Sorption studies of heavy metal ions on a novel chelating resin and its application in the stripping of mercury (II)

A chelating resin containing a stable thiol group was synthesised, using polystyrene as the starting material. The resin is stable towards conc. HCl, 0.1M HNO(3) and 0.1M NaOH. The resin shows affinity towards Ag(+), Hg(2+), Bi(3+), Pb(2+), Cu(2+), Zn(2+) and Cd(2+). Extraction of these metal ions as a function of pH, kinetics of exchange and breakthrough capacities is evaluated. The selectivity of the resin for the metal ions is in the order Ag(+) > Hg2+ > Cu2+ > Pb2+ > Cd2+ > Zn2+. The equilibrium constants for exchange and kinetics of exchange are favourable for the recovery of mercury from lean sources. Application of the resin in the stripping of mercury from chlor-alkali plant affluent, and in the enrichment of mercury from seawater, have been investigated. Mercury sorbed resin can be regenerated using 5% thiourea in 0.1M HCl.     

Pilot-plant study of wastewater sludge decontamination using a ferrous sulfate bioleaching process.

The objective of this research was to investigate the performance of the ferrous sulfate bioleaching (FSBL) process in a pilot plant for decontamination and stabilization of wastewater sludge. Batch and continuous experiments, conducted with two 4-m3 bioreactors using indigenous iron-oxidizing bacteria (20% v/v of inoculum) with addition of 4.0 g ferrous sulfate heptahydrate per liter of sludge initially acidified to pH 4.0, were sufficient for effective heavy metal (cadmium, copper, manganese, zinc, and lead) removal yields. The average metal removal yields during the FSBL process were as follows: cadmium (69 to 75%), copper (68 to 70%), manganese (72 to 73%), zinc (65 to 66%), and lead (16%). The FSBL process was also found to be effective in removing both fecal and total coliforms (abatement > 5 to 6 log units). The nutrients content (nitrogen, phosphorus, and magnesium) were also preserved in decontaminated sludge.     

Copper and cadmium removal from synthetic industrial wastewater using chitosan and nylon 6

Purpose

Chitosan with nylon 6 membranes was evaluated as adsorbents to remove copper and cadmium ions from synthetic industrial wastewater.

Methods

Chitosan and nylon 6 with glutaraldehyde blend ratio with (1:1+Glu, 1:2+Glu, and 2:1+Glu) have been prepared and these were used as membranes to remove copper and cadmium ions from synthetic industrial wastewater. Characterization of the synthesized membrane has been done with FTIR, XRD, TGA/DTA, DSC, and SEM. Chemical parameters for quantities of adsorption of heavy metal contamination have been done and the kinetics of adsorption has also been carried out.

Results

The optimal pH for the removal of Cd(II) and Cu(II) using chitosan with nylon 6. Maximum removal of the metals was observed at pH 5 for both the metals. The effect of adsorbent dose also has a pronounced effect on the percentage of removal of the metals. Maximum removal of both the metals was observed at 5 g/100 ml of the adsorbent.

Conclusion

Copper and cadmium recovery is parallel at all time. The percentage of removal of copper increased with increase in the pH from 3 to 5. In the case of cadmium containing wastewater, the maximum removal of metal occurred at pH 5. The uptake amount of Cu²⁺ ions on chitosan increased rapidly with increasing contact time from 0 to 360 min and then reaches equilibrium after 360 min; the equilibrium constant for copper and cadmium ions is more or less the same for the adsorption reaction.     

Key factors in chemical reduction by hydrazine for recovery of precious metals

Most of the commonly used metal waste treatment approaches only allow removal of metals which are ultimately discarded as sludge and do not permit the reuse of the metals, resulting in a waste of raw materials. In this study, the recovery of precious metals of sliver and copper in a synthesized wastewater in batch reactors was investigated using a reduction method by hydrazine as the reducing agent. Recovery of metal ions was greatest at pH > 11. The presence of humic acid did not have negative effects on the recovery process. Varying dissolved oxygen levels in the hydrazine solution did not significantly affect the recovery of both metals while seeding and ageing processes resulted in an increase in the particle size of the solid obtained. Under competitive conditions between Cu2+ and Ag+ ions, the recovery of silver remained the same, while that of copper was enhanced.     

