M-cresol Concentration Research Articles

Microwave-assisted synthesis of Ag-Cu co-modified TiO2 catalyst for efficient photocatalytic oxidation of M-cresol

In this study, the photocatalytic oxidation of toxic industrial compound m-cresol by Ag-Cu/-TiO2 P25 catalyst under UV light irradiation has been studied. Photocatalysts of P25 titanium dioxide modified with copper and silver are prepared by a new cost-effective microwave-assisted method. By varying the molar ratio Cu:Ag (1:1, 1:2, 2:1), X-ray diffraction analysis manifested a change in anatase/rutile amounts ratio and the appearance new phases Ag2O and Cu3Ti besides metallic Ag. The photocatalytic activity has been examined as a function of catalyst dose, the initial concentration of m-cresol, and the addition of airflow. The highest photocatalytic degradation performance is achieved for 2 g/L of 1:1 Ag/Cu-TiO2 P25 catalyst and 50 mg/L m-cresol in air, much better than TiO2 P25 catalyst, with good stability and reused after recovery. The improved catalyst gives any industries that use m-cresol as an element in fabricating other products the possibility of controlling the rejected concentrations of MC in wastewater and minimizing its harmful impact on the environment.

Novel use of activated carbon fabric to mitigate smoke taint in grapes and wine

Background and Aims Grapegrowers and winemakers, around the world, are searching for strategies to mitigate the compositional and sensory consequences of grapevine exposure to smoke from wildfires. This study evaluated the use of activated carbon fabrics as protective coverings to mitigate the uptake of smoke-derived volatile phenols by grapes, and accordingly, the intensity of smoky, ashy characters in wine. Methods and Results Smoke was applied to Mataro grapes, with and without individual bunches being enclosed in bags made from three activated carbon fabrics (felt, light cloth and heavy cloth). Wine made from smoke-exposed grapes had an elevated concentration of volatile phenols, but the composition of wines made from grapes protected by activated carbon fabric was comparable to that of the Control wine; the difference in concentration of guaiacol, o- and m-cresol and/or syringol was only 1 μg/L. Wine made from smoke-exposed grapes had diminished fruit and prominent smoke characters, whereas the sensory profile of the wines corresponding to activated carbon fabric treatments could not be differentiated from that of the Control wine. Analysis by GC/MS of the activated carbon fabrics following repeated smoke exposure confirmed their adsorption of smoke volatiles. Conclusions The activated carbon fabrics successfully protected Mataro grapes and wine from being tainted by smoke exposure. Significance of the Study This study demonstrates a promising new technology for overcoming smoke taint, an issue of major concern for grape and wine producers worldwide.

Biodegradation of phenolic compounds in waste foundry sand: Physical and chemical characterization of foundry sand and bacterial degradation kinetics

The foundry sand agglomerated with the phenolic resin becomes a hazardous waste after its use in the metallurgical industry. Thus, the present work aimed to study the biodegradation of phenolic compounds present in the waste phenolic foundry sand, such as phenol, o-cresol and m-cresol which were used as the only carbon source to Burkholderia genus. The foundry sand showed an initial concentration of phenol, m-cresol and o-cresol as 953, 360 and 110 mg L−1, respectively. After the bioprocess, a degradation efficiency of 97% for phenol and 100% for m-cresol and o-cresol, at temperature 28 °C and agitation 180 rpm and also no bacterial toxicity were observed. Thus, the bioremediation of waste foundry sand with reducing environmental and economic impacts through an ecologically correct and also low-cost process becomes potential to be applied on an industrial scale.

Three-dimensional hierarchically porous PbO2 electrode for electrochemical degradation of m-cresol

