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1.
The current work deals with efficient removal of acetaminophen (AC) from hospital wastewater using electro-Fenton (EF) process. The degradation yield of 99.5% was obtained under optimal experimental conditions, namely 5.75 mg L?1 initial AC concentration, 2.75 pH solution, 3-cm inter-electrode distance, 100 mg L?1 KCl electrolyte, 122.5 µL L?1 H2O2, 8 mA cm?2 current density at equilibrium time of 8 min. Analysis of variance (ANOVA) suggested that the effect of mentioned operating parameters was statistically significant on the AC removal. The low probability amount of P value (P < 0.0001), the Fisher’s F-value of 65.91, and correlation coefficient of the model (R2 = 0.9545) revealed a satisfactory correlation between the experimental and the predicted values of AC removal. The predicted removal efficiency of 99.4% was in satisfactory agreement with the obtained experimental removal efficiency of 98.7%. The AC degradation during the EF followed a first-order kinetic model with rate constants (Kapp) of 0.6718 min?1. Using the ordinary radical scavengers revealed that main mechanism of AC degradation controlled by the hydroxyl free radicals produced throughout the EF process. The excess amount of iron (II) scavenged the active radicals and diminished the concentration of ·OH available to react with AC. The optimum molar ratio of H2O2 to Fe2+ was found to be 2.5. The developed EF process as a promising technique applied for treatment of real samples.  相似文献   

2.
Street dust is one of the important indicators that reflect the status of urban environmental pollution. There are many studies of heavy metals contamination of street dust in capital cities; however, little attention has been paid to this kind of study in medium cities, including China. The dust samples were collected in the district of traffic crossroads in Xianyang city, Shaanxi Province. Pb, Cd, Cu, Ni, Zn, Cr and Mn concentrations were determined using atomic absorption spectrometry (AAS). The results indicate that the concentrations of heavy metals are higher than the background values of soils in Shaanxi Province. The contamination level of heavy metals is assessed by potential ecological risk index (E r), geoaccumulation index (I geo), enrichment factor (EF) and pollution index (Pi). The low I geo, EF, E r, Pi and PIn (integrated pollution index) for Mn in street dusts indicate an absence of distinct Mn pollution. The high EF, Pi and PIn of Cu and Zn indicate that there is considerable Cu and Zn pollution. It is suggested that more attention should be paid to heavy metals contamination of Cu and Zn. The assessment results of Pi and PIn suggest that Pb, Ni and Cr present strong pollution; however, their EFs indicate that they cause moderate pollution and their I geo indicates that they are unpolluted to moderately polluted. The contamination class value with different assessing methods is of the order: Pi ≈ PIn > EF > I geo > E r.  相似文献   

3.
Exposure to high concentration of nitrate through drinking water poses a threat to human health and environment. Electrocoagulation (EC) is an alternative water treatment process that involves electrogeneration of coagulant agents. In the present study, EC was exerted for the nitrate removal in a batch reactor using aluminum and iron anodes simultaneously. The effects of the main parameters including electrical current, initial pH, NaCl dosage, initial nitrate concentration and presence of turbidity on NO3 ? removal were investigated. NO2 ? as a by-product was monitored during electrolysis, and nitrate–nitrite index was calculated. The results indicated that optimum condition was pH of 5, 300 mA electrical current, 100 mg/L NaCl and electrolysis time of 40 min, under which removal efficiency was 81.5 %. Nitrite anion was generated during electrolysis of nitrate solution which increases nitrate–nitrite index at the first reaction time, and it was eliminated after 20-min electrolysis time. Reaction kinetic of nitrate removal in the absence and presence of turbidity was first-order and zero-order, respectively.  相似文献   

