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1.
In the present study arsenic contaminated simulated water and groundwater was treated by the combination of biological oxidation of tri-valent arsenite [As (III)] to penta-valent arsenate [As (V)] in presence of Acidothiobacillus ferrooxidans bacteria and its removal by adsorptive filtration in a bioreactor system. This method includes the immobilisation of A.ferrooxidans on Granulated Activated Carbon (GAC) capable of oxidising ferrous [Fe (II)] to ferric [Fe (III)]. The Fe (III) significantly converts the As (III) to As (V) and ultimately removed greater than 95% by the bed of GAC, limestone, and sand. The significant influence of Fe (II) concentration (0.1–1.5?gL?1), flowrate (0.06–0.18?Lh?1), and initial As (III) concentration (100–1000?µgL?1) on the arsenic removal efficiency was investigated. The simulated water sample containing the different concentration of As (III) and other ions was used in the study. The removal of other co-existing ions present in contaminated water was also investigated in column study. The concentration of arsenic was found to be <10?µgL?1 which is below Maximum Contaminant Level (MCL) as per WHO in treated water. The results confirmed that the present system including adsorptive-filtration was successfully used for the treatment of contaminated water containing As (III) ions.  相似文献   

2.
Microwave-hydrothermal treatment of persistent and bioaccumulative perfluorooctanoic acid (PFOA) in water with persulfate (S2O 8 2? ) has been found effective. However, applications of this process to effectively remediate PFOA pollution require a better understanding on free-radical scavenging reactions that also take place. The objectives of this study were to investigate the effects of pH (pH = 2.5, 6.6, 8.8, and 10.5), chloride concentrations (0.01?C0.15 mol·L?1), and temperature (60°C, 90°C, and 130°C) on persulfate oxidation of PFOA under microwave irradiation. Maximum PFOA degradation occurred at pH 2.5, while little or no degradation at pH 10.5. Lowering system pH resulted in an increase in PFOA degradation rate. Both high pH and chloride concentrations would result in more scavenging of sulfate free radicals and slow down PFOA degradation. When chloride concentrations were less than 0.04 mol·L?1 at 90°C and 0.06 mol·L?1 at 60°C, presence of chloride ions had insignificant impacts on PFOA degradation. However, beyond these concentration levels, PFOA degradation rates reduced significantly with an increase in chloride concentrations, especially under the higher temperature.  相似文献   

3.
大同盆地是典型的高砷地下水分布区。利用从地方性砷中毒严重病区山阴县采集的高砷地下水样品,用稀释培养法实验研究了外加砷源对地下水中微生物数量的影响;同时基于生物学可培养法和16S rDNA序列比对法,选取代表性高砷水样,研究了耐砷菌的种群特征。结果表明,外加砷源对地下水中微生物数量影响显著,高浓度砷会抑制大部分微生物生长,使微生物数量减少;低浓度砷对微生物生长具有一定促进作用。通过多次分离、纯化从3个不同砷含量地下水样中分离到多株砷抗性菌,经鉴定属于主要为BacillusPseudomonasPaenibacillusAeromonasEnterobacter5个属。从RDP(Ribosomal Database Project)分析显示3个水样可培养微生物组成不同,都有生存能力强能够耐低浓度NaAsO2的Bacillales,优势耐砷菌是γ-proteobacteria,其中Enterbacter具有耐高浓度NaAsO2的能力。  相似文献   

4.
砷浓度、形态及碳酸氢盐对蜈蚣草吸收砷的影响   总被引:1,自引:0,他引:1  
为了探讨超富集植物蜈蚣草在处理高砷地下水方面的可行性,研究了水培条件下砷的浓度、形态和碳酸氢盐(HCO-3)对超富集植物蜈蚣草吸收砷的影响。实验中使用了浓度为0.1~100mg·L-1的As(III)和As(V)溶液。HCO-3处理中,HCO-3浓度范围为0.5~20mmol·L-1,As(III)或As(V)的浓度为5mg·L-1。结果表明,在水培条件下,蜈蚣草具有明显的耐高砷特征。当介质砷含量高达100mg·L-1时,砷的去除率可达到80%,且对As(III)的吸收效率高于As(V)。植物体内砷形态研究表明,蜈蚣草体内2种形态砷的含量与外源砷形态有一定的关系,As(V)处理条件下,植物体中的As(V)比例较As(III)处理高。高浓度的HCO-3(20mmol·L-1)处理对蜈蚣草地上部分生物量没有明显影响,但是抑制了地下部分的生长,并且对砷的吸收表现出明显的抑制作用。  相似文献   

