributed to abundant microporous structures and basic sites, superior to that of the most porous carbon materials reported in the previous literature. In addition, the carbon materials also demonstrate high H₂ and CH₄ uptake (2.7 wt % at 77.3 K/1.13 bar and 3.8 wt % at 273 K/1.13 bar, respectively). The characters of easy preparation and high gas uptake capacity endow this kind of carbon material with promising applications for CH₄, H₂, and CO₂ uptake

Highly sensitive strain sensor based on composite interference established within S-tapered multimode fiber structure

In this paper, a novel strain sensor based on composite interference established within an S-tapered multimode (STM) fiber structure is proposed and experimentally demonstrated. The STM fibre structure is simply realized by non-axially tapering a traditional single-mode-multimode-single-mode (SMS) fiber into S-shape using a fusion splicer. This fabricated S-tapered structure provides an extra Mach-Zehnder interferometer (MZI) that is introduced within the multimode fibre (MMF) section; therefore, composite interference based on the inherent multimode interference (MMI) of an SMS and the introduced MZI is successfully established. This resultant composite interference greatly enhances the performance of traditional SMS fibre structures for strain sensing, with a maximum strain measurement sensitivity as high as −103.8 pm/με achieved with a detectable strain resolution of 0.2 με. Benefiting from the experimentally determined high sensitivity and good repeatability, this low-cost strain sensor can be realistically applied in many areas where high accuracy strain measurement is required

A humidity sensor based on a singlemode-side polished multimode-singlemode (SSPMS) optical fibre structure coated with gelatin

A novel relative humidity sensor based on a singlemode-side polished multimode-singlemode (SSPMS) fibre structure coated with gelatin material is reported. The sensing principle and fabrication method of the proposed sensor are presented. The experimental method is demonstrated to provide the optimum thickness of coating layers in order to achieve the highest sensitivity of 0.14 dB/%RH and a fast response time of 1000 ms for a given RH sensing range. The developed humidity fibre optic sensor based on a gelatin coating shows great potential for many applications such as industrial production, food processing and environmental monitoring

Simultaneous measurement of displacement and temperature based on a balloon-shaped bent SMF structure incorporating an LPG

A novel optical fiber sensor based on a balloon-shaped bent single-mode (BSBS) fiber structure incorporating a long-period grating (LPG) for simultaneous measurement of displacement and temperature is described and experimentally demonstrated. The sensor is fabricated by splicing a BSBS fiber structure based on a Mach-Zehnder interferometer (MZI) with a long-period grating (LPG). The interference dip formed by the BSBS fiber structure is sensitive to external displacement and temperature variation, while that formed by an LPG only depends on temperature, displacement, and temperature and, therefore, can be unambiguously and simultaneously measured by this sensor. Experimental results show that this sensor offers a high displacement sensitivity of -306 pm/μ m over the displacement range of 0-80 μm and a temperature sensitivity of 42.9 pm/°C over the temperature range of 20-45 °C. Due to its high measurement sensitivities, low cost, and good repeatability, this sensor could be a realistic candidate for applications where displacement and temperature need to be measured simultaneousl

Use of Nutrient Rich Hydrophytes to Create N,P-Dually Doped Porous Carbon with Robust Energy Storage Performance

The optimal strategy for the safe disposal of large amounts of hydrophyte biomass with enriched levels of N and P is challenging. In this study, we proposed and illustrated a facile pyrolysis approach to prepare an N, P-dually doped porous carbon (NPC) material with robust energy storage performance using a thermochemical self-doping process and a widely distributed hydrophyte biomass (<i>Typha angustifolia</i>). As a supercapacitor electrode material for electrochemical energy storage, the NPC shows a maximum capacitance of 257 F g^–1 and energy density of 19.0 Wh kg^–1 and only 3% capacitance loss after 6000 times of cyclic use, which places the NPC among the best porous carbon supercapacitors known previously. Multiple characterizations (BET, SEM, XPS, and Raman) provide evidence that NPC’s excellent energy storage performance involves a pseudocapacitive contribution due to the Faradaic redox reactions of the N and P functional groupsand a capacitive contribution from the formation of the electrical double layer. The external nitrogen resource cannot improve the supercapacitor performance of NPC, suggesting a role for the assimilated nitrogenof plants. In contrast, an external phosphorus resource can significantly increase the specific capacitance from 257 to 375 F g^–1 of NPC. These findings provide useful information for effective energy storage utilization of biomass wastes with differentconcentrations of N and P by fast pyrolysis and activation processes

