Surface Oxygen Functional Groups Research Articles

Photochemically induced aging of polystyrene nanoplastics and its impact on norfloxacin adsorption behavior

The co-occurrence of nanoplastics (NPs) and antibiotics in the environment is a growing concern for ecological safety. As NPs age in natural environments, their surface properties and morphology may change, potentially affecting their interactions with co-contaminants such as antibiotics. It is crucial to understand the effect of aging on NPs adsorption of antibiotics, but detailed studies on this topic are still scarce. The study utilized the photo-Fenton-like reaction to hasten the aging of polystyrene nanoplastics (PS-NPs). The impact of aging on the adsorption behavior of norfloxacin (NOR) was then systematically examined. The results showed a time-dependent rise in surface oxygen content and functional groups in aged PS-NPs. These modifications led to noticeable physical changes, including increased surface roughness, decreased particle size, and improved specific surface area. The physicochemical changes significantly increased the adsorption capacity of aged PS-NPs for norfloxacin. Aged PS-NPs showed 5.03 times higher adsorption compared to virgin PS-NPs. The adsorption mechanism analysis revealed that in addition to the electrostatic interactions, van der Waals force, hydrogen bonding, π-π* interactions and hydrophobic interactions observed with virgin PS-NPs, aged PS-NPs played a significant role in polar interactions and pore-filling mechanisms. The study highlights the potential for aging to worsen antibiotic risk in contaminated environments. This study not only enhances the comprehension of the environmental behavior of aged NPs but also provides a valuable basis for developing risk management strategies for contaminated areas.

Resembling Graphene/Polymer Aerogel Morphology for Advancing the CO2/N2 Selectivity of the Postcombustion CO2 Capture Process.

The separation of CO2 from N2 remains a highly challenging task in postcombustion CO2 capture processes, primarily due to the relatively low CO2 content (3-15%) compared to that of N2 (70%). This challenge is particularly prominent for carbon-based adsorbents that exhibit relatively low selectivity. In this study, we present a successfully implemented strategy to enhance the selectivity of composite aerogels made of reduced graphene oxide (rGO) and functionalized polymer particles. Considering that the CO2/N2 selectivity of the aerogels is affected on the one hand by the surface chemistry (offering more sites for CO2 capture) and fine-tuned microporosity (offering molecular sieve effect), both of these parameters were affected in situ during the synthesis process. The resulting aerogels exhibit improved CO2 adsorption capacity and a significant reduction in N2 adsorption at a temperature of 25 °C and 1 atm, leading to a more than 10-fold increase in selectivity compared to the reference material. This achievement represents the highest selectivity reported thus far for carbon-based adsorbents. Detailed characterization of the aerogel surfaces has revealed an increase in the quantity of surface oxygen functional groups, as well as an augmentation in the fractions of micropores (<2 nm) and small mesopores (<5 nm) as a result of the modified synthesis methodology. Additionally, it was found that the surface morphology of the aerogels has undergone important changes. The reference materials feature a surface rich in curved wrinkles with an approximate diameter of 100 nm, resulting in a selectivity range of 50-100. In contrast, the novel aerogels exhibit a higher degree of oxidation, rendering them stiffer and less elastic, resembling crumpled paper morphology. This transformation, along with the improved functionalization and augmented microporosity in the altered aerogels, has rendered the aerogels almost completely N2-phobic, with selectivity values ranging from 470 to 621. This finding provides experimental evidence for the theoretically predicted relationship between the elasticity of graphene-based adsorbents and their CO2/N2 selectivity performance. It introduces a new perspective on the issue of N2-phobicity. The outstanding performance achieved, including a CO2 adsorption capacity of nearly 2 mmol/g and the highest selectivity of 620, positions these composites as highly promising materials in the field of carbon capture and sequestration (CCS) postcombustion technology.

