Initial Solution pH Value Research Articles

Enhancement of photocatalytic activity of CeO2 nanorods through lanthanum doping (La–CeO2) for the degradation of Congo red dyes

The discharge of synthetic dyes into water bodies poses severe environmental risks due to their toxic and recalcitrant nature. This study explores the enhancement of photocatalytic properties of cerium dioxide (CeO2) nanorods by doping with lanthanum (La) to improve their efficacy in degrading aqueous solutions of Congo red dye. The CeO2 nanorods were synthesized via a hydrothermal method and subsequently doped with varying concentrations of La. The scanning electron microscopy (SEM) images confirmed the rod-like structures (nanorods) were observed for all samples, while the energy-dispersive X-ray spectroscopy (EDX) confirmed the homogeneous incorporation of La into the CeO2 matrix. The X-ray diffraction (XRD) spectra demonstrate lattice distortion due to substitutional defect. Photocatalytic experiments revealed that La-doped CeO2 nanorods exhibited significantly enhanced degradation capabilities compared to undoped counterparts, achieving up to a 3-fold photocatalytic kinetics ((30 ± 2) × 10−3 min−1) compared to the undoped counterparts ((11.5 ± 0.4) × 10−3 min−1). Influence of various parameters that affect the photocatalysis performance (i.e., contact time, initial dye concentration, catalyst dosage, and dye solution pH value) were also investigated. Radical scavenger experiments reveal that superoxide radicals play a dominant role in the photocatalytic process. Collectively, these findings confirm that the strategic incorporation of lanthanum into CeO2 nanorods not only enhances their overall photocatalytic efficiency but also tailors their activity towards specific pollutants through radical-mediated pathways.

High-efficiency removal of As(iii) from groundwater using siderite as the iron source in the electrocoagulation process.

Electrocoagulation technology, due to its simplicity and ease of operation, is often considered for treating arsenic-contaminated groundwater. However, challenges such as anode wear have hindered its development and application. This study aims to develop a siderite-filled anode electrocoagulation system for efficient removal of As(iii) and investigate its effectiveness. The impact of operational parameters on the removal rate of As(iii) was analyzed through single-factor tests, and the stability and superiority of the device were evaluated. The response surface methodology was employed to analyze the interactions between various factors and determine the optimal operational parameters by integrating data from these tests. Under conditions where the removal rate of As reached 99.3 ± 0.37%, with an initial concentration of As(iii) at 400 μg L-1, current intensity at 30 mA, initial solution pH value at 7, and Na2SO4 concentration at 10 mM. The flocculant used was subjected to characterization analysis to examine its structure, morphology, and elemental composition under these optimal operational parameters. The oxidation pathway for As(iii) within this system relies on integrated results from direct electrolysis as well as ˙O2 -, ˙OH, and Fe(iv) mediated oxidation processes. The elimination of arsenic encompasses two fundamental mechanisms: firstly, the direct adsorption of As(iii) by highly adsorbent flocculants like γ-FeOOH and magnetite (Fe3O4); secondly, the oxidation of As(iii) into As(v), followed by its reaction with siderite or other compounds to generate a dual coordination complex or iron arsenate, thus expediting its eradication. The anodic electrocoagulation system employing siderite as a filler exhibits remarkable efficiency and cost-effectiveness, while ensuring exceptional stability, thereby providing robust theoretical underpinnings for the application of electrocoagulation technology in arsenic removal.

Facile fabrication of Ag decorated MnFeO3 catalyst: Comparative analysis of visible light driven antibiotic reduction and antibacterial performance

