Heavy Metal Removal from Water by Adsorption Using Pillared Montmorillonite

Removal of Cu^2＋, Cr^3＋ and Cd^2＋ from aqueous solutions by adsorption on montmorillonite modified by sodium dodecylsulfate （SDS） and hydroxy-alumino-silicate （HAS） was investigated. Experiments were carried out as a function of solution pH, solute concentration, and time. The Langmuir model was adopted to describe the single-solute adsorption isotherm, in which the Langmuir parameters were directly taken from those obtained in single-solute systems. The kinetics of metal ions adsorption was examined and the pseudo-first-order rate constant was finally evaluated.     

Adsorption of Ammonium and Heavy Metal Ions on Industrial Vermiculite from the Yuli Mine in Xinjiang, China

The present work discusses the mineralogy, saturated adsorption of ammonium and adsorption of heavy metal ions （Cu^2＋, Pb^2＋ and Zn^2＋） on industrial vermiculite samples from the Yuli Mine in Xinjiang Autonomous Region. The saturated adsorption capacity of ammonium and the affection factors of adsorption of Cu^2＋, Pb^2＋ and Zn^2＋ are discussed on the basis of the mineralogical characteristics of the industrial vermiculite samples. The saturated adsorption capacities of ammonium are between 56.02 and 98.42 mmol/100g. The time of adsorption equilibrium is about 30-60 min, and the pH values and concentration of the ion solution significantly affect the adsorption capacities of the heavy metal ions. The adsorption capabilities of the heavy metal ions on industrial vermiculite are almost the same in the low ion concentration solutions, characterized by a sequence of Zn^2＋〉Pb^2＋〉Cu^2＋ for adsorption capacity in solutions with relatively high ion concentration. The results have practical significance for the application of the industrial vermiculite to treating wastewater containing ammonium or heavy metal ions.     

Removal of Lead,Copper, Zinc and Cadmium from Water Using Phosphate Rock

Removal of Pb^2＋, Cu^2＋, Zn^2＋ and Cd^2＋ from aqueous solutions by sorption on a natural phosphate rock （FAP） was investigated. The effects of the contact time and initial metal concentration were examined in the batch method. The percentage sorption of heavy metals from solution ranges generally between 50% and 99%. The amount of sorbed metal ions follows the order Cu〉Pb〉Cd〉Zn. Heavy metal immobilization was attributed to both surface complexation of metal ions on the surface of FAP grains and partial dissolution and precipitation of a heavy metal-containing phosphate. The very low desorption ratio of heavy metals further supports the effectiveness of FAP as an alternative and low-cost material to remove toxic Pb^2＋, Cu^2＋, Zn^2＋ and Cd^2＋ from polluted waters.     

Pottery glaze—An excellent adsorbent for the removal of Cu(II) from aqueous solution

In the present study,pottery glaze was investigated as an excellent adsorbent for the removal of Cu(Ⅱ) ions from aqueous solution.Effect of concentration,contact time,pH,and effect of electrolyte concentration,adsorbent doses and temperature were studied by using batch process to optimize conditions for maximum adsorption. Equilibrium isotherm data were analyzed using Langmuir,Freundlich and Temkin isotherms at 30,40 and 50℃. Thermodynamic parameters such as standard enthalpy change(ΔH0),free energy change(ΔG 0)and entropy change (ΔS0)were also evaluated.These parameters indicated that adsorption process is endothermic and spontaneous in nature.The mean energy calculated from Dubinin-Radushkeuich(D-R)isotherms showed chemical nature of adsorption.The kinetic data were evaluated using the pseudo-first-order and pseudo-second order kinetic equations and it was found that data best fitted pseudo-second-order model over a wide range of initial Cu(Ⅱ)concentrations supporting that chemisorption process was involved.The adsorption and desorption studies carried out by batch process suggested 100% desorption of Cu(Ⅱ)ions with 0.1 N HCl solution.     

