Initial Zn Concentration Research Articles

Zinc extraction with Ionquest 801 using pseudo-emulsion based hollow fibre strip dispersion technique

The transport of zinc from sulphate solutions using pseudo-emulsion based hollow fibre strip dispersion technique was investigated. The reagent Ionquest 801 was used as an extractant in most experiments. The influence of several parameters like the flow rates, the initial concentration of Zn(II), the extractant amount, the pH, the volume ratio of feed to strippant, and the presence of Ca(II) in the feed phase was studied. A few tests with the extractants Cyanex 272 and DEHPA were also carried out for comparison. Equilibrium data of zinc and calcium extraction were obtained. The analysis of zinc transport was made on the basis of the overall mass transfer coefficient of permeation. This coefficient was also estimated by applying the resistance in series approach, the contribution of each resistance to the overall resistance to mass transfer being evaluated.

Biosorption potential of cocoa pod husk for the removal of Zn(II) from aqueous phase

The potential of cocoa pod husk (CPH) as a biosorbent for the removal of Zn(II) from aqueous solution in a batch system was studied. The effects of contact time, initial concentration of Zn(II), temperature, pH and presence of other metal ions were investigated. The biosorption was relatively fast at 30 °C and followed the Avrami kinetic model. The biosorption isotherm modeling showed that the equilibrium data fitted better to the Freundlich than the Langmuir model. The biosorption showed a pH dependent profile and optimum values at pH 6. Binary metal system experiments showed that the presence of coions had adverse effect on the biosorption capacity of CPH for Zn(II). The thermodynamic parameters indicated that the biosorption of Zn(II) on CPH was a spontaneous and endothermic process. High biosorption capacity obtained shows that CPH may be useful for the removal of Zn(II) from aqueous media.

Removal of Zn(II) ions from aqueous solutions by ethyl xanthate impregnated activated carbons

A coconut shell based granular activated carbon (AC) was aged in solutions containing different amount of potassium ethyl xanthate (PEX) for 24h and then separated from the solutions, rinsed with distilled several times and used for Zn(II) ion removal. It was shown that the loading capacity of PEX impregnated AC at an initial Zn(II) concentration of 112mg/L slightly increased by increasing PEX preloading, so that it increases from 1.56 to 1.88mg/g by increasing the PEX concentration in the aging solution from zero to 200mg/L.Aging of AC in 0.1N sodium hydroxide solutions containing different amounts of PEX was also performed for 24h and it was shown that the loading capacity of the resultant AC samples for Zn(II) ions at an initial Zn(II) concentration of 112mg/L slightly increased by increasing PEX loading, so that it increases from 7.18 to 8.06mg/g by increasing PEX concentration in aging solution from zero to 600mg/L.Aging of nitric acid oxidized AC in 0.1N sodium hydroxide solutions containing different amounts of PEX also performed for 24h. It was shown that the loading capacity of these modified AC samples for Zn(II) ions at an initial Zn(II) concentration of 112mg/L increased by increasing PEX loading, so that it increases from 15.11 to 16.43mg/g by increasing PEX concentration in aging solution from zero to 1000mg/L.It was revealed that the impregnation of AC samples with PEX results in the decreasing of adsorption kinetics of Zn(II) ions, since the hydrophobic nature of PEX molecules retards solution diffusion onto PEX impregnated AC samples.In order to get the highest Zn(II) loading capacity, the optimum condition for surface modification was determined to be oxidizing of AC with 4M nitric acid solution and then aging in 0.1M sodium hydroxide solution containing 661mg/L PEX for 24h. These surface modified activated carbons were named ACABPEX. The effect of Zn(II) initial concentration in the range of 59 to 165mg/L on its adsorption kinetics and loading capacity onto ACABPEX was investigated. The equilibrium and kinetic data were best represented by the Koble–Corrigan isotherm model and the pseudo second order kinetic model, respectively. It was understood that three mechanisms play main roles in the adsorption of Zn(II) onto ACABPEX.

