P-nitrophenol In Solution Research Articles

Synergistic Degradation of 4-Nitrophenol Using Hydrodynamic Cavitation in Combination with Hydrogen Peroxide

p-Nitrophenol (PNP), a widely utilized intermediate, is a persistent pollutant present in industrial effluent streams. The inherent toxicity of PNP necessitates its treatment before releasing it in the environment. The conventional approach pertaining to degradation of PNP is based on chemical and biological methods for decomposition. Alternatively, Hydrodynamic Cavitation (HC) is emerging as a promising technology for waste water treatment. This study investigates HC as an alternative technology to degrade PNP and subsequently enhance efficiency by varying involved parameters. The HC-H2O2 system is reported to exhibit synergism for pollutant oxidation, the applicability of which is also investigated for degrading PNP. A PNP solution of fixed concentration was subjected to HC using a circular Venturi. Degradation was studied by varying time, pressure, pH and H2O2 concentration. Decompostion of p- Nitrophenol was quantified by UV-Visible Spectroscopy at 405nm. Degradation of PNP was observed to be directly proportional to time at constant pressure and an initial increase in pressure led to higher degradation. However, on achieving a peak decomposition level, the extent of decomposition declined with further increase in pressure. Experiments done at acidic pH resulted in over two times the decomposition than those done at basic pH. The PNP- H2O2 system exhibited 91% more degradation than the sum of degradations affected by PNP and H2O2 individually. Moreover, subjecting PNP:H2O2 in a molar ratio of 1:5 to HC resulted in near-complete (>95%) degradation. This study proposes variations of parameters for optimum decomposition of PNP using HC and explores the HC-H2O2 system as a promising alternative for the degradation PNP.

A rotating disk study of the photocatalytic oxidation of p-nitrophenol on phosphorus-modified TiO2 photocatalyst

After discussing the general aspects of photocatalytic oxidation of organic compounds in aqueous solutions and the application of the rotating disk theory to (photo)catalytic phenomena, we report the oxidation of p-nitrophenol (PNP) on illuminated phosphorus modified TiO2 (P-TiO2) and TiO2 photocatalysts under controlled hydrodynamic conditions. We found that the performance of the oxygen transfer reaction can be described considering mass transport in solution and surface reaction according to Langmuir–Hinshelwood kinetics. From analysis of the dependence of the reaction rate on the rotation rate, we obtained the apparent organic–photocatalyst adduct interaction constant K, the rate constant k of the surface reaction between adsorbed PNP and hydroxyl radicals, and the diffusion coefficient D of PNP in solution. The results showed that degradation of PNP using P-TiO2 and UV light was readily possible, with reaction half-lives significantly lower than those obtained using pristine TiO2 photocatalyst.

Atmospheric Pressure Plasma Jet in Organic Solution: Spectra, Degradation Effects of Solution Flow Rate and Initial pH Value

The organic compounds of p-nitrophenol (PNP) solution was treated by the active species generated in a stirred reactor by an atmospheric pressure plasma jet (APPJ). The emission intensities of hydroxyl (OH), oxygen (O), nitric oxide (NO), hydrogen (H) and molecular (N2) were measured by optical emission spectroscopy (OES). The relations between the flow rates of the PNP solution and degradation, the degradation effects and initial pH value of the solution were also investigated. Experimental results show that there exist intense emissions of O (777.1 nm), N2 (337.1 nm), OH (306–310 nm) and NO band (200–290 nm) in the region of plasma. Given the treatment time and gas flow rate, the degradation increased as a function of discharge energy and solution flow rate, respectively. The solution flow rate for the most efficient degradation ranged from 1.414 m/s to 1.702 m/s, and contributed very little when it exceeded 2.199 m/s. This indicates the existence of diffusion-controlled reactions at a low solution flow rate and activation-controlled reactions at a high solution flow rate. Moreover, increasing or decreasing the initial pH value of neutral PNP solution (pH=5.95) could improve the degradation efficiency. Treated by APPJ, the PNP solutions with different initial pH values of 5.95, 7.47 and 2.78 turned more acidic in the end, while the neutral solution had the lowest degradation efficiency. This work clearly demonstrates the close coupling of active species, photolysis of ultraviolet, the organic solution flow rate and the initial pH value, and thus is helpful in the study of the mechanism and application of plasma in wastewater treatment.