The modification of PbO2 electrode with high catalytic activity and stability for electrochemical degradation of pollutants remains a great challenge. Accordingly, a novel three-dimensional hierarchically porous PbO2 electrode with polypyrrole (PPy) as middle layer (marked as Ti/SnO2–Sb/PPy/PbO2) was developed for the first time. The physicochemical characterization results showed more intact and ordered “pyramid” structures were formed when the PPy was introduced to be the middle layer of PbO2 electrode. Additionally, the crystallinity of PbO2 and the proportion of adsorbed hydroxyl oxygen were all increased significantly. The electrochemical characterization results showed the active surface area and oxygen evolution overpotential of PbO2 electrode were also improved with PPy middle layer as middle layer. Besides, the electrode film resistance was reduced greatly. Also the PbO2 electrode with PPy middle layer possessed higher degradation ability of m-cresol and lower energy consumption. Above results indicated the physicochemical and electrochemical characterization of PbO2 electrode were all enhanced significantly with the introduction of PPy middle layer. Also the phenomenon that current-controlled reaction would transformed into diffusion-controlled reaction in the process of electrochemical degradation was observed. The effects of experimental parameters on electrochemical degradation were evaluated, indicating lower initial m-cresol concentration, higher current density, temperature and pH were beneficial for electrochemical degradation of m-cresol. Additionally, a possible degradation pathway of m-cresol was proposed. Finally, the continuous experiments of m-cresol degradation indicated the Ti/SnO2–Sb/PPy/PbO2 electrode possessed stable degradation ability and high safety within 30 days.

Electrochemically assisted photocatalytic removal of m-cresol using TiO2 thin film-modified carbon sheet photoelectrode

In this study, removal of m-cresol has been performed using photoeletrocatalysis technique at the surface of titanium dioxide (TiO2) thin film-modified carbon sheet photoelectrode. A biased potential was applied across this photoelectrode illuminated by UV light to investigate the feasibility of an electrochemically assisted photocatalytic process in this degradation. For preparation of this photoelectrode, the photocatalytically active TiO2 thin film was covered on the carbon sheet by dip coating technique using economically accessible TiO2 powder (Degussa P25). It was found that the m-cresol could be degraded more efficiently by this photoelectrocatalytic process than the degradation obtained by photocatalytic oxidation or by electrochemical oxidation or alone. The effect of various parameters, such as m-cresol concentration, pH and applied potential on the photoelectrocatalytic degradation of m-cresol was studied and discussed.

The optimization, kinetics and mechanism of m-cresol degradation via catalytic wet peroxide oxidation with sludge-derived carbon catalyst

The sludge-derived carbon catalyst modified with 0°C HNO3 solution was tested in catalytic wet peroxide oxidation of m-cresol (100mgL−1) with systematical mathematical models and theoretical calculation for the first time. The reaction conditions were optimized by response surface methodology (RSM) as T=60°C, initial pH=3.0, C0,H2O2(30%)=1.20gL−1 (lower than the stoichiometric amount of 1.80gL−1) and Ccat=0.80gL−1, with 96% of m-cresol and 47% of TOC converted after 16min and 120min of reaction, respectively, and ξ (mg TOC/g H2O2 fed)=83.6mg/g. The end time of the first kinetic period in m-cresol model was disclosed to be correlated with the fixed residue m-cresol concentration of about 33%. Furthermore, the kinetic constants in models of TOC and H2O2 exactly provide convincing proof of three-dimensional response surfaces analysis by RSM, which showed the influence of the interaction between organics and H2O2 on effective H2O2 utilization. The reaction intermediates over time were identified by gas chromatography–mass spectrometer based on kinetics analysis. Four degradation pathways for m-cresol were proposed, of which the possibility and feasibility were well proven by frontier molecule orbital theory and atomic charge distribution via density functional theory method.

Antioxidant responses and lipid peroxidation in Mozambique tilapia (Oreochromis mossambicus) exposed to phenol and m-cresol

The present study evaluated phenol and m-cresol induced oxidative stress responses in the teleost fish Oreochromis mossambicus in a semi-static test system in which water was renewed every 24 h. Fishes were exposed to sublethal (1/10 of LC50/96 h) concentration of phenol (3.12 mg l-1) and m-cresol (2.2 mg l-1) for a period of 21 days. Significant increases in catalase (CAT) and superoxide dismutase (SOD) activities in gills, liver and kidney of treated groups represent an adaptive response to free radical toxicity. Reduction in enzyme activity shows that all reactive oxygen species (ROS) are not being quenched. Glutathione-S-transferase (GST) activity was found to be highly elevated in liver which may be due to its important role in the detoxification of xenobiotics. Total reduced glutathione glutathiore peroxidase (GSH) level was found to be highest in liver which may be an adaptive mechanism to oxidative stress. An increased hydroperoxide (HP) level was observed in liver, kidney and muscle of both the treated groups which may be attributed to the decreased glutathione peroxidase (GPx) activity observed. Increased malondialdehyde (MDA) levels in gills and liver indicates that elevated antioxidant enzyme activities were not efficient enough to prevent lipid peroxidation in these tissues. Taken as a whole, the present results seem to implicate that phenolic compounds are potent mediators of free radical generation in fish.

