Showing papers in "ACS Sustainable Chemistry & Engineering in 2017"

Ammonia as a Renewable Energy Transportation Media

Abstract: Ammonia synthesized using hydrogen from renewable sources offers a vast potential for the storage as well as transportation of renewable energy from regions with high intensity to regions lean in renewable sources Ammonia can be used as an energy vector for an emissionless energy cycle in a variety of ways Ammonia at the point of end use can be converted to hydrogen for fuel cell vehicles or alternatively utilized directly in solid oxide fuel cells, in an internal combustion engine or a gas turbine One ton of ammonia production requires 9–15 MWh of energy However, its conversion back to useful form or direct utilization can lead to substantial energy losses In this paper, we present an overview of the current processes and technologies for ammonia synthesis and its utilization as an energy carrier We have performed an estimation of the round-trip efficiency of different routes for ammonia utilization at the point of end use along with some sensitivity analysis, and we discuss the outcomes resulting

Amorphous MnO2 Modified Biochar Derived from Aerobically Composted Swine Manure for Adsorption of Pb(II) and Cd(II)

Abstract: This study reports creative preparation of MnO2-biochar (MBR) via MnO2 modification of biochar (BR) derived from aerobically composted swine manure. SEM coupled with EDX analyzer, TEM, XRD, BET, and FT-IR were employed to examine the surface properties and pore structures of MBR and BR. Adsorption experiments of Pb(II) and Cd(II) including isotherms, kinetics, and thermodynamics as well as the influence of pH on zeta-potential were also investigated. The results indicated that MBR showed rougher and larger surface area and pore volume than BR. In batch adsorption, MBR showed superior adsorption performance (maximum capacity for Pb 268.0 mg/g and Cd 45.8 mg/g) to BR (Pb 127.75 and Cd 14.41 mg/g). The adsorption process was pH-dependent, and the removal efficiency reached its maximum at 0.2 g/L dosage of MBR, after which it declined. Finally, X-ray photoelectron spectrometer (XPS) studies indicated the oxidative Mn4+ on MBR, and suggested that apart from electrostatic attachment, specific adsorption (i.e., ...

Phosphorus- and Sulfur-Codoped g-C3N4: Facile Preparation, Mechanism Insight, and Application as Efficient Photocatalyst for Tetracycline and Methyl Orange Degradation under Visible Light Irradiation

Abstract: Phosphorus- and sulfur-codoped graphitic carbon nitride has been successfully synthesized by in situ thermal copolymerization of hexachlorocyclotriphosphazene and thiourea. The phosphorus doping, together with the sulfur doping, would enhance light trapping, surface area, and charge separation, making it serve as a more efficient photocatalyst than its pure g-C3N4 and single-doped g-C3N4 counterpart for the removal of tetracycline (TC) and methyl orange (MO). The optimum photocatalytic activities of a P-, S-codoped g-C3N4 sample for the degradation of TC and MO were about 5.9 times and 7.1 times higher than that of individual g-C3N4, respectively. Furthermore, the optimum TOC removal reached 70.33% and 55.37% for TC and MO within 120 min, respectively. The introduction of a P atom and S atom could significantly change the electronic property of g-C3N4 and suppress the recombination of photogenerated charges. Moreover, the defects in the framework of samples caused by the doping of P and S could serve as c...

Highly Efficient Visible-Light-Induced Photoactivity of Z-Scheme g-C3N4/Ag/MoS2 Ternary Photocatalysts for Organic Pollutant Degradation and Production of Hydrogen

Abstract: A Z-scheme g-C3N4/Ag/MoS2 ternary plasmonic photocatalyst in a flowerlike architecture of diameter about 0.4–0.6 μm is successfully synthesized by a reliable and effective method. The as-synthesized g-C3N4/Ag/MoS2 photocatalyst showed excellent improvement for visible-light absorption and separation efficiency of photoinduced electron–hole pairs. The g-C3N4/Ag/MoS2 system exhibits optimum visible-light-induced photocatalytic activity in degrading Rhodamin B (RhB), which is 9.43-fold and 3.56-fold of Ag/MoS2 and g-C3N4/MoS2 systems, and 8.78-fold and 2.08-fold in the production of hydrogen (H2) out of water, respectively. The excellent photocatalytic activities are attributed to the synergetic effects of Ag, g-C3N4, and MoS2 nanophase structures in the g-C3N4/Ag/MoS2 composites, which result in a Z-scheme-mechanism-assisted fast separation and slow recombination of photoinduced electron–hole pairs and thereby higher photocatalytic activity.

