Optimization of solar photocatalytic biodegradability of seawater using statistical modelling

The performance of zinc oxide (ZnO) as a photocatalyst was evaluated for the treatment of pollutants present in seawater. Batch experimental studies were carried out by varying the dosage of photocatalyst (1–4 ​g/L). The effect of reaction time, pH and the dosage of photocatalyst was evaluated with the percentage removal efficiencies of chemical oxygen demand (COD), biological oxygen demand (BOD), total organic carbon (TOC) and the biodegradability (BOD/COD) of the seawater. Response surface methodology-central composite design (RSM-CCD) and artificial neural network-Levenberg Marquardt (ANN-LM) statistical models were employed to optimize the photocatalytic biodegradability (BOD/COD). A quadratic polynomial statistical model was obtained to predict the percentage removal efficiencies of COD, TOC, BOD and biodegradability. For the experimental runs, the maximum percentage removal efficiencies for COD, TOC, BOD was found to be 62.3, 40.1, and 18.8%, respectively. Whereas, the maximum biodegradability was 0.036. As per RSM-CCD and ANN-LM statistical model method the maximum percentage removal efficiencies were found to be COD ​= ​58.14, 60.39%, TOC ​= ​33.74, 40.09%, BOD ​= ​18.47, 18.7% and Biodegradability ​= ​0.0315, 0.0360, respectively. The predicted values from statistical models were well correlated with experimental values. ANN modelling predicted better values for the responses with an average of R² ​= ​0.99697 than RSM modelling with average R² ​= ​0.8948.     

Anaerobic-anoxic-aerobic sequential degradation of synthetic wastewaters

This study was conducted in a continuous three-stage system of anaerobic (R1)-anoxic(R2)-aerobic (R3) reactors with synthetic wastewater containing phenol (1000 mg/L), chemical oxygen demand (COD) (3000 mg/L), CN⁻ (30 mg/L), SCN⁻(400 mg/L), and NH ₄ ⁺ -N (600 mg/L) as principal pollutants and well-acclimated heterogeneous microbial cultures. The final effluent was partially returned to R2 with a recycle ratio of 1. Anaerobic stage served to detoxify the feed by removing up to 80% of cyanide. Complete SCN⁻ removal and denitrification could be achieved in the anoxic stage by utilizing phenol as an internal source of carbon. Nitrification efficiency of 93% was obtained in the aerobic reactor. The results demonstrated that the three-stage system can give the desired final treated effluent quality (0 mg/L of phenol, 0.2 mg/L of CN⁻, 210 mg/L of COD, and 20 mg/L of NH ₄ ⁺ -N) and that the NO ₃ ⁻ -N concentration can be lowered by a higher recycle ratio.     

A comparative study for treatment of white liquor by different applications of Fenton process

In this paper, the treatability of white liquor by conventional (CFP), modified (MFP) and electro-Fenton oxidation processes (EFP) was investigated depending on the COD parameter. Based on the experimental results, up to 62.4%, 58.4% and 54.9% COD removals by the CFP, MFP and EFP were achieved, respectively. It was observed that adjustment of initial pH to acidic values is not required in the CFP. The optimal operational conditions were found to be [Fe²⁺] = 500 mg/L, [H₂O₂] = 1000 mg/L at pH 7.3 (original pH) in the CFP, [Fe⁰] = 1250 mg/L, [H₂O₂] = 1000 mg/L at pH 3 in the MFP, and I = 1.0 A, [H₂O₂] = 1500 mg/L at pH 3 in the EFP, respectively. As a result, the CFP has been determined as a more efficient alternative treatment method.     

