P-nitrophenol Degradation Rate Research Articles

In-situ growth of Ni3S2@Mo2S3 catalyst on Mo-Ni foam for degradation of p-nitrophenol with a good synergetic effect by using ozone

In this study, Ni3S2@Mo2S3 composites were grown on the surface of molybdenum-nickel (Mo-Ni) foam in situ by a one-step hydrothermal method. With p-nitrophenol (PNP) as the target pollutant, the catalyst can produce a good synergistic effect with ozone, and the degradation rate of PNP is more than 96%. Even after five cycles, Ni3S2@Mo2S3-NF/O3 was able to degrade PNP efficiently and stably. In addition, the unique three-dimensional structure of Ni3S2@Mo2S3-NF solves the separation and recycling problem of traditional powder catalysts by maintaining the structural stability during the use process and thus, may reduce the cost of water treatment. The degradation process is mainly dominated by non-radical pathways, and the radical pathway, which work synergistically. This work reveals the influencing factors and degradation mechanism of Ni3S2@Mo2S3-NF/O3 system for PNP degradation, which provides a new idea for water treatment and broadens its potential application.

Optimization of PNP Degradation by UV-Activated Granular Activated Carbon Supported Nano-Zero-Valent-Iron-Cobalt Activated Persulfate by Response Surface Method.

Nitrophenols are toxic substances that present humans and animals with the risk of deformities, mutations, or cancer when ingested or inhaled. Traditional water treatment technologies have high costs and low p-nitrophenol (PNP) removal efficiency. Therefore, an ultraviolet (UV)-activated granular activated carbon supported nano-zero-valent-iron-cobalt (Co-nZVI/GAC) activated persulfate (PS) system was constructed to efficiently degrade PNP with Co-nZVI/GAC dosage, PS concentration, UV power, and pH as dependent variables and PNP removal rate as response values. A mathematical model between the factors and response values was developed using a central composite design (CCD) model. The model-fitting results showed that the PNP degradation rate was 96.7%, close to the predicted value of 98.05 when validation tests were performed under Co-nZVI/GAC injection conditions of 0.827 g/L, PS concentration of 3.811 mmol/L, UV power of 39.496 W, and pH of 2.838. This study demonstrates the feasibility of the response surface methodology for optimizing the UV-activated Co-nZVI/GAC-activated PS degradation of PNP.

Theoretical and experimental insight into plasma-catalytic degradation of aqueous p-nitrophenol with graphene-ZnO nanoparticles

This paper aims to investigate plasma-catalytic degradation of p-nitrophenol (PNP) with graphene-ZnO nanoparticles based on theoretical and experimental perspects. The graphene-ZnO nanoparticles were firstly prepared by hydrothermal process, which were then systematically characterized with scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectrum, UV–Vis spectrophotometer, X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption desorption analyzer. Combined with the analysis of Discrete Fourier Transform (DFT), the morphology, structure, specific surface area, absorption light range and electron transfer of the prepared catalyst are described in detail. The prepared graphene-ZnO nanocomposites displayed larger specific surface area and wider light absorption range. The charge could be transferred from ZnO to graphene. The catalytic degradation performace was further examined. Results indicated that degradation rate of PNP was enhanced from 68.5% to 80.2% with ZnO, which could futher improved to 97.6% with graphene (6%)-ZnO nanocomposites. The prepared samples exhibited good stability. Active species including OH, O2–, HO2, 1O2, h+ and e- played crucial role in PNP degradation. The degradation pathways were proposed based on DFT calculation and relevant literatures. Lastly, ECOSAR algorithm illustrated that the toxicity of PNP can be relieved after plasma-catalytic treatment.

