Sorption studies of Zn(II)- and Cd(II)ions from aqueous solution on treated sawdust of sissoo wood

Sawdust, an inexpensive material, has been utilized as an adsorbent for the removal of Zn(II)- and Cd(II)ions from aqueous solution. The effects of time of equilibrium, pH, temperatures and dosage of the adsorbent on the removal of Zn(II)- and Cd(II)ions have been studied. The equilibrium nature of Zn(II)- and Cd(II)ions adsorption at different temperatures (25–60 °C) has been studied. The percent adsorption of Zn(II)- and Cd(II)ions increased with an increase in pH, temperature and dosage of treated sawdust. The applicability of the Langmuir isotherm suggests the formation of monolayer coverage of Zn(II)- and Cd(II)ions at the surface of the adsorbent. The thermodynamic parameters like free energy, enthalpy and entropy changes for the adsorption of Zn(II)- and Cd(II)ions has also been computed and discussed. The heat of adsorption [ΔH=17.706 kJmole^-1 for Zn(II) and ΔH=16.949 kJmole^-1 for Cd(II)] implied that the adsorption was an endothermic adsorption. The sawdust was found to be a metal adsorbent as effective as activated carbon.     

Sorption of aromatic organic contaminants by biopolymers: effects of pH, copper (II) complexation, and cellulose coating

Sorption of hydrophobic organic compounds (HOCs) (i.e., pyrene, phenanthrene, naphthalene, and 1-naphthol) by original and coated biopolymers was examined. Lignin yielded nonlinear isotherms due to its glassy character. Except for pyrene, cellulose showed linear isotherms for other compounds, indicating a partitioning dominant mechanism. Sorption of 1-naphthol by lignin decreased with increasing pH, attributed to both the increased pi e theta-pi e theta repulsion and weakened hydrogen bonds, while the affinity reduction of cellulose for 1-naphthol with increasing pH resulted from only the decrease in H-bonding due to its absence of benzene ring. Complexation of lignin with Cu2+ increased the sorption affinity for phenanthrene (2.6 times) and slightly enhanced its isotherm nonlinearity. For 1-naphthol, lignin-Cu2+ complex had a much higher sorption capacity (7 times)than the original lignin, accompanied bythe increased isotherm nonlinearity. Cellulose-coated lignin showed increased sorption affinity and more pronounced nonlinearity for 1-naphthol than the lignin-Cu2+ complex. In comparison, cellulose coating exhibited little effect on sorption affinity for phenanthrene relative to the lignin-Cu2+ complex. Isotherm nonlinearity of coated lignins increased with increasing cellulose coating, indicating more condensed domains produced, supported by an increase (from 68.9 degrees C for the original lignin to 82.4 degrees C for the highest cellulose coating level) in glass transition temperature (Tg). Results of this study highlightthe importance of structure, polarity, surface O-containing functional groups, and surface charges of biopolymers in controlling HOC sorption.     

Removal of Cd(II) ions by oxidized coconut coir

Biosorption potential of oxidized coconut coir (OCC) for removal of Cd(II) from aqueous medium at batch and column level was studied. Lignin and cellulose groups of coir were modified to acidic groups. Optimum biosorption was observed at pH 6. Isotherm data revealed that Langmuir gives best fit for experimental results with maximum adsorption capacity of 12.35 mg/g compared to unmodified coconut coir (5.29 mg/g). The column experiments were conducted as a function of flow rate, bed height, and influent Cd(II) concentration. Biosorption has best performance at 10 mg/L inlet concentration, 5 ml/min flow rate and 7 cm bed height.     

