Kinetics Of Phenol Degradation Research Articles

New insight into the mechanism of ferric hydroxide-based heterogeneous Fenton-like reaction.

The heterogeneous Fenton-like reaction (HeFR) has always been a research focus for environmental applications. However, it has long been difficult to reach a consensus on the reaction mechanism because the process of metal ions dissolution and its role were not well understood. In this paper, we propose the courses of organics-mediated coordination or/and reduction dissolution of ferric hydroxide to initiate the autocatalytic kinetics of phenol degradation and illustrate it through density functional theory (DFT) and experiments. With the increase of hydrogen peroxide concentration, the degradation of phenol changes from autocatalytic kinetics to first-order kinetics. Furthermore, a novel "limit segmentation method" initiated by us indicates that homogeneous reaction plays a decisive role in the phenol degradation process. The dominant roles of the reactive organics in both iron dissolution and the iron cycle and of the homogeneous reaction in the whole degradation process in the ferric hydroxide-based HeFR system are brand-new insights that pave the pathway for future research.

Modified high-efficiency carbon material for deep degradation of phenol by activating persulfate

A series of cobalt-nitrogen modified catalysts were prepared and applied to the degradation of phenol. The Mott Schottky catalyst (CoO/NGr@C) with high pyridine nitrogen content was designed to activate potassium peroxodisulfate (PDS) to generate active free radicals for phenol degradation. The structural properties of the materials are analyzed by XPS, TEM and then the charge density calculation is performed by DFT, which proves the existence of the highly active interface effect. Co–N-CMCM-41 can only degrade phenol into benzoquinone and it is difficult to achieve further degradation of benzoquinone, while the modified CoO/NGr@C can achieve deep mineralization of the intermediate benzoquinone through UV spectrum. EPR was used to prove that both hydroxyl radicals and sulfate radicals exist in the degradation process of phenol. Through the DFT simulation calculation of the material, it is proved that the existence of carbon activated by nitrogen and the electron rearrangement between cobalt and nitrogen-rich carbon lead to the catalytic activity of the material. The degradation conditions of phenol were optimized and the reaction kinetics of further phenol degradation were studied. The activation energy of phenol degradation on CoO/NGr@C is calculated to be 34.38 kJ mol−1.

Evaluation of degradation kinetic and photostability of immobilized TiO2/activated carbon bilayer photocatalyst for phenol removal

Fabrication of immobilizable titanium (IV) oxide (TiO2) and activated carbon (AC) were done using epoxidized natural rubber-polyvinyl chloride as adhesive. The two materials were combined in an immobilized layer by layer manner to remove phenol from aqueous media. This immobilized bilayer TiO2/AC photocatalyst operated via simultaneous synergy processes of phenol adsorption into AC layer and photocatalytic degradation by TiO2 top layer. The pseudo second order rate equation as derived from Langmuir Hinshelwood model was used to determine the optimal conditions for phenol degradation. It was found that the optimized loading of immobilized AC and TiO2 were 2.54 and 0.32 mg cm−2, respectively. The kinetics of phenol degradation was investigated over operational parameters namely pH of the solution (pH 2-10), initial concentration (10-100 mg L−1), light intensity (0.03-22 Wm−2) and dissolved O2 supply (0-500 mL min−1) and they were optimized at pH 6.5, 10 mg L−1, 6.0 Wm−2 of UV leakage and 100 mL min−1 of aeration rate, respectively. The optimized TiO2/AC bilayer photocatalyst could remove 94% of phenol while single TiO2 only removed 47% from the solution after 90 min in the presence of UV-vis light. The reusability and stability of TiO2/AC photocatalyst exhibited positive outcome as observed after 10 cycles of application showing the favorability of the bilayer photocatalyst for various applications.