Photocatalysis is an effective method with the potential to eliminate pharmaceutical compounds from water sources. Manganese ferrite (MnFeO3), a type of multiferroic perovskite catalyst, has attracted significant attention due to its small band gap, however its application was limited due to its high recombination rate and low quantum efficiency. It was therefore aimed to improve the properties of MnFeO3 by doping silver (Ag)-particles. In this study, Ag–MnFeO3 photocatalysts with different Ag content (1–3 mmol%) were synthesized by performing a facile hydrothermal method. The as-prepared samples were characterized using x-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDS), transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), ultraviolet–visible spectroscopy (DRS), photoluminescence spectroscopy (PL), electrochemical impedance spectroscopy (EIS) and Brunauer-Emmett-Teller (BET) method, showing successful addition of Ag-particles with the MnFeO3 structure. Then, the as-synthesized materials were investigated as: (i) photocatalysts for degradation tetracycline (TC) antibiotic and (ii) antibacterial agents for bacteria. The Ag–MnFeO3 catalyst demonstrated superior catalytic performance (95.7%), which was 1.6 times higher than that of pristine MnFeO3 (59.7%). The positive effect was ascribed to oxygen vacancies, enhanced light absorption ability, and lower recombination rate. The Ag–MnFeO3 catalyst also showed satisfactory removal performances in real water matrices. Furthermore, radical trapping tests depicted that the superoxide radicals played a dominant role in the photodegradation system. In addition, Box–Behnken design (BBD) was performed to determine the optimum conditions, which were determined as catalyst dosage of 0.45 g/L, initial TC concentration of 5.10 mg/L, and initial solution pH value of 3.69. In terms of antibacterial tests, the incorporation of Ag into the MnFeO3 structure greatly increased the antimicrobial resistance against bacteria. Our findings disclose that the incorporation of Ag into the MnFeO3 structure can be regarded as a feasible and promising approach to improve both photocatalytic degradation and antibacterial performances.

Performance and mechanism of magnetic Fe3O4@MnO2 catalyst for rapid degradation of methylene blue by activation of peroxymonosulfate

A flower ball shaped magnetic Fe3O4@MnO2 core-shell catalyst has been synthesized and the average diameter is about 135–180 nm. The Fe3O4@MnO2 (140.6 m2 g−1) showed a larger specific surface area than Fe3O4 (64.6 m2 g−1) due to the thin film like nature of MnO2. The Fe3O4@MnO2 exhibited a great degradation performance for methylene blue (MB, 20 mg L−1, pH=7) after the addition of peroxymonosulfate (PMS, 0.18 g L−1) when the dosage of Fe3O4@MnO2 is 0.3 g L−1, which reached 98% within 20 min. Additionally, the influences of catalyst dosage, PMS concentration and initial pH value of MB solution have been studied to maximize the catalytic performance of Fe3O4@MnO2. Results showed that the increase of catalyst dosage and PMS concentration have improved the degradation efficiency and reaction rate of MB. However, the effect of pH on MB removal was complex and has been analyzed. According to XPS and quenching studies, the degradation effects of free radicals produced by catalyst-activated PMS on MB followed the order 1O2> •OH> SO4•−. This research demonstrates that Fe3O4@MnO2 is an effective catalyst for the degradation of organic dye MB.

Intensive Treatment of Organic Wastewater by Three-Dimensional Electrode System within Mn-Loaded Steel Slag as Catalytic Particle Electrodes.

Developing a green, low-carbon, and circular economic system is the key to achieving carbon neutrality. This study investigated the organics removal efficiency in a three-dimensional electrode reactor (3DER) constructed from repurposed industrial solid waste, i.e., Mn-loaded steel slag, as the catalytic particle electrodes (CPE). The CPE, a micron-grade material consisting primarily of transition metals, including Fe and Mn, exhibited excellent electric conductivity, catalytic ability, and recyclability. High rhodamine B (RhB) removal efficiency in the 3DER was observed through a physical modelling experiment. The optimal operating condition was determined through a single-factor experiment in which 5.0 g·L-1 CPE and 3 mM peroxymonosulfate (PMS) were added to a 200 mL solution of 10 mM RhB under a current intensity of 0.5 A and a 1.5 to 2.0 cm distance between the 2D electrodes. When the initial pH value of the simulated solution was 3 to 9, the RhB removal rate exceeded 96% after 20 min reaction. In addition, the main reactive oxidation species in the 3DER were determined. The results illustrated that HO• and SO4•- both existed, but that the contribution of SO4•- to RhB removal was much lower than that of HO• in the 3DER. In summary, this research provides information on the potential of the 3DER for removing refractory organics from water.

Initial solution pH value for the construction of a 3D hydroxyapatite via the trisodium citrate-assisted hydrothermal route.