Investigating the Role of Tunable Nitrogen Vacancies in Graphitic Carbon Nitride Nanosheets for Efficient Visible-Light-Driven H2 Evolution and CO2 Reduction

Abstract: Vacancy engineering, that is, self-doping of vacancy in semiconductors, has become a commonly used strategy to tune the photocatalytic performances. However, there still lacks fundamental understanding of the role of the vacancies in semiconductor materials. Herein, the g-C3N4 nanosheets with tunable nitrogen vacancies are prepared as the photocatalysts for H2 evolution and CO2 reduction to CO. On the basis of both experimental investigation and DFT calculations, nitrogen vacancies in g-C3N4 induce the formation of midgap states under the conduction band edge. The position of midgap states becomes deeper with the increasing of nitrogen vacancies. The g-C3N4 nanosheets with the optimized density of nitrogen vacancies display about 18 times and 4 times enhancement for H2 evolution and of CO2 reduction to CO, respectively, as compared to the bulk g-C3N4. This is attributed to the synergistic effects of several factors including (1) nitrogen vacancies cause the excitation of electrons to midgap states below t...

Two-Dimensional Ti3C2Tx MXene Nanosheets for Efficient Copper Removal from Water

Abstract: The performance of two-dimensional (2D) Ti3C2Tx MXene nanosheets in the adsorption and copper removal from aqueous media was investigated. Delaminated (DL)-Ti3C2Tx exhibited excellent Cu removal ability, because of their large specific surface area, hydrophilicity, and unique surface functional properties. Scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM–EDS), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) analyses were performed to analyze the structural changes in Ti3C2Tx MXene and its interaction with Cu ions. Oxygenated moieties in the layered structure of MXene facilitated reductive adsorption of Cu2+ forming Cu2O and CuO species. DL-Ti3C2Tx exhibited a higher and faster Cu uptake, compared to multilayer (ML)-Ti3C2Tx. The maximum experimental adsorption capacity (Qexp,max) was 78.45 mg g–1, and 80% of the total content of metal ions was adsorbed within 1 min. A pseudo-second-order k...

Plasmonic Bi Metal Deposition and g-C3N4 Coating on Bi2WO6 Microspheres for Efficient Visible-Light Photocatalysis

Abstract: A low-cost semiconductor-based photocatalyst using visible light energy has attracted increasing interest for energy generation and environmental remediation. Herein, plasmonic Bi metal was deposited in situ in g-C3N4@Bi2WO6 microspheres via a hydrothermal method. As an electron-conduction bridge, metallic Bi was inserted as the interlayer between g-C3N4 and the surface of Bi2WO6 microspheres to enhance visible light absorption due to the surface plasmon resonance (SPR) effect and facilitate efficient electron-carrier separation. Different characterization techniques, including XRD, SEM, TEM, UV–vis, XPS, photoluminescence, and photocurrent generation, were employed to investigate the morphology and optical properties of the as-prepared samples. The results indicated that the g-C3N4(20%)@Bi@Bi2WO6 microsphere sample exhibited an extraordinary enhanced photocatalytic activity, higher than those of the g-C3N4, Bi2WO6, and g-C3N4(20%)@Bi2WO6 samples. It implies that the heterostructured combination of g-C3N4...