Sorption versus biomineralization of Pb(II) within Burkholderia cepacia biofilms

X-ray spectroscopy measurements have been combined with macroscopic uptake data and transmission electron microscopy (TEM) results to show that Pb(II) uptake by Burkholderia cepacia is due to simultaneous sorption and biomineralization processes. X-ray microprobe mapping of B. cepacia biofilms formed on alpha-Al2O3 surfaces shows that Pb(II) is distributed heterogeneously throughout the biofilms because of the formation of Pb "hot spots". EXAFS data and TEM observations show that the enhanced Pb accumulation is due to the formation of nanoscale crystals of pyromorphite (Pb5(PO4)3(OH)) adjacent to the outer-membrane of a fraction of the total population of B. cepacia cells. In contrast, B. cepacia cell suspensions or biofilms that were heat-killed or pretreated with X-rays do not form pyromorphite, which suggests that metabolic activity is required. Precipitation of pyromorphite occurs over several orders of magnitude in [H-] and [Pb] and accounts for approximately 90% of the total Pb uptake below pH 4.5 but only 45-60% at near-neutral pH because of the formation of additional Pb(II) adsorption complexes. Structural fits of Pb L(III) EXAFS data collected for heat-treated cells at near-neutral pH suggest that Pb(II) forms inner-sphere adsorption complexes with carboxyl functional groups in the biofilms.     

Modification of sawdust from pine and beech wood with the succinic anhydride

The aim of this study was to compare the reactivity of the succinic anhydride with the comminuted softwood (Pinus sylvestris L.) and hardwood (Fagus sylvatica L.). By extending the time of reaction (from 4 to 8 hours), products with different degrees of modification were obtained. It was demonstrated that in comparison with beech wood, the wood of Scots pine enters the reaction with the succinic anhydride easier. The results of the thermogravimetric analysis showed that the esterification of softwood and hardwood reduced the initial temperature of their thermal degradation. Wood modified with the succinic anhydride is characterised by poorer thermostability in comparison with natural wood.     

Sorption of copper,zinc and cobalt by oat and oat products

We determined copper, zinc and cobalt sorption by oat and its products under variable pH conditions as well as the content of neutral dietary fiber (NDF) and its fractional composition. Adsorbents in a model sorption system were: oat, dehulled oat, oats bran and oats flakes. Three various buffers (pH 1.8, 6.6 and 8.7) were used as dispersing solutions. Results collected during this study indicate that copper, zinc and cobalt sorption is significantly affected by the type of cereal raw material. Zinc and copper ions are subjected to higher sorption than cobalt ions. Examined metal ions were subjected to high sorption under conditions corresponding to the duodenum environment (pH 8.7( regardless of the kind of adsorbent. A little lower sorption capacity is observed under conditions close to the neutral environment, while the lowest one is found in environment reflecting conditions of stomach juice (pH 1.8). Zinc ions are bound intensively by dehulled oat, while oats flakes bound mostly copper and cobalt, independently on environmental conditions. Contents of dietary fiber in oat, dehulled oat, oat bran and oat flakes were: 40.1, 19.3, 20.3 and 14.3%, respectively. The dominating fraction in all oat products was the fraction of hemicelluloses. The content of remaining fractions varies in dependence on the product.     

Sorption of copper,zinc and cobalt by oat and oat products

We determined copper, zinc and cobalt sorption by oat and its products under variable pH conditions as well as the content of neutral dietary fiber (NDF) and its fractional composition. Adsorbents in a model sorption system were: oat, dehulled oat, oats bran and oats flakes. Three various buffers (pH 1.8, 6.6 and 8.7) were used as dispersing solutions. Results collected during this study indicate that copper, zinc and cobalt sorption is significantly affected by the type of cereal raw material. Zinc and copper ions are subjected to higher sorption than cobalt ions. Examined metal ions were subjected to high sorption under conditions corresponding to the duodenum environment (pH 8.7), regardless of the kind of adsorbent. A little lower sorption capacity is observed under conditions close to the neutral environment, while the lowest one is found in environment reflecting conditions of stomach juice (pH 1.8). Zinc ions are bound intensively by dehulled oat, while oats flakes bound mostly copper and cobalt, independently on environmental conditions. Contents of dietary fiber in oat, dehulled oat, oat bran and oat flakes were: 40.1, 19.3, 20.3 and 14.3%, respectively. The dominating fraction in all oat products was the fraction of hemicelluloses. The content of remaining fractions varies in dependence on the product.     