Artificial neural network modelling of photodegradation in suspension of manganese doped zinc oxide nanoparticles under visible-light irradiation.

The artificial neural network (ANN) modeling of m-cresol photodegradation was carried out for determination of the optimum and importance values of the effective variables to achieve the maximum efficiency. The photodegradation was carried out in the suspension of synthesized manganese doped ZnO nanoparticles under visible-light irradiation. The input considered effective variables of the photodegradation were irradiation time, pH, photocatalyst amount, and concentration of m-cresol while the efficiency was the only response as output. The performed experiments were designed into three data sets such as training, testing, and validation that were randomly splitted by the software's option. To obtain the optimum topologies, ANN was trained by quick propagation (QP), Incremental Back Propagation (IBP), Batch Back Propagation (BBP), and Levenberg-Marquardt (LM) algorithms for testing data set. The topologies were determined by the indicator of minimized root mean squared error (RMSE) for each algorithm. According to the indicator, the QP-4-8-1, IBP-4-15-1, BBP-4-6-1, and LM-4-10-1 were selected as the optimized topologies. Among the topologies, QP-4-8-1 has presented the minimum RMSE and absolute average deviation as well as maximum R-squared. Therefore, QP-4-8-1 was selected as final model for validation test and navigation of the process. The model was used for determination of the optimum values of the effective variables by a few three-dimensional plots. The optimum points of the variables were confirmed by further validated experiments. Moreover, the model predicted the relative importance of the variables which showed none of them was neglectable in this work.

Meta-Cresol Affects Lipid Raft Organization in Membrane-Model Systems and Increases Membrane Leakage in Neural Cells

m-cresol is an excipient stabilizer used in numerous pharmaceutical formulations, including injectable insulin and vaccines. Therefore, we studied the effects of m-cresol in a range of concentrations from 10nM to 3mM on membrane model systems mimicking lipid-rafts and living neural-cells. First, the intrinsic fluorescence of m-cresol was studied. Both its fluorescence lifetime and anisotropy increased in the presence of liposomes, indicating a decreased mobility of the molecule. This interaction was dependent on membrane lipid composition. To elucidate this process, liposomes were labeled with several membrane probes spanning a range of in-depth locations and with preference for distinct lipid domains. For the probes located in the bilayer core (DPH and trans-parinaric acid), no effect was detected even for an m-cresol concentration of 300M, whereas for the more superficial NBD-DOPE and NBD-DPPE, >30M m-cresol induced a significant fluorescence lifetime decrease. Atomic force microscopy experiments were performed on ternary supported lipid bilayers containing raft-like liquid ordered domains (Lo). Indeed, it was observed that upon addition of m-cresol in the M range, a reduction of the Lo occurs without changing their thickness. For higher m-cresol concentrations, raft-like domains are not detected at all. Whole-cell voltage-clamp recordings from pyramidal-neurons isolated from the CA1 region of rat hippocampus (p21-p29) and from N1E-115 neuroblastoma cells were also performed. m-Cresol was applied during constant superfusion and the following parameters were monitored: series-resistance, whole-cell capacitance, holding-current (Vm=-70 mV), and another read-out for the leak-current. Results show that only the leak current was altered by m-cresol (>100 M). As a whole, we show that m-cresol interacts with the membrane, affecting lipid raft organization, with functional implications on neural-cell integrity. We thank F.C.T. Portugal for financial support (Ciência2007, SFRH/BD/64442/2009, PEst-OE/QUI/UI0612/2011).

