Using resin supported nano zero-valent iron particles for decoloration of Acid Blue 113 azo dye solution.

In this study, a synthesized cation exchange resin supported nano zero-valent iron (NZVI) complex forming NZVI-resin was proposed for the decoloration of an azo dye Acid Blue 113 (AB 113), taking into account reaction time, initial dye concentration, NZVI dose and pH. From results, the successful decoloration of the AB 113 solution was observed using a NZVI-resin. Increasing the iron load to 50.8 mg g(-1), the removal efficiencies of the AB 113 concentration increased exponentially. With an initial dye concentration of 100 mg l(-1) and nano iron load of 50.8 mg g(-1), the best removal efficiencies were obtained at 100 and 12.6% for dye concentration and total organic carbon, respectively. Color removal efficiency was dependent on initial dye concentration and iron load. Moreover, the removal rates followed modified pseudo-first order kinetic equations with respect to dye concentration. Thus, the observed removal rate constants (k) were 0.137-0.756 min(-1) by NZVI loads of 4.9-50.8 mg g(-1). Consequently, the NZVI-resin performed effectively for the decoloration of AB 113 azo dye, offering great potential in the application of NZVI-resins in larger scale column tests and further field processes.

Integration of nanosized zero-valent iron particles addition with UV/H2O2 process for purification of azo dye Acid Black 24 solution.

The challenging national effluent standards for color and organic concentration enforce the industrial concern most the techniques providing fast and efficient solution for the strenuous dye wastewater treatment before outflow. The best remediation technique pursuit is urgently demand for the industrial, government, academia and community. In this study, a di-azo dye, C.I. Acid Black 24, synthesized wastewater was successfully removed synchronously its total color and total organic carbon (TOC) using an integrated innovation technology by coupling the zero-valent iron (ZVI) nanoparticles with UV/H(2)O(2) oxidation process. The nanosized ZVI (NZVI) primarily reduced color successfully following coupling UV/H(2)O(2) oxidation process for the residual organic mineralization resulting reduction with oxidation process (Re-Ox) for total color removal and organic mineralization. From the experimental data, the Re-Ox process consumed shorter time than UV/H(2)O(2) oxidation process alone to obtain total color removal of dye wastewater. Moreover, the residual TOC of dye wastewater after NZVI reduction from 45 to 100% was effectively mineralized by UV/H(2)O(2) process. By using proposed processes integration with NZVI dosage of 0.3348 g l(-1) and hydrogen peroxide concentration of 23.2 mM, in only 10 min the AB24 color was complete eliminated and in 90 min the TOC was 93.9% removed. Thus, the coupling Re-Ox process was developed to provide a superior solution for dye wastewater treatment.

Reduction of an azo dye acid black 24 solution using synthesized nanoscale zerovalent iron particles.

The strong color and high total organic carbon (TOC) of laboratory-synthesized azo dye, C.I. Acid Black 24 (AB24), solution was substantially reduced with particles of chemically synthesized nanoscale zerovalent iron (NZVI) under varied conditions of experimental variables such as NZVI dosage, initial dye concentration, and pH. From the results, the synthesized NZVI particles can effectively remove color and TOC of AB24 dye solution under certain conditions. The best removal efficiencies for color and TOC were obtained as 98.9 and 53.8%, respectively, with an initial dye concentration of 100 mg L(-1) and an NZVI dosage of 0.3348 g L(-1). Additionally, the removal rates followed an empirical rate equation with respect to the initial dye concentration as well as the NZVI dosage. The NZVI dosage addition exponentially increments the removal efficiency, with observed empirical reaction rate constants (k) of 0.046-0.603 min(-1) for added NZVI of 0.0335-0.3348 g L(-1). Moreover, the largest unit removal capacity was 609.4 mg of AB24 uptake for each gram of NZVI (i.e., 609.4 mg AB24/g NZVI). Ultimately, the ideal operation conditions were 0.1674-0.3348 g L(-1) of NZVI dosage, 15-30 min of reaction time, and pH 4-9 for 25-100 mg L(-1) of initial dye concentration.

Remediation of soil contaminated with pyrene using ground nanoscale zero-valent iron.

