Cationic surfactants influencing the enhancement of energy efficiency for perfluorooctanoic acid (PFOA) removal in the electrocoagulation-flotation (ECF) system.

From an environmental perspective, approaching sustainability requires a fundamental conceptual shift from the wastewater treatment process toward integrated treatment systems that consider efficient and effective utilization. This study aims to investigate the effects of different surfactants on the removal of perfluorooctanoic acid (PFOA). We used cationic surfactants as both frothers and collectors in the electrocoagulation-flotation (ECF) method to improve the removal efficiency of PFOA. The results showed that, under a monopolar aluminum electrode and with an initial PFOA concentration of 0.25 mM, the ECF method with decyl-trimethyl-ammonium bromide (DTAB) was able to remove over 98% of PFOA within 10 min. Cationic surfactants with a similar linear alkyl chain shape to PFOA, but a longer chain length, are more effective at removing PFOA through the ECF process. The removal mechanism is thought to involve co-precipitation with aluminum hydroxides through Al-F bonding, co-flotation with cationic surfactants, and mixed micelle formation with cationic surfactants. The optimal conditions were tested in both synthetic and realistic wastewater matrices and produced similar results. It has the potential for real wastewater application. The energy yield (G50) of ECF with 5 mM DTAB is 497 g·kWh-1, superior to other treatments, and is an extremely energy-effective method for separating PFOA from wastewater.

Effects of zinc salt addition on perfluorooctanoic acid (PFOA) removal by electrocoagulation with aluminum electrodes.

In this study, the electrocoagulation (EC) of perfluorooctanoic acid (PFOA) by an aluminum electrode with the addition of zinc salt was investigated. Adding ZnCl2 successfully prevented a rise in pH during EC and increased the efficiency from 73.7% to over 99%. In addition, the longer the carbon chain of a PFA was, the better the removal of that PFA by electrocoagulation. The main functions of ZnCl2 were to prevent the rise in pH and improve flotation because the flocs with added ZnCl2 were easy to gather together and had a faster floating speed. The XPS results demonstrated the occurrence of bonding between aluminum and fluoride. This finding indicates that complexation between aluminum and fluoride may be the main mechanism for removal when aluminum electrodes are used to remove perfluoroalkyl (PFA) compounds.

Comparison of the degradation of multiple amine-containing pharmaceuticals during electroindirect oxidation and electrochlorination processes in continuous system.

The degradation of pharmaceuticals by electrochemical oxidation (EO) in simulated wastewater containing multiple pharmaceuticals was compared between batch and continuous reactors. Despite the excellent efficiencies achieved in batch experiments, the practical/large-scale applications of EO-degrading amine-containing pharmaceuticals has not yet been accomplished. This paper presents the results of continuous experiments with one of the most promising electrochemical configurations of Pt/Ti electrodes before proceeding to application. In the continuous electrooxidation system (without chloride), direct oxidation on the electrode surface and oxidation by hydroxyl radicals were the main pathways. Due to their short lifespans, the radicals could not be transferred to the bulk solution, and the removal of pharmaceuticals followed the order of sulfamethoxazole (SMX) > paracetamol (PAR) > diclofenac (DIC). In the electrochlorination system (with chloride), oxidation by residual chlorine was the main pathway. The removal of pharmaceuticals followed the order of sulfamethoxazole (SMX) > diclofenac (DIC) > paracetamol (PAR). High SMX removal was realized because of the high reaction rate of SMX with free chlorine. Among the pharmaceuticals, PAR had the lowest removal because it is a neutral species with a low mass transfer rate without the attraction of electrostatic force. These results are consistent with the predictions from our previous batch-scale study, which showed that the reaction rate of dissociated compounds could be increased by the addition of electrostatic force. Furthermore, multiple coexisting pharmaceuticals, such as SMX and PAR or DIC, may form dimers that can be transferred to complex structures and cause higher toxicity.

Perfluorooctanoic acid (PFOA) removal by flotation with cationic surfactants.