Degradation kinetics of anthocyanin, flavonoid, and total phenol in bignay (Antidesma bunius) fruit juice during ohmic heating

The effect of ohmic heating on bioactive compounds in bignay (Antidesma bunius) fruit juice during ohmic heating were evaluated. The parameters measured were total phenol, anthocyanin, flavonoid, and antioxidant activity. Ohmic heating was conducted at 70, 90, and 110 °C, and samples were collected at heating times of 0, 15, 30, and 45 minutes. Electrical conductivity of bignay fruit juice increased linearly with temperature with values ranged from 0.012 S/m at 32 °C to 0.039 S/m at 110 °C. Insignificant change in total phenol was observed, while anthocyanin and flavonoid showed significant degradation and the degradation kinetics followed the first-order kinetic model. The degradation rate constants for anthocyanin ranged from 0.0016 to 0.0213 min-1 with activation energy (Ea) of 63.880 kJ/mol and the degradation rate constants for flavonoid were in the range of 0.0107 to 0.0209 min-1 with activation energy of 18.210 kJ/mol. Antioxidant activities (IC50) obtained from DPPH method ranged from 0.106-0.168 mg/mL while those obtained from ABTS method ranged from 0.131-0.161 mg/mL. The results indicate that anthocyanin and total phenol in bignay fruit juice is much more stable during heating compared to flavonoid.

Effect of Culture Condition and Growth Kinetics on Phenol Biodegradation by an Indigenous Rhodococcus pyridinivorans Strain PDB9T NS-1

The US Environmental Protection Agency listed phenolic compounds as priority pollutants, and their occurrence in water systems poses serious health risks to humans and other living species. The culture conditions are extremely crucial for microbial growth, enzymatic and cellular metabolic activities. Thus, the effects of different culture parameters like pH, temperature (°C), and agitation speed (RPM) on the indigenous Rhodococcus pyridinivorans strain PDB9T NS-1 were modeled using response surface methodology (RSM) and central composite design (CCD). The results showed that the main effect of pH and interaction between pH and agitation speed had a significant to a moderately significant effect on phenol degradation by the indigenous R. pyridinivorans strain PDB9T NS-1. Almost complete phenol degradation was obtained at an optimal setting of pH 7.5, 187 rpm, and 34 °C in 18 h. Growth and phenol degradation kinetics of the actinomycetes was examined in a batch shake flask under the optimized conditions. The growth of Rhodococcus species at varying initial levels of the phenol followed a Pamukoglu and Kargi substrate inhibition model with half-saturation constant (Ks ) of 54.21 mg/l, maximum specific growth rate (µ max) of 0.169 (1/h), substrate inhibition constant (Ksi ) of 243.26 mg/l. The results obtained from the optimization of culture conditions and growth kinetics by the indigenous R. Pyridinivorans strain PDB9T NS-1 suggest the potential of the system in the treatment of phenolic wastewater.

Fe-based single-atom catalysis for oxidizing contaminants of emerging concern by activating peroxides

We prepared a single-atom Fe catalyst supported on an oxygen-doped, nitrogen-rich carbon support (SAFe-OCN) for degrading a broad spectrum of contaminants of emerging concern (CECs) by activating peroxides such as peroxymonosulfate (PMS). In the SAFe-OCN/PMS system, most selected CECs were amenable to degradation and high-valent Fe species were present for oxidation. Moreover, SAFe-OCN showed excellent performance for contaminant degradation in complex water matrices and high stability in oxidation. Specifically, SAFe-OCN, with a catalytic center of Fe coordinated with both nitrogen and oxygen (FeNxO4−x), showed 5.13-times increased phenol degradation kinetics upon activating PMS compared to the catalyst where Fe was only coordinated with nitrogen (FeN4). Molecular simulations suggested that FeNxO4−x, compared to FeN4, was an excellent multiple-electron donor and it could potential-readily form high-valent Fe species upon oxidation. In summary, the single-atom Fe catalyst enables efficient, robust, and sustainable water and wastewater treatment, and molecular simulations highlight that the electronic nature of Fe could play a key role in determining the activity of the single-atom catalyst.

