Desorption Of Pb Research Articles

Bamboo Juice–Enhanced Desorption of Heavy Metals from Soil

AbstractThe performance of a novel natural agent, bamboo juice, in enhancing the desorption of heavy metals (Cd, Cu, and Pb) from contaminated soil was investigated in the present study. The bamboo juice was obtained from bamboo at elevated temperatures. The bamboo juice greatly enhanced the desorption of Cd and Cu and slightly enhanced the desorption of Pb from the soil. The maximum desorption efficiencies of Cd, Cu, and Pb reached 15.2, 25.7, and 5.9%, respectively, with the addition of 10.45% bamboo juice. The soil slurry pH dropped from 6.0 to 3.0 with the increase in bamboo juice concentration from 0 to 10.45%. The mechanism for the enhanced desorption was explained as the combined effect of pH drop and complexation. The desorbed fractions of Cd, Cu, and Pb with the addition of bamboo juice were exchangeable, followed by those bound to organic matters and Fe-Mn oxides. Although the performance of desorption enhancement by the addition of bamboo juice was lower than that of the addition of ethylenedia...

Enhancing electrokinetic lead removal from sediment: Utilizing the moving anode technique and increasing the cathode compartment length

This study investigates the possibility of simultaneous application of the moving anode technique and increased cathode compartment length as an enhanced electrokinetic treatment of lead-contaminated sediment from the River Tamis. The moving anode technique was employed to improve Pb desorption from sediment particles whilst the increased cathode compartment length was meant to prevent hydroxyl ions from penetrating into the sediment, to avoid metal precipitation and accumulation. Overall lead removal efficacies from the sediment were 38% and 62% after the conventional and enhanced treatments, respectively. Water electrolysis at the implemented anodes resulted in: (a) H+ formation (lowering pH) causing more Pb ions to desorb from the sediment particles and (b) oxygen formation causing the redox potential to become more positive, resulting in lead reorganisation from the oxidizable fraction into more soluble fractions (can be removed by electromigration). The increased cathode compartment length prevented hydroxyl ions penetration into the sediment. Finally, the sediment after the enhanced treatment was Class1/2 according to the Dutch standard. We thus demonstrate that the simultaneous use of the moving anode technique and increased cathode compartment length is an effective technique for electrokinetic removal of lead from sediment which does not involve adding chemicals into the system.

Multiple biosorption–desorption cycles in a fixed-bed column for Pb(II) removal by acid-treated olive stone

Biosorption of Pb2+ from aqueous solutions and desorption of Pb2+ from acid-treated olive stone were studied. Equilibrium screening tests of lead desorption established a solution of 0.3M hydrochloric acid as the most appropriate eluting agent. Fixed-bed biosorption and desorption recovery curves for Pb2+ were obtained for multiple consecutive biosorption–desorption cycles and the biosorption properties of the biomass for Pb2+ were compared after each cycle to evaluate the stability of the biomass. The biosorbent retained most of its original uptake capacity over fourteen cycles of use. Life factor calculation revealed that biosorbent bed would be completely exhausted after 71.3 cycles.

Studies of electrochemical surface alloying and dealloying by in situ high-speed STM

The electrochemical formation and dissolution of a lead/copper surface alloy on Cu(100) in chloride-containing electrolyte solutions were studied on the atomic scale by in situ scanning tunneling microscopy with high temporal and spatial resolution. Alloy formation, induced by a negative potential sweep, starts predominantly at the Cu steps, followed by the formation of a novel transient (4 × 3) alloy phase with 0.25 ML Pb coverage, which continuously is transformed into the 0.375 ML coverage c(4 × 4) phase, observed under UHV conditions. Both of these phases consist of rows of Pb atoms embedded into the Cu surface and exhibit highly dynamic structural fluctuations on sub 100 ms time scales. Upon increasing the potential again, a second c(4 × 4) phase with a different appearance in the STM images forms, which is attributed to partial dealloying, involving desorption of Pb from energetically less favorable sites. Further dealloying results in the formation of ribbon-like structures, already reported in previous studies. These ribbons are shown to consist of Pb atoms decorating domain boundaries in the c(2 × 2) chloride adlayer, left behind on the Cu surface by the dissolving surface alloy phase. Furthermore, dynamic observations of the subsequent coarsening of the ribbon network and the attachment/detachment of isolated Pd adsorbates to the ribbons are presented. Both isolated Pb adsorbates and Pb atoms in the ribbons are proposed to be stabilized by coadsorbed Cl.

