Pseudo-first Order Reaction Rate Research Articles

Key role of carbon as an efficient electron bridge in CuO@C@Fe2O3 for enhancing H2O2 activation during photo-assisted Fenton-like reaction

The Fe3+/Fe2+ cycle has been identified as the rate-limiting step in the Fenton system, and many efforts have been made to promote the Fe3+ reduction via external electrons provided by various electron donors. However, how to design an efficient electron transport pathway and then inhibit the invalid electron shuttle has been largely underestimated. In this study, two kinds of heterogeneous Fenton catalysts of CuO@Fe2O3 and CuO@C@Fe2O3 were prepared. The key role of carbon in transporting electrons as an electron bridge and its enhancement mechanism in photo-assisted Fenton-like performances were explored in detail. Compared with CuO@Fe2O3, the removal efficiency of tetracycline (TC) and the corresponding pseudo-first order reaction rate constants over CuO@C@Fe2O3 increased significantly from 88.6 % and 0.1054 min−1 to 99.7 % and 0.2058 min−1, respectively. Based on a series of probe experiments, visible light irradiation can promote the reduction of Cu2+ to Cu+, then the carbon in CuO@C@Fe2O3 can effectively transfer electrons from Cu+ to Fe3+, enhancing the Fe3+/Fe2+ cycle and the following Fenton-like efficiency. Since more ·OH while less ∙O2- was produced over CuO@C@Fe2O3, which further supports the fact that the enhanced Fe3+/Fe2+ cycle was due to the transfer electron from Cu+ to Fe3+ instead of the Haber-Wiss mechanism. Hence, this study provides new insight for effectively improving the transfer efficiency and effective utilization of electrons in Fenton systems.

Comparative study of metal nanoparticles anchored TiO2 using polyoxometalate intermediate in photodegradation of azo dye pollutant in aquatic environments

Herein, metal nanoparticles (Au, Ag, and Pt) are locally deposited on TiO2 with an UV-switchable polyoxometalate intermediate to achieve highly active photocatalyst nanohybrids. The successful preparation of these nanohybrids was confirmed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), Zeta potential (ZP), and UV–visible spectroscopy. TEM images showed the anchoring of metal nanoparticles of an average size of 20 nm on the TiO2 surface. A comparative study revealed that the bandgap energy was reduced in the order of Pt@PW-TiO2 (2.90 eV) > Ag@PW-TiO2 (2.95 eV) > Au@PW-TiO2 (3.05 eV). Likewise, the photocatalytic efficiency of fabricated nanohybrids was investigated in the degradation of reactive blue 19 (RB19), an azo dye model, under UV–visible light illumination and different experimental conditions. Optimal photodegradation occurred at pH = 3.8 with 0.33 gL−1 of photocatalyst exposed to light for 60 min. Under optimal conditions, the maximum and minimum photodegradation abilities were observed using Pt and Au deposited hybrids. A kinetic study of RB19 photodegradation was also conducted, resulting in pseudo-first order reaction rate constants of 0.0203, 0.025, and 0.0808 min−1, respectively, for the Au@PW-TiO2, Ag@PW-TiO2, and Pt@PW-TiO2 nanohybrids. Finally, the most probable mechanism for RB19 degradation using prepared photocatalysts is presented.

Insights into the electron transfer mechanisms of peroxydisulfate activation by modified metal-free acetylene black for degradation of sulfisoxazole

Herein, a modified metal-free acetylene black (MMF-AB) catalyst was synthesized by a simple solvothermal-calcination method and designed successfully to activate peroxodisulfate (PDS) for the degradation of sulfisoxazole (SIZ). Due to the doping of N, S and O metal-free elements, the modified catalyst showed excellent catalytic performance with 100% SIZ removal within 30 min. Pseudo first-order reaction rate constants (evaluating catalytic efficiencies and activity) of MMF-AB (kobs = 0.105 min−1) was 3 times higher than pure-AB (kobs = 0.029 min−1). Interestingly, it was demonstrated that the reaction system is based on the transfer of electrons from SIZ to PDS to realize an electron-transfer-based mechanism by the evidence of premixing, electron paramagnetic resonance (EPR) spectroscopy, salt-bridge experiments and electrochemical analyses. The introduction of recyclable filtration device solved the secondary pollution caused by the dispersion of the powdered catalyst in the treated water, which further proved the practicality and superiority of the MMF-AB catalyst.