Sorption of mercuric ion by synthetic nanocrystalline mackinawite (FeS)

Iron sulfides are known to be efficient scavengers of heavy metals. In this study, Hg(II) sorption was investigated using synthetic nanocrystalline mackinawite (a disordered phase) as a function of initial Hg(II) concentration [Hg(II)]0, initial FeS concentration [FeS]0, total chloride concentration CIT, and pH. Hg(II) sorption mechanisms are dependent on relative concentrations of [Hg(II)]0 and [FeS]0 (the molar ratio of [Hg(II)0/[FeS]0). When the molar ratio of [Hg(II)]0/[FeS]o is as low as 0.05, adsorption is mainly responsible for Hg(II) removal, with its contribution to the overall sorption increasing at lower Cl(T). As the molar ratio increases, the adsorption capacity becomes saturated, resulting in precipitation of a sparingly soluble HgS(s). XRD analysis indicates formation of metacinnabar (beta-HgS). Concurrently with HgS(s) precipitation, the released Fe(II) from FeS(s) is resorbed by adsorption at acidic pH and either adsorption or precipitation as Fe (hydr)-oxides at neutral to basic pH. Subsequently, the Fe precipitate formed at neutral to basic pH serves as an adsorbent for Hg(II). Under the conditions where either adsorption or HgS(s) precipitation is dominant, more than 99% of [Hg(II)]0 is immobilized. When the molar ratio of [Hg(II)]0/[FeS]0 exceeds 1, the sulfide concentration is no longer sufficient for HgS(s) precipitation, and formation of chloride salts (Hg2Cl2 at acidic pH and HgCl2 x 3HgO at basic pH) occurs.     

Interaction between Cyanidin 3-glucoside and Cu(II) ions

The interaction between cyanidin 3-glucoside (Cy 3-glc) and Cu(II) in a binary solvent (methanol–water, 1:1, (v/v)) and in a phosphate buffer was studied. It is demonstrated that Cy 3-glc and Cu(II) ions form a complex that is manifested by appearance of a new absorption band. In the complex, the reduction of Cu(II)–Cu(I) and oxidation of Cy 3-glc takes place. The association constant of the complex formation was calculated using the Rose–Drago method. The complex stoichiometry in the binary solvent was 1:1, and the association constant was K = (28,600 ± 2600) M⁻¹. Interaction of Cy 3-glc and Cu(II) ions has two stages “fast” and “slow”. The kinetics of these processes has been investigated. Thermodynamic data for the “fast” process: enthalpy (ΔH^∗) and entropy (ΔE^∗) of activation, were calculated.     

Simple and efficient elimination of copper(II) in sugar-cane spirits

Cachaça is a distilled alcoholic beverage, produced in large quantities in Brazil, from fermentation of sugar cane juice. It is normally distillated in copper stills, which can sometimes cause contamination with this element, at toxic levels. An efficient method to remove copper ions to lower than 5 ppm in such alcoholic distillates, without perceptible changes in organoleptical properties, was herein developed. This method is based on a treatment with either CaCO₃ or MgCO₃, which behave as cationic exchangers.     

Simultaneous separation and preconcentration of Ni(II) and Cu(II) ions by coprecipitation without any carrier element in some food and water samples

A simple and highly sensitive separation and preconcentration procedure, which has minimal impact on the environment, has been developed. The procedure is based on the carrier element‐free coprecipitation of Ni(II) and Cu(II) ions by using 2‐{4‐[2‐(1H‐Indol‐3‐yl)ethyl]‐3‐(4‐chlorobenzyl)‐5‐oxo‐4,5‐dihydro‐1H‐1,2,4‐triazol‐1‐yl}‐N′‐(pyrrol‐2‐ylmethyliden)acetohydrazide (ICOTPA), as an organic coprecipitant. The levels of analyte ions were determined by flame atomic absorption spectrometry. The detection limits for Ni(II) and Cu(II) ions were found to be 0.27 and 0.58 μg L^?1, respectively, and the relative standard deviations for the analyte ions were lower than 4.0%. Spike tests and certified reference material analyses were performed to validate the method. The method was successfully applied for the determination of Ni(II) and Cu(II) ions levels in sea and stream water as liquid samples and red lentil and rice as solid samples.     