Ozonation of p-nitrophenol at different pH values of water and the influence of radicals at acidic conditions

Ozonation of p-nitrophenol solution was carried out without pH control and at constant pH values of 2, 7 and 10. The effect of radical scavenger t-butanol at pH 2 was studied for t-butanol concentrations of 0.0, 0.000225, 0.00225 and 0.0225mol/dm3. The ozone decomposition rate was computed for each pH as a function of time on the basis of each experimental run. The consumed ozone dose was calculated at each pH and at each t-butanol concentration at pH 2. The results indicate that pH determines the relative production rates of the first intermediates, hydroquinone and 4-nitrocathecol, on the reaction path of p-nitrophenol decomposition and that radicals play an important role in ozonation at low pH. The results also indicate that there exists some optimum t-butanol concentration at which slowest 4-nitrocathecol production occurs, and further, there exists some optimum t-butanol concentration for highest consumed ozone dose per amount of decomposed p-nitrophenol at pH 2.

Removal of p-aminophenol and p-nitrophenol from aqueous solution through adsorption on bismuth, lead, and manganese ferrocyanides and their relevance to environmental issues

Removal of p-aminophenol (PAP) and p-nitrophenol (PNP) from aqueous solution have been studied through adsorption on bismuth, lead and manganese ferrocyanides (125 μm British Sieve Standard mesh size) at pH range 1.0–10.0 and room temperature (27 ± 1°C). The progress of adsorption was followed spectrophotometrically by measuring the absorbance of PAP and PNP solutions at their corresponding λmax = 220 and 330 nm, respectively. At neutral pH, PNP was found to more adsorbed than PAP on all three metal ferrocyanides studied. Manganese ferrocyanide and bismuth ferrocyanide were found to have maximum and minimum adsorption, respectively for both adsorbents. The adsorption followed the Langmuir type of adsorption in the concentration range of 10−4 to 10−5 mol/L of PAP and PNP solutions.

Research on Macro Cyclic Polyamine Complexes of Transition Metal and Catalytic Properties

This article Synthesis of carbohydrate ligands of coordination ability, to react with metal Chlorides to get more stable complexes, and elemental analysis, infrared, Ultraviolet Spectroscopic characterization and analysis of nuclear magnetic resonance. Characterization of its structure and study on the hydrolysis activity of pnitrophenyl picolinate lipid and the activity of pnitrophenol solution of phosphate, disodium macrocyclic polyamine catalyzed by macrocyclic polyamine metal complexes. The results show that the effect of hydrolytic activity of macrocyclic polyamine complexes is much larger than the hydrolysis activity of ordinary metal complexes; it can be important significance to find a better way of cutting nucleic acid by hydroxylation.

Synthesis of Cu<sub>2</sub>O/NiFe<sub>2</sub>O<sub>4</sub> Magnetic Complex and its Application in Photocatalytic Degradation <sup></sup>

In order to enhance the re-collecting ability of Cu2O, Cu2O/NiFe2O4 magnetic complex was synthesized in this paper. XRD patterns showed the prepared material was the complex of Cu2O and NiFe2O4. The saturation magnetization (Ms) of Cu2O/NiFe2O4 magnetic complex was 12.056emu/g. The Cu2O/NiFe2O4 magnetic complex was used for the decolorization of P-nitrophenol solution in a photocatalytic degradation reactor under the visible light irradiation. In this work, the Cu2O/NiFe2O4 magnetic complex is recycled for 3 times, and the decomposition rates are all above 60%. The XRD also showed that the Cu2O/NiFe2O4 complex was neither oxidized nor deoxidized in the photocatalytic degradation process. It can be concluded that the prepared Cu2O/NiFe2O4 complex can be recycled applied to photocatalytic degradation treatment.

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.

