Enhanced effect of suction-cavitation on the ozonation of phenol

800mL of 1.0mM phenol-containing aqueous solution was circulated at 20°C for 30 min in a suction-reactor, while 3.2 mg min(-1) ozone was introduced into the solution under the suction orifice. The removal rates of phenol vary polynomially with the orifice diameter as well as the suction pressure. The rate constant for the zero-order kinetics achieves the highest value at -0.070 MPa by using 5mm orifice. Although the suction-cavitation alone cannot remove phenol in 30 min, it can considerably enhance the ozonation of phenol. The rate constants for the zero-order kinetics by the simple ozonation and the combined method are 0.018 and 0.028 min(-1), respectively. Furthermore, no ozone was observed in the tail gas during the first 15 min for the ozonation in the suction reactor, and then the concentration of unreacted ozone slowly increased, indicating that the utilization rate of ozone is significantly improved by the suction-cavitation. The increasing input concentration of ozone obviously accelerates the ozonation of phenol, but the total required quantities of ozone are very close by various ozone input concentrations to reach the same degradation rate, indicating the ozonation assisted by the suction-cavitation can be considered as a quantitative reaction.     

Catalytic ozonation of phenol in water with natural brucite and magnesia

Natural brucite and magnesia were applied as catalysts in catalytic ozonation of phenol in this work. It was found that both brucite and magnesia had remarkable accelerations on degradation of phenol and removal of COD in water. On this basis, effective and feasible routes for catalytic ozonation of phenol in water were proposed. The influence of initial pH value, radical scavengers and reaction temperature were investigated. The results revealed that there were different ozonation mechanisms in two systems: molecular ozone direct oxidation mechanism was proved in catalytic ozonation with brucite, and hydroxyl radical mechanism was demonstrated to play a main role in catalytic ozonation with magnesia.     

In situ ozonation of anthracene in unsaturated porous media

Soil column experiments were conducted to investigate the effect of ozonation duration, contaminant content, particle size, moisture content, OH radical scavenger and soil organic matter on the removal of anthracene by in situ ozonation. In the whole study, the gas flow rate was 100 mL/min and concentration of gaseous ozone was 40 mg/L. The removal efficiency increased with the elapsed time, but the removal rate decreased in the range of 0–90 min. As anthracene content in sand decreased from 50 to 10 mg/kg, the removal efficiency increased from 42.1% to 62.0%, and ozone passed through soil column more rapidly. However, the ozone effectiveness reduced when anthracene content dropped. Small particle size provides a large interfacial area, which led to the high removal efficiency and long ozone breakthrough time in the column. The profile of residual anthracene in soil column varied more greatly at smaller particle size. The removal efficiency reduced when the moisture content rose from 0% to 9.1%. The ozone breakthrough time also decreased with the increasing moisture content. The presence of sodium bicarbonate or humic acid reduced the removal efficiency to some extent. GC–MS was employed in this study to determine 9,10-anthraquinone as the main ozonation product.     

Degradation of tetracycline in aqueous media by ozonation in an internal loop-lift reactor

The degradation of tetracycline by ozone was investigated in this paper. In the laboratory scale experiments, the effect of major parameters, including pH, gas flow rate, gaseous ozone concentration, hydrogen peroxide concentration and hydroxyl radical scavenger (tert-butyl alcohol) on the degradation of tetracycline was studied. A pseudo-first order kinetic model was used to simulate the experimental results. The results indicated that the tetracycline degradation rate increased with pH, gaseous ozone concentration and gas flow rate. The addition of hydrogen peroxide or hydroxyl radical scavenger had little effect on tetracycline removal, indicating that the direct oxidation of tetracycline by ozone was dominant process and the radical contribution to the tetracycline oxidation could be neglected. The main intermediates were separated and identified as well as the simple degradation pathway of tetracycline was proposed. The COD removal reached to 35% after 90 min reaction. The acute toxicity experiments illustrated that the Daphnia magna mortality reached the maximum after 25 min ozonation and then decreased to zero after 90 min ozonation.     

活性竹炭对苯酚的吸附动力学

研究了30℃下活性竹炭对苯酚溶液的吸附动力学,考察了苯酚初始浓度和吸附剂粒径的影响,并用三种动力学模型进行了拟合.结果表明:活性竹炭对苯酚的吸附动力学过程可以用准二级模型进行很好的描述,拟合所得的初始吸附速率随着苯酚浓度的增加和竹炭粒径的减小而提高.颗粒内扩散模型分析表明,活性竹炭对苯酚溶液的吸附过程中,颗粒内扩散为主要速率控制步骤.     