Removal of P-Nitrophenol by Nano Zero Valent Iron-Cobalt and Activated Persulfate Supported onto Activated Carbon

P-nitrophenol (PNP), a highly toxic carcinogen, is very stable due to its benzene structure. Advanced oxidation technology is becoming the main means for degrading it. A nano iron-cobalt (Co-nZVI) catalyst, supported by granular activated carbon (GAC), was prepared using liquid-phase reduction, and sodium persulfate’s (PS’s) potential to degrade PNP was studied. The Co-nZVI/GAC nanocomposites were classified, and effects of PS dosage, Co-nZVI/GAC dosage, material system type, PNP concentration, initial pH, and material reuse rate on the reaction were investigated. Activated carbon successfully supported iron and cobalt. At 1 mmol/L of PS, the maximum PNP degradation rate was 99.19%, which was unachievable at other dosages. With only Co-nZVI/GAC present, the rate was 69.8%; with activated persulfate present, it increased to 99.19%. The activated PS system was relatively stable under acidic conditions. Catalysis was induced by adding Co-nZVI/GAC (1.5 g/L). When added four times, the catalytic rate was 57%. Liquid chromatography–mass spectrometry (LC-MS) showed that PNP degradation involves the transfer of PNP to p-benzoquinone (PBQ), the main activators being iron(II) and iron(III) and the key active substances being sulfate (SO42−) and hydroxide (·OH). In conclusion, Co-nZVI/GAC-activated PS effectively removes PNP.

Cl/S co-doped carbon nitride nanotube clusters effectively drive the metal-free photo-Fenton reaction under visible light: A new ROS conversion mechanism

In this work, we used Cl/S co-doped carbon nitride nanotube clusters (Cl/S-TCN) photocatalyst to effectively drive the metal-free photo-Fenton (MF-PF) reaction. The synergistic effect of Cl/S-TCN and H2O2 made MF-PF(Cl/S-TCN) system have excellent degradation performance for organic wastewater in a wide pH range (3–9). The optimal amount of H2O2 was only 10 mM, the degradation rate of p-nitrophenol (p-NP) by MF-PF(Cl/S-TCN) system under neutral conditions can be increased from 50.3% to 98.2%, the degradation rate of tetracycline (TC) reached more than 90% within 20 min, and the COD removal rates of domestic sewage and oilfield produced water reached 70.3% and 82.6% accordingly. MF-PF(Cl/S-TCN) system had excellent stability, and the performance loss was less than 0.7% after four cycles of experiments. Density functional theory calculations showed that Cl and S dopants accelerated the separation of photogenerated electrons and holes on the surface of Cl/S-TCN. These photogenerated electrons and holes, were used as electron donors and electron acceptors for reacting with H2O2, destroyed the O–O bond and O–H bond of H2O2, and finally converted H2O2 to •OH and •O2− with strong oxidation, which is the key to enhance the performance of MF-PF(Cl/S-TCN) system. Such reaction pathway was rarely reported in previous studies.

Simultaneous Degradation of p-Nitrophenol and Recovery of Copper from Wastewater in Electrochemical Reactor Under High Salinity

Ti/RuO2–IrO2electrode was used in this study as an anode, while titanium plate (Ti) was used as a cathode for electrochemical oxidation process, to explore the influences of related parameters on degradation of p-nitrophenol (PNP) and removal of Cu2+from mixed simulated wastewater. Using a single chamber reactor, we tested the influence of various factors on the PNP degradation and Cu2+elimination. The factors that were tested are as follow; the type of electrolyte, density of the current, various values of pH and different concentrations of Cu2+. Furthermore, a dual-chamber diaphragm reactor compartmentalized by cationic membrane was utilized to explore the removal mechanism of PNP and Cu2+. Results showed that, treatment of PNP-Cu2+simulated wastewater, with NaCl as electrolyte, had a better effect compared with Na2SO4, which had characteristics such as shorter reaction time and higher degradation efficiency for PNP. Removal of Cu2+had no obvious advantage over Na2SO4. The degradation of PNP and removal of Cu2+were improved with increased current density when the rang was increased from 10 to 40 mA/cm2. Cu2+concentration when increased initially promoted the degradation of PNP. At the same time, Cu2+acted as electron acceptor at the cathode that slowed down the consumption of H+through reduced combination of H+with electrons. The degradation rate of PNP decreased with increased initial pH, but the Cu2+was opposite. In this experiment, the degradation of PNP was positively correlated with indirect oxidation of active chlorine, and the Cu2+was removed by cathodic electrodeposition.