In this study, a trisodium citrate (TSC)-assisted hydrothermal method is utilized to prepare three-dimensional hydroxyapatite (3D HA). Understanding the role of TSC in the preparation of 3D HA crystals may provide valuable methods to design advanced biomaterials. As one of the indexes of solution supersaturation, the initial pH (ipH) value can not only directly affect the nucleation rate, but also affect the growth of HA crystals. In this work, the effect of the ipH on the microstructure, particle size distribution, and specific surface area of the 3D HA is explored. Results showed that the morphology of 3D HA transformed from a bundle to a dumbbell ball and then a dumbbell with an increase in the ipH. A corresponding mechanism of such a structural evolution was proposed, providing inspiration for the fabrication of innovative 3D HA structures with enhanced biological functionality and performance.

Synthesis of mesoporous MIL-100(Fe) from acid mine drainage sludge for norfloxacin removal: Industrial sludge high value utilization, adsorbent performance and contaminant removal mechanisms

Recovery of heavy metals from acid mine drainage sludge (AMDs) and their conversion into high value-added materials such as metal-organic frameworks (MOFs) is of great significance for sustainable development. MOFs have broad application prospects in liquid phase pollutant removal, owing to super high specific surface area and adjustable structure. In this study, MIL-100(Fe) with mesoporous structures was successfully prepared from AMDs by acid leaching-hydrothermal method. And the obtained MIL-100(Fe) was employed as an adsorbent for adsorptive norfloxacin (NOR) removal from wastewater. The adsorption results showed that the maximum adsorption capacity can reach 280.84 mg/g under the condition of 298 K, the initial pH value of solution is 10 and the dosage of catalyst is 0.1 g/L. According to the N2 sorption–desorption isotherms, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) characterization, the adsorption mechanism of NOR on MIL-100(Fe) is mainly attributed to electrostatic interaction, π-π stacking, pore filling and coordination. Furthermore, the adsorbent maintained 75.05% of its initial adsorption capacity after 5 cycles, indicating that MIL-100(Fe) has excellent stability. This study provides a new idea for the resource utilization of industrial sludge.

A novel hierarchical 0D/3D NH2-MIL-101(Fe)/ZnIn2S4 S-scheme heterojunction photocatalyst for efficient Cr(VI) reduction and photo-Fenton-like removal of 2-nitrophenol

In this work, we designed a new hierarchical 0D/3D NH2-MIL-101(Fe)/ZnIn2S4 (NM-101(Fe)/ZIS) S-scheme heterojunction photocatalyst using a simple oil bath technique, in which nanometer-sized NM-101(Fe) are extensively scattered on the surface of ZIS microspheres. In contrast to an acidic environment, the optimal 10% NM-101(Fe)/ZIS can remove 94% of Cr(VI) in 60 min under neutral circumstances, the apparent rate constant is 24.6 and 3.26 times that of NM-101(Fe) and ZIS, respectively. This is due to the hierarchical 0D/3D heterostructure and the unique S-scheme photogenerated carrier transfer path, which successfully encourage the separation of photogenerated carriers while simultaneously enhancing redox ability. Specially, an efficient photo-Fenton-like system was developed using Fe3+ in NM-101(Fe) in conjunction with external H2O2 for entirely eliminating the refractory 2-nitrophenol pollutant in 120 min. It has an apparent rate constant that is 5.63 and 3.99 times that of pure NM-101(Fe) and ZIS. In order to better meet the demands of practical wastewater treatment, the impact of various photocatalyst doses, initial solution concentrations, coexisting ions and pH values on its photocatalytic activity were investigated. Finally, this work provides an idea to construct unique 0D/3D S-scheme heterostructure and effective photo-Fenton-like system for photocatalytic water purification.