Removal of lead (II) ions from aqueous solution by using crosslinked chitosan-clay beads

Abstract A simple and effective biodegradable material known as chitosan-clay composite beads were prepared to remove Pb(II) ions from aqueous solution. For this purpose, various important parameters such as contact time, pH and temperature were examined on the adsorption of Pb(II) ions onto crosslinked chitosan-clay composite beads. Maximum adsorption capacity of Pb(II) was observed at pH 4.5 and 25°C and calculated as 7.93 mg/g according to Langmuir isotherm model. Thermodynamic parameters namely ΔG°, ΔH° and ΔS° of the Pb(II) adsorption process have been calculated as 7.889 kJ/mol, −15.131 kJ/mol and −0.0785 kJ/molK respectively. EDTA was the best eluent for the desorption of Pb(II) ions from the crosslinked chitosan-clay beads. Scanning electron microscope (SEM) was used to characterize the surface morphology of the crosslinked chitosan-clay beads.

Effects of pH and low molecular weight organic acids on competitive adsorption and desorption of cadmium and lead in paddy soils

The bioavailability and ultimate fate of heavy metals in the environment are controlled by adsorption-desorption process. Batch equilibrium experiments were performed to assess the effects of pH and low molecular weight organic acids (LMWOAs) on competitive adsorption and desorption of cadmium and lead in paddy soils from China. The results indicated that both soils exhibited greater sorption capacity for lead (Pb) (1.37-1.61-fold) than cadmium (Cd) as estimated by the maximum sorption parameter (Q) from the Langmuir equation. The Langmuir bonding energy coefficient (b) and distribution coefficient (K (d)) were greater for Pb than for Cd, furthermore, b (binary) and K (d) (single) were greater than b (single) and K (d binary), indicating that competition for sorption sites promote the retention of both metals on more specific sorption sites. Both Cd and Pb desorption as a function of solution pH was characteristic of "S" pattern. The presence of LMWOAs inhibited Cd or Pb desorption at the low concentrations (≤0.1 mmol L(-1)) but promoted Cd and Pb desorption at higher concentrations (≥0.5 mmol L(-1) for citric acid and ≥1 mmol L(-1) for malic and oxalic acid). The two paddy soils had a greater d (Cd) than d (Pb) in the presence of LMWOAs, indicating that Cd desorption was more affected by the presence of LMWOAs in binary metal system.

Competition Absorption and Desorption Dynamic Character of Cadmium, Lead and Zinc by Soil in North-East of China

The competitive absorption and desorption of cadmium (Cd), lead (Pb) and zinc (Zn) in meadow brown soil from Liaoning province in north-east China was studied in the paper in order to establish the selectivity sequences for the sorption and desorption of these heavy metals in the soil and obtain the absorption and desorption dynamic character of these heavy metals. The results showed that with the increasing of the absorption times, the absorption quantities of Cd, Pb and Zn were increased little by little. The absorption process of Cd, Pb and Zn could be divided into the fast absorption phase and the slow absorption phase. And the fast absorption phases were from the beginning to 60 min, 120 min and 120 min for Cd, Pb and Zn, respectively. The more company metals (i.e. Pb and Zn) existed in the absorption solutions, the less absorption quantities of Cd absorbed by soil. The co-existence of Cd, Pb and Zn had obviously decreased the absorption of Pb by soil. And it was the same situation that Zn absorbed by soil was decreased by the company metals such as Cd, Pb. The company metals had obvious influence on the desorption process of Cd. The existence of Pb and Zn promoted the desorption of Cd. And desorption behavior of Zn was bated by the existence of Pb and Cd. While the company metals Cd and Zn restrained the desorption of Pb. The best equation to describe the absorption and desorption dynamic character of Cd, Pb and Zn was Elovich equation, next was Two–constant equation, and the effect of First-order dynamics equation was not good.

