Reaction of coals in hot acidic phenol at constant acid concentration

Previous work showed that the efficient ‘depolymerization’ of bituminous coals in hot phenol containing p-toluenesulphonic acid failed to occur and that the acid was destroyed during the reaction. Four coals varying in rank from lignite to low volatile bituminous were treated with refluxing phenol containing p-toluenesulphonic acid with the acid concentration held constant. The amount of colloidal material, of pyridine-soluble material, of benzene—ethanol solubles, and the number average molecular weight of the pyridine extractables were measured as a function of time. Although the reaction proceeds better with the lower rank coals, a large portion of the products is colloidal material. Treatment of coals with hot acidic phenol does not lead to their complete depolymerization. Treatment of Bruceton coal with refluxing phenol saturated with BF₃ also failed to give complete depolymerization. The formation of colloidal suspensions during investigations employing spectral and other physical measurements may lead to results that are susceptible to misinterpretation.     

Highly polar polymeric sorbents: Characterization and sorptive properties towards phenol and its derivatives

Six porous copolymers of acrylonitrile (AN)/divinylbenzene (DVB) and methacrylonitrile (MAN)/DVB have been synthesised by suspension polymerization in the presence of inert diluents. They have different specific surface area (460–720 m²/g for AN/DVB and 560–730 m²/g for MAN/DVB) and contain various amounts of the strongly polar nitrile groups. Their sorptive properties have been studied using dilute (0.5 mmol) solutions of phenol and its derivatives (o-chlorophenol, o-, m- and p-nitrophenol, 2,3- and 2,6-dimethylphenol, p-hydroxyphenol). It has been found that sorption of the most hydrophobic compounds and compounds capable of forming strong intramolecular hydrogen bonds does not depend on the polarity of the polymer surface. Sorption of phenol and m- and p-nitrophenol is stronger on sorbents having more polar groups. The influence of these groups on the sorption process is highly significant in the case of hydrophilic, water soluble sorbates such as p-hydroxyphenol. Polymeric sorbents were characterized using elemental analysis, inverse gas chromatography and their porous structure was characterized by nitrogen adsorption at 77 K.     

Effects of ultrasound on electrochemical oxidation mechanisms of p-substituted phenols at BDD and PbO2 anodes

The effects of low-frequency (40 kHz) ultrasound are investigated with regard to the effectiveness and mechanisms of electrochemical oxidation of p-substituted phenols (p-nitrophenol, p-hydroxybenzaldehyde, phenol, p-cresol, and p-methoxyphenol) at BDD (boron-doped diamond) and PbO₂ anodes. Although ultrasound improved the disappearance rates of p-substituted phenols at both the BDD and PbO₂ anodes, the degree of enhancement varied according to the type of p-substituted phenol and type of anode under consideration. At the BDD anode, the %Increase values were in the range 73-83% for p-substituted phenol disappearance and in the range 60-70% for COD removal. However, at the PbO₂ anode, the corresponding %Increase values were in the range 50-70% for disappearance of p-substituted phenols and only 5-25% for COD removal, much lower values than obtained at the BDD anode. Further investigations on the influence of ultrasound on the electrochemical oxidation mechanisms at BDD and PbO₂ anodes revealed that the different increase extent were due to the specialized electrochemical oxidation mechanisms at these two anodes. The hydroxyl radicals were mainly free at the BDD electrodes with a larger reaction zone, but adsorbed at the PbO₂ electrodes with a smaller reaction zone. Therefore, the enhancement due to ultrasound was greater at the BDD anode than at the PbO₂ anode.     

Utilization of bagasse fly ash generated in the sugar industry for the removal and recovery of phenol and p-nitrophenol from wastewater

Bagasse fly ash, a waste generated in local sugar industries, has been converted into a low cost adsorbent. The product so obtained has been characterized and used for the removal of phenol and p-nitrophenol. Investigations include the effect of pH, sorbent dosage, phenol concentration and the effect of surfactants on the uptake of phenol and p-nitrophenol. The adsorption data follow both Langmuir and Freundlich models. Isotherms have also been used to obtain the thermodynamic parameters of the process. Some experiments have also been performed with a view to recover phenols and have in-situ chemical regeneration of the spent carbon column. © 1998 SCI.     

