Uptake Of Pb2 Research Articles

Enhanced lead (II) adsorption from aqueous solution using sawdust-derived amino-decorated cellulose: Optimization, isotherm, kinetics, and reusability studies

Water pollution, driven by Pb2+, poses a significant threat to biotics and the environment. A promising solution to address the issue is the utilization of cellulose from lignocellulosic materials as an adsorbent to remove or reduce Pb2+ from wastewater. However, as reported, the adsorption capacities of native cellulose adsorbents vary depending on their plant source, and their metal binding capacity is not as satisfactory as expected due to a lack of robust chelation sites, particularly amino groups. Thus, this study aimed to improve Pb2+ uptake capacity by utilizing the prosopis juliflora stem, a previously unexplored cellulose source, as an adsorbent through ethylenediamine (EDA) grafting. FTIR, XRD, FE-SEM, EDX, and TGA evaluated the physicochemical properties of amino-decorated cellulose (ADC) adsorbent. The effect of experimental variables (initial Pb2+ concentration, ADC dose, and contact time) on percent removal was investigated and analyzed using Box-Behnken Design (BBD). Analysis of variance (ANOVA) revealed that, among the interaction effects, only the interactions between initial Pb2+ concentration and ADC dose significantly affected percent removal (P < 0.0008). The optimal percent removal and Pb2+ uptake onto ADC at conditions: pH of 5, ADC dose of 0.47 g, initial Pb2+ concentration of 52 mg L−1, and contact time of 118 min was 97.37 % and 53.86 mg g−1, respectively. The uptake of Pb2+ onto ADC agreed well with the Langmuir isotherm and the pseudo-second-order kinetic model. The adsorption isotherm analysis demonstrated that ADC created a monolayer for Pb2+ attachment during adsorption, with a maximum Langmuir Pb2+ uptake capacity of 64.72 mg g−1. Additionally, the analysis of the adsorption kinetics indicated that chemisorption was the dominant mechanism for the removal of Pb2+. Results from regeneration studies revealed that ADC retained its good Pb2+ uptake capacity for up to four cycles.

Effect of polylactic acid microplastics and lead on the growth and physiological characteristics of buckwheat

Microplastics (MPs) and heavy metals are common, often co-existing pollutants, that threaten crop growth and productivity worldwide. We analysed the adsorption of lead ions (Pb2+) to polylactic acid MPs (PLA-MPs) and their single factor and combined effects on tartary buckwheat (Fagopyrum tataricum L. Gaertn.) in hydroponics by measuring changes in the growth characteristics, antioxidant enzyme activities and Pb2+ uptake of buckwheat in response to PLA-MPs and Pb2+. PLA-MPs adsorbed Pb2+, and the better fitting second-order adsorption model implied that Pb2+ was adsorbed by chemisorption. However, the similar Pb2+ contents in the plants treated with Pb2+ only and those treated with the combined PLA-MPs-Pb2+ suggested that the adsorption played no role in the uptake of Pb2+. Low concentrations of PLA-MPs promoted shoot length. At high concentrations of both PLA-MPs and Pb2+, buckwheat growth was inhibited, and leaf peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) activities and malondialdehyde (MDA) contents were higher than in the control. No significant differences were observed in seedling growth between exposure to Pb2+ only and combined exposure to PLA-MPs with Pb2+, implying that PLA-MPs did not increase the toxicity of Pb2+ at macroscopic level. POD activity was higher and chlorophyll content was lower with PLA-MPs in the low Pb2+ dose treatments, suggesting that PLA-MPs may increase the toxicity of naturally occurring Pb2+. However, the conclusions must be verified in controlled experiments in natural soil conditions over the whole cultivation period of buckwheat.