Hexagonal carbon nitride microtube doped with tungsten and nitrogen vacancies: Photocatalytic hydrogen evolution and efficient Fenton-like photocatalytic degradation of p-nitrophenol

It has been found that the element doping and vacancy defects of the carbon nitride framework enhance its photocatalytic performance. In this article, we newly designed hexagonal carbon nitride microtube (W-TCN) with tungsten-doped and nitrogen vacancies in a layered stack structure through hydrothermal and in situ calcination methods. It is used to activate the high-efficiency Fenton-like photocatalytic degradation of peroxymonosulfate (PMS) and further studied the photocatalytic hydrogen evolution performance. Combining the Fenton-like process with photocatalysis driven by simulated sunlight, a cooperative catalytic system is realized to quickly remove p-nitrophenol (PNP) in water pollution. The prepared tubular W-TCN catalyst has excellent sunlight utilization efficiency, large surface area, abundant nitrogen vacancies, and narrow band gap due to the introduction of tungsten. These factors are conducive to the enhanced catalytic activity of W-TCN catalyst. Cyclic experiments and parallel experiments proved that the catalyst has good long-term stability. In particular, the degradation rate of PNP reached 98.6% under 90 min of irradiation in the optimal reaction system (W-TCN/PMS). Moreover, the hydrogen evolution performance of W-TCN catalyst is further studied, and it is found that in the presence of sacrificial agent, W-TCN also had a certain amount of hydrogen evolution, which is 91.46 μmol. The research ideas of this article proves that by adjusting the photocatalytic properties of carbon nitride materials, it has broad prospects in repairing environmental pollution under the synergistic effect of Fenton-like and photocatalysis. At the same time, further material optimization also has certain potential in solving the energy crisis.

A facile electroless preparation of Cu, Sn and Sb oxides coated Ti electrode for electrocatalytic degradation of organic pollutants

Electrocatalytic degradation of organic pollutants is an encouraging technology for wastewater treatment. To achieve practical application, electrode plate with cost effective fabrication, high catalytic efficiency and long service life is urgently required. This work prepared a CuO-SnO2-SbOX electrode on Ti substrate, which is achieved by ultrasonic assisted deposition of Cu layer, followed by electroless deposition of SnSb layer and finalized by calcination at 500 °C. The obtained electrode (Ti/CuO-SnO2–SbOX) exhibited high catalytic degradation activity and a high oxygen evolution potential (OEP) of 2.13 V, which is 0.4 V greater than that of the widely recognized Ti/SnO2–SbOX electrode. The oxygen evolution reaction (OER) models of active oxygen intermediate adsorption was optimized by density functional theory (DFT) calculations. The results revealed that (1) the ΔG of the OER rate-determining step was raised to 2.30 eV after Cu doping on 101 plane; (2) binding energies of the optimized surface with reactive oxygen species (ROS) were substantially decreased. Furthermore, the as-prepared electrode has a high yield of hydroxyl radical generation as evidenced by terephthalic acid detection. The potential for hydroxyl radical generation was measured to be 1.8 V at pH = 12 and 2.6 V at pH = 2.The catalytic degradation rate of methylene blue (MB) follows pseudo first order reaction kinetics, and the reaction constant K value reached 0.02964 -k/min−1, twice as much as that obtained from electrodeposition electrode (Ti/Cu/SnO2–SbOX). A degradation rate of 94.6% was achieved for MB in 100 min in the first run, and the value remained over 85% in the subsequent 10 runs. At the same conditions, the degradation rate of p-nitrophenol was over 90% in 100 min and complete mineralization was achieved in 4 h.