Sustainable Recovery of Cathode Materials from Spent Lithium-Ion Batteries Using Lactic Acid Leaching System

Abstract: An environmentally friendly leaching process for recycling valuable metals from spent lithium-ion batteries is developed. A sol–gel method is utilized to resynthesize LiNi1/3Co1/3Mn1/3O2 from the leachate. Lactic acid is chosen as a leaching and chelating agent. The leaching efficiency is investigated by determining the contents of metal elements such as Li, Ni, Co, and Mn in the leachate using inductively coupled plasma optical emission spectroscopy. The spent cathode materials for the pretreatment process and the regenerated and freshly synthesized materials are examined using X-ray diffraction and scanning electronic microscopy. The results show that the leaching efficiencies of Li, Ni, Co, and Mn reached 97.7, 98.2, 98.9, and 98.4%, respectively. The optimum conditions are lactic acid concentration of 1.5 mol L–1, solid/liquid ratio of 20 g L–1, leaching temperature of 70 °C, H2O2 content of 0.5 vol %, and reaction time of 20 min. The leaching kinetics of cathode scrap in lactic acid fit well to the A...

Lignin Nanoparticle as a Novel Green Carrier for the Efficient Delivery of Resveratrol

Abstract: In this work, we have developed a novel green nanoparticle platform based on lignin without chemical modification. The alkali lignin (AL) was used to prepare nanoparticles with perfect spheres and well dispersibility via a simple self-assembly method by adding water to a methanol solution of AL. Finally, we showed that self-assembly of AL with the bioactive molecule resveratrol (RSV) and Fe3O4 magnetic nanoparticles led to the formation of stable nanodrug carrier. In cytological and animal tests, the magnetic RSV-loaded lignin nanoparticles (AL/RSV/Fe3O4 NPs) demonstrated good anticancer effects and enhanced in vitro RSV release and stability, drug accumulation, and better tumor reduction, as well lower adverse effects than free drugs, strongly supporting the AL NPs application as a new and highly efficient nanodelivery. Moreover, this renewable green material with its simple preparation technique and easy large-scale production would be a highly potential candidate for many poorly soluble drugs.

Cellulose-Lignin Biodegradable and Flexible UV Protection Film

Abstract: There is significant interest in biodegradable and transparent UV protection films from renewable resources for many different applications. Herein, the preparation and characterization of semitransparent flexible cellulose films containing low amounts of covalently bonded lignin with UV-blocking properties are described. Azide modified cellulose dissolved in dimethylacetamide/lithium chloride (DMAc/LiCl) was reacted with propargylated lignin to produce 0.5%, 1%, and 2% by weight lignin containing materials. Cellulose-lignin films were prepared by regeneration in acetone. These covalently bonded cellulose-lignin films were homogeneous, unlike the simple blends of cellulose and lignin. Prepared films showed high UV protection ability. Cellulose film containing 2% lignin showed 100% protection of UV-B (280–320 nm) and more than 90% of UV-A (320–400 nm). The UV protection of prepared films was persistent when exposed to thermal treatment at 120 °C and UV irradiation. Thermogravimetric analysis of the films s...

Recovery of Lithium, Nickel, Cobalt, and Manganese from Spent Lithium-Ion Batteries Using l-Tartaric Acid as a Leachant

Abstract: Herein is reported a novel green process involving natural l-tartaric acid leaching, developed for the sustainable recovery of Mn, Li, Co, and Ni from spent lithium-ion batteries (LIBs). Operating conditions affecting the leaching efficiencies of Mn, Li, Co, and Ni, including the concentrations of l-tartaric acid (C4H6O6) and hydrogen peroxide (H2O2), pulp density, temperature, and leaching time, were investigated. The leaching efficiencies were 99.31% for Mn, 99.07% for Li, 98.64% for Co, and 99.31% for Ni under the optimized conditions (4 vol% H2O2, 2 M l-tartaric acid, 17 g/L pulp density, 70 °C, and 30 min). The leaching mechanism was studied preliminarily based on the structure of l-tartaric acid. The kinetics data for the leaching of Mn, Li, Co, and Ni fit best to the shrinking-core model of chemical control. For the first stage, the activation energies (Eas) for the leaching of Mn, Li, Co, and Ni were 66.00, 54.03, 58.18, and 73.28 kJ/mol, respectively. For the second stage, the Eas for the leachin...

