Adsorption and desorption of phosphate in some semi-arid tropical Indian Vertisols

Adsorption and desorption of phosphorus in soils are among the key processes governing its availability to crops. There have been very few studies on the phosphorus adsorption and desorption characteristics of Vertisols. The P adsorption and desorption characteristics of four Vertisols belonging to three agriculturally important soil series were studied. The amounts of P adsorbed by the soils at 0.2µg ml^–1 equilibrium solution P concentration was low and ranged from 34.3 to 79.5µg g^–1 soil. The phosphate adsorption was very well described by Langmuir and Freundlich isotherms. The P adsorbed by a Vertisol (BR-1) fertilized with different rates of P in the previous season (0, 10, 20 and 40 kg P ha^–1) was similar (34.3–41.3µg g^–1 soil) indicating little effect of fertilization on P adsorption. The correlation studies indicated that the DTPA-extractable Fe was the most important factor accounting for P adsorption in these soils. Clay and CaCO₃ content were found to be relatively less important factors affecting P adsorption in the soils studied.The capacity of the two extractants and EUF (electro-ultrafiltration) to desorb the adsorbed P followed the order: EUF (400V, 80°C)>sodium bicarbonate>EUF (200V, 20°C)>calcium chloride. The average amounts of P desorbed from the four Vertisols using these methods were 74, 63, 50, and 3% respectively of the adsorbed P. In the Begamganj soil, the amount of P desorbed by EUF (400V, 80°C) exceeded 100%, indicating that all of the adsorbed P was desorbable including some native P.In conclusion the results of our study show that the Vertisols studied have low phosphate adsorption capacity and that the P they adsorbed is easily desorbable.Approved for publication as Journal Article No. 983 by International Crops Research Institute for the Semi-Arid Tropics (ICRISAT).     

Reuse of a waste adsorbent poly(AAc/AM/SH)‐Cu superabsorbent hydrogel,for the potential phosphate ion removal from waste water: Matrix effects,adsorption kinetics,and thermodynamic studies

The most commonly applied methods for the treatment of used adsorbents is to recover them in acid/alkaline medium or direct enflame them. This work dealt with a new potential and economic method to utilize a waste adsorbent. Poly(AAc/AM/SH) superabsorbent hydrogels have proved to be a good adsorbent for Cu²⁺ ions and after adsorption the hydrogels were recovered in acid medium. In this report, the Cu²⁺ ion adsorbed hydrogel has not undergone any regeneration process and applied directly to phosphate ion adsorption. The Cu²⁺ ions‐loaded poly(AAc/AM/SH) hydrogels, were stable within a wide pH range and suitable for phosphate ion adsorption. The factors affecting the phosphate adsorption, such as pH, ionic strength, contact time, temperature, initial concentration of the phosphate ion, and coexisting ions were systematically investigated. The phosphate adsorption was highly pH dependent; and the maximum adsorption of 87.62 mg/g was achieved at pH 6.1. The adsorption data fitted the Langmuir adsorption isotherm better than the Freundlich isotherm. The concomitant anions show profounder adverse influence on phosphate ion adsorption of poly(AAc/AM/SH)‐Cu hydrogel and the effect follows the order citrate > sulfate > bicarbonate > chloride > nitrate. The thermodynamic parameters including ΔH°, ΔG°, and ΔS° for the adsorption processes of phosphate ions on the gel were also evaluated, and the negative ΔG° and ΔH° confirmed that the adsorption process was spontaneous and exothermic. The adsorption kinetic results suggest that the adsorption process was well described by the pseudo second‐order kinetic model. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Characteristics of phosphate adsorption on ferric hydroxide synthesized from a Fe<Subscript>2</Subscript>(SO<Subscript>4</Subscript>)<Subscript>3</Subscript> aqueous solution discharged from a hydrometallurgical process