Petrology and phase equilibrium modeling of sapphirine ＋ quartz assemblage from the Napier Complex,East Antarctica： Diagnostic evidence for Neoarchean ultrahigh-temperature metamorphism

A synthesis of the petrological characters of granulite facies rocks that contain equilibrium sapphirine ＋ quartz assemblage from two localities （Tonagh Island （TI） and Priestley Peak （PP）） in the Napier Complex,East Antarctica,provides unequivocal evidence for extreme crustal metamorphism possibly associated with the collisional orogeny during Neoarchean.The reaction microstructures associated with sapphirine ＋ quartz vary among the samples,probably suggesting different tectonic conditions during the metamorphic evolution.Sapphirine and quartz in TI sample were probably in equilibrium at the peak stage,but now separated by corona of Grt ＋ Sil ＋ Opx suggesting near isobaric cooling after the peak metamorphism,whereas the Spr ＋ Qtz ＋ Sil ＋ Crd ＋ Spl assemblage replaces garnet in PP sample suggesting post-peak decompression.The application of mineral equilibrium modeling in NCKFMASHTO system demonstrated that Spr ＋ Qtz stability is lowered down to 930 ℃ due to small Fe3＋ contents in the rocks （mole Fe2O3/（FeO ＋ Fe2O3） =0.02）.The TI sample yields a peak p-T range of 950-1100 ℃ and 7.5-11 kbar,followed by cooling toward a retrograde stage of 800-950 ℃ and 8-10 kbar,possibly along a counterclockwise p-T path.In contrast,the peak condition of the PP sample shows 1000-1050 ℃ and ＞12 kbar,which was followed by the formation ofSpr ＋ Qtz corona around garnet at 930-970 ℃ and 6.7-7.7 kbar,suggesting decompression possibly along a clockwise p-T trajectory.Such contrasting p-T paths are consistent with a recent model on the structural framework of the Napier Complex that correlates the two areas to different crustal blocks.The different p-T paths obtained from the two localities might reflect the difference in the tectonic framework of these rocks within a complex Neoarchean subduction/collision belt.     

Adsorption behavior of CO2 in magnesite micro-pores at high temperature and pressure

The fluid inclusions in mantle rocks and melt indicated that a large amount of CO₂fluid exists in the deep earth,which is of great significance for understanding the deep carbon cycle and the composition of mantle.However,it was also suggested that carbonate minerals were likely to be the main host of mantle carbon.At the same time,the distribution and behavior of carbon in the mantle still remain a puzzle.In this paper,the adsorption behavior and occurrence characteristics of supercritical CO₂in magnesite(MgCO3)pores were studied by the Grand Canonical Monte Carlo method(GCMC)under the different conditions of CO₂pressures(0–100 MPa),temperatures(350–1500 K)and the pore sizes(7.5–30?).The simulated results showed that the adsorption of CO₂in magnesite was a physical adsorption,which was mainly controlled by the intermolecular force.The gas adsorption became more stable when the adsorption site shifted from the high energy site to the low energy site with increasing pressure(P)and decreasing temperature(T)and pore size.At the same time,the variations of excess adsorption amounts of CO₂in the pores of magnesite(Nexcess)under the different conditions were quantitatively calculated.It was found that the Nexcess decreased with increasing T,but increased with increasing P and pore size.The results favor understanding the CO₂migration,seismic precursor observations,and heat transfer process in the deep earth.     