P-nitrophenol degradation by pine-wood derived biochar: The role of redox-active moieties and pore structures

Biochar can both adsorb and degrade p-nitrophenol (PNP); however, the PNP degradation mechanism has not been well investigated. We prepared two biochars at pyrolysis temperatures of 500 °C (B500) and 700 °C (B700). Although B500 showed much stronger free radical signals (which are associated with organic degradation, according to previous studies), the apparent PNP degradation was approximately 3 times higher in the B700 system. The degradation increased significantly after the biochars were washed with water. According to a quantitative analysis of the sorption and degradation and two-compartment first-order kinetics modeling of the apparent removal kinetics, sorption occurred mainly in the initial period, whereas degradation continued throughout the removal process. The PNP degradation rate constant depended mainly on the external surface area at a relatively low concentration (200 mg/L) and was controlled by the microporous surface area at a relatively high concentration (800 mg/L). In addition, the apparent degradation did not depend on the biochar particle size. Therefore, PNP degradation may be related to the three-dimensional structure of the biochar in addition to the exposed external surface. The well-developed pore structure, more accessible surface, and larger electron exchange capacity of B700 may promote electron transfer between the biochar and PNP, and thus accelerate PNP degradation. This study demonstrates that various properties of the biochar may contribute to PNP degradation.

Degradation of high-concentration p-nitrophenol by Fenton oxidation.

This work aimed to degrade high-concentration p-nitrophenol (PNP) by Fenton oxidation. We studied various reaction parameters during Fenton oxidation, such as the iron dosage (as Fe2+), the initial concentration and temperature of PNP, and the dosage of hydrogen peroxide (H2O2), especially the influence of temperature on the PNP degradation rate and degree. Under the addition of the same molar ratio of H2O2/Fe2+ and H2O2 dosage according to the theoretical stoichiometry, the PNP degradation rate and the removal rate of total organic carbon (TOC) increased significantly with the increase in the initial PNP concentration. Moreover, the oxidative degradation effect was significantly affected by temperature. The increased reaction temperature not only significantly reduced the Fe2+ dosage, but also greatly promoted the removal rate of chemical oxygen demand (COD) and TOC, and improved the utilization efficiency of H2O2. For example, when the initial concentration of PNP was 4,000 mg·L-1, and the dosage of Fe2+ was 109 mg·L-1 (H2O2/Fe2+ = 200), the removal rates of COD and TOC at 85 °C reached 95% and 71% respectively. Both were higher than the 93% COD removal rate and 44% TOC removal rate when the dosage of Fe2+ was 1,092 mg·L-1 (H2O2/Fe2+ = 20) at room temperature.

Degradation of organic contaminants through the activation of oxygen using zero valent copper coupled with sodium tripolyphosphate under neutral conditions

In this study, sodium tripolyphosphate (STPP) was used to promote the removal of organic pollutants in a zero-valent copper (ZVC)/O2 system under neutral conditions for the first time. 20 mg/L p-nitrophenol (PNP) can be completely decomposed within 120 min in the ZVC/O2/STPP system. The PNP degradation process followed pseudo-first-order kinetics and the degradation rate of PNP gradually increased upon the decreasing ZVC particle size. The optimal pH of the reaction system was 5.0. Our mechanism investigation showed that Cu+ generated by ZVC corrosion was the main reducing agent for the activation of O2 to produce ROS. ·OH was identified as the only ROS formed during the degradation of PNP and its production pathway was the double-electron activation of O2 (O2→H2O2→·OH). In this process, STPP did not only promote the release of Cu+ through its complexation, but also promoted the production of ·OH by reducing the redox potential of Cu2+/Cu+. In addition, we could initiate and terminate the reaction by controlling the pH. At pH < 8.1, ZVC/O2/STPP could continuously degrade organic pollutants; at pH > 8.1, the reaction was terminated. STPP was recycled to continuously promote the corrosion of ZVC and O2 activation as long as the pH was <8.1. This study provided a new and efficient way for O2 activation and organic contaminants removal.

