Aerated Static Pile Composting for Industrial Biowastes: From Engineering to Microbiology.

This work demonstrated the feasibility of an industrial-scale aerated static pile composting system for treating one of the common biowastes-soybean curd residue. The mixing ratios of the feedstock were optimized to achieve a carbon-nitrogen ratio and a moisture level in the ranges of 25-35 and 60-70%, respectively. This open-air composting system required 6-7 months to obtain a mature compost. Solvita and seed germination tests further confirmed the maturity of the compost, with 25% compost extract concentration yielding the best germination index in the absence of phytotoxicity. The bacterial and fungal compositions of the compost piles were further examined with metagenomic analysis. Thermoactinomyces spp., Oceanobacillus spp., and Kroppenstedtia spp. were among the unique bacteria found, and Diutina rugosa, Thermomyces dupontii, and Candida taylorii were among the unique fungi found in the compost piles, suggesting the presence of good microorganisms for degrading the organic biowastes.

Highly Mesoporous g-C3N4 with Uniform Pore Size Distribution via the Template-Free Method to Enhanced Solar-Driven Tetracycline Degradation.

A highly mesoporous graphitic carbon nitride g-C3N4 (GCN) has been produced by a template-free method and effectively photodegrade tetracycline (TC) antibiotic under solar light irradiation. The mesoporous GCN (GCN-500) greatly improves the photoactivity (0.0247 min-1) by 2.13 times, as compared to that of bulk GCN (0.0116 min-1). The efficiently strengthened photoactivity is ascribed to the high porosity (117.05 m2/g), and improves the optical absorption under visible light (Eg = 2.65 eV) and good charge carrier separation efficiency. The synthesized mesoporous GCN shows a uniform pore size (~3 nm) distribution. GCN-500 shows large pore volume (0.210 cm3/g) compared to GCN-B (0.083 cm3/g). Besides, the GCN-500 also exhibits good recyclability and photostability for TC photodegradation. In conclusion, GCN-500 is a recyclable photocatalyst for the removal of TC under visible light irradiation.

Ultrasound-assisted sequentially precipitated nickel-silica catalysts and its application in the partial hydrogenation of edible oil.

Sequentially precipitated Mg-promoted nickel-silica catalysts with ageing performed under various ultrasonic intensities were employed to study the catalyst performance in the partial hydrogenation of sunflower oil. Results from various characterisation studies showed that increasing ultrasonic intensity caused a higher degree of hydroxycarbonate erosion and suppressed the formation of Ni silicates and silica support, which improved Ni dispersion, BET surface area and catalyst reducibility. Growth of silica clusters on the catalyst aggregates were observed in the absence of ultrasonication, which explained the higher silica and nickel silicate content on the outer surface of the catalyst particle. Application of ultrasound also altered the electron density of the Ni species, which led to higher activity and enhanced product selectivity for sonicated catalysts. The catalyst synthesised with ultrasonic intensity of 20.78 Wcm-2 achieved 22.6% increase in hydrogenation activity, along with 28.5% decrease in trans-C18:1 yield at IV = 70, thus supporting the feasibility of such technique.

The improved photocatalytic activity of highly expanded MoS2 under visible light emitting diodes.

Photocatalytic degradation is a promising method to remove organic pollutants from water. Photocatalysts based on two-dimensional (2D) transition metal dichalcogenides (TMDs) such as MoS2 nanomaterials have gained tremendous popularity. This is due to their narrow band gap and high visible light absorption. Herein, a MoS2 photocatalyst with highly expanded interlayer spaces of 1.51 nm was synthesized in the presence of Pluronic F-127 as a template by a facile one-pot hydrothermal method. This expanded MoS2 (MF-1) managed to photodegrade 98% (2.62 × 10-2 min-1) of methylene blue (MB) dye under irradiation of 1 W visible light-emitting diode (LED) white light. The dominant performance of MF-1 is attributed to the highly expanded interlayer spacing, which exposed more active edge sites. Moreover, the formation of surface defects such as surface cracks and sulfur vacancies (Sv) facilitates the adsorption capacity and in situ generation of reactive oxygen species (ROS). The dominant ROS responsible for the photodegradation of MB is superoxide radical (˙O2 -). The photocatalyst shows good recyclability without deterioration even after five consecutive cycles.

