Copper(II) removal from aqueous solutions by fly ash

The removal of Cu(II) by adsorption on fly ash has been found to be concentration, pH and temperature dependent. The kinetics of adsorption indicates the process to be diffusion controlled. The Langmuir constants have been calculated at different temperatures, and the adsorption has been found to be endothermic (ΔH = 15.652 kcal mol^?1). The maximum removal is observed at pH 8.0, and variation in adsorption with pH has been explained on the basis of surface ionisation and complexation.     

Pb(II)、Cu(II)、Cd(II)在黄土上二元竞争吸附特性研究

铅、铜、镉是3种具有代表性的重金属污染物,可用于模拟多重离子复合污染情况。研究了离子浓度、土水比等因素对3种元素在黄土上二元竞争吸附特性的影响。等温吸附模型Langmuir、Freundlich和D-R模型都能在一定程度上解释Pb(II)-Cu(II)、Pb(II)-Cd(II)、Cu(II)-Cd(II)在黄土上的竞争吸附性能。黄土对Pb(II)、Cu(II)、Cd(II)的选择顺序为Pb(II)>Cu(II)>Cd(II)。相比单一吸附,黄土对每种离子的吸附容量均有不同程度的下降。溶液的初始浓度越大,3种离子在单位黄土上的最大吸附量也随之增大,吸附效率随之降低;适当增大土水比可提高离子的去除效率。试验结果为黄土作为防污屏障和污水处理材料提供了依据。     

Adsorption characteristics of some Cu(II) complexes on aluminosilicates

The adsorption of Cu(II) by aluminosilicates with varying Si/Al ratios was investigated. The presence of complex-forming organic ligands [nitrilotriacetate (NTA) and glycine (Gly)] alters metal electrovalency and, in so doing, modifies Cu(II) adsorption characteristics which can influence its fate, biological activity and transport in aquatic systems. Electrostatic attraction by a positively-charged aluminosilicate surface is an important mechanism whereby anion CuNTA⁻ complexes were adsorbed. Two distinct mechanisms are involved in the adsorption of cationic complexes: (1) an exchange reaction at permanent structural sites and (2) interfacial accumulation in response to the pH-dependent surface charge. The contribution of each mechanism to the total amount of CuGly⁺ adsorbed is related to the Si/A1 ratio. At the critical Si/A1 ratio (Si/A1_iso), the aluminosilicates have zero net pH-dependent surface charge. In the absence of specific adsorption, aluminosilicates for which Si/A1 ≥ Si/A1_iso can only function as cation exchangers. For Si/A1 < Si/A1_iso simultaneous adsorption of anions and cations is possible.     

Potential of zero-valent iron in remediation of Cd(II) contaminated soil: From laboratory experiment,mechanism study to field application

This study investigates the potential of ZVI on Cd(II) contaminated soil remediation through laboratory experiment, mechanism study and field application. The results show that the dosage of ZVI, the initial concentration level and the reaction time have significant impacts on Cd(II) adsorption and about 88% of aqueous Cd(II) can be removed from soils. The ZVI is observed to promote the increase of Cd(II) residual fraction in Cd(II) contaminated soils according to the sequential extraction procedure (SEP) results. Regression of the laboratory experimental data based on the Langmuir isotherm equation shows the adsorption capacity can reach 34.7 mg/g. Such a high value is attributed to physical and chemical adsorption, which is proved by X-ray diffraction patterns (XRD), scanning electron microscope images (SEM), and Brunner-Emmet-Teller & Barret–Joyner–Halenda (BET-BJH) analysis. The field application shows that the ZVI can reduce the Cd(II) content in soils and brown rice by 51% and alleviate soil acidification, resulting in a 9.4% increase in rice yields.     

Adsorption of Cu(II) to schwertmannite and goethite in presence of dissolved organic matter

Sorption processes involving secondary iron minerals may significantly contribute to immobilisation of metals in soils and surface waters. In the present work the effect of dissolved organic matter (DOM) from a concentrated bog-water on the adsorption of Cu(II) onto schwertmannite (Fe₈O₈(OH)₆SO₄) and goethite (α-FeOOH) has been studied. The acid/base behaviour of DOM up to pH 6 was explained by assuming a diprotic acid with a density of carboxylate groups of 6.90 μeq (mg C)⁻¹. The resulting acidity constants, recalculated to zero ionic strength were and .The uptake of DOM to schwertmannite and goethite was highest at low pH although adsorption was significant also under mildly alkaline conditions. Adsorption to the two minerals was similar although at high pH more DOM was adsorbed to schwertmannite than to goethite.DOM enhanced the adsorption of Cu(II) at moderately low pH in the goethite system but there was no effect of DOM in the case of schwertmannite. The presence of Cu(II) resulted in a decreased adsorption of DOM to goethite at weakly acidic pH and increased adsorption at high pH. In the case of schwertmannite, Cu(II) did not affect DOM uptake.     