Experimental investigation of ultrasound/ Fenton’s reagent oxidation process on the degradation rate constant of p- nitrophenol

هدف اصلی این پژوهش بررسی اثربخشی ترکیب روش فنتون و سونوشیمی با فرکانس بالا برای تصفیه پساب شامل p- نیتروفنول (PNP) به عنوان ماده آلاینده است. این روش‌ها برای تخریب PNP در سیستم ناپیوسته تحت شرایط عملیاتی مختلف بر اساس فرآیند افراصوت، فنتون، فراصوت/ پروکسید هیدروژن و فرآیند فراصوت / فنتون مورد استفاده قرار گرفته اند. این راکتور شامل شش ترنسدیوسر فراصوت با فرکانس 7/1 مگاهرتز بود. سه ترنسدیوسر در کف و سه ترنسدیوسر دیگر در دیواره رآکتور قرار داشتند. نتایج نشان داد که تجزیه PNP از واکنش شبه درجه اول تبعیت می کند. ثابت نرخ تخریب برای پارامترهای عملیاتی مختلف شامل pH، توان الکتریکی ورودی به ترنسدیوسرها و غلظت و حجم های مختلف H2O2 و FeSO4 تعیین شد. در شرایط بهینه، بیشترین میزان تخریب PNP برای ترکیب فراصوت و واکنش فنتون (min-1 166/0) با ضریب هم افزایی 165/1 بدست آمد. اولویت های بعدی مربوط به فنتون، فراصوت/ پراکسید هیدروژن و فراصوت با ثابت نرخ تخریب min-1 137/0، 0107/0 و 0055/0 بود. بنابراین فرآیند فراصوت / فنتون دارای بالاترین توانایی برای تخریب PNP بود، زیرا فراصوت می تواند واکنش فنتون را برای تولید رادیکال های هیدروکسیل تشدید کند.

Glucose and Applied Voltage Accelerated p-Nitrophenol Reduction in Biocathode of Bioelectrochemical Systems

p-Nitrophenol (PNP) is common in the wastewater from many chemical industries. In this study, we investigated the effect of initial concentrations of PNP and glucose and applied voltage on PNP reduction in biocathode BESs and open-circuit biocathode BESs (OC-BES). The PNP degradation efficiency of a biocathode BES with 0.5 V (Bioc-0.5) reached 99.5 ± 0.8%, which was higher than the degradation efficiency of the BES with 0 V (Bioc-0) (62.4 ± 4.5%) and the OC-BES (59.2 ± 12.5%). The PNP degradation rate constant (kPNP) of Bioc-0.5 was 0.13 ± 0.01 h-1, which was higher than the kPNP of Bioc-0 (0.024 ± 0.002 h-1) and OC-BES (0.013 ± 0.0005 h-1). PNP degradation depended on the initial concentrations of glucose and PNP. A glucose concentration of 0.5 g L-1 was best for PNP degradation. The initial PNP increased from 50 to 130 mg L-1 and the kPNP decreased from 0.093 ± 0.008 to 0.027 ± 0.001 h-1. High-throughput sequencing of 16S rRNA gene amplicons indicated differences in microbial community structure between BESs with different voltages and the OC-BES. The predominant populations were affiliated with Streptococcus (42.7%) and Citrobacter (54.1%) in biocathode biofilms of BESs, and Dysgonomonas were the predominant microorganisms in biocathode biofilms of OC-BESs. The predominant populations were different among the cathode biofilms and the suspensions. These results demonstrated that applied voltage and biocathode biofilms play important roles in PNP degradation.

Ni-doped mesoporous carbon obtained from hydrothermal carbonization of cellulose and their catalytic hydrogenation activity study

Ni-doped spherical mesoporous carbon catalysts (Ni/C n ) were prepared via one-pot hydrothermal carbonization of microcrystalline cellulose (MCC) with nickel acetate as the Ni source. This exhibited a high conversion rate for p-nitrophenol (PNP) hydrogenation to p-aminophenol (PAP). The obtained catalysts contained 0.87–6.84 wt% nickel content that primarily consisted of metallic nickel, with a small amount of nickel oxide. The Ni additive could be beneficial in the formation of the mesoporous structure. The results showed that as the Ni content increased, the mesoporous percentage increased. The doped Ni was monodispersed particles added into the carbon skeleton with an average particle size of 23.6 nm. They were surrounded by ordered striped carbon that exhibited a graphite-like structure. The catalytic hydrogenation reaction took place at normal temperatures and pressure exhibited high catalytic activity. The degradation rate of PNP reached 99.7% when 0.30 g of the Ni/C0.2-900 catalysts was used for a reaction time of 40 min, with corresponding apparent rates constant of 1.68 × 10−3 S−1, apparent activation energy of only 43.25 kJ/mol.