Review on the Aerogel-Type Oil Sorbents Derived from Nanocellulose

Abstract: Because of the severe risk of oil pollution and increasing concerns about the sustainability of sorbent materials, there are considerable interests across the world to develop cost-effective, reusable, and environmentally friendly oil sorbents derived from renewable resources. Nanocellulose is a new family of promising cellulosic materials with a cellulose fibril width in the order of nanometer range (i.e., 2–100 nm). As a class of newly developed cellulose aerogels, nanocellulose-derived ones combine intriguing interconnected three-dimensional porous characteristics of aerogel-type materials such as high porosity, large surface area, and low density with fascinating advantages related to naturally occurring nanocellulose: impressive mechanical properties, abundant sources, natural renewability, excellent biodegradability, and ease to surface modification. Therefore, nanocellulose-based aerogels are very ideal “green” oil sorbents after either appropriate hydrophobic modifications or carbonization. This p...

Graphene Quantum Dots from Mangifera indica: Application in Near-Infrared Bioimaging and Intracellular Nanothermometry

Abstract: We report a simple one-pot microwave-assisted green-synthesis route for the fabrication of bright red-luminescent graphene quantum dots (GQDs) using ethanolic extracts of Mangifera indica (mango) leaves, hence addressing them as mGQDs. The mGQDs were quantum-sized ranging from 2 to 8 nm and exhibited excitation-independent fluorescence emission in the near-infrared (NIR) region between 650 and 750 nm. The mGQDs showed defects in their structure and were highly crystalline in nature as confirmed by Raman spectroscopy and powdered X-ray diffraction analysis, respectively. These mGQDs showed 100% cellular uptake and excellent biocompatibility on L929 cells even at high concentration (0.1 mg/mL) 24 h post-treatment. Cell cycle analysis showed increased proliferation in L929 cells upon mGQDs treatment. Furthermore, the mGQDs were demonstrated as NIR-responsive fluorescent bioimaging probes, self-localizing themselves selectively in the cell cytoplasm. Also, the temperature-dependent fluorescence intensity of t...

Plasmon-Enhanced Photoelectrochemical Water Splitting on Gold Nanoparticle Decorated ZnO/CdS Nanotube Arrays

Abstract: The design and decoration of plasmonic metal hybrid photoanodes provide an effective strategy for highly efficient photoelectrochemical (PEC) water splitting. In this work, an Au nanoparticle (NP) decorated highly ordered ZnO/CdS nanotube arrays (ZnO/CdS/Au NTAs) photoanode has been rationally designed and successfully synthesized. By virtue of the favorable band alignment and specific nanotube structure of ZnO/CdS as well as the surface plasmonic effect of Au NPs, the ZnO/CdS/Au NTAs photoanode shows significantly enhanced PEC performance as compared to the ZnO/CdS/Au and ZnO/CdS nanorod arrays (NRAs). Impressively, the optimized ZnO/CdS/Au NTAs photoanode exhibits the highest photocurrent density of 21.53 mA/cm2 at 1.2 V vs Ag/AgCl and 3.45% photoconversion efficiency (PCE) among the parallel photoanodes under visible light illumination (λ > 420 nm).

Construction of Pillared-Layer MOF as Efficient Visible-Light Photocatalysts for Aqueous Cr(VI) Reduction and Dye Degradation

Abstract: By using a controllable pillared-layer method, a novel visible-light responsive metal–organic framework (MOF) photocatalyst NNU-36 has been rationally constructed. The synthesized NNU-36 is of broad-range visible light absorption and good chemical stability which are beneficial to its application of photocatalysis. Photocatalytic experiments reveal that NNU-36 is highly efficient for Cr(VI) reduction and dye degradation in aqueous solution under visible light irradiation. Control experiments show that the pH value is vital for Cr(VI) reaction, and meanwhile, the use of hole scavenger of methanol promotes the photocatalytic reduction significantly. It has been also demonstrated that NNU-36 is efficient for dye degradation, in which the introduction of hydrogen peroxide (H2O2) significantly enhances the photocatalytic efficiency of dye degradation. This study illustrates that the introduction of hole scavengers or oxidants in the MOF-mediated photocatalytic reaction is a feasible approach to enhance the cat...