Preparation of g-C3N5 composites for butyl xanthate photocatalytic degradation

The nitrogen-rich graphite-phase carbon nitride (g-C3N5) supported TiO2 photocatalyst (Ti-CN) was prepared using TiO2 and 3-amino 1, 2, 4-triazole as raw materials for butyl xanthate residual (SBX) removal from mineral processing wastewater. The crystal, morphology, specific surface area and optical properties of the Ti-CN were characterized by XRD, TEM, UV–vis DRS, BET and PL. These results showed that TiO2 particles were uniformly dispersed on g-C3N5 nanosheets, and the heterojunction was formed. The formation of heterojunction improved its response to visible light, and promoted the separation of photoelectron-hole, contributing to improving its photocatalytic activity. The influence of catalyst dosage, initial SBX concentration and pH value of the SBX solution on SBX photocatalytic degradation removal was investigated. The Box-Behnken design of the response surface was used to optimize the process conditions to obtain the optimal experiment conditions with the pH of 7.04, catalyst dosage of 50.2 mg and SBX concentration of 56.6 mg/L. The SBX photocatalytic degradation removal of Ti-CN is 98.15 %, which is close to the predicted value of 97.75 % at the optimal experiment conditions. Meanwhile, the SBX degradation removal of Ti-CN still had 90.21 % after five cycles, indicating that Ti-CN has good stability. These results indicate that Ti-CN can be used as the promising photocatalyst for SBX from mineral processing wastewater.

High-efficiency degradation of norfloxacin by cathodic micro-arc plasma electrolysis:Optimization of operation parameters and investigation on kinetics

In this work, the norfloxacin antibiotic (NOR) in simulated wastewater solution was rapidly degraded by a novel cathodic micro-arc plasma electrolysis (CMPE) treatment within 20 min. The effects and kinetics of initial pH value of solution, supporting electrolyte, and applied voltage on this NOR degradation process were systematically investigated. The intermediate products are analyzed by a Liquid Chromatograph-Mass Spectrometer (LC-MS), and the possible degradation pathways in the NOR degradation process were proposed. The results obtained showed that the NOR removal efficiency increased with the increase of the initial pH value of the solution. When KCl was employed as the supporting electrolyte instead of KNO3 and K2SO4, the removal efficiency of NOR is the highest. In addition, the removal efficiency is not significantly different at 340 V, 380 V, and 420 V, but it is more beneficial to the removal of chemical oxygen demand (COD) and the increase of average current efficiency (ACE) at 380 V. Furthermore, under the optimized operating parameters for the initial pH value of 9, supporting electrolyte of KCl, and applied voltage of 380 V, the 100 mg/L NOR solution can be completely removed within 10 min, and the energy yield and average current efficiency were 0.385 g (kW⋅h)-1 and 0.118. Further, it is found that the degradation pathways of NOR mainly include the piperazine ring opening, hydroxylation, defluorination, and quinoline ring transformation. Overall, this study provides a high-efficiency and novel technique for the NOR degradation treatment.

Persulfate activation by sulfide-modified nanoscale zero-valent iron for metronidazole degradation: Mechanism, major radicals and toxicity assessment

Sulfide-modified nanoscale zero-valent iron (SnZVI) is considered to be an effective method for persulfate (PS) activation. Here, the catalytic activity was evaluated in view of the potential influencing factors, including the sulfidation regent, Fe/S molar ratio, initial solution pH value, catalyst dosage, PS dosage, initial MNZ concentration and common anion species. The complete removal was obtained when Na2S was chosen at Fe/S molar ratio of 0.05 with 1.5 g·L−1 SnZVI and 1.5 mM PS. SnZVI exhibited a promising application owing to the high pH adaptation and the outstanding reusability. The high and persistent release of Fe2+ and FexSy generated on the surface, which accelerated the electron transfer rate for PS activation. The main reactive oxygen species, including OH, SO4−, O2− and 1O2, were further determined. However, OH rather than SO4− was the dominant reactive radical in our study. Finally, the degradation products and possible pathways were predicted based on the intermediate analysis. The T.E.S.T theoretical calculation indicated that the ecotoxicity of the various intermediate products of MNZ were greatly reduced. These results demonstrated that SnZVI/PS was a promising strategy for practical application in the remediation of MNZ contaminated water.

Synthesis, characterization and heterogeneous photo-Fenton-like catalyst activity of a novel inorganic-organic 2D framework based on reduced α-Keggin phosphomolybdate

