Aqueous Solutions Of Lead Research Articles

ОЦЕНКА СОРБЦИОННЫХ СВОЙСТВ ГРИБОВ ЧАГА (INONOTUS OBLIQUUS) В ОТНОШЕНИИ КАДМИЯ И СВИНЦА

To reduce the toxic load on the body of animals and the accumulation of heavy metals in livestock products, the use of sorbents of various origins is effective. Natural substances, which, along with sorption, have anticarcinogenic, antimutagenic, immunomodulatory properties and antitoxic activity are of particular interest. Sorption properties of the birch fungus Inonotus obliquus (chaga, or chamfered tinder) with respect to cadmium and lead were determined in an experiment on model solutions in order to assess the possibility of its further use as an enterosorbent to reduce the negative effect of heavy metals on the animal body. Under in vitro conditions, the maximum sorption by chaga from aqueous solutions of lead reached more than 95 % of cadmium – up to 89 %. The natural zeolite of the Shivyrtuiskoye deposit was used as a reference preparation. It has been established that the sorption efficiency of both chaga and shivyrtuin with respect to lead is higher than with respect to cadmium. At the same time, chaga sorbed lead worse than shivyrtuin (by 29.4 %), and cadmium more efficiently (by 28.0 %).

Efficient Concentration of PB From Water by Reactions With Layered Alkali Silicates, Magadiite and Octosilicate

AbstractHuman health problems are often related to contamination of the aqueous environment by toxic metal ions. In the present study, two layered alkali silicates (magadiite and octosilicate) were examined to assess removal of Pb2+ from aqueous solutions in terms of quantity and kinetics. The ion-exchange reaction between the silicates and aqueous solutions of lead(II) acetate at various concentrations was examined at room temperature for 24 h. The adsorption isotherms were H-type, showing the strong interactions between Pb2+ and the silicates. The amounts of Pb2+ adsorbed were as much as 1.23 mmol Pb/g magadiite and 2.32 mmol Pb/g octosilicate, which are larger than the reported values for various ion exchangers. They were larger than the theoretical cation exchange capacities (2.2 and 3.7 meq/g for magadiite and octosilicate, respectively), suggesting that the collection of Pb2+ included the precipitation as basic lead salts in addition to the ion exchange. The adsorption isotherms for magadiite and octosilicate fitted the Langmuir equation with correlation coefficients, R2, of 0.9991 and 0.9972, respectively. The adsorption of Pb2+ onto the layered alkali silicates from acidic aqueous solution was examined to obtain smaller amounts of adsorbed Pb2+ (0.32 mmol Pb/g magadiite and 0.34 mmol Pb/g octosilicate), confirming the important role of pH on the surface charge of the layered silicates in terms of ion exchange. The adsorption of Pb2+ reached equilibrium within 5 min for magadiite while it took 60 min for octosilicate. The difference was in the particle morphology; smoother diffusion of Pb2+ was possible through flower-shaped aggregates of particles of magadiite.

Adsorption Isotherms and Kinetics of Pb (II) and Cd (II) Ions onto Carbonised Sugarcane Bagasse

In the present study, the adsorption of Pb (II) and Cd (II) ions from aqueous solution of lead (II) nitrate and cadmium chloride onto carbonized sugarcane bagasse was investigated. The physicochemical attributes of the adsorbent were: bulk density =0.58 g/mL, Ash content =21%, Attrition =31.33% and moisture =0.79%. The effects of adsorption dosage, effect of concentration, effect of ion concentration, effect of adsorbent contact time and effect of pH was discussed and detailed. Batch adsorption experiments revealed that the amount of ion adsorbed decreased with increase in adsorbent dosage; the effect of concentration on ion uptake increased with increase in concentration; there was a rapid increase in amount adsorbed as contact time increased with maximum adsorption reached at 80 minutes before subsequent reduction. The effect of pH showed that there was effective removal of ions at acidic pH than in alkaline pH level. The linearized form of Langmuir model revealed isotherm parameters that confirmed the sorptive capacity of the sugarcane bagasse and thus fit for heavy metal remediation from aqueous solution. Besides, the adsorption isotherm indicated that the adsorption occurred at homogeneous sites and form a monolayer. The Langmuir model was also able to explain the sorption equilibrium with maximum biosorption capacity.