Ferric hydroxide adsorbent was prepared by a chemical treatment process with H₂O₂, NaOH, and aeration from a Fe₂(SO₄)₃ aqueous solution as a side product discharged from the hydrometallurgical process used to extract neodymium. The ferric hydroxide was used as an adsorbent to prevent eutrophication in water. At the time of synthesis, the most important process variable is the pH condition, which, in this experiment, was changed from pH 3 to 13. The cost of synthesizing ferric hydroxide was sharply reduced by using ferric sulfate, which is considered a side product of the aforementioned hydrometallurgical process, as a starting material, and an adsorbent with high adsorption ability was prepared by controlling the pH level. Microstructural characterization of the synthesized ferric hydroxide revealed particles with a specific surface area of 194.2 m²/g and an average pore diameter of 2.66 nm at pH 6 and 298 K. A column-type packed-bed adsorption experiment was conducted under the following conditions: a flow rate of 0.567 BV/min (3.2 mL/min), 298 K, and atmospheric pressure. The results of the adsorption performance test indicated that the adsorption efficiency of phosphate at concentrations of 10 ppm was 100% at a flow rate of 0.567 BV/min within a contact time of 2 min, and the maximum adsorption capacity for phosphate ions was 65 mg/g.     

Root-secreted Allelochemical in the Noxious Weed <Emphasis Type="Italic">Phragmites Australis</Emphasis> Deploys a Reactive Oxygen Species Response and Microtubule Assembly Disruption to Execute Rhizotoxicity

Phragmites australis is considered the most invasive plant in marsh and wetland communities in the eastern United States. Although allelopathy has been considered as a possible displacing mechanism in P. australis, there has been minimal success in characterizing the responsible allelochemical. We tested the occurrence of root-derived allelopathy in the invasiveness of P. australis. To this end, root exudates of two P. australis genotypes, BB (native) and P38 (an exotic) were tested for phytotoxicity on different plant species. The treatment of the susceptible plants with P. australis root exudates resulted in acute rhizotoxicity. It is interesting to note that the root exudates of P38 were more effective in causing root death in susceptible plants compared to the native BB exudates. The active ingredient in the P. australis exudates was identified as 3,4,5-trihydroxybenzoic acid (gallic acid). We tested the phytotoxic efficacy of gallic acid on various plant systems, including the model plant Arabidopsis thaliana. Most tested plants succumbed to the gallic acid treatment with the exception of P. australis itself. Mechanistically, gallic acid treatment generated elevated levels of reactive oxygen species (ROS) in the treated plant roots. Furthermore, the triggered ROS mediated the disruption of the root architecture of the susceptible plants by damaging the microtubule assembly. The study also highlights the persistence of the exuded gallic acid in P. australis’s rhizosphere and its inhibitory effects against A. thaliana in the soil. In addition, gallic acid demonstrated an inhibitory effect on Spartina alterniflora, one of the salt marsh species it successfully invades. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Adsorption of phosphate species on poly-oriented Pt and Pt(1 1 1) electrodes over a wide range of pH

The adsorption of phosphate anions from phosphate solutions at poly-oriented and single-crystal platinum electrodes, primarily Pt(1 1 1), was studied over a wide range of pH by cyclic voltammetry. The features observed at the poly-oriented Pt electrode in phosphate solution may be related to the different crystalline facets, the (1 1 1) orientation presenting the most significant behavior in terms of phosphate adsorption. On the reversible hydrogen electrode (RHE) scale, the phosphate adsorption strength decreases with increasing alkalinity of the solution. Qualitatively, three different pH regions can be distinguished. At pH < 6 only a broad reversible peak is observed, corresponding to the adsorption of H₂PO₄⁻ and further deprotonation to adsorbed HPO₄⁻. For 6 < pH < 11 a butterfly feature followed by one or two anodic peaks (depending on scan rate) is observed, ascribed to the adsorption of HPO₄⁻ followed by its subsequent deprotonation to adsorbed PO₄³⁻. The splitting into two or three voltammetric features, and the irreversibility of the two features at more positive potential, is ascribed to the deprotonation reaction leading to a surface species (i.e. phosphate) which needs to change its surface coordination. At pH > 11 a reversible pre-wave and a sharp spike are observed, ascribed to the co-adsorption of phosphate and hydroxide.     