Hydroxyl radical-driven transformations of bisphenol A and 2,4-dinitroanisole: Experimental and computational analysis.

This study used experimental and computational analysis to investigate the advanced oxidation of bisphenol A (BPA) and 2,4-dinitroanisole (DNAN). The pseudo first-order reaction rate constants depended on the molar peroxide ratio and were between 0.13 and 0.28 min-1 for BPA and between 0.018 and 0.032 min-1 for DNAN. The kinetic differences appear to be due in part to the energy requirements for oxidation, which depended on the reaction mechanism but were typically lower for BPA than they were for DNAN. Density functional theory (DFT) was used to develop transformation pathways that included experimentally-detected byproducts. The most energetically favored pathway for BPA oxidation begins with the formation of hydroxylated derivatives, while for DNAN, the most energetically favorable degradation pathway begins with the substitution of the methoxy group. Overall, these findings demonstrate the power of combining experimental and computational tools to reveal transformation mechanisms during water treatment. PRACTITIONER POINTS: Advanced oxidation transformations for two emerging water pollutants, bisphenol A and dinitroanisole, was investigated. The observed reaction kinetics depended on molar peroxide ratio in a manner that is in keeping with previous findings. Density functional theory-based analysis revealed reaction energy requirements and degradation pathways.

Calcium oxide nanoparticles: Biosynthesis, characterization and photocatalytic activity for application in yellow tartrazine dye removal

Dyes are substances that have a high polluting potential, due to their low biodegradability and chemical stability, causing serious environmental damage when disposed of incorrectly. Yellow tartrazine (YT) dye as an environmental liability requires attention, since it causes toxic effects in fish (Danio rerio) with a potential allergic effect in humans. In this context, the present study aims to synthesize and characterize calcium oxide nanoparticles (CaO-NPs) to evaluate the photocatalytic activity for the YT photodegradation under visible irradiation. CaO-NPs were synthesized by the biosynthesis method from golden linseed (Linum usitatissimum L.) extract. Central Composite Rotational Design (CCRD 23) was used to determine the ideal condition for the photocatalytic tests. X-ray diffraction (XRD), zeta potential (ZP), physical adsorption of N2, zero charge point (pHzcp), Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), Scanning Electron Microscopy by Energy Dispersive Spectroscopy (SEM-EDS), Diffuse Reflectance Spectroscopy (DRS) and Field Emission Gun – Scanning Electron Microscope (FEG-SEM) were used to the CaO-NPs characterization. Thus, CaO-NPs presented SBET = 14±0.02 m2g−1, Dp = 20.9±0.02 nm and Vp = 0.054±0.004 cm3g−1, characteristic of a mesoporous material. ATR-FTIR spectrum showed characteristic stretches of specific functional groups (–CH, –CO, C = C, Ca-O, –OH) from plant extract and metallic precursor. CaO-NPs showed pHZCP equal to 7.74, positive surface charge (+12.7 mV) and bang gap energy of 2.61 eV. FEG-SEM micrographs showed that has a small agglomeration with defined morphology, but with irregular particle size (around 48 nm), and SEM-EDS micrographs showed an elemental composition (in weight) of the 50.24% oxygen, 3.32% magnesium, 2.29% iron, 10.44% calcium, 14.07% silicon, 3.33% aluminum and 0.63% potassium. Regarding CCRD 23, the ideal condition was the pH = 7.0, [CaO-NPs] = 1.2 g/L and [YT] = 20 mg/L, with 76.2% of photodegradation and a pseudo first-order reaction specific reaction rate k = 0.089 min−1. After V cycles of CaO-NPs recycling, there was a decrease of around 22.83%, indicating a saturation of the active sites available in the nanocatalyst Therefore, CaO-NPs showed potential application for TY photodegradation to be used in wastewater treatment being an alternative nanocatalyst, meeting nanotechnology and sustainable development.

