Degradation Of Acetic Acid Research Articles

Bioconversion of Alkali Pretreated Hazelnut Shells to Fermentable Sugars for Generation of High Value Products

Hazelnut shells are lignocellulosic by-products of hazelnut processing. As the shells are rich in cellulose and hemicellulose, they have high potential as a raw material for production of food enzymes, biofuel, and various chemicals (acetic acid, furfural and lignin degradation products) after bioprocessing. The objective of this study was to determine the effect of alkali pretreatment and enzymatic hydrolysis on production of fermentable sugars from hazelnut shells. The hazelnut shells were pretreated with sodium hydroxide (NaOH) at concentrations of 3–7 % (w/v) for 30–90 min at 121 °C. Pretreatments were evaluated measuring delignification, solid recovery and production of reducing sugars after enzymatic hydrolysis of the pretreated biomass. Up to 20 % lignin removal was achieved and the highest reducing sugar yield of 318.3 mg/g pretreated biomass (or 91.7 % enzyme conversion efficiency) was obtained from biomass pretreated with 3 % NaOH at a solid to liquid ratio of 1:20 for 60 min. The response surface model predicted the optimal reducing sugar production (357.2 mg/g pretreated biomass) under 3 % NaOH, 1:13 of solid to liquid ratio and 63 min of pretreatment period at 121 °C. Overall, the results of this study show a promise for hazelnut shells to be used in production of value-added products.

Thermal degradation capabilities of modified bio-chars and fluid cracking catalyst (FCC) for acetic acid

Fluid Cracking Catalyst (FCC) and three different modified bio-chars were tested for their thermal degradation capability of acetic acid in a custom-made continuous-flow reactor operated at 450 °C under nitrogen flow. The tested modified bio-chars were: switchgrass bio-char (BC), bio-char impregnated with nickel nitrate solution (BCNi), and bio-char deposited with iron oxide (BCFe). The modified bio-chars showed acetic acid degradation capability comparable to the FCC catalyst as quantified by total conversion. The total conversions were 5.55%, 17.33%, 15.21%, and 12.41% for the blank (no catalyst), modified bio-chars (BC and BCNi), and FCC catalyst, respectively while modified bio-char BCFe showed the highest conversion of 40.66%.

Mathematical analysis of the heterogeneous photo-Fenton oxidation of acetic acid on structured catalysts

In this paper, we analyse the model for the UV-C photo-Fenton degradation of acetic acid using \(LaFeO_{3}\) heterogeneous structured catalyst with a monolithic structure. The model is based on the occurrence of hydrogen peroxide photolysis and acetic acid oxidation in the heterogeneous phase, assumed first-order and Eley–Rideal type kinetics respectively. The main objective is to propose an analytical solution for the concentrations of \(\hbox {CH}_{3}\hbox {COOH}\) and \(\hbox {H}_{2}\hbox {O}_{2}\). A powerful analytical method called Homotopy Perturbation Method (HPM) has been employed to obtain approximate analytical solutions. The accuracy of the analytical solution is tested with the numerical solution. In this work the numerical solution of the problem is reported using SCILAB program. Stability Analysis of this model is also explained. The obtained analytical solution in comparison with the numerical and stability analysis is found to be in satisfactory agreement.

Degradation of Acetic Acid in Water Using Gas-Liquid Plasma with SPG Membrane

Degradation of Acetic Acid in Water Using Gas-Liquid Plasma with SPG Membrane

Titania modification with a ruthenium(II) complex and gold nanoparticles for photocatalytic degradation of organic compounds.