Surface and adsorptive properties of wood char particles in soil

Char and soot （black carbon, BC） are highly surface-active materials that can play an important role in contaminant fate and bioavailability in soils and sediments. This report summarizes our research on the influence of adsorbate structure and BC properties on adsorption of organic compounds, and the possible attenuation of BC surface activity by humic substances in the environment. The BC was a maple wood char formed at 400 ℃ in air and under other conditions. The solutes were polar and apolar aromatic compounds. The following points will be discussed. （1） By comparing adsorption to nonporous graphite, it was shown that molecular sieving effects （steric restriction） in the char micropore system occur in the order of increasing substitution on the benzene ring and in the order of increasing fused ring size. （2） By accounting for hydrophobic and steric effects it was shown that aromatic rings substituted with strongly pi-electron-accepting functional groups, such as nitro, undergo pi-pi electron donor-acceptor （EDA） interactions with the pi-donor polyaromatic （graphene） surface of the char. The free energy of adsorption due to pi-pi EDA interactions correlated with the free energy of molecular complexation in chloroform with model compounds representing the graphene surface （napthalene, phenanthrene, pyrene）. （3） A series of chars were prepared of different polarity （O content） but similar surface area and pore size distribution by varying temperature and atmosphere. Single- and bi-solute experiments showed that polar interactions with surface O are not a significant driving force for adsorption of polar compounds. Rather, surface O attracts water molecule clusters that inhibit adsorption of both polar and nonpolar compounds by competition. （4） Aging of char particles in a soil-water suspension strongly reduced char SA and sorption of added benzene. Studies were conducted with dissolved humic （HA） acid, HA-char co-precipitates, Ala＋-HA-char co-flocculates, and soybean oil representing humic lipid components.     

Diffusion Kinetics of Carbonate Hydroxyapatite （CHAP） for Adsorbing F^- Dissolved in Water

A systematic research was performed about diffusion kinetics of adsorbing F^- dissolved in water for carbonate hydroxyapatite （CHAP） from the natural hydroxyapatite which was modified by adulterating with CO3^2-. The result shows that the speed of F^- adsorption is controlled by membrane diffusion when F^- concentration is relatively low, which is expressed by the kinetic equation of diffusion Q=0.0005（Ci-C）（t-ti）＋0.3967, or by vacancy diffusion when F^- concentration is relatively high, which is expressed by the kinetic equation of diffusion In[C（o, t）]=8.4718-0.5048Int. Based on the feature of CHAP for adsorbing F^- dissolved in water and its special channel of the structure of CO3^3- modified hydroxyapatite, models of vacancy diffusion and membrane diffusion were established.     

Effect of Uncertainty of the Pre-Exponential Factor on Kinetic Parameters of Hydrocarbon Generation from Organic Matter and its Geological Applications

The source rock sample of the Shahejie Formation（upper Es₄） in Jiyang Sag was pyrolyzed under open system with the Rock-Eval-Ⅱapparatus,and then kinetic model parameters were calibrated for investigating the effect of uncertainty of pre-exponential factors on kinetic parameters and geological applications,where the parallel first-order reaction rate model with an average pre-exponential factor and discrete distribution activity energies was used.The results indicate that when the pre-exponential factor changes from low to high,an extreme value for residual errors occurs.And with the increasing pre-exponential factor,the distribution shape of activation energies are nearly the same,but the values of activation energies move higher integrally,and the average activation energy increases about 12 kJ/mol for every 10-fold of the pre-exponential factors.Extrapolating the geological heating rate of 3.3℃/Ma,the results show that with the increases in pre-exponential factor, the geological temperature corresponding to TR_0.5（transforming ratio of hydrocarbon generation is 50%） increases gradually,and the additional temperature gradually decreases.Combined with geochemical data of source rock,the kinetic parameters with different pre-exponential factors are used to calculate the transformation ratio of hydrocarbon generation,and the result indicates that kinetic parameters corresponding to the better optimized pre-exponential factor are more suitable.It is suggested that the risk assessment of hydrocarbon generation kinetic parameters should be enhanced when using the kinetic method to appraise the oil-gas resources.Meantime,the application result of different kinetic parameters should be verified with geological and geochemical data of source rock in the target area;therefore,the most suitable kinetic parameters for target can be obtained.     