浮游球衣菌对Pb2+、Cu2+、Zn2+、Cd2+的吸附性能研究

研究了浮游球衣菌（Sphaerotilus natans）在不同吸附条件下对溶液中Pb^2＋、Cu^2＋、Zn^2＋、Cd^2＋的吸附规律。结果表明,Sphaerotilus natans对这4种重金属离子均有一定的吸附作用,并在20min内达到吸附平衡,pH对吸附过程影响较大,pH为5.5时Sphaerotilus natans对这4种金属离子的吸附效果最好,Sphaerotilus natans对它们的吸附选择性为Pb^2＋〉Cu^2＋〉Zn^2＋〉Cd^2＋,Pb^2＋、Cu^2＋能部分置换出已被菌体吸附的Zn^2＋、Cd^2＋。HCI和EDTA溶液可有效地将金属离子从菌体上解吸下来,解吸后的菌体可重复使用。     

Biosorption of copper(II) by Pseudomonas aeruginosa

The mechanism of accumulation of copper(II) by Pseudomonas aeruginosa was investigated. Uptake consisted of a rapid process (likely to be extracellular binding) followed by a slow phase (possibly cellular uptake). The sorption capacity of the microbe was found to be 50 mg/g, and sorption followed the Langmuir isotherm. The presence of mild mineral acids (0.1 N HCl) led to destructive desorption of 95% of sorbed metal, whereas citrate buffer (pH 4) desorbed 80% of the accumulated metal ions non-destructively. Spectroscopic and microscopic studies indicated the accumulation of metal inside the cell, though the maximum uptake was by the cell wall.     

Investigation of heavy metal accumulation in Polygonum thunbergii for phytoextraction

In this study, cadmium (II), lead (II), copper (II) and zinc (II) were determined in Polygonum thunbergii and soil from the Mankyung River watershed, Korea. Soil samples contained detectable lead (<17.5 g g(-1)), copper (<8.4 g g(-1)) and zinc (<24.5 g g(-1)), whereas cadmium was undetectable. Whole plants of P. thunbergii contained detectable lead (<320.8 g g(-1)), copper (<863.2 g g(-1)) and zinc (<2427.3 g g(-1)), whereas cadmium was detectable only in the stem (<7.4 g g(-1)) and root (<10.1 g g(-1)). Whole plant concentrations were very different for each metal, particularly in the case of zinc. The mean content of heavy metal in the whole plants increased in the order of cadmium (8.5 g g(-1))相似文献   

Copper binding by peat fulvic and humic acids extracted from two horizons of an ombrotrophic peat bog

We studied the binding of Cu(II) to humic acids and fulvic acids extracted from two horizons of an ombrotrophic peat bog by metal titration experiments at pH 4.5, 5.0, 5.5, and 6.0 and 0.1 M KNO3 ionic strength. Free metal ion concentrations in solution were measured using an ion selective electrode. The amounts of base required to maintain constant pH conditions were recorded and used to calculate H+/Cu2+ exchange ratios. The amount of Cu(II) bound to the humic fractions was greater than the amount bound to the fulvic fractions and only at the highest concentrations of metal ion the amount of Cu(II) sorbed by both fractions became equal. The proton to metal ion exchange ratios are similar for all humic substances, with values ranging from 1.0 to 2.0, and decreasing with increased pH. The amount of Cu(II) bound is practically independent of the horizon from which the sample was extracted. The results indicate that the humic substances show similar cation binding behaviour, despite the differences in chemical composition. The copper binding data are quantitatively described with the NICA-Donnan model, which allows to characterize only the carboxylic type binding sites. The values of the binding constants are higher for the humic acids than for the fulvic acids.     

污泥中重金属的去除及回收试验

论述了利用离子交换技术循环使用柠檬酸去除污泥中重金属,并置换回收重金属的适宜工艺条件.经柠檬酸处理后,污泥中90%以上的重金属被去除;柠檬酸处理液中的重金属用离子交换法回收,考察了树脂种类、流速、操作方式等因素对离子交换、再生效果的影响;在适宜工艺条件下,重金属的交换率均为100%,而洗脱率均接近90%;柠檬酸及离子交换树脂循环使用,重金属也得到回收,降低了处理成本.     