5.
Titanium dioxide (TiO2) is a promising sorbent for As removal. There are two main and physico-chemically distinct polymorphs of TiO2 in nature, namely anatase and rutile. Since the difference of arsenic removal by the two polymorphs of TiO2 is now well known, study on the arsenic removal efficiency and the underlying mechanism is of great significance in developing new remediation strategies for As-polluted waters. Here batch experiments were carried out in combination with instrumental analysis of X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) to investigate the effects, influential factors and mechanisms of As removal from aqueous solution by two types of nano TiO2 crystals. The adsorption behavior of anatase and rutile for As(V) and As(III) are well described by Freundlich equations. Anatase had higher As removal efficiency and adsorption capacity than rutile. Solution pH had no influence on the As adsorption of anatase TiO2, whereas the As removal by rutile TiO2 was increased by 7?C18% with pH from 4 to 10. Presence of accompanying anions such as phosphate, silicate, nitrate and sulfate, decreased the As(V) and As(III) removal by both crystals, with phosphate being the most effective. However, removal of As by rutile TiO2 was greatly enhanced in the presence of divalent cations i.e. Ca2+ and Mg2+. Shading of light decreased the removal of As(V) and As(III) of anatase by 15.5% and 17.5%, respectively, while a slight increase of As removal was observed in the case of Rutile TiO2. FT-IR characterization of As(V) or As(III)-treated nano TiO2 crystals indicated that both Ti-O and As-O groups participated in As adsorption. Both FT-IR and XPS analysis demonstrated that As(III) was photooxidated into As(V) when adsorbed by anatase under the light condition. Thus, the effect of crystal types and light condition on As removal should be taken into consideration when nano TiO2 is applied for As removal from water.  相似文献   

6.
As a biomass agricultural waste material, coconut shells were used for the preparation of high-quality modified activated carbon. Chemical modification of the surface of the prepared activated carbon is done by oxidation using H2O2 and HNO3, respectively. The surface area and pore volume of the coconut shells activated carbon are increased by the chemical modification, and followingly the removal of the metals is improved. The structural morphology and composition of the modified activated carbon coconut shells (MACCS) were evaluated by Fourier transform infrared (FTIR) spectra, thermogravimetric analysis–differential thermal analysis (TGA-DTA), scanning electron microscope (SEM), X-ray diffraction (XRD), surface area analysis (SAA), X-ray fluorescence (XRF), and carbon, hydrogen, nitrogen, and sulfur (CHNS) elemental analysis. The prepared MACCS has reasonably good chemical stability. The influence of solution pH, contact time, adsorbent dosage, adsorption temperature, initial metal concentrations, and interfering ions on the adsorption performance of the investigated ions onto the prepared sorbent was examined by a batch method. The selectivity sequence for sorption of Eu3+, Ce3+, Sr2+, and Cs+ ions on MACCS was found to be Eu3+?>?Ce3+?>?Sr2+?>?Cs+. The saturation capacities of MACCS for the studied metal ions were found to be 136.84, 85.55, 69.85, and 60.00?mg?g?1 for Eu3+, Ce3+, Sr2+, and Cs+ ions, respectively. The thermodynamic parameters, ΔH°, ΔS°, and ΔG° were also evaluated.  相似文献   