Hydrodynamic cavitation of p-nitrophenol: A theoretical and experimental insight

Abstract This paper presents a theoretical and experimental study of cavitation as an advanced oxidation process. The degradation rate of p-nitrophenol (PNP) was experimentally investigated and used as an estimator of the sonochemical effect in hydrodynamic cavitation. The PNP initial concentration was varied in the range 0.1–1 g L−1 and the pressure in the range 0.2–0.7 MPa, with a corresponding flow rate of 3.5–6.9 L min−1. In terms of removal rate and energy efficiency, an optimal inlet pressure value was found close to 0.4 MPa and cavitation number of 0.25. The calculated first-order kinetic constant values show the existence of an optimal configuration: k = 1.13 × 10−2 min−1 at 0.45 MPa with a value for the electrical energy per order EEO = 66.7 kWh m−3. Moreover, the kinetic data was purged from the influence of the experimental apparatus configuration, allowing for the evaluation of an intrinsic kinetic constant. The physical–chemical behavior of hydrodynamic cavitation is discussed on the basis of single bubble dynamics. The numerical simulations, at different inlet pressures, provided a good explanation of the values observed. Furthermore, a simple energy balance on cavitating bubbles, taking into account for the actual production of cavitating events, gave a further confirmation of the experimental trends.

Degradation of p-nitrophenol by interior microelectrolysis of zero-valent iron/copper-coated magnetic carbon galvanic couples in the intermittent magnetic field

In this present paper, the copper-coated magnetic carbon (CCMC) was fabricated by pre-deposition of ferric ferrous oxides onto carbon particles and followed by the chemical deposition of copper. Galvanic couples composed of zero-valent iron and copper-coated magnetic carbon (Fe0/CCMC) were employed for the treatment of simulative wastewater containing p-nitrophenol (PNP). Under the optimized conditions such as magnetic induction intensity, mass ratio of Fe0/CCMC and initial pH, it was found that the degradation rate of PNP greatly increased due to the enhancement of the internal microelectrolysis of Fe0/CCMC couples in the intermittent magnetic field. In addition, the half-life value of COD of simulative wastewater containing PNP was used as a parameter to evaluate the degradation efficiency of PNP by interior microelectrolysis of zero-valent iron (Fe0), zero-valent iron/carbon (Fe0/C), zero-valent iron/magnetic carbon (Fe0/MC) and zero-valent iron/copper-coated magnetic carbon (Fe0/CCMC), respectively. It showed that the degradation efficiency of PNP by interior microelectrolysis of Fe0/CCMC was the highest among them. The degradation process could be described as a pseudo-first-order model and liquid chromatography–mass spectrometer (LC–MS) analysis showed that amino-phenol was an intermediate during the degradation of PNP.

Electricity generation using p-nitrophenol as substrate in microbial fuel cell

The cell voltage and degradation rate of p-nitrophenol (PNP) were monitored in a two-chambered microbial fuel cell (MFC) system. Degradation metabolites in the anode solution of MFC were analyzed by gas chromatography–mass spectrometry (GC–MS). PNP was used as substrate by the MFC that was inoculated with anaerobic sludge. The results showed that electricity output increased with the PNP concentration increased, the MFC displayed a maximum power density of 1.778 mW m−2 and a maximum PNP degradation rate of 64.69% when PNP was used as a sole substrate. However, the cell voltage and the PNP degradation rate with sodium acetate (402.3 mV and 95.96%) were higher than those fed with glucose (341.9 mV and 83.51%) when glucose and sodium acetate were used as a substrate, respectively. Furthermore, GC–MS analysis showed that the PNP was biodegraded completely after 142 h in the MFC. These results demonstrate that PNP can be used for electricity generation in MFC for practical applications of wastewater treatment.

