The steel industry in Taiwan produces more than 3 million tons of steelmaking slag per year on average. Conventional solidification and landfilling methods are no longer suitable for the highly ...populated small island as a wide area is needed for such methods. This study aims to improve the quality of polluted water bodies using desulfurization slag – a recycled product resulted from steelmaking – as an arsenate adsorbent. Experimental results revealed that desulfurization slag pH and metal ions including Ca, Mg, Fe, and Mn affected the behavior and content of arsenate existing in an aqueous solution. The concentration of Ca among these metal ions is the highest in the aqueous solution, which facilitates the formation of calcium hydroxyarsenate and is therefore more critically beneficial than other metal ions in removing As in the aqueous solution. Additionally, desulfurization slag samples with particle size of >200 mesh had a greater specific surface area compared to those in other particle sizes, suggesting preferable As adsorption ability of slag with higher mesh numbers. Such desulfurization slag samples were thus used in subsequent adsorption experiments in this study. The energy dispersive spectrometry results confirmed that the >200‐mesh group comprised the highest metal oxide content in terms of As removal. This study found that under different Cl− and SO42− concentrations, the covalent bond effect did not significantly affect the slag's ability to adsorb As. According to the adsorption isotherm experiment results, the Langmuir model (R2 = 0.998) outperformed the Freundlich model (R2 = 0.961) possibly because the former is suitable for situations with even energy distribution and monolayer adsorption, while the latter is often applied to scenarios with uneven distribution and multilayer adsorption, indicating that the adopted desulfurization slag adsorbed arsenate through the mechanism of monolayer adsorption. There are many useful contents in the desulfurization slag. In terms of sustainable use of resources, desulfurization slag is worthy of economic development and reusing if recycled. Currently, there is little research and information on desulfurization slag in Taiwan. Hopefully, this study will be helpful for future development and application of desulfurization slag in recycling techniques.
In this study, incorporated hexadecyltrimethylammonium (HDTMA) cations to smectite via ion exchange and formed the modified smectite‐HDTMA, a kind of organoclay catalyst. Besides analyzing its ...physical properties, we also adopted it to conduct adsorption experiments on organic pollutants such as aniline and pentachlorophenol (PCP). In terms of the adsorption of organic pollutants, adsorption reaction reached the saturation point within 2 h and remained unchanged after reaching 8 h when smectite‐HDTMA with a pH value of 7 was used to bind aniline. Moreover, adsorption reaction reached the saturation point within 2 h and remained unchanged after reaching 24 h when smectite‐HDTMA with a pH value of 7 was used to bind PCP. This study also found that high adsorption efficiency of smectite‐HDTMA towards aniline could be achieved; there was a slow but steady increase in the adsorption capacity of smectite‐HDTMA when its equilibrium concentration reached 100 mg/L. Besides, batch adsorption experiments using two solvents showed that smectite‐HDTMA mainly bound aniline and PCP via distribution, meaning that the adsorption capacity of the smectite‐HDTMA remains the same no matter how many kinds of organic compounds are presented and that competitive adsorption does not occur.
This study assesses the concentrations of the 54 ozone precursors (all being volatile organic compounds (VOCs)) detected at the four photochemical assessment monitoring stations that are part of the ...air quality monitoring network in the Kaohsiung-Pingtung area in Taiwan. Factor and cluster analyses of the multivariate statistical analysis are performed to explore the interrelationship among the 10 VOCs of relatively higher concentrations selected from the 54 ozone precursors to identify significant factors affecting ozone pollution levels in the study area. Moreover, the multivariate statistical analysis can faithfully reflect why the study area has been affected by photochemical pollution. First, results of the factor analysis suggest that the factors affecting how photochemical reactions occur in the study area can be divided into the following: “pollution from mobile sources”, “pollution from stationary sources”, and “pollution from energy sources”. Among them, mobile sources have the greatest impact on photochemical pollution levels. Second, the impacts of photochemical pollution on air quality in the study area can be classified into four clusters via cluster analysis. Each cluster represents how the 10 VOCs affect air quality, with different characteristics, and how they contribute to photochemical pollution in the study area. If there are more types and samples of photochemical pollutants when performing a multivariate statistical analysis, the analysis results will be more stable. This study adopts data on VOC monitoring over a period of nearly two years, which can effectively improve the validity and reliability of the factor analysis results, while helping environmental agencies review the effectiveness of air quality management in the future and serving as reference for the effectiveness of reducing photochemical pollution in the atmosphere.