Role of Manglicolous fungi isolated from Indian Sunderban mangrove forest for the treatment of metal containing solution: Batch and optimization using response surface methodology

Abstract Lead and Cadmium are known for their various carcinogen effects in various biotic components. In the present study, manglicolous fungi isolated from the Indian Sunderban region were utilized for the removal of lead and cadmium from its aqueous solution. Six fungal strains were isolated from the water samples collected from the intertidal zone of Jharkhali, an island of Indian Sunderban region, which were then screened for their potentiality for the removal of lead and cadmium. Of all the isolated strain, one fungal strain which was molecularly identified to be Alternaria alternata showed promising result in the removal of lead and cadmium. The removal efficiency of Alternaria alternata from the aqueous solution of Lead and Cadmium were optimized using different conditions like initial concentration of heavy metal, contact time, biomass dose, pH, temperature and salinity. Competitive biosorption capacity of the fungal species were also investigated by mixing the two metal in effluent solution where the removal capacity of each metal ion were reduced due to the presence of other metal ion and also the removal efficiency decreases with increase of competitive metal ion concentration in solution. Further, the removal of these heavy metals were also optimized using Response Surface Methodology (RSM). It was observed that Alternaria alternata could remove 98.27% and 84.64% of lead and cadmium respectively from the initial metal-ion solution. This research indicated that fungi obtained from mangrove growing area of Sunderban region has biosorption potential and can be used to remove heavy metal-ions from the wastewater.

Determination of the Correct Composition of “Hydrous Lead(II) Oxotellurate(IV)” as PbTeO3, Crystallizing as a New Polymorph

In previous studies, it has been reported that the crystalline product precipitated from the reaction of aqueous solutions of lead(II) salts with sodium oxotellurate(IV) is hydrous lead(II) oxotellurate(IV); however, there have been conflicting specifications of the water content, and the crystal structure of the product is yet undetermined. During the present study, it was shown that the precipitated material does not contain any structural water and in fact represents the third modification (denoted as γ-) of PbTeO3, as revealed by thermal analysis, vibrational spectroscopy, single crystal and powder X-ray diffraction. This modification crystallizes in the space group P 1 ¯ with five formula units in the asymmetric unit, comprising off-centred coordination polyhedra around the PbII cations (coordination numbers: 5–7 with Pb-O distances ranging from 2.3–3.0 Å), and trigonal-pyramidal TeO32− units. The thermal behaviour and structural phase transitions of PbTeO3 were investigated by means of temperature-dependent X-ray powder diffraction and complementary thermal analysis measurements. In addition, the crystal structure of β-PbTeO3 was redetermined, and a comparison was made between the three known polymorphs of PbTeO3.

A comparative study of the structure of copper and lead xanthates

XPS, PbL3 and CuK EXAFS, solid state NMR, and EPR techniques are used to study insoluble products formed in the interaction of aqueous solutions of lead(II) nitrate and copper (II) sulfate with potassium nbutylxanthate (KX). The XPS spectra of lead xanthates with the composition PbX2 are similar to those of KX, and interatomic distances of 0.279 nm suggest a nearly ionic character of Pb–S bonds. In copper xanthate precipitating together with dixanthogen (approximately 15 wt.%), the Cu(I)–S bond length is smaller (0.229 nm), and copper coordination number of 2.9 in a composite with dixanthogen increases to 3.3 after its removal by washing with acetone. The XPS spectra indicate the covalent character of the bond and non-equivalence of xanthate radicals. Solid state 1H and 13C NMR spectra as well as the actual absence of metal lines under the measurement conditions demonstrate strong disordering of the structure of xanthates, which is stronger for PbX2 and weakest in CuX after the removal of dixanthogen. EPR reveals sulfur-containing radicals and Cu2+ in CuX, however, their amounts are insignificant and decrease after the washing with acetone. The results of the work are significant for the understanding of the reactivity of xanthates, in particular, under the conditions of flotation of base metal ores.