Titania of fine anatase nanoparticles (ST01) was modified successively with two components, i.e., a ruthenium(II) complex with phosphonic anchoring groups [Ru(bpy)2(4,4'-(CH2PO3H2)2bpy)](2+) bpy = 2,2'-bipyridine (Ru(II)CP) and gold nanoparticles (Au). Various compositions of two titania modifiers were investigated, i.e., Au, Au + Ru(II)CP, Au + 0.5Ru(II)CP, Ru(II)CP, 0.5Ru(II)CP and 0.25Ru(II)CP, where Au and Ru(II)CP correspond to 0.81 mol% and 0.34 mol% (with respect to titania), respectively. In the case of hybrid photocatalysts, the sequence of modification (ruthenium(II) complex adsorption or gold deposition) was investigated to check its influence on the resultant properties and thus photocatalytic performance. Diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM) were applied to characterize the structural properties of the prepared photocatalysts, which confirmed the successful introduction of modifiers of the ruthenium(II) complex and/or gold NPs. Different distributions of gold particle sizes and chemical compositions were obtained for the hybrid photocatalysts prepared with an opposite sequence. It was found that photocatalytic activities depended on the range of used irradiation (UV/vis or vis) and the kind of modifier in different ways. Gold NPs improved the photocatalytic activities, while Ru(II)CP inhibited the reactions under UV/vis irradiation, i.e., methanol dehydrogenation and acetic acid degradation. Oppositely, Ru(II)CP greatly enhanced the photocatalytic activities for 2-propanol oxidation under visible light irradiation.

Kinetic modeling of hemicellulose-derived biomass hydrolysis under high pressure CO2–H2O mixture technology

This work is focused on the development of kinetic models of hydrolysis of hemicellulose-derived wheat straw under high-pressure CO2–H2O technology. The experiments were performed at fixed temperature (180°C), varying pressure from 0 (water-only reaction), 20, 35 to 50bar of initial CO2 pressure and reaction times varied from 0 to 45min. The three accurate kinetic models allowed to describe the effect of reaction conditions mainly hitherto not studied CO2 pressure and reaction time on the concentration of intermediate compounds such as xylose and arabinose in both oligomer and monomer form as well as final compounds e.g. acetic acid, furfural and other degradation products. Modeling demonstrated that addition of CO2 plays an important role in kinetics study of hemicellulose fraction hydrolysis being the fastest step the polysaccharides’ hydrolysis into sugars in oligomer form. Even negligible amount of CO2 (20bar of initial pressure) improves the initial kinetic constant of aforementioned reaction by almost 40% in comparison to water-only process. Depletion of oligosaccharides’ concentration and counterbalanced production of monomer sugars were found for longer reaction times, achieving maximum faster for CO2-assisted than CO2-free processes. Moreover, the increase of initial CO2 pressure demonstrated to be highly efficient in enhancement of the kinetic constants of all reactions occurring in the liquors. The developed models demonstrated a good fitting to the experimental data albeit the complex composition of raw material as well as the multistep analytical process.

Degradation of acetic acid by heterogeneous Fenton-like oxidation over iron-containing ZSM-5 zeolites

In this study, the degradation of acetic acid was investigated by heterogeneous Fenton-like oxidation in the presence of iron-containing ZSM-5 zeolites. Iron content and Brønsted acidity of the catalyst affected positively and significantly the activity of catalyst in acetic acid (AA) degradation. The catalysts were prepared by ion-exchange method by using ZSM-5 type zeolites with different Si/Al ratio and characterized by XRD, SEM, FT-IR, ICP-AES and nitrogen adsorption measurements. The catalyst (IE-FeZSM-5 (90)) with Si/Al ratio of 42 and iron content of 8.5% (in wt) was found to be the most active catalyst in AA degradation. The influence of temperature, initial concentration of acid, amounts of H2O2 and catalyst and solution pH was investigated on degradation of AA by heterogeneous Fenton-like oxidation over this catalyst. Degradation of AA was accelerated at pH around 4 and temperature, H2O2 amount, catalyst loading and initial concentration of AA affected significantly the destruction of acid. The optimum conditions were obtained to be 0.2g of catalyst, 333K of temperature, solution pH of 4 and H2O2 amount of 8.35mmol for an AA concentration of 0.1g/dm3 with a COD removal of 50.5%. Degradation of AA obeyed first order kinetics with a rate expression of −rAA=2.56×107e−61.5/RTCAA where −rAA in mol/dm3min, R in kJ/mol.K, T in K and CAA in mol/dm3.