Multivariate statistics have been applied to evaluate the water quality data collected at six monitoring stations in the Feitsui Reservoir watershed of Taipei, Taiwan. The objective is to evaluate ...the mutual correlations among the various water quality parameters to reveal the primary factors that affect reservoir water quality, and the differences among the various water quality parameters in the watershed. In this study, using water quality samples collected over a period of two and a half years will effectively raise the efficacy and reliability of the factor analysis results. This will be a valuable reference for managing water pollution in the watershed. Additionally, results obtained using the proposed theory and method to analyze and interpret statistical data must be examined to verify their similarity to field data collected on the stream geographical and geological characteristics, the physical and chemical phenomena of stream self-purification, and the stream hydrological phenomena. In this research, the water quality data has been collected over two and a half years so that sufficient sets of water quality data are available to increase the stability, effectiveness, and reliability of the final factor analysis results. These data sets can be valuable references for managing, regulating, and remediating water pollution in a reservoir watershed.
The subject of this study was the dust collected from an electric arc furnace at an unidentified-waste treatment site in southern Taiwan. The dust underwent an in situ vitrification (ISV) process and ...was tested using the toxicity characteristic leaching procedure (TCLP), at the end of which the final product was analyzed for its stability and weather resistance. This study then examined the above results to determine whether the ISV process helps to enhance the efficiency and economic benefits of said waste-treatment site. A TCLP test conducted on the dust that had been treated with ISV revealed that concentrations of various heavy metals were not only far below those of the unprocessed sample dust but also fell below the limit stipulated in the TCLP regulation of Taiwan’s Environmental Protection Administration. The results show that after undergoing ISV treatment, heavy metals in the dust were either encapsulated or bound in silicon lattices and thus barely leached from the dust. Analyses using scanning electron microscopy (SEM) and an energy dispersive spectrometry (EDS) indicate that the surface of the dust appeared more compacted after going through the ISV process. In addition, the highly contaminated dust that underwent ISV treatment saw a pronounced decrease in or elimination of wave crests. Another analysis applying X-ray diffraction (XRD) showed that the SiO2 crests disappeared in the processed dust, suggesting that the crystal structure was replaced with quasi-vitreous products after ISV treatment. In the event that pollutants were extant, they were usually characterized by smaller size, high stability, excellent weather resistance, an innocuous nature, and recyclability.
This study adopted the exponential generalized autoregressive conditional heteroscedasticity (EGARCH) model to examine the 10 ozone precursors of the highest concentrations among the 54 that were ...assessed over a number of years at the four photochemical assessment monitoring stations (PAMSs) in the Kaohsiung–Pingtung Area in Taiwan. First, the 10 ozone precursors, which were all volatile organic compounds (VOCs), were analyzed using the factor analyses in multiple statistical analyses that had the most significant impact on the area’s ozone formation: mobile pollution factor, which included 1,2,4-Trimethylbenzene (C9H12), toluene (C7H8), and Isopropyl benzene (C9H12). Then, taking into consideration that the number sequences might be affected by standardized residuals, this study applied the vector autoregressive moving average-EGARCH (VARMA-EGARCH) model to analyze the correlation between the three VOCs under different polluting activities. The VARMA-EGARCH model in this research included dummy variables representing changing points of variance structures in the variance formula to predict the conditional variance. This process proved able to effectively estimate the relevant coefficients of the three VOCs’ dynamic conditions that changed with time. The model also helped to prevent errors from occurring when estimating the conditional variance. Based on the testing results, this study determined the VARMA(2,1)-EGARCH(1,0) as the most suitable model for exploring the correlation between the three VOCs and meteorological phenomena, as well as the interplay between them in regard to interaction and formation. With the most representative of the three, toluene (TU), as the dependent variable and 1,2,4-Trimethylbenzene (TB) and Isopropyl benzene (IB) as the independent variables, this study found it impossible to calculate the TU concentration with TB and IB concentrations in the same period; estimations of TB and IB concentrations with a period of lag time were required because TU was mainly contributed by automobiles and motorcycles in Kaohsiung. TB and IB resulted from other stationary pollution sources in the region besides cars and motorbikes. When TU was evenly distributed and stayed longer in the atmosphere, the TB and IB concentrations were lower, so distribution conditions and concentrations could not be used to effectively estimate the concentration of toluene. This study had to wait until the next period, or when stationary pollution sources started producing TB and IB of higher concentrations during the daytime, in order to estimate the TU concentrations in a better photochemical situation.