A novel inorganic-organic 2D framework [CuI2CuII2(L)4(PMoV3MoVI9O40)(H2O)] (CuLPMo12) [L = 4-(4H-1,2,4-triazol-4-yl)pyridine)] based on reduced α-Keggin phosphomolybdate was hydrothermally synthesized and fully characterized. CuLPMo12 was found to be an efficient heterogeneous photo-Fenton-like catalyst for the degradation of dyes including methyl orange (MO), methylene blue (MB) and rhodamine B (RhB). The Fenton-like catalyst activity study of CuLPMo12 was carried out by employing RhB as model dye, because it had the best catalytic effect on RhB degradation. The degradation of RhB was affected by initial pH value and concentration of RhB solution, concentration of H2O2 and CuLPMo12 dosage. The optimum conditions for RhB degradation in the photo-Fenton-like progress were determined, the color of RhB could be completely removed in 5 min and the total organic carbon (TOC) removal was up to about 81.8% in 3 h under these conditions. These data were superior to that of similar compounds reported by other groups. Moreover, this system could work in a wide pH range and the optimum pH value was 7. Working at neutral pH made it be more convenient to operate than the acidic traditional Fenton system. UV–Vis spectroscopy results confirm that the N-deethylation and the conjugated chromophore cleavage reactions occurred simultaneously in a stepwise manner during RhB degradation process. Mechanism research indicates that the active species, such as 1O2,•OH, and •O2H/O2•− were responsible for RhB degradation. The better stability and recyclability of CuLPMo12 suggest that the present photo-Fenton-like system has potential in practical wastewater treatment.

Short wet-steaming low-carbon cleaner pad dyeing of cotton/polyamide/lyocell fabric with reactive dyes

Cotton/polyamide/lyocell three-component fabrics are usually dyed by the traditional dip dyeing technology with two kinds of dyes, which has the disadvantages of long process, high energy consumption and high cost. In this research, the short process cleaner pad dyeing technology for cotton/polyamide/lyocell fabric was developed. The optimal dyeing conditions were that the pH value of initial dye solution was 3–4, the reactive red 195 dye concentration was 10 g/L in the preliminary dye bath, the concentration of NaOH and Na2CO3 were 10 g/L in the alkaline fixing solution, and the steaming time of acid solution and alkali solution was 4 mins. The dyeing effects and fixation rate indicated that short wet-steaming technology was the optimum method. The developed short wet-steaming low-carbon cleaner pad dyeing technology of cotton/polyamide/lyocell fabric not only ensured the color yield, reproducibility, dyeing uniformity and permeability, but also saved dyes and chemicals, shortened dyeing time by 17.4 %, reduced power and heat consumption by 27.1 % and 15.1 %, and decreased carbon emission by 24.6 % compared with traditional dyeing. The K/S values of the dyed samples by short wet-steaming pad dyeing technique indicated that bifunctional reactive dyes with monochlorotriazine and vinyl sulfone sulfate groups (M-type) were superior to the other three kinds of reactive dyes. In the era of low-carbon economy, short wet-steaming low-carbon cleaner pad dyeing of cotton/polyamide/lyocell fabric with reactive dyes is an advanced short process dyeing technology worth of promotion for dyeing a variety of industrial crops and products.

Characterization and dye adsorption effectiveness of activated carbon synthesized from olive pomace

Studies, about products obtained from agricultural wastes, have increased within the scope of zero waste studies . The olive pomace is produced as a result of olive oil production. In the present study, activated carbon was synthesized using the olive pomace taken from the olive pomace processing plant operating with a three-phase process. The synthesized activated carbon characterization was performed using Scanning Electron Microscope (SEM), Fourier-Transform Infrared Spectroscopy (FT-IR), Brunauer – Emmett – Teller (BET), and X-Ray Crystallography (XRD) devices. Olive pomace activated carbon (OPAC) was used for the adsorption of dye from an aqueous solution. The adsorption efficiency of the OPAC was investigated. The initial pH value of dye solution (6-9), the amount of activated carbon (0.5 and 1.0 g/L), and initial dye concentration (600-1200 mg/L) were optimized. Also, adsorption kinetic and isotherm calculations were evaluated. The optimum parameters were found as the original pH value (pH=8) of dye solutions, OPAC amount of 1.0 g/L and the initial concentration of 1000 mg/L. The Langmuir isotherm model and the pseudo-second-order kinetic model were found as the most suitable models. It can be said that the synthesized material can be used at dye removing from wastewater.