Hydrolysis of aluminium on weakly acidic organic exchangers: Implications for phosphate adsorption

In contrast to its behaviour on soil clays and in aqueous solution, aluminium is more extensively hydrolysed between pH3 and 4.5 on organic exchangers because the weakly acidic carboxyl groups appear to act as sinks for the protons released by hydrolysis and polymerization of the Al(H₂O) ₆ ³⁺ ions. In consequence, the basicity (measured by the OH/Al mole ratio) of Al adsorbed on samples of acid peat, humic acid and Amberlite IRC-50 resin was closely correlated with the apparent pK_a of the acid groups. The amount of phosphate adsorbed depended not only on the amount of Al adsorbed but also on the basicity of the adsorbed Al. Phosphate and OH^– ions competed for Al on the exchange sites with the result that the P/Al mole ratio on the exchanger was inversely related to the basicity of the adsorbed Al. Once adsorbed, the Al was quite stable and P adsorption on the Al-exchanger was unaffected by a rise in pH from 4.5 to 6.4.     

Studies on the Adsorption of Traces of Zirconium on Manganese Dioxide from Acid Solutions

Abstract

The adsorption of zirconium on manganese dioxide from nitric and perchloric acid solutions has been investigated at different concentrations of electrolyte, adsorbent, and adsorbate. The effect of other cations and anions on adsorption has been studied. Fluoride, citrate, oxalate, molybdate, tartrate, carbonate, phosphate, Fe(III), Sr(II), Zn(II), Cr(III), and Mg(II) drastically reduce adsorption. Adsorption of other metal ions on the oxide has been measured under identical conditions. Based on these data, separation of zirconium from a number of elements, including cobalt, zinc, caesium, neodymium and lutetium, can be achieved. Zirconium adsorption follows Freundlich's equation C _Ads = AC ^1/n Bulk with the values of 1/n = 0.92 and A = 40 mmol/g. Thus manganese dioxide can be used for the separation and preconcentration of zirconium from dilute solutions.     

Adsorption off Lauryl Sulfate from Electrolyte Solutions on Cobalt Hydroxide

Abstract

The adsorption of lauryl sulfate on cobalt(II) hydroxide from solutions of inorganic salts has been found to change as follows: without salt ≥ chloride ≥ bromide ≥ nitrate ≥ sulfate ≥ phosphate Adsorption in the presence of acids increases in the following series: without acid ≥ hydrochloric ≥ sulfuric ≥ phosphoric, and is higher than in the presence of salts. The surface concentration of lauryl sulfate adsorbed from a suspension without electrolyte is about 0.9 (μmol/ m². The surface coverage of hydroxide by lauryl sulfate is about 1/5 of a monolayer, but it decreases in the presence of electrolyte. The law of mass action was applied to characterize the effect of solution composition on the adsorption of lauryl sulfate on cobalt(II) hydroxide.     

Ability of iron(III)‐loaded carboxylated polyacrylamide‐grafted sawdust to remove phosphate ions from aqueous solution and fertilizer industry wastewater: Adsorption kinetics and isotherm studies