Treatment of phenol in synthetic saline wastewater by solvent extraction and two-phase membrane biodegradation

Phenol in synthetic saline (100gL(-1) NaCl) and acidic (pH 3) wastewater was treated by a hybrid solvent extraction and two-phase membrane biodegradation process at 30 degrees C. Kerosene was adopted to be the organic solvent because it was biocompatible and had a suitable partition coefficient for phenol. Phenol in water was first extracted by kerosene in a batch stirred vessel and the loaded solvent was passed through the lumen of a polyvinylidene fluoride (PVDF) hollow-fiber membrane contactor; in the meantime, Pseudomonas putida BCRC 14365 in mineral salt medium was flowed across the shell, to which tetrasodium phyophosphate (1gL(-1)) was added as a dispersing agent. The effect of the initial phenol level in wastewater (110-2400mgL(-1)) on phenol removal and cell growth was experimentally studied. At a cell concentration of 0.023gL(-1), it was shown that the removal of phenol from saline wastewater was more efficient at a level of 2000mgL(-1) when 0.02-m(2) membrane module was used. The effects of bigger membrane module size (0.19m(2) area) and higher initial cell concentration (0.092-0.23gL(-1)) on the performance of such a hybrid process for the treatment of higher-level phenol in saline wastewater was also evaluated and discussed.     

Characteristics of phenol biodegradation in saline solutions by monocultures of Pseudomonas aeruginosa and Pseudomonas pseudomallei

Phenol is a highly toxic and carcinogenic compound and its biodegradation is very important to meet the environmental regulations. Two bacterial strains capable of utilizing phenol as a sole source of carbon were isolated from the wastewater of a pharmaceutical industry. On the basis of morphological and biochemical characteristics these strains were identified as Pseudomonas aeruginosa and Pseudomonas pseudomallei. Both of these strains were very efficient for phenol degradation. P. pseudomallei degraded phenol at a maximum concentration of 1500 mg L(-1) within seven days with a specific growth rate of 0.013 h(-1) and phenol degradation rate of 13.85 mg L(-1)h(-1). Maximum initial concentration of phenol utilized by P. aeruginosa was 2600 mg L(-1) with 0.016 h(-1) specific growth rate and 26.16 mg L(-1)h(-1) phenol degradation rate. Moreover, the effect of various salts i.e., NaCl, KCl, Na(2)SO(4) and K(2)SO(4) on the growth of these strains and phenol degradation rate (at 1000 mg L(-1)) was studied. In the presence of these salts, P. aeruginosa showed up to 1.53 and 1.34 times faster phenol degradation rate and specific growth rate, respectively as compared to P. pseudomallei. In addition, P. aeruginosa exhibited higher chemical oxygen demand (COD) and biochemical oxygen demand (BOD) reduction rates as compared to the strain P. pseudomallei.     

Isothermal kinetics of sorption in porous media

A system of quasi-linear parabolic equations describing nonisothermal sorption kinetics in porous grains is analyzed. Model equations for sorption kinetics with complete derivatives are considered with regard for sorption heat release. The accuracy of different model kinetic equations is estimated. A method is proposed to determine heat transfer coefficients in porous grains. Experimental relationships are obtained describing the dependence of the kinetic curve and mean temperature distribution on time for porous grains of silica gel when benzene vapors are used as sorbate. Experimental relationships are compared with those calculated on an electronic digital computer, their agreement being satisfactory. This proves the application of complete-derivative model equations to be reasonable for practical calculations of nonisothermal sorption kinetics.     

Influence of saline media on the fluorescence emission of Bacillus spores

Single-particle levitation in conjunction with 264.3-nm laser excitation is used to measure the fluorescence emission of individual particles of Bacillus globigii spores. With precise humidity control, the fluorescence emission of wetted and desiccated Bacillus spore particles is measured from 300 to 450 nm. Comparison of spectra for Bacillus spores suspended in a standard buffer aqueous solution and for a desiccated 10-mum-diameter aggregate Bacillus spore particle shows that the spectra is virtually indistinguishable. However, at 85% relative humidity, corresponding to a 4.5M sodium chloride solution, the spore spectra redshifts by approximately 25 nm. It is postulated that the spectra redshifting is a result of specific interactions between the tyrosine fluorophore of the Bacillus spore and the phosphate moieties in the buffer solution.     