Comparative sorption kinetic studies of phenolic compounds on fly ash and impregnated fly ash

The factors affecting the rate processes involved in the removal of phenolic compounds, e.g. initial phenol concentration, particle size, impregnation of fly ash (IFA), pH and temperature have been studied. The removal rate of phenols varied in the order p-nitrophenol m-nitrophenol > o-nitrophenol > p-cresol > phenol > m-cresol > o-cresol. The process followed first order rate kinetics. The sorption data generally fit the Lagergren equation and the intraparticle diffusion rate equation from which adsorption rate constants, diffusion rate constants and diffusion coefficients were determined. Intraparticle diffusion was found to be the rate-limiting step. These kinetic parameters were compared for various phenols under different conditions using fly ash (FA) and impregnated fly ash (IFA).     

Application of different equations to adsorption isotherms of phenolic compounds on activated carbons prepared from cork

Activated carbons were prepared from solid cork wastes by physical activation with carbon dioxide or steam, and chemical activation by impregnation with phosphoric acid. In this work we show the possibility of using these activated carbons for the adsorption of phenolic compounds from the aqueous phase. The materials present a different response to the adsorptives used (p-nitrophenol, p-chlorophenol, p-cresol and phenol), depending on the type of activation and the parameters (burn-off, absolute concentration) used in each case. All the samples were capable of retaining the contaminants, with the best result being reached by the sample with higher burn-off and the worst with the carbonised, while intermediate values were reached with the remaining samples. The experimental isotherms were analysed with two and three parameters equations (Freundlich, Langmuir, Dubinin-Radushkevich-Kaganer and Redlich-Peterson). The results obtained from the application of the equations are similar in some aspects, but the degree of confidence is quite different. The best fit was achieved with the Redlich-Peterson equation, which can be explained by the fact that this has three adjustable parameters. However, overall the Freundlich and DRK equations appear to be more useful and provide parameters which can be correlated with the structural characteristics of the solids obtained from N₂ adsorption measurements.     

Cometabolic degradation of para-nitrophenol and phenol by Ralstonia eutropha in a Kissiris-immobilized cell bioreactor

Ralstonia eutropha was able to degrade p-nitrophenol (PNP) at concentrations ranging from 5 to 15mg l ^?1 in the presence of phenol which was kept at the constant concentration of 200 mg l ^?1. More than 90% of phenol was degraded within 30 h and in the absence of PNP. While in this time period and in the presence of 15 mg l ^?1 less than 30% of phenol was degraded and PNP removal ability of the test bacterium was about 20%. Kissiris as a natural source of silicon dioxide having a very rigid structure with many micropores irregularly distributed throughout its surface was used to evaluate effectiveness of the cell immobilization using a Kissiris-immobilized cell bioreactor [ICB]. By applying phenol-feeding regime in the ICB operated in a batch recycling mode, simultaneous degradation of phenol in total amount of 1,000 mg l ^?1 with 15 mg l ^?1 PNP was achieved within 40 h.     

Depolymerization of Turkish lignites. 2. Effect of phenol concentration in a closed system

A lignite (C, 66.9 wt%) was depolymerized, using sulphuric acid as a catalyst, in a closed system in which the phenol/coal ratio was varied from 1.5 to 10. The products were separated by solvent extraction and silica gel chromatography. The i.r. and n.m.r. spectra, and the molecular weight of the products were measured. In the experiments with a phenol/coal ration of 10, complete depolymerization of the coal was seen provided the temperature of depolymerization was at least 210 °C. The products generally contained disubstituted aromatic structures connected by methylene bridges, it was found that as the phenol/coal ratio was increased there was a decrease in the number of methylene bridges connecting the aromatic structures. The molecular weights of the straight-chain pentane and benzene-soluble material were lower than the molecular weights of similar fractions in depolymerization experiments carried out in open systems. A method for the structural analysis of straight-chain pentane and benzene-soluble material based on i.r., ¹H n.m.r. and molecular weight measurements is suggested.     

Effect of initial solution apparent pH on nano-sized nickel catalysts in p-nitrophenol hydrogenation

The effect of initial solution apparent pH (pH_a) on nano-sized nickel in the catalytic hydrogenation of p-nitrophenol to p-aminophenol was investigated in detail. Experimental results show that the catalytic activity of the nano-sized nickel shows a strong dependence on the initial solution pH_a, and is the highest at the initial solution pH_a 4.8. At lower or higher pH_a values the nano-sized nickel will obviously deactivate, but the deactivation mechanisms are fully different. With respect to the former, the nickel dissolution and the strong adsorption of the complex compound of nickel ion and p-nitrophenol on the surface of nano-sized nickel are the main reasons. The severe agglomeration of nickel particles also causes the deactivation of nickel used at the initial solution pH_a 1.6. For the latter the main reasons are the formation of nickel hydroxide surface species and the decrease of p-nitrophenol adsorption on the hydrogenation sites.     