Engineering S. oneidensis for Performance Improvement of Microbial Fuel Cell-a Mini Review.

Microbial fuel cell (MFC) is a promising technology that utilizes exoelectrogens cultivated in the form of biofilm to generate power from various types of sources supplied. A metal-reducing pathway is utilized by these organisms to transfer electrons obtained from the metabolism of substrate from anaerobic respiration extracellularly. A widely established model organism that is capable of extracellular electron transfer (EET) is Shewanella oneidensis. This review highlights the strategies used in the transformation of S. oneidensis and the recent development of MFC in terms of intervention through genetic modifications. S. oneidensis was genetically engineered for several aims including the study on the underlying mechanisms of EET, and the enhancement of power generation and wastewater treating potential when used in an MFC. Through engineering S. oneidensis, genes responsible for EET are identified and strategies on enhancing the EET efficiency are studied. Overexpressing genes related to EET to enhance biofilm formation, mediator biosynthesis, and respiration appears as one of the common approaches.

Biomass-Derived Porous Carbons Derived from Soybean Residues for High Performance Solid State Supercapacitors.

A series of heteroatom-containing porous carbons with high surface area and hierarchical porosity were successfully prepared by hydrothermal, chemical activation, and carbonization processes from soybean residues. The initial concentration of soybean residues has a significant impact on the textural and surface functional properties of the obtained biomass-derived porous carbons (BDPCs). SRAC5 sample with a BET surface area of 1945 m2 g-1 and a wide micro/mesopore size distribution, nitrogen content of 3.8 at %, and oxygen content of 15.8 at % presents the best electrochemical performance, reaching 489 F g-1 at 1 A g-1 in 6 M LiNO3 aqueous solution. A solid-state symmetric supercapacitor (SSC) device delivers a specific capacitance of 123 F g-1 at 1 A g-1 and a high energy density of 68.2 Wh kg-1 at a power density of 1 kW kg-1 with a wide voltage window of 2.0 V and maintains good cycling stability of 89.9% capacitance retention at 2A g-1 (over 5000 cycles). The outstanding electrochemical performances are ascribed to the synergistic effects of the high specific surface area, appropriate pore distribution, favorable heteroatom functional groups, and suitable electrolyte, which facilitates electrical double-layer and pseudocapacitive mechanisms for power and energy storage, respectively.

In-situ DRIFT investigation of photocatalytic reduction and oxidation properties of SiO2@α-Fe2O3 core-shell decorated RGO nanocomposite.

In this work, SiO2@α-Fe2O3 core-shell decorated RGO nanocomposites were prepared via a simple sol-gel method. The nanocomposites were prepared with different weight percentages (10, 30, and 50 wt %) of the SiO2@α-Fe2O3 core-shell on RGO, and the effects on the structural and optical properties were identified. The photocatalytic reduction and oxidation properties of the nanocomposites in the gas phase were assessed through the reduction of CO2 and oxidation of ethanol using in-situ diffuse-reflectance infrared fourier transform spectroscopy (DRIFT). The prepared nanocomposite with (30 wt %) of SiO2@α-Fe2O3 showed superior photocatalytic activity for the gas phase reduction of CO2 and oxidation of ethanol. Enhancement in the activity was also perceived when the light irradiation was coupled with thermal treatment. The DRIFT results for the nanocomposites indicate the active chemical conversion kinetics of the redox catalytic effect in the reduction of CO2 and oxidation of ethanol. Further, the evaluation of photoelectrochemical CO2 reduction performance of nanocomposites was acquired by linear sweep voltammetry (LSV), and the results showed a significant improvement in the onset-potential (-0.58 V) for the RGO (30 wt %)-SiO2@α-Fe2O3 nanocomposite.

Enzymatic pretreatment to enhance anaerobic bioconversion of high strength wastewater to biogas: A review.