Development of aerobic granules in sequencing batch reactor with p-nitrophenol as sole carbon source

The present study was aimed at the development of aerobic granules in sequencing batch reactor (SBR) for the biodegradation of p-nitrophenol (PNP). The reactor was started with 50 mg L−1 of PNP. Aerobic granules first appeared within 1 month of the start up of the reactor. The granules were large and strong and had a compact structure. The diameter of stable granules on day 200 was in the range of 2–3 mm. The integrity coefficient and granule density was found to be 98% and 1,031 kg m−3 respectively. The settling velocity of granules was found to be in the range of 3 × 10−2 to 4 × 10−2m s−1. The aerobic granules were able to degrade PNP up to 700 mg L−1 at a removal efficiency of 87%. Gas chromatography–mass spectrometry studies confirmed that the biodegradation of PNP occurred by an initial oxygenase attack that resulted in the release of nitrite and the accumulation of hydroquinone. The specific PNP degradation rate in aerobic granules followed the Haldane model for substrate inhibition. A high specific PNP degradation rate up to 0.872 g PNP g−1 VSS−1 d−1 was sustained up to PNP concentration of 200 mg L−1. Higher removal efficiency, good settling characteristics of aerobic granules, makes a SBR suitable for enhancing the microorganism potential for biodegradation of inhibitory compounds.

Kinetics of Ultrasound-Enhanced Oxidation of p-Nitrophenol by Fenton's Reagent

Aqueous solutions of p-Nitrophenol (PNP) were oxidized by Fenton's reagent assisted by ultrasound (US) irradiation. The effects of operating parameters such as initial medium pH, initial concentration of PNP, the molar ratio of Fe2+/H2O2, the temperature and the type of saturating gas on the degradation rates of PNP were investigated. The results showed that both pH value and PNP concentration altered noticeably the reaction rates, with preferred operation conditions at low pH, and low PNP concentration. Among the four different saturating gases (namely Ar, O2, air and N2), PNP degradation in an oxygen-saturated solution was the fastest. The addition of Fenton's reagent could increase the PNP removal rate. PNP degradation followed apparent pseudo-first-order kinetics under US irradiation, Fenton's reagent oxidation and the combined US/Fenton's reagent oxidation process. The overall reaction rates were significantly enhanced in the US/Fenton's reagent oxidation system, most likely because ultrasound could accelerate Fenton's reagent to generate hydroxyl radical (.OH) and other reactive oxygen intermediates. There was an obvious synergetic effect in the combined US-Fenton's reagent process. The observed synergetic effects of the US/Fenton's reagent system resulted in an increase in the net PNP degradation rate by a factor of 2.06.

Kinetics and mechanism of organic pollutants degradation with cobalt–bicarbonate–hydrogen peroxide system: Investigation of the role of substrates

The kinetics and mechanism of a simple system, Co 2+–HCO 3 −–H 2O 2 for degrading highly stable organic pollutants have been reported. Fast and versatile decolorization of organic dyes was observed in an aqueous solution containing 10 mM NaHCO 3, 10 μM Co 2+ ions and 10 mM H 2O 2, while the degradation rate of p-nitrophenol and 2,4-dinitrophenol was very slow. From cyclic voltammetry and UV–vis spectra, it was found that different complexes between Co 2+ ions and methylene blue (MB) were formed in HCO 3 − solution, and being confirmed by photoluminescence probing and electron spin resonance spin-trapping technologies, the 1:1 complex [Co II(HCO 3 −)(MB)] + was more efficient in catalyzing decomposition of H 2O 2 into OH radicals. The other tested pollutants also played an important role in the rate of OH radicals production in the system. Based on the kinetic observations of MB decolorization, a possible mechanism was proposed.