Origin of the Zedang and Luobusa Ophiolites,Tibet

The Zedang and Luobusa ophiolites are located in the eastern section of the Yalung Zangbo ophiolite belt,and they share similar geological tectonic setting and age.Thus,an understanding of their origins is very important for discussion of the evolution of the Eastern Tethys Ocean.There is no complete ophiolite assemblage in the Zedang ophiolite.The Zedang ophiolite is mainly composed of mantle peridotite and a suite of volcanic rocks as well as siliceous rocks,with some blocks of olivinepyroxenite.The mantle peridotite mainly consists of Cpx-harzburgite,harzburgite,some lherzolite,and some dunite.A suite of volcanic rocks is mainly composed of caic-aikaline pyroclastic rocks and secondly of tholeiitic pillow lavas,basaltic andesites,and some boninitic rocks with a lower TiO2 content （TiO2 ＜ 0.6％）.The pyroclastic rocks have a LREE-enriched REE pattern and a LILE-enriched （compared to HFSE） spider diagram,demonstrating an island-arc origin.The tholeiitic volcanic rock has a LREE-depleted REE pattern and a LILE-depleted （compared to HFSE） spider diagram,indicative of an origin from MORB.The boninitic rock was generated from fore-arc extension.The Luobusa ophiolite consists of mantle peridotite and mafic-ultramaflc cumulate units,without dike swarms and volcanic rocks.The mantle peridotite mainly consists of dunite,harzburgite with low-Opx （Opx ＜ 25％）,and harzburgite （Opx ＞ 25％）,which can be divided into two facies belts.The upper is a dunite-harzburgite （Opx ＜ 25％） belt,containing many dunite lenses and a large-scale chromite deposit with high Cr203; the lower is a harzburgite （Opx ＞25％） belt with small amounts of dunite and lherzolite.The Luobusa mantle peridotite exhibits a distinctive vertical zonation of partial melting with high melting in the upper unit and low melting in the lower.Many mantle peridotites are highly depleted,with a characteristic U-shaped REE pattern peculiar to fore-arc peridotite.The Luobusa cumulates are composed of wehrlite and olivine-pyroxenite,of the P-P-G ophiolite series.This study indicates that the Luobusa ophiolite was formed in a fore-arc basin environment on the basis of the occurrence of highly depleted mantle peridotite,a high-Cr2O3 chromite deposit,and cumulates of the P-P-G ophiolite series.We conclude that the evolution of the Eastern Tethys Ocean involved three stages：the initial ocean stage （formation of MORB volcanic rock and dikes）,the forearc extension stage （formation of high-Cr203 chromite deposits and P-P-G cumulates）,and the islandarc stage （formation of caic-alkaline pyroclastic rocks）.     

Separation of Cu<Superscript>2+</Superscript> and Pb<Superscript>2+</Superscript> by tetraethylenepentamine-modified sugarcane bagasse fixed-bed column: selective adsorption and kinetics

Tetraethylenepentamine-modified sugarcane bagasse (SCB) was prepared to improve its adsorption capacity and selectivity toward Cu²⁺. Adsorption performances of the modified sorbent for Cu²⁺ were studied in batch system. Separation of Cu²⁺ from Pb²⁺ by the modified sorbent fixed-bed column were studied under dynamic system with initial molar concentration ratio \(\left( {C_{0}^{\text{Cu}} /C_{0}^{\text{Pb}} } \right)\) ranging from 1:1 to 1:100. The amount of Cu²⁺ and Pb²⁺ adsorbed on the saturated column was calculated by the elution curve. Batch experimental results showed that the adsorption capacity of the sorbent for Cu²⁺ increased from 0.12 to 0.21 mmol g^?1 after modification. Dynamic adsorption results showed that the modified SCB had higher adsorption affinity toward Cu²⁺ than Pb²⁺. 0.07 mmol g^?1 of adsorbed Pb²⁺ was pushed off by Cu²⁺ during the competitive adsorption process at \(C_{0}^{\text{Cu}} /C_{0}^{\text{Pb}} = {\text{1:1}}.\) The breakthrough curves and adsorption kinetics of Cu²⁺ in the column could be fitted well by the Yoon–Nelson and modified Yoon–Nelson model, respectively. According to the elution curve, the amount of Cu²⁺ adsorbed on the fixed-bed column were 0.16, 0.16 and 0.15 mmol g^?1, while that of Pb²⁺ were 0.0016, 0.0051 and 0.0094 mmol g^?1 when \(C_{0}^{\text{Cu}} /C_{0}^{\text{Pb}}\) increased from 1:1 to 1:10 and 1:100. Cu²⁺ could be selectively adsorbed and separated from Pb²⁺ by using the modified sorbent fixed-bed column.     