Rapid and selective removal of Pb ions by electroactive titanium Dioxide/Polyaniline ion exchange film

The slow accumulation of heavy metal in the sediment and aquatic food chain, leads to extremely bad health influence in human body. Most of the traditional adsorption materials have deficient adsorption capacity and selectivity. In this research, the TiO2/PANI composite material is synthesized successfully by intercalating 2HT (intercalating agent) and PANI into the interlayer of the TiO2 nanosheet for the separation of Pb2+. During this synthesis process, the layer spacing of TiO2/PANI can be controlled precisely by adjusting the concentration of 2HT and PANI. The rapid Pb2+ uptake/ release process is triggered through turning the redox states of composite film which can leads to the conversion between Ti4+ and Ti3+ and the conversion between –OH and -O-Pb covalent bond for maintaining the electrical neutrality. In addition, the directional H+ proton migration, fast electronic transporting network and superfast Pb2+ ion transport path both are benefit for the transmission and uptake of Pb2+. As a result, this composite film illustrates ultrahigh uptake capacity (1499.99 mg∙g−1) and selectivity (KD = 15.2 L·g−1). It can even treat real wastewater to a level lower than WHO. Hence, this composite film with superior electrochemical performance is a promising material, which could be used for uptake/release of Pb2+.

Polymer-Based Nano-Adsorbent for the Removal of Lead Ions: Kinetics Studies and Optimization by Response Surface Methodology

This work successfully created a polypyrrole-polyethyleneimine (PPy-PEI) nano adsorbent for the elimination of the lead ion Pb2+ from an aqueous solution. An efficient conducting polymer-based adsorbent called as was created using ammonium persulfate (NH4)2S2O8 as an oxidant (PPy-PEI). The PEI hyper-branched polymer with terminal amino groups was added to the PPy adsorbent to offer heavy metals more effective chelating sites. Pb2+ removal from aqueous solution using polyethyleneimine micro adsorbent was successfully accomplished using a batch equilibrium technique (PPy-PEI). The generated water-insoluble polymer nanoadsorbent had enough nitrogen atoms; therefore, an effort was made to link PEI, a water-soluble PPy, with PPy, a conjugated polymer, for lead ion adsorption from an aqueous solution. The generated PPy-PEI nanoadsorbents were discovered to have average particle sizes of 18–34 nm and a Brunauer-Emmet-Teller surface area of 17 m2/g, respectively. The thermal behavior of the composites was investigated using thermo gravimetric and differential scanning calorimetric methods. The lead ion adsorption efficacy of pure polypyrrole was found to be 38%; however, a batch equilibrium technique employing nanoadsorbent revealed with the maximum adsorption capacity of 75.60 mg g−1. At pH 10 and 30 min of contact time at 50 °C, 0.2 g of adsorption was shown to be the ideal dosage. X-ray diffraction analysis, energy-dispersive ray spectroscopy, and Fourier transform infrared ray spectrum support the lead ion adsorption by PPy-PEI nanoadsorbents. The cauli-like structure was visible using field emission scanning electron microscopy. Studying the thermodynamic showed that the adsorption was endothermic as illustrated from the positive value of value of ΔH° is 1.439 kJ/mol which indicates that the uptake of Pb2+ onto nanoadsorbent PPy-PEI could be attributed to a physical adsorption process. According to the values of ΔG°, the adsorption process was spontaneous at all selected temperatures. The positive value of ΔS° value (43.52 j/mol) suggested an increase in the randomness at the solid/solution interface during the adsorption process. The adsorption data meet the pseudo-second-order kinetic model and suited the Langumuir isothermal model effectively.

Enhancing the remarkable adsorption of Pb2+ in a series of sulfonic-functionalized Zr-based MOFs: a combined theoretical and experimental study for elucidating the adsorption mechanism.