TiO2 modified with Ag nanoparticles synthesized via ultrasonic atomization-UV reduction and the use of kinetic models to determine the acetic acid photocatalytic degradation

TiO2 surfaces modified with noble metal nanoparticles have been found to effectively reduce the photogenerated carrier recombination rate and significantly extend the light absorption properties of TiO2, thereby greatly increasing its photocatalytic activity. In this paper, highly ordered, double-sided TiO2 nanotube arrays were prepared using an anodic oxidation method in a home-made reactor using glycerol/water (volume ratio 2:1) and NH4F (0.25mol/L) as the electrolyte, titanium plates (10cm×2cm×0.5mm) as the anode and graphite as the cathode at a constant voltage of 25V. After a 2-h reaction, anatase TiO2 nanotubes were obtained upon calcination at 450°C for 4h. The Ag nanoparticles on the surfaces of the TiO2 were prepared via ultrasonic atomization-ultraviolet light reduction. First, a silver nitrate solution was sputtered into small droplets under ultrasonication. Then, the Ag+ droplets were reduced to Ag nanoparticles. The surface morphologies, structures and elemental compositions were characterized using SEM, EDS, XRD and XPS. The photocatalytic activities were determined in acetic acid solutions (40–200mg/L), and a mathematical model for catalytic degradation was established based on a hyperbolic model. The SEM results showed that the diameters of the as-prepared Ag/TiO2 are approximately 100nm and that the lengths are approximately 1.8μm. The XRD crystal structure analysis shows that the anatase phase of the TiO2 does not change during the Ag modification, and there was a peak from Ag (220). The XPS determined that the Ag atom percentage was 1.11%. The degradation of acetic acid indicated that Ag/TiO2 has a higher photocatalytic activity than the undoped TiO2.

Lanthanide co-doped TiO2: The effect of metal type and amount on surface properties and photocatalytic activity

Abstract Preparation of new rare earth metal-containing TiO 2 nanocomposites (Nd 3+ /Er 3+ , Nd 3+ /Eu 3+ , Eu 3+ /Ho 3+ -TiO 2 ) using sol–gel route and their photoactivity under visible and ultraviolet light is reported. The obtained photocatalysts were subsequently characterized by Brunauer–Emmett–Teller (BET) method, UV–vis diffuse-reflectance spectroscopy (DRS), luminescence spectroscopy, X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction analysis (XRD). Photodegradation efficiency of phenol and acetic acid was estimated for visible light ( λ > 420 nm) and UV irradiation. It was found that introduced rare earth (RE) metals are presented in the form of metal oxides (RE 2 O 3 ) at TiO 2 surface. Our study demonstrated that Eu 3+ /Ho 3+ co-doped titania exhibited higher photocatalytic activity than P25 in phenol degradation under visible light, whereas Nd 3+ /Eu 3+ co-doped TiO 2 showed one of the highest activities in both phenol and acetic acid degradation reaction either under UV and visible light among all the rare earth doped samples. Action spectra analysis of the selected samples clearly showed that RE-doped TiO 2 could be excited under visible light in the range from 420 to 450 nm.