Perfluorooctanoic acid (PFOA) was separated and recovered using a foam flotation process aided by cationic surfactants. The PFOA removal efficiency was in the following decreasing order: OTAB (C8TAB) > DTAB (C10TAB) > CTAB (C16TAB) > TBAB, which indicates that cationic surfactants with an alkyl chain that had a similar length to that of PFOA had higher affinities to PFOA. PFOA removal slightly decreased with increasing ionic strength of the surfactant but did not change with the pH. PFOA could be completely removed in 20 min with 1.25 mM of OTAB in actual wastewater. The energy yield value of foam flotation with a cationic surfactant was much higher than those of other methods, which means that using foam flotation with a cationic surfactant as the collector is a simple, fast, and energy-efficient method to separate and recover PFOA from dilute water solutions.

Effects of Surfactants on the Degradation of Diclofenac by Manganese Oxide.

Amine-containing pharmaceuticals are the most often detected pharmaceuticals in wastewater and ambient aquatic environments. They can usually be degraded by manganese oxide (MnO2), which is a common natural oxidant in soils. Surfactants often coexist with pharmaceuticals in wastewater. Some amine-containing pharmaceuticals, such as diclofenac (DIC), are acidic and are thus ionic compounds in neutral conditions. These compounds, therefore, have similar properties to surfactants. Surfactants, thus, may influence the adsorption and degradation processes of DIC by MnO2. The effect of the type of surfactant on the degradation of DIC by MnO2 was investigated in this study with the addition of two common biodegradable surfactants (cetyltrimethyl-ammonium bromide (CTAB) and sodium dodecylsulfate (SDS)). The results indicated that the cationic surfactant (CTAB) significantly increased the degradation rate in neutral and alkaline conditions. On the other hand, the anionic surfactant (SDS) slightly increased the DIC removal rate in an acidic condition but significantly decreased the removal in neutral and alkaline conditions. Coexisting cationic surfactants not only influenced the kinetics but also altered the transformation mechanism of DIC by MnO2. Decarboxylation is the main transformation mechanism of DIC in the presence of CTAB, while both decarboxylation and hydroxylation are the main transformation mechanisms in the absence of CTAB.

Simultaneous aqueous chlorination of amine-containing pharmaceuticals.

Amine-containing pharmaceuticals such as acetaminophen, diclofenac, and sulfamethoxazole are the most often detected pharmaceuticals in wastewater and other aquatic environments. Amine-containing pharmaceuticals can be effectively removed by chlorination. These drugs, however, may coexist in wastewater. Thus, they may compete with each other, and their chlorinated products may react with each other to form new products. In this study, competitive effects of the above three amine-containing pharmaceuticals by chlorination and their products were investigated. The priority of chlorination of these compounds was dependent upon the pH of the solution, due to the dissociation of the compounds and hypochlorite. It followed the order of sulfamethoxazole > diclofenac > acetaminophen in an acidic condition, the order of sulfamethoxazole > acetaminophen > diclofenac in a neutral condition, and the order of sulfamethoxazole ≈ acetaminophen > diclofenac in an alkaline condition. Some of the chlorinated products in single- and multiple-compound systems were the same. Dimers of sulfamethoxazole and its chlorinated products, however, were not found, but dimers of sulfamethoxazole and acetaminophen or diclofenac were found in multiple-compound systems. This finding is important because it means that new products may be produced if different amine-containing pharmaceuticals react with free chlorine simultaneously.

Direct and indirect electrochemical oxidation of amine-containing pharmaceuticals using graphite electrodes.