Properties of Carbon Fibers as Supercapacitor Electrodes via Electrospinning Using a Blending Solution of Polyacrylonitrile and Bisphenol A

Supercapacitors have attracted attention as efficient energy storage systems owing to their high power density and cycling stability. The use of appropriate electrode materials is important for high-performance supercapacitors, and various carbon materials have been studied as supercapacitor electrodes. In this study, carbon nanofibers with high specific surface areas were fabricated via a simple electrospinning process. Carbon nanofibers were fabricated by adjusting the ratio of polyacrylonitrile (PAN) to bisphenol A (BPA) and evaluated as electrode materials for supercapacitors. With the addition of BPA, improved specific surface area and oxygen functional groups were observed compared with nanofibers using only PAN. Therefore, BPA3, which had the highest specific surface area, exhibited a 28% improvement in capacitance (162 F/g) compared with BPA0 fabricated using only PAN. Carbon nanofibers fabricated by adjusting the ratio of BPA to PAN are promising electrodes for supercapacitors owing to their high capacitance and stability.

Fabrication of high voltage and energy dense supercapacitor with Manilkara zapota seeds derived porous activated carbon in acidic electrolyte

Achieving a high working potential window beyond the water electrolysis limit (> 1.23 V) has always been a big challenge in the fabrication of aqueous supercapacitors (SCs). Since energy density has quadratic dependence on voltage, broadening of cell voltage can remarkably increase the energy density of the capacitor. Unfortunately, most of the aqueous electrochemical capacitors operated in strongly acidic or alkaline electrolytes show poor energy densities owing to their narrow operating voltage limit. To obtain a high voltage range of aqueous symmetric carbon/carbon capacitors and achieve high energy density, the chemistry of electrode materials and the electrochemical kinetics of electrolytes play a critical role. Hence, in the present work, we explore a porous activated carbon produced from the seeds of Manilkara zapota (ACMZ-700) in combination with sulfuric acid electrolyte to obtain an encouraging electrochemical stable working voltage window. Thus, the resulting symmetric SC effectively exhibited an enlarged cell voltage of 1.5 V in an acidic medium. Importantly, due to the positive role of oxygenated surface functional groups of the ACMZ-700 active material, the fabricated symmetric cell delivered an attractive specific capacitance of 334 F g−1 @ 1 A/g. As a result of high capacitance and broader working voltage, the symmetric device delivered an excellent energy density of 26 Wh kg−1 at a power density of 748 W kg−1 and held excellent cycling stability over 10,000 charge/discharge cycles.

A Study on the Adsorption of Rhodamine B onto Adsorbents Prepared from Low-Carbon Fossils: Kinetic, Isotherm, and Thermodynamic Analyses.

The aim of this study was to obtain a series of activated carbon samples by the chemical activation of low-rank coal. The precursor was impregnated with a NaOH solution. Activated carbons were characterized by determining their textural parameters and content of surface oxygen functional groups and by using an elemental analysis. The carbons were tested as potential adsorbents for the removal of liquid pollutants represented by rhodamine B. The effectiveness of rhodamine B removal from water solutions depended on the initial concentration of the dye, the mass of rhodamine B, and the pH and temperature of the reaction. The isotherm examination followed the Langmuir isotherm model. The maximum adsorption capacity of the rhodamine B was 119 mg/g. The kinetic investigation favored the pseudo-second-order model, indicating a chemisorption mechanism. The thermodynamic assessment indicated spontaneous and endothermic adsorption, with decreased randomness at the solid-liquid interface. The experiment revealed that a 0.1 M HCl solution was the most effective regenerative agent.

Analysing the modifications of carbon black and other fillers after pyrolysis of model tyres

Carbon blacks (CBs) that are used as fillers to reinforce rubber contribute to tyre recycling issues. Although recovered carbon black (rCB) produced from the thermoconversion of waste tyres has poor reinforcing abilities in non-polar rubbers, the exact origin of the difference between rCBs and CBs is not elucidated. The characteristics of the rCBs produced from the steam pyrolysis of model laboratory-reinforced rubbers, with or without silica added, were analysed and compared to the pristine CB. X-Ray Diffraction revealed that the quantity of unorganised carbon in the rCB increased by about 25% after pyrolysis, revealing the occurrence of carbonaceous deposits originating from rubber carbonisation. They affected the filler texture, and part of the ultra-microporosity (i.e., pores within the diameter range 0.34–0.76 nm), which had a three-fold decrease in the rCB sample. The recovered fillers, with and without silica, had more oxygenated functional groups than the CB. The dispersibility and stability of the colloidal suspensions were affected by the increased surface oxygen functional groups. Reductive hydrogenation was utilised to remove the excess oxygen allowing an improved understanding of the rCBs. This is a promising method to maximise material reutilisation in the circular value chain of tyres.