The sites contaminated with recalcitrant polycyclic aromatic hydrocarbons (PAHs) are serious environmental problems ubiquitously. Some PAHs have proven to be carcinogenic and hazardous. Therefore, the innovative PAH in situ remediation technologies have to be developed instantaneously. Recently, the nanoscale zero-valent iron (ZVI) particles have been successfully applied for dechlorination of organic pollutants in water, yet little research has investigated for the soil remediation so far. The objective in this work was to take advantage of nanoscale ZVI particles to remove PAHs in soil. The experimental factors such as reaction time, particle diameter and iron dosage and surface area were considered and optimized. From the results, both microscale and nanoscale ZVI were capable to remove the target compound. The higher removal efficiencies of nanoscale ZVI particles were obtained because the specific surface areas were about several dozens larger than that of commercially microscale ZVI particles. The optimal parameters were observed as 0.2 g iron/2 mL water in 60 min and 150 rpm by nanoscale ZVI. Additionally, the results proved that nanoscale ZVI particles are a promising technology for soil remediation and are encouraged in the near future environmental applications. Additionally, the empirical equation developed for pyrene removal efficiency provided the good explanation of reaction behavior. Ultimately, the calculated values by this equation were in a good agreement with the experimental data.

Prediction for energy content of Taiwan municipal solid waste using multilayer perceptron neural networks.

In the past decade, the treatment amount of municipal solid waste (MSW) by incineration has increased significantly in Taiwan. By year 2008, approximately 70% of the total MSW generated will be incinerated. The energy content (usually expressed by lower heating value [LHV]) of MSW is an important parameter for the selection of incinerator capacity. In this work, wastes from 55 sampling sites, including villages, towns, cities, and remote islands in the Taiwan area, were sampled and analyzed once a season from April 2002 to March 2003 to determine the waste characteristics. The LHV of MSW in Taiwan was predicted by the multilayer perceptron (MLP) neural networks model using the input parameters of elemental analysis and dry- or wet-base physical compositions. Although all three of the models predicted LHV values rather accurately, the elemental analysis model provided the most accurate prediction of LHV values. Additionally, the wet-base physical composition model was the easiest and most economical. Therefore, the waste treatment operators can choose the more appropriate analysis method considering situations themselves, such as time, equipment, technology, and cost.

An integrated technique using zero-valent iron and UV/H2O2 sequential process for complete decolorization and mineralization of C.I. Acid Black 24 wastewater.

The zero-valent iron (ZVI) reduction succeeds for decolorization, while UV/H(2)O(2) oxidation process results into mineralization, so that this study proposed an integrated technique by reduction coupling with oxidation process in order to acquire simultaneously complete both decolorization and mineralization of C.I. Acid Black 24. From the experimental data, the zero-valent iron addition alone can decolorize the dye wastewater yet it demanded longer time than ZVI coupled with UV/H(2)O(2) processes (Red-Ox). Moreover, it resulted into only about 30% removal of the total organic carbon (TOC), which was capable to be effectively mineralized by UV/H(2)O(2) process. The proposed sequential ZVI-UV/H(2)O(2) integration system cannot only effectively remove color and TOC in AB 24 wastewater simultaneously but also save irradiation power and time demand. Furthermore, the decolorization rate constants were about 3.77-4.0 times magnitude comparing with that by UV/H(2)O(2) process alone.

Remedy of dye manufacturing process effluent by UV/H2O2 process.

The effluent from dye manufacturing industry is more difficult to be treated than laboratory synthesized wastewater according to high variability of composition and color intensity. Thus, this study aimed to propose the method for remedying industrial effluent by UV/H2O2 process in a recirculated batch reactor system while considering the effects on hydrogen peroxide dosage, UV power and wastewater intensity for the removal of color and COD. From the experimental results, it was feasibly treated that the distinguished removal of color and COD by increasing the hydrogen peroxide dosage and UV power, but not by the strong intensity of industrial effluent. Therefore, UV/H2O2 process of the developed reactor was a positively superior treatment or pre-treatment for dye manufacturing plant effluent to comply the regulated requirements.

Decolorization of acid black 24 by the FeGAC/H2O2 process.