Research on dynamics and mechanism of treatment on phenol simulated wastewater by the ultrasound cooperated electro-assisted micro-electrolysis.

In the research, the ultrasound was introduced to the electric-assisted micro-electrolysis system to improve the treatment efficiency of phenol simulated wastewater. The results showed that the phenol removal efficiency was significantly enhanced by the electric-assisted micro-electrolysis method in the presence of ultrasound, which could reach 88.61% under the initial value of pH 4, an iron dosage of 50g/L, a mass ratio of iron/carbon of 1:1, and the initial phenol concentration of 100mg/L. The degradation kinetics of phenol was in accordance with a second-order kinetic model. The synergistic effect of the ultrasonic and electric-assisted micro-electrolysis method was obvious with a synergistic factor at 98.02%. The degradation mechanism of phenol was that the treatment could effectively destroy the benzene ring structure of phenol in the liquid phase with ring-opening reaction and small molecules substances generated. PRACTITIONER POINTS: The article was the pretreatment of coking wastewater. First, the synergistic effects between ultrasound and electrochemical method through the removal ratio of phenol were found. Second, it was showed that the initial pH and applied intensity of voltage had the effects on removal ratio of phenol by the UEME method. Third, the synergy factor (Syn ) between ultrasonic and electrochemical method was 98.02%. Finally, the mechanism of the UEME degradation of phenol was researched. The technology could effectively improve the biodegradability of coking wastewater and provide conditions for subsequent biochemical treatment. So, we thought this article was suitable for the journal.

Greatly enhanced oxidative activity of δ-MnO2 to degrade organic pollutants driven by dominantly exposed {−111} facets

The reactivity of oxidizing materials is highly related to the exposed crystal facets. Herein, δ-MnO2 with different exposure facets were synthesized and the oxidative activities of the as-prepared materials were evaluated by degrading phenol in water without light. The degradation rate of phenol by δ-MnO2-{−111} was significantly higher than that by δ-MnO2-{001}. δ-MnO2-{−111} also displayed high degradation efficiency to a variety of other organic pollutants, such as ciprofloxacin, bisphenol A, 3-chlorophenol and sulfadiazine. Comprehensive characterization and theoretical calculation verified that the {−111} facet had high density of Mn3+, thus displaying enhanced direct oxidative capacity to degrade organic pollutants. In addition, the dominant {−111} facet promoted adsorption/activation of O2, thus favored the generation of superoxide radical (O2•−), which actively participated in the degradation of pollutants. The phenol degradation kinetics could be divided into two distinct phases: the rapid phase (k1obs = 0.468 min−1) induced by Mn3+ and the slower phase (k2obs = 0.048 min−1) dominated by O2•−. The synergistically promoted non-radical and radical based reactions resulted in greatly enhanced the oxidative activity of the δ-MnO2-{−111}. These findings deepen the understanding of facet-dependent oxidative performance of materials and provided valuable insights into the possible practical application of δ-MnO2 for water purification.

Effect of Radio Frequency Low Pressure Cold Plasma on Total Phenol, Antioxidant Activity and Colour Degradation Kinetics of Red Chilli Pepper Powder

The study was aimed to analyse the effect of low pressure cold plasma treatment [operated at 60.8 kPa on the quality parameters of red chilli pepper powder (RCPP)]. The experiments were conducted at two radio frequency power levels (60 W, 120 W) over a time range from 0 to 10 min. Total phenols, antioxidant activity, colour, and moisture content were determined. Results showed that radio frequency operating power and treatment time had significant negative effects (p < 0.05) on the quality parameters analysed. Cold plasma treatment reduced the redness, total phenol content, moisture content, and increased the antioxidant activity of the RCPP. Changes in the quality of the treated samples, especially the colour degradation were significant after 4 min of treatment. Degradation kinetics was determined for parameters studied to ascertain their order of reaction during cold plasma treatment. The order of reaction was decided from best fit models with the highest R2, minimum bias, and error sum of squares. Total phenol followed a zero-order, whereas antioxidant activity and colour followed first-order reactions. The study explored the possibilities and impact of using cold plasma for powdered food materials.