Oil and grease, carbohydrate, protein, and lignin are the main constituents of high strength wastewaters such as dairy wastewater, cheese whey wastewater, distillery wastewater, pulp and paper mill wastewater, and slaughterhouse wastewaters. These constituents have contributed to various operational problems faced by the high-rate anaerobic bioreactor (HRAB). During the hydrolysis stage of anaerobic digestion (AD), these constituents can be hydrolyzed. Since hydrolysis is known to be the rate-limiting step of AD, the overall AD can be enhanced by improving the hydrolysis stage. This can be done by introducing pretreatment that targets the degradation of these constituents. This review mainly focuses on the biological pretreatment on various high-strength wastewaters by using different types of enzymes namely lipase, amylase, protease, and ligninolytic enzymes which are responsible for catalyzing the degradation of oil and grease, carbohydrate, protein, and lignin respectively. This review provides a summary of enzymatic systems involved in enhancing the hydrolysis stage and consequently improve biogas production. The results show that the use of enzymes improves the biogas production in the range of 7 to 76%. Though these improvements are highly dependent on the operating conditions of pretreatment and the types of substrates. Therefore, the critical parameters that would affect the effectiveness of pretreatment are also discussed. This review paper will serve as a useful piece of information to those industries that face difficulties in treating their high-strength wastewaters for the appropriate process, equipment selection, and design of an anaerobic enzymatic system. However, more intensive studies on the optimum operating conditions of pretreatment in a larger-scale and synergistic effects between enzymes are necessary to make the enzymatic pretreatment economically feasible.

Entropic Effects in Solvent-Free Bidisperse Polymer Brushes Investigated Using Density Functional Theories.

Solvent-free polymer-functionalized nanoparticles form a special type of colloid composed of inorganic cores self-suspended by their grafted coronas. In the absence of intervening solvent molecules, the fluidity of the system is provided by these tethered polymers as they fill the space. Here, we study the structure and interaction of neighboring polymer-grafted surfaces in the solvent-free condition using mean-field density functional theories. For opposing flat surfaces, the brush configuration and the associated energy landscape are semianalytically investigated given the incompressibility of the tethered entropic chains. The effect of brush polydispersity (including variations in both chain length and surface grafting density) is considered by two bidisperse models corresponding to different physical scenarios: one for opposing brushes uniformly mixed with two species at a fixed grafting density, and the other for opposing brushes with distinct chain lengths and grafting densities. The space-filling capabilities of the neighboring coronas differ not only by their ratio of radii of gyration for the composing polymers but also by their ratio of grafting densities. We show that the system energy depicts a steric repulsion as the brushes are compressed, which is typical for hairy particles in a solvent. However, as the interwall separation increases, the cooperative stretching of the chains leads to an entropic attraction between them, a unique characteristic of solventless systems. The corresponding brush profiles change from a bell-like shape to a more step-function-like feature as the interwall spacing increases significantly. The interwall separation associated with the overall free energy minimum therefore characterizes the favorable interparticle spacing for solvent-free polymer-functionalized particles. The limiting accessible parameter space of polymer sizes and grafting densities subjected to the space-filling constraint is comprehensively explored for representative interparticle spacing characterizing the compressed, relaxed, and stretched regimes for a given polymer species, respectively. Such information would be useful for guiding the design of experimental solvent-free polymer-functionalized nanoparticles.

Adsorptive decontamination of diclofenac by three-dimensional graphene-based adsorbent: Response surface methodology, adsorption equilibrium, kinetic and thermodynamic studies.

Pharmaceutical residues are emerging pollutants in the aquatic environment and their removal by conventional wastewater treatment methods has proven to be ineffective. This research aimed to develop a three-dimensional reduced graphene oxide aerogel (rGOA) for the removal of diclofenac in aqueous solution. The preparation of rGOA involved facile self-assembly of graphene oxide under a reductive environment of L-ascorbic acid. Characterisation of rGOA was performed by Fourier transform infrared, scanning electron microscope, transmission electron microscopy, nitrogen adsorption-desorption, Raman spectroscopy and X-ray diffraction. The developed rGOA had a measured density of 20.39 ±â€¯5.28 mg/cm3, specific surface area of 132.19 m2/g, cumulative pore volume of 0.5388 cm3/g and point of zero charge of 6.3. A study on the simultaneous interactions of independent factors by response surface methodology suggested dosage and initial concentration as the dominant parameters influencing the adsorption of diclofenac. The highest diclofenac adsorption capacity (596.71 mg/g) was achieved at the optimum conditions of 0.25 g/L dosage, 325 mg/L initial concentration, 200 rpm shaking speed and 30 °C temperature. The adsorption equilibrium data were best fitted to the Freundlich model with correlation coefficient (R2) varying from 0.9500 to 0.9802. The adsorption kinetic data were best correlated to the pseudo-first-order model with R2 ranging from 0.8467 to 0.9621. Thermodynamic analysis showed that the process was spontaneous (∆G = - 7.19 to - 0.48 kJ/mol) and exothermic (∆H = - 12.82 to - 2.17 kJ/mol). This research concluded that rGOA is a very promising adsorbent for the remediation of water polluted by diclofenac.