FACILE SYNTHESIS OF SEMICONDUCTING NANOSIZED 0D AND 2D LEAD OXIDES USING A MODIFIED CO-PRECIPITATION METHOD

Nano-sized lead has many versatile applications that could be applied in daily life. In the current study, we report a comprehensive study for preparation of nanosized lead oxide using the co-precipitation method and optimization of reaction parameters to obtain lead oxide (PbO) nanoparticles with homogeneously distributed size, shape and structure. When aqueous solution of lead (II) acetate reduced with sodium hydroxide at elevated temperatures, alpha form of lead oxide nanoparticles, with spherical shape were achieved. Decreasing the ratio of sodium hydroxide to lead (II) acetate concentration at moderate temperatures resulted with a gradual change in crystal structure from quasi -spherical α-PbO nanoparticles and two dimensional nanoflakes of beta PbO with a thickness below 100 nm was synthesized for the first time. The obtained particles in both α and b forms were characterized by X-ray powder diffraction (XRD), dynamic light scattering equipment (Zetasizer), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Finally, thin layers of freeze-dryer α-PbO and β-PbO particle powder on glass and filter paper were formed by the help of nail polisher and conductivity measurements were performed using four-point probes method. Produced layers β-PbO particles with a below 100 nm showed higher conductivity on both supports as compared to the ones produced from spherical α-PbO nanoparticles. This altered conductivity of the material in the semiconducting zone, which is probably due to a more effective electron transfer facilitated by 2D alignment of the molecules, could rose the potential use of this material in voltaic and catalysis.

Synthesis and study of lead(II) uranate Pb(UO2)2O2(OH)2·H2O

An individual crystalline compound Pb(UO2)2O2(OH)2·(H2O) was obtained by reaction of synthetic schoepite UO3·2.25H2O with an aqueous solution of lead(II) nitrate under hydrothermal conditions. The composition and structure of this compound were determined, and the processes of its dehydration and thermal decomposition were studied by chemical analysis, X-ray diffraction, IR spectroscopy, and thermography.

Square wave voltammetric determination of lead in commercial kohl using a glassy carbon electrode

A simple sensitive square wave voltammetric method for the determination of lead contamination of several kohl samples purchased from Algeria retail stores was developed using glassy carbon electrode. The peak current response of 5 standards aqueous solution of lead in NaNO3 as supporting electrolyte was observed showing a linear calibration curve in the concentration range of 4×10-3 – 2.5×10-4 mol/l of lead. Over this concentration range, the equation obtained from the linear calibration graph for lead is Y = 0.00068 + 0.0093x with a correlation coefficient of r2 = 0.987. Following this step, the potential of an aqueous solution of 12 kohl samples containing 2 M nitric acid solution as supporting electrolyte is then swept in the same range of potential (-400 to -700 mV). The amount of lead is then deduced using the linear calibration graph for lead. The results showed up to 52.14% of lead present in kohl, this concentration was over the safe limits of lead set by the world health organization standards. However; only five commercial samples of kohl tested contained less than 0.001% lead. Complete recovery of lead from the kohl was obtained by simple nitric acid digestion.Keywords: Square wave voltammetry, kohl, lead, surma.

Removal of lead from aqueous solutions by adsorption with surface precipitation

An activated carbon from Coconut (Cocos nucifera) shells was prepared by physical activation with carbon dioxide and water vapor. The activated carbon obtained has a surface area of 1058 m2 g−1 and such a high micropore volume of 0.49 cm3 g−1. This carbon was studied for the removal of lead from water. Sorption studies were performed at 30 °C, at different pH and adsorbent doses, in batch mode. Lead precipitation was observed on the surface of the activated carbon. Maximum adsorption occurred at pH 9 for an adsorbent dose of 2 g L−1. Kinetic studies, at the initial concentration of 150 mg L−1 of lead, pH 5 and an adsorbent dose of 1 g L−1, yielded an equilibrium time of 50 h for this activated carbon. The kinetic data were modeled with the pseudo first order, the pseudo second order and the Bangham models. The pseudo second order model fitted the data well. The sorption rate constant (7 × 10−4 mol−1 Kg s−1) and the maximum amount of lead adsorbed (0.23 mol kg−1) are quite good compared to the data found in literature. Sorption equilibrium studies were conducted in a concentration range of lead from 0 to 150 mg L−1. In an aqueous lead solution with an initial concentration of 30 mg L−1, at pH 5, adsorbent dose 1 g L−1, activated Coconut shell carbon removed at equilibrium 100 % of the heavy metal. The equilibrium data were modeled with the Langmuir and Freundlich equations, of which the former gave the best fit. The Langmuir constants Qmax eq (0.23 mol kg−1) and KL (487667 L mol−1) are in good agreement with literature. XPS studies identified adsorbed species as lead carbonates and/or lead oxalates and precipitates as lead oxide and/or lead hydroxide on the activated carbon surface. The Coconut shell activated carbon is a very efficient carbon due to its high surface area, to the presence of many micropores on its surface and to the presence surface groups like hydroxyls promoting adsorption in the porous system and lead crystal precipitation on the activated carbon surface.