Degradation of m-cresol in aqueous solution by dielectric barrier discharge

It was carried out a theoretical and experimental study of the m-cresol degradation in aqueous solution using a non-thermal plasma induced by dielectric barrier discharge. For the experimental setup a coaxial reactor vertically placed was used. Wherein a liquid solution flowing inside the internal electrode was impelled by a peristaltic pump and falling over the external surface of the internal electrode. Working gas was applied in a parallel direction respect to the surface of the liquid and inside of the quartz tube. Non-thermal plasma was generated at the gas-liquid interface in Ar-O2 gas mixtures with a high-voltage power supply system. The electric power applied ranged from 10–60W at a 3.0 kHz frequency. The initial concentration of m-cresol was of 5 × 10−3 mol/L, and the removal efficiency up to 97.3% was obtained after 1 h of treatment. For the theoretical study a simplified model of the chemical kinetics was developed where the temporary evolution of the compounds generated in the process of degradation of the m-cresol was analyzed. Byproducts as oxalic acid and CO2 were found.

Kinetic modelling for removal of m-cresol from wastewater using mixed microbial culture in batch reactor

An indigenous mixed microbial culture isolated from an effluent treatment section of a coke oven plant has been studied for its m-cresol biodegradation capacity under aerobic batch reactor operation. The culture, after acclimatization could biodegrade up to 700 mg/L of m-cresol. The m-cresol concentration in the present study was at 50 mg/L and then ranged from 100 to 700 mg/L with step up concentration of 100 mg/L. Both biodegradation kinetics and microorganism growth kinetics were studied and kinetic parameters were estimated. The result showed that m-cresol was an inhibitory-type substrate and the inhibition effect became predominant after 200 mg/L of initial m-cresol. The specific growth rate of microorganisms increased up to 200 mg/L of m-cresol as sole carbon source, and then started decreasing. The kinetic data obtained in this study have been fitted to different substrate inhibition models (Haldane, Han-Levenspiel, Edward, Luong, Aiba, Teissier, Yano-Koga). Among all models, Han-Levenspiel and Luong were best fitted for this study (root mean square error = 0.001349). In addition, the variation of observed yield coefficient Yx/s with initial m-cresol concentration was investigated. The values of kinetic constants estimated by the models proved that the mixed culture used in the study had good potential for m-cresol degradation.

Kinetic Study of the Electrochemical Mineralization of m-Cresol on a Boron-Doped Diamond Anode

The kinetics of the electrooxidation of m-cresol in aqueous solution was investigated in a one-compartment flow electrochemical cell with a boron-doped diamond electrode (BDD). Cyclic voltammograms recorded on BDD revealed that cresol oxidation takes place at a potential very close to the discharge of water. Under potentiostatic conditions, at a working potential lower than water discharge, a passive layer was rapidly formed on the electrode surface due to cresol polymerization. The anode fouling was not observed during electrolysis performed with the flow electrochemical cell operating under galvanostatic conditions. In this case, the decay of mcresol concentration followed a pseudo-first-order kinetics. The abatement of chemical oxygen demand (COD) showed that the kinetics of m-cresol oxidation was limited by mass transfer and that a full mineralization was achieved. A good agreement between predicted and experimental COD and instantaneous current efficiency values was obtained, although some deviations were observed at high current since the experimental data decreased faster than those predicted ones. These deviations can be explained by the occurrence of oxygen evolution which increases the mass transfer coefficient. Keywords: Electrooxidation, Boron-doped diamond, Cresol, Wastewater treatment, mineralization, polymerization, voltammograms, Aromatic compounds, kinetics, oxalic

Biodegradation of m-cresol by aerobic granules in a sequencing batch reactor

The present study was aimed at the development of aerobic granules in a sequencing batch reactor for the biodegradation of m-cresol. The reactor was started with 100 mg L−1 of m-cresol. 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 1.5–5 mm. The integrity coefficient and density of the granules was found to be 98% and 1046 kg m−3, respectively. The settling velocity of the granules was found to be in the range of 2–6×10−2 m s−1. The aerobic granules were able to degrade m-cresol up to 800 mg L−1 at a removal efficiency of 87%. UV and GC/MS studies confirmed that the biodegradation of m-cresol occurred via catechol via the ortho-cleavage pathway. The specific m-cresol degradation rate in aerobic granules followed the Haldane model for substrate inhibition. A high specific m-cresol degradation rate of up to 0.718 g m-cresol g−1VSS−1d−1 was sustained up to an m-cresol concentration of 400 mg L−1. The higher removal efficiency and good settling characteristics of aerobic granules make the sequencing batch reactor method suitable for enhancing the microorganism potential for biodegradation of inhibitory compounds.

