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1.
Several aquatic environments have been contaminated with heavy metals dumped via industrial effluents. Numerous studies have
been published regarding the removal of single metals from aqueous solutions by microalgal biomass. However, such studies
do not reflect the actual problem associated with industrial effluents because usually more than one metal species is present.
Here we studied the biosorption capacity of Zn 2+ and Cd 2+ as single- and binary-metal systems by two microalgae, Scenedesmus obliquus and Desmodesmus pleiomorphus, isolated from a polluted site in Northern Portugal. For each metal independently, D. pleiomorphus showed a higher metal sorption capacity than S. obliquus, at concentrations ranging from 60 to 300 mg/l (except 150 mg Cd/l). Maximum amounts of Zn 2+ and Cd 2+ removed were 22.3 and 60.8 mg/g by S. obliquus, and 83.1 and 58.6 mg/g by D. pleiomorphus. In binary-metal solutions, S. obliquus was in general able to remove Zn 2+ to higher extents than Cd 2+, whereas the opposite was observed with D. pleiomorphus. The simultaneous uptake of Zn 2+ and Cd 2+ by both microalgae was considerably lower than that of their single-metal counterparts, at equivalent concentrations. Although
microalgal uptake from binary-metal solutions was lower than from single-metal ones, the wild microalgae selected were able
to efficiently take up mixtures of Zn 2+ and Cd 2+ up to 300 mg/l of both metals—thus materializing a promising bioremediation vector for polluted waters. 相似文献
2.
Water-dissolved oxygen was supplied into anaerobic aquifer , which oxidized Fe(II), Mn(II) and trivalent arsenic and changed
them into undissolved solid matter through hydrolysis, precipitation, co-precipitation and adsorption processes. The experiment
was carried out on the column imitated a bore core of anaerobic aquifer with water phase containing Fe(II), Mn(II), As(III)
concentration of 45.12 mg/L, 14.52 mg/L, 219.4 μg/L, respectively and other ions similarly composition in groundwater. After
6 days of air supply, concentration of iron reduced to 0.38 mg/L, manganese to 0.4 mg/L, arsenic to 9.8 μg/L (equivalent 99.16%
of iron, 97.25% of manganese and 95.53% of arsenic fixed), and for other ions, the concentration changed almost according
to general principles. Ion phosphate and silicate strongly influenced on arsenic removal but supported iron and manganese
precipitation from water phase. Based on the experimental results, new model of groundwater exploitation was proposed. 相似文献
3.
Rice husk (RH) agro-waste was used as a raw material for synthesizing mesoporous molecular sieves, MCM-41. The Fe-MCM-41 was
prepared by the hydrothermal technique (HT), resulting in a higher surface area and crystallinity than when prepared under
ambient conditions. In addition, a hexagonal structure was clearly seen with hydrothermal technique (HT) preparation. The
adsorption of arsenate by HT-Fe-MCM-41 was investigated. The factors studied affecting arsenate adsorption capacity were ferric
content in MCM-41, contact time, pH of solution, and initial arsenate concentration. It was found that HT-Fe-MCM-41 at the
Si/Fe mole ratio of 10 gave the highest adsorption capacity. Arsenate adsorption reached equilibrium within 4 h. The adsorption
capacity of HT-Fe-MCM-41 (Si/Fe = 10) was affected by the initial pH value and the initial arsenate concentration. The adsorption
capacity was highest at pH 3 and decreased thereafter with increases in the pH of solution value. The Langmuir model fit the
arsenate adsorption isotherm well. The maximum adsorption capacity for arsenate was 1,111 μg g −1. 相似文献
4.
The present work describes the removal of Novacron Golden Yellow (NGY) dye from aqueous solutions using peanut hulls. The experiments were performed with native, pretreated and immobilised forms of peanut hulls. The effect of various operational parameters (pH, biosorbent dose, initial dye concentration and temperature etc.) was explored during batch study. NGY showed maximum removal at low pH and low biosorbent dose. High initial dye concentration facilitated the biosorption process. Maximum dye removal with native, pretreated and immobilised biomass was found to be 35.7, 36.4 and 15.02 mg/g respectively. The experimental data were subjected to different kinetic and equilibrium models. The kinetic data confirmed the fitness of pseudo-second-order rate law for NGY biosorption. The equilibrium modelling was carried out by Freundlich, Langmuir and Temkin models. The isothermal data of NGY removal were best described by Freundlich adsorption isotherm. Negative values of Free energy change (Δ G0) for NGY with native and pretreated biomass depicted the spontaneous nature of biosorption process. In column mode, the effects of bed height, flow rate and initial dye concentrations were optimised. Maximum NGY biosorption (7.28 mg/g) was observed with high bed height, low flow rate and high initial concentration in continuous mode. Bohart–Adams model best fitted to the data obtained from column studies. The results indicated that the peanut hulls could be used effectively for the removal of dyes containing wastewater. 相似文献
5.