Cobalt-loaded carbon nanotubes boosted aerobic ciprofloxacin transformation driven by sulfide: A comprehensive mechanism investigation

Sulfide oxidation under aerobic conditions can produce active oxygen for the transformation of organic pollutants in aquatic environments. However, the catalytic performance of transition metal-supported carbon material on this process is poor understood. This study found that Co-loaded carbon nanotubes (CNTs) was able to realize the efficient aerobic transformation of antibiotic ciprofloxacin (CIP) by sulfide, with the pseudo-first order reaction rate constant improved from 0.013 h−1 without catalyst to 0.44–0.71 h−1 with 100 mg/L Co-loaded CNTs. Singlet oxygen (1O2) was the main active specie playing key roles in the process of CIP aerobic transformation with presence of Co-loaded CNTs. Mechanism studies indicated that the excellent electron transfer ability of Co-loaded CNTs might play an important role to promote the electron transfer and facilitate the formation of intermediate H2O2 and 1O2. Additionally, the Co-loaded CNTs/sulfide system effectively reduced the acute toxicity of organic pollutant, and Co-loaded CNTs showed remarkable cycling stability and negligible leaching. This study gives a better understanding for the Co-loaded CNTs mediated aerobic antibiotics transformation by sulfide, and provide a reference for the application of Co-loaded carbon materials on organics aerobic transformation by sulfide.

Photocatalytic degradation of gentamicin using TiO2 nanoparticle driven by UV light irradiation

Antibiotics have contributed to enhance life expectancy in underdeveloped countries by reducing mortality rate, but the hazards connected with antibiotic pollution are largely harming people. The photocatalytic degradation of gentamicin utilizing Titanium oxide nanoparticles (TiO2nps) using visible and UV light has been studied. TiO2nps was synthesized using the co-precipitation method and calcined at 600 °C. XRD study confirmed the phase formation and Raman study confirmed the structure of TiO2nps. UV–Vis’s absorption study was performed in which a broad peak was obtained between 300 and 600 nm. The degradation percentage for the photocatalytic study was found to be 51 %, 84 %, and 95 % under dark, visible light, and UV light, respectively. The pseudo-first order reaction rate constant was calculated for the sample exposed to UV light, and was found to be 0.0158. In the cyclic study, high degradation percentage of more than 80 % was obtained even after four cycle of degradation.

Effect of frequency and power on the piezocatalytic and sonochemical degradation of dyes in water

For the very first time, the effect of frequency on the piezocatalytic degradation of dyes has been systematically evaluated. To achieve this, a combination of systems and experimental setups operating at different ultrasonic frequencies ranging from 20 kHz up to 1 MHz were used. In addition, the effect of ultrasonic power was investigated at a low ultrasonic frequency of 20 kHz and higher ultrasonic frequency of 576 kHz to shed more light into the controversial discussion surrounding the ‘true’ mechanisms behind piezocatalysis. The results revealed that mechanical effects derived from acoustic cavitation, predominant at lower ultrasonic frequencies (<100 kHz), indeed enhanced the piezocatalytic degradation of the dye, Rhodamine B, to some extent (from 53% to 64% RhB degradation after 2 h). However, it was again demonstrated that sonochemical production of radicals remains a significant contributor for the overall degradation of the dye. Moreover, at higher ultrasonic frequencies (>100 kHz), the chemical effects derived from acoustic cavitation were so remarkable, that it raised the question of whether a piezocatalyst is really necessary when the optimisation of frequency and power may be enough for sonochemistry to fully degrade organic pollutants at a fast rate (pseudo first-order degradation reaction rate constant up to 0.037 min−1).

Single atom Co-anchored nitrogen‑doped graphene for peroxymonosulfate activation with high selectivity of singlet oxygen generation

Singlet oxygen (1O2) is an excellent active species generated in advanced oxidation processes (AOPs) that exhibits high selectivity, long life and wide pH tolerance. Therefore, catalysts for highly efficient and selective generation of 1O2 in AOPs would be highly desirable. This study developed a single atom Co-anchored nitrogen‑doped graphene (CoSAC-NG), which showed excellent catalytic performance for peroxymonosulfate (PMS) activation and bisphenol A degradation, with the pseudofirst-order reaction rate constant improved from 8.13 × 10−4 min−1 without catalyst to 4.42 × 10−2 min−1 with 5 mg L−1 CoSAC-NG. Mechanism studies indicated that CoSAC-NG selectively enhanced 1O2 generation, which was the dominant active specie for pollutant degradation. Moreover, the CoSAC-NG/PMS system effectively reduced the acute toxicity of pollutant, and CoSAC-NG exhibited remarkable cycling stability and negligible leaching. This study develops a new catalyst with high selectivity for 1O2 generation and provides a reference for application of single atom catalyst in PMS-based AOPs.