Biological nitrogen and phenol removal from saline industrial wastewater by submerged fixed-film reactor

In this study a biological nitrogen removal process using a submerged fixed-film reactor was applied to treat industrial wastewater with phenol (1g/l), a high nitrogen concentration (0.4 g N/l) and high salinity (30 g/l). The process consisted of a pre-denitrification system with a down-flow-up-flow biofilter (two columns, each with an effective volume of 21 l) packed with clayey schists from recycled construction material. The efficiency of the system for reducing COD, phenol concentration and total nitrogen was tested under different running conditions such as influent flow (10, 12 and 15 l/d), air loading (6.8 and 13.6m(3)/m(2)h) and effluent recirculation (300%, 400%, and 600%). The system demonstrated a high capacity for reducing COD concentration (95.75+/-0.72%), independently of running conditions. The aerobic column eliminated most of the phenol in the influent. Nitrogen removal took place mainly in the anoxic column, and was conditioned by the air loading in the aerated column, owing to the dependence of nitrification on the supply of oxygen. However, this process was not able to achieve a nitrogen oxidation superior to 63%, in spite of a sufficient supply of oxygen and the diluting effect of high recirculation (600%) on the phenol concentration in the influent. In spite of the limitations observed in the process of nitrification, results for the removal of total nitrogen were as high as 83%, owing to a combination of different processes for nitrogen removal.     

Some features of the kinetics of high-speed penetration in brittle media

The kinetics of the high-speed penetration of deformable rods into ceramics has been investigated. It is established that penetration takes place by a two-stage process. In the first stage the penetration velocity increases with increasing damage to the ceramic. The second stage corresponds to quasisteady penetration into a medium devoid of strength. It is shown that the first stage determines the high level of resistance of ceramics to high-intensity impact loading. Pis’ma Zh. Tekh. Fiz. 23, 68–73 (February 12, 1997)     

Role of hydroboron intermediates in the mechanism of chemical vapor generation in strongly acidic media

Unknown and controversial aspects related to the mechanisms of hydrolysis of borane complexes and to the mechanisms of chemical vapor generation for trace element determination in strongly acidic media (0.01-10 M HCl) have been investigated and clarified. The overall hydrolysis rates of borane complexes (BH(4)(-), H(3)N-BH(3)) in the acidity range of 0.2-10 M HCl were several orders of magnitude lower than those predicted by kinetics laws and obtained in the pH range of 3.8-14. The decomposition of the borane complexes takes place stepwise and proceeds through the formation of hydroboron intermediates, L(x)()BH(4)(-)(x)()(n)() (x = 1, 2, 3), where L could be one or more species among the donor groups H(2)O, NH(3), OH(-), and Cl(-) and n is the charge of the hydroboron species (n = 0, +1, -1, depending on L). Some intermediates present surprisingly long lifetimes at elevated acidities and play a key role in determining both the overall hydrolysis rates of borane complexes and the reactivity of Hg(II), As(III), Sb(III), Bi(III), Se(IV), Te(IV), and Sn(IV) in chemical vapor generation for trace element determination. Atomic absorption experiments demonstrated that almost all trihydroboron species (LBH(3)(n)()), dihydroboron species (L(2)BH(2)(n)()), and monohydroboron species (L(3)BH(n)()) play an active role in the generation of elemental mercury and stibine. Some of these intermediates are inactive or play a marginal role in the generation of arsine, bismuthine, and hydrogen selenide. Hydrogen telluride is preferentially formed by those hydroboron species, which are stable in strongly acidic conditions, while the same species are unreactive in the generation of stannane. The collected experimental evidence is in agreement with the general reactivity of the elements in chemical vapor generation techniques and, together with other literature data, definitely rule out the hypothesis of "nascent hydrogen" as a possible mechanism of chemical vapor generation by borane complex derivatization.     

The influence of TiO2 and aeration on the kinetics of electrochemical oxidation of phenol in packed bed reactor

The electrochemical oxidation of phenolic wastewater in a lab-scale reactor, packed into granular activated carbon (GAC) with Ti/SnO2 anodes and stainless steel cathodes, was interpreted in this study. GAC saturated rapidly if it was only used as sorbent, but application of suitable electric energy for the system simultaneously could recover the adsorption ability of GAC and maintain the continuous running effectively. The titanium dioxide (TiO2) as catalyst and airflow were also applied to the electrochemical reactor to examine the enhancement for phenol oxidation process. Results revealed that the electrochemical degradation of phenol could be reasonably described by first-order kinetics. In addition, it was illustrated that acid region, increased voltage, more dosage of TiO2 and higher aeration intensity were all beneficial parameters for phenol oxidation rates. By inspecting the relationship between the rate constants (k) and influencing factors, respectively, an overall kinetic model for phenol oxidation was proposed. The kinetics obtained from the experiments under corresponding electrochemical conditions could provide an accurate estimation of phenol concentration effluent and better design of the packed bed reactor.     