4.
The aim of this research was to evaluate the efficiency of electrocoagulation (EC) for the removal of natural organic matter (NOM) by using iron (Fe) and aluminum (Al) electrodes. The effects of several operational parameters such as initial pH (3–10), time of electrolysis (5–30 min), initial concentration of organic matter (10–50 mg NOM/L), current density (0.25–1.25 mA/cm2), type of electrode material (n = 4, 2 sides × 11 cm × 10 cm, wall thickness = 2 mm, distance between each electrode = 5 mm), and type of connection of electrodes (bipolar and monopolar configurations) were explored for the removal of NOM from synthetic humic acid solution in a 2 L laboratory-scale EC cells (A s/V = 0.110 cm?1). The optimum conditions for the process were identified as pH = 3 and 7, electrolysis time = 20 and 10 min for Fe and Al electrodes, respectively. Using both electrodes at current density = 0.25 mA/cm2 and initial concentration of organic matter = 50 mg/L, a NOM removal efficiency of almost 100% could be achieved in the bipolar mode. Based on the optimum conditions, specific reactor electrical energy consumptions were 14.90 kWh/kg Al (or 0.092 kWh/m3) and 2.88 kWh/kg Fe (or 0.11 kWh/m3). Specific electrode consumptions were obtained to be 0.0062 and 0.0382 kg/m3, and operating costs of the EC system were preliminary estimated at 0.057 and 0.119 $/m3 for Al and Fe electrodes, respectively.  相似文献   

5.
CO2 is a greenhouse gas, whose emissions threaten the existence of human beings. Its inherently safe sequestration can be performed via CO2 mineralization, which is relatively slow under natural conditions. In this work, an energy-saving membrane electrolysis technique was proposed for accelerating the CO2 mineralization of wollastonite into SiO2 and CaCO3 products. The electrolysis process involved splitting NH4Cl into HCl and NH3·H2O via hydrogen oxidation and water reduction at the anode and cathode of the electrolytic system, respectively. In contrast to the chlor-alkali electrolysis, this method did not involve Cl? oxidation and the standard potential of the anode was reduced. Additionally, NH4Cl was used as the electrolyte instead of NaCl; as a result, the generation of NH3·H2O instead of NaOH occurred in the catholyte and the cathodic pH dramatically decreased, thus reducing the cathodic potential for hydrogen evolution. The observed changes led to a 73.5% decrease in the energy consumption. Moreover, after the process of CO2 mineralization was optimized, SiO2 with a specific surface area of 221.8 m2 g?1 and CaCO3 with a purity of 99.9% were obtained.  相似文献   

6.
This paper reports an investigation of different persulfate (PS) activations, including PS at 20 °C (PS), thermally activated PS at 70 °C (T-PS), ferrous-ion activated PS at 20 °C [Fe(II)-PS)], hydrogen peroxide activated PS at 20 °C, and sodium hydroxide activated PS at 20 °C, for degradation of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) in aqueous phase. Several findings were made in this study including the followings: the 2,4-D degradation rates in T-PS and Fe(II)-PS systems were higher than other systems. However, complete degradation of 2,4-D and associated derivatives can be reached in all oxidation systems, with various reaction times. When considering the results of PS consumption during the 48 h reaction time to reach complete 2,4-D degradation, the T-PS system consumed all of the PS while only 10 % of the PS was consumed in the Fe(II)-PS system. The evaluation of optimum PS and ferrous ion doses indicated that under a fixed initial PS concentration, increasing Fe2+ concentration generally increased the amount of initial rapid degradation of 2,4-D and dissolved organic carbon. However, the effectiveness of the Fe(II)-PS system may be inhibited by the presence of excess iron. When a fixed level of Fe2+ was employed, various PS concentrations resulted in approximately equal 2,4-D degradation. The Fe(II)-PS system was found to be sensitive to the initial Fe2+ concentration, and the presence of soil revealed minor influence on the 2,4-D degradation by the Fe(II)-PS system. These findings indicate that the iron-activated PS process may be an effective method for remediating 2,4-D contamination.  相似文献   

7.
The sonochemical degradation of 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) in water and wastewater was investigated at ultrasonic frequency of 850 kHz. The effects of pH, initial concentrations, temperature, power and dissolved organic carbon were examined. The results obtained indicated that the rate of ultrasonic degradation of E2 and EE2 in water and wastewater is influenced by the pH, power, air sparging and the dissolved organic content of the aqueous solutions. Mass degradation rates of E2 and EE2 per kW ranged from 1.7 to 4.0 mg kW?1 at varying process parameters. The degradation process followed the pseudo-second-order kinetic model with rate constant of 1.71 × 10?2 min?1 at 25 °C. The value for activation energy (E a = 15.21 kJ mol?1) obtained from Arrhenius-type plot, indicated that the ultrasonic degradation of steroid hormones is thermodynamically feasible, and does not progress only on radical reactions but other intermediate reaction processes. In wastewater, the higher dissolved organic carbon significantly reduced the effectiveness of degradation of the E2 and EE2 showing that ultrasound treatment will be more effective as a tertiary treatment option in wastewater applications.  相似文献   