Phenol Degradation Kinetics by Free and Immobilized Pseudomonas putida BCRC 14365 in Batch and Continuous-Flow Bioreactors

Phenol degradation by Pseudomonas putida BCRC 14365 was investigated at 30 °C and a pH of 5.0–9.0 in the batch tests. Experimental results for both free and immobilized cells demonstrated that a maximum phenol degradation rate occurred at an initial pH of 7. The peak value of phenol degradation rates by the free and immobilized cells were 2.84 and 2.64 mg/L-h, respectively. Considering the culture at 20 °C, there was a lag period of approximately 44 h prior to the start of the phenol degradation for both free and immobilized cells. At the temperatures ranging from 25 to 40 °C, the immobilized cells had a higher rate of phenol degradation compared to the free cells. Moreover, the removal efficiencies of phenol degradation at the final stage were 59.3–92% and 87.5–92%, for the free and immobilized cells, respectively. The optimal temperature was 30 °C for free and immobilized cells. In the batch experiments with various initial phenol concentrations of 68.3–563.4 mg/L, the lag phase was practically negligible, and a logarithmic growth phase of a particular duration was observed from the beginning of the culture. The specific growth rate (μ) in the exponential growth phase was 0.085–0.192 h−1 at various initial phenol concentrations between 68.3 and 563.4 mg/L. Comparing experimental data with the Haldane kinetics, the biokinetic parameters, namely, maximum specific growth rate (μmax), the phenol half-saturation constant (Ks) and the phenol inhibition constant (KI), were determined to equal 0.31 h−1, 26.2 mg/L and 255.0 mg/L, respectively. The growth yield and decay coefficient of P. putida cells were 0.592 ± 4.995 × 10−3 mg cell/mg phenol and 5.70 × 10−2 ± 1.122 × 10−3 day−1, respectively. A completely mixed and continuous-flow bioreactor with immobilized cells was set up to conduct the verification of the kinetic model system. The removal efficiency for phenol in the continuous-flow bioreactor was approximately 97.7% at a steady-state condition. The experimental and simulated methodology used in this work can be applied, in the design of an immobilized cell process, by various industries for phenol-containing wastewater treatment.

Kinetics of phenol degradation by selected bacterial strains with different genetic properties

The major environmental problem in the northeastern Estonia is the semi-coke mounds in oilshale industry areas, Alternatives to the chemical methods (sorption, ozonation) for removingxenobiotic compounds from leachate are biological methods, like bioaugmentation, where theproperly selected microorganisms are used. Determination of the kinetic constants (maximumspecific growth rates (µmax), lag times (A.), half saturation constants (Kso for oxygenatingactivity and Ksa for growth) and inhibition constants (Ki)) will give us information about therate of pollutant degradation and is the basis for the selection of the most effective bacteria forbioaugmentation. In phenol degradation the initial and rate-limiting enzyme is phenolhydroxylase, encoded by different genes, The aim of this work was to carry out a kineticstudy of the aerobic degradation of phenol using single strains (Pseudomonas mendocinaPC 1, P. fluorescens PC 18, PC20 and PC24) isolated from river water continuously pollutedwith phenolic compounds, The strains PC 1 and PC 18 contain genes for multicomponentphenol hydroxylase, whereas single-component phenol hydroxylase (pheBA operon)characterizes the strains PC20 and PC24, The phenol-oxygenating activity (Kso) was obtainedfrom substrate-dependent oxygen uptake data (oxygen concentrations were measured with aClark-type oxygen electrode) using Michaelis-Mentens model. Specific growth rates µ andlag times). were calculated from absorbance growth curves on phenol concentrations 0,2-10.6mM and the growth kinetic constants (µmax, Ksa, Ki) were estimated using Haldanes, Edwardsand Aiba-Edwards model. The Kso values for phenol were one order of magnitude lower instrains PC 1 and PC 18 than in strains PC20 and PC24.