Engineering metal oxide heterostructures derived from MOFs/MXene hybrids as efficient acetone sensor

Acetone, one of the most used solvents in industry and the laboratory, can anesthetize the central nervous system of humans and cause damage to the kidneys, pancreas, and liver. For the purpose of monitoring the leakage and concentration of acetone, α-/γ-Fe2O3/TiO2-X (α-/γ-Fe2O3-X) materials were successfully manufactured by in-situ solvothermal and calcination processes. Here, MIL-100-derived porous α-/γ-Fe2O3 and TiO2 nanoparticles are uniformly grown on the self-sacrificial template of exfoliated Ti3C2Tx nanosheets (ex-Ti3C2Tx) that simultaneously serve as the Ti source. The heterostructure between TiO2 and Fe2O3 therein is conducive to carrier transfer and sharp resistance change. And bulk resistance-controlled γ-Fe2O3 is able to raise the response to gas. Besides, the porous structure of α-/γ-Fe2O3-X could create plenty of oxygen vacancies and surface functional groups, which facilitate diffusion and contact interaction between acetone and active sites. Accordingly, the α-/γ-Fe2O3-X endow exceptional response (R = 105.5) towards 100 ppm acetone at 240 ℃, fast response/recovery time, outstanding selectivity and stability. To further substantiate this promotion mechanism, density functional theory (DFT) calculations were carried out for investigating the adsorption behavior of α-/γ-Fe2O3-X for acetone.

Effect of the pore structure characteristics of coal samples on the dynamic adsorption of water vapor

In order to study the dynamic adsorption process of water vapor in the pore structure of different coal samples (YJL for lignite, SEK for bituminous coal and BJ for anthracite). The pore structure characteristics of the three coal samples were analyzed by mercuric pressure method, liquid nitrogen adsorption method and infrared spectroscopy. Further, the water vapor adsorption capacity of the three coal samples under different humidity conditions was determined by dynamic water vapor sorption (DVS) experiments. In addition, the monolayer adsorption and multilayer adsorption at different humidity were calculated using the Dent model. The results showed that YJL had the largest surface pore volume and oxygen functional group parameter (IO = 12.41), and its water vapor adsorption capacity was also the highest. However, under high humidity conditions, the presence of a large number of pore throats in the YJL coal samples hindered multilayer adsorption, resulting in a water vapor adsorption percentage of only 18.07 %. On the other hand, SEK has a small oxygen functional group parameter (IO = 5.81), poor pore connectivity, and a certain pore throat structure, resulting in a low water vapor adsorption capacity of SEK coal samples, with a water vapor adsorption proportion of only 23.76 %. BJ coal has a large pore volume and a large number of oxygen functional groups on the surface (IO = 8.84), which has a good pore connectivity and the least number of pore throats structure, resulting in a water vapor adsorption ratio is higher at 87.38 %. On this basis, cylindrical and wedge-shaped pore models of coal samples were constructed, and molecular dynamics simulations were carried out to investigate the adsorption characteristics of water vapor in these pore models. The results show that the adsorption process of water molecules in coal develops continuously with “initial-water chain-water bridge-water lock”. By summarizing and analyzing the above experimental results, four control mechanisms of coal pore characteristics affecting water vapor adsorption were clarified. These findings are of great significance for studying the movement of water vapor in coal seams and understanding the degree of water confinement caused by hydraulic control measures.

Engineering Detrimental Functional Groups in Conductive Additives Toward High-Performance All-Solid-State Batteries.

