RESUMEN
The removal of dimethyl phthalate (DMP), which is a pollutant of concern in water environments, was carried out by catalytic ozonation with TiO(2)/Al(2)O(3) catalysts. The heterogeneous catalytic ozonation was an ozonation process combined with the catalytic and adsorptive properties of the TiO(2)/Al(2)O(3) catalysts to significantly accelerate the mineralization efficiency. Semi-batch ozonation was performed under various experimental conditions including the fed ozone concentration, catalyst type, catalyst dosage, and ultraviolet radiation on the degradation of DMP. The complete removal of DMP was efficiently achieved by both sole and catalytic ozonation; meanwhile, the presence of the catalysts slightly accelerated the elimination rate of DMP. On the other hand, the mineralization efficiency, in terms of total organic carbon (TOC) removal, was substantially enhanced by employing the TiO(2)/Al(2)O(3) catalyst. The mineralization efficiency using the TiO(2)/Al(2)O(3) catalyst was the highest, followed in decreasing order by the Al(2)O(3) catalyst, the TiO(2) catalyst, and sole ozonation. In addition, the use of the TiO(2)/Al(2)O(3) catalyst would increase the utilization efficiency of the fed ozone, especially in the late ozonation period. Furthermore, the decrease in the catalytic activity of the TiO(2)/Al(2)O(3) catalyst after multi-run experiments can be mostly recovered by an incineration process at a high temperature.
Asunto(s)
Óxido de Aluminio/química , Ozono/química , Ácidos Ftálicos/química , Titanio/química , Adsorción , Carbono/análisis , Catálisis , Técnicas de Química Analítica , Diseño de Equipo , Incineración , Temperatura , Factores de Tiempo , Rayos Ultravioleta , Contaminantes Químicos del Agua/análisis , Purificación del Agua/métodosRESUMEN
The continuous-flow transesterification of soybean oil with methanol using a rotating packed bed (RPB) for the production of fatty acid methyl esters (biodiesel) is presented herein. The RPB, which provides high centrifugal force and has an adjustable rotational speed, is employed as a novel transesterification reactor. In this study, biodiesel is synthesized via the methanolysis of soybean oil using potassium hydroxide as the catalyst. The following variables were investigated for their effects on transesterification efficiency: the methanol-oil molar ratio, the estimated hydraulic retention time, the rotational speed of the packed-bed rotator, the reaction temperature, and the catalyst dosage. The yield of the fatty acid methyl esters (Y(FAME)) in the RPB system depends significantly on the experimental conditions, which influence the residence time distribution, the transesterification reaction rate, and the micromixing intensity. Due to its excellent micromixing characteristics, the RPB system shows satisfactory transesterification efficiency. The values of Y(FAME), productivity of FAMEs (P(FAME)), and P(FAME) per unit reactor volume (P(FAME)/V(R)) in the RPB are used to evaluate the performance for biodiesel production and allow for further comparison with other continuous transesterification reactors. Consequently, a RPB is considered a practical transesterification reactor with high transesterification efficiency.
Asunto(s)
Biocombustibles , Catálisis , Esterificación , Hidróxidos/química , Compuestos de Potasio/química , Aceite de Soja/químicaRESUMEN
This study investigates the photocatalytic degradation of dimethyl phthalate (DMP) with both the titanium dioxide-coated magnetic poly(methyl methacrylate) (TiO2/mPMMA) and platinum-doped TiO2/mPMMA (Pt-TiO2/mPMMA) microspheres. The TiO2/mPMMA and Pt-TiO2/mPMMA microspheres are employed as novel photocatalysts that offer high photocatalytic activity, magnetic separability and good durability. The photocatalytic experiments of DMP under various conditions are conducted to examine the effects of the initial DMP concentration, photocatalyst dosage, UV radiation intensity and Pt doping content on the degradation of DMP. In addition, the correlations of the photocatalytic kinetics and quantum yield for DMP removal are proposed associated with the system parameters. According to the experimental results, there exists a distinct relationship between the reduction percentages of total organic carbons and DMP. Furthermore, the photodegradation mechanism of DMP in the photocatalytic process is established based on the identification of the intermediates. Moreover, the good repeatability of the photocatalytic performance with the use of the Pt-TiO2/mPMMA microspheres has also been demonstrated in the multi-run experiments. Therefore the Pt-TiO2/mPMMA microspheres are considered as a practical and promising photocatalyst in a suspension reaction system and they can be effectively recovered after use. This study provides useful information about the applications of the TiO2/mPMMA and Pt-TiO2/mPMMA microspheres for the photodegradation of DMP.