Calcium phosphate based materials starting from calcium carbonate and orthophosphoric acid for the removal of lead(II) from an aqueous solution

Calcium phosphates starting from calcium carbonate and orthophosphoric acid as unconventional and low cost initial reactants were investigated in the removal from aqueous solution of lead(II) as model heavy metal. Sorbent in gel form, which was directly obtained from the reaction of calcium carbonate powder and orthophosphoric acid, and sorbent in powder form, which was obtained by filtration and drying of the gel at room temperature showed the highest reactivity for the removal of lead(II). The sorption capacity could reach up to 1226mg of lead(II) per gram of powder sorbent. On the other hand, the conventional drying overnight at 105°C decreased the reactivity of the sorbent in powder form. The intermediates of the reaction between calcium carbonate and orthophosphoric acid, including brushite (CaHPO4·2H2O), monetite (CaHPO4) and MCPM (Ca(H2PO4)2·H2O) were found to be more active than hydroxyapatite (Ca10(PO4)6(OH)2) which was the final stable product of the reaction between calcium carbonate and orthophosphoric acid. Lead hydroxyapatite (Pb10(PO4)6(OH)2) was the main crystalline phase formed from the contact of calcium phosphate based sorbents with lead(II) nitrate solution. It was only formed at the external surface or surface of open-pores of calcium phosphate particles, highlighted by SEM characterization. The results obtained open new prospects for the design of efficient orthophosphate-based sorbents for the removal of lead(II) and other heavy metals from liquid effluents.

Comparative Study of Lead Removal by Extracts of Spinach, Coffee, and Tea

The use of tea and coffee for the removal of heavy metal from aqueous lead solutions has been reported. However, those studies were limited to expended dry biomass of coffee and tea and the lead concentration in those studies range from 10 - 100 ppm of aqueous lead solution. This study compared the effectiveness of aqueous extracts of instant coffee (IC), coffee ground (CG), coffee bean (CB), Lipton tea (Tea), and spinach puree (SP) in removing lead from 1300 PPM of aqueous lead solution. After 24 hr of agitation at room temperature followed by centrifugation, the lead concentration (in ppm) in the liquid from each reaction tube was analyzed using EPA Method 6010 (Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES)). The results suggest that the order of lead removal was Spinach (99%) > Instant coffee (95%) >Tea (91%), > CG (62%) > CB (59%). In comparing the brewed versus the boiled extracts, the results demonstrated that temperature of the aqueous extract affected the lead removal potential of coffee and tea in decreasing order: IC (95%:79%), > Tea (91%:88%) > CG (62%:53%) > CB (59%:53%).

In Situ Transmission Electron Microscopy of Lead Dendrites and Lead Ions in Aqueous Solution

An ideal technique for observing nanoscale assembly would provide atomic-resolution images of both the products and the reactants in real time. Using a transmission electron microscope we image in situ the electrochemical deposition of lead from an aqueous solution of lead(II) nitrate. Both the lead deposits and the local Pb(2+) concentration can be visualized. Depending on the rate of potential change and the potential history, lead deposits on the cathode in a structurally compact layer or in dendrites. In both cases the deposits can be removed and the process repeated. Asperities that persist through many plating and stripping cycles consistently nucleate larger dendrites. Quantitative digital image analysis reveals excellent correlation between changes in the Pb(2+) concentration, the rate of lead deposition, and the current passed by the electrochemical cell. Real-time electron microscopy of dendritic growth dynamics and the associated local ionic concentrations can provide new insight into the functional electrochemistry of batteries and related energy storage technologies.