Conductive additives are of great importance for the adequate utilization of active materials in all-solid-state lithium batteries by establishing conductive networks in the composite cathode. However, it usually causes severe interfacial side reactions with solid electrolytes, especially sulfide electrolytes, leading to sluggish ion transportation and accelerated performance degradation. Herein, a simple hydrogen thermal reduction process is proposed on a commonly used conductive additive Super P, which effectively removes the surface oxygen functional groups and weakens the interfacial side reactions with sulfide. With a small amount of 1 wt % reduced Super P, ASSLBs demonstrates a competitive capacity of 180.2 mAh g-1 , which is much higher than the 130.8 mAh g-1 of untreated Super P. Impressively, reduced Super P based ASSLBs also exhibit a higher capacity retention of 81.8 % than 64.6 % of untreated Super P. The cathode interfacial chemical evolutions reveal that reduced Super P could effectively alleviate the side reactions of sulfide. Reduced Super P shows better reversible capacity compared to reduced carbon nanofiber with almost no loss of capacity retention, due to its more complete conductive network. Our results highlight the importance of oxygen-containing functional groups for conductive additives, lightening the prospect of low-cost 0D conductive additives for practical ASSLBs.

Powdered activated carbon (PAC)-assisted peroxymonosulfate activation for efficient urea elimination in ultrapure water production from reclaimed water

Urea is a problematic pollutant in reclaimed water for ultrapure water (UPW) production. The sulfate radical-based advanced oxidation process (SR-AOP) has been recognized as an effective method for urea degradation. However, conventional metal-based catalysts for peroxymonosulfate (PMS) activation are unsuitable for UPW production due to issues related to metal ion leaching. In this study, the use of powdered activated carbon (PAC) was investigated for the removal of urea from reclaimed water. The PAC exhibited a high degree of defects (ID/IG = 1.709) and various surface oxygen functional groups (C–OH, C=O, and C–O), which greatly enhanced its catalytic capability. The PAC significantly facilitated PMS activation in the PMS + PAC system, leading to the complete urea decomposition. The PMS + PAC system demonstrated excellent urea removal efficiency within a wide pH range, except for pH < 3. Among the various anions present, the CO32− and PO43− inhibited urea degradation, while the coexistence of Cl− promoted urea removal. Furthermore, the feasibility test was evaluated using actual reclaimed water. The quenching test revealed that SO4−·, ·OH, and O2−· played crucial roles in the degradation of urea in the PAC-assisted SR-AOP. The oxygen functional groups (C–OH and O–C=O) and defect sites of PAC clearly contributed to PMS activation.

Transformation of Al Species on Carbon Surfaces: Effects of Al Species and Carbon Surface Oxygen Groups.

Control of residual Al is critical, owing to its high tendency to accumulate in drinking water distribution systems and its potential risks to human health. Herein, the effects of surface properties of activated carbon (AC) on intercepting different Al species (including monomeric Al and polymeric Al species-Al13) are evaluated. The results showed that Al in the form of monomers was considerably adsorbed by AC; whereas Al in the form of polymeric Al13 was held to a much lower degree by AC, and the effluent Al concentration was even higher than that without AC. By comparing virgin AC and hydrogen thermal treated AC, the surface oxygen functional groups on the AC were proposed to play a critical role in the transformation of Al species. The oxygen functional groups on the AC surface can directly form complexes with monomeric Al, thereby inducing the binding of monomeric Al on the AC surface. However, the AC surface oxygen groups could not bind to polymeric Al13, and the interaction between AC surface oxygen groups and polymeric Al13 partially transforms Al13 into monomeric Al species, which inhibited the self-aggregation of Al13. This study aims to provide new insights into the control of residual Al in water treatment plants to ensure drinking water safety.