Sorption and desorption of Cd, Cu and Pb using biomass from an eutrophized habitat in monometallic and bimetallic systems

This work examines the sorption capacity of a natural biomass collected from an irrigation pond. The biomass mainly consisted of a mixture of chlorophyte algae with caducipholic plants. Biosorption experiments were performed in monometallic and bimetallic solutions containing different metals commonly found in industrial effluents (Cd, Cu and Pb). The biosorption process was slightly slower in the binary system comparing with monometallic system which was related to competition phenomena between metal cations in solution. The biosorbent behaviour was quantified by the sorption isotherms fitting the experimental data to mathematical models. In monometallic systems, the Langmuir model showed a better fit with the following sorption order: Cu ∼ Pb > Cd; and biomass-metal affinity order: Pb > Cd ∼ Cu. In bimetallic systems, the binary-type Langmuir model was used and the sorption order obtained was: Pb ∼ Cu > Cd. In addition, the effectiveness of the biomass was investigated in several sorption–desorption cycles using HCl and NaHCO3. The recovery of metal was higher with HCl than with NaHCO3, though the sorption uptake of the biomass was sensitively affected by the former desorption agent in subsequent sorption cycles.

Experimental and modeling studies of lead (II) sorption onto a polyvinyl-chloride inclusion membrane

In the present paper, a polymer inclusion membrane (PIM) containing 50% polyvinyl chloride (PVC), and 50% bis-(2-ethylhexyl) phosphate (D2EHPA) as extracting agent is used for the removal of Pb(II) ions from aqueous acid solution, by using the batch extraction technique. The optimal PIM composition was discussed both in correlations with the PIM's morphology, and also with the sorption mechanism. The characterization of PIM, realized by atomic force microscopy (AFM), and differential scanning calorimetry (DSC), highlighted the membrane morphology and the plasticizing role of the sorption agent D2EHPA, respectively. The sorption kinetics was well described by the pseudo-second order model, and the adsorption isotherm was best fitted by the Redlich–Peterson equation. The kinetic experiments confirm that the sorption process of Pb(II) into the optimal 50%D2EHPA/50%PVC PIM is a chemisorption. The Pb(II) sorption into the PIM occurs by a “relay mechanism”. The experimentally determined maximum sorption capacity of PIM for Pb(II) ions was found to be 60.785mg/g, and it is among the highest values reported in literature. Moreover, the desorption of Pb(II) ions, as well as the regeneration of PIM can be achieved at least five times by using 0.5M HNO3. We consider that this membrane (50%D2EHPA/50%PVC) is a good candidate to be used as solid sorbent, due its lower price comparing to the plasticized PIMs, high sorption capacity, and good regeneration properties, with the regeneration process simultaneous with the metal recovery.

Facilitated desorption and stabilization of sediment-bound Pb and Cd in the presence of birnessite and apatite

Desorption of lead (Pb) and cadmium (Cd) from contaminated sediments was investigated to clarify the effect of stabilizing agents on Cd and Pb desorption kinetics. The desorbed aqueous Cd and Pb concentrations and the residual amounts of Cd on the sediments in the desorption tests were best fitted to a pseudo-second-order kinetics with the highest R 2 values among the models used in the kinetic studies. The average residual Cd on sediments were 24% and 19% less in the presence of apatite and birnessite, respectively, than in the absence of them. However, the Pb desorption was not affected by the stabilizing agents. The negligible aqueous concentrations of desorbed Cd and Pb in the presence of apatite and birnessite suggest the stabilization of desorbed Cd that was facilitated by apatite and birnessite and Pb. The kinetics study with Cd shows that the rate constants are not affected, but the desorption extents are affected in the presence of apatite and birnessite. The Tessier sequential extraction method and toxicity characteristic leaching procedure indicate that Pb is more strongly bound on the stabilizing agents than Cd. Overall, birnessite and apatite can be successfully applied in remediation of Cd and Pb contaminated sediment.