Protonation of Graphitic Carbon Nitride (g-C3N4) for an Electrostatically Self-Assembling Carbon@g-C3N4 Core–Shell Nanostructure toward High Hydrogen Evolution

Abstract: The development of new, appealing metal-free photocatalysts is of great significance for photocatalytic hydrogen evolution. Herein, an electrostatic self-assembly method to form a unique core–shell architecture of a colloid of carbon spheres with graphitic carbon nitride (g-C3N4) has been developed by a one-step chemical solution route. The chemical protonation of g-C3N4 solids with strong oxidizing acids (such as HNO3) is an efficient pathway toward the sol procedure of stable carbon nitride colloids, which can cover the surface of carbon spheres via electrostatic adsorption. On account of the unique polymeric matrix of g-C3N4 and reversible hydrogen bonding, the carbon@g-C3N4 derived from the sol solution showed high mechanical stability with broadened light absorption and enhanced conductivity for charge transport. Thus, the carbon@g-C3N4 core–shell structure exhibited remarkably enhanced photoelectrochemical performance. This polymer system is envisaged to hybridize with desirable functionalities (suc...

N-Doped Graphene from Metal–Organic Frameworks for Catalytic Oxidation of p-Hydroxylbenzoic Acid: N-Functionality and Mechanism

Abstract: N-doped graphene has been considered as a promising catalyst with surface metal-free active sites for environmental remediation. Several MIL-100 (Fe)-templated N-doped graphene samples were synthesized using dicyandiamide, melamine, and urea as the nitrogen precursors. Excellent catalytic oxidation of p-hydroxylbenzoic acid (PHBA) was observed on the as-synthesized samples via peroxymonosulfate (PMS) activation. The mechanism was investigated by both electron paramagnetic resonance (EPR, 5,5-dimethyl-1-pyrroline N-oxide and 2,2,6,6-tetramethyl-4-piperidinol as the trapping agents) and quenching tests (ethanol and sodium azide as the radical scavengers). Benzoic acid and furfuryl alcohol were also employed as probing reagents for hydroxyl/sulfate radicals and singlet oxygen, respectively. The results confirmed that singlet oxygen was generated and dominated the PHBA degradation on N-doped graphene, rather than hydroxyl/sulfate radicals. With the novel N-doped graphene, this study illustrates the formation ...

Electrochemical Synthesis of NH3 at Low Temperature and Atmospheric Pressure Using a γ-Fe2O3 Catalyst

Abstract: The electrochemical synthesis of NH3 by the nitrogen reduction reaction (NRR) at low temperature (<65 °C) and atmospheric pressure using nanosized γ-Fe2O3 electrocatalysts were demonstrated. The activity and selectivity of the catalyst was investigated both in a 0.1 M KOH electrolyte and when incorporated into an anion-exchange membrane electrode assembly (MEA). In a half-reaction experiment conducted in a KOH electrolyte, the γ-Fe2O3 electrode presented a faradaic efficiency of 1.9% and a weight-normalized activity of 12.5 nmol h–1 mg–1 at 0.0 VRHE. However, the selectivity toward N2 reduction decreased at more negative potentials owing to the competing proton reduction reaction. When the γ-Fe2O3 nanoparticles were coated onto porous carbon paper to form an electrode for a MEA, their weight-normalized activity for N2 reduction was found to increase dramatically to 55.9 nmol h–1 mg–1. However, the weight- and area-normalized N2 reduction activities of γ-Fe2O3 decreased progressively from 35.9 to 14.8 nmol...

Bioinspired Polydopamine Sheathed Nanofibers Containing Carboxylate Graphene Oxide Nanosheet for High-Efficient Dyes Scavenger

Abstract: New hierarchical bioinspired nanocomposite materials of poly(vinyl alcohol)/poly(acrylic acid)/carboxylate graphene oxide nanosheet@polydopamine (PVA/PAA/GO-COOH@PDA) were successfully prepared by electrospinning technique, thermal treatment, and polydopamine modification. The obtained composite membranes are composed of polymeric nanofibers with carboxylate graphene oxide nanosheets, which are anchored on the fibers by heat-induced cross-linking reaction. The preparation process demonstrate eco-friendly and controllable manner. These as-formed nanocomposites were characterized by various morphological methods and spectral techniques. Due to the unique polydopamine and graphene oxide containing structures in composites, the as-obtained composite demonstrate well efficient adsorption capacity toward dye removal, which is primarily due to the specific surface area of electrospun membranes and the active polydopamine/graphene oxide components. In addition, the composite membranes reported here are easy to re...