Iron(III)‐loaded carboxylated polyacrylamide‐grafted sawdust was investigated as an adsorbent for the removal of phosphate from water and wastewater. The carboxylated polyacrylamide‐grafted sawdust was prepared by graft copolymerization of acrylamide and N,N′‐methylenebisacrylamide onto sawdust in the presence of an initiator, potassium peroxydisulfate. Iron(III) was strongly attached to the carboxylic acid moiety of the adsorbent. The adsorbent material exhibits a very high adsorption potential for phosphate ions. The coordinated unsaturated sites of the iron(III) complex of polymerized sawdust were considered to be the adsorption sites for phosphate ions, the predominating species being H₂PO ions. Maximum removal of 97.6 and 90.3% with 2 g L^?1 of the adsorbent was observed at pH 2.5 for an initial phosphate concentration of 100 and 250 μmol L^?1, respectively. The adsorption process follows second‐order kinetics. Adsorption rate constants as a function of concentration and temperature and kinetic parameters, such as ΔG^±, ΔH^±, and ΔS^±, were calculated to predict the nature of adsorption. The L‐type adsorption isotherm obtained in the sorbent indicated a favorable process and fitted the Langmuir equation model well. The adsorption capacity calculated by the Langmuir adsorption isotherm gave 3.03 × 10^?4 mol g^?1 of phosphate removal at 30°C and pH 2.5. The isosteric heat of adsorption was also determined at various surface loadings of the adsorbent. The adsorption efficiency toward phosphate removal was tested using industrial wastewater. Different reagents were tested for extracting phosphate ions from the spent adsorbent. About 98.2% of phosphate can be recovered from the adsorbent using 0.1M NaOH. Alkali regeneration was tried for several cycles with a view to recover the adsorbed phosphate and also to restore the adsorbent to its original state. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2541–2553, 2002     

Synthesis of mesoporous niobium oxophosphate using niobium tartrate precursor by soft templating method

Mesoporous niobium oxophosphate (NBP) with high specific surface area (427 m²/g) and narrow pore size distribution (3–15 nm) has been prepared using aqueous solution of niobium tartrate complex, diammonium hydrogen phosphate as precursors and cationic surfactant, tetradecyl trimethylammonium bromide (TTBr) as an organic template. The synthesized material has been characterized by simultaneously recorded thermogravimetric and differential thermal analysis (TG–DTA), fourier transformed infrared spectroscopy (FTIR), high and low angle X-ray diffraction (XRD), N₂ adsorption–desorption isotherms, high resolution transmission electron microscopy (HRTEM), ³¹P solid state magic angle spinning nuclear magnetic resonance (³¹P MASNMR) spectroscopy and energy dispersive X-ray (EDX) analysis. HRTEM and XRD confirm the formation of mesoporous structure and HRTEM image indicates the formation of wormhole-like mesopores in the synthesized sample. The interaction of pyridine with niobium oxophosphate has been investigated by means of adsorption infrared spectroscopy (FTIR) which shows that both Brönsted and Lewis acid sites are present on the surface of niobium oxophosphate.     

ESR study of paramagnetic sites in sulfated zirconia

ESR spectroscopy was used to investigate paramagnetic sites in sulfated zirconia. Catalysts derived from zirconium oxide and zirconium hydroxide were studied. It was demonstrated that paramagnetic sites assigned to near-surface F-centers were formed during activation at temperatures above 573 K. The catalyst derived from zirconium hydroxide shows after activation at 873 K two types of paramagnetic sites: F-centers and Zr³⁺ sites. Both F-centers and Zr³⁺ sites in this catalyst form complexes with reagents upon n-butane or hydrogen adsorption at range of 423–523 K in contrast to paramagnetic sites of the oxide-derived catalyst. This revised version was published online in July 2006 with corrections to the Cover Date.     

In situ STM study of the effect of chlorides on the initial stages of anodic oxidation of Cu(111) in alkaline solutions