Highly effective mineralization of acetic acid wastewater via catalytic ozonation over the promising MnO2/γ-Al2O3 catalyst

The complete mineralization of acetic acid in wastewater through a biodegradation process is difficult due to the α-position methyl coordinated with the carboxyl group, and this work explored the oxidation performance of acetic acid by catalytic ozonation with metal oxides supported on γ-Al2O3. It was found that MnO2/γ-Al2O3 catalyst achieved superior mineralization performance to Co/Fe/CeOx supported on γ-Al2O3 for acetic acid wastewater treatment. The effects of MnO2 loading, catalyst dosage, acetic acid concentration, O3 concentration, ozonation temperature, and initial pH value of the acetic acid solution were investigated. Typically, the mineralization of acetic acid over 1.0 wt.% MnO2/γ-Al2O3 catalyst was as high as 88.4% after 300 min ozonation of 1.0 g·L‒1 acetic acid at 25 °C with the highest energy efficiency around 15 g·kWh‒1. By contrast, the mineralization of acetic acid could only reach 43.2% in the absence of the catalyst, with an energy efficiency of 5.1 g·kWh−1. Radical quenchers and indicated that ·OH radical, O2− species originated from ozone played an important role in the catalytic ozonation of acetic acid into CO2 and H2O. Besides, the catalytic ozonation mechanism of acetic acid over MnO2/γ-Al2O3 was carefully proposed based on the in situ DRIFTS results.

Highly efficient activation of peroxymonosulfate by novel CuO-Chrysotile catalytic membrane for degradation of p-nitrophenol

A novel CuO-Chrysotile thin membrane catalyst was prepared by simple impregnation-calcination route, which provided new insights of catalytic membranes by natural mineral fiber for the degradation of organic contaminants in wastewater treatment. Through intermittent and continuous catalytic degradation experiments, peroxymonosulfate (PMS) was efficiently activated by the membrane to degrade p-nitrophenol (PNP), and the effects of experimental parameters (including initial solution pH value, PMS dosage, catalyst dosage, reaction temperature, membrane mass and flow rate) on PNP degradation were systematically studied. The results showed that the catalytic membrane had great catalytic performance and long-term stability, it could completely degrade 10 mg/L of PNP within 60 min and its degradation ratio could remain above 90 % after 5 cycles. Meanwhile, it was worth noting that 0.15 g of CuO-Chrysotile catalytic membrane used as fixed bed could continuously degrade 12.5 L of PNP solution with gratifying performance, which proved that the catalytic membrane had convenient use method and great application effect. The mechanism study found that 1O2 produced in this process played a key role in the degradation of PNP. From the aspects of manufacturing cost, catalytic performance and service life, the novel CuO-Chrysotile catalytic membrane has excellent industrial application potential.

A novel octamolybdate‐based organic–inorganic hybrid as photo‐Fenton‐like catalyst for degradation of methylene blue

A γ‐Mo8O26‐based organic–inorganic hybrid [Cu2(L)2(γ‐Mo8O26)0.5(H2O)]•H2O (CuLMo8) [L = 5‐(pyrimidyl)tetrazolate] was hydrothermally synthesized and fully characterized by various spectral techniques. In the crystal structure of CuLMo8, the μ2‐bridging γ‐Mo8 anion coordinates with Cu ions to extend into a 2D network. CuLMo8 displayed excellent photo‐Fenton‐like catalyst properties for MB degradation under UV light irradiation. Complete decolorization of MB solution was finished in 5 min, and the degradation rate reached 97.9% in 7 min. The degradation rate of the present system was much higher than that of similar systems in the literature. The synergistic effect of CuLMo8 and H2O2 was the fundamental reason for the high degradation rate. Initial pH value and concentration of MB solution, catalyst dosage, and concentration of H2O2 were the main factors to affect the degradation rate. Hydroxyl (•OH) and superoxide (•O2H/O2•‐) radicals were the major reactive species to degrade MB molecules. Moreover, the total organic carbon (TOC) removal was about 37.5% in 3 h, indicating mineralization and decolorization did not take place at the same time. The possible MB degradation pathway was deduced depending on the data gained. In view of the high catalytic efficiency, repeated use, and no need to adjust the pH value of MB solution, this heterogeneous catalyst might have potential to deal with practical wastewater.