Synergism of ozonation and electrochemical filtration during advanced organic oxidation

Here, we investigated the synergistic effect towards phenol degradation and mineralization between ozonation (O3) and electrochemical filtration (ECF) using perforated titanium as cathode and porous carbon nanotube (CNT) networks as anode. A flow rate of 1.6 mL min−1, 10 mM of sodium sulfate electrolyte, 1.0 mM of phenol (model aromatic compound), and an ozone dose of 12 mgO3 L−1 were used. Insight into the synergistic mechanism was achieved via carbon anode morphology characterization and phenol degradation kinetics analysis. Improved kinetic performance was observed for the combined process (O3-ECF) as compared to the sum of the individual processes, not only towards phenol degradation (3.2-fold increase), but also towards phenol mineralization (2.2-fold increase). Scanning electron microscopy revealed a significant decrease of polymer formation and deposition on CNT after the hybrid O3-ECF process as compared to the ECF alone. Voltage-dependent (0–2.5 V) ozone CNT functionalization was investigated at pH 7–11 to assist in elucidation of the synergistic mechanism. X-Ray photoelectron spectroscopy indicated increases up to 26-fold in CNT oxygen content post-ozonation at pH 7 comparing to fresh CNT. Various potential O3-ECF synergistic reaction mechanisms for organic aromatic oxidation and mineralization are discussed.

Looking at the overlooked hole oxidation: Photocatalytic transformation of organic contaminants on graphitic carbon nitride under visible light irradiation

Solar-energy-enabled photocatalysis is a sustainable process to destruct persistent environmental pollutants via the attack of photogenerated reactive species (e.g., holes, reactive oxygen species such as OH, O2−/HO2, H2O2, and 1O2). Graphitic carbon nitride (g-C3N4) has emerged as a promising polymeric photocatalyst, and its highly tunable properties allow the material with an enhanced photocatalytic activity for environmental remediation. In this study, by taking advantage of simulation and experimental tools, we systematically evaluated the production of reactive species of undoped and carbon (C)-doped g-C3N4 samples, and identify the role of these species in contaminant oxidation under simulated visible sunlight irradiation (xenon lamp, λ > 400 nm). Both g-C3N4 samples produced negligible OH or triplet-excited states (3g-C3N4*), but the C-doped g-C3N4 sample generated more 1O2, O2−, and H2O2 compared to the undoped counterpart. Surprisingly, all these oxidative species did not contribute substantially for the degradation kinetics of contaminant phenol and atrazine, at least for the initial oxidation of the parent compounds; and the results otherwise highlighted the important role of the holes for contaminant transformation. The surface-mediated hole oxidation of the contaminants, including the adsorption of the contaminants on the photocatalyst surface (quantified by the binding free energy) and electron transfer kinetics from the contaminants to the excited photocatalysts (quantified by the concerted proton-coupled electron transfer (CPCET) rate) were investigated by molecular dynamics (MD) and density functional theory (DFT) simulations. The simulation results indicated that C-doping could favor the binding of atrazine but not of phenol on g-C3N4. The C-doping also significantly decreased the CPCET rate of phenol on g-C3N4 but could have little to no adverse impact for the CPCET rate of atrazine. These simulation and experimental results could explain the selective oxidation of phenol and atrazine on undoped and C-doped g-C3N4 in our previous study, and the results also highlight the dominant role of the holes for contaminant transformation that was largely overlooked before. This study generates mechanistic insights of photocatalytic oxidation, and will provide guidelines for the rational design of g-C3N4 as an effective visible-light-responsive photocatalyst for many applications, including contaminant degradation, chemical synthesis, and beyond.