Green Synthesis of Fe3O4/RGO Nanocomposite with Enhanced Photocatalytic Performance for Cr(VI) Reduction, Phenol Degradation, and Antibacterial Activity

Abstract: Herein, we report a novel single-step hydrothermal synthesis of a photocatalytically stable and magnetically separable g-Fe3O4/RGO nanocomposite in the presence of Averrhoa carambola leaf extract as a natural surfactant for multipurpose water purification application. The Averrhoa carambola leaf extract played a major role in the modification of structural, optical, and electronic properties of the Fe3O4 nanoparticle. At room temperature, the g-Fe3O4/2RGO nanocomposite showed 97% and 76% of Cr(VI) reduction and phenol degradation, respectively. The higher activity of g-Fe3O4/2RGO was attributed to the in situ loading of RGO, and the synergism developed between RGO and the super magnetic Fe3O4 nanoparticle results in better separation of photoexcited charge carriers (e–/h+) which was concluded from photoluminescence and photocurrent measurements. Further, the g-Fe3O4/2RGO nanocomposite showed better antimicrobial activity against three bacterial pathogens such as Staphylococcus aureous (MTCC-737), Bacillus...

A Review of Clathrate Hydrate Nucleation

Abstract: Clathrate hydrates are crucial from the point of view of flow assurance and future energy resources, as well as potential innovative and sustainable applications such as gas separation, CO2 sequestration, district and data center cooling, seawater desalination, and natural gas storage. Although proof of concept has been demonstrated, significant progress is necessary in order to achieve industrial-level validation and commercialization. Most of the applications possess a common requirement of enhanced kinetics in formation and dissociation. There is a need for a broader understanding of hydrate nucleation mechanisms, cause-effect relations, and investigation techniques. The stochastic nature of hydrate nucleation, confounding cause–effect relations, and spatial-temporal scales have made it even more challenging to study nucleation. The use of hydrate promoters, novel reactor configurations such as porous media in a packed bed, and nanoparticles and hydrogels necessitates us to obtain further insights abou...

Antibacterial Activity of Graphene Oxide/g-C3N4 Composite through Photocatalytic Disinfection under Visible Light

Abstract: Carbon-based nanomaterials have been widely developed into innovative antimicrobial agents due to their advantages of high surface-to-volume ratio, extremely high mechanical strength, and distinct physicochemical properties. Here, the nanocomposite of graphene oxide/graphitic carbon nitride (GO/g-C3N4), a free-metal photocatalyst, was fabricated through sonication at room temperature and its antibacterial activity against Escherichia coli (E. coli) was investigated. The 100 μg/mL GO/g-C3N4 composite was found to kill 97.9% of E. coli after 120 min visible light irradiation, which was further confirmed by fluorescent-based cell membrane integrity assay. Additionally, the holes produced by photocatalysis were confirmed by electron spin resonance (ESR) spectra and trapping experiments to participate in photocatalytic sterilization as principal active species and were further verified by transmission electron microscopy (TEM) and scanning electron microscope (SEM) to lead to the distortion and rupture of cell...

Accessible Graphene Aerogel for Efficiently Harvesting Solar Energy

Abstract: Solar steam generation through heat localization is a new approach to efficiently utilize solar energy. Nanocomposites with noble metals and other porous materials have been employed to generate solar vapor at a high light intensity. However, large-scale applications of the nanocomposites based on noble metals are restricted due to their high cost, complex preparation, and low recycling stability. Herein, we report a simple method toward fabricating graphene aerogel (GA) from graphene oxides only by photoreduction, which is for the first time used to harvest solar energy. GA can not only convert almost the entire incident solar light to heat energy but can also self-float on the surface of water and pump the interface water forming a constant water steam. Solar steam generation efficiencies of 53.6 ± 2.5% and 82.7 ± 2.5% are achieved at light intensities of 1 and 10 kW m–2, respectively. Furthermore, this efficiency is still kept at a high value, and the morphology of GA is hardly broken after 10 cycles o...