Pyromorphite formation from montmorillonite adsorbed lead

Pyromorphite formation from montmorillonite adsorbed lead The reaction of Pb-adsorbed montmorillonite with aqueous solutions of PO4 and Cl ions results in the decrease in phosphate concentration associated with the formation of a new phase - pyromorphite Pb5(PO4)3Cl. Pyromorphite crystals range in size from hundreds of nm to several tens of μm, depending on the PO4, K, and Ca concentrations in the reacting system. A strong ion-exchange effect of K+ and Ca2+ cations on desorption of Pb2+ from Pb-adsorbed montmorillonite was observed. Also, a high concentration of cations leads to a rapid desorption of Pb and the formation of fine pyromorphite crystals. In contrast, low PO4, K and Ca concentrations result in the formation of relatively large euhedral crystals. Final Pb concentrations are much lower in experimental sets than in control experiments with no phosphate present.

Biosorption of heavy metals from aqueous solutions by chemically modified orange peel

Equilibrium, thermodynamic and kinetic studies were carried out for the biosorption of Pb 2+, Cd 2+ and Ni 2+ ions from aqueous solution using the grafted copolymerization-modified orange peel (OPAA). Langmuir and Freundlich isotherm models were applied to describe the biosorption of the metal ions onto OPAA. The influences of pH and contact time of solution on the biosorption were studied. Langmuir model fitted the equilibrium data better than the Freundlich isotherm. According to the Langmuir equation, the maximum uptake capacities for Pb 2+, Cd 2+ and Ni 2+ ions were 476.1, 293.3 and 162.6 mg g −1, respectively. Compared with the unmodified orange peel, the biosorption capacity of the modified biomass increased 4.2-, 4.6- and 16.5-fold for Pb 2+, Cd 2+ and Ni 2+, respectively. The kinetics for Pb 2+, Cd 2+ and Ni 2+ ions biosorption followed the pseudo-second-order kinetics. The free energy changes (Δ G°) for Pb 2+, Cd 2+ and Ni 2+ ions biosorption process were found to be −3.77, −4.99 and −4.22 kJ mol −1, respectively, which indicates the spontaneous nature of biosorption process. FTIR demonstrated that carboxyl and hydroxyl groups were involved in the biosorption of the metal ions. Desorption of Pb 2+, Cd 2+ and Ni 2+ ions from the biosorbent was effectively achieved in a 0.05 mol L −1 HCl solution.

Sorption and desorption behavior of lead on a Chinese kaolin

The sorption and desorption of Pb on kaolin from Suzhou, China were investigated. The sorption experiment was conducted in a 0.01 M NaNO3 aqueous solution with respect to the effects of initial Pb concentration, pH, solid/solution ratio, and temperature. Langmuir and Freundlich models well described equilibrium isotherms of Pb sorption. Less than 5% of Pb sorbed was desorbed with 0.01 M NaNO3 extraction, suggesting a dominant specific sorption of Pb. As the initial pH increased, the sorption of Pb on the kaolin increased. More than 60% of Pb was sorbed at pH 2.69 far below the point of zero net charge of the kaolin at 4.2, indicating a mechanism of Pb inner-sphere complex or by chemisorption. Lead sorption decreased with increasing temperature, indicating a process of exothermic sorption.