Investigation of mutual interactions of physicochemical parameters on simultaneous Zn(II) bioaccumulation and lipase production of R. delemar

In this study, while Rhizopus delemar removes Zn(II) ions in the wastewater with the help of bioaccumulation mechanisms, the effects of increasing concentrations of Zn(II) ions both on micro-organism growth and lipase enzyme production which biodegrades lipids were investigated. The parameters which affect micro-organism growth, lipid biosynthesis, and Zn(II) bioaccumulation were determined as pH, temperature, and initial Zn(II) ion concentration. In single factor experiments, pH and temperature were studied in the ranges of 5.0–8.0 and 25–35°C, respectively, while initial Zn(II) ion concentration was changed between 5 and 200 mg/L. At pH 5.0, and temperature 35°C, maximum Zn(II) removal was obtained as 26.31 mg/L in the bioaccumulation medium containing 30 mg/L Zn(II) initially. The lipase activities and micro-organism concentrations obtained in Zn(II)-free and the preceding media were 656 and 537 U/L, 1.16 and 0.82 g/L, respectively. When the biomass concentration was kept constant at a required level, in order to maximize the bioaccumulation of Zn(II) and lipase biosynthesis, a statistical experimental design was applied. Maximum Zn(II) bioaccumulation was obtained as 32.38 mg/L at pH 6.8, 33.8°C and 41 mg/L initial Zn(II) concentration. At this optimum point, it was determined that lipase activity is 586 U/L and micro-organism concentration is 0.62 g/L.

Uptake of Zn2+ from dilute aqueous solutions using protonated dry alginate beads

The uptake of zinc ions from dilute aqueous solutions was studied at 25°C using protonated dry alginate beads (PDAB) of around 1 mm in diameter. The Zn2+ uptake increases with the pH of the Zn bearing solution, reaching a value of around 90 mg of Zn per gram of beads (dry weight) at pH 4·5. For an initial Zn concentration as low as 10 mg L−1, the removal reached was complete.The mechanism of Zn uptake was found to be ion exchange between zinc ions and protons form the functional groups of the beads, which followed a pseudo-second order kinetic behaviour. In equilibrium condition the experimental data followed the Langmuir adsorption model.The maximum uptake reached were around 145 and 165 mg g−1 at pH values of 3·5 and 4·5, respectively, which is higher than most of the sorbents used for zinc removal. EPMA-EDX analysis shows that the functional groups of the PDAB were homogeneously distributed during preparation of beads, and that zinc ions were able to reach functional groups in the entire structure of the beads without a concentration gradient across the beads.On a étudié le changement d′ions de le Zinc depuis des solutions aqueuses diluées à 25°C en utilisant des sphères protonadas sèches d′alginatos (PDAB) d′autour de 1 mm de diamètre. Le changement de Zn2+ augmente avec le pH de la solution, en atteignant une valeur d′autour de 90 mg de Zn par gramme de sphères (un poids sec) à un pH 4.5. Pour un concetración initial de Zn plus bas que 10 mg L−1, le changement à court d'argent a été complet. Le mécanisme de changement de Zn est été par un échange ionique entre des ions de zinc et protones provenants depuis les groupes fonctionnels des sphères, qui a un comportement cinétique du pseudo-deuxième ordre. Dans des conditions d′équilibre, les données expérimentales suivent un modèle d′adsorpcin de Langmuir. Le changement maximal à court d′argent a été de 145 et 165 mg g−1 aux valeurs de pH de 3.5 et 4.5, respectivement, où elles ont été plus hautes que les sorbentes utilisés pour le changement de Zn. Des analyses par EPMA-EDX ont montré que les groupes fonctionnels du PDAB ont été distribués de façon homogène durant la préparation des sphères, et que les ions de zinc ont été capables d′atteindre les groupes fonctionnels dans toute la structure des sphères sans une pente de concentration à travers des sphères.

Extraction of Heavy Metals from Contaminated Soil by Two Amaranthus spp.