Absorption of chlorine in aqueous solutions of phenols and aromatic sulfonic acids

The kinetics of absorption of Cl₂ in aqueous solutions of phenol, o-chlorpophenol, p-chlorpophenol, p-nitrophenol, m-aminophenol-hydrochloride, ptoluenesulfonic acid and m-nitrobenzenesulfonic acid, at 30°C, was studied in a model stirred contactor, with a plane liquid interface and independent stirrers for gas and liquid phases. A laminar jet apparatus was also used to study the kinetics of chlorination of aqueous p-toluenesulfonic acid and m-aminophenol-hydrochloride. All the reactions were found to be first order in Cl₂ and first order in the dissolved organic substance. The values of second order rate constants at 30°C varied from about 1.1 x 10⁶ to 5.7 x 10⁹ cm³/g mole sec for phenolic substances and from 1.1 x 10⁶ to 3.5 x 10⁶, cm³/g mole sec for the sulfonic acids.Chlorination of o- and p-chlorophenol in aqueous buffered solutions was analysed on the basis of absorption of Cl₂ followed by two parallel fast pseudo-first order reactions, where the hydrolysis of Cl₂, catalysed by buffer anion, and the chlorination of chlorophenol were found to occur in the liquid film.Measurements of the effective interfacial area and the liquid-side mass transfer coefficient were made in a mechanically agitated contactor and a bubble column by using some of these chlorination reactions.     

Enhanced electrochemical treatment of phenolic pollutants by an effective adsorption and release process

Phenolic compounds are the most prevalent pollutants in industrial wastewater. Here we report on a novel approach: using adsorption and release process to improve the efficiency of electrochemical oxidation of phenolic pollutants. To illustrate this innovative technique, three phenolic compounds, phenol, p-nitrophenol (p-NPh) and p-cresol, were selected as model pollutants. The adsorption studies were carried out by adsorbing the three pollutants onto a hyper-cross-linked resin (Purolite Macronet MN-200). The adsorption isotherms, adsorption kinetics and the effect of temperature on adsorption were systematically investigated. Our experimental results have shown that the MN-200 resin exhibits a high removal efficiency of the three model pollutants and the adsorbed phenolic compounds can be efficiently released in a NaOH solution. The preconcentrated phenolic compounds were further treated using electrochemical oxidation at the Ti/SnO₂-Sb₂O₅-IrO₂ electrode. The first-order model fits the kinetics data of the electrochemical oxidation very well, showing that the degradation rate constant decreases in the order of p-NPh > phenol > p-cresol. Our study has demonstrated that the integration of the effective preconcentration process and the advanced electrochemical oxidation offers a promising approach for the efficient elimination of phenolic pollutants in wastewater.     

On the interactions of phenol, aniline and p-nitrophenol on activated carbon surfaces as detected by TPD

The interactions of phenol, aniline and p-nitrophenol, adsorbed from aqueous solutions, with the surface of two activated carbons (with and without oxygen surface groups) were followed by temperature programmed desorption, thermogravimetry and analysis by mass spectrometry. The results reveal that on bare surface the three molecules can be presented as physisorbed and chemisorbed species. When oxygen surface groups are introduced on the carbon surface, there is a change in the adsorption/desorption behaviour; in such a way that the phenol chemisorption is inhibited and that decomposition of aniline and nitrophenol are originated.     

Depolymerization of Yallourn brown coal: 1. Reduction of molecular weight with repeated reaction

Yallourn (Australian) brown coal (66.6 wt% C) was depolymerized three times in phenol, using p-toluenesulphonic acid as catalyst. After each reaction the product was extracted with pyridine. The pyridine extracts were then methylated and fractionated by g.p.c. to obtain the molecular weight distribution. The yield of lower molecular weight material increased with advancing reaction.     

微波场中两种吸波材料氧化处理p-硝基酚溶液

考察了活性炭和炭化硅两种材料的吸波能力和微波辅助氧化处理p-硝基酚(PNP)溶液的情况.对活性炭固定床而言,1618 mg•L^-1 PNP溶液的微波去除率和矿化率分别为96%和91%,而炭化硅固定床上的去除率和矿化率则最高为73%和24%.3种高浓度(3540、6858 mg•L^-1和11095 mg•L^-1)PNP溶液在活性炭固定床上的微波降解率均大于98%,矿化率均高于96%.活性炭和炭化硅微波辅助氧化降解PNP的中间产物同为o-硝基酚、苯酚和苯醌.活性炭固定床微波降解PNP溶液后出水的可生化性得到明显提高.     