Generation of adsorbed atomic hydrogen by Pd(II) doped Fe(OH)2 enables ultra-fast reductive dechlorination of trichloroethylene

Trichloroethylene (TCE) is a notorious persistent pollutant in groundwater, while most reductive dechlorination processes result in the formation of toxic less-chlorinated by-products. In this work, adsorbed atomic hydrogen (H*) was produced by Pd(II) doped Fe(OH)2, which was used for ultra-fast reductive dechlorination of TCE without the formation of less-chlorinated by-products. When the Fe(OH)2 dosage is 0.5 mM and the Pd(II) dosage is 20 μM, TCE (42 μM) is completely removed in 60 min with the pseudo first-order reaction rate constant of 7.74 h−1. Radical quenching experiment and electrochemical analysis both confirmed that adsorbed H* rather than absorbed H* contribute to the reduction of TCE. Density function theory calculation demonstrated that small Pd clusters were more beneficial to TCE dechlorination than large Pd clusters. The pseudo first-order rate constant for TCE reduction in real groundwater was as high as 0.018 min–1, demonstrating the potential application of Pd/Fe(OH)2 in groundwater remediation.

Hydrogen Evolution Reaction By Metal-Free Poly-Neutral Red Electrocatalyst

While electric power supply by renewable sources such as solar and wind has become viable for their significant cost reduction, its intermittency demands urgent development of large scale storage technologies. Although conversion of electrical energy into storable hydrogen via electrolysis of water is ideal, noble metals and their oxides are used as electrocatalysts for their activities and stabilities. Alternative electrocatalysts out of abundant elements are needed for sustainable technological development.Recently, some metal-free organic conductive polymers with hydrogen-bonding capabilities were found to exhibit high electrocatalytic activities towards hydrogen evolution reaction (HER) [1,2]. We have succeeded electropolymerization of neutral red (NR) resulting in a formation of conductive poly-NR (PNR) that shows a relatively high HER catalytic activity [3]. PNR possesses hydrogen-bonding N atoms as annelated in the phenazine aromatic system as well as those in the amino substituents. Electrochemical analysis combined with in situ spectroscopy as well as DFT calculation was performed to clarify the mechanism and kinetics of HER electrocatalysis by PNR.This films of PNR were obtained by electropolymerization on F-doped SnO2 coated conductive glass (FTO, Asahi Glass) and SIGRATHERM® GFA5 Carbon felt with potential cycling between -0.2 and 1.2 V (vs. Ag/AgCl) at 50 mV s-1 for 50 times in a 5 mM NR - 0.1 M H2SO4 aqueous solution under N2. Polyaniline (PANI) was also obtained by the same method for comparison. The HER catalysis was evaluated by linear sweep voltammetry (LSV) in a 1 M trifluoromethanesulfonic acid (TfOH) under N2. The film samples were characterized by Fourier transform infrared spectroscopy (FT-IR), UV-visible spectroscopy. In-situ UV-visible spectroelectrochemical monitoring of the reaction intermediate was carried out to determine the rate of HER.PNR undergoes a pseudo-reversible reduction that shifts -61.8 mV/pH under acidic conditions and HER takes off right at this point (Fig. 1, a). Coupling of the same number of protons / electrons is expected as the electrochemical stoichometry from the observed Nernstian relationship, namely, resulting in a singly reduced PNR-H or doubly reduced PNR-H2 as depicted in Fig. 1 b. Protonation of N atoms was reasonably expected and also supported by the DFT calculation. The hydrogen atoms stabilized in the reaction intermediate can be associated to release H2 (Tafel mechanism) to complete the cycle of electrocatalysis of HER.Reduction of PNR in fact is associated with a color change. The broad reddish absorption of PNR peaking at around 500 nm attenuates to change the color to a pale yellow by constantly applying -0.15 V vs. RHE to produce PNR-H and/or PNR-H2 state as shown in Fig. 1c. Gradual recovery of the original red PNR was observed under open circuit under N2, associated with the H2 release. Thus, the rate of the spectral change is analyzed to determine the rate of the Tafel process. Pseudo-first order reaction rate law can be applied as proton is abundant and its concentration is constant, so that the rate of HER (r H2) is simply described as the rate of consumption of PNR-H and/or PNR-H2 as, r H2=-dC PNR-H2/dt =-kt (1)The ratio of PNR-H and PNR-H2 as compared to their initial amount (x PNR-red) was defined from the absorbance at 545 nm before and after reduction as, x PNR-red = C PNR-red/C 0-PNR-red = exp (-kt) (2)Good fitting of the experimental data was obtained to yield a pseudo-first order reaction rate constant of 9.98×10-4 s-1 for this rate-limiting step.