Decolorization of kraft bleaching effluent by advanced oxidation processes using copper (II) as electron acceptor

Two advanced oxidation processes (AOPs), TiO2/UV/O2 and TiO2/UV/Cu (II), were used to remove color from a Kraft bleaching effluent. The optimal decoloration rate was determined by multivariate analysis, obtaining a mathematical model to evaluate the effect among variables. TiO2 and Cu (II) concentrations and the reaction times were optimized. The experimental design resulted in a quadratic matrix of 30 experiments. Additionally, the pH influence on the color removal was determined by multivariate analysis. Results indicate that color removal was 94% at acidic pH (3.0) in the presence of Cu (11) as an electron acceptor. Under this condition, the biodegradation of the effluent increased from 0.3 to 0.6. Moreover, 70% of COD (chemical oxygen demand) was removed, and the ecotoxicity, measured by Daphnia magna, was reduced. Photocatalytic oxidation to remove the color contained in the Kraft mill bleaching effluent was effective under the following conditions: short reaction time, acidic pH values, and without the addition of oxygen due to the presence of Cu (II) in the effluent. Moreover, residual Cu (II) was a minimum (0.05.mg L(-1)) and was not toxic to the next biological stage. The experimental design methodology indicated that a quadratic polynomial model may be used to representthe efficiencyfor degradation of the Kraft bleach pulp effluent by a photocatalytic process.     

Adsorption and cosorption of tetracycline and copper(II) on montmorillonite as affected by solution pH

Land application of wastes generated from concentrated animal feeding operations may result in accumulation of tetracyclines (TCs) and metals in agricultural soils. Adsorption of TCs and metals on soil minerals strongly affects their mobility. This study was conducted to evaluate the interaction between tetracycline (TC) and Cu(ll) with regard to their adsorption and cosorption on montmorillonite as affected by solution pH. When solution pH was below 6.5, the presence of TC increased Cu(ll) adsorption on montmorillonite, which could be due to increasing Cu(II) adsorption via the TC bridge, or due to the stronger affinity of TC-Cu(II) complex to the mineral than Cu2+ ion itself. Zeta potential of the montmorillonite significantly decreased after the adsorption of TC, suggesting a strong interaction between TC and montmorillonite. Addition of Cu(ll) ions increased TC adsorption on the mineral in a wide range of pH. The experimental data were well fit with the weighted sum model. The complexes of TC and Cu(II) (CuH2L(2+), CuHL+, and CuL) had higher sorption coefficients (K(d)) than that of the corresponding TC species (H3L+, H2L, and HL-). Increasing adsorption of TC and Cu(II) on montmorillonite as they coexist in the normal pH environment may thus reduce their mobility.     

甜菜废粕吸附性能的研究

研究了甜菜废粕吸附溶液中Cu2＋的能力,采用间歇吸附试验来评价甜菜废粕对Cu2＋的除去效率,吸附速率相对较快,在60min即可达到平衡。在间歇试验条件下,最高可达90％的去除率。废粕吸附能力与溶液pH有关,pH5．5时最大吸附Cu2＋量可达30．9mg／g。废粕添加量为8g／L足以达到最佳处理效果。     

Sorption of anionic metsulfuron-methyl and cationic difenzoquat on peat and soil as affected by copper

The effect of cationic copper (Cu2+) on the sorption of anionic metsulfuron-methyl (Me) and cationic difenzoquat (DZ) to peat and soil was studied using a batch equilibration method. The results showed that Cu2+ increased the sorption of Me but diminished the sorption of DZ. The adsorption of Cu2+ on the surface of peat and soil neutralizes the negative charge, making the zeta potential (zeta) of peat and soil less negative, consequently decreasing the repulsion between the surface of peat or soil and Me and increasing the sorption of Me. Cu2+ may additionally form Cu-Me complexes in aqueous solution, which was preferentially sorbed to peat and soil over the anionic Me. In contrast, the decreased negative surface charge of soil and peat does not favor the sorption of cationic DZ. Fourier transform infrared showed that DZ may be sorbed through interaction with -OH or -COOH groups of peat and soil and that surface complexes of Cu2+ may form through these groups. A competitive sorption between Cu2t and DZ for the same sorption sites is indicated, leading to mutual sorption inhibition of both cations.     