A series of Zr-based metal-organic frameworks was prepared via the solvothermal route using sulfonic-rich linkers for the efficient capture of Pb2+ ions from aqueous medium. The factors affecting adsorption such as the solution pH, adsorbent dosage, contact time, adsorption isotherms, and mechanism were studied. Consequently, the maximum adsorption capacity of Pb2+ on the acidified VNU-23 was determined to be 617.3 mg g-1, which is much higher than that of previously reported adsorbents and MOF materials. Furthermore, the adsorption isotherms and kinetics of the Pb2+ ion are in good accordance with the Langmuir and pseudo-second-order kinetic model, suggesting that the uptake of Pb2+ is a chemisorption process. The reusability experiments demonstrated the facile recovery of the H+⊂VNU-23 material through immersion in an HNO3 solution (pH = 3), where its Pb2+ adsorption efficiency still remained at about 90% of the initial uptake over seven cycles. Remarkably, the adsorption mechanism was elucidated through a combined theoretical and experimental investigation. Accordingly, the Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy connected to energy-dispersive X-ray mapping (SEM-EDX-mapping), and X-ray photoelectron spectroscopy (XPS) analysis of the Pb⊂VNU-23 sample and comparison with H+⊂VNU-23 confirmed that the electrostatic interaction occurs via the interaction between the SO3- moieties in the framework and the Pb2+ ion, leading to the formation of a Pb-O bond. In addition, the density functional theory (DFT) calculations showed the effective affinity of the MOF adsorbent toward the Pb2+ ion via the strong driving force mentioned in the experimental studies. Thus, these findings illustrate that H+⊂VNU-23 can be employed as a potential adsorbent to eliminate Pb2+ ions from wastewater.

Conversion of Natural Bentonite into Effective Adsorbents for Removing of Pb2+ Ions from Wastewater

Adsorption is an effective techniques using for removing heavy metal contamination from wastewater. In order to study the capacities of both natural and modified bentonite (synthetic analcime zeolite (ANA)) samples to remove lead ions, batch adsorption experiments of Pb2+ were conducted under various conditions. Most essential parameters such as initial solution pH, adsorbent mass and contact time were studied. Bentonite clay was activated and went through various thermal and chemical processes. The result from this route shows that zeolite ANA crystals with regular icositetrahedron have been successfully synthesised. The efficiency of both natural bentonite and zeolite ANA converted from natural bentonite and their ability for the reducing of Pb2+ ions from industrial wastewaters have investigated and the results show that heavy metal removal was enhanced with increased initial solution pH, greater mass of absorbent and fast in the in the first hour. The uptake of Pb2+ ions from solution by synthetic zeolite type ANA was improved compared to natural bentonite.

The sorption of single- and multi-heavy metals in aqueous solution using enhanced nano-hydroxyapatite assisted with ultrasonic

Nano-hydroxyapatite (nHAP) has been often used as environment material for the remediation of heavy metal contaminated water and soil. Here, an enhanced nHAP was synthesized with the assistance of ultrasonic and was employed for the sorption of single- and multi-heavy metals. The characteristics of SEM, TEM, XRD, FTIR and XPS were utilized for the investigating of competitive sorption mechanism and the metal properties were correlated with the sorption capacities. The impact of ultrasonic time on the performance of nHAPs varied from different metal ions with the apparent improvement on the uptake of Pb2+, followed by Cu2+ and Zn2+, while without significant effects on for Cd2+. The maximum sorption capacity values of nHAP were 1352, 272, 285 and 304 mg g–1 for Pb2+, Cu2+, Zn2+ and Cd2+, respectively. Competitive sorption would seriously affect the uptake of Cd2+ while exerting little influence on Pb2+ for their different metal properties and dominant sorption mechanisms. The enhanced nHAP synthesized with ultrasonic simultaneously presented a high sorption capacity for several heavy metals which could be a promising environmental material for wastewater treatment and soil remediation.

Levels of induced free proline in chelated and unchelated hydroponically grown lettuce (&lt;i&gt;Lactuca sativa L.&lt;/I&gt;)

It is well described that under stress conditions many plant species accumulates proline as adaptive response to adverse conditions. In this study, eight weeks old Lactuca sativa L. seedlings were transplanted in nutrient solution containing various doses (0.000, 0.0025, 0.005, 0.0075, and 0.025mg/L) of Pb2+ and Cd2+ and constant concentration of EDDS (0.0025M). The effects of these treatments of Pb2+, Cd2+, combination of Pb2+ + Cd2+and with or without EDDS (Ethylene diamine disuccinate) were compared based on the level of stress induced to the seedlings. Free proline contents induced due to stress by uptake of Pb2+and Cd2+ were investigated in both unchelated and chelated treatment. The results obtained showed that the effect of increasing concentration of Pb2+ in hydroponic solution leads to decrease in the level of stress induced to the seedlings by EDDS while the lower the Cd2+ concentration in the hydroponic solution the more the level of stress induced by EDDS to the plant. The highest level of stress caused to the seedlings by unchelated and chelated Pb2+ solution are 68.294±5.642; 72.681±14.740 µmolg-1 respectively while that of Cd2+ are 28.962±8.703; 48.263±2.455 µmolg-1 respectively. From this, it is evident that Pb2+induced more stress to the plants than Cd2+ in the presence and absence of EDDS (p&lt;0.05).&#x0D; Keywords: Proline, Ethylenediaminedisuccinic Acid (EDDS), Lead, Cadmium, Lettuce.