Experimental design,machine learning approaches for the optimization and modeling of caffeine adsorption

In the current research, the sorption of caffeine on fresh and calcined Cu–Al layered double hydroxide was comparatively studied based on adsorption parameters, adsorption kinetics, and adsorption isotherm. Response surface methodology (RSM), support vector machine (SVM) and artificial neural network (ANN), as data mining methods, were applied to develop models by considering various operating variables. Different characterization methods were exploited to conduct a comprehensive analysis of the characteristics of HDL in order to acquire a thorough understanding of its structural and functional features. The Langmuir model was employed to accurately describe the maximum monolayer adsorption capacity for calcined sample (q_max) of 152.99 mg/g mg/g with R² = 0.9977. The pseudo-second order model precisely described the adsorption phenomenon (R² = 0.999). The thermodynamic analysis also reveals a favorable and spontaneous process. The ANN model predicts adsorption efficiency result with R² = 0.989. The five-fold cross-validation was achieved to evaluate the validity of the SVM. The predication results revealed approximately 99.9% accuracy for test datasets and 99.63% accuracy for experiment data. Moreover, ANOVA analysis employing the central composite design-response surface methodology (CCD-RSM) indicated a good agreement between the quadratic equation predictions and the experimental data, which results in R² of 0.9868 and the highest removal percentages in optimized step were obtained for RSM (pH 5.05, mass of adsorbent 20 mg, time of 72 min, and caffeine concentrations of 22 mg/L). On the whole, the findings confirm that the proposed machine learning models provided reliable and robust computer methods for monitoring and simulating the adsorption of pollutants from aqueous solutions by Cu–Al–LDH.     

Removal of COD,aromaticity and color of a pretreated chemical producing industrial wastewater: a comparison between adsorption,ozonation, and advanced oxidation processes

A wide range of products are produced in the chemical producing industry such as textile dyes, chemicals, printing dyes and chemicals, paper chemicals, electrostatic powder dyes, and optical brighteners. The aim of this study is to investigate the treatability of chemical oxygen demand (COD), aromaticity, and color in the wastewater of this sector, where highly complex chemicals are used. Most of the studies in the literature are related to the treatment of synthetically prepared dyed wastewater. This study is important as it is carried out with real wastewater and gives results of many treatment methods. In the study, COD, UV-vis absorbance, and color values were attempted to be removed from the wastewater of a chemical producing industry that was pretreated by coagulation-flocculation. The COD value of the pretreated wastewater discharged to the central treatment system was restricted as 1000 mg/L. Pretreated wastewater characterization is as follows: COD: 2117 mg/L, UV-vis absorbance values at; 254 nm: 9.91, 280 nm: 8.65, 341 nm: 12.77, 436 nm: 5.01, 525 nm: 2.24, and 620 nm: 1.59. In the study, adsorption, ozonation, and advanced oxidation processes (Fenton and persulfate oxidation) were used to remove COD and UV-vis absorbance values (aromaticity, organics, and color). The method by which the best removal efficiency was obtained for all parameters was the adsorption process using powdered activated carbon (PAC). The equilibrium PAC dose was found as 6 g/L. At this adsorbent dose, the removal efficiencies of UV-vis absorbance values were all around 99% and the efficiency of COD removal was 77%. The Langmuir isotherm constants were found to be q_max= 30.4 mg/g and K_L = 487.9 (L/mg). The COD concentration at this adsorbent dose was 486 mg/L and wastewater was suitable for discharge to the central wastewater treatment plant in that region.     

Enhanced three-dimensional electrochemical process using magnetic recoverable of Fe3O4@GAC towards furfural degradation and mineralization