In situ electrochemical scanning tunneling microscopy (STM) has been applied to study the mechanisms of growth of passive layers on Cu(111) in NaOH solutions in the presence of chlorides. For [Cl⁻]/[OH⁻]=0.01, the same ordered precursor phase of adsorbed OH is observed in the underpotential region of oxidation as in Cl⁻-free solutions. Atomically resolved images reveal the structure of the reconstructed topmost metal plane and the threefold hollow adsorption site of the hydroxide. The induced reconstruction causes the ejection of Cu atoms that contribute to the observed lateral growth of the terraces and to the formation of 2D Cu ad-islands in the final stages of the adsorption process. For [Cl⁻]/[OH⁻]=0.1, threadlike nanostructures resulting from the reaction of the ejected Cu atoms with chlorides are formed before agglomeration with the 2D Cu ad-islands formed in the final stage of the hydroxide adsorption process. For [Cl⁻]/[OH⁻]=10, the step edges, which are normally the preferential sites of the reaction with hydroxide, are blocked by the formation of non-ordered surface chloride complexes. Hydroxide adsorption still predominates the surface reaction on the terraces but the 2D ad-islands form immediately due to the blocking of the step edges. In the potential range of Cu(I) oxide formation, crystalline Cu(I) oxide layers are formed with a high density of steps and (111) terraces. Their step edges are rougher in the presence of chlorides which indicates a Cl⁻-enhanced localized dissolution reaction of the oxide layers at step edges.     

Adsorption of glucosinolates to metal oxides, clay minerals and humic acid

Glucosinolates are thioglucosides produced by plants belonging to the Capparales order. Glucosinolates can upon hydrolysis be transformed into a variety of bioactive compounds with a potential to serve as naturally produced pesticides. This paper presents results on the adsorption of prop-2-enyl and benzyl glucosinolate to two metal oxides (amorphous aluminium hydroxide and goethite), two clay minerals (kaolinite and montmorillonite) and to humic acid at different initial concentrations and at pH 4 and 8. The results show that the glucosinolates are weakly adsorbed to the variable-charge minerals with K_d ranging from 0.00 to 1.85 L kg^− 1 and that adsorption was higher at pH 4 than 8 indicating that adsorption takes place by electrostatic interactions between the negatively charged glucosinolates and positive sites on the minerals. On the humic acid higher K_d values were observed for prop-2-enyl glucosinolate (7.22 and 12.3 L kg^− 1), indicating that hydrophobic interactions may take place between the glucosinolate and humic acid. On the montmorillonite anion exclusion was observed as an effect of the negatively charged glucosinolates being repelled from the negatively charged montmorillonite surface. Thus glucosinolates will be very mobile in the soil environment with the potential of leaching to ground and surface waters where the toxic hydrolysis products may be formed.     

Adsorption and binding of the transgenic plant proteins, human serum albumin, β-glucuronidase, and Cry3Bb1, on montmorillonite and kaolinite: Microbial utilization and enzymatic activity of free and clay-bound proteins

Human serum albumin (HSA), β-glucuronidase (GUS), and the Cry3Bb1 protein from Bacillus thuringiensis subsp. kumamotoensis are expressed by genetically-modified plants. Commercial samples of these proteins adsorbed and bound rapidly on the clay minerals, kaolinite (K) and montmorillonite (M). Adsorption increased as the concentration of protein increased and then reached a plateau. The greatest amount of adsorption and binding occurred with the Cry3Bb1 protein, of which there was no desorption: 6.7 ±0.21 μg adsorbed and bound μg^− 1 of M; 2.1 ± 0.39 μg adsorbed and bound μg^− 1 of K. With GUS, 2.2 ± 0.29 μg adsorbed and 1.7 ±0.21 μg bound μg^− 1 of M; 1.5 ± 0.28 μg adsorbed and 1.0 ± 0.03 μg bound μg^− 1 of K. HSA was adsorbed and bound the least: 1.2 ±0.04 μg adsorbed and 0.8 ± 0.05 μg bound μg^− 1 of M; 0.4 ± 0.05 μg adsorbed and 0.4 ± 0.03 μg bound μg^− 1 of K. However, X-ray diffraction analyses indicated that only HSA intercalated M, and none of the proteins intercalated K, a nonswelling clay. When bound, the proteins were not utilized for growth by mixed cultures of soil microorganisms, whereas the cultures readily utilized the free (i.e., not adsorbed or bound) proteins as sources of carbon and energy. The enzymatic activity of GUS was significantly enhanced when bound on the clay minerals. These results indicated that recombinant proteins expressed by transgenic plants could persist and function in soil after release in root exudates and from decaying plant residues as the result of the protection provided against biodegradation by binding on clay minerals.     