7.
The kinetics of the oxidation of endocrine disruptor nonylphenol (NP) by potassium ferrate(VI) (K2FeO4) in water as a function of pH 8.0–10.9 at 25°C is presented. The observed second-order rate constants, k obs, decrease with an increase in pH 269–32 M?1 s?1. The speciation of Fe(VI) (HFeO 4 ? and FeO 4 2? ) and NP (NP–OH and NP–O?) species was used to explain the pH dependence of the k obs values. At a dose of 10 mg L?1 (50 μM) K2FeO4, the half-life for the removal of NP by Fe(VI), under water treatment conditions, is less than 1 min.  相似文献   

8.
Biosorption properties of arsenate [As(V)] onto activated sludge were investigated in batch systems. The adsorption of As(V) onto sludge increased from 23 to 266 μg/g dry weight through the methylation of the activated sludge. This increase resulted from neutralization of carboxylic groups via the methylation process. The pH effect of As(V) uptake was also investigated and As(V) adsorption by methylated sludge decreased significantly at high pH (pH > 11) due to competition between As(V) and OH ions for binding sites distributed on sludge surfaces. In contrast, low pH favored As(V) adsorption by methylated sludge because of the elevated quantities of positively charged functional groups. The results suggest that methylated activated sludge may provide promising applications for the simultaneous removal and separation of As(V) from aqueous effluents.  相似文献   

9.
Photoelectro-Fenton was applied for the removal of acid yellow 36 (AY36) from synthetic aqueous solution using iron electrodes. A Box–Behnken design was used for optimization of the effects of pH, H2O2 concentration, current density, and reaction time. Individual effects of these variables were more important than their interaction effects. The derived model was in good agreement with the experimental results. Total organic carbon was determined in solution and sludge in order to clarify the removal mechanism. Increase of H2O2 concentration and current density led to domination of oxidation and coagulation mechanisms, respectively. The effects of scavenging and inhibiting agents were also investigated: (1) presence of alcohols can reduce the efficiency through competition with dye for reaction with hydroxyl radicals; (2) anions (NO3?, HCO3?, and H2PO4?) scavenged hydroxyl radicals and reduced decolorization of AY36.  相似文献   

10.
This research investigates the adsorption mechanisms of fluoride (F) on four clay minerals (kaolinite, montmorillonite, chlorite, and illite) under different F? concentrations and reaction times by probing their fluoride superficial layer binding energies and element compositions using X-ray photoelectron spectroscopy (XPS). At high F? concentrations (C 0 = 5?C1000 mg·L?1), the amount of F? adsorbed (Q F), amount of hydroxide released by clay minerals, solution F? concentration, and the pH increase with increasing C 0. The increases are remarkable at C 0>50 mg·L?1. The QF increases significantly by continuously modifying the pH level. At C 0<5?C100 mg·L?1, clay minerals adsorb H+ to protonate aluminum-bound surface-active hydroxyl sites in the superficial layers and induce F? binding. As the C 0 increases, F?, along with other cations, is adsorbed to form a quasi-cryolite structure. At C 0>100 mg·L?1, new minerals precipitate and the product depends on the critical Al3+ concentration. At [Al3+]>10?11.94 mol·L?1, cryolite forms, while at [Al3+]<10?11.94 mol·L?1, AlF3 is formed. At low C 0 (0.3?C1.5 mg·L?1), proton transfer occurs, and the F? adsorption capabilities of the clay minerals increase with time.  相似文献   

11.
Carbonate shells have an astonishing ability in the removal of Cd2+ in a short time period with emphasis on being a low cost adsorbent. In the present study, the sorption capacity of carbonate shells was studied for Cd2+ in batch experiments. The influence of different carbonate shell sizes and physico-chemical factors were evaluated and the results were analyzed for its correlation matrices by using Predictive Analytics Software (PASW). The mineralogy state of aqueous solution regarding the saturation index was simulated using PHREEQC to identify the Cd2+ uptake mechanism. The Cd uptake rates were calculated as well as Ca2+, HCO 3 ? concentration, pH, ambient humidity and temperature were measured. Cd2+ removal of 91.52% was achieved after 5 h adsorption. The adsorption efficiencies were significantly influenced by pH as they increased with the increase of pH from acidic solution (5.50±0.02) to slightly alkaline (7.60±0.05). In addition, the mineralogy state of aqueous solution calculated from PHREEQC confirmed that the increment of Ca2+ and HCO 3 ? concentrations in solution was attributed to the dissolution of carbonate shells. Moreover, the ion exchange adsorption mechanism of Cd2+ toward Ca2+ was identified as the process involved in Cd2+ uptake.  相似文献   

12.