<Superscript>10</Superscript>Be, <Superscript>18</Superscript>O and radiogenic isotopic constraints on the origin of adakitic signatures: a case study from Solander and Little Solander Islands,New Zealand

Subduction-related Quaternary volcanic rocks from Solander and Little Solander Islands, south of mainland New Zealand, are porphyritic trachyandesites and andesites (58.20–62.19 wt% SiO₂) with phenocrysts of amphibole, plagioclase and biotite. The Solander and Little Solander rocks are incompatible element enriched (e.g. Sr ~931–2,270 ppm, Ba ~619–798 ppm, Th ~8.7–21.4 ppm and La ~24.3–97.2 ppm) with MORB-like Sr and Nd isotopic signatures. Isotopically similar quench-textured enclaves reflect mixing with intermediate (basaltic-andesite) magmas. The Solander rocks have geochemical affinities with adakites (e.g. high Sr/Y and low Y), whose origin is often attributed to partial melting of subducted oceanic crust. Solander sits on isotopically distinct continental crust, thus excluding partial melting of the lower crust in the genesis of the magmas. Furthermore, the incompatible element enrichments of the Solander rocks are inconsistent with partial melting of newly underplated mafic lower crust; reproduction of their major element compositions would require unrealistically high degrees of partial melting. A similar argument precludes partial melting of the subducting oceanic crust and the inability to match the observed trace element patterns in the presence of residual garnet or plagioclase. Alternatively, an enriched end member of depleted MORB mantle source is inferred from Sr, Nd and Pb isotopic compositions, trace element enrichments and εHf ? 0 CHUR in detrital zircons, sourced from the volcanics. ¹⁰Be and Sr, Nd and Pb isotopic systematics are inconsistent with significant sediment involvement in the source region. The trace element enrichments and MORB-like Sr and Nd isotopic characteristics of the Solander rocks require a strong fractionation mechanism to impart the high incompatible element concentrations and subduction-related (e.g. high LILE/HFSE) geochemical signatures of the Solander magmas. Trace element modelling shows that this can be achieved by very low degrees of melting of a peridotitic source enriched by the addition of a slab-derived melt. Subsequent open-system fractionation, involving a key role for mafic magma recharge, resulted in the evolved andesitic adakites.     

Removal of lead(II) from aqueous stream by hydrophilic modified kapok fiber using the Fenton reaction

A hydrophilic kapok fiber was prepared by a chemical process of the Fenton reaction and used as an adsorbent to remove Pb(II) from aqueous solution. The effects of experimental parameters including pH, contact time, Pb(II) concentration, and coexisting heavy metals were estimated as well as evaluated. The optimum concentrations of FeSO₄ and H₂O₂ for the Fenton reaction-modified kapok fiber (FRKF) were 0.5 mol L^?1 and 1 mol L^?1, respectively. The adsorption kinetic models and isotherm equations of Langmuir and Freundlich were conducted to identify the most optimum adsorption rate and adsorption capacity of Pb(II) on FRKF. The FRKF displayed an excellent adsorption rate for Pb(II) in single metal solution with the maximum adsorption capacity of 94.41?±?7.56 mg g^?1 at pH 6.0. Moreover, the FRKE still maintained its adsorption advantage of Pb(II) in the mixed metal solution. The FRKF exhibited a considerable potential in removal of metal content in wastewater streams.     