The use of tree species for phytoremediation of contaminated soil offers the advantage of a large biomass in which to store
contaminants. We investigated the cadmium (Cd) and zinc (Zn) accumulation ability of Evodiopanax innovans, a common deciduous tree species belonging to the Araliaceae family and widely found in secondary forests in Japan. Sampling
was conducted at an old silver mine. Leaf samples were collected from nine tree species, including E. innovans. The seasonal variation of metal concentrations in the leaves and the detailed distribution of metals in the leaves and twigs
of E. innovans were measured. We also analyzed the contents of organic acids in the leaves. The highest concentration of Cd in the leaves
of E. innovans was 118 μg/g, which exceeds the threshold level for being considered a Cd hyperaccumulator (100 μg/g). For Zn, the highest
value was 1040 μg/g in leaves, which is less than required to qualify as a Zn hyperaccumulator. Both Cd and Zn were found
to accumulate in the petioles and veins of leaves and the bark of twigs. Since the oxalic acid content of leaves showed a
weak correlation with Cd concentration, oxalic acid may play an important role in the accumulation of Cd. Taking both the
Cd concentration level and the biomass of this woody plant into consideration, it may be possible to use E. innovans for the phytoremediation of Cd-contaminated soils. 相似文献
6.
This paper reports the application of Box-Behnken experimental design to illustrate the adsorption of direct dyes (Indosol Black NF and Indosol Orange RSN) using polyethyleneimine (PEI)-treated peanut husk biomass. The effect of three independent variables (initial dyes concentration, biosorbent dose and pH) was investigated during the study. Maximum biosorption capacity (141 and 98.2 mg/g) of PEI-pretreated biomass was achieved with 200 mg/L initial dye concentration and 0.05 g/50 mL biomass dose for Indosol Black NF and Indosol Orange RSN, respectively. Acidic pH was found to be favourable for maximum dyes removal. Characterisation of biosorbent was carried out through Fourier transform-infrared spectroscopy (FT-IR), scanning electron microscopy, thermogravimetric analysis (TGA) and point of zero charge determination. FT-IR analyses confirmed the involvement of carboxylic and carbonyl groups. The desorption study was also conducted to check out the possibility of regeneration of dyes and adsorbent and it was found that 51.58 and 76.6% of Indosol Black NF and Indosol Orange RSN, respectively, can be desorbed from the loaded biosorbent by using 1 M NaOH solution. The results indicated that PEI-treated peanut husk biomass can be used as an efficient biosorbent for the removal of Indosol Black NF and Indosol Orange RSN dyes from aqueous solutions. 相似文献
7.
Heavy metal pollution caused by traffic activities is increasingly becoming a great threat to urban environmental quality
and human health. In this paper, soils of Kerman urban and suburban areas were collected to assess the potential effects of
traffic and other vehicle-related pollution by heavy metal accumulation in soils. Eighty-six samples were collected along
streets and from residential and rural sectors, as well as vehicle-related workshops from depth of 0–5 and 15–20 cm and analyzed
by flame atomic absorption spectrometry (FAAS) for heavy metals (Cd, Cr, Cu, Pb, Sn and Zn), as well as major elements (Al,
Ca, Fe and Mn). Several hot-spot areas were identified in the composite geochemical maps produced based on Geographical Information
System (GIS) technology. The majority of the hot-spot areas were identified to be vehicle-related workshops, fuel stations
and road junctions. The most polluted hot-spot in the study area was located in soils close to a car battery processing workshop
in the southwestern part of Kerman city, with concentrations of Cd (0.32 mg/kg), Cr (169 mg/kg), Cu (250 mg/kg), Pb (5,780 mg/kg),
Sn (27.2 mg/kg) and Zn (178 mg/kg) of 1, 8.5, 8.3, 230, 13.5 and 3 times more than the relevant mean concentrations in natural
soils, respectively. Traffic pollution has resulted in significant accumulation of heavy metals in soils and sediments, and
that level of accumulation varied remarkably among elements. Based on X-ray diffraction analysis, most parts of soils and
sediments of the Kerman basement consist of calcite and clay minerals. Abundance of clay minerals and medium to alkaline pH
causes low mobility of heavy metals in soils of Kerman. 相似文献
8.