Biochar derived from food waste was modified with Fe to enhance its adsorption capacity for As(III), which is the most toxic form of As. The synthesis of Fe-impregnated food waste biochar (Fe-FWB) was optimized using response surface methodology (RSM), and the pyrolysis time (1.0, 2.5, and 4.0 h), temperature (300, 450, and 600 °C), and Fe concentration (0.1, 0.3, and 0.5 M) were set as independent variables. The pyrolysis temperature and Fe concentration significantly influenced the As(III) removal, but the effect of pyrolysis time was insignificant. The optimum conditions for the synthesis of Fe-FWB were 1 h and 300 °C with a 0.42-M Fe concentration. Both physical and chemical properties of the optimized Fe-FWB were studied. They were also used for kinetic, equilibrium, thermodynamic, pH, and competing anion studies. Kinetic adsorption experiments demonstrated that the pseudo-second-order model had a superior fit for As(III) adsorption than the pseudo-first-order model. The maximum adsorption capacity derived from the Langmuir model was 119.5 mg/g, which surpassed that of other adsorbents published in the literature. Maximum As(III) adsorption occurred at an elevated pH in the range from 3 to 11 owing to the presence of As(III) as H2AsO3? above a pH of 9.2. A slight reduction in As(III) adsorption was observed in the existence of bicarbonate, hydrogen phosphate, nitrate, and sulfate even at a high concentration of 10 mM. This study demonstrates that aqueous solutions can be treated using Fe-FWB, which is an affordable and readily available resource for As(III) removal.

  相似文献   

13.
The effect of feed seawater temperature on the quality of product water in a reverse osmosis process was investigated using typical seawater at Urla Bay, Izmir region, Turkey. The tests were carried out at different feed seawater temperatures (11–23°C) using two RO modules with one membrane element each. A number of variables, including pH, conductivity, total dissolved solids, salinity, rejection percentage of a number of ions (Na+, K+, Ca2+, Mg2+, Cl, HCO3 , and SO4 2−), and the levels of boron and turbidities in collected permeates, were measured. The suitability of these permeates as irrigation and drinking water was checked by comparison with water quality standards.  相似文献   

14.
The pollution characteristics of PM2.5 and correlation analysis with meteorological parameters in Xinxiang during the Shanghai Cooperation Organization Prime Ministers’ Meeting were investigated. During the whole meeting, nine PM2.5 samples were collected at a suburban site of Xinxiang, and the average concentration of PM2.5 was 122.28 μg m?3. NO3 ?, NH4 +, SO4 2? accounted for 56.8% of the total water-soluble ions. In addition, with an exception of Cl?, all of water-soluble ions decreased during the meeting. Total concentrations of crustal elements ranged from 6.53 to 185.86 μg m?3, with an average concentration of 52.51 μg m?3, which accounted for 82.5% of total elements. The concentrations of organic carbon and elemental carbon were 7.71 and 1.52 μg m?3, respectively, lower than those before and after the meeting. It is indicated that during the meeting, limiting motor vehicles is to reduce exhaust emissions, delay heating is to reduce the fossil fuel combustion, and other measures are to reduce the concentration of PM2.5. The directly dispersing by mixing layerheight increase and the indirectly reducing the formation of secondary aerosol by low relative humidity, andthese are the only two key removing mechanisms of PM2.5 in Xinxiang during the meeting.  相似文献   