Influence of the Surface Properties of the Bois Carré Seeds Activated Carbon for the Removal of Lead From Aqueous Ssolutions

<p>An activated carbon from Bois carré (Citharexylum Fruticosum L.) seeds was prepared by chemical activation with phosphoric acid. The activated carbon obtained has a surface area of 594 m<sup>2</sup>/g and a high content of acid groups of 3.44 mmol.g<sup>-1</sup>. This carbon was studied for the removal of lead from water. Sorption studies were performed at 30 °C at different pH and adsorbent doses, in batch mode. Maximum adsorption occurred at pH 7 for an adsorbent dose of 1g/L. Kinetic studies, at the initial concentration of 150 mg/L of lead, pH 5 and an adsorbent dose of 1 g/L, yielded an equilibrium time of 30 h for this activated carbon. The kinetic data were modelled with the pseudo first order, the pseudo second order and the Bangham models. The pseudo second order model fitted the data well. The sorption rate constant (2.10<sup>-3</sup> mol<sup>-1</sup>.Kg.s<sup>-1</sup>) and the maximum amount of lead adsorbed are quite good (0.18 mol.kg<sup>-1</sup>) compared to the data found in literature. Sorption equilibrium studies were conducted in a concentration range of lead from 0 to 150 mg/L, at pH 5, adsorbent dose 1 g/L. In an aqueous lead solution with an initial concentration of 30 mg/L, activated Bois carré seed carbon removed (at equilibrium) 48% of the heavy metal. The equilibrium data were modelled with the Langmuir and Freundlich equations, of which the latter gave the best fit. The Freundlich constants n (3.76 L.mol<sup>-1</sup>) and Kf (1.06 mol.kg<sup>-1</sup>) are in good agreement with literature. The Bois carré seed activated carbon is a very efficient carbon in terms of the metal amount adsorbed per unit of surface area (0. 06 m<sup>2</sup>/g). This good result is due to the presence of many active acid sites on the surface of this activated carbon.</p>

The Cause of Highly Efficient Lead Removal with Silica Spheres Modifying the Surface by a Base Catalyst

The surface of silica spheres was modified using 3-mercaptopropyl trimethoxysilane (MPTMS) with an acid catalyst and a base catalyst. Large aggregation was observed for the spheres modified with an acid catalyst. The spheres modified with an acid catalyst (ACS) show aggregated spheres. However, no aggregation was observed for the spheres modified with a base catalyst (BCS). Aqueous lead solutions with 625 and 1663 ppm were used to test the removal of lead ions. Various amounts of modified spheres were treated to the lead solutions. The lead concentration drastically decreased with the increase of the amount of the spheres. The lead removal efficiency for the BCS is much more effective than that of ACS. For more-quantitative analysis of the residual lead concentration, inductive coupled plasma–mass spectrometry (ICP-MS) was employed. As the amount of spheres increased, the lead concentration drastically decreased. The lowest concentration of 1.2 ppb was obtained, which indicates that the lead ion can be co...

Lead hexacyanoferrate(II) tetrahydrate: Crystal structure, FTIR spectroscopy and thermal decomposition studies

Pb2[Fe(CN)6]·4H2O was synthesized by mixing aqueous solutions of lead(II) nitrate and potassium ferrocyanide. Its crystal structure was solved ab initio from synchrotron powder X-ray diffraction data using the direct methods and refined by the Rietveld method. Thermal analysis (TGA and DTA), Fourier Transform Infrared Spectroscopy (FTIR) and scanning electron microscopy (SEM) studies were also used for the solid state characterization of this compound and its decomposition products. The complex crystallizes in the monoclinic crystal system, space group P21/n. The Fe2+ cation is octahedrally coordinated to six cyano groups, and the Pb2+ cation is penta-fold coordinated to three N atoms from CN ligands and two O atoms from coordinated water molecules. The most important peculiarity of the structure of this complex is the occurrence of water bridges linking two neighboring Pb2+ cations. An unusual Fe–CN–Pb(H2O)2–Pb–NC–Fe linkage alternates with a usual Pb–NC–Fe one. Zeolitic water molecules are also observed in the structure; they are located in small channels in the structure and they are hydrogen bonded to coordinated water molecules forming a cumulus. Coordinated water and zeolitic water molecules in this complex can be removed without affecting the hexacyanometallate framework. The thermal decomposition in air to produce Pb2Fe2O5 and PbO as final products has been studied by thermogravimetric and differential thermal analysis, FTIR spectroscopy and laboratory powder X-ray diffraction. The crystallite size and morphology of the complex and its thermal decomposition products were evaluated by SEM.