Furfural is as one of the major environmental pollutants in different industrial effluents such as refinery and petrochemical, paper, cardboard and oil refining. This toxic chemical is irritant and causes allergy for skin, eyes and mucous membranes. This study was developed to investigate the efficiency of a three-dimensional electrochemical process in the presence of granular activated carbon magnetized with Fe₃O₄ (Fe₃O₄@GAC) particle electrodes for removal of furfural from aqueous solution. The particle electrodes structural and morphological featured were determined via BET, VSM, XRD, FE-SEM and FTIR techniques. The experiments were performed based on central composite design (CCD) and the role of influencing factors including reaction time, pH, voltage and initial furfural concentrations at five levels were evaluated. The Quadratic model with high correlation coefficient = 0.9872 (R² and (R²_Adj = 0.9724)) was suggested for experimental data analysis. The performance of electrochemical oxidation towards furfural degradation was enhanced substantially after adding Fe₃O₄@GAC. The highest furfural removal efficiency (98.2%) was achieved under optimal conditions (furfural: 201 mg/L, electrolysis time: 69 min, voltage: 19 V, and pH: 5.0). Besides, over 78 and 74 % of COD and TOC were removed by Fe₃O₄@GAC-based three-dimensional process, respectively. Based on the COD/TOC ratio and average oxidation state (AOS) index, a significant increase was observed in the biodegradability of intermediates of furfural after treatment. Results showed that three-dimensional electrochemical process with particle electrodes is a promising technology for efficient removal of furfural, even at high concentrations. Results of Liquid chromatography–mass spectrometry (LC-MS) analysis and degradation pathway showed that furfural could be oxidized to compounds with smaller molecular masses, which eventually converted to carbon dioxide and water.     

Thiazolylhydrazone dervatives as inhibitors for insect N-acetyl-β-d-hexosaminidase and chitinase

Insect chitinase and N-acetyl-β-d-hexosaminidases (Hex) are potential targets for developing new pesticides. Here, a series of thiazolylhydrazones I (with substituted group R₁ at N3) and II (with substituted group R₁ at N2) were designed, synthesised and evaluated as competitive inhibitors of OfHex1 and OfChi-h, from the agricultural pest Ostrinia furnacalis. Derivatives I-3d and II-3d, with phenoxyethyl group at R₁, demonstrated the best inhibitory activities against OfHex1 and OfChi-h. Molecular docking analysis indicated that the branched conformation compound II-3d (K_i = 1.5 μmol/L) formed more hydrogen bonds with OfHex1 than the stretched conformation compound I-3d (K_i = 5.9 μmol/L). The differences in compounds’ binding conformations with OfChi-h explained differences in inhibitory activity of compounds I-3d (K_i = 1.9 μmol/L) and II-3d (K_i = 4.1 μmol/L). This work suggests a novel scaffold for developing specific Hex and Chi-h inhibitors.     

Green synthesis of copper oxide nanoparticles CuO NPs from Eucalyptus Globoulus leaf extract: Adsorption and design of experiments

The study is concerned with synthesizing copper oxide nanoparticles with leaf extract Eucalyptus Globoulus. The results of scanning electron microscopy (SEM) and dynamic light scattering (DLS) revealed that the green synthesized copper oxide nanoparticles are spherical and have a mean particle size of 88 nm, with a negative zeta potential of ?16.9 mV. The XRD graph showed the crystalline and monoclinic phases of CuO nanoparticles. The average crystalline size around 85.80 nm was observed by the Debye–Scherrer formula. The adsorption characteristics of the nano-adsorbents were investigated using methyl orange, and the adsorption efficiency at room temperature attained 95 mg/g. Copper oxide nanoparticles (CuO NPs) adsorb methyl orange dye most effectively at pH 4.5 when the dye is applied in quantities of 0.04 g/50 mL. Box–Behnken design (BBD) in response surface methodology (RSM) was used to optimize various process parameters, such as pH solution (X₁: 2 – 11), adsorbing dose (X₂: 0.01 – 0.08 g/L), [MO] dye concentration (X₃: 10 – 80 mg/L). Overall, the adjusted coefficient of determination (R²) value of 0.99 demonstrated that the used model was quite appropriate, and the chosen RSM was effective in optimization the decolorization conditions of MO.     