15.
The kinetics of famotidine (FAM) transformation under the influence of various factors, important from the environmental point of view, was investigated in aqueous solutions. The degradation processes using UV, H2O2, UV/H2O2, H2O2/Fe2+, and UV/H2O2/Fe2+ were studied. Direct photolysis and H2O2-assisted photolysis showed a pseudo-first-order kinetics, while the Fenton and the photo-Fenton processes fit second-order kinetics. The provided experiments proved a high resistance of FAM to direct photolysis. Its stability depends highly on the pH of the reaction solutions. The rate of FAM direct photolysis in acidic solutions was almost negligible. The reaction rate of FAM photolysis at pH 8–9 was 3.7 × 10?3 min?1 with DT50 about 3 h 7 min. It was found that the presence of H2O2 in the reaction environment enhances the rate of photolysis of FAM. The observed rates of reaction were 5.1 × 10?3 min?1 and 3.7 × 10?3 min?1 in acidic and basic solutions, respectively. The used Fenton systems appeared to be the most efficient in FAM removal. The rate of reaction depends on concentration of Fe2+ and H2O2. It was observed that the presence of UV-light enhances the reaction rate by two to six times in comparison to the classical Fenton system. Additionally, FAM behavior in natural water under solar irradiation was examined. The irradiation experiments were carried out in batch experiments with simulated sunlight.  相似文献   

16.
In this work, a new procedure for the enrichment of the trace amount of Cu2+, Ni2+, Co2+, Pb2+, Fe2+, and Zn2+ ions based on the utilization of multiwalled carbon nanotubes (MWCNT) modified with 2-(2-hydroxy-5-nitrophenyl)-4,5-diphenyl imidazole as chelating agent prior to their determination by flame atomic absorption spectrometry has been described. The influence of effective parameters including pH, amount of ligand and MWCNT, composition of eluent, and coexisting ions on recoveries of understudy metal ions was examined. At the optimum pH of 5.0, all metal ions were quantitatively sorbed onto the proposed solid phase and completely desorbed with 8?mL of 5.0?mol?L?1 HNO3. The detection limit of Cu2+, Co2+, Ni2+, Pb2+, Fe2+, and Zn2+ ions was 1.7, 2.4, 2.3, 2.9, 2.8, and 1.4?µg?L?1, while the preconcentration factor was 63 for Cu2+ and 94 for the other metal ions and relative standard deviations between 1.8 less than 3.0%. The proposed procedure was applied for the analysis of various samples.  相似文献   

17.
Chromium compounds have received considerable attention because these are used extensively in such industrial applications as electroplating, steelmaking, tanning of leather goods, and corrosion inhibition. The use of supported liquid membranes (SLMs) to remove metals from wastewaters has actively been pursued by the scientific and industrial community. In the present work, the selective separation and preconcentration of Cr(VI) ions has been studied by using a commercial amine as the membrane liquid on the porous polypropylene support. Permeation experiments were conducted on a laboratory scale batch reactor made up of perspex, with a memberane fixed amid the two chambers. The flux of Cr(VI) ions was found to be maximum (3.15?×?10?5?mol?cm?2?s?1) around pH 1. Above and below this pH the flux decreases. Distribution studies show that an increase in the amine concentration leads to higher distribution coefficients at fixed pH values. At pH around unity, the distribution of Cr(VI) ions into the organic phase was found to be maximum, of the order of 56.3. The Cr(VI) transport through the membrane increases with rise in temperature. In order to check the long-term efficiency of the flat sheet SLM, an experiment was conducted with higher Cr(VI) concentration (5000?ppm) for 24?h, at optimised parameters. It was observed that in 24?h, about 1/5th of the feed Cr(VI) is left over while the rest is transported. However, minute organic droplets were also seen in the feed and strip compartments, after 1 day. This observation suggested the loss of membrane liquid. The feasibility of preconcentration of Cr(VI) by using the proposed SLM parameters, was also studied by using the hollow fibre (HF) system. Highest enrichment factor (E.F) value was obtained for 50?mg?L?1 whereby all of the metal was transported to the stripping phase and the resulting Cr concentration was 688?mg?L?1 (E.F?=?13.8). It was observed that while treating more diluted solutions, the enrichment factor decreases. The values of E.F equal to 8.9 and 11.3 were found for initial Cr concentration of 10 and 30?mg?L?1.  相似文献   