Biological nitrification/denitrification of high sodium nitrite (navy shipyard) wastewater

In the hydroblasting of ships' boiler tubes, a wastewater high in nitrite (as high as 1200 mg litre(-1)) is produced by the US Navy. This research has evaluated the use of a suspended-growth biological system to treat this wastewater by denitrification. Two biological treatment configurations were evaluated (direct denitrification versus nitrification/denitrification) with nitrification/denitrification producing better nitrite removal efficiencies (54 to 62% versus 40%, respectively). The introduction of metals (cadmium, chromium, lead, copper and iron) in concentrations typical for this wastewater did not inhibit the nitrite removal efficiencies. The influent metal concentrations ranged from 0.02 mg litre(-1) for cadmium to 22 mg litre(-1) for iron and the metal removal efficiencies ranged from 4.8% for cadmium to 50% for copper. Increasing sludge age resulted in improved nitrite removal efficiencies (52%, 57% and 74% for sludge ages of 4, 6 and 8 days, respectively). The resulting biokinetic constants were similar to those reported by others for lower influent concentrations of nitrite or nitrate (Ygs=0.02 mg/mg; Ygn=0.16 mg/mg; Yb=0.8 mg/mg; and b=0.006 h(-1)).     

Long-range air pollution and its impact on heavy metal accumulation in dippers Cinclus cinclus in Norway

Heavy metals such as cadmium, lead and zinc are deposited in Norway as long-range transported air pollution, while copper deposition is of mainly local origin. This study examined whether the deposition influences the metal concentrations in dippers Cinclus cinclus. The lead concentration in dippers reflected the deposition pattern of long-range air pollution, with higher concentrations in Southern Norway than Central Norway and a significant decrease (>/=40%) between 1987 and 1994. For cadmium, copper and zinc there were no geographical or temporal variations in metal concentrations. For zinc, this lack of geographic and temporal variation probably reflects the fact that it is a homeostatically regulated metal. For both cadmium and copper, local sources are probably more important than long-range sources. Zinc and copper was at higher level in livers of females than in males during the egg laying period. The concentrations of zinc and copper in livers were positively correlated.     

Washing as a remediation technology applicable in soils heavily polluted by mining-metallurgical activities

A permanent solution in order to remediate a heavily contaminated soil is washing it utilizing the appropriate reagents. The study presented in this paper deals with the washing of a soil highly polluted by mining and metallurgical activities. Pollution consists of slags, sulphur compound waste and various low grade lead condensates, all rich in heavy metals and metalloids (Pb, As, Cu, Zn, Mn and Fe). Soil was washed with deionized water, 6, 3, 2 and 1 M HCl, 6 M H(2)SO(4), 6 M HNO(3) and 0.1 M Na(2)EDTA. High extraction efficiency was achieved with respect to hydrochloric acid even at the lowest concentration; the solubility of pollutants in nitric acid was low, while sulphuric acid was proven to be problematic with respect to lead. Mobilization of metals and metalloids under DI water effect was minimal indicating that the elements fraction that is weakly bound to soil particles is insignificant. Furthermore, a kinetic study was undertaken, utilizing 1 M HCl and 0.1 M Na(2)EDTA. Results illustrated that 1 M HCl was more effective for intermediate mixing times (up to 4 h) while 0.1 M Na(2)EDTA was better applicable to short mixing times (<1 h) and low pH values (pH < 7.1). 1 M HCl was proven to be very effective for the removal of pollutants from contaminated soil but the high metal content of the resulting solution necessitates further treatment for the retention of metals.     