Magnetic resonance study of co-modified (Fe,N)-TiO2

Iron and nitrogen co-modified TiO2, nFe,N-TiO2 (n=1, 5 and 10wt.%), nanocomposites were prepared by impregnation of amorphous titanium dioxide with Fe(NO3)3 followed by high temperature calcination (800°C) in ammonia atmosphere. The nanocomposites exhibited high photocatalytic activity towards the degradation of acetic acid under visible light, with optimum performance for the n=5% sample. To obtain insight in the electronic properties of the co-modified photocatalysts underlying their visible light photocatalytic activity, the magnetic properties of the (Fe,N)-TiO2 nanocomposites have been investigated by FMR/EPR spectroscopy in 4–290K range. The FMR spectra of iron nanoparticle agglomerates were dominant in the whole temperature range for all samples, with the lowest intensity for 5Fe,N-TiO2 sample at RT. In addition, the EPR spectra of free radicals and trivalent titanium ions were recorded at low temperatures. The highest concentration of trivalent titanium ions was observed for n=5Fe,N-TiO2 and the lowest for n=10Fe,N-TiO2 sample. It is proposed that in the case of the former sample, the largest amount of iron is involved in the modification of titania, resulting in the appearance of the highest concentrations of trivalent titanium ions that correlates favorably with the optimum visible light photocatalytic reactivity.

Photocatalytic degradation of acetic acid on spinel ferrites MFe2O4 (M = Mg, Zn, and Cd)

Spinel ferrites MFe2O4(M=Mg, Zn, and Cd) with Fe(III) in a d5 electron configuration were prepared via a conventional solid-state reaction. The amount of CO2 generated by the photocatalytic degradation of acetic acid on these ferrites was measured under irradiation by a xenon lamp with a power of 300W. Photocatalytic degradation was observed for all the compounds, and the results revealed that MgFe2O4 exhibited the highest degradation, i.e., 196μmol/g/h. The degradation in the presence of MFe2O4(M=Mg, Zn, and Cd) increased with increasing heating condition.

Effect of Inorganic Ions on the Oxidative Efficiency of Ti(IV)-Catalyzed H2O2/O3 Process in the pH Range of 1.0 to 6.0

The oxidative efficiency of Ti(IV)-catalyzed H2O2/O3 (Ti(IV)/H2O2/O3) for acetic acid (HAc) degradation was investigated in the initial pH range of 1.0 to 6.0, and the effects of some common inorganic ions were also discussed in detail. The results showed that the effects of SO4 2− and NO3 − on the efficiency of Ti(IV)/H2O2/O3 were negligible. However, adding Br− greatly reduced the removal rate of HAc. The presence of Cl− also reduced the efficiency of Ti(IV)/H2O2/O3, but its negative effect became negligible in the initial pH range of 4.5 to 5.5. The presence of H2PO4 − could improve the removal rate of HAc, and addition of sodium carbonate had no influence on the efficiency of Ti(IV)/H2O2/O3 in the initial pH range of 4.5 to 5.5.

Photocatalytic Degradation of Phytotoxic Substances in Waste Nutrient Solution by Various Immobilized Levels of Nano-TiO2

The photocatalytic degradation effectiveness of six selected typical phytotoxic substances (ferulic, benzoic, gallic, salicylic, tannic, and acetic acid) by two levels of 10 nm TiO2 (11 and 22 g/m2) immobilized on tiles under 254 nm of UV light irradiation was investigated. The results showed that the immobilized nano-TiO2 significantly degraded all phytotoxic substances dissolved in distilled water, and the cumulative degradation rates of ferulic, benzoic, gallic, salicylic, tannic, and acetic acid reached 22.2, 33.6, 48.2, 56.9, 57.5, and 76.0 % after 6 h of treatment, respectively. Furthermore, the cumulative degradation rates of six phytotoxic substances by immobilized nano-TiO2 were different remarkably, i.e., salicylic acid > benzoic acid, gallic acid > ferulic acid, acetic acid > tannic acid. The maximal photocatalytic degradation efficiencies of all phytotoxic substances appeared at the first 2 h in the three experiments. During the 6-h treatment period, the photocatalytic degradation efficiency of all phytotoxic substances decreased gradually. There was no significant difference in the photocatalytic degradation of benzoic acid and ferulic acid between the two levels of immobilized nano-TiO2 treatments, whereas a significant difference was found in the photocatalytic degradation of salicylic acid, gallic acid, tannic acid, and acetic acid. In a word, nano-TiO2 photocatalysis is an effective method to degrade phytotoxic substances. And the photocatalytic degradation effectiveness of six typical phytotoxic substances may be related to their structures.