FeGAC/H2O2 process was developed and employed in this research for the treatment of acid back 24. The removal efficiencies of five treatment processes (GAC, FeGAC, H2O2, GAC/H2O2, and FeGAC/H2O2) were studied in this research. The adsorption capacity of granular activated carbon (GAC) was greatly improved by the coating of iron oxide on GAC surface (FeGAC). The presence of H2O2 significantly improved the removal abilities of FeGAC and GAC. For instance, at solution pH 2, the removal efficiency of FeGAC/H2O2, GAC/H2O2, H2O2, FeGAC, and GAC were 76, 74, 59, 11, and 7%, respectively. The possible removal mechanisms of FeGAC/H2O2 process were proposed in this research. When treating the actual dye contaminated wastewater, the removal efficiencies of FeGAC/H2O2 and GAC/H2O2 were approximately six times greater than that of H2O2 process.

Treatment of MSW landfill leachate by a thin gap annular UV/H2O2 photoreactor with multi-UV lamps.

The treatment of leachate from landfills is a major disposal problem for municipal solid waste. The leachate is generally recalcitrant to be treated according to complicated characteristics and high color intensity resulting further threat for environment and human health. In this work, the designed thin gap annular photoreactor with 4-UV lamps in UV/H2O2 process was proposed to decolor and remove chemical oxygen demand (COD) from the landfill leachate for solving this environmental problem. Meanwhile, the operating parameters such as UV dosage, hydrogen peroxide concentration and leachate strength were evaluated. The landfill leachate treated with the maximum dosage of 4-UV lamps and 232.7 mM of hydrogen peroxide concentration achieved 72 and 65% of color and COD removal efficiencies in 300 min. As for less concentrated leachate of 20% strength, 91% of color and 87% of COD were removed within only 120 min. From the experimental results, the UV/H2O2 process in this work was an effective pre-treatment or treatment technology for landfill leachate.

Degradation of dyehouse effluent containing C.I. Direct Blue 199 by processes of ozonation, UV/H2O2 and in sequence of ozonation with UV/H2O2.

The decolorization and mineralization of cotton dyeing effluent containing C.I. Direct Blue 199 (DB 199) by advanced oxidation processes (AOPs) such as ozonation, UV/H(2)O(2), and in sequence of ozonation with UV/H(2)O(2) processes were evaluated in this study. By ozonation alone, the color removal was almost 100% for DB 199 and greater than 80% for dye bath effluent rapidly within 5 and 15 min, respectively. Meanwhile, the reduction of total organic carbon (TOC) was about 60% for DB 199 and almost no change for dye bath effluent, respectively due to incomplete mineralization. On the other hand, by UV/H(2)O(2) alone, the color removing not only took longer time but obtained lower removal efficiencies for DB 199 and dye bath effluent about 80% and 95% in 30 and 120 min, respectively. Nevertheless, it was more effective than ozonation for TOC removal while about 75% and 80% in 30 and 120 min, respectively. As a result, this study conducted the combination with the above two processes in order to shorten time demand as well as the higher removal efficiencies of both color and TOC simultaneously. Thus, the sequence process was designed to begin with ozonation to rapidly remove color proficiently, following by UV/H(2)O(2) in order to promptly remove remaining TOC efficiently. The successful process design by sequence of ozonation with UV/H(2)O(2) has proved the significant improvement for the removal of both color and TOC in dye bath effluent shortly. Besides, the lab prepared dye solution was substantially much easier to be decolorized than field dye bath effluent so that the lab results were utilized to design the further applications of pilot or full scale.

Characteristics of landfill leachates in central Taiwan.

Due to the complex nature of landfill leachates, the leachate treatment plants have difficulty to meet the current Taiwan EPA's effluent standards. Three typical types of landfills, closed landfill A, mixed landfill B (disposal of MSW with bottom ashes from MSW incinerators) and direct MSW landfill C, (disposal of MSW only), are investigated in this research in order to have a better understanding of characteristics of leachates. Factors investigated in this research include landfill age, pH, BOD, COD, TS, DS, VS, seasons, metals (Pb, Ca, Cd, Hg, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, and Zn), humic substances (humic acid, fulvic acid, and non-humic substance), aromaticity and toxicity. Results show that the active landfills B and C had the significant higher concentration of COD, VSS, TS, PtCo, TOC and conductivity. The mixed landfill B had the higher DS, TS, Na, Ca, Mg and conductivity than that of direct MSW landfill C. Direct MSW landfill C had the highest contents of Fe, Cr, Ni and acute toxicity among these landfills. A significant degree of variation was encountered and factors which may influence leachate quality were identified and discussed.

Using nanoscale zero-valent iron for the remediation of polycyclic aromatic hydrocarbons contaminated soil.