Influence of initial pH on bioleaching of heavy metals from contaminated soil employing indigenous Acidithiobacillus thiooxidans

Bioleaching of heavy metals from contaminated soil was carried out employing indigenous sulfur oxidizing bacterium Acidithiobacillus thiooxidans. Experiments were carried out to assess the influence of initial pH of the system on bioleaching of chromium, zinc, copper, lead and cadmium from metal contaminated soil. pH at the end of four weeks of bioleaching at different initial pH of 3-7 was between 0.9 and 1.3, ORP between 567 and 617mV and sulfate production was in the range of 6090-8418mgl(-1). Chromium, zinc, copper, lead and cadmium solubilization ranged from "59% to 98%" at different initial pH. A. thiooxidans was not affected by the increasing pH of the bioleaching system towards neutral and it was able to utilize elemental sulfur. The results of the present study are encouraging to develop the bioleaching process for decontamination of heavy metal contaminated soil.     

Palygorskite as a feasible amendment to stabilize heavy metal polluted soils

The sorption behaviour of palygorskite has been studied with respect to lead, copper, zinc and cadmium in order to consider its application to remediate soils polluted with these metals. The Langmuir model was found to describe well the sorption processes offering maximum sorption values of 37.2 mg/g for lead, 17.4 mg/g for copper, 7.11 mg/g for zinc and 5.83 mg/g for cadmium at pH 5-6. In addition the effect of palygorskite amendment in a highly polluted mining soil has been studied by means batch extractions and leaching column studies. The soluble metal concentrations as well as the readily-extractable metal concentrations were substantially decreased at any concentration of palygorskite applied to soil (1, 2, 4%), although the highest decrease is obtained at the 4% dose. The column studies also showed a high reduction in the metal leaching (50% for lead, 59% for copper, 52% for zinc and 66% for cadmium) when a palygorskite dose of 4% was applied.     

Loofa sponge immobilized fungal biosorbent: a robust system for cadmium and other dissolved metal removal from aqueous solution

The potential of loofa sponge discs to immobilize fungal biomass of Phanerochaete chrysosporium (a known biosorbent) was investigated as a low cost biosorbent for the removal of Cd(II) ions from aqueous solution. A comparison of the biosorption of Cd(II) by immobilized and free fungal biomass from 10 to 500 mg l(-1) aqueous solutions showed an increase in uptake of over 19% when the biomass is immobilized (maximum biosorption capacity of 89 and 74 mg Cd(II) g(-1) biomass for immobilized and free biomass respectively at a solution pH of 6). Equilibrium was established within 1h and biosorption was well defined by the Langmuir isotherm model. The immobilized biomass could be regenerated using 50 mM HCl, with up to 99% metal recovery and reused in ten biosorption-desorption cycles without significant loss of capacity. This study suggests that such an immobilized biosorbent system has the potential to be used in the industrial removal/recovery of cadmium and other pollutant metal ions from aqueous solution.     

Influence of clay on the adsorption of heavy metals like copper and cadmium on chitosan

The influence of clay on the adsorption of heavy metals like copper and cadmium on chitosan from simulated industrial wastewater is evaluated. Chitosan–clay blend with ratio of (1:1), (1:2), and (2:1) have been prepared, and these were used as membranes to remove copper and cadmium ions from synthetic industrial wastewater. The chemical parameters for quantities of adsorption of heavy metal contamination have been done, and the kinetics of adsorption has also been carried out. Clay provides enough absorbable sites to overcome mass transfer limitations. The number of absorbable sites for cadmium is more compared to copper, and thus the rate of recovery of cadmium is faster than copper, and the percentage removal of cadmium is more than copper at all times on clay over nylon 6. This difference indicates the influence of clay in the adsorption of heavy metals in comparison to synthetic polymer nylon 6. Rate constant for first-order kinetics of adsorption, k ₁, for copper and cadmium is less than that of clay, which clearly indicates that clay, which is a natural polymer, is more kinetically favored compared to synthetic polymer. The difference in the intraparticle diffusion in both the natural and synthetic polymer is not much, and it suggests that the particle diffusion mechanism is the same in both cases. Copper and cadmium recovery is parallel at all times. The percentage of removal of copper increased with an increase in pH from 3 to 5. In the case of cadmium containing wastewater, the maximum removal of metal occurred at pH 5. The uptake amount of Cu²⁺ ions on chitosan increased rapidly with increasing the contact time from 0 to 360 min and then reaches equilibrium after 360 min, and the equilibrium constant for copper and cadmium ions are more or less the same for the adsorption reaction. There are more adsorption sites for cadmium in the presence of clay and mass transfer limitation is avoided without resorting to rotation, which is the highlight of the present work. And more so, this is pronounced in the case of natural polymer compared to synthetic polymer.     