Radiation-induced catalytic degradation of p-nitrophenol (PNP) in the presence of TiO 2 nanoparticles

The gamma radiation induced catalytic degradation of p-nitrophenol (PNP) in the presence of titanium dioxide (TiO 2) nanoparticles in aqueous solution was investigated. The initial concentration of PNP solution was 50 mg/L, and the additional TiO 2 doses were 0, 0.5, 1.0, and 2.0 g/L. The experimental results indicated that the PNP decomposition kinetics conformed to the modified pseudo-first order reaction equation under all applied conditions. When the TiO 2 dose was in the range of 0–2.0 g/L, the effect of additional TiO 2 on PNP decomposition rate was not obvious because PNP could be removed quite well by irradiation even in the absence of TiO 2 nanoparticles; however, the removal of total organic carbon (TOC) and total nitrogen (TN) was significantly accelerated in the presence of TiO 2 nanoparticles, the TOC removal efficiency increased from about 16% to 42%, and therefore the mineralization of PNP could be enhanced by TiO 2 nanoparticles. The inorganic nitrogen products were quantitatively measured to estimate the decomposition degree of PNP. The major aromatic intermediates, as well as carboxylic acids were identified by LCMS and IC. Possible reactions involved in radiation induced catalytic decomposition of PNP in aqueous solutions were proposed.

Sorption of Agrochemical Model Compounds by Sorbent Materials Containing β-cyclodextrin

ABSTRACT Polymeric sorbent materials that incorporate β-cyclodextrin (CD) have been prepared and their sorption behavior toward two model agrochemical contaminant compounds, p-nitrophenol (PNP) and methyl chloride examined. The sorption of PNP was studied in aqueous solution using ultraviolet-visible (UV-Vis) spectroscopy, whereas the sorption of methyl chloride from the gas phase was studied using a Langmuir adsorption method. The sorption results for PNP in solution were compared between granular activated carbon (GAC), modified GAC, CD copolymers, and CD-based mesoporous silica hybrid materials. Nitrogen porosimetry at 77 K was used to estimate the surface area and pore structure properties of the sorbent materials. The sorbents displayed variable surface areas as follows: copolymers (36.2–157 m2/g), CD-silica materials (307–906 m2/g), surface modified GAC (657 m2/g), and granular activated carbon (∼103 m2/g). The sorption capacities for PNP and methyl chloride with the different sorbents are listed in descending order as follows: GAC > copolymers > surface modified GAC > CD-silica hybrid materials. In general, the differences in the sorption properties of the sorbents were related to the following: (i) surface area of the sorbent, (ii) CD content and accessibility, (iii) and the chemical nature of the sorbent material.

Gamma radiation-induced degradation of p-nitrophenol (PNP) in the presence of hydrogen peroxide (H 2O 2) in aqueous solution

The synergistic effect of gamma radiation with hydrogen peroxide (H 2O 2) for p-nitrophenol (PNP) decomposition in aqueous solution was evaluated. The PNP solution with initial concentration of 50 mg/L was irradiated in the presence of extra H 2O 2 at initial concentration of 0, 20, 40, and 80 mg/L. The experimental results showed that the decomposition of PNP conformed to the pseudo-first-order reaction kinetics under the applied conditions. When initial H 2O 2 concentration was in the range of 0–80 mg/L, higher concentration of H 2O 2 was more effective for the decomposition, mineralization and nitrogen release of PNP. However, the removal of total organic carbon (TOC) and total nitrogen (TN) was not as effective as that of PNP. Ammonia and nitrate were detected as the main inorganic nitrogen products of PNP decomposition without extra H 2O 2, whereas nitrate was considered as a final inorganic nitrogen product with extra H 2O 2 in the initial concentration range of 0–80 mg/L. Major decomposition products, including organic acids were identified by LC/MS and IC. Possible pathways for PNP decomposition by gamma radiation in aqueous solution were proposed.

The utilization of bathocuproinedisulfonic acid as a reagent for determining d-glucose and d-galactose levels in glycoconjugates

A sensitive, rapid, and reliable method for measuring d-glucose and d-galactose levels in glycoconjugates has been developed. In this method, the NAD(P)H produced from the enzymatic oxidation of the monosaccharides is reacted with a CuSO 4-bathocuproinedisulfonic acid reagent (Cu-BCS) to produce a color complex absorbing maximally at 486 nm. With galactose dehydrogenase and glucose dehydrogenase serving as the model enzymes, graphs of absorbance versus varying d-glucose or d-galactose concentrations yielded a linear plot from 2.5 to 250 nmol of sugar. Using this procedure, sugar released by acid hydrolysis from lactose, porcine submaxillary mucin and raffinose was quantified. When p-nitrophenyl-α- d-glucopyranoside and p-nitrophenyl-β- d-galactopyranoside were acid hydrolyzed and assayed with the Cu-BCS reagent, the amount of sugar released from each of the p-nitrophenyl compounds was found to be equal to the levels of p-nitrophenol in solution. This method is easy to use and with minor modifications can be employed for the quantification of d-glucose and d-galactose in other glycoconjugates.