Adsorption for removal of Cd(II) from effluents

The adsorption of Cd(II) onto wollastonite has been reported. Adsorption increased from 55.7 to 93.6% by decreasing the concentration of Cd(II) from 2.0 x 10^‐4M to 0.5 x 10^‐4M. The rearranged Lagergren equation has been used for dynamic modelling of the process. However, the value of rate constant at 30°C was found to be 3.17 x 10^‐2min^‐1. Equilibrium modelling was carried out using the Freundlich isotherm equation and constants have been calculated. Thermodynamic studies were carried out and values of standard free energy (?G°), enthalpy (?H°) and entropy (AS°) were calculated at various temperatures. Low temperatures favour the uptake of Cd(II) in the process.     

Adsorption of Zn(II) in Oxisols as affected by selective removal of soil fractions

The relative contribution of organic matter, amorphous and crystalline Fe oxides and Al oxides to soil Zn adsorption was evaluated in contaminated and uncontaminated Brazilian soils. Soil samples were equilibrated with Zn solutions and Zn adsorption was determined using the Langmuir adsorption isotherm. The Fe and Al oxides (non‐silicated clays) and the organic matter contents of the soils were the main contributors to the variation in Zn adsorption. The Zn maximum adsorption capacity in the soil with the greatest sand and organic carbon contents was higher than in the higher clay content soil, which was second in organic carbon content. Related to the whole soil samples, as the soil organic matter was removed, the Zn maximum adsorption capacity decreased in most of the observations. The removal of Fe and Al oxides decreased the soil Zn maximum adsorption capacity in some cases and increased it in others, with no clear variation in the pathway. For both whole soil and soil fractions, the isotherms for Zn adsorption to soil, fitted to the Langmuir equation, showed two linear portions or pathways (Part I and Part II). The bonding energy coefficient was higher in Part I (related to specific chemical adsorption) than in Part II (related to electrostatic interactions), which suggests a higher affinity between Zn and soil particles in Part I as compared with Part II.     

Speciation (including adsorbed species) of copper, lead, nickel and zinc in the Meuse River: Observed results compared to values calculated with a chemical equilibrium computer program

The adsorption of trace metals on sediments of the Meuse River was interpreted in terms of competition between metals and protons for surface sites. Surface constants (^*β₁^surf) were determined for Cu, Zn and Cd (10^−1.8, 10^−3.6 and 10^−3.7). The constants for Pb, Ni, Ca and Mg (10^−1.7, 10^−3.8, 10^−6.5 and 10^−5.2) were estimated using a correlation between hydrolysis and surface constants. A chemical equilibrium computer program in which surface sites (for adsorption reactions) are treated as conventional ligands was used to calculate the speciation of Cu, Pb, Ni and Zn in the Meuse River. Calculated values of the adsorbed/dissolved distribution agreed well with observed values, after some realistic data manipulation. This work indicates that dissolved trace metal concentrations in the Meuse River are controlled by adsorption and not by precipitation mechanisms. The relationship between organic matter and suspended matter greatly influences the adsorption of metals like Cu and Pb.     

Recovery of chromium(VI) from wastewaters with iron(III) hydroxide—I: Adsorption mechanism of chromium(VI) on iron(III) hydroxide

Chromium(VI) [Cr(VI)] is adsorbed as HCrO⁻₄ on iron(III) hydroxide at pH below 8.5. The Cr(VI) adsorption is suppressed by the presence of other anions such as SO²⁻₄ and SCN⁻, and enhanced by the presence of metal ions such as Cd(II) and Pb(II). The suppression is due to the competitive adsorption of other anions, depending upon the stability of their iron complexes. The enhancement is probably due to the increase in adsorption sites as a result of coprecipitation of metal ion with iron(III) hydroxide.     

Comparative and competitive adsorption of Cu(II), Cd(II) and Pb(II) onto Sepia pharaonis endoskeleton biomass from aqueous solutions

In this research, the possibility of simultaneous removal of lead, cadmium and copper divalent ions from water samples through the use of Sepia pharaonis endoskeleton powder (SPEB) as bio‐material, was investigated. The bio‐sorbent was characterised by Fourier transform infrared spectrum (FT‐IR), atomic force microscopy (AFM) and X‐ray fluorescence (XRF). The different factors affecting the bio‐sorption process were studied. Langmuir and Freundlich isotherm models were applied to analyse the experimental data. The kinetic studies showed that the pseudo‐second order model kinetics were compatible with the investigated systems. It was found that under optimal conditions, this bio‐sorbent was efficient in the uptake of these heavy metal ions from both mono and multi‐metal solutions, and high removal percentages were achieved. This study verified the potential ability of SPEB as an efficient natural adsorbent for removal of Pb(II), Cd(II) and Cu(II) ions from river, tap and mineral water samples.     