Removal of VOCs from gas streams with double perovskite-type catalysts.

Double perovskite-type catalysts including La2CoMnO6 and La2CuMnO6 are first evaluated for the effectiveness in removing volatile organic compounds (VOCs), and single perovskites (LaCoO3, LaMnO3, and LaCuO3) are also tested for comparison. All perovskites are tested with the gas hourly space velocity (GHSV) of 30,000hr-1, and the temperature range of 100-600°C for C7H8 removal. Experimental results indicate that double perovskites have better activity if compared with single perovskites. Especially, toluene (C7H8) can be completely oxidized to CO2 at 300°C as La2CoMnO6 is applied. Characterization of catalysts indicates that double perovskites own unique surface properties and are of higher amounts of lattice oxygen, leading to higher activity. Additionally, apparent activation energy of 68kJ/mol is calculated using Mars-van Krevelen model for C7H8 oxidation with La2CoMnO6 as catalyst. For durability test, both La2CoMnO6 and La2CuMnO6 maintain high C7H8 removal efficiencies of 100% and 98%, respectively, at 300°C and 30,000hr-1, and they also show good resistance to CO2 (5%) and H2O(g) (5%) of the gas streams tested. For various VOCs including isopropyl alcohol (C3H8O), ethanal (C2H4O), and ethylene (C2H4) tested, as high as 100% efficiency could be achieved with double perovskite-type catalysts operated at 300-350°C, indicating that double perovskites are promising catalysts for VOCs removal.

Degradation of Methylene Blue Dye in the Presence of Visible Light Using SiO2@α-Fe2O3 Nanocomposites Deposited on SnS2 Flowers.

Semiconductor materials have been shown to have good photocatalytic behavior and can be utilized for the photodegradation of organic pollutants. In this work, three-dimensional flower-like SnS2 (tin sulfide) was synthesized by a facile hydrothermal method. Core-shell structured SiO2@α-Fe2O3 nanocomposites were then deposited on the top of the SnS2 flowers. The as-synthesized nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV⁻Vis Spectroscopy, Brunauer⁻Emmett⁻Teller (BET) surface area analysis, and photoluminescence (PL) spectroscopy. The photocatalytic behavior of the SnS2-SiO2@α-Fe2O3 nanocomposites was investigated by observing the degradation of methylene blue (MB). The results show an effective enhancement of photocatalytic activity for the degradation of MB especially for the 15 wt % SiO2@α-Fe2O3 nanocomposites on SnS2 flowers.

The production of an efficient visible light photocatalyst for CO oxidation through the surface plasmonic effect of Ag nanoparticles on SiO2@α-Fe2O3 nanocomposites.

A process for the photo deposition of noble Ag nanoparticles on a core-shell structure of SiO2@α-Fe2O3 nanocomposite spheres was performed to produce a CO photo oxidation catalyst. The structural analyses were carried out for samples produced using different Ag metal nanoparticle weight percentages on SiO2@α-Fe2O3 nanocomposite spheres by X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), UV-vis spectroscopy, Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). A computational study was also performed to confirm the existence of the synergic effect of surface plasmon resonance (SPR) for different weight percentages of Ag on the SiO2@α-Fe2O3 nanocomposites. The mechanism for CO oxidation on the catalyst was explored using diffuse reflectance infrared Fourier transform spectroscopy (DRFIT). The CO oxidation results for the Ag (2 wt%)-SiO2@α-Fe2O3 nanocomposite spheres showed 48% higher photocatalytic activity than α-Fe2O3 and SiO2@α-Fe2O3 at stable temperature.