Enhanced dechlorination of chlorinated methanes and ethenes by chloride green rust in the presence of copper(II)

The enhanced removal of carbon tetrachloride (CCl4), tetrachloroethene (C2Cl4), and trichloroethene (C2HCl3) by chloride green rust (GR(Cl)) in the presence of copper ions was investigated. X-ray powder diffraction (XRPD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the crystallization and chemical speciation, respectively, of the secondary mineral phases produced in the GR(Cl)-Cu(II) system. The addition of Cu(II) to GR(Cl) suspensions resulted in enhanced dechlorination of the chlorinated hydrocarbons examined in this study. The degradation reactions followed pseudo-first-order kinetics and the pseudo-first-order rate constant (k(obs)) for CCl4 (20 microM) removal by GR(CI) at pH 7.2 was 0.0808 h(-1). Addition of 0.5 mM Cu(II) completely dechlorinated CCl4 within 35 min, and the k(obs) was 84 times greater than that in the absence of Cu(II). Chloroform (CHCl3), the major chlorinated product in CCl4 dechlorination, accumulated at a concentration up to 13 microM in the GR(Cl) system alone, but was completely dechlorinated within 9 h in the GR(Cl)-Cu(II) suspension. Also, rapid removal of C2Cl4 and C2HCl3 by GR(Cl) was observed when Cu(II) was added. The k(obs) values for the removal of chlorinated ethenes were 4.7-7 times higher than that obtained in the absence of Cu(II). In addition, the k(obs) for PCE removal increased linearly with respect to Cu(II) concentrations in the range from 0.1 to 1.0 mM. Addition of Cu(II) at a concentration higher than 1.0 mM decreased the k(obs) for the removal of both C2Cl4 and C2HCl3 due to the decrease in structural Fe(II) concentration in GR(Cl) and the changes in redox potentials and pH values. Moreover, the highest removal efficiency and rate of C2Cl4 was obtained at near-neutral pH when Cu(II) was added into the GR(Cl) suspension. XPS and XRPD results showed that the Fe(II) in the GR(Cl) suspension could reduce Cu(II) to both Cu(I) and metallic Cu. These findings are relevant to the better understanding of the role of abiotic removal of chlorinated hydrocarbons during remediation and/or natural attenuation in iron-reducing environments.     

Spectroscopic study of copper(II)--wheat straw cell wall residue surface complexes

The sorption of copper(II) by wheat straw cell wall residue (CWR) was studied and revealed a relatively stable surface complexation on the acid sites of the substrate (carboxylic and phenolic moieties). The copper binding capacity at pH = 5.75 and ionic strength of 0.1 M was evaluated at 63 micromol x g(-1) CWR. The Langmuir and Freundlich isotherm equations were then used to describe the partitioning behavior for the system at different pH values. Batch experiments have been achieved in the presence of calcium in order to mimic the calcareous soil of the Champagne region. A competitive effect on copper complexation has been shown, which is presumably due to the calcium ability to form outer-sphere complexes far less stable than copper(II) ones. Electron spin resonance and X-ray absorption spectroscopy were combined to obtain information on the geometry and structure of Cu bound to CWR. At least two different binding sites for Cu2+ were found to take place in CWR. From ESR parameters, we deduced that copper(II) ions, when complexed with CWR, are coordinated in a square-planar arrangement with four oxygen-containing groups. EXAFS and XANES experiments revealed that Cu(II) is surrounded by four oxygen atoms, with an average Cu-O equatorial distance equal to 1.94 A.