Indirect Electrochemical Oxidation of Phenol in the Presence of Chloride for Wastewater Treatment

Electrochemical oxidation of phenol using a Ti/TiO₂‐RuO₂‐IrO₂ anode in the presence of chloride as the supporting electrolyte was investigated. The experiments were performed in an undivided batch reactor. Preliminary investigations showed that only a small fraction of phenol was oxidized by direct electrolysis, while complete degradation of phenol was achieved by indirect electrochemical oxidation using chloride as a supporting electrolyte. The effect of operating parameters such as initial pH, supporting electrolyte concentration, phenol concentration, and charge input was studied using Box‐Behnken second order composite experimental design. The effect of current density on COD removal was studied separately. TOC removal and AOX formation were studied for selected conditions. It was found that the formation of chlorinated organic compounds was pronounced at the beginning of electrolysis, but it was reduced to lower levels by extended electrolysis.     

Performance evaluation of a continuous flow Photo-Impinging Streams Cyclone Reactor for phenol degradation

In this study, an impinging streams cyclone reactor has been utilized as a novel apparatus in photocatalytic degradation of phenol. Degussa P25 TiO₂ nano particles have been applied as the photocatalyst under UV radiation. The operating parameters including catalyst loading, pH, initial phenol concentration and light Intensity have been found to affect the efficiency of the photocatalytic degradation process within this photoreactor. Photocatalytic degradation of phenol has been also investigated in a continuous flow impinging streams system. The results have shown a higher efficiency and an increased performance capability of the present reactor in comparison with the conventional processes.     

Toxicity identification of effluent from a semiconductor lead frame manufacturing factory

The acute toxicity of lead frame effluent to Daphnia magna was found to be 22.62 TU, which far exceeded the toxicity discharge limit in Korea (<1 TU). TIE phases I and II result suggest that the mixture of Ag, Cu and CN were likely responsible for the observed toxicity, and this was confirmed by mass balance approach (TIE phase III). In addition, the Visual MINTEQ simulation suggested the presence of [Ag(CN)₂]⁻ and [Cu(CN)₃]²⁻ complexes in the effluent. Therefore, TIE procedures with chemical speciation modeling were effective for identifying the cause of acute toxicity in industrial effluents.     

Remediation of Kraft Effluent by Ozonation: Effect of Applied Ozone Concentration and Initial pH

In this study, the impact of ozone concentration (14 and 7mg/L^?1 applied for 120min) and pH (10 and 12) on color removal, and reduction of dissolved organic matter (DOC) and total phenol of Kraft E₁ effluent was investigated. The degradation kinetics for the all parameters at pH 12 were slower than of those at pH 10. The degradation at pH 10 ceased after approximately 120min, while for the ozonation at pH 12, ozone was still being consumed even after 5h of treatment. When the ozone dose was increased, the removal efficiency increased; however, the DOC removal efficiency continued limited.     

Photocatalyzed Degradation of Phenol, 2,4-Dichlorophenol,Phenoxyacetic Acid and 2,4-Dichlorophenoxyacetic Acid over SupportedTiO2 in a Flow System

The photodegradation of phenol, 2,4-dichlorophenol, phenoxyacetic acid and 2,4-dichlorophenoxyacetic acid using TiO₂ as photocatalyst is investigated. The photodegradations of these compounds have been conducted in a continuous mode by means of a flow system, in which TiO₂ remains fixed onto glass pearls. The use of this system gives high yields of degradation for the chemicals tested, except for 2,4-dichlorophenol for which a slow dechlorination process is observed. The rate of photodegradation depends on the pH of the solution, the point of zero charge of TiO₂ and the pK_a of the chemicals being the key parameters. The main aromatic intermediates detected have been hydroquinone,paraquinone and hydrohydroquinone during phenol degradation; phenol and hydroquinone during phenoxyacetic acid degradation; chlorohydroquinone and chlorophenol during 2,4-dichlorophenol degradation; and dichlorophenol during 2,4-dichlorophenoxyacetic acid degradation. Finally, some long term irradiations with phenol as model compound have been performed, showing high degrees of photodegradation. It has been observed that only a periodic evacuation of the effluent out of the reactor is needed to sustain high percentages of photodegradation.     