Enhanced degradation of sulfamethazine in boron-doped diamond anode system via utilization of by-product oxygen and pyrite: Mechanism and pharmaceutical activity removal assessment

Treatment of antibiotic contaminants from water has become an urgent problem due to that antibiotic pollution may threaten the ecosystem. This study explored the feasibility of enhancement of boron-doped diamond (BDD) anode system for antibiotic removal by utilization of by-product oxygen and natural pyrite catalyst. Sulfamethazine (SMZ), one of commonly detected antibiotics in the aquatic environment, was selected. Completed degradation of SMZ was achieved within 60 min, when 3 g/L pyrite was added into BDD-nickel foam (NiF) electrochemical system. The pseudo first-order reaction rate constant for SMZ degradation in BDD-NiF-pyrite electrochemical system was approximately 9 times higher than that in BDD-NiF electrochemical system. The optimal conditions of BDD-NiF-pyrite electrochemical system for SMZ degradation were: current intensity of 50 mA, pyrite dosage of 3 g/L, initial pH = 3, and reaction time of 60 min at room temperature (25 ± 1 ℃). The OH and O2− radicals were responsible for SMZ degradation. SMZ degradation intermediates were identified. Possible SMZ degradation pathways were also proposed. Furthermore, in vivo pharmaceutical activity removal of SMZ was assessed by zebrafish inflammation model. SMZ before treatment exhibited anti-inflammatory activity while lost it after treatment. This study offered an alternative approach to boost the BDD electrochemical oxidation of antibiotic-contaminated water.

Study on the mechanism and kinetics of amine with steric hindrance absorbing CO2 in non-aqueous/aqueous solution

Several alkanolamines (1A2P, 2A1P, AMP, MAE, EAE, and IPAE) were selected to study the steric hindrance effect on reaction kinetics between amine and CO2 in ethanol and aqueous solutions. Pseudo first-order reaction rate constant k0 was measured by the stopped-flow apparatus. Zwitterion mechanism was applied to describe the reaction and the k0 was well fitted by the corresponding kinetic model with average absolute relative deviation (AARD) in a range of 1.08%-3.89%. Apparent second-order reaction rate constant KA revealed that the reaction rate is simultaneously controlled by steric hindrance and pKa of amines. Additional alkyl groups increase the steric hindrance of amines and accelerate the decomposition of zwitterions. As a result, the reaction rate decreases with stronger steric hindrance effect. The larger pKa is conducive to a better proton receiving of amine. This leads to an acceleration of the deprotonation reaction of zwitterion intermediate. In addition, the relative influence of steric hindrance and pKa on the reaction kinetics is also related to the solvent environment.

Toward enhanced visible-light photocatalytic dye degradation and reusability of La3+ substituted ZnFe2O4 nanostructures

The present work focused on the synthesis of novel ZnLaxFe2−xO4 catalysts (x = 0, 0.01, 0.03, 0.05) and their utilization for the photocatalytic degradation of Rhodamine B dye. Structurally, the band gap energy of the catalysts tended to decrease (1.94–1.70 eV) with increasing the amount of La3+ dopant. ZnLa0.05Fe1.95O4 had an average particle size (40 nm), high surface area (41.07 m2 g−1) and large pore volume (0.186 cm3 g−1). Moreover, the effect of doping ratio, reaction time, H2O2 concentration, catalyst loading on the treatment performance of La3+ substituted ZnFe2O4 nanocomposites was investigated. ZnLa0.05Fe1.95O4/H2O2 system exhibited the highest degradation efficiency of 99.5% and nonlinear pseudo first-order kinetic reaction rate (14.8 × 10−3 min−1) in the presence of visible light irradiation. The key role of reactive oxygen species involving •O2− and •OH radicals was well explained through the scavenger study. A plausible mechanism of the degradation of Rhodamine B dye was also proposed. Due to two advantageous points including high recyclability (up to 4 cycles) and stability, La3+ substituted ZnFe2O4 nanocomposites can be an effective and competitive catalyst for the visible light-driven photodegradation of toxic dyes in the real wastewaters.