8.
The study was taken up to establish the distributions of metals as well as to assess the extent of anthropogenic inputs into the Subarnarekha River. Bed sediments were collected; analyzed for metals; and assessed with the index of geo-accumulation (I geo), enrichment factor (EF) value, concentration factor (CF) and pollution load index (PLI). Metals in the sediment were variable in the river and there are major pollution problems at certain locations. The average concentrations of Fe, Cu, Cr, Pb, Mn, Ni, Zn, Co and Ba in mg/kg was found to be 30,802 ± 11,563, 69 ± 57, 111 ± 74, 75 ± 61, 842 ± 335, 42 ± 22, 100 ± 39, 15 ± 4 and 698 ± 435, respectively. The I geo, EF, CF and PLI indices showed that the contamination of Pb and Cu was more serious than that of Ni, Zn, Co and Ba, whereas the presence of Fe, Mn and Cr might be primarily from natural sources. The contamination of the sediments with metals at few locations is attributed to mining, industries and other anthropogenic causes. Principal component analysis was employed to better comprehend the controlling factors of sediment quality. The statistical analysis of inter-metallic relationship revealed the high degree of correlation among the metals indicated their identical behaviour during transport. PCA outcome of three factors together explained 83.8 % of the variance with >1 initial eigenvalue indicated both innate and anthropogenic activities are contributing factors as source of metal profusion in Subarnarekha River basin.The overall study reveals moderately serious pollution in the river basin principally in some locations under the anthropogenic influences.  相似文献   

9.
Heavy metals are introduced in human tissue through breathing air, food chain and human skin. They can cause damage to the nervous system and internal organs. In the present study, sixty street dust samples were collected from the central area of Tehran and were digested in the laboratory to determine the content of Zn, Ni, Cd, Cr, Cu and Pb, using inductively coupled plasma optical emission spectrometry (ICP-OES). The level of contamination with the analyzed metals was determined according to the following indices: geo-accumulation index (I geo), enrichment factor (EF), pollution index (PI), integrated pollution index (IPI) and potential ecological risk index (RI). The average concentration of heavy metals found was in the order of Zn > Cu > Pb > Ni > Cr > Cd. The average I geo values for Cd, Cr, Cu, Ni, Pb and Zn were 1.53, ?1.88, 2.68, ?0.67, 1.62 and 2.70, respectively. Among the investigated heavy metals, zinc and copper had the maximum average EF values and were placed into the “very severe enrichment” class. Potential ecological risk factor (E r) also indicated that Cd had the highest risk, and it was classified as of considerable potential ecological risk. Therefore, it is necessary to pay more attention to the appearance of Cd in the human environment. The calculated potential ecological risk index values also illustrated that the street dust samples presented a “moderate ecological risk.” The calculated IPI values showed that the pollution levels of the street dust samples ranged from high to extremely high.  相似文献   

10.
Wanshan mercury mine is the largest cinnabar deposit in Guizhou, China. Few effective methods had been achieved to remedy Hg heavily contaminated field soils. In this paper, a modified EK method with approaching cathodes (AC-EK) and an I−/I2 lixiviant was described to remedy mercury-contaminated field soils near Wanshan mercury mine. Paddy Soil I and Paddy Soil II were sampled and contained 576.73 ± 45.50 and 491.35 ± 4.73 mg/kg Hg, respectively. Although they contained 6.9 and 9.4% organic matter respectively, more than 92 and 89% Hg were removed by AC-EK within 5 days. Removal ratio increased by 0.21 and 0.68 times using EK process with ACs over that with one single cathode (SC-EK). AC-EK method saved nearly 26.4–28.1% electric power as compared to SC-EK method. As an I−/I2 lixiviant solution was used to solubilize HgS(HgO) during EK process, the bonding of Hg to organic functional S groups should be less important than the binding to inner sites of organic matter in soil. The relationship between EK remediation effect and soil organic matter content was fitted to a linear model. It turned out that when soil OM increased by 1.0%, EK removal ratio (%) of Hg would decrease by 2.63%.  相似文献   