18.
Removal of Cu2+, Cd2+, Pb2+, and Zn2+ from aqueous solutions by activated carbon prepared from stems and seed hulls of Cicer arietinum, an agricultural solid waste, has been studied. The influence of various parameters, such as pH, contact time, adsorbent dose, and initial concentration of metal ions on removal was evaluated. The activated carbon was characterized by FT-IR spectroscopy, X-ray diffraction, and elemental analysis. Sorption isotherms were studied using Langmuir and Freundlich isotherm models. All experimental sorption data were fitted to the sorption models using nonlinear least-squares regression. The maximum adsorption capacity values for activated carbon prepared from Cicer arietinum waste for metal ions were 18 mg g?1 (Cu2+), 18 mg g?1 (Cd2+), 20 mg g?1 (Pb2+), and 20 mg g?1 (Zn2+), respectively. The Freundlich isotherm model fit was best, followed by the pseudo-second-order kinetic model. Desorption studies were carried out with dilute hydrochloric acid for quantitative recovery of the metal ions and for regeneration of the adsorbent.  相似文献   

19.
Poly(vinylidene fluoride) (PVDF)/titanium dioxide (TiO2) hybrid membranes were prepared using nano-TiO2 as the modifier, and characterized by Transmission Electron Microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), atomic force microscope (AFM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The characterization results demonstrated that nano-sized TiO2 particles dispersed homogeneously within the PVDF matrix, contributing to more hydroxyls and smoother surfaces. Moreover, permeate flux, retention factor, porosity, contact angle and anti-fouling tests were carried out to evaluate the effect of TiO2 concentration on the performance of PVDF membranes. Among all the prepared membranes, PVDF/TiO2 membrane containing 10 vol.% TiO2 exhibited the best hydrophilicity with an average pure water flux up to 237 L·m?2·h?1, higher than that of unmodified PVDF membranes (155 L·m?2·h?1). Besides, the bovine serum albumin rejection of the hybrid membrane was improved evidently from 52.3% to 70.6%, and the contact angle was significantly lowered from 83° to 60°, while the average pore size and its distribution became smaller and narrower.  相似文献   

20.
Quality of groundwater in the Yarmouk basin, Jordan has been assessed through the study of hydrogeochemical characteristics and the water chemistry as it is considered the main source for drinking and agriculture activities in the region. The results of the relationship between Ca2+ + Mg2+ versus HCO3? + CO32?, Ca2+ + Mg2+ versus total cations, Na+ + K+ versus total cations, Cl? + SO42? versus Na+ + K+, Na+ versus Cl?, Na+ versus HCO3? + CO32?, Na+ versus Ca2+, and Na+: Cl? versus EC describe the mineral dissolution mechanism through the strong relationship between water with rocks in alkaline conditions with the release of Ca2+, Mg2+, Na+, K+, HCO3?, CO32?, SO42?, and F? ions in the groundwater for enrichment. Furthermore, evaporation processes, groundwater depletion, and ion exchange contribute to the increased concentration of Na+ and Cl? ions in groundwater. Anthropogenic sources are one of the main reasons for contamination of groundwater in the study area and for increasing the concentration of Mg2+, Na+, Cl?, SO42?, and NO3? ions. Results show the quality of groundwater in the study area is categorized as follows: HCO3? + CO32? > Cl? > SO42? > NO3? > F? and Na+ > Ca2+ > Mg2+ > K+. In conclusion, the results of TDS, TH, and chemical composition showed that 26% of the groundwater samples were unsuitable for drinking. About 28% of groundwater samples in the study area have a high concentration of Mg2+, Na+, and NO3? above the acceptable limit. Also, based on high SAR, 10% of the groundwater samples were not suitable for irrigation purposes.  相似文献   

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