Solar light photocatalytic transformation of heptachlorobiphenyl (PCB 180) using g-C3N4 based magnetic porous photocatalyst

A novel porous core-shell magnetic β-cyclodextrin/graphitic carbon nitride photocatalyst (Mβ-CD/GCN) was synthesized and employed in a solar light driven catalytic system for the degradation of polychlorinated biphenyls (PCBs). The Mβ-CD/GCN display superior photocatalytic performance on account of porous structure and ultrathin GCN nanosheets design, the former improves the utilization of visible light by multiple scattering and reflection of incident light, and the latter accelerates electron transfer. The ultrahigh specific surface area (1255 m2 g−1) of Mβ-CD/GCN provided a large number of active sites for adsorption and degradation of the target pollution. The pseudo-first order reaction rate constant (kobs) for the degradation of PCB180 by Mβ-CD/GCN was 0.021 min−1, which improved 3.23 times than the bulk GCN. Additionally, the effects of various reaction parameters and water matrices were studied on the degradation of PCB180. Three possible degradation pathways and mechanism of PCB180 were speculated according to the identification of reaction intermediates and detection of reactive species. The solar light driven Mβ-CD/GCN catalytic technology is a promising method not only for the control of persistent organic pollutants (POPs), but also the catalyst could be recovered and reused through simple magnetic separation.

Degradation Characteristics of Carbon Tetrachloride by Granular Sponge Zero Valent Iron.

Granular sponge zero valent iron (ZVI) was employed to degrade carbon tetrachloride (CCl4). The effects of acidic washing, initial solution pH, and ZVI dosage on CCl4 degradation were investigated. Results showed that CCl4 was effectively removed by ZVI and approximately 75% of CCl4 was transformed into chloroform through hydrogenolysis. The rate of chloroform transformation was slower compared to that of CCl4, resulting in chloroform accumulation. CCl4 degradation was a pseudo first-order process. The observed pseudo first-order reaction rate constant (kobs) for CCl4 and chloroform were 0.1139 and 0.0109 h−1, respectively, with a ZVI dosage of 20 g/L and an initial CCl4 concentration of 20 mg/L. Surface acidic washing had a negligible effect on CCl4 degradation with ZVI. The kobs for CCl4 degradation increased linearly with increasing ZVI dosage and the optimal dosage of ZVI was 20 g/L based on the surface area-normalized rate constants. The negative relationship between kobs and the solution pH indicated that the degradation of CCl4 by ZVI performed better under weakly acidic conditions.

The Kinetics Investigation of CO2 Absorption into TEA and DEEA Amine Solutions Containing Carbonic Anhydrase

Tertiary amines have been used as alternative absorbents for traditional primary and secondary amines in the process of carbon capture. However, the carbon dioxide (CO2) absorption rates in these kinds of amine are relatively slow, which implies greater investment and construction costs and limits the large-scale application of carbon capture. Carbonic anhydrase (CA) is considered to be an ideal homogeneous catalyst for accelerating the rate of CO2 into aqueous amine solution. In this work, CO2 absorption combining CA with two single aqueous tertiary amines, namely triethanolamine (TEA) and 2-(diethylamino)ethanol (DEEA), was studied by use of the stopped-flow apparatus over temperature ranging from 293 to 313 K. The concentrations of selected aqueous amine solution and CA used in the experiment were ranging among 0.1–0.5 kmol/m3 and 0–50 g/m3 , respectively. Compared to the solution without the addition of CA, the pseudo first-order reaction rate in the presence of CA (k0,withCA) is significantly increased. The values of k0,withCA have been calculated by a new kinetics model. The results of experimental and calculated k0,amine and k0,withCA in CO2-amine-H2O solutions were also investigated,respectively.