11.
The present research work was intended to find out the useful information on identification, separation and photocatalytic degradation of organic compounds present in leather industry wastewater. The separation of organic compounds present in leather industry wastewater was carried out by solvent extraction. The separated crude extracted products were purified through column chromatography and characterized by UV–vis spectrophotometer, gas chromatography–mass spectrophotometer, liquid chromatography–mass spectrophotometer, 1H and 13C Fourier-transform nuclear magnetic resonance spectroscopy. The elemental analysis of wastewater and solid residue was carried out by inductively coupled plasma-optical emission and X-ray fluorescence spectroscopy. The organic compounds such as nonadec-1-ene, 2-phenylethanol, 2,4-di-tert-butylphenol and other organic compounds in the leather industry wastewater were identified. Out of these organic compounds, 2-phenylethanol was photocatalytically degraded using standard Degussa P-25 TiO2 (100 mg) photocatalyst under the irradiation of UV light. Result has been shown that 2-phenylethanol was transformed into 2-tert-butyl-4,6-dimethylphenol, 2,6-di-tert-butyl-4-methylphenol then the prolonged time (30 h) irradiation leads to 100 % degradation of 2-phenylethanol. Further possible degradation mechanism of 2-phenylethanol was proposed based on the electrospray ionization mass spectrometry analysis of degraded samples. The degradation of 2-phenylethanol was confirmed by chemical oxygen demand analysis of degraded samples. The physicochemical parameters such as pH, color, chemical oxygen demand, total dissolved solids, electrical conductivity and ionic chromatography analysis of the leather industry wastewater were also measured.  相似文献   

12.
This investigation evaluates the effectiveness of UV-365 nm/S2O8 2? process in degrading polyvinyl alcohol in aqueous solutions. The effects of pH, Na2S2O8 dosage, and temperature on the degradation efficiency of polyvinyl alcohol were studied. Under acidic conditions, the degradation efficiency of polyvinyl alcohol exceeded that under alkaline conditions. Additionally, a higher Na2S2O8 dosage and a higher temperature were associated with a higher degradation efficiency of polyvinyl alcohol. The degradation rates of polyvinyl alcohol followed a pseudo-first-order kinetic model. Moreover, the observed degradation rate coefficient increased from 0.0078 to 0.4081 min?1 when the temperature was increased from 10 to 55 °C. Also, the activation energy estimated using the observed degradation rate coefficients and the Arrhenius equation was 64 kJ/mol. At UV-365 nm, pH 3, an Na2S2O8 dosage of 0.06 g/L, a temperature of 55 °C, and an initial polyvinyl alcohol concentration of 20 mg/L, around 100 % of polyvinyl alcohol was degraded, indicating that UV-365 nm/S2O8 2? process has great potential in degrading polyvinyl alcohol in aqueous solutions.  相似文献   

13.
The electrochemical decolorization of the Reactive Violet 5 azo dye on a boron-doped diamond anode was used as a model process to test a novel definitive screening design (DSD). This method allows a dramatic reduction in the number of experiments needed to investigate those systems characterized by a large number of variables. In this study, the effect of nine quantitative parameters was investigated: initial dye concentration (60–120 mg L?1), current density (100–500 A m?2), NaCl concentration (5–20 mM), Na2SO4 concentration (35–65 mM), pH (3–11), temperature (20–45 °C), inter-electrode distance (0.5–3.5 cm), stirring rate (250–750 rpm) and electrolysis time (2–8 min). Analysis of DSD data showed that four out of the nine factors (initial dye concentration, current density, pH and electrolysis time) were statistically significant. These factors were retained for process characterization using a subsequent central composite design. Overall, the number of experiments was reduced from over 500 to only 41, thus confirming the validity of the proposed approach as a time-saving and efficient method.  相似文献   