Mathematical modelling of the heterogeneous photo-Fenton oxidation of acetic acid on structured catalysts

This work focused on the development and the validation of a mathematical model for the UV-C photo-Fenton degradation of acetic acid using a LaFeO3 heterogeneous structured catalyst with a monolithic structure. A combined study of the evolved gases and the liquid phase was conducted. The experimental results led to the identification of the main reactions that occur in the system: the complete mineralisation of acetic acid by H2O2 due to the presence of the catalyst and the decomposition of H2O2 to water and O2 in the homogeneous phase. A mathematical model was then developed using Eley–Rideal-type kinetics for the acetic acid consumption and first-order kinetics for the photolysis of hydrogen peroxide. The apparent kinetic constants were estimated, and the accuracy of the model was tested under different experimental conditions to evidence the predictive capability of the model. A very good agreement between the mathematical model calculations and the experimental data obtained in the presence of various H2O2 dosages was achieved. The results demonstrate that the continuous addition of H2O2 during the photo-Fenton reaction ensures the fruitful utilisation of the produced hydroxyl radicals in the acetic acid oxidation reaction to minimise the oxidant consumption and maximise the TOC removal in a shorter irradiation time.

Sugarcane bagasse ozonolysis pretreatment: Effect on enzymatic digestibility and inhibitory compound formation

Sugarcane bagasse was pretreated with ozone to increase lignocellulosic material digestibility. Bagasse was ozonated in a fixed bed reactor at room temperature, and the effect of the two major parameters, ozone concentration and sample moisture, was studied. Acid insoluble and total lignin decreased whereas acid soluble lignin increased in all experiments. Pretreatment barely attacked carbohydrates, with cellulose and xylan recovery rates being >92%. Ozonolysis increased fermentable carbohydrate release considerably during enzymatic hydrolysis. Glucose and xylose yields increased from 6.64% and 2.05%, for raw bagasse, to 41.79% and 52.44% under the best experimental conditions. Only xylitol, lactic, formic and acetic acid degradation compounds were found, with neither furfural nor HMF (5-hydroxymethylfurfural) being detected. Washing detoxification provided inhibitor removal percentages above 85%, increasing glucose hydrolysis, but decreasing xylose yield by xylan solubilization. SEM analysis showed structural changes after ozonization and washing.

Photocatalytic Oxidation of Acetic Acid overCdS

The photocatalytic degradation of acetic acid over cadmium sulphidesemiconductor was investigated. The effect of various parameters, such as pH,concentration of acetic acid,amount of catalyst, effect of light intensity were observed. A tentative mechanism has been proposed for the phtocatalyticdegradation of acetic acid using CdS semiconductor as catalyst.

Plasmonic Titania Photocatalysts Active under UV and Visible-Light Irradiation: Influence of Gold Amount, Size, and Shape

Plasmonic titania photocatalysts were prepared by titania modification with gold by photodeposition. It was found that for smaller amount of deposited gold (≤0.1 wt%), anatase presence and large surface area were beneficial for efficient hydrogen evolution during methanol dehydrogenation. After testing twelve amounts of deposited gold on large rutile titania, the existence of three optima for 0.5, 2 and >6 wt% of gold was found during acetic acid degradation. Under visible light irradiation, in the case of small gold NPs deposited on fine anatase titania, the dependence of photoactivity on gold amount was parabolic, and large gold amount (2 wt%), observable as an intensively coloured powder, caused photoactivity decrease. While for large gold NPs deposited on large rutile titania, the dependence represented cascade increase, due to change of size and shape of deposited gold with its amount increase. It has been thought that spherical/hemispherical shape of gold NPs, in comparison with rod-like ones, is beneficial for higher level of photoactivity under visible light irradiation. For all tested systems and regardless of deposited amount of gold, each rutile Au/TiO2 photocatalyst of large gold and titania NPs exhibited much higher photoactivity than anatase Au/TiO2 of small gold and titania NPs.