Development of a Lower Toxic Approach Based on Green Synthesis of Water-Compatible Molecularly Imprinted Nanoparticles for the Extraction of Hydrochlorothiazide from Human Urine

Abstract: In the present paper, one-pot green syntheses of novel hydrophilic and superparamagnetic molecularly imprinted polymers (MMIPs) for the cleanup and extraction of hydrochlorothiazide (HCT) in human urine are described. The MMIPs were prepared via a sol–gel process using Fe3O4 magnetite as a magnetic component, HCT as a template, tetraethyl orthosilicate (TEOS) as the cross-linker, and 3-aminopropyl trimethoxysilane (APTMS) as the functionalized monomer, which could simplify the imprinting process. During the synthesis process, a surfactant was especially used to graft the silica-imprinted nanoparticles. The key step of this research is mild working temperature without consuming any organic solvent during the synthesis of MMIPs in addition to its ability for efficient and highly selective enrichment of HCT in complicated human urine. The morphology, structure, and magnetic properties of the MMIPs were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier tra...

Fabricating the Robust g-C3N4 Nanosheets/Carbons/NiS Multiple Heterojunctions for Enhanced Photocatalytic H2 Generation: An Insight into the Trifunctional Roles of Nanocarbons

Abstract: In this work, robust nanocarbons, including graphite (G), carbon nanotube (CNT), reduced graphene oxide (rGO), carbon black (CB), and acetylene black (AB), have been successfully coupled into the interfaces between g-C3N4 and NiS using a facile precipitation method. The results demonstrated that nanocarbons played trifunctional roles in boosting the photocatalytic H2 evolution over g-C3N4, which can not only act as effective H2-evolution co-catalysts but can also serve as conductive electron bridges to collect photogenerated electrons and boost the H2-evolution kinetics over the NiS co-catalysts. More interestingly, the nanocarbons can also result in the downshift of valence band of g-C3N4, thus facilitating the fast oxidation of triethanolamine and charge-carrier separation. Particularly, in all five ternary multiheterostructured systems, the g-C3N4-0.5%CB-1.0%NiS (weight ratio) and g-C3N4-0.5%AB-1.0%NiS photocatalysts exhibited the highest H2-evolution rates of 366.4 and 297.7 μmol g–1 h–1, which are 3....

Cr(VI) Reduction and Immobilization by Core-Double-Shell Structured Magnetic Polydopamine@Zeolitic Idazolate Frameworks-8 Microspheres

Abstract: A well-defined core-double-shell structured magnetic polydopamine@zeolitic idazolate frameworks-8 (MP@ZIF-8) hydrid microsphere consisting of the core of magnetic Fe3O4 nanoparticles, the inner shell of a polydopamine layer, and the outer shell of a porous ZIF-8 nanocrystal was prepared through a facile and green approach to achieve synergistic reduction and adsorptive removal of Cr(VI). The microsphere property was characterized methodically. The batch adsorption experiments showed that the MP@ZIF-8 exhibited high efficiency in the Cr(VI) removal from aqueous solutions, affording Cr(VI) removal capacity of 136.56 mg g–1, surpassing pristine MP (92.27 mg g–1). The pseudo-second-order model fitted the Cr(VI) removal kinetics well. Cr(VI) removal on the MP@ZIF-8 relied highly on pH values. More significantly, with the reduction of nitrogen atom group on ZIF-8 and PDA, Cr(VI) was easily converted into low toxicity Cr(III) and then immobilized on the MP@ZIF-8. Thus, the hybrid microspheres provided excellent ...