Synthesis of g-C3N4-C60 fullerene nanowhisker composites and its photocatalytic activity for degradation of rhodamine B

Graphitic carbon nitride (g-C3N4) was prepared from melamine (C3H6N6) by annealing it under an electric furnace at 550 °C for 3 h. The g-C3N4 solution was prepared by dissolving powdered g-C3N4 in an aqueous solution with polyvinyl pyrrolidone (PVP). The liquid–liquid interfacial precipitation (LLIP) method was used to prepare the g-C3N4–C60 fullerene nanowhisker composites from g-C3N4 solution, C60-saturated toluene, and isopropyl alcohol (IPA). X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and transmission electron microscopy were used to characterize the g-C3N4–C60 fullerene nanowhisker composites. These were further used for the photocatalytic degradation of rhodamine B (RhB) under ultraviolet (at 254 and 365 nm) irradiation. In addition, UV–vis spectroscopy was utilized to confirm the photocatalytic degradation activity of RhB over the g-C3N4–C60 fullerene nanowhisker composites. Under UV irradiation, the kinetics of photocatalytic degradation of RhB using g-C3N4–C60 fullerene nanowhisker composites followed a pseudo first-order reaction rate law.

Removal of Aqueous Para-Aminobenzoic Acid Using a Compartmental Electro-Peroxone Process

The presence of emerging contaminant para-aminobenzoic acid (PABA) in the aquatic environment or drinking water has the potential to harm the aquatic ecosystem and human health. In this work, the removal of aqueous PABA by a compartmental electro-peroxone (E-peroxone) process was systematically investigated from the kinetic and mechanism viewpoints. The results suggest that single electrolysis or ozonation was inefficient in PABA elimination, and the combined E-peroxone yielded synergistic target pollutant degradation. Compared to the conventional E-peroxone oxidation, the sequential cathodic reactions, followed by anodic oxidations, improved the PABA removal efficiency from ~63.6% to ~89.5% at a 10-min treatment, and the corresponding pseudo first-order kinetic reaction rate constant increased from ~1.6 × 10−3 to ~3.6 × 10−3 s−1. Moreover, the response surface methodology (RSM) analysis indicated that the appropriate increase of inlet ozone concentration, applied current density, initial solution pH value, and solution temperature could accelerate the PABA degradation, while the excess of these operational parameters would have a negative effect on the treatment efficiency. The comparation tests revealed that the coupling of electrolysis and ozonation could synergistically produce hydroxyl radicals (HO•) and the separation of cathodic reactions and anodic oxidations further promoted the HO• generation, which was responsible for the enhancement of PABA elimination in the compartmental E-peroxone process. These observations imply that the compartmental E-peroxone process has the potential for aqueous micropollutants elimination, and the reaction conditions that favor the reactive oxygen species generation are critical for the treatment efficiency.

Heterogeneous activation of peroxymonosulfate by Co3O4 loaded biochar for efficient degradation of 2,4-dichlorophenoxyacetic acid

Carbon-based catalysts have the advantage of biological cleaning and cost-effectiveness in water treatment. This work used a two-step calcination method to prepare a novel nanometer composite material (CBC-1), where flake-like Cobalt oxide (Co 3 O 4 ) loaded on rice husk biochar. CBC-1 was used to activate PMS and degrade 2,4-dichlorophenoxyacetic acid (2,4-D) in the water phase. SEM, XRD, FT-IR, BET, XPS, EPR and other characterization methods showed that both sulfate radical and hydroxyl radical were involved in 2,4-D degradation. Both the high hydroxyl (-OH) content and Co (II) of the catalyst are beneficial to the activation of PMS. The pseudo-first order reaction rate constant of CBC-1 was 5.3 and 16 times that of pure Co 3 O 4 and biochar. This research provides new ideas for the application of carbon-based materials in the water treatment process and achieves the goals of treating waste water polluted by pesticides effectively and resource utilization of agricultural waste. • Provided a new view for the waste utilization of rice husk. • Enhanced the catalytic activity of Co 3 O 4 with rice husk biochar added. • CBC-1/PMS system exhibited satisfactory degradation efficiency of 2,4-D within 10 min. • The higher hydroxyl content of CBC-1 is helpful for enhancing the catalytic ability.