This study investigated the direct and indirect electro-oxidation of amine-containing pharmaceuticals (acetaminophen (ACT), diclofenac (DIC), and sulfamethoxazole (SMX)) by using graphite electrodes, and to compare the influence by using different electrolytes (Na2SO4 and NaCl). Under the optimum conditions of current (I) at 0.5 A, in direct system, 74.3%, 90.0%, 81.6% of ACT, DIC, and SMX were respectively removed after 60 min (k = 0.023, 0.037, 0.027 min-1), 48.9%, 85.9%, 68.2% of TOC respectively removed after reaction time. In contrast, at the same current intensity, in indirect system, ACT, DIC, and SMX were eliminated within 30 min (k = 0.117, 0.307, 0.170 min-1), 89.6%, 92.6%, 99.6% of TOC respectively removed after reaction time. The results indicated that the dissociated compounds were attracted to the anode due to electrostatic forces and had higher mass transformation rates in the direct electro-oxidation process. According to the cyclic voltammogram, indirect oxidation occurred when active chlorine species were generated from chloride ions anodically to destroy pollutants. Based on intermediates detected during electro-oxidation treatment by ultra performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS), only oxidized intermediates were found in the direct oxidation system, while both oxidized and chlorinated intermediates were found in the indirect oxidation system.

Soil-to-skin adherence during different activities for children in Taiwan.

Children may be exposed to environmental contaminants through incidental ingestion of soil resulting from hand-to-mouth contact. We measured soil adherence to the skin among 86 children from four kindergartens and one elementary school in Taiwan. Rinse water samples were collected from the hands, forearms, feet and lower legs of children after they had engaged in assigned activity groups (pre-activity, indirect contact and direct contact) from two different soil textures groups: sand and clay. We found that the soil loadings significantly differed between the different soil textures, body parts, activities, and clothing groups. Measured soil loadings for hands of pre-activity, indirect contact activity, and direct contact activity groups were 0.0069, 0.0307 and 0.153 mg cm-2, respectively, for the group playing on sand and 0.0061, 0.0116 and 0.0942 mg cm-2, respectively, for the group playing on clay. To facilitate the use of soil adherence data in exposure assessments, we provided a new and simple way to group activities based on the intensity of children's interactions with soil. The adherence data from this study can help enhance existing information based on soil-to-skin adherence factors used to assess children's exposure to soil contaminants during their play activities.

Determination of hand soil loading, soil transfer, and particle size variations after hand-pressing and hand-mouthing activities.

Hand-pressing trials and hand-to-mouth soil transfer experiments were conducted to better understand soil loadings, soil transfer ratios for three mouthing activities, and variations in particle size distributions under various conditions. Results indicated that sand caused higher soil loadings on the hand than clay. When the moisture level of clay soil exceeded its liquid limit, soil loadings also increased. Greater pressing pressures also led to larger clay loadings. Clay with a moisture content close to its plastic limit caused the smallest soil loadings due to strong soil cohesion. Particle sizes of the transferred clay were larger than that of the original clay, indicating that hand-pressing and the pressure exerted may have enhanced clay particles of larger sizes adhering onto the hand. Nevertheless, the sizes of most particles that adhered to the hand were still smaller than 150 µm. Higher pressing pressures and greater moisture contents resulted in larger soil loadings on the hand, and transfer ratios became smaller. Transfer ratios from palm-licking with clay particles were smaller than those from finger-mouthing, which may have been due to finer particles that more readily adhered to the skin of the palm and that were transferred from the hand to the mouth with greater difficulty.

Effect of surfactants on the degradation of perfluorooctanoic acid (PFOA) by ultrasonic (US) treatment.

Perfluorooctanoic acid (C7F15COOH, PFOA) is an aqueous anionic surfactant and a persistent organic pollutant. It can be easily adsorbed onto the bubble-water interface and both mineralized and degraded by ultrasonic (US) cavitation at room temperature. The aim of this study is to investigate whether the effect of US on the degradation of PFOA in solution can be enhanced by the addition of surfactant. To achieve this aim, we first investigated the addition of a cationic (hexadecyl trimethyl ammonium bromide, CTAB), a nonionic (octyl phenol ethoxylate, TritonX-100), and an anionic (sodium dodecyl sulfate, SDS) surfactant. We found the addition of CTAB to have increased the degradation rate the most, followed by TritonX-100. SDS inhibited the degradation rate. We then conducted further experiments characterizing the removal efficiency of CTAB at varying surfactant concentrations and solution pHs. The removal efficiency of PFOA increased with CTAB concentration, with the efficiency reaching 79% after 120 min at 25°C with a 0.12 mM CTAB dose.