The sites contaminated with recalcitrant organic compounds, such as polycyclic aromatic hydrocarbons (PAHs) with multiple benzene rings, are colossal and ubiquitous environmental problems. They are relatively nonbiodegradable and mutagenic, and 16 of them are listed in the U.S. Environment Protection Agency priority pollutants. Thus, the efficient and emerging remediation technologies for removal of PAHs in contaminated sites have to be uncovered urgently. In this decade, the zero-valent iron (ZVI) particles have been used successfully in the laboratory, pilot, and field, such as degradation of chlorinated hydrocarbons and remediation of the other pollutants. Nevertheless, as far as we know, little research has investigated for soil remediation; this study used nanoscale ZVI particles to remove pyrene in the soil. The experimental variables were determined, including reaction time, iron particle size, and dosage. From the results, both the micro- and nanoscales of ZVI were capable of removing the target compound in soil, but the higher removal efficiencies were by nanoscale ZVI because of the massive specific surface area. The optimal operating conditions to attain the best removal efficiency of pyrene were obtained while adding nanoscale ZVI 0.1 g/g soil within 60 min and 150 rpm of mixing. Thus, nanoscale ZVI has proved to be a promising remedy for PAH-contaminated soil in this study, as well as an optimistically predictable application for additional pilot and field studies.

Pilot scale annular plug flow photoreactor by UV/H2O2 for the decolorization of azo dye wastewater.

A pilot scale annular plug flow photoreactor with thin gap size, which combines with UV irradiation and hydrogen peroxide, was employed to deal with colored dyeing wastewater treatment. In the experiment, a mono-azo dye acid orange 10 was the target compound. The experimental parameters such as flow rate, hydrogen peroxide dosage, UV input power, pH and dye initial concentrations in a pilot scale photoreactor with flow rate of 9.32 m3day(-1) were investigated. Ultimately, the degradation rates were calculated and compared with a 100-l batch reactor. In our plug flow photoreactor design, the degradation rate of acid orange 10 was 233 times higher than that of 100-l annular batch reactor with same UV light source. The residence time needed for 99% decolorizing of 100 l of 20 mgl(-1) acid orange 10 wastewater was 26.9 min for the thin gap plug flow reactor and was far shorter than that of batch reactor needed.

Decolorization and mineralization of a phthalocyanine dye C.I. Direct Blue 199 using UV/H2O2 process.

In this study, the successful decolorization and mineralization of phthalocyanine dye (C.I. Direct Blue 199, DB 199) by an advanced oxidation process (AOP), UV/H2O2, were observed while the experimental variables such as hydrogen peroxide dosage, UV dosage, initial dye concentration and pH were evaluated. The operating conditions for 90% decolorization of C.I. DB 199 and 74% removal of total organic carbon (TOC) were obtained for initial dye concentration of 20 mgl(-1), hydrogen peroxide dosage of 116.32 mM, UV dosage of 560 W and pH of 8.9 in 30 min. The pseudo-first order rate constant is a linear function of reverse of initial dye concentration. They linearly increased by incrementing UV dosage, yet were non-linear enhancement by increasing the hydrogen peroxide concentration. A higher pseudo-first order rate constant about 0.15 min(-1) was observed while hydrogen peroxide concentration within 5.82-116.32 mM. Moreover, the decolorization of C.I. DB 199 was observed to be more difficult than that of an azo dye, C.I. Acid Black 1, under the same operating conditions.

Pre-ozonation coupled with UV/H2O2 process for the decolorization and mineralization of cotton dyeing effluent and synthesized C.I. Direct Black 22 wastewater.

The decolorization and mineralization of cotton dyeing effluent containing C.I. Acid Black 22 as well as synthesized C.I. Acid Black 22 wastewater by means of advanced oxidation processes (AOPs), such as UV/H2O2, O3 and pre-ozonation coupled with UV/H2O2 processes, were evaluated in this study. It was observed that the UV/H2O2 process took longer retention time than ozonation for color removal of dye bath effluent. Reversely, the total organic carbon (TOC) removal showed different phenomena that ozonation and UV/H2O2 process obtained 33 and 90% of removal efficiency for 160 min of retention time, respectively. Additionally, laboratory synthesized dye wastewater was substantially more efficient in the decolorization process than dye bath effluent. Therefore, in this work, pre-ozonation coupled with UV/H2O2 process was employed to enhance the reduction of both color and TOC in dye bath effluent at the same time. At the same time, the retention time demand was reduced to less than 115 min for 90% removal of TOC and color by this combined process.