Assessment of raw clays from Maghnia (Algeria) for their use in the removal of Pb<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> ions from industrial liquid wastes: a case study of wastewater treatment

Homogenized samples of raw clays resulting from two (2) different lots of natural clays from Maghnia (Algeria) have been assessed for their potential use in the removal of Pb²⁺ and Zn²⁺ ions from industrial liquid wastes (LW). Raw and acid-activated samples have been characterized by powder X-ray diffraction, FT-IR spectroscopy, electron microscopy (SEM), and X-ray fluorescence (XRF) and used as adsorbents for the removal of Pb²⁺ and Zn²⁺ ions from aqueous system using adsorption method under different conditions. The effect of factors including contact time, pH, and dosage on the adsorption properties of Pb²⁺ and Zn²⁺ ions onto clays was investigated at 25 °C. The obtained results revealed that the removal percentages of Pb²⁺ and Zn²⁺ ions, from both aqueous solution (AS) and LW, were varying between 90 and 98% for 40 min and optimal pH values ranged from 5 to 6 for Pb²⁺ and Zn²⁺ ions, respectively. The kinetics of both Pb²⁺ and Zn²⁺ ion adsorption fitted well with the pseudo-second-order model. Langmuir, Freundlich, and Temkin adsorption isotherms were used, and their constants were evaluated. The values of thermodynamic parameters, ΔH°, ΔS°, and ΔG° indicated that the adsorption of Pb²⁺ and Zn²⁺ ions was spontaneous and exothermic process in nature. The adsorption and desorption isotherms indicated that Pb²⁺ and Zn²⁺ adsorption to raw clays was reversible. The experimental results obtained showed that the raw clays from Maghnia (Algeria) had a great potential for removing Pb²⁺ and Zn²⁺ ions from industrial liquid wastes using adsorption method.     

Differential behavior of components of the <Superscript>238</Superscript>U-<Superscript>206</Superscript>Pb and <Superscript>235</Superscript>U-<Superscript>207</Superscript>Pb isotopic systems in polymineralic U ores

U-Pb systems were examined in samples (ranging from 4 to 10 cm³ in volume) of ore material taken from along a 3.5-m profile across a zone of U mineralization exposed in an underground mine at the Strel’tsovskoe U deposit in eastern Transbaikalia. The behaviors of two isotopic U-Pb systems (²³⁸U-²⁰⁶Pb and ²³⁵U-²⁰⁷Pb) are principally different in all samples from our profile. While the individual samples are characterized by a vast scatter of their T(²⁰⁶Pb/²³⁸U) age values (from 112 to 717 Ma), the corresponding T(²⁰⁷Pb/²³⁵U) values vary much less significantly (from 127 to 142 Ma) and are generally close to the true age of the U mineralization. The main reason for the distortion of the U-Pb system is the long-lasting (for tens of million years) migration of intermediate decay products in the ²³⁸U-²⁰⁶Pb(RD²³⁸U) in the samples. This process resulted in the loss of RD²³⁸U from domains with high U concentrations and the subsequent accommodation of RD²³⁸U at sites with low U concentrations. The long-term effect of these opposite processes resulted in a deficit or excess of ²⁰⁶Pb as the final product of ²³⁸U decay. The loss or migration of RD²³⁸U are explained by the occurrence of pitchblende in association with U oxides that have higher Si and OH concentrations than those in the pitchblende and a higher ⁺⁶U/⁺⁴U ratio. The finely dispersed character of the mineralization and the loose or metamict texture of the material are the principal prerequisites for RD²³⁸U loss and an excess of ²⁰⁶Pb in adjacent domains with low U concentrations. Domains with low U contents in the zone with U mineralization serve as geochemical barriers (because of sulfides contained in them) at which long-lived RD²³⁸U(²²⁶Ra, ²¹⁰Po, ²¹⁰Bi, and ²¹⁰Pb) were accommodated and subsequently caused an excess of ²⁰⁶Pb. The ²³⁵U-²⁰⁷Pb system remained closed because of the much briefer lifetime of the ²³⁵U decay products. This may account for the significant discrepancies between the T(²⁰⁶Pb/²³⁸U) and T(²⁰⁷Pb/²³⁵U) age values. RD²³⁸U was most probably lost via the migration of radioisotopes at the middle part and end of the ²³⁸U family (starting with ²²⁶Ra). The heavy Th, Pa, and U radioisotopes (²³⁴Th, ²³⁴Pa, ²³⁴U, and ²³⁰Th) that occur closer to the beginning of ²³⁸U decay, before ²²⁶Ra, only relatively insignificantly participated in the process. Our results show that the loss and migration of RD²³⁸U are, under certain conditions, the main (or even the only) process responsible for the distortion of the U-Pb system.     