The inter-relationship among economic activities, environmental degradation, material consumption and population health in low-income countries: a longitudinal ecological study.

OBJECTIVES: The theory of ecological unequal exchange explains how trade and various forms of economic activity create the problem of environmental degradation, and lead to the deterioration of population health. Based on this theory, our study examined the inter-relationship among economic characteristics, ecological footprints, CO2 emissions, infant mortality rates and under-5 mortality rates in low-income countries. DESIGN: A longitudinal ecological study design. SETTING: Sixty-six low-income countries from 1980 to 2010 were included in the analyses. Data for each country represented an average of 23 years (N=1497). DATA SOURCES: Data were from the World Development Indicators, UN Commodity Trade Statistics Database, Global Footprint Network and Polity IV Project. ANALYSES: Linear mixed models with a spatial power covariance structure and a correlation that decreased over time were constructed to accommodate the repeated measures. Statistical analyses were conducted separately by sub-Saharan Africa, Latin America and other regions. RESULTS: After controlling for country-level sociodemographic characteristics, debt and manufacturing, economic activities were positively associated with infant mortality rates and under-5 mortality rates in sub-Saharan Africa. By contrast, export intensity and foreign investment were beneficial for reducing infant and under-5 mortality rates in Latin America and other regions. Although the ecological footprints and CO2 emissions did not mediate the relationship between economic characteristics and health outcomes, export intensity increased CO2 emissions, but reduced the ecological footprints in sub-Saharan Africa. By contrast, in Asia, the Middle East and North Africa, although export intensity was positively associated with the ecological footprints and also CO2 emissions, the percentage of exports to high-income countries was negatively associated with the ecological footprints. CONCLUSIONS: This study suggested that environmental protection and economic development are important for reducing infant and under-5 mortality rates in low-income countries.

Enhanced sonochemical degradation of perfluorooctanoic acid by sulfate ions.

This study investigated the effects of sulfate ions on the decomposition of perfluorooctanoic acid (PFOA) by ultrasonic (US) irradiation at various pHs, sulfate doses, powers and temperatures. The removal of PFOA was augmented with an increased sulfate ion concentration, with PFOA being almost completely decomposed in 90min at 25°C with a sulfate dose of 117mM. The two major mechanisms in the sulfate-assisted sonochemical system are the direct destruction of PFOA by cavitation and the indirect destruction of PFOA by sulfate free radicals. The decomposition of PFOA followed pseudo-first-order kinetics and was not influenced by pH. The reaction rate constants decreased with increases in temperature due to decreases in the surface tension of the solution.

Degradation of antibiotic amoxicillin using 1 x 1 molecular sieve-structured manganese oxide.

The kinetics and mechanism ofamoxicillin (AMO) degradation using a 1 x 1 molecular sieve-structured manganese oxide (MnO2) was studied. The presence of the buffer solution (i.e., NaHCO3, NaH2PO4 and KH2PO4) diminished AMO binding to MnO2, thus reducing AMO degradation in the pretest; therefore, all other experiments in this study were conducted without the addition of a buffer. Third-order rate constants, second-order on AMO and first-order on MnO2 increased with elevating pH level (2.81-7.23) from 0.54 to 9.17 M(-2) s(-1), and it decreased to 4.27 M(-2) s(-1) at pH 8.53 beyond the pk(a2) of AMO (7.3). The dissolution of the MnO2 suspension with and without AMO exhibited a similar trend; that is, Mn2+ concentration increased with decreasing pH. However, the dissolution of MnO2 with AMO was greater than that without AMO, except for the reaction occurring at pH 8.53, partially indicating that MnO2 acts as an oxidant in AMO degradation. The preliminary chromatogram data display different products with varying pH reaction s, implying that AMO elimination using this 1 x 1 molecular sieve-structured MnO2 is by adsorption as well as oxidative degradation. A complementary experiment indicates that the amount of oxidatively degraded AMO increases substantially from 65.5% at 4 h to 95% at 48 h, whereas the AMO adsorbed onto MnO2 decreases slightly from 4.5% at4 h to 2.4% at 48 h. The oxidative degradation accounted for more AMO removal than adsorption over the whole reaction course, indicating that the oxidative reaction of AMO on MnO2 dominated the AMO removal.