Process Optimization and Modeling of Phenol Adsorption onto Sludge-Based Activated Carbon Intercalated MgAlFe Ternary Layered Double Hydroxide Composite

A sewage sludge-based activated carbon (SBAC) intercalated MgAlFe ternary layered double hydroxide (SBAC-MgAlFe-LDH) composite was synthesized via the coprecipitation method. The adsorptive performance of the composite for phenol uptake from the aqueous phase was evaluated via the response surface methodology (RSM) modeling technique. The SBAC-MgAlFe-LDH phenol uptake capacity data were well-fitted to reduced RSM cubic model (R² = 0.995, R²-adjusted = 0.993, R²-predicted = 0.959 and p-values < 0.05). The optimum phenol adsorption onto the SBAC-MgAlFe-LDH was achieved at 35 °C, 125 mg/L phenol, and pH 6. Under the optimal phenol uptake conditions, pseudo-first-order and Avrami fractional-order models provided a better representation of the phenol uptake kinetic data, while the equilibrium data models’ fitting follows the order; Liu > Langmuir > Redlich–Peterson > Freundlich > Temkin. The phenol uptake mechanism was endothermic in nature and predominantly via a physisorption process (ΔG° = −5.33 to −5.77 kJ/mol) with the involvement of π–π interactions between the phenol molecules and the functionalities on the SBAC-LDH surface. The maximum uptake capacity (216.76 mg/g) of SBAC-MgAlFe-LDH was much higher than many other SBAC-based adsorbents. The improved uptake capacity of SBAC-LDH was attributed to the effective synergetic influence of SBAC-MgAlFe-LDH, which yielded abundant functionalized surface groups that favored higher aqueous phase uptake of phenol molecules. This study showcases the potential of SBAC-MgAlFe-LDH as an effective adsorbent material for remediation of phenolic wastewater     

Synthesis and characterization of the unusual cluster [Ni2(GaAr′)2(η:η-μ2-C2H4)]: Ready addition of ethylene to Ni(COD)(GaAr′)2 at 25 °C and 1 atmosphere

The nickel (0) compound Ni(COD)(GaAr′)₂ (Ar′ = C₆H₃-2,6-(C₆H₃-2,6-i-Pr₂)₂), 1, was synthesized by the reaction of Ni(COD)₂ (COD = 1,5-cyclooctadiene) with (GaAr′)₂. Compound 1 reacted with ethylene at 25 °C and at 1 atm pressure to give the bimetallic cluster [Ni₂(GaAr′)₂(η¹:η¹-μ₂-C₂H₄)], 2, through the incorporation of one molecule of ethylene and displacement of COD. The structure of 2 featured an unusual Ni₂Ga₂C₂ core bicyclic structure in which the C₂H₄ moiety bridges the Ga···Ga edge of a Ga₂Ni₂ tetrahedron. The galliums each carry an η¹-bonded Ar′ substituent which complexes the nickel atom by an η⁶-π interaction with one of its flanking Ar’ rings.     

2-(1-Aryliminoethylidene)quinolylnickel(II) dibromides: Synthesis, characterization and ethylene dimerization capability

A series of 2-(1-aryliminoethylidene)quinoline derivatives (L1-L9) and the nickel(II) dibromides (C1-C9) thereof, were synthesized and characterized. The molecular structures of C2 (R¹ = Et, R² = H, R = Me) and C9 (R¹ = ⁱPr, R² = H, R = ⁱPr) were confirmed as being distorted tetrahedral at nickel by single crystal X-ray diffraction. On treatment with diethylaluminium chloride (Et₂AlCl) or ethylaluminum sesquichloride (EASC), these nickel pre-catalysts exhibited high activity for selective ethylene dimerization (0.89-3.29 × 10⁶ g mol⁻¹(Ni) h⁻¹) at 20 °C under 10 atm of ethylene. The influence of the reaction parameters on the catalytic behaviour was investigated for these nickel systems, including variation of Al/Ni molar ratio and reaction temperature.     