Two medicinal species of amaranth, Amaranthus viridis L. and A. caudatus L. were evaluated for their ability to uptake heavy metals from a contaminated soil. Twenty healthy plants of each species were transplanted to plastic pots containing the soil contaminated with elevated concentrations of Cd, Cr, Cu, Ni, Pb, and Zn. The plants were harvested after 45 days. Below‐ and above‐ground tissues (roots and shoots) were analyzed separately to determine metals concentrations. Compared with the control group, the effects of S,S‐ethylenediaminedisuccinic acid (S,S‐EDDS) on the uptake of Cd, Cr, Cu, Ni, Pb, and Zn by two medicinal plants were also investigated. The initial contaminant concentrations of Cd, Cr, Cu, Ni, Pb, and Zn in soil were 2.34, 30.53, 16.14, 20.99, 35.77, and 102.31 mg/kg, respectively. The results of metal accumulation with EDDS application showed that EDDS was more efficient at solubilizing Cu and Zn than the control group. Translocation of metals from roots to shoots was most pronounced for Cu and Zn. The only metal that did not result in a transfer factor (TF) ≥0.3 for at least one of the two test species was Pb. The enrichment factor (E) was also low for Pb. The lower TF and E for Pb illustrated the tendency of that metal to remain bound to soil particles and not transfer into plant tissues. These data suggest that these two medicinal species of Amaranthus could be hyperaccumulators of several of these metals, and were particularly effective in accumulating Zn and Cu. Pb and Cd, while accumulated in measurable amounts, did not decrease significantly in the soil, suggesting these species may not be the best choice for plants to be used when bioremediating Pb‐ or Cd‐contaminated areas.

Phytoaccumulation of zinc using the duckweed Lemna gibba L.: effect of temperature, pH and metal source

The use of aquatic plants in the removal of pollutants is an alternative technique for the remediation of contaminated waters. In this work, the capacity of accumulation of soluble Zn by the duckweed Lemna gibba L. native to a Mediterranean area (North-east Algeria) was studied under controlled conditions. The effect of temperature (17, 21, 25 and 29°C), medium pH (3, 4, 5 and 6) and Zn source (ZnSO4, Zn(NO3)2 and ZnCl2) was investigated in order to assess the ability of the plants to remove metal pollutant under various conditions. The results revealed that, at 21, 25 and 29°C, the plants reduced initial Zn concentration (∼18 mg L-1) to 4.64, 1.69 and 1.92 mg L-1, respectively, with 9.1–22.1 mg g-1 DW of Zn accumulated in the biomass. Low Zn accumulation in L. gibba biomass (7.5 mg g-1 DW) corresponding to a low plant growth was observed at pH 3 and 4 indicating that this species is not tolerant to water acidity. A very low Zn concentration in Lemna biomass (1.04 mg g-1 DW) was observed when Zn(NO3)2 was used as Zn source. The results obtained in this study demonstrated that temperature ⩾ 21°C and pH values of 5 and 6 are favourable factors for the phytoaccumulation of Zn by L. gibba L.

Characterization of coconut shell-based activated carbon and its application in the removal of Zn(II) from its aqueous solution by adsorption

AbstractAdsorption kinetics and loading capacity of Zn(II) onto a coconut shell-based activated carbon (AC) was investigated at different solution concentrations, pH values, and temperatures. Characterization of the AC was performed by using scanning electron microscopy, N2 adsorption and desorption isotherms, pore size distribution, surface area determination, determination of point of zero charge (pHPZC), and Boehm titration. The equilibrium studies showed that the Zn(II) adsorption onto the AC increases from 1.98 to 4.24 mg/g by increasing the initial Zn(II) concentration from 23 to 148 mg/L. The kinetic experiments revealed that the initial adsorption rate of Zn(II) is rapid and decreased afterwards. The adsorption rate significantly increased with raising the temperature from 25 to 45°C. The activation energy for the adsorption of Zn(II) ions onto the AC was 54.23 kJ/mol. Both of the adsorption kinetics and loading capacity decreased with increasing the acidity of solution. The results of Boehm titra...