Wastewater from wash down of boat hulls contains typically Cu, Zn and organometallic biocides, e.g. tributyltin (TBT). In
some cases this wastewater is led directly into the marine system. In the present paper, a cheap flocculation method (iron
flocculants) for removal of Cu and Zn from the wastewater is investigated and the method was shown successful. TBT concentration
in a sample from a German dockyard was also decreased during flocculation, but the TBT removed was already associated with
small particulates in the original sample. Low concentrations of heavy metals were obtained by flocculation: <0.05 mg Cu/l
and 0.2 mg Zn/l.
An erratum to this article can be found at 相似文献
9.
Phosphate removal from aqueous solution was explored using granular ferric hydroxide (GFH) as an inorganic adsorbent. Adsorption,
desorption and kinetic studies were conducted on laboratory scale to evaluate the performance of GFH as an adsorbent for low
concentrations of phosphate solution. The effect of pH on adsorption was investigated, and phosphate uptake was shown to decrease
with an increase in solution pH, with maximum removal seen to occur at pH 3. The experimental data best fit the Temkin isotherm
at both pH 3 and 4. Uptake of phosphate by GFH follows second-order kinetics, with the small particle range (76–200 μm) removing
phosphate from the solution more rapidly than the larger particle range (710–850 μm). The kinetic results suggest that intra-particle
diffusion is an important factor in phosphate adsorption onto GFH. Thermodynamic parameters (Δ G°, Δ H°, Δ S°) were evaluated, and the results indicated that the adsorption process was endothermic and spontaneous. This study demonstrates
that GFH has potential to be used as a cost-effective adsorbent for phosphate removal from aqueous solution. 相似文献
10.
Adsorption of arsenic (V) by natural zeolitic tuff, modified with iron (III), was investigated. Also, the iron (III) adsorption
characteristics by natural zeolitic tuff was evaluated. It was determined that iron (III) adsorption by starting zeolitic
tuff was best represented by the Freundlich type of isotherm, having correlation coefficient ( r
2) of 0.990. Arsenic (V) adsorption by iron (III)-modified zeolitic tuff followed a nonlinear type of isotherm. The best fit
of the experimental data was obtained using the Langmuir–Freundlich model ( r
2 = 0.99), with the estimated maximum of arsenic (V) adsorption to iron (III)-modified zeolitic tuff of 1.55 mg/g. 相似文献
11.
An understanding of road-deposited sediment (RDS) characteristics on an impervious surface is essential to estimate pollutant
washoff characteristics and to minimise the impacts of pollutants on the water environment. A total of 62 RDS samples were
collected from four different land-use types (commercial, residential, intense traffic and riverside park) in Zhenjiang City,
China. The samples were fractionated into seven grain-size classes and analysed for particle size distribution and concentrations
of pollutants. The samples are found to consist predominantly of fine particles (60–80%, <250 μm). The maximum mean concentrations
of zinc, lead and copper were 686.93, 589.19 and 158.16 mg/kg, respectively, with the highest metal concentrations found in
samples from the intense traffic area. The maximum mean contents of organic matter (12.55%), nitrogen (6.31 mg/g) and phosphorus
(5.15 mg/g) were found in samples from the commercial area. The concentrations of heavy metals were highest in the smallest
particle size fraction analysed (63 μm). The organic matter and nitrogen content generally increased with decreasing particle
sizes in the <500-μm particle size range. The results also revealed that most of the total nitrogen (TN) is attached to the
finer sediments and that to effectively reduce TN loads in particulates, treatment facilities must be able to remove the finer
particles (down to 125 μm for TN). 相似文献
12.
以花生壳为生物吸附剂,通过序批式实验研究了吸附剂投量、吸附时间、金属离子初始质量浓度、吸附温度对吸附金属离子的影响,探讨了花生壳吸附的动力学及热力学特性。结果表明,准二级动力学方程能很好地描述花生壳对Pb^2+、Cu^2+、Cr^3+、Cd^2+、Ni^2+的吸附过程。Langmuir模型和Freundlich模型均能较好地描述花生壳对5种重金属离子的等温吸附过程,而Langmuir模型拟合的线性更好。Pb2+、Cu2+、Cr3+、Cd2+、Ni2+5种金属离子的最大吸附量分别是32.25、7.09、3.82、2.95、2.22 mg.g-1,花生壳可用于处理低质量浓度多种重金属混合的废水。热力学研究表明,花生壳对5种金属离子的吸附具有自发、吸热和熵增的特性。 相似文献
13.
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
14.