Selective separation of copper(II) and nickel(II) from aqueous media using the complexation-ultrafiltration process

The polyethylenimine (PEI) as complexing agent was used to study the complexation-ultrafiltration (CP-UF) process in the selective removal of Cu(II) from Ni(II) contained in aqueous media. Preliminary tests showed that optimal chemical conditions for Cu(II) and Ni(II) complexation by the PEI polymer were pH>6.0 and 8.0, respectively, and polymer/metal weight ratio of 3.0 and 6.0, respectively. The effect of some important operating parameters on process selectivity was studied by performing UF tests at different parameters: pH, polymer/metal weight ratio, transmembrane pressure (TMP), and membrane cut-off in a batch experimental set-up. It was observed that process selectivity was achieved by choosing the pH value for obtaining a preferential copper complexation (pH 6.0), and the polymer/metal ratio needed to bound only the copper ion (3.0). The selective separation by UF tests was performed by using both a laboratory aqueous solution and a real aqueous effluent (water from Emoli torrent, Rende (CS)). The Iris 30 membrane at TMP of 200 kPa (2 bar) for both aqueous media gave the best results. A complete nickel recovery was reached, and copper recovery was the highest for this membrane (94% and 92%). Besides at this pressure, a lower water amount was needed to obtain total nickel recovery by diafiltration. A little higher membrane fouling was obtained by using the river effluent due to the presence of dissolved organic and inorganic matter.     

Heavy metal speciation and mobility assessment of arid soils in the vicinity of Al Ain landfill, United Arab Emirates

Sixty-four surface soil samples taken in the vicinity of Al Ain landfill were analysed for cadmium, chromium, copper, nickel, lead and zinc by inductively coupled plasma spectroscopy. Extraction techniques were used to establish the association of the total concentrations of the six metals in the soil samples with their contents in the exchangeable, carbonate, iron/manganese oxides, and residual fractions. In the investigated soils, the recorded concentrations were as follows: 0.043 mg kg^-1 for cadmium, 19.1 mg kg^-1 for chromium, 53.3 mg kg^-1 for copper, 60 mg kg^-1 for nickel, 13.7 mg kg^-1 for lead, and 117 mg kg^-1 for zinc. Cadmium, chromium, nickel, lead and zinc concentrations in the investigated soil samples reflect the natural background values in shale, whereas copper is slightly enriched. I-geo (geoaccumulation index) values of the metals in the soils under study indicate that they are uncontaminated with cadmium, chromium, nickel, lead and zinc, but contaminated to moderately contaminated with copper. Heavy metal contents in the sediments were found to be significantly influenced by different physico-chemical parameters. The effect of these parameters can be arranged in the following order: clay fraction > carbonate fraction > silt fraction > organic matter fractions. A sequential extraction procedure showed that the total concentrations of the heavy metals are largely bound to the residual phase (retained 71.4% of cadmium, 77.8% of chromium, 75% of copper, 47% of nickel, 62.8% of lead, and 75.8% of zinc). A likely sequence of mobility in the investigated soils is as follows: chromium > lead > nickel > cadmium > zinc > copper.     

Zinc, copper and nickel concentrations in soil extracts and crops grown on four soils treated with metalloaded sewage sludges

Sludges containing high concentrations of zinc, copper or nickel and an uncontaminated sludge were added to two sandy loams (pH 6.5 and 7.1), a heavy clay (pH 6.3) and a calcareous clay (pH 7.8) to give ten sludge treatments for each soil. The mixtures were incubated fallow, cropped continuously with clover, or cropped with barley and red beet in rotation for 21 months. The quantity of added metal either in the soil solution or extracted by 0.1m CaCl(2) depended on the metal loading, pH and soil cation exchange capacity, and changed with time after mixing soils and sludges. Crop metal concentrations, and the occurrence of metal-induced yield reductions, also depended on soil properties as well as metal loading. The best chemical extractant for predicting plant metal concentrations was 0.1m CaCl(2).