Biosorption of Zn(II) from aqueous solutions by Acinetobacter sp. isolated from petroleum spilled soil

In this study, biosorption of Zn(II) from aqueous solutions by Acinetobacter sp. was investigated in batch experiments. Effects of pH, bacterial dosage, initial Zn(II) concentration, contact time and temperature were studied. Optimum biosorption conditions were found to be initial pH of 6, bacterial dosage of 0.5g/l and initial Zn(II) ion concentration of 100mg/l at room temperature and contact time of 90min. The maximum uptake capacity of Acinetobacter sp. for Zn(II) ions was found to be 36mg/g at optimum conditions. The adjusted R squared for the first-order kinetic model was 0.999. The Langmuir and Freundlich isotherms were also studied and data were better fitted with the Freundlich isotherm. Finally, Acinetobacter sp. adsorption capacity was compared with other biosorbents. This biomass could be used for removal of Zn(II) from wastewater.

Isotherm and thermodynamic studies of Zn (II) adsorption on lignite and coconut shell-based activated carbon fiber

The Zn (II) adsorption capacity of lignite and coconut shell-based activated carbon fiber (ACF) was evaluated as a function of initial Zn (II) concentration, temperature and contact time in batch adsorption process in this study. Adsorption uptake increased with initial Zn (II) concentration and temperature. Optimal contact time for the adsorption of Zn (II) ions onto lignite and coconut shell-based ACF was found to be 50min. Removal percentage decreased from 88.0% to 78.54% with the increment in initial Zn (II) concentration from 5 to 50mgL−1. Equilibrium data fit well with Langmuir-I isotherm indicating homogeneous monolayer coverage of Zn (II) ions on the adsorbent surface. Maximum monolayer adsorption capacity of Zn (II) ions on ACF was found to be 9.43mgg−1. Surface morphology and functionality of ACF prior to and after adsorption were characterized by electron microscopy and infrared spectroscopy. Various thermodynamic parameters such as standard Gibbs free energy (ΔG°), standard enthalpy (ΔH°), and standard entropy (ΔS°) were evaluated.

Metal Adsorbent Prepared from Coir Pith as Agricultural Waste: Adsorption of Zn(II) and Pb(II) from Aqueous Solution

Adsorption of Zn(II) and Pb(II) from aqueous solution were studied by using modified coir pith as an adsorbent. The extended adsorption conditions were investigated as a function of calcination temperature, contact time, adsorbent size, initial pH of solution and initial Zn(II) and Pb(II) concentrations. The adsorption capacity increased rapidly in first 5 minute and reached equilibrium in 120 minutes for Zn(II) and 10 minutes for Pb(II). In case of Zn(II); the results showed that the calcination temperature of modified coir pith above 600oC gave the higher adsorption capacity. The sizes of modified coir pith have no effect on the adsorption capacity. The adsorption capacity increased with increasing initial solution pH value. In case of Pb(II); the calcination temperature of modified coir pith showed no effect on the adsorption capacity. The sizes of modified coir pith showed a little effect on the adsorption capacity. The adsorption capacity increased with increasing of initial solution pH value up to pH of 3 and then stable. The results also corresponded with the Langmuir and Freundlich isotherms and pseudo second order kinetic adsorption models. The modified coir pith gave a higher Zn(II) and Pb(II) adsorption capacity of 29.33 mg Zn(II)/g adsorbent and 36.50 mg Pb(II)/g adsorbent, respectively.

Application of full factorial design to study the simultaneous removal of copper and zinc from aqueous solution by liquid–liquid extraction

The aim of this study is to investigate the zinc and copper removal by liquid–liquid extraction using a statistical method. The study is carried out in two steps: (1) the preliminary extraction tests are performed in order to identify the adequate operational conditions, such as the equilibrium time (=15 min) and the pH range (4.5–6.5). (2) A full factorial design at two levels is applied; the effects of the initial solution pH, the initial concentration of metals, the concentration of extractant, the type of initial solution (sulphate or chloride) and the stirring rate on the removal of each heavy metal are investigated. A first-order-polynomial equation is established. The analysis of variance (ANOVA) method is applied to determine the significant level of the main and interaction effects. The initial concentration of Zn is the most influential parameter on the extraction yield and the concentration of extractant. Di-2-ethylhexyl phosphoric acid is the most used one for the Cu(II) extraction yield. The coefficients of determination, calculated for statistical models obtained, are R2 = 0.908 and R2 = 0.814, respectively, for Zn and Cu and their p-values are 2.26E-07 and 9.01E-07. The interaction graphs have provided valuable information on the interactions factors for each model.