Sorption and Desorption of Pb(II) from Aqueous Solution using Triplochiton scleroxylon Sawdust as Sorbent

Sorption and Desorption of Pb(II) from Aqueous Solution using Triplochiton scleroxylon Sawdust as Sorbent

Adsorption and desorption of Cu(II), Cd(II) and Pb(II) ions using chitosan crosslinked with epichlorohydrin-triphosphate as the adsorbent

In this study, chitosan (CTS) was crosslinked with both epichlorohydrin (ECH) and triphosphate (TPP), by covalent and ionic crosslinking, respectively. The resulting new CTS–ECH–TPP adsorbent was characterized by CHN analysis, EDS, FTIR spectroscopy, TGA and DSC, and the adsorption and desorption of Cu(II), Cd(II) and Pb(II) ions in aqueous solution were investigated. Potentiometric studies were also performed and revealed three titratable protons for each p K a value of 5.14, 6.76 and 9.08. The results obtained showed that the optimum pH values for adsorption were 6.0 for Cu(II), 7.0 for Cd(II) and 5.0 for Pb(II). The kinetics study demonstrated that the adsorption process proceeded according to the pseudo-second-order model. Three isotherm models (Langmuir, Freundlich and Dubinin-Radushkevich) were employed in the analysis of the adsorption equilibrium data. The Langmuir model resulted in the best fit and the new adsorbent had maximum adsorption capacities for Cu(II), Cd(II) and Pb(II) ions of 130.72, 83.75 and 166.94 mg g −1, respectively. Desorption studies revealed that HNO 3 and HCl were the best eluents for desorption of Cu(II), Cd(II) and Pb(II) ions from the crosslinked chitosan.

Immobilization of S. duplicatum supported silica gel matrix and its application on adsorption–desorption of Cu (II), Cd (II) and Pb (II) ions

It has been carried out a research adsorption–desorption of metal ion Cu (II), Cd (II) and Pb (II) on Sargassum duplicatum ( S. duplicatum) biomass immobilized by silica gel with a continuous method using a set of adsorption equipment controlled automatically. From the optimum result of this equipment, it has been obtained that an average of flow rates Cu (II), Cd (II) and Pb (II) ions by S. duplicatum biomass immobilized by silica gel is 1.3 mL min − 1 . Adsorption process of metal ions Cu (II), Cd (II) and Pb (II) on S. duplicatum biomass immobilized by silica gel is optimum at pH of 5.0 with the adsorption capacities of 280.112, 130.513 and 113.660 μmol g − 1 respectively. On the competition adsorption, the Cu (II) ion is more adsorbed on S. duplicatum immobilized by silica gel with the adsorption selectivity coefficient ( α) > 1. The uses of 2.0 mmol L − 1 HCl as eluent of Cu (II), Cd (II) and Pb (II) ions adsorbed on S. duplicatum immobilized by silica gel resulted recovery percent (%) are 98.63 ± 0.56, 84.79 ± 0.40 and 70.11 ± 0.17, respectively.

The resistance of single atomic steps in ultrathin Pb nanowires on Si(557)

We studied the local electronic transport properties of a monolayer thick Pb wire by local potentiometry with the tip of a tunneling microscope. 50-nm-wide wires on bare Si(557) were generated by direct writing with an electron beam in an ultrathin film of SiO2 using the process of electron-beam-induced selective stimulated thermal desorption of oxygen (EBSTD) in combination with a shadow-mask technique and macroscopic TiSi2 contacts. The resistivity of this wire agrees well with expectations derived from anisotropic monolayer thick Pb films on Si(557). Although small Pb clusters nucleated during annealing and desorption of excess Pb, they had a negligible effect on the local resistive properties of the wire. Steps in the substrate of atomic height apparently do not interrupt the conducting path, but due to local scattering at step edge states increase the local resistivity by more than one order of magnitude.