Polyethylene-derived high-yield carbon material for upcycling plastic wastes as a high-performance composite filler

In this study, to address environmental challenges stemming from plastic wastes, we produced carbon material derived from polyethylene (PE-C) using thermal oxidation and carbonization processes. Prior to thermal oxidation, e-beam irradiation was employed to enhance oxidation reactions which facilitated transformation of linear chains to cyclic ladder structures, resulting in a threefold increase in carbonization yield compared to conventional methods. Our analysis using XRD, Raman spectroscopy, XPS, and SEM revealed that PE-C exhibited a crystal structure similar to commercial CB (C-CB). However, it featured three times more oxygen functional groups on its surface and consisted of individual particles without forming aggregates or agglomerates. We incorporated PE-C into a PA6 polymer matrix to create composite materials with various compositions, systematically comparing their electrical, thermal, and mechanical properties to C-CB/PA6. PE-C outperformed C-CB in terms of mechanical properties (65 MPa vs. 41 MPa) due to its surface oxygen functional groups, uniform dispersion even at high loadings, and a rough surface. Moreover, PE-C exhibited a lower surface area, which reduced interfacial thermal resistance and consequently enhanced thermal conductivity, resulting in a 16 % improvement compared to C-CB at 30 wt%.

Carbon nanosphere as an efficient support for CoOx nanoparticles on water decontamination via sulfite activation

Sulfite has recently been considered as the most potential alternative to peroxydisulfate and peroxymonosulfate for wastewater treatment because of its low ecotoxicity, low cost and abundant source. Although all sorts of homogeneous catalysts, such as Co2+, Cu2+, Fe2+, Mn2+, and so on, are developed for activating sulfites to generate SO4•−, it is of high significance to develop heterogeneous catalysts for wastewater treatment via sulfite activation. Herein, we have employed carbon nanosphere as an efficient support for CoOx nanoparticles on water decontamination via sulfite activation. The comparison with other carbon carriers (including carbon nanotubes and activated carbon) emphasized the vital role of CNS-600 in CoOx/CNS-600 for tetracycline (TC) degradation via Na2SO3 activization. Because CNS-600 presented an uniform structure of nanosphere, with surface nitrogen and oxygen functional groups, which were favorable for Na2SO3 activation and CoOx stabilization. This work proposes an efficient and heterogeneous Co-based nanomaterial for water decontamination via Na2SO3 activization.

Hierarchically Porous Carbon Rods Derived from Metal-Organic Frameworks for Aqueous Zinc-Ion Hybrid Capacitors.

Aqueous zinc-ion hybrid capacitors (ZIHCs), as ideal candidates for high energy-power supply systems, are restricted by unsatisfied energy density and poor cycling durability for further applications. The construction of a surface-functionalized carbon cathode is an effective strategy for improving the performance of ZIHCs. Herein, a high-performance ZIHC is achieved using oxygen-rich hierarchically porous carbon rods (MDPC-X) prepared by the pyrolysis of a metal-organic framework (MOF) assisted by KOH activation. The MDPC-X samples displayed high electric double-layer capacitance (EDLC) and pseudocapacitance owing to their oxygen-rich surfaces, abundant electroactive sites, and short ions/electron transfer lengths. The surface oxygen functional groups for the reversible chemical adsorption/desorption of Zn2+ are identified using ex situ X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Consequently, the as-assembled ZIHC exhibited a high capacity of 323.4 F g-1 (161.7mA h g-1) at 0.5 A g-1 and a retention of 147 F g-1 (73.5mA h g-1) at an ultrahigh current density of 50Ag-1, corresponding to high energy and power densities of 145.5W h kg-1 and 45kW kg-1, respectively. Furthermore, an excellent cycling life with 96.5% of capacity retention is also maintained after 10 000 cycles at 10 A g-1, demonstrating its promising potential for applications.

Nanoporous Activated Carbon Material from Terminalia chebula Seed for Supercapacitor Application

High-surface-area porous carbon materials with high porosity and well-defined pore structures are the preferred advanced supercapacitors electrode materials. Here, we report the electrochemical supercapacitive performance of novel high-porosity activated carbon materials prepared from biowaste Terminalia chebula (Harro) seed stones involving zinc chloride (ZnCl2) activation. Activation is achieved by mixing ZnCl2 with Harro seed powder (1:1 w/w) followed by carbonization at 400–700 °C under a nitrogen gas atmosphere. The amorphous carbon materials obtained exhibit excellent performance as electrical double-layer capacitor electrodes in aqueous electrolyte (1 M sulfuric acid) due to high specific surface areas (as high as 1382.6 m2 g−1) based on well-developed micropore and mesopore structures, and partial graphitic structure containing oxygenated surface functional groups. An electrode prepared using material having the optimal surface textural properties achieved a large specific capacitance of 328.6 F g−1 at 1 A g−1 in a three-electrode cell setup. The electrode achieved a good capacitance retention of 44.7% at a high 50 A g−1 current density and outstanding cycling performance of 98.2% even following 10,000 successive charge/discharge cycles. Electrochemical data indicate the significant potential of Terminalia chebula seed-derived porous carbons as high-performance electrode materials for high-energy-storage supercapacitor applications.