Addition of alkali to pH 10 is effective for precipitation of precipitable metals. Fenton treatment is effective for substantial removal of Tl, Cd, Cu, Pb, and Zn. Sulfide precipitation is a final step for removal of trace Tl, Cd, Cu, Pb, and Zn. Bench and pilot studies demonstrated the effectiveness of this combined technique. ![]() Thallium (Tl) in industrial wastewater is a public health concern due to its extremely high toxicity. However, there has been limited research regarding Tl removal techniques and engineering practices to date. In this investigation, bench and pilot studies on advanced treatment of industrial wastewater to remove Tl to a trace level were conducted. The treatment process involved a combination of hydroxide precipitation, Fenton oxidation, and sulfide precipitation. While hydroxide precipitation was ineffective for Tl+ removal, it enabled the recovery of approximately 70%–80% of Zn as Zn hydroxide in alkaline conditions. The Fenton process provided good Tl removal (>95%) through oxidation and precipitation. Tl was then removed to trace levels (<1.0 µg/L) via sulfide precipitation. Effective removal of other heavy metals was also achieved, with Cd<13.4 µg/L, Cu<39.6 µg/L, Pb<5.32 µg/L, and Zn<357 µg/L detected in the effluent. X-ray photoelectron spectroscopy indicated that Tl2S precipitate formed due to sulfide precipitation. Other heavy metals were removed via the formation of metal hydroxides during hydroxide precipitation and Fenton treatment, as well as via the formation of metal sulfides during sulfide precipitation. This combined process provides a scalable approach for the in-depth removal of Tl and other heavy metals from industrial wastewater. 相似文献
15.
This study involves the utilisation of peanut husk for the removal of Drimarine Red HF-3D dye from aqueous solutions. Batch study experiments were conducted with native, HNO 3-treated and Na-alginate-immobilised peanut husk biomass. Maximum dye removal (95.24 mg/g) was obtained with HNO 3-treated biomass. The experimental data were successfully explained with a pseudo-second-order kinetic model for all types of biosorbents. The equilibrium data fitted well to the Freundlich adsorption isotherm model. A thermodynamic study was also carried out to check the nature of the adsorption process. A fixed-bed column study for Drimarine Red HF-3D was carried out to optimise the effect of bed height, flow rate and initial dye concentration using peanut husk biomass. The column study showed that biosorption capacity increased with the increase in initial dye concentration and bed height, but decreased with increased flow rate. Data for Drimarine Red HF-3D were in very good agreement with the bed depth service time model. Fourier transform infrared analysis demonstrated the involvement of different functional groups in dye biosorption. These results showed that peanut husk biomass possessed good potential for the removal of Drimarine Red HF-3D from aqueous solution. 相似文献
16.
This report shows that silica sulfate is removing phosphate from wastewater very efficiently. Phosphorus removal and recovery
from wastewater is a worldwide issue due to pollution of natural waters by phosphate and depletion of phosphate ores. Adsorption
is a process that can remove phosphate at low concentrations. Adsorption also allows the recovery of phosphate for possible
re-use. Here, we studied the adsorption of phosphate from wastewater using commercial Zr ferrite, Zr-MCM 41 and silica sulfate.
We calculated equilibrium isotherms, kinetic models and thermodynamic effects under conditions similar to real wastewaters.
We found that the equilibrium data for the adsorption of phosphate were best fitted to the Freundlich model. The results show
that the maximum uptake of phosphate was 3.36 mg g −1 for Zr-MCM, 27.73 mg g −1 for Zr ferrite and 46.32 mg g −1 for silica sulfate. The kinetic results of the three adsorbents were satisfactorily predicted using a pseudo-second-order
model. We found that silica sulfate provided excellent characteristics in terms of the maximum adsorption and rate constant
for the adsorption of phosphate. The thermodynamic data showed that increasing the temperature enhanced the adsorption of
phosphate onto silica sulfate. Our findings will help to define efficient methods to remove phosphate from wastewater. 相似文献
17.