14.
During dyeing process, industries consume large quantity of water and subsequently produce large volume of wastewater. This wastewater is rich in color and contains different dyes. Orange II is one of them. In this article, metal-impregnated TiO2 P-25 catalyst was used to enhance the photocatalytic degradation of Orange II dye. Photodegradation percentage was followed spectrophotometrically by the measurements of absorbance at λ max = 483 nm. The effect of copper-impregnated TiO2 P-25 photocatalyst for the degradation of Orange II has been investigated in terms of percentage removal of color, chemical oxygen demand (COD) and total organic carbon (TOC). As such 98 % color removal efficiency, 97 % percentage removal of COD and 89 % percentage removal of TOC was achieved with TiO2 P-25/Cu catalysts under typical conditions. Copper-impregnated TiO2 P-25 photocatalyst showed comparatively higher activity than UV/H2O2 homogeneous photodegradation. The relative electrical energy consumption for photocatalytic degradation was considerably lower with TiO2 P-25/Cu photocatalyst than that with homogeneous photodegradation. Transmission electron microscopic analysis was used for catalyst characterization.  相似文献   

15.
Groundwater systems are important sources of water for drinking and irrigation purposes. Unfortunately, human activities have led to widespread groundwater contamination by chlorinated compounds such as tetrachloroethene (PCE). Chloroethenes are extremely harmful to humans and the environment due to their carcinogenic properties. Therefore, this study investigated the potential for bioremediating PCE-contaminated groundwater using laboratory-based biostimulation (BS) and biostimulation–bioaugmentation (BS-BA) assays. This was carried out on groundwater samples obtained from a PCE-contaminated site which had been unsuccessfully treated using chemical oxidation. BS resulted in complete dechlorination by week 21 compared to controls which had only 30 % PCE degradation. BS also led to a approximately threefold increase in 16S rRNA gene copies compared to the controls. However, the major bacterial dechlorinating group, Dehalococcoides (Dhc), was undetectable in PCE-contaminated groundwater. This suggested that dechlorination in BS samples was due to indigenous non-Dhc dechlorinators. Application of the BS-BA strategy with Dhc as the augmenting organism resulted in complete dechlorination by week 17 with approximately twofold to threefold increase in 16S rRNA and Dhc gene abundance. Live/dead cell counts (LDCC) showed 70–80 % viability in both treatments indicating active growth of potential dechlorinators. The LDCC was strongly correlated with cell copy numbers (r > 0.95) suggesting its potential use for low-cost monitoring of bioremediation. This study also shows the dechlorinating potential of indigenous non-Dhc groups can be successfully exploited for PCE decontamination while demonstrating the applicability of microbiological and chemical methodologies for preliminary site assessments prior to field-based studies.  相似文献   

16.
Socioeconomic developments and industrialization exert tremendous impact on beaches which is often neglected. Heavy metal (Cr, Mn, Co, Ni, Cu, Zn, Cd, and Pb) contents were estimated in the intertidal region from Kalpakkam to Mamallapuram (20 km), southeast coast of India covering seven locations. To evaluate the level of contamination of these metals; enrichment factor (EF), geoaccumulation index (I geo), contamination factor (CF), pollution load index (PLI) and modified degree of contamination (mCd) were applied. The results were also compared with the sediment quality guidelines (SQGs) to find out the eco-toxicity level. Metal contents in the beach sediment were observed in the order: Fe > Al > Mn > Cr > Cu > Ni > Zn > Pb > Co > Cd. Grain size distribution showed medium to coarse nature of the sediment. Significant positive correlation was found among the metals indicating their common source of input. Based on EF, minor enrichment of Mn and Zn and moderately severe to severe enrichment of Cr, Cu, Pb and Cd were observed which was further confirmed by I geo and CF values. Moreover, Mamallapuram showed a very high CF value for Cd (>6) indicating very high contamination accountable to anthropogenic sources. PLI and mCd in all the stations indicated unpolluted nature except M1 where the values pointed moderate degree of contamination. As per the SQGs, Ni and Cr values exceeded the probable effect limit value implying that these metals can have adverse impacts. None of the metals exceeded the effect range median indicating that the beach sediment is not very toxic.  相似文献   