Plasmonic Titania Photocatalysts Active under UV and Visible-Light Irradiation: Influence of Gold Amount, Size, and Shape

Plasmonic titania photocatalysts were prepared by titania modification with gold by photodeposition. It was found that for smaller amount of deposited gold (≤0.1 wt%), anatase presence and large surface area were beneficial for efficient hydrogen evolution during methanol dehydrogenation. After testing twelve amounts of deposited gold on large rutile titania, the existence of three optima for 0.5, 2 and >6 wt% of gold was found during acetic acid degradation. Under visible light irradiation, in the case of small gold NPs deposited on fine anatase titania, the dependence of photoactivity on gold amount was parabolic, and large gold amount (2 wt%), observable as an intensively coloured powder, caused photoactivity decrease. While for large gold NPs deposited on large rutile titania, the dependence represented cascade increase, due to change of size and shape of deposited gold with its amount increase. It has been thought that spherical/hemispherical shape of gold NPs, in comparison with rod-like ones, is beneficial for higher level of photoactivity under visible light irradiation. For all tested systems and regardless of deposited amount of gold, each rutile Au/TiO2photocatalyst of large gold and titania NPs exhibited much higher photoactivity than anatase Au/TiO2of small gold and titania NPs.

Sorption, desorption, and degradation of (4-chloro-2-methylphenoxy)acetic acid in representative soils of the Danubian Lowland, Slovakia

Herbicide leaching through soil into groundwater greatly depends upon sorption–desorption and degradation phenomena. Batch adsorption, desorption and degradation experiments were performed with acidic herbicide MCPA and three soil types collected from their respective soil horizons. MCPA was found to be weakly sorbed by the soils with Freundlich coefficient values ranging from 0.37 to 1.03mg1−1/nkg−1L1/n. It was shown that MCPA sorption positively correlated with soil organic carbon content, humic and fulvic acid carbon contents, and negatively with soil pH. The importance of soil organic matter in MCPA sorption by soils was also confirmed by performing sorption experiments after soil organic matter removal. MCPA sorption in these treated soils decreased by 37–100% compared to the original soils. A relatively large part of the sorbed MCPA was released from soils into aqueous solution after four successive desorption steps, although some hysteresis occurred during desorption of MCPA from all soils. Both sorption and desorption were depth-dependent, the A soil horizons exhibited higher retention capacity of the herbicide than B or C soil horizons. Generally, MCPA sorption decreased in the presence of phosphate and low molecular weight organic acids. Degradation of MCPA was faster in the A soil horizons than the corresponding B or C soil horizons with half-life values ranging from 4.9 to 9.6d in topsoils and from 11.6 to 23.4d in subsoils.

A kinetic model of Ti(IV)-catalyzed H 2O 2/O 3 process in aqueous solution

To well describe the Ti(IV)-catalyzed H 2O 2/O 3 reaction in aqueous solution, a kinetic model was established based on its mechanism. This model was then validated by the experiments of acetic acid degradation in aqueous solution. It was found that the correlation coefficient of fittings was higher than 0.970. Three key operating factors affecting organic degradation in the Ti(IV)-catalyzed H 2O 2/O 3 process were studied, including Ti(IV) concentration, dissolved ozone concentration and initial H 2O 2 concentration. Furthermore, some experiments were conducted to determine the rate constant for dissolved ozone decomposition initiated by Ti 2O 5 2+. The rate constant measured is almost in accord with the data analyzed by this kinetic model. The goodness of fittings demonstrated that this model could well describe the kinetics of the Ti(IV)-catalyzed H 2O 2/O 3 reaction mathematically and chemically. Therefore, this kinetic model can provide some useful information to optimize the parameters in ozonation of water containing certain pollutants.