Asunto(s)
Microesferas , Fotoquímica/métodos , Ácidos Ftálicos/química , Platino (Metal)/química , Polimetil Metacrilato/química , Purificación del Agua/métodos , Catálisis , Técnicas de Química Analítica , Cinética , Magnetismo , Modelos Químicos , Titanio/química , Rayos Ultravioleta , Contaminantes Químicos del Agua/análisisRESUMEN
This study investigates the oxidation of local scrubber wastewater (LSW) from semiconductor manufacture by using ozonation, catalytic ozonation (ozone/Al(2)O(3) and ozone/TiO(2)-Al(2)O(3)), and photo-catalytic ozonation (UV/TiO(2)-Al(2)O(3), ozone/UV and ozone/UV/TiO(2)-Al(2)O(3)). The results show that catalyst Al(2)O(3) and TiO(2)-Al(2)O(3) promotes the TOC removal under the condition of neutral or alkaline buffer solution during catalytic ozonation of LSW. The Al(2)O(3) induces highest promotion in TOC removal efficiency, which is higher than ozone alone by 26% TOC removal under alkaline buffer solution. However, TiO(2)-Al(2)O(3) and Al(2)O(3) cannot display the promotion in TOC removal under acidic condition. In addition, a pre-treatment of anion ion-exchange is employed and the result indicates that decreasing the anion ions concentration before AOPs can imply higher TOC removal during AOPs of LSW. In this study, ozone/UV under raw LSW acidic condition and ozone/Al(2)O(3) under alkaline buffer solution present 95% and 88% TOC removal rate respectively and show the higher TOC removal efficiency than other AOPs. Therefore, these two kinds of AOP can serve as the very viable AOP methods in the LSW reclamation for semiconductor.
Asunto(s)
Ozono/química , Fotoquímica/métodos , Semiconductores , Eliminación de Residuos Líquidos/métodos , Purificación del Agua/métodos , Óxido de Aluminio/química , Catálisis , Concentración de Iones de Hidrógeno , Oxidación-Reducción , Titanio/químicaRESUMEN
This study investigates the enhanced ozonation of dimethyl phthalate (DMP), which is a pollutant of concern in water environments, with high silica zeolites and ultraviolet (UV) radiation. Semibatch ozonation experiments are performed under various reaction conditions to examine the effects of inlet gas ozone concentration, high silica zeolite dosage, and UV radiation intensity on the decomposition of DMP. The complete removal of DMP can be efficiently achieved via both O(3) and O(3)/UV treatments. Note that the presence of high silica zeolites accelerates the decomposition rate of DMP in the O(3) process. On the other hand, the removal efficiencies of both chemical oxygen demand (COD) and total organic carbons (TOC) are significantly enhanced by employing the ozonation combined with UV radiation. The O(3)/UV process is also advantageous for the utilization efficiency of fed ozone especially in the late ozonation period. Furthermore, the correlation between the COD removal percentage (%) and the mole ratio of ozone consumed to the DMP treated (mol mol(-1)) is obtained. The clear-cut removal relationship of the TOC with COD during the ozonation of DMP has also been presented. Consequently, the results evaluate the flexibility of ozonation system associated with high silica zeolites and UV radiation for the removal of DMP and provide the useful information in engineering application.
Asunto(s)
Ozono/química , Ácidos Ftálicos/química , Contaminantes Químicos del Agua/aislamiento & purificación , Purificación del Agua/métodos , Diseño de Equipo , Conformación Molecular , Oxidación-Reducción , Dióxido de Silicio/química , Soluciones , Rayos Ultravioleta , Contaminantes Químicos del Agua/química , Zeolitas/químicaRESUMEN
This study investigated the oxidation of methyl methacrylate (MMA) by sole ozonation and ozone/UV treatments. The semi-batch ozonation experiments were proceeded under different reaction conditions to study the effects of ozone dosage and UV radiation on the oxidation of MMA. The experimental results indicated that both the oxidation of MMA by the sole ozonation and O3/UV processes can completely decompose MMA to form the following intermediates within 30 min reaction time. To increase the applied ozone dosage can significantly raise the removal efficiency of MMA. However, the mineralization of MMA via the direct oxidation reaction of molecular ozone was slow, while introducing the UV radiation can promote the mineralization rate of MMA. In addition, the pH value of the oxidized solution in the O3/UV treatment decreased lower than that in the sole ozonation treatment of about 1 unit. The possible scheme of the decomposition pathway of MMA under the ozonation process is proposed in this study. Formic acid and acetic acid were found to be the main ozonated intermediates.
Asunto(s)
Residuos Industriales/prevención & control , Metilmetacrilato/química , Metilmetacrilato/efectos de la radiación , Semiconductores , Ácido Acético , Formiatos , Oxidación-Reducción , Ozono , Fotólisis , Rayos UltravioletaRESUMEN
This study investigates the ozonation of Reactive Red 120 and Acid Red 299 dyes in the synthesized solution and textile wastewater by using a rotating packed bed. The decomposition rate of Reactive Red 120 and Acid Red 299 dyes via ozonation can be described by the pseudo-first-order kinetics. Ozonation of Reactive Red 120 exhibited the higher mineralization rate compared with that of Acid Red 299. The biodegradability of the two dyes could be significantly promoted during the ozonation. The BOD5/TOC (5-day biological oxygen demand/total organic carbons) ratios of the ozonated Reactive Red 120 and Acid Red 299 solutions would increase and have the maximum values. Moreover, the oxidized textile wastewater revealed the fast decolorization and moderate COD (chemical oxidation demand) removal rates. The optimal ADMI (American Dye Manufactures Institute) and COD removal of the textile wastewater were 93% and 37% in 30 minutes ozonation time, respectively. The performance evaluation of ozonation in the rotating packed bed indicated that the higher water flow rate, gas ozone concentration and rotational rotating speed would increase the efficiency of mineralization.