17.
Phenol biodegradation in an aerobic batch reactor was investigated using mixed two co-aggregating strains (Flavobacterium sp. and Acetobacter sp.). Response surface methodology by the Box–Behnken model was used to evaluate the optimal cell growth and phenol degradation conditions. The optimum temperature, pH value and inoculum size were found to be 33 °C, 6.06 and 13 %, respectively. In the conditions, phenol degradation rate and biomass were predicted to be 96.97 % and 410.78 mg/L within the range examined, respectively. Less toxic acetaldehyde, ethanol and acetic ether were identified as main intermediate products from the degraded samples using GC–MS. Substrate inhibition was calculated from experimental biomass growth and phenol degradation parameters using the Haldane equation. Kinetic parameters derived from nonlinear regression with correlation factors (R 2) were 0.9682 for phenol degradation and 0.9594 for biomass growth, respectively. The phenol concentration to avoid substrate inhibition was 278.17 mg/L.  相似文献   

18.
The emergence of antibiotics residues in pharmaceutical industrial wastewater has been a significant environment problem. However, current methods of treating antibiotic-polluted wastewater are inefficient, of high cost and time-consuming. In this study, highly effective enzymatic Fe3O4 magnetic nanoparticles were developed, which is extremely simple and can degrade antibiotics in a fast manner at a low cost. β-Lactamase, a representative enzyme for β-lactam antibiotic degradation, was covalently immobilized on the surface of magnetic nanoparticles modified with amino groups by a simple cross-linking process. The immobilized β-lactamase displayed a wider pH and temperature range for penicillin G degradation than the free enzyme. Meanwhile, the thermostability and storage stability of the immobilized β-lactamase were improved. Fifty milligrams magnetic nanoparticles immobilized with β-lactamase can thoroughly degrade 100 mL penicillin G (5–50 mg L?1) within 5 min. Even if the β-lactamase immobilized on the nanoparticles was reused 35 times in the 5 mg L?1 penicillin G solution, it still kept more than 95% degradation efficiency. These suggest that magnetic nanoparticles immobilized with β-lactamase have a sufficient capacity for degrading antibiotics in wastewater and will serve as a practical and economical solution to antibiotic pollution in pharmaceutical industrial wastewater treatment.  相似文献   

19.
Instrumental and historical data on mainshocks for 13 seismogenic sources in western Anatolia have been used to apply a regional time- and magnitude-predictable model. Considering the interevent time between successive mainshocks, the following two predictive relations were computed: log T t = 0.13 M min + 0.21 M p ? 0.15 log M 0 + 2.93 and M f = 0.87 M min ? 0.06 M p + 0.33 log M 0 ? 6.54. Multiple correlation coefficient and standard deviation have been computed as 0.50 and 0.29, respectively, for the first relation, and 0.65 and 0.47, respectively, for the second relation. The positive dependence of T t on M p and the negative dependence of M f on M p indicate the validity of time- and magnitude-predictable model on the area considered in this study. On the basis of these relations and using the occurrence time and magnitude of the last main shocks in each seismogenic source, the probabilities of occurrence P(Δt) of the next main shocks during the next 50 years with decade interval as well as the magnitude of the expected main shocks were determined. The highest probabilities P 10 = 80 % (M f = 6.8 and T t = 13 years) and P 10 = 32 % (M f = 7.6 and T t = 29 years) were estimated for the seismogenic source 11 (Golhisar-Dalaman-Rhodes) for the occurrence of a strong and a large earthquake during the future decade, respectively.  相似文献   

20.
The biosorption of ammoniacal nitrogen (N-NH4 +) from aqueous solutions by dead biomass of brown seaweed Cystoseira indica and Jatropha oil cake (JOC), which is generated in the process of biodiesel recovery from its seeds, was studied under diverse experimental conditions. The N-NH4 + biosorption was strictly pH dependent, and maximum uptake capacity of C. indica (15.21 mg/g) and JOC (13.59 mg/g) was observed at initial pH 7 and 3, respectively. For each biosorbent–N-NH4 + system, kinetic models were applied to the experimental data to examine the mechanisms of sorption and potential rate-controlling steps. The generalized rate model and pseudo-second-order kinetic models described the biosorption kinetics accurately, and the sorption process was found to be controlled by pore and surface diffusion for these biosorbents. Results of four-stage batch biosorber design analysis revealed that the required time for the 99 % efficiency removal of 40 mg/L N-NH4 + from 500 L of aqueous solution were 76 and 96 min for C. indica and JOC, respectively. The Fourier transform infrared spectroscopy analysis before and after biosorption of ammonium onto C. indica and JOC revealed involvement of carboxylic and hydroxyl functional groups.  相似文献   

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