Electrodeposited Porous Mn1.5Co1.5O4/Ni Composite Electrodes for High-Voltage Asymmetric Supercapacitors.

Mesoporous Mn1.5Co1.5O4 (MCO) spinel films were prepared directly on a conductive nickel (Ni) foam substrate via electrodeposition and an annealing treatment as supercapacitor electrodes. The electrodeposition time markedly influenced the surface morphological, textural, and supercapacitive properties of MCO/Ni electrodes. The (MCO/Ni)-15 min electrode (electrodeposition time: 15 min) exhibited the highest capacitance among three electrodes (electrodeposition times of 7.5, 15, and 30 min, respectively). Further, an asymmetric supercapacitor that utilizes (MCO/Ni)-15 min as a positive electrode, a plasma-treated activated carbon (PAC)/Ni electrode as a negative electrode, and carboxymethyl cellulose-lithium nitrate (LiNO3) gel electrolyte (denoted as (PAC/Ni)//(MCO/Ni)-15 min) was fabricated. In a stable operation window of 2.0 V, the device exhibited an energy density of 27.6 Wh·kg-1 and a power density of 1.01 kW·kg-1 at 1 A·g-1. After 5000 cycles, the specific energy density retention and power density retention were 96% and 92%, respectively, demonstrating exceptional cycling stability. The good supercapacitive performance and excellent stability of the (PAC/Ni)//(MCO/Ni)-15 min device can be ascribed to the hierarchical structure and high surface area of the (MCO/Ni)-15 min electrode, which facilitate lithium ion intercalation and deintercalation at the electrode/electrolyte interface and mitigate volume change during long-term charge/discharge cycling.

The Preparation of Porous Sol-Gel Silica with Metal Organic Framework MIL-101(Cr) by Microwave-Assisted Hydrothermal Method for Adsorption Chillers.

Abstract: Metal organic framework (MOF) of MIL-101(Cr)-Silica (SiO2) composites with highly mesoporous and uniform dispersions were synthesized by a microwave-assisted hydrothermal method followed by the sol-gel technique. Water vapor adsorption experiments were conducted on the MIL-101(Cr)-SiO2 composites for industrial adsorption chiller applications. The effects of MIL-101(Cr)-SiO2 mixing ratios (ranging from 0% to 52%), the surface area and amount of Lewis and Brønsted sites were comprehensively determined through water vapor adsorption experiments and the adsorption mechanism is also explained. The BET and Langmuir results indicate that the adsorption isotherms associated with the various MIL-101(Cr)-SiO2 ratios demonstrated Type I and IV adsorption behavior, due to the mesoporous structure of the MIL-101(Cr)-SiO2. It was observed that the increase in the amount of Lewis and Brønsted sites on the MIL-101(Cr)-SiO2 composites significantly improves the water vapor adsorption efficiency, for greater stability during the water vapor adsorption experiments.

In situ DRIFT and kinetic studies of photocatalytic degradation on benzene vapor with visible-light-driven silver vanadates.

The visible-light active silver vanadates with different types of crystallines (Ag(4)V(2)O(7) and Ag(3)VO(4) phases) were synthesized by an environmentally friendly aqueous process. The parameters of hydrothermal temperature and hydrothermal time were tuned to maximize the photocatalytic efficiency for the decomposition of benzene vapor under visible-light irradiation. The quantum efficiencies of the photocatalysts are compared on the basis of the crystalline phases, surface area, intensity of surface hydroxyl groups, and Brönsted acid sites. From the results of DRIFTS studies, the photocatalytic activities strongly depend on the intensities of the Brönsted acidity and hydroxyl groups presented on the silver vanadates. The sample synthesized at 140 degrees C and 4h (HM140) exhibits the best photocatalytic activity; it has a reaction rate constant (k(app)) of 1.42 min(-1), much higher than that of P25 (k(app)=0.13 min(-1)). For an irradiation time of 720 min, the mineralization yields of benzene were 48% and 11% for HM140 and P25, respectively. Based on the short-term decrease of benzene concentration and the long-term increase of CO(2) concentration, the photocatalytic ability of the HM140 sample is significantly superior to that of P25. The highest activity can be attributed to the synergetic effects of the richest Brönsted acid sites, and a favorable crystalline phase combined with abundant surface hydroxyl groups.