Effect of multifactors interaction on competitive adsorption of Zn<Superscript>2+</Superscript> and Cd<Superscript>2+</Superscript> by response surface methodology

The problem associated with multi-metals contaminated soils has generated increasingly more attention. Thus, it is necessary within the field to study the mutual influence of environmental factors on competitive adsorption. The majority of studies carried out to date have concentrated on the variation of adsorption capacity or the removal efficiency, with only a single factor changed (including pH, ionic strength, and metal concentration). However, the interaction effect among various environmental factors was ignored in these studies. The purpose of this study was mainly aimed toward the investigation of the interaction of two influential factors, as well as the influential degree of each factor (such as the initial pH, ionic strength, initial metal concentration, and the competitive metal concentration) on competitive adsorption using the response surface method. These results demonstrated that the influential degree of each factor studied on the competitive adsorption of Zn²⁺ and Cd²⁺ followed the trend of having the initial concentration of the target metal?>?initial pH?>?concentration of competitive metal?>?ionic strength. When the metal concentration was held constant, we found that the competitive adsorption of Zn²⁺ initially increased, followed by a decrease with increasing initial pH. However, this was found to change minimally with increasing ionic strength. When the initial pH or ionic strength was held constant, the competitive ability was observed to increase with increasing Zn²⁺ concentration. However, with increasing Zn²⁺ or Cd²⁺ concentrations, the variation degree of the competitive adsorption was found to become smaller. These results provide novel information toward a better understanding of the effect of multifactors on the competitive adsorption of Zn²⁺ and Cd²⁺.     

Adsorptive removal of Cu(II) and Pb(II) onto mixed-waste activated carbon: kinetic,thermodynamic, and competitive studies and application to real wastewater samples

This work aimed to investigate the adsorption characteristics, both kinetically and thermodynamically, of Cu(II) and Pb(II) removal from aqueous solutions onto mixed-waste activated carbon, as well as to study the competitive behavior found in mixed heavy metal solution systems. This study shows that activated carbon prepared from mixed waste is an effective adsorbent for the removal of Cu(II) and Pb(II) from aqueous solutions, with the aim of detoxifying industrial effluents before their safe disposal onto water surfaces. The adsorption process was characterized in terms of kinetic and thermodynamic studies. In addition, the influence of presence of Cu(II) and Pb(II) in a competitive system was investigated. The results showed that the maximum adsorption capacities were gained at a pH of 6 with a contact time of 180 min, a metal solution concentration of 300 ppm, and an adsorbent dose of 0.3 g/L. The adsorption process was found to follow a pseudo-first-order kinetic model. Thermodynamic parameters such as ΔG ^o, ΔH ^o, and ΔS ^o showed that the sorption process was spontaneous and endothermic in nature. A competitive study demonstrated the applicability of mixed-waste activated carbon to adsorb Cu(II) and Pb(II) from a solution of mixed metals. In addition, the adsorption capacity was found to be as effective as other adsorbents reported in the literature. The developed adsorptive removal procedure was applied for treatment of real wastewater samples and showed high removal efficiency.     