Effect of zinc-biochar composite aging on its physicochemical and ecotoxicological properties

The stability of Zn-biochar composites is determined by environmental factors, including the aging processes. This paper focused on the ecotoxicological evaluation of Zn-biochar (Zn-BC) composites subjected to chemical aging. Pristine biochars and composites produced at 500 or 700 °C were incubated at 60 and 90 °C for six months. All biochars were characterized in terms of their physicochemical (elemental composition, Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and porous structure), ecotoxicological properties (tested with Folsomia candida and Aliivibrio fischeri) and contaminant content (polycyclic aromatic hydrocarbons (PAH), heavy metals (HM) and environmentally persistent free radicals (EPFR)). An increase in the number of surface oxygen functional groups and increased hydrophilicity and polarity of all Zn-BC composites were observed due to oxidation during aging. It was also found that Zn-BC aging at 90 °C resulted in a 28–30% decrease in solvent-extractable PAHs (Ʃ16 Ctot PAHs) compared to nonaged composites. The aging process at both temperatures also caused a 104 fold reduction in EPFRs in Zn-BC composites produced at 500 °C. The changes in the physicochemical properties of Zn-BC composites after chemical aging at 90 °C (such as pH and HM content) caused an increase in the toxicity of the composites to Folsomia candida (reproduction inhibition from 19 to 24%) and Aliivibrio fischeri (luminescence inhibition from 96 to 99%). The aging of composites for a long time may increase the adverse environmental impact of BC-Zn composites due to changes in physicochemical properties (itself and its interactions with pollutants) and the release of Zn from the composite.

Utilization of Organic Waste in a Direct Carbon Fuel Cell for Sustainable Electricity Generation

There is much organic waste that comes from by-products of agriculture and product processing, solid waste from livestock, and municipal waste. Conventional methods that are widely used for the treatment and management of organic fractions of waste are landfilling, composting, anaerobic digestion, incineration, gasification, and pyrolysis. Among the above methods, pyrolysis is a relatively simple, robust, and scalable technology for transforming diverse organic waste feedstock into renewable energy products. Recently, the electrochemical conversion of biochar into electricity in direct carbon fuel cells (DCFC) has also been investigated and shown to be feasible and highly efficient. This paper focuses on the utilization of organic waste as a fuel and the investigation of their characteristics during electrochemical reactions in molten hydroxide direct carbon fuel cells (MH-DCFCs). Organic waste of different origins (the food-processing industry, urban and suburban areas, municipal solid organic waste, sewage sludge) with diversified characteristics was used as the main feedstock. The lowest power density was determined for sewage sludge (5.1 mW cm−2), and the best results were obtained for peanut shells (53.14 mW cm−2). This study concludes that higher elemental carbon, lower ash content and the presence of reactive surface oxygen functional groups in biochar obtained from organic waste might contribute to better cell performance. Moreover, the research establishes the potential of carbonized organic waste as a prospective alternative fuel source for power generation in an MH-DCFC.