Decolorization of malachite green, decolorization kinetics and stoichiometry of ozone-malachite green and removal of antibacterial activity with ozonation processes

This study aimed to identify degradation intermediates and to investigate the stoichiometry of decolorization and degradation, decolorization kinetics, and removal of antibacterial activity of malachite green (MG) using ozonization processes. The decolorization of MG was optimal at an acidic pH value of 3 based on molecular ozone attack on MG molecules. The stoichiometric ratio of decolorization between ozone and MG was calculated to be 7.0 with a regression coefficient of 0.995, whereas the ratio for degradation was calculated as 13.1 with a regression coefficient of 0.998. With MG concentrations in the range of 0.30-1.82 mM, the concentration of decolorized MG increased with higher initial concentrations of MG, whereas the ozonolytic decolorization rates of MG, decreased with increasing initial concentration. The pseudo-first-order degradation rate constants (k') decreased with the initial concentration and ranged from 0.769 to 0.223 min(-1). Twelve different intermediates were produced during the ozonation of MG with ozonation times between 5 min and 30 min and were identified by GC-MS. Although 86% of MG in the reaction mixture was removed by ozonation after 10 min, the decrease of antibacterial activity was very low (10%) for Bacillus subtilis and Staphylococcus epidermidis because the degradation intermediates, phenol and benzoic acid, also have antibacterial activity. The antibacterial activity of both MG and its intermediates were removed successfully with ozonation times above 26 min.     

Grinding kinetics of red grape seed residue in stirred media mill

The main objective of the present paper was to experimentally investigate the grinding kinetics of red grape seed which is the by-product of winery and juice industry. Stirred media mill was used as a high energy density mill to improve the raw grape seed fineness, i.e. mean particle size approx. 10 µm using various rotor circumferential velocities under dry condition. The effect of stress intensity and stress number on the particle size distribution of ground grape seed was investigated. Optimum conditions (rotor velocity and residence time) were determined, mean particle size close to 10 µm and 5000 cm²/g geometric specific surface area were reached within the studied variables. Additionally, concerning the material structure, FTIR measurements of the ground grape seed samples were carried out which demonstrated that no structural changes were detected. Furthermore, the specific grinding work was measured for each test, in this way energy utilization, efficiency was determined.     

Adsorption of phenol and 4-nitrophenol on granular activated carbon in basal salt medium: equilibrium and kinetics

Batch studies were carried out for studying the adsorption behaviour of phenol and 4-nitrophenol on granular activated carbon from a basal salt medium (BSM) at pH approximately 7.1 and temperature approximately 30 degrees C. The literature review was done in order to review the information for comparison purposes on equilibrium models of phenol and 4-nitrophenol adsorption on activated carbon. The units for measurements reported in these models were found to be diverse, thus making the comparison difficult. These units have been converted into similar units for easy reference. In all, six models of Freundlich, Langmuir, Redlich-Peterson, Radke-Prausnitz, Toth and Fritz-Schlunder as reported in the literature have been fitted to the data of phenol/activated carbon and 4-nitrophenol/activated carbon systems of the present studies using nonlinear regression technique. Based on maximum deviations and correlation coefficients, Langmuir gave the poorest fit for both compounds; Redlich-Peterson, Radke-Prausnitz, and four parameter model of Fritz-Schlunder could represent the data with similar accuracy, i.e. with R2-value of 0.98 and maximum deviation approximately 12%. However, for phenol, two parameter model of Freundlich may be recommended because of ease in its parameter estimation and better accuracy. 4-Nitrophenol was found to be more adsorbed than phenol, which is consistent with the result found in literature. The kinetics of the adsorption was found to be intra-particle diffusion controlled with diffusion coefficient values of the order of 10(-13)m2/s. Three distinct phases of kinetics--rapid, medium, and slow--have been observed in this study.     

Kinetics of the ozonation of muconic acid in water

The removal of muconic acid (specifically trans-trans-butanedioc acid) with ozone from water has been studied for kinetics purposes. Concentrations of muconic acid of 4.4x10(-4)M are completely removed with ozone in less than 14 and 9 min at pH 3 and 7, respectively, and 3x10(-4)M of ozone in the gas. The positive influence of pH was due to the more reactive muconic acid dissociated form with ozone. The process can be described as a second order irreversible gas-liquid reaction developing in the moderate kinetic regime of absorption. At the experimental conditions investigated no free radical reactions are present and muconic acid is entirely oxidized by molecular ozone. Rate constants of the direct reaction between muconic acid and ozone were found to be 1.6x10(4) and 1.4x10(5)M(-1)s(1) at 20 degrees C, pH 3 and 7, respectively, according to film theory.