Inhibition by tween-85 of the corrosion of cold rolled steel in 1.0?M hydrochloric acid solution

The inhibition effect of tween-85 on the corrosion of cold rolled steel (CRS) in 1.0 M hydrochloric acid (HCl) was studied by weight loss and potentiodynamic polarization methods. The results show that tween-85 is a good inhibitor in 1.0 M HCl and its maximum inhibition efficiency (IE) is 92% at very low concentration. Its adsorption obeys the Langmuir adsorption isotherm equation. The thermodynamic parameters of adsorption enthalpy (ΔH ⁰), adsorption free energy (ΔG ⁰) and adsorption entropy (ΔS ⁰) were calculated and discussed. Polarization curves show that tween-85 acts as a mixed-type inhibitor in hydrochloric acid. IE values obtained from weight loss and polarization are consistent. The adsorbed film on a CRS surface containing an optimum dose of tween-85 was investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM). An inhibitive mechanism is proposed from the viewpoint of adsorption theory.     

The adsorption of sulphate, hydrogenchromate and dihydrogenphosphate anions on surfactant-modified clinoptilolite

The adsorption of sulphate, hydrogenchromate and dihydrogenphosphate anions on surfactant-modified clinoptilolite (SMC) was investigated. The SMCs were prepared by the adsorption of cis-1-aminoctadecen-9 (oleylamine) on both modified and unmodified natural clinoptilolite tuff. The properties of the modified clinoptilolite samples, such as cation type, structure of the zeolite framework and ECEC value, determined the mechanism of oleylamine adsorption, and consequently anion adsorption on the external clinoptilolite surface. According to the strength of the anion adsorption, two groups of SMCs could be distinguished: strong and weak anion adsorbents. Strong anion adsorbents were obtained by oleylamine adsorption on H⁺-clinoptilolites by protonation of the –NH₂ groups. This mechanism of oleylamine adsorption resulted in the surface precipitation mechanism of anion adsorption being the dominant mechanism. The oleylamine derivatives of Ca- and Na-clinoptilolite were weak anion adsorbents. Oleylamine is adsorbed on Ca- and Na-clinoptilolite by hydrogen bonding, thus yielding insufficient adsorption sites for anions. Hydrogenchromate and dihydrogenphosphate anions were nevertheless adsorbed on these SMCs by interaction with oleylamine. The experiments of anion adsorption on various oleylamine loaded SMCs confirmed the existence of two types of anion adsorption sites and showed that excess oleylamine did not significantly influence the anion adsorption in the investigated concentration range. The kinetic results showed that SO₄²⁻ and H₂PO₄⁻ adsorptions were slow processes while HCrO₄⁻ adsorption was completed in a few minutes.     

Zirconia nano-powders with controllable polymorphs synthesized by a wet chemical method and their phosphate adsorption characteristics & mechanism

Adsorption is a simple and efficient phosphorus removal method used to control the eutrophication of water bodies. A simple and gentle atmospheric pressure hydrothermal method by adjusting the dosage of ammonium chloride and sodium hydroxide was used to synthesize amorphous, monoclinic, and tetragonal zirconia nano-powders with high specific surface areas (383.91 m²/g, 330.01 m²/g, and 234.36 m²/g) and particle size of about 40 nm for phosphate adsorption. When pH = 6.3, the phosphate adsorption capacity of the amorphous monoclinic phase and the tetragonal phase respectively reached 102.58 mg P/g, 68.11 mg P/g, and 37.25 mg P/g and the adsorption process of the three crystal forms of zirconia powders conformed to the Langmuir adsorption model. In the first 2 min of rapid adsorption, amorphous zirconia completed 76.23% of the adsorption process and the monoclinic phase also completed more than 60%. The adsorption process of the three crystal forms of zirconia was completed within 240 min and conformed to the pseudo-second-order kinetic model. Their adsorption characteristics of the three crystal forms of zirconia decreased with the increase in pH. While the pH was above than the isoelectric point of the solution, the adsorption capacity was significantly reduced. The large specific surface area and high hydroxyl content of the zirconia nano-powder made a great contribution to the adsorption process.     