Kinetic features of chromium(VI) reduction and phenol degradation in aqueous solution by treatment in atmospheric-pressure air direct-current discharge

The kinetics of the processes of simultaneous reduction of Cr(VI) and degradation of phenol during the treatment of their aqueous solutions with different initial concentrations using an atmosphericpressure air direct-current discharge have been studied. The solution served as the discharge cathode. It has been shown that the discharge treatment leads to a decrease in the concentration of both Cr(VI) and phenol. Phenol additives accelerate the Cr(VI) reduction process and make it irreversible. The phenol degradation and Cr(VI) reduction kinetics are described well (R2 > 0.99) by the pseudo-first-order rate equation in phenol and Cr(VI) concentrations, respectively. The apparent rate constants of the processes have been determined, the energy efficiency of the processes has been evaluated, and possible mechanisms of the proceeding reactions have been discussed.

An efficient eco advanced oxidation process for phenol mineralization using a 2D/3D nanocomposite photocatalyst and visible light irradiations

Nanocomposites (CNTi) with different mass ratios of carbon nitride (C3N4) and TiO2 nanoparticles were prepared hydrothermally. Different characterization techniques were used including X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), transmission electron spectroscopy (TEM) and Brunauer-Emmett-Teller (BET). UV-Vis DRS demonstrated that the CNTi nanocomposites exhibited absorption in the visible light range. A sun light - simulated photoexcitation source was used to study the kinetics of phenol degradation and its intermediates in presence of the as-prepared nanocomposite photocatalysts. These results were compared with studies when TiO2 nanoparticles were used in the presence and absence of H2O2 and/or O3. The photodegradation of phenol was evaluated spectrophotometrically and using the total organic carbon (TOC) measurements. It was observed that the photocatalytic activity of the CNTi nanocomposites was significantly higher than that of TiO2 nanoparticles. Additionally, spectrophotometry and TOC analyses confirmed that degraded phenol was completely mineralized to CO2 and H2O with the use of CNTi nanocomposites, which was not the case for TiO2 where several intermediates were formed. Furthermore, when H2O2 and O3 were simultaneously present, the 0.1% g-C3N4/TiO2 nanocomposite showed the highest phenol degradation rate and the degradation percentage was greater than 91.4% within 30 min.

Qualitative analysis of a mathematical model for kinetic mechanisms of complete mineralization of phenol by Fe_2^+, Fe_3^+ and H_2O_2

In this work we study the phenol degradation kinetics through the formulation and analysis of a nonlinear system of ordinary differential equations. The results suggest that the dynamics of the model is consistent with the phenomenon of phenol mineralization.

Batch growth kinetic studies for elimination of phenol and cyanide using mixed microbial culture

The efficiency of a mixed microbial culture to eliminate phenol and cyanide from aqueous solution was estimated in a batch process. The influence of initial concentration of phenol and cyanide on the microbial growth was calculated for the range of initial concentration between 50 and 1500mg/L of phenol and 5–150mg/L of cyanide. A maximum specific growth rate of 0.0663h−1 was observed at 250mg/L of phenol and 0.143h−1 at 25mg/L of cyanide concentration in the growth medium. The specific growth rate of the culture followed substrate inhibition kinetics. Monod, Haldane, Edward, Yano and Koga, Luong, Han-Levenspiel, and Powell growth kinetic models were used to determine the growth kinetics of mixed culture. Edward, Luong and Han and Levenspiel models were established as best fit to the specific growth rate data for phenol. However, for cyanide Haldane and Edward models were found to be best with lowest Marquardt’s percent standard deviation (MPSD) values. The degradation kinetics of phenol and cyanide was found to follow a three-half order model at all initial concentrations with lowest MPSD value.