Photodegradation of m-cresol by Zinc Oxide under Visible-light Irradiation

The photodegradation of m-cresol was carried out under visible light (46% sunlight) by ZnO as photocatalyst. To measure the efficiency of photodegradation, the different variables studied included amount of photocatalyst, concentration of m-cresol and pH. The maximum amount of photocatalyst and concentration of m-cresol was 1.5 g/L and 25 ppm respectively. The photodegradation was favorable in the pH 6-9 range. The detected intermediates were 2-methyl-1,4-benzodiol, 2-methyl-para-benzoquinone, 3,5-dihydroxytoluene and 2,5-dihydroxy-benzaldehyde. TOC studies show that 78% of total organic carbon is removed from solution during irradiation time. This study indicates the great potential of ZnO to remove aqueous m-cresol under visible-light irradiation which is part of sunlight.

Biodegradation characterisation and kinetics of m-cresol by <i>Lysinibacillus cresolivorans</i>

A novel strain of m-cresol-degrading bacterium, named as Lysinibacillus cresolivorans , was isolated from aerobic sludge from a coking wastewater treatment plant. This bacterium is able to utilise m-cresol as its sole source of carbon and energy. The optimal pH for growth is 6.8 ~ 7.3 and the optimal temperature is 35°C. Compared to organic nitrogen sources, inorganic nitrogen sources were easily utilised for the m-cresol biodegradation. The degradation rate of m-cresol at different starting concentrations was analysed with zero-order kinetic characteristics. When the initial concentration of m-cresol was 224.2 mg·l-1, the reaction rate reached a maximum at 46.80 mg·(l·h)-1.The cell growth kinetics was also investigated with initial m-cresol concentrations varying from 0 to 1 200 mg·l-1. The growth kinetics was well described by the Haldane kinetic models. The parameter values of m-cresol on cell growth were μmax = 0.89 h-1, Ks = 426.25 mg·l-1, Ki = 51.26 mg·l-1. Experiments supplementing growth with glucose indicated that this substrate increased the biomass, and also induced the biodegradation of m-cresol. From the results, it can be concluded that Lysinibacillus cresolivorans is an efficient m-cresoldegrading bacterium and that glucose plays multiple roles in the co-substrate condition. Keywords: m-cresol; biodegradation; Lysinibacillus cresolivorans; high efficient degrading bacterium

What is the optimum concentration of m-cresol in antivenoms?

Antivenoms against snake and scorpion envenomations are usually equine in nature and composed mostly of F(ab')2; additionally, phenol and m-cresol are mainly employed for their preservation. Although there is no study on this subject, m-cresol is utilized by most manufacturers in a concentration that ranges from 0.15 to 0.35 g%. Decreasing the concentration of m-cresol to its minimal effective level may protect victims from its toxic effects and keep the antivenom stable during its shelf life without forming any aggregates. In the present work, different concentrations of m-cresol, ranging from 0.1 to 0.35 g%, were used with some selected batches of snake and scorpion antivenoms. A low concentration of 0.15 g% showed an acceptable preserving result that complies perfectly with antimicrobial specifications stated by the British Pharmacopoeia. Tested antivenoms (in 12 batches), when kept in a cold room for 39 months (more than their shelf life), retained their physical, chemical and microbiological activities according to the specifications of pharmacopeias. The present data demonstrated that reduction of m-cresol concentration to 0.15 g% in case of equine F(ab')2 antivenoms will improve safety of such preparations and preserve their stability during their shelf life.

Isolation and Characterization of Citrobacter farmeri SCO1: A Novel m-Cresol-Degrading Strain