A novel method for removing NOx from simulated marine exhaust gas in wet absorption system using Na2SO3/THS composite solution

AbstractSince it is difficult to deal with high‐concentration nitrates in scrubbed wastewater onboard vessels, the application of traditional wet denitration technology is limited to some extent. Here a novel method for removing pre‐oxidized NOx by using Na2SO3/THS composite solution is proposed with the aim to obtain high NOx absorption efficiency and low nitrate concentration in scrubbed wastewater simultaneously. The effects of Na2SO3 concentration, THS concentration, NOx oxidation degree, coexistence of SO2 and O2 in flue gas, initial pH value and temperature of absorption solution on denitration performance were discussed in detail. The results showed Na2SO3 could reduce NOx to nitrate, nitrite, and N2. The addition of THS could promote NOx absorption greatly by forming complexes with SO32−. When initial NOx concentration was 1000 ppm with a NOx oxidation degree of 50%, O2 concentration was 8%, Na2SO3 and THS concentrations were 25 and 20 mmol/L, a NOx absorption efficiency of 87% could be achieved, while nitrate and nitrite concentrations were 32.97 and 14.19 mg/L, respectively.

Optimized design of environmentally-friendly polydopamine nanoparticles for the stabilization of both thermo- and photo-oxidation of polypropylene: Size effects

Despite the huge success of commercial stabilizers (antioxidants, UV absorbers, etc.) on the functionality enhancement and lifetime prolonging of polymers, their toxicity on the environment has been raising severe concerns. Therefore, producing environmentally benign stabilizers via green chemistry has been attracting researchers’ attention. In this work, we demonstrated the potential of mussel-inspired polydopamine nanoparticles (PDA-NPs) with intrinsic biocompatibility for the enhancement of both thermo- and photo-oxidation stability of polypropylene (PP). The effects of PDA-NPs size on the antioxidative performance of PP were systematically explored. PDA-NPs with different sizes of 471 nm, 284 nm, and 98 nm were synthesized first by tuning the pH values of initial dopamine solutions. The antioxidation ability of PDA-NPs for PP increased remarkably with the decreasing size, which was attributed to a higher specific area and more available semiquinone structure of smaller PDA-NPs. Compared with pure PP, the oxidation induction time (OIT) and onset thermal decomposition temperature of optimized PP composites can be increased significantly from 9.8 min to 26.0‍‍ min by 165% with the addition of only 0.5 wt% PDA-NP (98 nm), while the thermo- and photo-oxidative degree (formation of carbonyl products) on the surface can be decreased by 53% and 92% at most, respectively. However, the dependence of UV protection ability of PDA-NPs for PP on their size is non-monotonic. As indicated by cross-sectional fluorescence and modulus imaging, the shallowest degradation depth was observed for PP composites with the PDA-NP size of 284 nm other than that of 98 nm. These results have demonstrated the feasibility of PDA-NPs as robust stabilizers and the importance of size design for optimizing the anti-aging efficiency of PDA-NPs, providing valuable insights into the development of multifunctional stabilizers for environmental sustainability.

Study on cobalt coating on ZTA particles by electroless plating and impact-abrasive wear behavior of ZTAp reinforced iron matrix composite

The electroless cobalt plating modification of ZTAp (Zirconia toughened alumina particle) surface and the impact-abrasive wear behavior of ZTAp and NbCp(Niobium carbide particle) reinforced Fe60 matrix composites (ZTAp-NbCp/Fe60) were investigated. Cobalt was deposited on the ZTAp surface by electroless plating (modified ZTAp) to strengthen the interface bonding between ZTAp and matrix. Both composites reinforced with modified ZTAp and unmodified ZTAp were prepared through vacuum sintering, and their impact-abrasive wear performance testing under different impact energy were carried out with MLD-10 impact-abrasive wear tester. The results showed that the optimal conditions to coat cobalt on the ZTAp surface included of: initial pH value of plating solution was 9, the concentration of NaH2PO2.H2O, and C4H4Na2O6.2H2O was 0.25 mol/L and 0.8 mol/L respectively. The impact-abrasive wear-resistant performance of the modified ZTAp reinforced Fe60 matrix composite was significantly enhanced by more than 35% than the unmodified ZTAp reinforced composite under high energy impact condition. Cobalt and liquid iron had good wettability, and the interface strength significantly increased. During the sintering process, cobalt diffused at the interface, thus leading to a significant binding force between ZTAp and the iron matrix interface. This study suggested that the modified ZTAp could have a better and longer protective effect than unmodified ZTAp on the matrix.