High sensitivity temperature sensor based on balloon-shaped bent SMF structure with its original polymer coating

A high sensitivity optical fibre temperature sensor is demonstrated based on a balloon-shaped bent single-mode (BSBS) fibre structure where the fibre retains its original protective polymer coating. The BSBS fibre structure can be simply realized by bending a coated straight single-mode fibre into the balloon shape using a section of silica capillary tube. By adjusting the bending radius of the balloon-shaped fibre section, a modal interferometer between the core mode and the coating mode can be effectively implemented at a suitable bending radius. Considering the intrinsically high thermo-optical coefficient and thermal expansion coefficient of the polymer coating, the BSBS fibre structure offers excellent temperature sensing performance. Experimental results show that the temperature sensitivity is as high as  −2465 pm °C−1 with a resolution of 0.008 °C over the temperature range of 20.7 °C–31.7 °C. Based on its simple fabrication process, very low cost, and experimentally determined high sensitivity coupled with good repeatability, the temperature sensor described in this article could be a competitive candidate in many temperature sensing applications

Mesoporous Carbon Stabilized MgO Nanoparticles Synthesized by Pyrolysis of MgCl₂ Preloaded Waste Biomass for Highly Efficient CO₂ Capture

Anthropogenic CO₂ emission makes significant contribution to global climate change and CO₂ capture and storage is a currently a preferred technology to change the trajectory toward irreversible global warming. In this work, we reported a new strategy that the inexhaustible MgCl₂ in seawater and the abundantly available biomass waste can be utilized to prepare mesoporous carbon stabilized MgO nanoparticles (mPC-MgO) for CO₂ capture. The mPC-MgO showed excellent performance in the CO₂ capture process with the maximum capacity of 5.45 mol kg^–1, much higher than many other MgO based CO₂ trappers. The CO₂ capture capacity of the mPC-MgO material kept almost unchanged in 19-run cyclic reuse, and can be regenerated at low temperature. The mechanism for the CO₂ capture by the mPC-MgO was investigated by FTIR and XPS, and the results indicated that the high CO₂ capture capacity and the favorable selectivity of the as-prepared materials were mainly attributed to their special structure (i.e., surface area, functional groups, and the MgO NPs). This work would open up a new pathway to slow down global warming as well as resolve the pollution of waste biomass

Investigation on the Evolution of N‑Containing Organic Compounds during Pyrolysis of Sewage Sludge

Pyrolysis is an emerging technology for the disposal of huge amounts of sewage sludge. However, the thermochemical decomposition mechanism of organic compounds in sludge is still unclear. We adopt a novel online TG-FTIR-MS technology to investigate the pyrolysis of sludge. The sludge samples were pyrolyzed from 150 to 800 °C with heating rates of 10, 50, and 200 K min^–1. We found for the first time that the heating rate of pyrolysis can significantly change the species of liquid organic compounds produced, but cannot change the gaseous species produced under the same conditions. The contents of produced gas and liquid compounds, most of which were produced at 293–383 °C, are influenced by both the heating rate and temperature of pyrolysis. The results also showed that heterocyclic-N, amine-N, and nitrile-N compounds are obtained from the decomposition of N-compounds in sludge, such as pyrrolic-N, protein-N, amine-N, and pyridinic-N. Heterocyclic-N compounds are the dominant N-containing products, which can be due to the thermochemical decomposition of pyridine-N and pyrrole-N, whereas fewer amine-N compounds are produced during the pyrolysis. A mechanism for the decomposition of N-containing compounds in sludge is proposed based on the obtained data