Performance and Economic Assessment of the Treatment of Phenol with TiO2 Photocatalysis,Photo‐Fenton,Biological Aerated Filter,and Wetland Reactors

The performance and economic cost of the removal of phenol with TiO₂ photocatalysis, photo‐Fenton reactions, biological aerated filter (BAF), and constructed wetland (CW) reactors has been studied. The BAF achieved complete removal with a maximum phenol concentration of 200 mg·L^?1. The BAF‐CW combination provided a phenol‐free effluent with a maximum phenol concentration of 650 mg·L^?1. In both cases, a complete detoxification of the treated water was achieved at the concentrations studied. The efficiency of TiO₂ photocatalysis was limited to concentrations below 50 mg L^?1 to minimize removal reduction and toxicity of the intermediates. Photo‐Fenton was more efficient, but also more expensive because of the high cost of H₂O₂. The photo‐Fenton‐BAF combination is proposed to be the most suitable one.     

The Advanced Oxidation Process of Phenol Solution by O3/H2O2 in a Rotating Packed Bed

This article presents experimental investigation on the oxidative treatment of phenol in water by O₃/H₂O₂ in a rotating packed bed (RPB). It was found that the phenol degradation ratio increased with increasing rotation speed, initial pH value of phenol solution, and temperature. The degradation ratio of phenol had a peak value with increasing H₂O₂ concentration. The optimum operating conditions in this study were determined as an H₂O₂ concentration of 6.5 mM and a rotation speed of 1200 rpm. Phenol degradation ratio reached 100% at an initial phenol concentration of 40 mg/L in the O₃/H₂O₂ process.     

Modeling of Fenton Reaction for the Oxidation of Phenol in Water

Phenol is an organic pollutant found in various types of industrial wastewater. Due to its bactericidal properties, it is difficult to eliminate it by classic treatment methods. In this work, the degradation of this compound by Fenton reaction at mild temperature and pressure conditions is studied. An experimental design was applied in order to quantify the influence of operating parameters on the efficiency of this method. The field of study was defined between 20 and 50^{^}C for the temperature, 1 and 4 g L^-1 for the phenol concentration, 10 and 28 for the H₂O₂ to phenol molar ratio, and 0.02 to 0.08 for the Fe(II) to phenol concentration ratio. It was shown that the temperature and the amount of catalyst have a strong influence. A model giving the decrease of COD was established. The COD decrease was between 40% and 72% and phenol had totally disappeared.     

Photoelectrocatalytic degradation of phenol using a TiO<Subscript>2</Subscript>/Ni thin-film electrode

As a new type of photoelectrode, TiO₂/Ni thin-film electrode was prepared by dip-coating technique. The structural and surface morphology of electrode was examined by X-ray diffraction (XRD) and scanning electron microscope (SEM). Effects of initial phenol concentration, pH value, number of film layers, voltage of electrical bias applied, variation of inorganic salt type and types of dissolved gas on the photoelectrocatalytic (PEC) degradation of phenol using ultraviolet (UV) illuminated TiO₂/Ni thin-film electrode were investigated. The mechanism of PEC degradation of phenol was also studied by analyzing reaction intermediates.     

转盘式反应器光催化氧化含酚废水的试验研究

设计的新型转盘式光反应器采用同轴多层转盘作为TiO2膜的载体,很大程度上扩大了光与催化剂的接触面积,对光源系统进行优化布置,使光均匀分布在各转盘叶片之间,不仅可以提高光辐射强度还具有良好的传质性能.利用该反应器光催化氧化苯酚废水,考察了反应器各参数对苯酚降解率的影响,试验结果表明该反应器对低浓度苯酚废水具有良好的降解效果,出水水质可以达到国家一级排放标准.同时从工业放大的角度考虑,多叶转盘式光反应器的结构和降解能力决定了它具有潜在的优势.     