Photocatalytic activity of nitrogen doped TiO2 nanotubes prepared by anodic oxidation: The effect of applied voltage, anodization time and amount of nitrogen dopant

Nitrogen doped TiO2 nanotube arrays were prepared by anodizing Ti foils in an organic electrolyte containing specified amounts of urea as nitrogen precursor. The photocatalytic activity of the samples was evaluated by analyzing the degradation kinetics of phenol in water. The influence of tubes’ length, tubes’ surface morphology and amount of nitrogen in the TiO2 lattice on hydroxyl radical formation efficiency, photocatalytic activity and stability in four cycles was investigated. It was found that the photocatalytic activity as well as the charge carrier recombination rate depends on nitrogen concentration and the process parameters. 3.5μm-long nanotubes containing 0.34at.% of nitrogen seems to be favorable in phenol degradation and OH radicals generation under visible light. Comparison of XPS and photocatalytic activity test results shows decrease in phenol degradation efficiency with increasing amount of carbon contaminants on photocatalysts’ surface.

Physiological and functional diversity of phenol degraders isolated from phenol-grown aerobic granules: Phenol degradation kinetics and trichloroethylene co-metabolic activities

Aerobic granule is a novel form of microbial aggregate capable of degrading toxic and recalcitrant substances. Aerobic granules have been formed on phenol as the growth substrate, and used to co-metabolically degrade trichloroethylene (TCE), a synthetic solvent not supporting aerobic microbial growth. Granule formation process, rate limiting factors and the comprehensive toxic effects of phenol and TCE had been systematically studied. To further explore their potential at the level of microbial population and functions, phenol degraders were isolated and purified from mature granules in this study. Phenol and TCE degradation kinetics of 15 strains were determined, together with their TCE transformation capacities and other physiological characteristics. Isolation in the presence of phenol and TCE exerted stress on microbial populations, but the procedure was able to preserve their diversity. Wide variation was found with the isolates’ kinetic behaviors, with the parameters often spanning 3 orders of magnitude. Haldane kinetics described phenol degradation well, and the isolates exhibited actual maximum phenol-dependent oxygen utilization rates of 9–449 mg DO g DW−1 h−1, in phenol concentration range of 4.8–406 mg L−1. Both Michaelis–Menten and Haldane types were observed for TCE transformation, with the actual maximum rate of 1.04–21.1 mg TCE g DW−1 h−1 occurring between TCE concentrations of 0.42–4.90 mg L−1. The TCE transformation capacities and growth yields on phenol ranged from 20–115 mg TCE g DW−1 and 0.46–1.22 g DW g phenol−1, respectively, resulting in TCE transformation yields of 10–70 mg TCE g phenol−1. Contact angles of the isolates were between 34° and 82°, suggesting both hydrophobic and hydrophilic cell surface. The diversity in the isolates is a great advantage, as it enables granules to be versatile and adaptive under different operational conditions.

Simultaneous bioremediation of Cr(VI) and phenol from single and binary solution using Bacillus sp.: Multicomponent kinetic modeling

In the present study, batch experiments for simultaneous biological degradation of phenol and bioaccumulation of Cr(VI) by a bacterial strain Bacillus sp. (MTCC No. 3166) were carried out in incubator cum shaker at 30°C and 120rpm. The Bacillus sp. was acclimatized to the various concentrations of Cr(VI) and phenol both in single and binary substrate solution. This bacterium can reduce the toxic concentration of Cr(VI) up to 25mg/L and phenol was degraded up to 50mg/L. In a binary substrate solution of Cr(VI) and phenol (1:2 ratio), reduction of Cr(VI) was found more than a single substrate solution at all concentrations of Cr(VI). The possible reason behind this fact that Bacillus sp. was utilized phenol as carbon source for the reduction of Cr(VI). Monod and Haldane kinetics models are used to explain the kinetics of Cr(VI) reduction and Phenol degradation. The interaction parameter of Cr(VI) was more than of phenol, which shows that Cr(VI) inhibited the effect of both reduction of Cr(VI) and biodegradation of while phenol improves the Cr(VI) reduction kinetic. Yield coefficient and the decay coefficient after the exponential phase of the bacterium were estimated, for Cr(VI) and phenol both in single and binary substrate solution.