Comparative sorption equilibrium studies of toxic phenols on flyash and impregnated flyash

In the present study, the sorption of toxic phenols, which include phenol, o-cresol, m-cresol, p-cresol, o-nitrophenol, m-nitrophenol and p-nitrophenol, has been investigated. The influences of various factors, such as particle size, impregnation of flyash (IFA), pH and temperature on the sorption capacity have been studied. Equilibrium modelling has been carried out using Langmuir and Freundlich isotherm equations and constants have been calculated under different conditions. Thermodynamic studies have also been carried out and values of standard free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) calculated.     

褐煤活性炭吸附苯酚的研究

The feasibility and adsorption effect of lignite activated carbon for phenol removal from aqueous solutions were evaluated and investigated. A series of tests were performed to look into the influence of various experimental parameters such as contact time, initial phenol concentration, temperature, and pH value on the adsorption of phenol by lignite activated carbon. The experimental data were fitted well with the pseudo-second-order kinetic model. The adsorption is an endothermic process and conforms to Freundlich thermodynamic model. The results indicate that the lignite activated carbon is suitable to be used as an adsorbent material for adsorption of phenol from aqueous solutions.     

Electrooxidation of p-nitrophenol on organobentonite modified electrodes

A natural bentonite, modified with different quaternary ammonium cations, hexadecyl trimethylammonium, (HDTMA), dodecyl trimethylammonium (DTMA) and tetramethylammonium (TMA), was used as an electrode material in a p-nitrophenol (p-NP) electrooxidation. On the basis of electrochemical response, TMA-modified bentonite (TMA-B) electrode was chosen for further investigations. The influence of TMA loading on the electrochemical properties of the TMA-B electrodes toward p-NP electrooxidation was examined. Electrode sensitivity toward p-NP was performed. The detection limit for p-NP of 1 · 10^− 6 mol dm^− 3 was obtained.     

Depolymerization of Turkish lignites: 3. Effect of ultraviolet radiation

The effect of u.v. radiation on the product distribution of the acid-catalysed depolymerization reaction of a lignite (C, 66.9wt%) has been investigated. The products are separated by solvent extraction and silica gel chromatography and their ¹H n.m.r. spectra and molecular weights are also measured. Larger amounts of solubilized material are formed in the u.v.-irradiated depolymerization experiments due to a greater amount of phenol incorporation in the reactions. The relative molar masses of products are lower than those obtained from thermal depolymerization experiments and they contain less hydroaromatic structures connected by fewer methylene bridges. It is suggested that u.v. radiation is making the coal more accessible for phenol in the depolymerization reactions.     

氯代硝基苯类废水臭氧化动力学和机理

采用半连续臭氧化工艺处理氯代硝基苯类废水,对氯代硝基苯（ClNBs）臭氧化过程反应动力学、臭氧分子与自由基氧化反应的贡献、过程降解机理等方面进行了研究。结果表明,ClNBs降解遵循准一级反应动力学,降解速率顺序为o-CNB相似文献   

Electropolymerization of phenol, o-nitrophenol and o-methoxyphenol on gold and carbon steel materials and their corrosion protection effects

This paper reports the results of a comparative study of the electropolymerization of phenol, o-methoxyphenol and o-nitrophenol by cyclic voltammetry on gold and carbon steel electrodes. The aim of this work is to synthesize homogeneous and adherent polyphenols film to protect carbon steel material against corrosion. Gold electrodes were used to optimize the experimental parameters such as the initial concentration of the monomer, the pH, the potential scan rate and the anodic potential limit value. Results showed that poly-o-metoxyphenol synthesized on carbon steel using optimized parameters obtained from gold electrode leads to more effective protection. This is probably due to the electron-donating mesomeric effet (+M) of the methoxy group which stabilized the phenoxy radicals obtained during the monoelectronic discharge of o-methoxyphenol. The best electropolymerization conditions involved an aqueous solution of 0.04 M o-methoxyphenol at pH 10.7, 5 mV s⁻¹ potential scan rate and an anodic potential limit (1.64 V/SCE) avoiding the degradation of the polymer film. The application of these conditions on steel electrodes leads to the formation of a stable, adherent and inhomogeneous film of polymer. A polymerization mechanism was proposed with consideration of results from literature.