溶剂萃取法处理苯酚稀溶液及其废水的研究

为探索工业含酚废水处理的适宜萃取剂,选用具有物理萃取和络合萃取作用的两类萃取剂正辛醇、甲基异丁基甲酮(MIBK)和磷酸三丁酯(TBP)(以煤油为稀释剂)进行了苯酚稀溶液萃取性能的实验研究。测定了不同溶液pH值、初始苯酚浓度和TBP浓度条件下的萃取平衡数据,分析了各萃取剂萃取平衡的规律及机理。结果表明,虽然各萃取剂的萃取机理不同,但在酸性和中性范围内都可获得较大的萃取平衡分配系数,所以,这三种萃取剂的适宜pH值操作条件为酸性和中性,且在稀溶液的范围内溶剂的萃取能力为TBP > MIBK >正辛醇,而在极稀的苯酚浓度条件下(<20mgL-1),则为正辛醇> TBP > MIBK。同时,正辛醇、TBP处理工业含酚废水的错流萃取实验表明,若考虑通过单一的萃取方法使得废水中苯酚的浓度达到国家排放标准(0.5mgL-1),正辛醇为适宜的萃取剂。     

An optimization study on microwave irradiated decomposition of phenol in the presence of H2O2

BACKGROUND Removal of phenol from industrial waste waters involves basic techniques namely extraction, biodegradation, photocatalytic degradation, etc. Among the available processes, the oxidation of phenols using H₂O₂ is a suitable alternative because of low cost and high oxidizing power. The application of an oxidation process for the decomposition of stable organic compounds in waste water leads to the total degradation of the compounds rather than transferring from one form to another. Since oxidation using Fenton's reagent is more dependent on pH, in this present work it was proposed to use H₂O₂ coupled with microwave irradiation. The effects of initial phenol concentration, microwave power and the irradiation time on the amount of decomposition were studied. RESULTS: In the present work experiments were conducted to estimate the percentage degradation of phenol for different initial concentrations of phenol (100, 200, 300, 400 and 500 mg L^?1), microwave power input (180, 360, 540, 720 and 900 W) for different irradiation times. The kinetics of the degradation process were examined through experimental data and the decomposition rate follows first‐order kinetics. Response surface methodology (RSM) was employed to optimize the design parameters for the present process. The interaction effect between the variables and the effect of interaction on to the responses (percentage decomposition of phenol) of the process was analysed and discussed in detail. The optimum values for the design parameters of the process were evaluated (initial phenol concentration 300 mg L^?1, microwave power output 668 W, and microwave irradiation time 60 s, giving phenol degradation 82.39%) through RSM by differential approximation, and were confirmed by experiment. CONCLUSION: The decomposition of phenol was carried out using H₂O₂ coupled with microwave irradiation for different initial phenol concentrations, microwave power input and irradiation times. The phenol degradation process follows first‐order kinetics. Optimization of the process was carried out through RSM by forming a design matrix using CCD. The optimized conditions were validated using experiments. The information is of value for the scale up of the oxidation process for the removal of phenol from wastewater. Copyright © 2008 Society of Chemical Industry     

pH、碱度和苯酚对低浓度氨氮废水处理工艺的影响

低浓度氨氮废水的处理一直是近年来的研究热点和难点，各种处理工艺的运行并不稳定，出水氨氮浓度经常超标。本文对pH、碱度和有毒物质苯酚等影响低浓度氨氮废水处理工艺运行的主要因素进行了研究。结果表明：低浓度氨氮废水处理的最优pH在9左右．偏碱性的环境更有利于低浓度氨氮废水的处理；Alk／N=38．39（此时pH=8．7）时，低浓度氨氮硝化速率接近最大值，充足的碱度有利于低浓度氨氮的彻底硝化：苯酚对硝化污泥的抑制为非竞争性抑制；达到相同的氨氮出水浓度，苯酚抑制条件下泥龄大于无抑制情况，且抑制程度越高，所需泥龄越长。低浓度氨氮硝化污泥一旦受到苯酚的抑制，很难通过控制泥龄的途径得到解决。     

Designing and operating a pilot plant for purification of industrial wastewater from toxic organic compounds by utilizing solar energy