Fluorinated rhodium-phosphine complexes as efficient homogeneous catalysts for the hydrogenation of styrene in supercritical carbon dioxide

A fluorinated trisphenylphosphine ligand was reacted with [(COD)CIRh]₂ (COD = cyclooctadiene) and [(COD)₂Rh]⁺BArF⁻ {BArF = tetrakis[(3,5-bistrifluoromethyl)phenyl]borate} to synthesize new fluorinated derivatives of the well-known Wilkinson catalyst as {[P(Ph(CF₃)₂)₃]₃RhBArF}, {[P(Ph)₃]₃RhBArF} and {[P(Ph(CF₃)₂)₃]₃RhCl}. BArF anion was used to synthesize cationic complexes. All the synthesized complexes were tested and found to be soluble in supercritical carbon dioxide (scCO₂) media. The catalytic activities of the rhodium complexes were examined for hydrogenation of styrene in scCO₂. The catalysts showed different activities between 47.9–77.4%. The most effective result among the synthesized Rh-catalysts was obtained with a conversion of 77.4% corresponding to {[P(Ph(CF₃)₂)₃]₃RhBArF} under the reaction conditions of 343K temperature and 123 bar pressure after 8 h in scCO₂ (molar ratio of substrate to catalyst = 500).     

Kinetics of wet air oxidation of sodium sulfide over heterogeneous iron catalyst

Wet air oxidation (WAO) is an established technique for reducing the chemical oxygen demand (COD) of refinery sulfidic spent caustic waste. In the present work, the heterogeneous form of the cheap and abundant catalyst ferrous sulfate (FeSO₄) was employed for WAO of sodium sulfide. The performance of this catalyst in the oxidative destruction of this model compound is thus far unfamiliar. Kinetic data for the non-catalytic and catalytic oxidation processes was collected in a batch reactor. For the catalytic process, temperature (T), oxygen partial pressure () and catalyst concentration (ω) were varied in the ranges 80-150°C, 0.69-2.06 MPa and 0.8-2.4 g/L respectively. Around 94% COD was destroyed within 1 h when feed containing 8 g/L of sulfide was oxidized at T = 100°C, = 0.69 MPa, and ω = 0.8 g/L. First, the data on disappearance of COD were fitted to a power law model and reaction rate constants were determined. The activation energy for the non-catalytic (91 kJ/mol) and catalytic (50 kJ/mol) oxidation process was found from the temperature dependence of the rate constants. Second, hyperbolic models based on Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-L) kinetics were used for fitting kinetic data. It was found that the L-H model suggesting dissociative adsorption of oxygen provided the best fit. In this way, a deep insight into oxidation kinetics of sodium sulfide was provided.     

高浓度含酚废水中酚类的转化回收及脱除

以含量30 g/L的苯酚水溶液为模型,提出氯化联合氧化工艺,实现对高浓度含酚废水中苯酚的转化回收及残余酚类的氧化脱除。 首先以pH值作为指示,向溶液中引入足够量的氯离子和氢离子,通过加入氯酸钠与之反应定量产生氯气;在所控制的实验条件下,氯气与溶液中的苯酚选择性反应转化为低溶解度的三氯苯酚沉淀,经气相色谱-质谱（GC-MS）面积归一法测得其含量可达97.76%;过滤所得滤液化学需氧量（COD）降低至1125 mg/L,苯酚回收率约98.7%。 采用Fenton氧化技术对该滤液进行氧化降解,结果表明,在优化的实验条件pH=3、Fe2+浓度为1 mmol/L下,H2O2用量为15 mL/L时,残余的氯酚类即可以被有效降解,降解后的水样经调碱性将铁或亚铁离子沉淀后为无色透明的溶液;联合处理后,水样COD减小到52 mg/L,该值满足国家工业污水排放标准。     

Production of a water disinfectant by membrane electrolysis of brine solution and evaluation of its quality change during the storage time