Fabrication of SnO2 Nanopaticles/BiOI n–p Heterostructure for Wider Spectrum Visible-Light Photocatalytic Degradation of Antibiotic Oxytetracycline Hydrochloride

Abstract: In this work, n–p heterostructure SnO2/BiOI photocatalyst was successfully fabricated through a facile chemical bath method. The photocatalysts was applied to minimize antibiotic oxytetracycline hydrochloride (OTTCH) and methyl orange (MO) under visible light irradiation. SnO2/BiOI composite exhibited excellent photocatalytic performance for the refractory pollutant OTTCH and MO decomposition. The sample of 30 wt % SnO2/BiOI possessed the best photocatalytic performance in all the obtained catalysts. Several reaction parameters affecting OTTCH degradation such as initial concentration, ion species, and concentration were investigated systematically. The optical and electrical properties of materials demonstrate that the transfer rate of electron–hole pairs dramatically improve though forming an n–p junction in SnO2/BiOI hybrid. Moreover, the energy band alignments of SnO2/BiOI junction were confirmed via combining DRS and XPS analysis, which provided strong support for the proposed mechanism. This work co...

Z-Scheme BiOCl-Au-CdS Heterostructure with Enhanced Sunlight-Driven Photocatalytic Activity in Degrading Water Dyes and Antibiotics

Abstract: Although semiconductor photocatalysis has made great progresses as a promising solution to solve the problem of environmental pollution, the highly efficient decomposition of organic pollutants driven by sunlight is still a challenge. Herein, we successfully constructed a Z-scheme photocatalyst BiOCl-Au-CdS for the first time by stepwise deposition of Au and CdS. It was found that the Au nanoparticles (NPs) were selectively anchored on the {001} facets of BiOCl nanosheets in the process of photoreduction while CdS NPs were further in situ deposited on Au NPs via the strong S–Au interaction. Compared to BiOCl, BiOCl-Au, and BiOCl-CdS, the Z-scheme BiOCl-Au-CdS exhibited evidently higher sunlight-driven photocatalytic activity toward the degradations of anionic dye Methyl Orange, cationic dye Rhodamine B, colorless pollutant phenol, and antibiotic sulfadiazine. The radical trapping experiments indicated that ·OH, h+, and ·O2– are the main reactive species responsible for the degradations of organic pollutan...

Magnetic Porous Carbonaceous Material Produced from Tea Waste for Efficient Removal of As(V), Cr(VI), Humic Acid, and Dyes

Abstract: Magnetic porous carbonaceous (MPC) materials derived from tea waste were synthesized by an integrated biosorption–pyrolysis process and were applied as adsorbents for wastewater cleanup. On the basis of various characterizations, we demonstrated that the formation mechanism of γ-Fe2O3 anchored on the porous carbonaceous material surface consisted of the adsorption of iron ions and then the γ-Fe2O3 nucleation and growth through pyrolysis at alternative peak temperatures (300–500 °C). The sample pyrolyzed at 300 °C (MPC-300) showed good capacities for As(V) (38.03 mg g–1) and Cr(VI) (21.23 mg g–1) adsorption, outperforming that of commercial bulk Fe2O3 and many other materials. Moreover, the large available positive charge density can facilitate the effective adsorption of anionic dye (MO) and humic acid (HA) on the γ-Fe2O3 surface while the adsorption performance is sluggish for cationic dyes (MB and RhB). Relatively, the adsorption isotherms could significantly conform to the Langmuir model, and the pseud...

Toward Sustainability for Recovery of Critical Metals from Electronic Waste: The Hydrochemistry Processes

Abstract: Critical metals are significantly important in the preparation of high-tech materials associated with applications on, e.g., renewable energy, sustainable materials engineering and cleaner production. This importance together with supply risk to a substantial extent within the European Union (EU) has pushed their recovery from waste being highlighted. Electronic waste, usually from end-of-life electronic products, is a notable secondary resource for this purpose because of its distinctive features. A range of critical metals, including rare-earth metals, indium, cobalt and valuable metals, such as copper, silver and gold, are possibly recovered from electronic waste. On top of the current practices of electronic waste recycling, it requires innovations on technology and breakthroughs on process design in order to promote critical metal recovery or electronic waste treatment (in general) to be green and sustainable. Significant potentials are more and more noticed from hydrochemistry (metallurgy) technolog...