Adsorption and desorption of Cu(II), Zn(II), Pb(II), and Cd(II) on the soils amended with nanoscale hydroxyapatite

AbstractAdsorption and desorption of Cu(II), Zn(II), Pb(II) and Cd(II) on a Red soil (RS, Udic Ferrosols) and a Wushan soil (WS, Anthrosol) amended with nanoscale hydroxyapatite (nano‐HAP) were studied by batch experiments. The adsorption isotherms show that different kinds of heavy metals had different affinity to the soils in the order of Cu(II) > Pb(II) > Cd(II) > Zn(II). The amount of each heavy metal adsorbed on the RS was lower than that on the WS, because the former had lower CEC and pH than the latter. The amendment of nano‐HAP in the soils significantly enhanced the adsorption of heavy metals, in comparison with the treatment receiving no nano‐HAP. The Kf, simulated from the adsorption isotherms, increased from 78 to 2180 for Cu(II), 16.6 to 59.5 for Zn(II), and 17.9 to174 for Cd(II) on the RS, and from 995 to 6410 for Cu(II), 52.5 to 92.4 for Zn(II), and 59.2 to 199 for Cd(II) on the WS, when 0.20 g nano‐HAP was added into 1.00 g soil. The nano‐HAP remarkably inhibited desorption of heavy metals from the soils, suggesting that the addition of nano‐HAP can significantly reduce the mobilization of heavy metals and increase their geochemical stability in metal contaminated soils. © 2009 American Institute of Chemical Engineers Environ Prog, 2010

Mobility and plant-availability of Cd(II) and Pb(II) adsorbed on zeolite and bentonite

The objective of this work was to study the desorption behaviour and plant-availability of Cd(II) and Pb(II) adsorbed on zeolite and bentonite in a batch and a pot (sand) culture experiment. In a sequential desorption experiment Cd(II) and Pb(II) desorption from the zeolite (at 50, 75 and 100% of maximum adsorption capacity, SC max) equilibrated with 0.01 M Ca(NO 3) 2 was lower as compared to bentonite at all the metal ion loading rates. Amounts of 3, 14 and 31% of the initially adsorbed Pb(II) were desorbed from the bentonite but only 1, 3 and 5% from the zeolite. The corresponding desorbed quantities of Cd(II) were 53, 65 and 71% for bentonite and 41, 33 and 21% for zeolite. In the pot (sand) culture experiments in a greenhouse, corn seedlings were planted in pots filled with quartz sand mixed with zeolite or bentonite enriched with Cd(II) or Pb(II). The concentration of Cd(II) and Pb(II) in the corn roots and shoots grown in the enriched bentonite–sand culture system was significantly higher than those planted in the enriched zeolite–sand culture indicating a stronger immobilizing of Cd(II) and Pb(II) by the zeolite.

Adsorption and desorption of Cu(II) and Pb(II) in paddy soils cultivated for various years in the subtropical China

The adsorption and desorption of Cu(II) and Pb(II) on upland red soil, and paddy soils which were originated from the upland soil and cultivated for 8, 15, 35 and 85 years, were investigated using the batch method. The study showed that the organic matter content and cation exchange capacity (CEC) of the soils are important factors controlling the adsorption and desorption of Cu(II) and Pb(II). The 15-Year paddy soil had the highest adsorption capacity for Pb(II), followed by the 35-Year paddy soil. Both the 35-Year paddy soil and 15-Year paddy soil adsorbed more Cu(II) than the upland soil and other paddy soils. The 15-Year paddy soils exhibited the highest desorption percentage for both Cu(II) and Pb(II). These results are consistent with the trend for the CEC of the soils tested. The high soil CEC contributes not only to the adsorption of Cu(II) and Pb(II) but also to the electrostatic adsorption of the two heavy metals by the soils. Lower desorption percentages for Cu(II) (36.7% to 42.2%) and Pb(II) (50.4% to 57.9%) were observed for the 85-Year paddy soil. The highest content of organic matter in the soil was responsible for the low desorption percentages for the two metals because the formation of the complexes between the organic matter and the metals could increase the stability of the heavy metals in the soils.