Anolyte solution produced by membrane electrolysis of NaCl solution contains a high level of available chlorine content (ACC) and other oxidizing compounds, rendering this solution a strong disinfectant property. In this paper, some process parameters affecting the anolyte production efficiency, such as total inlet flow (240–320 L/h), saline solution concentration (1.65–3.50 g/L), and the type of membrane (cation exchange, anion exchange, and bipolar membranes) were investigated in an electrolysis cell. Changes in the quality of anolytes produced at three initial concentrations of very high (ACC₁ = 816.5 mg/L), relatively high (ACC₂ = 461.5 mg/L), and medium (ACC₃ = 355.0 mg/L) during storage (from the production up to 20 weeks) were examined by adjusting the total inlet flow, saline concentrations, and membrane types. Changes in the ACC of the produced anolyte solution were generally affected by the type of membrane used in the electrolysis cell. The use of anion exchange membrane resulted in the lowest durability of anolyte quality (60–80% ACC reduction after 4 weeks of storage) and the cation exchange membrane had the highest durability (less than 40% decrease after 4 weeks of storage). In addition, changes in the pH and the oxidation–reduction potential of the anolyte were investigated during the storage period, which had a different trend depending on the type of applied membrane.     

Intensified removal of 4-Methylpyridine by ultrasonication in presence of advanced oxidants

Water contamination is a big issue in every part of the globe. In response to the rising demand for wastewater with lower pollutant levels, a unique enhanced oxidation technique called ultrasound assisted irradiation has been developed. In the current study, advanced oxidising technology is used to accelerate the breakdown of 4-Methylpyridine (4 MP) utilising ultrasound at a rated frequency of 22 ± 2 KHz. In the presence of ultrasound, the effects of advanced oxidising agents as well as the effects of different operational factors like pH, time, and power were evaluated. The kinetics for degradation of 4 MP were evaluated by second order model. The combined strategy of ultrasound assisted degradation in the presence of various advanced oxidising agents like hydrogen peroxide (H₂O₂), peroxymonosulphate (PMS), potassium per sulphate (KPS) and Fenton reagent was investigated at optimal operating conditions, with the starting concentration of 50 mg/L at pH 9, and temperature 45⁰C. When applying ultrasound at its highest rated power of 120 W while the Fenton reagent was present, the maximum degradation was recorded to be 99 ± 1%. The scavenger effect of ^?OH free radical andions was evaluated on degradation of 4 MP. The synergetic index for all combination approaches was determined, for US/Fenton maximum synergetic index 10.8 established. The tentative degradation pathway was studied for degradation of 4 MP.     

Fe-Mn-Cu-Ce/Al2O3 as an efficient catalyst for catalytic ozonation of bio-treated coking wastewater: Characteristics,efficiency, and mechanism

It is important to develop a catalyst that has high catalytic activity and can improve the degradation efficiency of refractory organic pollutants in the catalytic ozonation process. In this study, Fe-Mn-Cu-Ce/Al₂O₃ was synthesised via impregnation calcination for catalytic ozonation of bio-treated coking wastewater. The physical and chemical characteristics of the catalysts were analysed using X-ray diffraction (XRD), X-ray fluorescence spectrometry (XRF), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller nitrogen adsorption–desorption methods. The effects of catalyst dosage, pH, and reflux ratio on the degradation efficiency of wastewater were examined in laboratory-scale experiments. The chemical oxygen demand (COD) removal rate of bio-treated coking wastewater was estimated to be 52.76 % under optimal conditions. The experiments on the catalytic mechanism demonstrated that the surface hydroxyl formed by the Lewis acid sites on the surface of the catalyst can react with ozone as the active site forming the active oxygen (·OH, ·O₂^–, and ¹O₂), thereby efficiently degrading the organic pollutants in coking wastewater. Furthermore, a pilot-scale experiment on the catalytic ozonation of bio-treated coking wastewater was carried out using an Fe-Mn-Cu-Ce/Al₂O₃ catalyst, while the effects of the initial pollutant concentration, ozone concentration, and gas flow on the COD removal rate were studied on a pilot scale. It was found that the COD removal rate of the wastewater was ～ 60 % under optimal parameters. After the treatment, the wastewater steadily reached the coking wastewater discharge standard (COD < 80 mg/L), while the operating cost of catalytic ozonation reached ～ 0.032$/m³, thereby paving the way toward economic engineering applications. The COD degradation kinetics in the bio-treated coking wastewater followed pseudo-second-order kinetics. Three-dimensional fluorescence and gas chromatography–mass spectrometry revealed that macromolecular organic pollutants in the bio-treated coking wastewater were greatly degraded. In summary, Fe-Mn-Cu-Ce/Al₂O₃ exhibited good reusability, high catalytic activity, and low cost and has a wide application prospect in the treatment of coking wastewater.     