Combined effects of noise, vibration, and low temperature on the physiological parameters of labor employees.

Noise, vibration, and low temperature render specific occupational hazards to labor employees. The purpose of this research was to investigate the combined effects of these three physical hazards on employees' physiological parameters. The Taguchi experimental method was used to simulate different exposure conditions caused by noise, vibration, and low temperature, and their effects on the physiological parameters of the test takers were measured. The data were then analyzed using statistical methods to evaluate the combined effects of these three factors on human health. Results showed that the factor that influenced the finger skin temperature, manual dexterity, and mean artery pressure (MAP) most was air temperature, and exposure time was the second most influential factor. Noise was found to be the major factor responsible for hearing loss; in this case, hand-arm vibration and temperature had no effect at all. During the study, the temperature was confined in the 5-25°C range (which was not sufficient to study the effects at extremely high- and low-temperature working conditions) because the combined effects of even two factors were very complicated. For example, the combined effects of hand-arm vibration and low temperature might lead to occupational hazards such as vibration-induced white finger syndrome in working labors. Further studies concerning the occupational damage caused by the combined effects of hazardous factors need to be conducted in the future.

The effects of salinity and temperature on phase transformation of copper-laden sludge.

To stabilize the copper and aluminum ions in simulated sludge, a series of sintering processes were conducted to transform Cu/Al precipitation into spinel structure, CuAl(2)O(4). The results indicated that the large amount of salt content in the simulated sludge would hinder the formation of crystalline CuAl(2)O(4) generated from the incorporation of CuO and Al(2)O(3), even after the sintering process at 1200 °C. Opposite to the amorphous CuAl(2)O(4), the crystalline CuAl(2)O(4) can be formed in the sintering process at 700-1100 °C for 3 h with the desalinating procedure. According to the theory of free energy, the experimental data and references, the best formation temperature of CuAl(2)O(4) was determined at 900-1000 °C. As the temperature rose to 1200 °C, CuAlO(2) was formed with the dissociation of CuAl(2)O(4). The XPS analysis also showed that the binding energy of copper species in the simulated sludge was switched from 933.8 eV for Cu(II) to 932.8 eV for Cu(I) with the variation of temperature. In this system, the leaching concentration of copper and aluminum ions from sintered simulated sludge was decreased with ascending temperature and reached the lowest level at 1000 °C. Furthermore, the descending tendency coincided with the formation tendency of spinel structure and the diminishing of copper oxide.

Effect of low frequency noise on the echocardiographic parameter E/A ratio.

The hearing condition of the Taiwanese aerospace maintenance workers affected by the low frequency noise had not been reported. The purpose of this research is to clarify the maintenance workers' health effect when exposed to low frequency and/or general noises and to understand the relationship between the variations of the worker's echocardiographic E/A ratio and the low frequency noise. The low frequency noise monitoring and echocardiographic E/A ratio results obtained for 213 aerospace maintenance workers indicated that the workers' hearing loss was more serious at high frequency 4k and 6k when exposed to the low frequency noise and could be more than 40 dB. The abnormality of echocardiographic E/A ratio was also higher than that of control group.

Stabilization of nickel-laden sludge by a high-temperature NiCr2O4 synthesis process.