Insights into dynamic adsorption of lead by nano-hydroxyapatite prepared with two-stage ultrasound

Nano-hydroxyapatite (nHAP) has an excellent effect on the remediation of Pb contaminated water and soil. In this study, an efficient modified nHAP was prepared assisted with two-stage ultrasonic irradiation. The effects of ultrasound modification on the nHAP were tested using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform InfraRed spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) and combined batch Pb uptake experiments. The nHAP with ultrasound has a fine structure with the width and length of around 9 nm and 40 nm respectively. The ultrasound parameter of 1s/36s in stage 1 and 16s/18s in stage 2 was verified as the optimum under which the nHAP prepared performed the best with the maximum adsorption capacity of 1300.93 mg/g. The results of XRD and SEM indicated that the sorbent after uptake of Pb2+ was mainly Pb10(PO4)6OH2 (HPY) with insignificant Ca10Pb10-x(PO4)6OH2. Compared the results of Pb/Ca, pH and XRD with the metal fraction of Pb in adsorbents during the dynamic sorption process, this research proved that the effects of complexation, cation exchange and dissolution and precipitation coexisted in the initial stage, while the dissolution and precipitation gradually dominated the adsorption mechanism with contact time. The processes of Pb2+ uptake by nHAP sorbents prepared under different ultrasound parameter presented almost the same dynamic mechanism with a little difference in time node. The research of dynamic mechanism of Pb2+ uptake by a superior nHAP is essential for both contaminated water and soil remediation.

Preparation of hydroxyapatite-based porous materials for absorption of lead ions.

In this paper, soybean protein isolate (SPI) was used as template, hydroxyapatite was crystallized on protein chains of SPI by in-situ synthesis, then the obtained inorganic HA/biopolymer SPI composite (HA@SPI) was calcined at suitable temperature, which afforded a novel hydroxyapatite-based porous materials (HApM). The results indicated that the product showed a porous morphology structure and excellent absorption performance for Pb2+. HApM maximum removal of lead was attained (96.25%) at an initial pH value of 7.4, temperature of 25 °C and contact time of 30 min with an initial metal concentration of 60 mg/L. In order to identify composition, structure and functional groups involved in the uptake of Pb2+, Fourier transform infrared spectrometer (FTIR), thermogravimetric analysis (TG), X-ray diffraction (XRD) scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Brunauer-Emmett-Teller (BET) analysis were carried out. Therefore, the hydroxyapatite-based porous materials (HApM) is a promising candidate for the treatment of liquid wastes containing toxic Pb2+ metal ion, heavy metal ion antidotes and other related fields.

Mathematical modelling of Pb2+, Cu2+, Ni2+, Zn2+, Cr6+ and Cd2+ ions adsorption from a synthetic acid mine drainage onto chitosan derivative in a packed bed column

ABSTRACTStudies on the adsorption of toxic metal ions in batch mode using modified chitosan beads have been reported by several authors in literature; for large-scale operations, packed bed column studies are performed to generate data that are directly applicable in real wastewater treatment. In this work, the application potential of chitosan derivative for the uptake of Pb2+, Cu2+, Ni2+, Zn2+, Cr6+, and Cd2+ ions from aqueous solution in a packed bed adsorption column was investigated. On this note, the adsorbent was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Scanning electron microscope (SEM); the effect of breakthrough parameters such as influent concentration, bed height, and feed flow rate was determined. The experimental data were fitted to mathematical column models, namely Bed Depth Service Time (BDST), Yoon-Nelson and Thomas model. The removal efficiency, breakthrough and exhaustion time increased with an increase in bed height but decreased with an increase in the flow rate and influent concentration. The mathematical models applied in this study were successful in describing experimental data. Desorption studies were performed with no loss in the mass of the beads, and the breakthrough and exhaustion time were found to be the same on reusing the beads.Abbreviations: Ch-b: chitosan coated bentonite; GXXB: grafted cross-linked chitosan beads; MMBB: multi metal binding biosorbent; PFOLG: panosized ferric oxide loaded glycidyl; MPSD: Marquardt’s percent standard deviation