The aim of the present project was to design and operate a solar reactor system and to analyze its performance for the removal of different types of toxic organic pollutants (e.g., synthetic methyl violet dye and phenol) from water with titanium dioxide as the photocatalyst. Various operating parameters were studied to investigate the behavior of the designed reactor like initial substrate concentration, loading of catalyst, pH of solution, and H₂O₂ concentration. The operating parameters were optimized to give higher efficiency to the reactor performance. Results showed that a photocatalysis system, operating at optimum conditions, offered within one hour of operation degradation up to 95.27% for synthetic dye, while a conversion of 99.95% was obtained in three hours. With phenol, degradation was up to 80.0% and 98.0%, respectively. The removal of TOC for the two toxic materials was also at high levels. This confirmed the feasibility of the designed solar system. The kinetics of dye degradation was first order with respect to dye concentration and could be well described by Langmuir-Hinshelwood model. A preliminary design of a solar photocatalysis system as an alternative treatment method for wastewater effluents from an Iraqi textile mill was introduced.     

利用生物反应器处理含酚废水

以从农药厂土壤中分离得到的苯酚降解菌为菌种,采用有效容积为6L的自制生物反应器对模拟含酚废水进行生物降解实验,考察在不同曝气量、pH值和苯酚浓度下苯酚降解菌降解苯酚性能的变化。结果表明,在温度为17 ℃、接种量为7%、曝气量为30 L/h、pH值为6～8的条件下,24 h内可使浓度为700 mg/L的苯酚降解率达到99%以上。在苯酚浓度为200～700 mg/L范围内其平均降酚速率随苯酚浓度的增加而增大,最大达29.2 mg/(L·h)。该菌对pH值、初始苯酚浓度的变化不敏感,能适应一定的冲击负荷。     

Aerobic Degradation of Trichloroethylene by Co-Metabolism Using Phenol and Gasoline as Growth Substrates

Trichloroethylene (TCE) is a common groundwater contaminant of toxic and carcinogenic concern. Aerobic co-metabolic processes are the predominant pathways for TCE complete degradation. In this study, Pseudomonas fluorescens was studied as the active microorganism to degrade TCE under aerobic condition by co-metabolic degradation using phenol and gasoline as growth substrates. Operating conditions influencing TCE degradation efficiency were optimized. TCE co-metabolic degradation rate reached the maximum of 80% under the optimized conditions of degradation time of 3 days, initial OD₆₀₀ of microorganism culture of 0.14 (1.26 × 10⁷ cell/mL), initial phenol concentration of 100 mg/L, initial TCE concentration of 0.1 mg/L, pH of 6.0, and salinity of 0.1%. The modified transformation capacity and transformation yield were 20 μg (TCE)/mg (biomass) and 5.1 μg (TCE)/mg (phenol), respectively. Addition of nutrient broth promoted TCE degradation with phenol as growth substrate. It was revealed that catechol 1,2-dioxygenase played an important role in TCE co-metabolism. The dechlorination of TCE was complete, and less chlorinated products were not detected at the end of the experiment. TCE could also be co-metabolized in the presence of gasoline; however, the degradation rate was not high (28%). When phenol was introduced into the system of TCE and gasoline, TCE and gasoline could be removed at substantial rates (up to 59% and 69%, respectively). This study provides a promising approach for the removal of combined pollution of TCE and gasoline.     

A batch LED reactor for the photocatalytic degradation of phenol

Photocatalytic degradation of phenol by titanium dioxide illuminated by one light emitting diode (LED) in a batch photocatalytic reactor is reported in this paper. The effect of catalyst loading, catalyst type, phenol–hydrogen peroxide ratio, pH, initial phenol concentration and irradiance by applying pulse width modulation (PWM) was studied. The effect of the beam width on photocatalytic degradation of phenol is also included in this paper as is the use of different type of reflectors outside the reactor. With both an LED beam width of 120° and optimal chemical conditions of 10 ppm phenol concentration with a hydrogen peroxide–phenol molar ratio of 100 and pH of 4.8, a degradation rate of 42% was achieved after 4 h. Decreasing the beam width to 40° raised degradation to 87%.In order to study the irradiance distribution and its effect on the reactor performance, experiments were conducted incorporating various catalysts loading, reactor heights and beam widths. The irradiance was measured for different amount of catalyst loading ranging from 0.17 to 1.8 g L⁻¹at different reactor heights. The results are compared with optimal catalyst loading measurement to assess the correlation between phenol degradation and irradiance distribution. The UV LED in combination with titanium dioxide is appropriate for water treatment to degrade organic pollutants at low concentration.     