Preparation and characteristics of carbon-supported platinum catalyst and its application in the removal of phenolic pollutants in aqueous solution by microwave-assisted catalytic oxidation

Granular activated carbon-supported platinum (Pt/GAC) catalysts were prepared by microwave irradiation and characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). Pt particles dispersing onto the surface of GAC could be penetrated by microwave and acted as “reaction centre” in the degradations of p-nitrophenol (PNP) and pentachlorophenol (PCP) in aqueous solution by microwave-assisted catalytic oxidation. The reaction was carried out through a packed bed reactor under ambient pressure and continuous flow mode. Under the conditions of microwave power 400 W, influent flow 6.4 mL min −1 and air flow 120 mL min −1, phenolic solutions with high concentration (initial concentrations of PNP and PCP solutions were 1469 and 1454 mg L −1, respectively) were treated effectively by Pt/GAC, 86% PNP and 90% PCP were degraded and total organic carbon (TOC) removal reached 85% and 71%, respectively. Compared with GAC, loaded Pt apparently accelerated oxidative reaction so that Pt/GAC had a better degrading and mineralizing efficiencies for PNP. Hydraulic retention time was only 16 min in experiment, which was shortened greatly compared with catalytic wet air oxidation. Pyrolysis and oxidation of phenolic pollutants occurred simultaneously on the surface of Pt/GAC by microwave irradiation.

Micro-emulsion-assisted synthesis of ZnS nanospheres and their photocatalytic activity

ZnS nanospheres with rough surface were synthesized by using a micro-emulsion-assisted solvothemal process. The molar ratio of [water]/[surfactant] played an important role in controlling the size of the ZnS nanospheres. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), field emission-scanning electron microscope (FE-SEM), and selected area electron diffraction (SAED) were used for the characterization of the resulting ZnS nanospheres. A possible formation mechanism was proposed. These ZnS nanospheres exhibited a good photocatalytic activity for degradation of an aqueous p-nitrophenol solution and the total organic carbon (TOC) of the degradation product has also been investigated.

Solvation ofp-Nitrophenol at a Water/Alkane Interface: The Role of Ionic Strength and Salt Identity

Second harmonic generation (SHG), a surface specific, nonlinear optical spectroscopy, was used to study the interfacial solvation of a neutral surfactant, p-nitrophenol (PNP), adsorbed to the water/cyclohexane interface in the presence of simple salts at varying salt concentrations. The purpose of this work was to determine what relationship (if any) exists between interfacial polarity and bulk solution ionic strength. Data show an apparent red shift in SHG spectra with an increase in salt anion size from fluoride to chloride to bromide at 1 M salt concentrations. A spectral red shift of the PNP electronic excitation implies an increase in local polarity. Within experimental limits, however, these observed interfacial spectral shifts mimic shifts in absorbance spectra observed for PNP in bulk electrolyte solutions. Given the similarities between bulk and surface behavior, we conclude that observed shifts in SHG spectra may be attributed to effects similar to those found in bulk solution. Additionally, the surface adsorption of PNP to the water/cyclohexane interface was studied to determine the surface distribution of PNP and the conjugate base, p-nitrophenoxide (PNP(-)), for a 10 mM PNP solution. PNP adsorption is favored over PNP(-) adsorption by a factor of 10, giving rise to an equilibrium surface distribution that is an order of magnitude greater than that found in bulk solution. These findings indicate that the amount of PNP(-) at the surface in an aqueous solution of 10 mM PNP is negligible.

Microwave assisted wet oxidation of p-nitrophenol

Aqueous solution of p-nitrophenol (PNP) was treated continuously by microwave assisted wet oxidation while flowing through a granular activated carbon (GAC) fixed bed. PNP was pre-adsorbed onto GAC prior to being put into the reactor so as to prevent PNP adsorption on GAC during microwave irradiation. PNP solutions with different initial concentration (218.6 mg/L and 1200 mg/L) were treated under conditions of microwave power 500 W, liquid flow 6.4 mL/min and air flow 40 mL/min or 60 mL/min. The results indicated that the removal of PNP was higher than 90% and more than 65% PNP was mineralized. Phenol, nitrobenzene, hydroquinone and benzoquinone occurred as course products during the operation process, which were degraded further. The biodegradability of the outflow was improved greatly by microwave assisted wet oxidation.