In a multifactorial pot experiment, maize ( Zea mays L.) with or without inoculation with the arbuscular mycorrhizal (AM) fungus Glomus mosseae BEG167 was grown in a sterilized soil spiked with three levels of zinc (0, 300 and 900 mg Zn kg −1 soil) and three levels of cadmium (0, 25 and 100 mg Cd kg −1 soil). At harvest after 8 weeks of growth, the proportion of root length of inoculated plants colonized decreased with increasing Zn or Cd additon, and was 56% in the absence of both metals and was reduced significantly to 27% in the presence of the higher levels of both metals. Mycorrhizal plants had higher biomass than non-mycorrhizal controls except at the highest soil level of Cd. Cadmium had more pronounced effects on plant biomass than did Zn at the levels studied and the two metals showed a significant interaction. The data suggest that mycorrhizal inoculation increased plant growth with enchancement of P nutrition, perhaps increasing plant tolerance to Zn and Cd by a dilution effect. AM inoculation also led to higher soil solution pH after harvest, possibly reducing the availability of the metals for plant uptake, and lowered the concentrations of soluble Zn and Cd in the soil solution, perhaps by adsorption onto the extrametrical mycelium. 相似文献
18.
This study evaluated the feasibility of combining potassium chloride (KCl) leaching and electrokinetic (EK) treatment for the remediation of cadmium (Cd) and other metals from contaminated soils. KCl leaching was compared at three concentrations (0.2%, 0.5%, and 1% KCl). EK treatment was conducted separately to migrate the metals in the topsoil to the subsoil. The combined approach using KCl leaching before or after EK treatment was compared. For the single vertical EK treatment, the removal of Cd, lead (Pb), copper (Cu) and zinc (Zn) from the topsoil (0–20 cm) was 9.38%, 4.80%, 0.95%, and 10.81%, respectively. KCl leaching at 1% KCl removed 84.06% Cd, 9.95% Pb, 4.34% Cu, and 19.93% Zn from the topsoil, with higher removal efficiency than that of the 0.2% and 0.5% KCl leaching treatments. By combining the KCl leaching and EK treatment, the removal efficiency of heavy metals improved, in particular for the 1% KCl + EK treatment, where the removal rate of Cd, Pb, Cu, and Zn from the upper surface soil reached 97.79%, 17.69%, 14.37%, and 41.96%, respectively. Correspondingly, the soil Cd content decreased from 4 to 0.21 mg/kg, and was below the Chinese standard limit of 0.3 mg/kg soil. These results indicate that 1% KCl + EK treatment is a good combination technique to mitigate Cd pollution from contaminated soils used for growing rice and leafy vegetables. 相似文献
19.
An-RBC reactor is highly suited to treat metallic wastewater. Metal removal is due to sulfide precipitation via sulfate reduction by SRB. Cu(II) removal was the best among the different heavy metals. Maximum metal removal is achieved at low metal loading condition. Metal removal matched well with the solubility product values of respective metal sulfide salts. ![]() This study was aimed at investigating the performance of anaerobic rotating biological contactor reactor treating synthetic wastewater containing a mixture of heavy metals under sulfate reducing condition. Statistically valid factorial design of experiments was carried out to understand the dynamics of metal removal using this bioreactor system. Copper removal was maximum (>98%), followed by other heavy metals at their respective low inlet concentrations. Metal loading rates less than 3.7 mg/L?h in case of Cu(II); less than 1.69 mg/L?h for Ni(II), Pb(II), Zn(II), Fe(III) and Cd(II) are favorable to the performance of the An-RBC reactor. Removal efficiency of the heavy metals from mixture depended on the metal species and their inlet loading concentrations. Analysis of metal precipitates formed in the sulfidogenic bioreactor by field emission scanning electron microscopy along with energy dispersive X-ray spectroscopy (FESEM-EDX) confirmed metal sulfide precipitation by SRB. All these results clearly revealed that the attached growth biofilm bioreactor is well suited for heavy metal removal from complex mixture. 相似文献
20.
通过盆栽试验,观察分析不同的土壤改良配方对重金属超积累植物东南景天盆栽土壤中细菌、真菌和放线菌数量、Cmic及Nmic的影响,以此来筛选出最优的促进东南景天修复锌镉污染土壤的改良剂配方。结果显示:细菌、真菌和放线菌数量,与土壤Zn、Cd的去除率、东南景天植株干质量、Cmic及Cmic/Nmic两两之间都呈现极显著正相关关系(但Cmic/Nmic与真菌数量仅呈显著相关)。添加了土壤改良剂后,细菌、放线菌、真菌的数量都有不同程度的增加,其中以细菌数量的增加最为显著,放线菌次之,真菌则对各种土壤处理相对较不敏感;在各种土壤配方中,添加了6 g赤泥、15 g污泥和15 g沸石的T7处理最有利于各类土壤微生物的生长,微生物量碳达到345.64 mg.kg-1,与其它处理之间都达到显著差异。因此,可以利用土壤微生物作为污染土壤改良情况的生物指标。该研究为下阶段研究化学改良剂-植物-微生物修复技术奠定了基础。 相似文献
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