Ozonation of Phenol-Containing Wastewater Using O3/Ca(OH)2 System in a Micro Bubble Gas-Liquid Reactor

The degradation of phenol in aqueous solution was investigated in an integrated process consisting of O₃/Ca(OH)₂ system and a newly developed micro bubble gas-liquid reactor. The effects of operating parameters such as Ca(OH)₂ dosage, reactor pressure, liquid phase temperature, initial phenol concentration and inlet ozone concentration on degradation and mineralization (TOC removal) were studied in order to know the ozonation performance of this new integrated process. It is demonstrated that the degradation and TOC removal efficiency increased with increasing inlet ozone concentration and increasing Ca(OH)₂ dosage before 2 g/L, as well as decreasing initial phenol concentration. The optimum Ca(OH)₂ dosage should exceed Ca(OH)₂ solubility in liquid phase. The reactor pressure and liquid phase temperature have little effects on the removal and TOC removal efficiency. When Ca(OH)₂ dosage exceeded 3 g/L, the degradation and TOC removal of phenol almost reached 100% at 30 and 55 min, respectively. The intensification mechanism of Ca(OH)₂ assisted ozonation was explored through analysis of the precipitated substances. The mechanism for Ca(OH)₂ intensified mineralization of phenol solution is the simultaneous removal of CO₃^2- ions, as hydroxyl radical scavengers, due to the presence of Ca²⁺ ions. Results indicated that the proposed new integrated process is a highly efficient ozonation process for persistent organic wastewater treatment.     

Degradation of Aqueous Phenol and Chlorinated Phenols by Ozone

The degradation of phenol and its chlorinated derivatives with ozone is studied. The studied compounds are phenol (Ph), 4-chlorophenol (4-CPh) and 2,4-dichlorophenol (2,4-DCPh). The kinetic performances of each phenolic compound and their model mixture are examined. The pH influence on the decomposition dynamics for different phenolic compounds in the range 2–12 is investigated. The increase of the decomposition rate under increasing pH was observed. In the pH range studied, phenol and chlorophenols ozonation proceeds rapidly. The UV absorbency is used for the preliminary control of the degree of decomposition. The HPLC analysis is used to identify intermediates and final products formed during ozonation. It is shown that the basic intermediates are muconic and fumaric acids, malonic and maleic acids, catechol and hydroquinone. The final products are oxalic acid and formic acid. In the case of alkaline media, the principal final product is oxalic acid. Furthermore, intermediates and final decomposition products obtained at different pH are compared. According to the results obtained, the possible mechanism of ozonation by the reaction of hydroxylation and dechloration in the early stage is proposed. The BOD₅/COD ratio is used as a biodegradability measure for the comparison of biodegradability of initial compounds and final products composition.     

微波强化臭氧氧化降解苯酚水溶液

The degradation of phenol in aqueous solution with the combination of microwave and ozone（MW/O₃）was studied with laboratory-scale experiments.Effects of ozone dose,pH value,initial phenol concentration and reaction temperature on the reaction kinetics were investigated.In all cases,the degradation of phenol follows a pseudo-first-order kinetics relation.MW/O₃ combined technology is favorable for enhancing the removal efficiency of phenol,with the enhancement factor of the first-order kinetics constant being around 3.6.Experimental results showed that the synergetic effect of MW/O3 combined technology was obvious and up to 99 % of phenol was removed after 30 min reaction with initial phenol concentration of 100 mg·L^-1,ozone dose of 1.1 mg·min^-1,pH value of 9—11,and reaction temperature of 25℃.