Adsorption of Ag<Superscript>+</Superscript> ions on hydrolyzed lignocellulosic materials based on willow,paulownia, wheat straw and maize stalks

In the present work, the adsorption of Ag⁺ ions on hydrolyzed plant biomass (willow, paulownia, wheat straw and maize stalks) was investigated. Chemical analyses were performed to establish the composition of the obtained materials. Adsorption mechanism, adsorption sites and specific surface areas of these materials were examined by BET analysis, IR spectroscopy, XPS and EPR. The effects of contact time, acidity of initial solutions and Ag⁺ ion concentrations were followed. Pseudo-first-order, pseudo-second-order and intra-particle diffusion models were used to analyze kinetic data. In all cases, the adsorption was significantly affected by the pH value. Different types of adsorption isotherms of Ag⁺ ions (either Langmuir or Freundlich) were registered depending on the adsorbing material. The adsorption mechanism is complex, and the process passes through different stages as clustering of Ag⁺ ions and formation of elemental Ag. The maximal adsorption capacities varied from 2.05 to 6.07 mg g^?1. The obtained results revealed that the examined waste lignocellulosic materials are promising adsorbents for Ag⁺ ions.     

Kinetics and thermodynamics study of lead adsorption on to activated carbons from coconut and seed hull of the palm tree

The kinetic and thermodynamic of the bath sorption of lead (Pb) on to activated carbon from Coconut (CA) and Seed hull of the Palm tree (GA) have been investigated. The effects of initial Pb concentration, contact time and temperature were examined. The results showed that the adsorption capacities of the activated carbons increased with the initial lead concentration. The process sorption followed a pseudo first order kinetics and parameters such as Ea and k₀ were determined. It could be best fitted by the Langmuir and Freundlich isotherms. From the first, the equilibrium sorption capacities of lead ion were determined and found to be respectively 4.38 and 3.77 mg/ g for CA and GA at 60 °C. The thermodynamic parameters such as dGH, dGS and dGG were computed from the experimental data. These values show that the adsorption is endothermic and non spontaneous. Moreover, the relative weak values of dGH (～5 kcal/mol) confirm a physical adsorption. The maximum adsorptions were obtained at 60 °C, pH 4 and with a Pb initial concentration of 100 mg/L.     

<Superscript>1</Superscript>H NMR-based serum metabolic profiling of <Emphasis Type="Italic">Carassius auratus gibelio</Emphasis> under the toxicity of Pb<Superscript>2+</Superscript> and Cd<Superscript>2+</Superscript>

Lead and cadmium are the two widely recognized toxic metals, with known ecological risk to freshwater fish in contaminated ecosystems. However, their effect at environmentally realistic level in a mixture has been rarely investigated. In the present study, serum metabolic responses of Crucian carp exposed to Pb (30 µgL^?1), Cd (100 µgL^?1) and Pb+Cd (30 + 100 µgL^?1) for 21 days were investigated by ¹H NMR-based metabolomics. The metabolic responses were compared to control by multivariate techniques (PCA, PLS-DA and OPLS-DA), and metabolites that significantly contributed to the variation were identified. Metal dependent metabolic responses revealed a decline of alanine, lysine and tyrosine in Pb exposed fish, indicating changes in neurotransmitters, and amino acid metabolism, while fish exposed to Cd showed significant decrease in lysine, isoleucine, leucine, alanine and increase in 3-hydroxybutyrate, acetone, lactate, choline, inosine, guanosine and threonine. The coexposure of Pb and Cd had additive effect on metabolic profile with increase in pyruvate, guanosine and inosine. The overall metabolic changes due to Pb and Cd were characterized by disturbed energy metabolism, impaired osmotic regulation and a shift from aerobic to anaerobic respiration. Moreover, ¹H NMR-based metabolomics was proved to be a powerful tool in elucidating the toxic effects of environmental pollutants and underlying mechanism.