Reactive red 120 and NI(II) derived poly(2‐hydroxyethyl methacrylate) nanoparticles for urease adsorption

Non‐porous poly(2‐hydroxyethyl methacrylate) [p(HEMA)] nanoparticles were prepared by surfactant free emulsion polymerization. The p(HEMA) nanoparticles was about 200 nm diameter, spherical form, and non‐porous. Reactive Red 120 (RR 120) was covalently attached to the p(HEMA) nanoparticles and Ni(II) ions were incorporated to attach dye molecules. Urease was immobilized onto RR120‐Ni(II) attached p(HEMA) nanoparticles via adsorption. The maximum urease adsorption capacity of RR120‐Ni(II) attached p(HEMA) nanoparticles was 480.01 mg g^?1 nanoparticles at pH 7.0 in phosphate buffer. It was observed that urease could be repeatedly adsorbed and desorbed without significant loss in adsorption amount. K_m values were 21.50 and 34.06 mM for the free and adsorbed enzyme. The V_max values were 4 U for the free enzyme and 3.3 U for the adsorbed enzyme. The optimum pH was 25 mM pH 7 phosphate buffer for free and adsorbed enzyme. The optimum temperature was determined at 35°C and 55°C for the free and adsorbed enzyme, respectively. These findings show considerable promise for this material as an adsorption matrix in biotechnological applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39757.     

Removal of Pb2+ from the aqueous solution by tartrate intercalated layered double hydroxides

Adsorption of Pb²⁺ ion by a tartrate intercalated MgAl layered double hydroxides (MgAl-TA LDHs) was studied. The adsorption isotherms and kinetics were investigated as a function of various experimental parameters using batch adsorption experiments. The results indicated that the adsorption isotherm was well described by Sips model. The kinetic adsorption data were fitted well to the pseudo-second-order kinetic equation. The adsorption of Pb²⁺ was controlled mainly by the chemical process combined with intraparticle diffusion. Parameters of adsorption thermodynamic suggested that the interaction of Pb²⁺ adsorbed by MgAl-TA LDHs adsorbents was thermodynamically spontaneous and endothermic.     

Heavy Metal Adsorption by Magnetic Hybrid-Sorbent: An Experimental and Theoretical Approach

This study examined the sorption and desorption behaviors of Cu²⁺ and Pb²⁺ ions, which were adsorbed on the vinyl benzene chloride divinylbenzene (VBC-DVB-OH) polymer and magnetic hybrid adsorbent (VBC-DVB-OH-Fe) at pH 5. Batch and fixed bed column experiments were performed to study practical applicability and the breakthrough curves were obtained. The experimental equilibrium data, suitably fitted by the Langmuir and Freundlich isotherms, have shown that ferric oxide loaded magnetic hybrid sorbent (VBC-DVB-OH-Fe) exhibits higher adsorption capacity than vinyl benzene chloride divinylbenzene (VBC-DVB-OH) polymer. The results indicate the following order to fit the isotherms for both metal ions: Langmuir > Freundlich for polymeric sorbent and Freundlich > Langmuir for VBC-DVB-OH-Fe. The maximum adsorption capacity of VBC-DVB-OH adsorbent is 26.39 mg/g for Pb²⁺ and 7.93 mg/g for Cu²⁺ whereas it is increased to 45.81 mg/g for Pb²⁺and 25.64 mg/g for Cu²⁺ by using VBC-DVB-OH-Fe adsorbent. A series of column experiments were carried out to determine the breakthrough curves. The regeneration efficiency of the column runs was determined using HCl (10% v/v). The elution efficiency was 90% for each adsorbent.