A bacterium capable of biodegrading m-cresol was isolated from aerobic sludge of a coking wastewater treatment plant. Morphological and biochemical analyses, as well as 16S rRNA gene sequence comparisons, demonstrated that the selected strain, SCO1, belongs to the species Citrobacter farmeri. Growth of the bacterium is coupled with the biodegradation of m-cresol. Optimal biodegradation conditions were pH 7 and a temperature of 35°C. Under these conditions, C. farmeri SCO1 degraded approximately 700 mg · L−1m-cresol completely with 200 mg · L−1 biomass in 114 h. Lag periods varied from 0.5 h to 70 h when C. farmeri SCO1 biodegraded m-cresol at concentration ranges between 19 and 697 mg · L−1. The average biodegradation rate (ABR) increased with an increasing initial concentration of m-cresol from 20 to 300 mg · L−1, to a maximum ABR of 9.80 mg · L−1 · h−1. The kinetics followed a zero-order model when lag phase is excluded. Results indicated that C. farmeri SCO1 was an efficient strain and its maximum m-cresol concentration tolerance was higher than for previously described bacteria. A Haldane model was used to interpret the free cell specific growth rate on m-cresol biodegradation. Kinetic parameters were estimated up to an initial concentration of 696 mg · L−1 yielding model constants for maximum specific growth rate (μmax = 0.429 h−1), half saturation (Ks = 37.65 mg · L−1), and substrate inhibition constant (Ki = 165.68 mg · L−1) for cell growth on m-cresol. Results demonstrated that the Haldane model was acceptable for describing the dynamic behavior of m-cresol biodegradation by C. farmeri strain SCO1.

Batch growth kinetics of an indigenous mixed microbial culture utilizing m-cresol as the sole carbon source

An indigenous mixed microbial culture, isolated from a sewage treatment plant located in Guwahati was used to study biodegradation of m-cresol in batch shake flasks. m-Cresol concentration in the growth media was varied from 100 mg/L to 900 mg/L. The degradation kinetics was found to follow a three-half-order model at all initial m-cresol concentrations with regression values greater than 0.97. A maximum observed specific degradation rate of 0.585 h −1 was observed at 200 mg/L m-cresol concentration in the medium. In the range of m-cresol concentrations used in the study, specific growth rate of the culture and specific degradation rates were observed to follow substrate inhibition kinetics. These two rates were fitted to kinetic models of Edward, Haldane, Luong, Han-Levenspiel, and Yano-Koga that are used to explain substrate inhibition on growth of microbial culture. Out of these models Luong and Han-Levenspiel models fitted the experimental data best with lowest root mean square error values. Biokinetic constants estimated from these two models showed good potential of the indigenous mixed culture in degrading m-cresol in wastewaters.

Controlled release of preservatives using dealuminated zeolite Y

This study demonstrates that dealuminated zeolite Y can act as a depot after adsorption of phenol derived preservatives. Upon suspension of zeolite loaded with the preservative m-cresol, equilibrium was quickly reached between free and adsorbed m-cresol. The equilibrium concentration of m-cresol was below 1 mM; however, it was enough to kill bacteria such as Escherichia coli and Staphylococcus aureus under metabolically active conditions. Killing of bacteria was not obtained under non-proliferating conditions and m-cresol was only released from the zeolite upon bacterial activity. Together, these results demonstrate an interesting potential use of dealuminated zeolite Y containing adsorbed preservatives for preventing microbial growth in numerous applications in industry and clinical setting.

Equilibrium, kinetic and thermodynamic studies on the adsorption of m-cresol onto micro- and mesoporous carbon

Investigations were conducted in batch mode to study the adsorption behaviour of m-cresol on a porous carbon prepared from rice husk (RHAC) by varying the parameters such as agitation time, m-cresol concentration (50–300 mg/l), pH (2.5–10) and temperature (293–323 K). Studies showed that the adsorption decreased with increase in pH and temperature. The isotherm data were fitted to Langmuir, Freundlich, and Dubinin–Radushkevic (D–R) models. The kinetic models such as pseudo-first-order, pseudo-second-order and intraparticle diffusion models were selected to understand the reaction pathways and mechanism of adsorption process. The thermodynamic equilibrium coefficients obtained at different temperatures were used to evaluate the thermodynamic constants Δ G°, Δ H° and Δ S°. The sorption process was found to be exothermic in nature (Δ H°: −23.46 to −25.40 kJ/mol) with a decrease in entropy (Δ S°: −19.44 to −35.87 J/(mol K)). The negative value of Gibbs free energy, Δ G° indicates that the adsorption occurs via a spontaneous process. The decrease in the value of −Δ G° from 17.70 to 13.54 kJ/mol with increase in pH and temperature indicates that the adsorption of m-cresol onto activated carbon is less favourable at higher temperature and pH range. The influence of mesopore and a possible mechanism of adsorption is also suggested.