Removal of Zinc from Aqueous Solutions by Magnetite Silica Core‐Shell Nanoparticles

Magnetite silica core‐shell nanoparticles (Fe3O4‐SiO2) were synthesized and evaluated as a nanoadsorbent for removing Zn(II) from aqueous solutions. The core‐shell nanoparticles were prepared by combining coprecipitation and sol‐gel methods. Nanoparticles were characterized by X‐ray diffraction, transmission electron microscopy (TEM), and FT‐IR. The magnetization values of nanoparticles were measured with vibrating sample magnetometer (VSM). The adsorption of Zn(II) ions was examined by batch equilibrium technique. The effects of pH, initial Zn(II) concentration, and contact time on the efficiency of Zn(II) removal were studied. The equilibrium data, analyzed by using Langmuir and Freundlich isotherm models, showed better agreement with the former model. Using the Langmuir isotherm model, maximum capacity of the nanoadsorbent for Zn(II) was found to be 119 mg g−1 at room temperature. Kinetic studies were conducted and the resulting data were analyzed using first‐ and second‐order equations; pseudo‐second‐order kinetic equation was found to provide the best correlation. The adsorption and sedimentation times were very low. The nanoadsorbent can be easily separated from aqueous solution by a magnet. Repeated adsorption acid regeneration cycles were performed to examine the stability and reusability of the nanoadsorbent. The result of this study proved high stability and reusability of Fe3O4‐SiO2 as an adsorbent for Zn(II) ions.

Structure and Composition of ZnxCd1–xS Films Synthesized through Chemical Bath Deposition

Zinc cadmium sulfide (ZnxCd1-xS) thin films grown through chemical bath deposition are used in chalcopyrite solar cells as the buffer layer between the n-type zinc oxide and the p-type light absorbing chalcopyrite film. To optimize energetic band alignment and optical absorption, advanced solar cell architectures require the ability to manipulate x as a function of distance from the absorber-ZnCdS interface. Herein, we investigate the fundamental factors that govern the evolution of the composition as a function of depth in the film. By changing the initial concentrations of Zn and Cd salts in the bath, the entire range of overall compositions ranging from primarily cubic ZnS to primarily hexagonal CdS could be deposited. However, films are inhomogeneous and x varies significantly as function of distance from the film-substrate interface. Films with high overall Zn concentration (x > 0.5) exhibit a Cd-rich layer near the film-substrate interface because Cd is more reactive than Zn. This layer is typically beneath a nearly pure ZnS film that forms after the Cd-rich layers are deposited and Cd is depleted in the bath. In films with high overall Cd concentration (x < 0.5) the Zn concentration rises towards the film's surface. Fortunately, these gradients are favorable for solar cells based on low band gap chalcopyrite films.

Adsorption of Zn(II) on dialdehyde m-phenylenediamine starch

A new chelating material dialdehyde m-phenylenediamine starch (DASMPA) was synthesized by reacting m-phenylenediamine with dialdehyde starch. The obtained material was characterized by element analysis and Fourier transform infrared (FT-IR) spectra. The FT-IR of DASMPA showed an absorption peak at 1605.95 cm(-1) indicating the formation of a Schiff base (C=N). Adsorption activity of DASMPA for Zn(2+) was also investigated in terms of contact time, pH, the initial Zn(II) concentration and temperature, the results revealed that pH = 5, t = 1 h were the optimal conditions. With the degree of substitution (DS) of the DASMPA increased, the adsorption capacity increased gradually. The adsorption equilibrium data correlated well with Freundlich isotherm. Moreover, lower temperature was preferable for the process as it was exothermic.