In situ synthesis of MnO2-loaded biocomposite based on microcrystalline cellulose for Pb2+ removal from wastewater

We fabricated a new MnO2-loaded biocomposite based on microcrystalline cellulose (MCC–MnO2) by an in situ synthesis method and investigated its adsorption behavior and mechanism for Pb2+ removal from aqueous medium. As-prepared MCC–MnO2 was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) analyses. The effects of pH value, initial Pb2+ concentration, contact time, and solution temperature on the uptake of Pb2+ onto MCC–MnO2 were investigated using a batch system. Adsorption equilibrium could be achieved in 3 h for various studied initial concentrations, and a pseudo-second-order model could fit the adsorption behavior well. The equilibrium data could be well described by the Langmuir isotherm model, and the maximum monolayer adsorption capacity of MCC–MnO2 (with 7.98% MnO2 loading) for Pb2+ was estimated to be 247.5 mg/g at 313 K. Thermodynamic studies indicated a spontaneous and endothermic adsorption process. X-ray photoelectron spectroscopy (XPS) was used to analyze the adsorption mechanism, revealing that the chemical speciation of Pb2+ on MCC–MnO2 was similar to the compound PbO. Moreover, no variations in the valence of Mn were observed after adsorbing Pb2+. The regeneration study showed that the adsorption capacity retained about 89.6% of its initial value at the fifth sequential regeneration cycle, indicating that this material is an efficient and renewable hybrid adsorbent for Pb2+ removal.

Preparation and characterization of poly (itaconic acid)-grafted crosslinked chitosan nanoadsorbent for high uptake of Hg2+ and Pb2+

A novel nanoadsorbent (PIACS) with average size of 52.6nm was prepared by controlling grafted polymerization of itaconic acid on chitosan to emulsion stage and then crosslinking with glutaraldehyde. The preparation conditions were optimized and PIACS was characterized by FT-IR, XRD, SEM, TEM and TGA. The adsorption of PIACS for some metal ions was studied. The adsorption results showed that PIACS for adsorption of Hg2+ and Pb2+ had higher uptakes than some reported adsorbents. Various variables for adsorption of Hg2+ and Pb2+ were systematically researched. The adsorption followed the pseudo-second-order kinetics and Langmuir isotherm models. The maximum uptakes of Hg2+ and Pb2+ from Langmuir model were 870.1mgg−1 and 1320mgg−1, respectively. Especially, the uptake of this nanoadsorbent for Pb2+ was 4 times of that of the macro-scale adsorbent with the similar structure reported. As temperature rising, uptake of Pb2+ decreased while uptake of Hg2+ almost had no change. In addition, the adsorbent could be regenerated with EDTA. Hence, this prepared method of nanomaterial might extend to the similar grafted polymerizing and crosslinking systems of polymers and PIACS would be a promising adsorbent in the removal of Hg2+ and Pb2+ from wastewaters.

Using a novel adsorbent macrocyclic compound cucurbit[8]uril for Pb2 + removal from aqueous solution

In this study, cucurbit[8]uril (CB[8]) was utilized as a kind of new adsorbent to remove Pb2+ ions from aqueous solution. With the solution pH increased from 2 to 6, the removal efficiency of adsorption increased from 55.6% to 74.5%correspondingly. The uptake of Pb2+ increased rapidly in the initial 30min, and then the adsorption rate became slower. The Pseudo-second order model could be used to interpret the adsorption kinetics satisfactorily; and the rate determining step in Pb2+ adsorption onto CB[8] was the external mass transfer step. Equilibrium isotherm study reveals that the Langmuir model gave a better fitting result than Freundlich model. The maximum adsorption capacity calculated by the Langmuir model was 152.67mg/g for 298K, 149.70mg/g for 313K and 136.42mg/g for 323K, respectively. The adsorption is a spontaneous process of exothermic nature. The effect of the adsorbent dosage and the influences of solution pH and co-existing cations were also investigated. The CB[8] was synthesized and characterized by 1H NMR, IR, ESI-MS spectra, SEM-EDAX, Zeta-potential and BET-analysis. The adsorption mechanism was due to the coordination between CB[8] molecule and Pb2+ ions.