Reduced and oxidized rice straw biochar for hexavalent chromium adsorption: Revisiting the mechanism of adsorption

Surface oxygen functional groups of biochar were tuned by oxidation and reduction of biochar for establishing Cr(VI) adsorption mechanism. Oxygen functional groups (OFGs) on the surface of leached rice straw biochar (LBC4-6) obtained from pyrolysis at 400, 500 and 600 °C, were oxidized to furnish OBC4-6 using modified Hummer's method. Reduced biochar RBC4-6 were obtained by esterification and NaBH4/I2 reduction of oxidized biochar (OBC4-6). The modified biochar were characterized by increase in O/C and H/C ratio, respectively, in case of OBC4-6 and RBC4-6. The Cr(VI) adsorption by modified biochar LBC4-6, OBC4-6, and RBC4-6 showed optimum conditions of pH 3 and dose 0.1 g/L with a good non-linear fit for Langmuir & Freundlich isotherm. The maximum adsorption (Qm) followed the trend: OBC4 (17.47 mg/g) > RBC4 (15.23) > OBC5 (13.23) > LBC4 (10.23) > RBC5 (9.83) > OBC6 (9.60) > RBC6 (7.24) > LBC5 (6.32) > LBC6 (5.98). The adsorption kinetics for adsorption of Cr(VI) on to modified biochar fits pseudo second order (PSO), Elovich and intraparticle diffusion kinetics, showing a chemisorptions in case of biochar L/O/RBC4-6. The lower temperature modified biochar O/RBC4 show better Cr(VI) adsorption. X-ray Photoelectron Spectroscopy (XPS) studies establish optimum OFGs for reduction of Cr(VI) and chelation of the reduced Cr(III). Adsorption and stripping cycles show the oxidized and reduced biochar as better adsorbents with excellent stripping of Cr up to >98 % upon desorption with 1 M NaOH.

Photocatalytic Degradation of Tetracycline Hydrochloride by Mn/g-C3N4/BiPO4 and Ti/g-C3N4/BiPO4 Composites: Reactivity and Mechanism

The environmental pollution caused by antibiotics is becoming more serious. In this study, the Mn/BiPO4/g-C3N4 composite (Mn-BPC) and the Ti/g-C3N4/BiPO4 composite (Ti-BPC) were prepared by hydrothermal reaction method and solvent method, respectively, and applied to the degradation of tetracycline (TC) in an aqueous environment. The XRD and HRTEM results showed that these materials had the crystalline rod-like structure of BiPO4 and abundant carbon, nitrogen and carbon–oxygen surface functional groups. The degradation of TC by Ti-BPC and Mn-BPC were nearly 92% and 79%, respectively. The degradation processes of TC were well consistent with the pseudo-second-order kinetics model and R2 values were closer to 1. The trapping experiment showed that electron holes (h+) were the main reactive species for the degradation of tetracycline, OH· and O2− also have certain effects. Also, the possible photocatalytic degradation mechanism of Ti-BPC and Mn-BPC composites was thereby proposed. TC was firstly adsorbed on the surface of catalysts, and subsequently degraded by reactive species such as h+, OH· and O2− generated under visible light excitation. This study shows that the Ti-BPC and Mn-BPC photocatalysts have great potential in antibiotic degradation and can provide new ideas for antibiotic removal in aqueous environments.

RETRACTED: Characterization and performance evaluation of nylon-66 composite at various composition of carbon fibers and GNP reinforcement

Recycled reinforcements are being utilized more and more to make sustainable composites for load-bearing structural applications, which now dominate the key transportation industries, because they have lower environmental impact than virgin fiber manufacturing and are also less expensive. In order to improve the mechanical properties of composites, a combination of recycled carbon fibers (rCF) and waste tire-derived graphene nanoplatelets (GNP) with oxygen surface functional groups was used as reinforcement for the nylon-66 matrix. The alignment of the rCF and GNP during the injection molding process was monitored using numerical methods in conjunction with the rheological behavior of the compounds. The effective dispersion of the rCF and GNP was obtained using high shear mixing. In contrast, the flexural modulus and strength of the 20% rCF-0.3% GNP reinforced nylon-66 composites increased by 86% and 35%, respectively, while the tensile strength and modulus improved by 43% and 95%. Further, the addition of 0.3% GNP to the composition resulted in a 7.7% increase in Charpy notched impact energy compared to the 20% rCF composite. Moreover, the flow model developed to study the injection molding process of rCF/GNP reinforced composite using the fiber aspect ratio and distribution in the compounds described fiber alignment and provided insight into mechanical strengthening mechanisms.