Kinetics, Mechanistic and Thermodynamics of Zn(II) Ion Sorption: A Modeling Approach

AbstractBiosorption potential of Cedrus deodara sawdust (CDS) in terms of sorption of Zn(II) ion across liquid phase has been evaluated in the present investigation. The surface of the CDS biomass before the sorption of Zn(II) ions seemed to be more porous, non‐crystalline and heterogeneous. The maximum uptake capacity of CDS was 97.39 mg g−1. Sorption of Zn(II) ion on the surface of CDS sawdust was maximum at pH 5, temperature 45°C, initial concentration of Zn(II) ion 100 mg L−1, biomass dose 1 g L−1, contact time 150 min, and agitation rate 160 rpm. Pseudo second‐order kinetics with the highest linear regression coefficient (R2 = 0.99), and lowest values of error functions, i.e., chi (χ2) and sum of square errors (SSE) against pseudo first‐order rate kinetics showed that the sorption of Zn(II) ion on the surface of CDS was mediated by chemosoprtive forces of attraction rather than physical adsorption. Mechanistically, relatively higher proportion of sorption of Zn(II) ion in early phase of contact time was profoundly explained by Bangham's equation and film diffusivity (Df). Intraparticle or pore diffusion (Dp) of Zn(II) ion inside the pores of CDS was rate limiting step at the later stage of contact time. Furthermore, the thermodynamic study on sorption of metal ion delineated the fact that the Zn(II) sorption on the surface of CDS was spontaneous, endothermic together with increased entropy at solid liquid interface.

Uptake of Zn, Cu, Pb, and Cd by water hyacinth in the initial stage of water system remediation

The removal efficiency of water hyacinth for Zn, Cu, Pb and Cd after their entry into an undisturbed fresh water body was studied using minicosms placed within a reservoir. Variable parameters were water pH (6 or 8), single or multi-metal additions, and the plant biomass. The initial concentrations of Zn, Cu, Pb and Cd in water (500, 250, 250 and 50 μg/L, respectively) quickly decreased in the order Pb ≈ Cu ≫ Cd ≈ Zn in the first days. Metal removal was more efficient at pH 8 than at pH 6, and it was only slightly higher for single metals compared to multi-metal additions. After 8 days the remaining amounts of metals relative to their initial concentrations for multi-metal pollution treatments were 8% and 24% (Cu), 11% and 26% (Pb), 24% and 50% (Cd), and 18% and 57% (Zn) at pH 8 and pH 6, respectively. Increasing plant biomass promoted faster metal removal. The bioconcentration factor (the ratio of the metal concentration in whole plants to the initial metal concentration in water) exceeds 2000 for all metals (with the exception of Zn and Cd at pH 6). It was concluded that the water hyacinth can be successfully used for fast removal of metals in the initial stage of water body remediation.

Sorption of Zn(II) and Pb(II) ions in the presence of the biodegradable complexing agent of a new generation

The macroporous chelating ion exchangers containing different functional groups i.e. Purolite S-920, Purolite S-930 and Lewatit TP-208 have been used in the sorption process of Zn(II) and Pb(II) ions. The effect of the presence of biodegradable, environmentally friendly aminopolycarboxylate chelating agent, trisodium salt of methylglycinediacetic acid (MGDA) on its sorption capacity was also examined. The investigations were carried out by the static method. Besides the effect of initial concentration of Zn(II) and Pb(II) and the complexing agent the research concerns the influence of solution pH, phase contact time on effectiveness of sorption. The equilibrium and kinetics of Zn(II)–MGDA and Pb(II)–MGDA complexes sorption were obtained and fitted using the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich (D–R) models as well as the pseudo first and pseudo second order kinetic models. The intraparticle diffusion model was also used. The results showed that the sorption processes of Zn(II) and Pb(II) complexes with MGDA on Purolite S-920, Purolite S-930 and Lewatit TP-208 followed well the pseudo second order kinetics.