Effects of gap size and UV dosage on decolorization of C.I. Acid Blue 113 wastewater in the UV/H2O2 process.

The wastewater from textile dyeing industry is difficult to be treated successfully according to both high variability of composition and color intensity. To investigate the effects of reactor gap size and UV dosage on the decolorization of dye wastewater, a commercially available azo dye C.I. Acid Blue 113 was chosen as a model compound. UV/H2O2 processes with various gap sizes and setups of plug flow reactor and recirculated batch reactor were proposed to deal with the dye wastewater in this study. The experimental parameters including the design of reactor configurations of annular gap size, and in batch system or plug flow reactors and hydrogen peroxide dosage, UV dosage were investigated. The gap size of reactor was adjusted by different diameter of reactor shells in order to optimize the reactor configuration. The color removal percentage was used to evaluate the treatment efficiency. An optimal hydrogen peroxide concentration of 46.53 mM was observed in this study for highest decolorization rate. Besides, the pseudo-first-order rate constant of 3.14 min(-1) was obtained by plug flow reactor with 0.5 cm gap size, 120.70 W/l of UV dosage and 23.27 mM of H2O2 dosage. The first-order rate constant, which was about 20 times less than that of plug flow reactor, was obtained 0.1422 min(-1) by recirculated batch reactor with 2.0 cm gap size, 7.0 W/l of UV and 23.27 mM of H2O2 dosages. Ultimately, we developed an effective pre-treatment or treatment technology for dye wastewater to provide the dyeing industries and dye manufacturers an alternative to meet the effluent standards.

Decolorization of azo dye acid black 1 by the UV/H2O2 process and optimization of operating parameters.

An advanced oxidation process, UV/H2O2, was applied for decolorization of a di-azo dye (acid black 1). The effects of operating parameters such as hydrogen peroxide dosage, UV dosage and initial dye concentration, on decolorization have been evaluated. The acid black 1 solution was completely decolorized under optimal hydrogen peroxide dosage of 21.24 mmol/l and UV dosage of 1400 W/l in less than 1.2 min. The decolorization rate followed pseudo-first order kinetics with respect to the dye concentration. The rate increased linearly with volumetric UV dosage and nonlinearly with increasing initial hydrogen peroxide concentration. It has been found that the degradation rate increased until an optimum of hydrogen peroxide dosage, beyond which the reagent exerted an inhibitory effect. For real case application, an operation parameter plot of rate constant was developed. To evaluate the electric power and hydrogen peroxide consumption by UV/H2O2 reactor, 90% color removal was set as criteria to find the balance between both factors.

Assessment of occupational health hazards in scrap-tire shredding facilities.

Occupational hygiene conditions in scrap-tire shredding facilities were assessed to identify potential health risk factors for workers and provide a basis for developing future control measures. Specifically, noise, volatile organics and particulate levels were measured at two plants. Particulate/dust levels were measured via filter collection, and were analyzed gravimetrically. Sound pressure levels were measured and their spectral properties analyzed. Moreover, the major chemical species in the samples were identified using GC/MS. Finally, the mutagenic activity associated with the airborne particulates was assessed using a typical Ames test applied to Salmonella strains TA98 and TA100, with or without bio-activation. The noise levels were steady and high throughout the facilities, ranging from 85 to approximately 100 dBA. The octave band spectrum analysis reveals pattern similarity among the different areas. Levels of volatile organics were not significant, but a few mutagens/carcinogens, such as styrene, benzothiazole, phthalate ester and naphthalene were identified. Total particulate levels ranged from 0.43 to 6.54 mg/m(3), while respirable particulates were in the range 0.23-1.25 mg/m(3). Ames testing revealed indirect mutagenicity on strain TA98, indicating possible effects of frame-shift type mutagens. Chemical analysis of airborne particulates confirmed the presence of amines, aniline, quinoline, amides and benzothiazole, which are potentially convertible to frame-shift type mutagenic nitrosoamines. Noise appears to be an occupational hazard for workers at scrap-tire shredding facilities, but the risk associated with the mutagenic/carcinogenic property of particulates requires further confirmation.