Engineering behavior influence of basaltic rocks on the adsorption of heavy metal ions

Basaltic rocks obtained from Qusier area, south Eastern Desert, Egypt showed to be effective in removing heavy metals from aqueous solution. According to mechanical and engineering scheme, the basaltic rocks were classified into basalt weathering grade I (BWGI) and basalt weathering grade II (BWGII). The adsorption of Pb2+ using BWGI and BWGII from aqueous solution was studied under various conditions. The uptake of Pb2+ was rapid with maximum adsorption within 90 min for BWGI and 60 min for BWGII. The kinetic of the Pb2+ adsorption was studied using pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models. The kinetics data showed that the adsorption of Pb2+ onto basalt proceeds according to the pseudo-second-order model. The results obtained from adsorption isotherm indicated that the maximum adsorption capacities of Pb2+ were 15.92 and 23.31 mg/g by BWGI and BWGII, respectively. The mean sorption energy (E) obtained from Dubinin-Radushkevich isotherm model indicated that, the adsorption process takes place chemically and the reaction is endothermic. The results suggested that natural basalt, especially, BWGII is suitable as an adsorbent material for adsorption of Pb2+ from aqueous solutions.

Amine functionalized radiation-induced grafted water hyacinth fibers for Pb2+, Cu2+ and Cr3+ uptake

An amine group containing fibrous adsorbent was prepared by reaction of grafted water hyacinth fibers with ethylenediamine. Glycidyl methacrylate (GMA) was grafted onto water hyacinth fibers using gamma radiation induced graft polymerization through simultaneous grafting technique and this was used as base material for producing the amine type adsorbents. The conversion of the epoxy group from GMA into amine group was investigated. The concentration of ethylenediamine solution that gave the highest amine functional group density was 50% by volume in 2-propanol. The amine functionalized water hyacinth fibers were characterized using Attenuated Total Reflectance-Fourier Transformed Infrared Spectroscopy (ATR-FTIR), Thermogravimetric Analysis (TGA), and Energy Dispersive X-ray Spectroscopy (EDX). Information derived from these analyses confirms the successful conversion of the epoxy group. The amine-type adsorbent was evaluated for its uptake of Pb2+, Cu2+ and Cr3+ from aqueous solutions. The initial concentration of the metal ions and pH of the solutions were found to influence the amount of metal ions adsorbed by the amine-type adsorbent. The kinetics of adsorption was observed to follow Lagergren's first order equation. Results of ion sorption studies indicate that gamma radiation-induced grafting and subsequent chemical modification improved the ion sorption behaviour of water hyacinth fibers.

Morphological, transport, and adsorption properties of ethylene vinyl acetate/polyurethane/bentonite clay composites

AbstractThe effect of polyurethane (PU) foam on the morphological and transport properties of ethylene vinyl acetate (EVA) with 9% vinyl acetate and the potential application of 3%bentonite/28.5% PU/68.5% EVA composites fabricated via the melt‐blending method in heavy‐metal extraction from water systems were investigated. EVA did not swell in water, whereas the PU/EVA blend attained a maximum percentage of deionized water uptake of 2.158 mol %. A 3% bentonite/28.5% PU/68.5% EVA composite blend successfully removed 90% of Pb2+ from an aqueous solution with an initial concentration of 30 mg/L, whereas 3% bentonite/97% EVA could only extract 7.323% of Pb2+ ions. Pb2+ adsorption was found to obey the Langmuir adsorption isotherm and pseudo‐second‐order kinetic model. Thermodynamic studies demonstrated that the adsorption was favorable at room temperature and the uptake of Pb2+ was mostly by physical adsorption, as also indicated by the value n = 2.449 (where n is an empirical parameter indicating transport mode) from the Freundlich adsorption isotherm. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Adsorption Behaviour of Ethylene Vinyl Acetate and Polycaprolactone-Bentonite Composites for Pb2+ Uptake