Divalent zinc removal from aqueous solutions by adsorption on magnetite nanoparticles: kinetics and isotherm

Magnetite nanoparticles were applied to remove Zn(II) from aqueous solutions in batch systems. Rate experiments were performed at various initial Zn(II) concentrations (1 and 4 mmol/L), adsorbent concentration (2.5, 5 and 10 g/L) and particle size (10 and 20 nm). The experimental data were analysed using several kinetic equations to determine the best-fit equation and related parameters were calculated. The adsorption process followed the Elovich equation and the Fractional power equation. The adsorption process was found to strongly be pH dependent. The adsorption data fitted with Freundlich and Langmuir isotherm equations and the isothermal constants were evaluated.

Accumulation and translocation of heavy metals in the canola (Brassica napus L.)—soil system in Yangtze River Delta, China

Concentrations of heavy metals such as Cd, As, Hg, Pb, Cr, Cu, Zn and Ni in different tissues (seeds, roots and shoots) of the mature canola (Brassica napus L.) plants and in the associated rhizosphere soils from Yangtze River Delta (YRD) region of China, were determined to evaluate the heavy metals’ pollution in the soils and the canola seeds, and to discuss their accumulation and translocation characteristics in canola plants. At the same time, the phytoextraction potential of the canola plant for the above heavy metals was theoretically calculated and discussed on the basis of above measured data. The results showed that the concentration ranges of Cd, As, Hg, Pb, Cr, Cu, Zn and Ni in the rhizosphere soils were 0.115–0.481, 3.40–20.5, 0.069–0.682, 9.92–27.4, 46.8–86.6, 17.7–253.3, 65.2–511.7 and 16.0–37.8 mg kg−1, respectively. The concentrations of Cu, Zn and Hg at some sampling sites exceeded the 2nd grade threshods of Chinese national environmental quality standard for soils. The potential ecological risk of heavy metals in the canola rhizosphere soils decreased in the order of Zhejiang > Shanghai > Jiangsu provinces. The concentration ranges of above heavy metals in the canola seeds were 0.032–0.067, 0.002–0.005, 0.001–0.005, 0.053–0.165, 0.191–0.855, 3.01–13.20, 34.82–96.95 and 0.343–2.86 mg kg−1, respectively, with Cu and Zn at some sampling sites exceeding the permissible concentrations in foods of China. Heavy metals’ concentrations in canola seeds didn’t increase with their increasing concentrations in the rhizosphere soils. The bioconcentration factors (BCFs) of most heavy metals in the canola seeds decreased with their increasing concentrations in the associated rhizosphere soils. The average BCFs of heavy metals decreased in the order of Zn (0.488)>Cd (0.241)>Cu (0.145)>Ni (0.038)>Hg (0.021)>Pb (0.005)=Cr (0.005)>As (0.000) in the canola seeds, Cd (1.550)>Cu (0.595)>Zn (0.422)>Hg (0.138)>Ni (0.085)>Pb (0.080)>As (0.035)>Cr (0.031) in the roots, and Cd (0.846)>Zn (0.242)>Cu (0.205)>Hg (0.159)>Ni (0.031)>Pb (0.025)>As (0.012)>Cr (0.007) in the shoots, respectively. The accumulation capacity for most of the above heavy metals in the mature canola tissues was root > shoot > seed, with the exceptions of seed > root > shoot for Zn and shoot > root > seed for Hg. Except Hg from root to shoot and Zn from root to seed, translocation factors (TFs) of above heavy metals were lower than 1.0. The concentrations, BCFs and TFs of above heavy metals in the canola tissues indicated that the investigated canola plants did not meet the criteria of hyperaccumulators for the above heavy metals. The phytoextracton potential of the studied canola plants for the above heavy metals from the polluted soils was very limited. It would take 920, 3,170 and 3,762 years (assuming two crops per year) to reduce the initial soil Zn, Cu and Hg concentrations, respectively, from the most polluted soil concentrations to the 2nd grade thresholds of Chinese national environmental quality standard for soils.