Removal of Chromium and Lead from Industrial Wastewater Using Effective Microorganisms (EM) Technology

In this research an attempt is made on the ability of aerobic treatment of synthetic solutions containing lead and chromium using effective microorganisms within the reactor. To achieve the desired objectives of the research, synthetic aqueous solutions of lead and chromium was used in the concentration of chromium and lead ions of 5, 10,50 and 100 mg / l .The work was done at constant pH equal to 4.5 and temperature of 30 ± 1 º C. Effective microorganisms solutions was added to the reactor at Vol.% of 1/50 ,1/100 ,1/500 and 1/1000, with retention time was 24 hours to measure the heavy metals concentration the atomic absorption device was used. The experimental results showed that each 1mg / l of lead and chromium ions need 24 mg of effective microorganisms to achieve removal of 92.0% and 82.60% for lead and chromium respectively. Increasing the concentration of effective microorganisms increases the surface of adsorption and thus increasing the removal efficiency. It is found that the microorganisms activity occur in the first five hours of processing and about 94% of adsorption capacity of biomass will take place. It is also found the selectivity of microorganisms to lead ions is higher than for chromium ions.

Enhanced effects of nonisotopic hafnium chloride in methanol as a substitute for uranyl acetate in TEM contrast of ultrastructure of fungal and plant cells

This ultrastructural study showed that nonisotopic methanolic hafnium chloride and aqueous lead solution was an excellent new electron stain for enhancing TEM contrasts of fungal and plant cell structures. The ultrastructural definition provided by the new stain was often superior to that provided by conventional staining with uranyl acetate and lead. Definition of fine ultrastructure was also supported by quantitative data on TEM contrast ratios of organelles and components in fungal and plant cells. In particular, polysaccharides, which were localized in cell walls, glycogen particles, starch grains, and plant Golgi vesicle components, were much more reactive to the new stain than to the conventional one. The new nonisotopic stain is useful for enhancing the contrast of ultrastructure in biological tissues and is a safer alternative to uranyl acetate.

Thermodynamical and analytical evidence of lead ions chemisorption onto Pimenta dioica

Residue of allspice (Pimenta dioica L. Merrill) obtained as a by-product from the hydro-distillation oil process, has been studied as a low cost biosorbent for removing lead (II) ion from water solution at different temperatures. Batch experiments were performed with aqueous lead solutions of concentration 25mgL−1, at pH 5 and adsorbent dosage 1.0g biosorbent per liter of solution. According to pseudo-second order kinetic model, the maximum adsorption capacity was 22.37mgg−1 of Pb (II) on residue of allspice (RA). This value was reached at 90min and temperature of 308K. Langmuir, Freundlich and Dubinin–Radushkevich (D–R) adsorption isotherm models were applied as an attempt to mathematically represent adsorption data. These three equations were found to be applicable to this adsorption system, in terms of relatively high regression values. Thermodynamic parameters showed that the adsorption of lead (II) onto RA was feasible, spontaneous, and endothermic under the studied conditions. The elemental analysis from scanning electron microscopy (SEM) before and after the contact showed that lead was adsorbed by RA. Diffusion results, the value of the free energy E (kJmol−1), XPS and FTIR analysis confirmed that the lead (II) adsorption process onto RA was controlled by chemisorption.

Waste Biomass from Marine Environment as Arsenic and Lead Biosorbent

This paper deals with arsenic and lead biosorption by different waste biomasses coming from the marine environment. Shoreline seaweeds and seagrasses were used to adsorb metals from aqueous solutions, under different pH. Experimental tests were performed in order to study the equilibrium of biosorption with suspended biomass. The obtained results confirmed the possibility of using marine macrophyte biomass for heavy metal biosorption and evidenced a strong dependence of lead and arsenic uptake on the macrophyte structure. Brown algae were found to be the best sorbents for lead with a maximum observed lead uptake of 140 mg/g; green algae showed a maximum lead uptake in the range 50-70 mg/g; red algae were the worst lead sorbent, in the investigated experimental conditions, with a maximum lead uptake in the range 10-40 mg/g. As concerns arsenic, the macrophytes had in general good sorption abilities when compared with those of activated carbon. Furthermore red algae, that for lead were not effective, resulted to be the best sorbents for arsenic. This was explained by a different speciation in aqueous solution of lead (II), that is cationic with respect to arsenic(V), that is anionic.