Preparation and photocatalytic activity of TiO<Subscript>2</Subscript> films with Ni nanoparticles

Titania thin films were synthesized by sol–gel dip-coating method with metallic Ni nanoparticles synthesized separately from an organometallic precursor Ni(COD)₂ (COD = cycloocta-1,5-diene) in presence of 1,3-diaminopropane as a stabilizer. Titania was obtained from a titanium isopropoxide precursor solution in presence of acetic acid. A Ni/TiO₂ sol system was used to coat glass substrate spheres (6, 4 and 3 mm diameter sizes), and further heat treatment at 400 °C was carried out to promote the crystallization of titania. XRD analysis of the TiO₂ films revealed the crystallization of the anatase phase. Transmission Electron Microscopy (TEM) and High Resolution TEM studies of Ni nanoparticles before mixing with the TiO₂ solution revealed the formation of Ni nanostructures with an average size of 5–10 nm. High-angle annular dark-field images of the Ni/TiO₂ system revealed well-dispersed Ni nanoparticles supported on TiO₂ and confirmed by AFM analysis. The photocatalytic activity of the Ni/TiO₂ films was evaluated in hydrogen evolution from the decomposition of ethanol using a mercury lamp for UV light irradiation. Titania films in presence of Ni nanoparticles show higher efficiency in their photocatalytic properties in comparison with TiO₂.     

Determination of Phenol in Surface Waters by High-Performance Liquid Chromatography with Sorption Preconcentration

The retention of phenol and its derivatives on Silasorb C₈ and PepRPC ^TMHR 5/5 was studied. Both columns are suitable for the separation of pyrocatechol–phenol–o-cresol(p-cresol)–2,6-xylenol mixtures using mobile phases containing 10–20 vol % of isopropanol and 1% glacial acetic acid in water. A procedure was developed for determining phenol with a detection limit of 4 mg/L (acetonitrile; signal-to-noise ratio, 2; loop volume, 25 L). With preconcentration from 1-L samples in a Diapak-phenol/P cartridge, the procedure allows phenol to be determined in water samples with a detection limit of 4 g/L. The procedure was used in analyses of samples of river and tap water.     

Electro-catalytic effect of Al2O3 supported onto activated carbon in oxidizing phenol at graphite electrode

In this work, the electro-catalytic oxidation of phenol was studied using the aluminum oxide supported onto activated carbon (Al₂O₃/AC). The later was successfully prepared by impregnating aluminum particles in the activated carbon (AC) using heat treatment. Al₂O₃/AC was characterized by X-ray diffraction (XRD) and infrared spectroscopy (IR). The electro-catalytic performance of the Al₂O₃/AC for phenol oxidation was studied using cyclic voltammetry (CV), chronoamperometry, linear sweep voltammetry polarization, electrochemical impedance spectroscopy and differential pulse voltammetry (DPV) in 0.1 mol L^?1 Na₂SO₄. It has been shown that the proposed catalyst exhibits remarkably an electro-catalytic performance toward phenol oxidation. Moreover, the oxidation peak currents are linearly dependent on the concentration of phenol in the wide ranges from 1.0 × 10^?3 mol L^?1 to 1.0 × 10^?4 mol L^?1 and 8.0 × 10^?5 mol L^?1 to 1.0 × 10^?6 mol L^?1 with a detection limit of 1.51 × 10^?7 mol L^?1 (signal (S) to noise (N) ratio, S/N = 3) and response time of 3 min. The possible interferences were evaluated in 1.0 × 10^?5 mol L^?1 of phenol. The proposed catalyst also indicated suitable repeatability and stability. Moreover, the proposed Al₂O₃/AC–CPE has been successfully applied for the phenol analysis in natural waters and olive oil samples with good recoveries.