The results presented in this work show that the hydrophobic thermoplastics, namely ethylene vinyl acetate (EVA) and polycaprolactone (PCL), could be good matrices for the synthesis of polymer/bentonite composites via the melt-blending method for the removal of heavy metals from water. The hydrophobic nature of the polymers was countered by using dry Na2SO4 to form large free-volume pores. These pores, formed after the removal of the Na2SO4 by washing, improved the contact ratio between bentonite particles and Pb2+ ions. The composites were able to achieve up to 78% Pb2+ removal at an initial concentration of 200 mg/L in 10 h with a clay loading of 3% (w/w). The results confirmed that the PCL/bentonite composite was more effective and efficient in the adsorption of Pb2+ than the EVA/bentonite composite. The experimental data for both composites followed Langmuir and Freundlich models. The uptake of Pb2+ was found to be a result of a chemical interaction between the heavy metal, silanol (Si–OH) and aluminol (Al–OH) groups. The adsorption of Pb2+ onto the composites was found to follow pseudo-first-order kinetics and the results supported a monomolecular reaction mechanism.

Biosorption of Pb2 + and Cd2 + in a Fixed Bed Column with Immobilised Chorella sp. Biomass

The biosorption of Pb2+ and Cd2+ in a fixed bed column by immobilised Chlorella sp. was characterised in a fixed bed column. Effect of initial concentration of Pb2+ and Cd2+, pH, and pellet size on the biosorption capacity was studied, at laboratory scale, using a factorial experiment design 2(3), in a 10 cm heightx1 cm of diameter continuous flow column packed with immobilised biomass. Equilibrium uptake of Pb2+ and Cd2+, increased with increasing initial metal ion concentration. It was favoured to pH 5, with a pellet of 5 mm of diameter. Langmuir model described the biosorption equilibrium of both metals.The biosorption of each single cation was studied too in a large column (50 cm heightx5 cm of diameter) at bench scale with a range of flow of 40 to 80 mL min(-1). The mass transfer coefficient was determined fitting the experimental data to continuity equations that were discretised in the radial terms with orthogonal collocation method.

Uptake of Pb2+ by a cyanobacterium belonging to the genus Synechocystis, isolated from East Kolkata Wetlands

East Kolkata Wetlands is a conserved wetland utilizing sewage and garbage, generated by Kolkata Municipal Corporation area for cultivation purpose. Cyanobacteria are the photosynthetic prokaryotes having bioremedial capacity. We have isolated a cyanobacterium from the sewage recycling fish-pond of East Kolkata Wetlands. Partial sequence of 16S rDNA gene of the isolated strain showed 100% similarity with that of genus Synechocystis. Isolated strain and Synechocystis sp. PCC6803 survived up to 300 mug ml(-1) Pb(2+ )and growth was completely inhibited at 400 mug ml(-1) Pb(2+). All experiments were carried out with 100 mug ml(-1) Pb(2+) in which growth was the maximum. 91.67% of the total Pb(2+) got adsorbed to the outer surface of the cell and 1% of the total Pb(2+) entered the cell of the isolated strain as estimated by atomic absorption spectrometry, but in Synechocystis sp. PCC6803 72.72% adsorbed and 0.96% penetrated. Intracellular and periplasmic depositions of Pb(2+) were observed in both the strain. A filamentous structure developed outside the cell wall of the isolated cyanobacterium, but very little change was observed in Synechocystis sp. PCC6803. ZiaR-SmtB like regulator gene was expressed in both the strains after Pb(2+) induction. The cDNA sequence of ZiaR of the isolated cyanobacterium shows 100% homology with that of Synechocystis sp. PCC6803. Upon Pb(2+) induction, expression of SOD gene increased. cDNA sequence of the SOD gene from the isolated strain showed 98% homology with that of Synechocystis sp. PCC6803. Enzymatic activity of catalase and SOD was also increased. No DNA damage was monitored upon induction with Pb(2+).