Asunto(s)
Colorantes/química , Residuos Industriales , Ozono/química , Industria Textil , Contaminantes Químicos del Agua/química , Purificación del Agua/instrumentación , Compuestos Azo/química , Estudios de Evaluación como Asunto , Cinética , Modelos Químicos , Oxidación-Reducción , Taiwán , Triazinas/químicaRESUMEN
The Microtox toxicity and Oxygen Uptake Rate (OUR) inhibition tests were conducted to monitor the variation of toxicity during ozonation of 2-chlorophenol (2-CP), 3-chlorophenol (3-CP) and 4-chlorophenol (4-CP) under neutral conditions. The results revealed that the oxidized 2-CP solution exhibited new toxicity to pure bacteria and mixed microorganisms in the early stage of ozonation. The largest inhibition of OUR appeared at one mol of applied ozone dosage per mol of initial 2-CP, and the percentage of inhibition was 63.8%. In addition, ozonated 3-CP and 4-CP also significantly induced new aqueous toxicity, if these toxic intermediates were not further ozonated. Comparing the variation of toxicity and the hydroxylated/chlorinated intermediates formed, 3-chloro-catechol, 2-chloro-2, 4-hexadienedioic acid and the dimmer compounds may be related to the sources of toxicity during the ozonation of 2-CP.
Asunto(s)
Clorofenoles/química , Clorofenoles/toxicidad , Ozono/química , Contaminantes del Agua/toxicidad , Oxígeno/metabolismo , Photobacterium/efectos de los fármacos , Aguas del Alcantarillado , SolucionesRESUMEN
Taiwan is the second most densely populated country in the world; its 22.604 million residents (2002) live in an area of 35,967 km2 (628 people/km2). Taiwan's economy has grown rapidly during the last 20 years, resulting in a corresponding increase in the amount of municipal solid waste (MSW). This study describes and evaluates the municipal solid waste management system in Taiwan. The study's results indicate that the amount of MSW began to decline after 1997, when the government enforced aggressive MSW management policies. By 2002, total MSW production had dropped by 27%, and the average daily per capita weight of MSW had fallen from 1.14 kg in 1997 to 0.81 kg in 2002. Summarizing the successful experience of MSW reduction in Taiwan, the most important factor was the government's combining of the MSW collection system with reduction/recycling programs. The second most important factor was the policy of extended producer responsibility, which laid a foundation of recycling by producers and retailers and promoted public recycling.
Asunto(s)
Salud Pública , Política Pública , Eliminación de Residuos/legislación & jurisprudencia , Eliminación de Residuos/métodos , Administración de Residuos/métodos , Ciudades , Humanos , Densidad de Población , TaiwánRESUMEN
This study investigates the ozonation of 2-naphthalenesulfonate (2-NS) combined with UV radiation in the electroplating solution. 2-NS is commonly used as a brightening and stabilization agent in the electroplating solution. Semibatch ozonation experiments were conducted under various reaction conditions to study the effects of ozone dosage and UV radiation on the oxidation of 2-NS. The concentrations of 2-NS were analyzed at specified time intervals to elucidate the decomposition of 2-NS. Total organic carbon (TOC) is chosen as a mineralization index of the ozonation of 2-NS. In addition, values of pH and oxidation reduction potential were continuously measured in the course of experiments. As a result, the nearly complete mineralization of 2-NS via the ozonation treatment can be achieved. The mineralization of 2-NS is found accelerated by the introduction of UV radiation and has a distinct relationship with the consumption of applied ozone. These results can provide useful information for the proper removal of 2-NS in the electroplating solution by the ozonation with UV radiation.
Asunto(s)
Galvanoplastia , Ácidos Sulfónicos/química , Rayos Ultravioleta , Purificación del Agua/métodos , Oxidantes Fotoquímicos/química , Oxidación-Reducción , Ozono/química , FotoquímicaRESUMEN
This study investigates the variation of toxicity during ozonation of 2-chlorophenol (2-CP), 3-chlorophenol (3-CP) and 4-chlorophenol (4-CP) in neutral condition. Acute toxicity of pure chlorophenols (CPs) and their ozonated intermediates was evaluated by Microtox assay. The results revealed that the intermediates of oxidized CPs induced new toxicity during the early stage of ozonation, and the ozonated 2-CP showed higher degree of toxicity increase than 3-CP and 4-CP. The maximum toxicity normally occurred before the maximum color intensity was monitored, while ozone dosage applied was within 1 mg of ozone per mg of initial CPs. This increasing toxicity was mainly contributed from ozonated intermediates. Formation of chlorocatechols, chloromuconic acids and hydroxylated/chlorinated dimeric compounds were detected in ozonation of CPs. These chlorinated by-products may cause greater toxicity than the parent chlorophenols. The required ozone dosage to detoxify the CPs solution into a complete non-toxic condition follows the order: 4-CP > 3-CP > 2-CP.