Incorporation of Cyclodextrin into Mesostructured Silica

The incorporation of cyclodextrin (CD) groups inside mesoporous silica frameworks was attempted using two methods: by the grafting of the CD groups into the channels of preformed mesoporous silica hosts and by the direct synthesis of CD-containing mesoporous materials by a one-step process. While the grafting procedure failed to incorporate CD groups inside the pore channels of mesoporous silica substrates, the direct synthesis approach yielded materials whose physical and chemical characteristics (as determined by X-ray diffraction, N2 sorptometry, transmission electron microscopy, and elemental analysis) were indicative of the presence of CD groups inside the pore channels of the materials. The CD-containing mesoporous materials, denoted as CD-HMS, were prepared by the co-condensation of tetraethoxysilane and a silylated derivative of β-cyclodextrin in the presence of a structure-directing dodecylamine surfactant solution. Materials with CD group loadings up to 0.39 mmol g-1 and uniform pore channels with diameters in the range of 38−42 Å were prepared by this method. Preliminary adsorption experiments using aqueous p-nitrophenol solutions showed that the CD-HMS materials were promising for the removal of organic compounds from water.

Influence of the Regeneration Temperature on the Phenols Adsorption on Activated Carbon

Adsorption from aqueous solutions of p-nitrophenol and p-chlorophenol on activated carbon regenerated by wet oxidation after saturation of the same adsorptive has been studied. The adsorption behaviors have been analyzed with the help of a scheme of double Langmuir, which gives information of the induced modifications on different parts of the surface by the regeneration treatment. Also, differences in the adsorption uptake and free energy have been obtained depending on the adsorptive and on the temperature at which wet oxidation was done. From the point of view of a higher uptake capacity after regeneration it has been found that 170°C is the best suited temperature for wet oxidation.

The Use of Cavitating Jets to Oxidize Organic Compounds in Water

Exposure to ultrasonic acoustic waves can greatly enhance various chemical reactions. Ultrasonic acoustic irradiation of organic compounds in aqueous solution results in oxidation of these compounds. The mechanism producing this behavior is the inducement of the growth and collapse of cavitation bubbles driven by the high frequency acoustic pressure fluctuations. Cavitation bubble collapse produces extremely high local pressures and temperatures. Such conditions are believed to produce hydroxyl radicals which are strong oxidizing agents. We have applied hydrodynamic cavitation to contaminated water by the use of submerged cavitating liquid jets to trigger widespread cavitation and induce oxidation in the bulk solution. Experiments were conducted in recirculating flow loops using a variety of cavitating jet configurations and operating conditions with dilute aqueous solutions of p-nitrophenol (PNP) of known concentration. Temperature, pH, ambient and jet pressures, and flow rates were controlled and systematically varied. Samples of the liquid were taken and the concentration of PNP measured with a spectrophotometer. Experiments were conducted in parallel with an ultrasonic horn for comparison. Submerged cavitating liquid jets were found to generate a two order of magnitude increase in energy efficiency compared to the ultrasonic means. [S0098-2202(00)00303-5]

Hydrogen-bonding-based thermochromic phenol-amine complexes

Variable-temperature UV–vis, 13C NMR and IR studies showed that proton-transferred complexes were formed between phenols and amines in apolar solvents at low temperature. Upon cooling a solution of p-nitrophenol and diisopropylamine in toluene, the colour of the solution changed from colourless to yellow. This thermochromism was ascribed to the proton transfer in the hydrogen-bonding complex. Under UV–vis conditions, butylamine and imidazole also caused similar thermochromism upon complexation with p-nitrophenol, while triethylamine, quinuclidine and pyridine did not. The thermochromic behaviour was particularly dependent on the stoichiometry of the amine and the phenol: a solution of 3,3′-dibromo-5,5′-dinitro-2,2′-biphenyldiol and diisopropylamine with a molar ratio of 1:1 showed no thermochromism, while solutions with 1:2 or higher ratios showed thermochromism, indicating that excess amine is required to obtain the proton-transferred species. These results revealed that the proton-transferred species forms in apolar solvents at low temperature if an appropriate hydrogen-bonding network between the phenol and the amine can stabilize it. © 1998 John Wiley & Sons, Ltd.