The feasibility of stabilizing nickel-laden sludge by a high-temperature NiCr(2)O(4) synthesis process was investigated with different sintering temperatures, salt contents, molar ratios, and reaction atmospheres. The crystalline phases of species were investigated by using an X-ray diffraction, and the surface characteristics of particles were observed by scanning electron microscopy. The leaching behavior of the stabilized sludge was evaluated by Toxicity Characteristic Leaching Procedure (TCLP) test. The results indicated that NiCr(2)O(4) was formed at around 800°C by transforming NiO and Cr(2)O(3) into a spinel structure. Leaching concentrations of both nickel and chromium decreased with an increase in the sintering temperature. The existence of salt in the sludge disturbed the formation of spinel, but a moderate salt content contributed to stabilization efficiency. A Cr/Ni molar ratio >2 also contributed to the stabilization efficiency of heavy metals after the thermal process. NiCr(2)O(4) was transformed from simulated sludge under both an N(2) and air atmosphere. The sintering strategy designed for nickel-laden sludge was proven to be beneficial in stabilizing nickel and chromium.

Stabilization and phase transformation of CuFe2O4 sintered from simulated copper-laden sludge.

The feasibility of stabilizing copper-laden sludge by high-temperature CuFe(2)O(4) ferritization process is investigated with different sintering temperature, and the prolonged leaching test. The thermal behavior, structural morphology, phase composition, and phase transformation of the stabilized sludge were investigated by using thermal gravimetry-differential scanning calorimetry, scanning electron microscopy and X-ray diffraction. The leaching behavior of the stabilized sludge under acidic environment was evaluated by modified Toxicity Characteristic Leaching Procedure (TCLP). The results indicated that CuFe(2)O(4) could be effectively formed at around 800°C by the iron oxide precursor with a 3h of short sintering. The transformation was discovered on crystallographic spinel structures: the low-temperature (800-900°C) tetragonal phase (t-CuFe(2)O(4)) and the high-temperature (∼ 1000°C) cubic phase (c-CuFe(2)O(4)). At higher temperatures (∼ 1100°C), the formation of cuprous ferrite delafossite phase (CuFeO(2)) from the dissociation of CuFe(2)O(4) was also noticed. Both CuFe(2)O(4) spinel and CuFeO(2) delafossite phase have a better intrinsic resistance to acidic environment when compared to that of CuO phase by the modified TCLP test. The sintering strategy designed for copper-laden sludge is proven to be beneficial in stabilizing copper.

Formation of copper aluminate spinel and cuprous aluminate delafossite to thermally stabilize simulated copper-laden sludge.

The study reported herein indicated the stabilization mechanisms at work when copper-laden sludge is thermally treated with gamma-alumina and kaolinite precursors, and evaluated the prolonged leachability of their product phases. Four copper-containing phases - copper oxide (CuO), cuprous oxide (Cu(2)O), copper aluminate spinel (CuAl(2)O(4)), and cuprous aluminate delafossite (CuAlO(2)) - were found in the thermal reactions of the investigated systems. These phases were independently synthesized for leaching by 0.1M HCl aqueous solution, and the relative leachabilities were found to be CuAl(2)O(4)

Hexavalent chromium removal from near natural water by copper-iron bimetallic particles.

The reduction of hexavalent chromium (Cr(VI)) by zero-valent iron (ZVI) is self-inhibiting in near natural groundwater because insulating Fe(III)-Cr(III) (oxy)hydroxide film forms on the ZVI surface during the reaction. This study tries to overcome this deficiency by coating the surface of ZVI with copper to form copper-iron bimetallic particles. The Cr(VI) removal rate by ZVI rose significantly after the copper coating was applied. The copper loading needed for enhancing Cr(VI) removal was much higher than that needed for enhancing removal of chlorinated organic compounds or other oxidative contaminants, because of the higher oxidation potential of Cr(VI). The results of X-ray photoelectron spectroscopy (XPS) indicate that coating copper onto the surface of ZVI can not only increase the deepness of the oxidation film but also increase the oxidation state of iron in the film. This phenomenon means higher Cr(VI) removal capacity per unit weight of ZVI.