This study adopted the Exponential Generalized Autoregressive Conditional Heteroscedasticity (EGARCH) model to analyze seven air pollutants (or the seven variables in this study) from ten air quality ...monitoring stations in the Kaohsiung–Pingtung Air Pollutant Control Area located in southern Taiwan. Before the verification analysis of the EGARCH model is conducted, the air quality data collected at the ten air quality monitoring stations in the Kaohsiung–Pingtung area are classified into three major factors using the factor analyses in multiple statistical analyses. The factors with the most significance are then selected as the targets for conducting investigations; they are termed “photochemical pollution factors”, or factors related to pollution caused by air pollutants, including particulate matter with particles below 10 microns (PM10), ozone (O3) and nitrogen dioxide (NO2). Then, we applied the Vector Autoregressive Moving Average-EGARCH (VARMA-EGARCH) model under the condition where the standardized residual existed in order to study the relationships among three air pollutants and how their concentration changed in the time series. By simulating the optimal model, namely VARMA (1,1)-EGARCH (1,1), we found that when O3 was the dependent variable, the concentration of O3 was not affected by the concentration of PM10 and NO2 in the same term. In terms of the impact response analysis on the predictive power of the three air pollutants in the time series, we found that the asymmetry effect of NO2 was the most significant, meaning that NO2 influenced the GARCH effect the least when the change of seasons caused the NO2 concentration to fluctuate; it also suggested that the concentration of NO2 produced in this area and the degree of change are lower than those of the other two air pollutants. This research is the first of its kind in the world to adopt a VARMA-EGARCH model to explore the interplay among various air pollutants and reactions triggered by it over time. The results of this study can be referenced by authorities for planning air quality total quantity control, applying and examining various air quality models, simulating the allowable increase in air quality limits, and evaluating the benefit of air quality improvement.
This study used the soil representative of Taitung in Taiwan, Santai (St) series soil, as the catalyst carrier and exchanged arboxydecyltriethylammonium chloride (CDTEA) onto it through ion exchange, ...forming nano-level St-CDTEA organoclay via surface modification and high-temperature sintering. The physical and chemical properties of the St-CDTEA organoclay were then studied via a series of physical and chemical experiments.
First, an analysis of the basic properties of St series soil shows that it does not have a high organic matter content because it is affected by either rainfall erosion or intensive farming, which causes a decrease in organic matter after it is consumed or lost. The Fourier-transform infrared spectroscopy (FT-IR) analysis suggests that compared with the unmodified St series soil, C-H bonds are found between 2900 cm-1 and 2850 cm-1 and COOH bond around 1750 cm-1 in St-CDTEA organoclay. A field emission scanning electron microscope (FE-SEM) analysis shows the formation of a crystal structure on the surface of the St-CDTEA organoclay because St series soil contains a larger amount of smectite and the structure of the St-CDTEA organoclay absorbs a significant amount of CDTEA molecules (the molecular structure of CDTEA contains three ethyls) after high-temperature sintering.
This article used bentonite impregnated with titanium and silver, respectively, as photocatalyst, to degrade methylene blue (MB) under conditions of MB solutions exposed to sodium lamp and sunlight. ...Due to the semi-conducting properties of synthesized bentonite catalysts, when exposed to sodium lamp and sunlight, catalyst particles are excited for photocatalysis to achieve decolourization. After an FT-IR analysis, this study finds that smectite catalysts have significant and complicated wave crests between the fingerprint area with wave numbers 415∼600 cm−1 and 75∼1170 cm−1. The bentonite impregnated with Ti4+ (Sm-Ti) and with Ag+ (Sm-Ag) removes MB through the mechanisms of adsorption and degradation, while the commercial product of titanium dioxide (TiO2) only exhibits the capability of MB degradation. At present, a heterogeneous photocatalytic system has been fully applied for use in daily life, with its efficiency determined by the free radical action of electrons and holes, the generation efficiency of ·OH.
As steelmakers scale up production to meet the rising demand for steel worldwide, waste generated from steelmaking continues to increase as well. This study adopted sieve analysis and microwave ...digestion to explore the kish graphite content in the desulfurization slag at a steel mill in southern Taiwan. Moreover, it also explored the physical properties of desulfurization slag through various physical and chemical approaches, such as observing the surface and structure of desulfurization slag using a field emission scanning electron microscope (FE-SEM). First, the results of the sieve analysis indicated that there was 8.51% of kish graphite in the desulfurization slag, which increased substantially to 28.7% after the slag underwent acid digestion. Second, a proximate analysis showed that the desulfurization slag mainly consisted of noncombustible elements, with only a smattering of combustible content. Apart from some kish graphite, the slag was mostly composed of iron-containing materials. Finally, an FE-SEM analysis revealed that the kish graphite's surface was covered by many impurities, mostly iron oxides, meaning that the amount of carbon content should be slightly lower if an FE-SEM analysis is conducted on kish graphite with cleaner surfaces.
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