Removal of Cu(II) and Cd(II) from aqueous solution by seafood processing waste sludge

Dried waste slurry generated in seafood processing factories has been shown to be an effective adsorbent for the removal of heavy metals from dilute solutions. Characterization of the sludge surface with scanning electron microscope and X-ray microanalyzer were carried out to evaluate the components on the sludge surface that are related to the adsorption of metal ions. Aluminum and calcium, as well as organic carbon are distributed on the surface of sludge. Alkalimetric titration was used to characterize the surface acidity of the sludge sample. The surface acidity constants, pKa1s and pKa2s, were 5.80 and 9.55, respectively. Batch as well as dynamic adsorption studies were conducted with 10(-5) to 5 x 10(-3) M Cu(II) and Cd(II). A surface complexation model with the diffuse layer model successfully predicted Cu(II) and Cd(II) removals in single metal solutions. Predictions of sorption in binary-adsorbate systems based on single-adsorbate data fits represented competitive sorption data reasonably well over a wide range of conditions. The breakthrough capacity found from column studies was different for each metal ion and the data reflect the order of metal affinity for the adsorbent material very well.     

Adsorption of Cu(II) and Pb(II) onto a grafted silica: isotherms and kinetic models

The isotherms and kinetics of adsorption of lead(II) and copper(II) onto a grafted silica are studied at 20 degrees C. A commercial silica is grafted with an ethylediamine derivative, N-[3-(trimethoxysilyl)propyl]-ethylenediamine. From the Langmuir isotherms, maximum adsorption capacities of the grafted silica towards Pb(II) and Cu(II) are determined (0.184 mmol Pb(II)g-1 and 0.261 mmol Cu(II)g-1) and compared to those of non-modified silica (respectively, 0.019 and 0.036 mmol g-1). Four kinetic models, i.e., pseudo-first order, pseudo-second order, Langmuir and double-exponential are applied to fit the experimental kinetic data. The kinetic parameters are determined which allow to calculate the theoretical metal uptake as a function of time. The results are discussed and indicate the best fit is obtained with the double-exponential model. A discussion on the adsorption mechanism with respect to the double-exponential model leads to two possible interpretations: the metal uptake may follow a diffusion-controlled mechanism or a two-site adsorption process.     

Displacement mechanism of binary competitive adsorption for aqueous divalent metal ions onto a novel IDA-chelating resin: isotherm and kinetic modeling

Adsorptive properties for Cu (II), Pb (II) and Cd (II) onto an iminodiacetic acid (IDA) chelating resin were systematically investigated at the optimal pH-value in both single and binary solutions using batch experiments. The Langmuir isotherm model and the pseudo second-order rate equation could explain respectively the isotherm and kinetic experimental data for sole-component system with much satisfaction. The maximum adsorption capacity in single system for Cu (II), Pb (II) and Cd (II) was calculated to be 2.27 mmol/g, 1.27 mmol/g and 0.65 mmol/g individually. The initial adsorption rate followed the order as Cu (II) > Pb (II) > Cd (II) at the fixed initial concentration, and for each metal the initial sorption rate increased as the initial concentration increased. In addition, the modified Langmuir model could describe the binary competitive adsorption behavior successfully, with which the interaction coefficient was obtained to follow the order as Cu (II) < Pb (II) < Cd (II). Furthermore, in every case of the investigated three binary systems, the reduction in both the uptake amounts and distribution coefficients testified the antagonistic competitive phenomena. Obviously, this novel IDA-chelating resin possessed of a good selectivity toward Cu (II) over Pb (II) and Cd (II) for the obtained highest separation factor values were up to 21.30 and 133.91 in the range of tested. This interaction mechanism between the favorable component and other metal ions could mainly contribute to the direct displacement impact which be herewith illustrated schematically.     

Toxicity of lipid-soluble copper(II) complexes to the marine diatom Nitzschia closterium: Amelioration by humic substances

Algal assays, using the marine diatom Nitzschia closterium, have established that humic acid (5 mg kg⁻¹) can ameliorate the toxicity of the lipophilic complex Cu(oxine)₂ (3 × 10⁻⁸ mol l⁻¹ in unsupplemented seawater). The toxicity of Cu(PAN)₂ is not ameliorated [PAN = 1-(2-pyridylazo)-2-napthol]. In conjunction with previous visible absorption spectrophotometry and polarographic measurements it was established that humic acid sequesters copper(II) from the hydrophobic complexes, releasing a ligand molecule. The copper(II) toxicity may be ameliorated provided the ligand itself is not toxic.Fulvic acid was significantly less effective in ameliorating toxicity. Because of the significant competition from Ca(II) and Mg(II) in seawater, it is inferred that humic substances may be more effective in ameliorating toxicity of hydrophobic copper complexes in fresh water.     

Synthesis,characterisation of ternary layered double hydroxides (LDH) for sorption kinetics and thermodynamics of Cd2+

Kinetic and thermodynamic studies were carried out on the sorption of Cd²⁺ on three synthesised and characterised layered double hydroxides, namely: Ni-Co-Ti, Ni-Co-La and Mn-Ni-Al-CO₃. Sorption kinetics were investigated through time-dependent studies. Thermodynamics were determined by the effect of temperature on adsorption. Kinetic modelling of the adsorption of Cd(II) ions on the LDHs was determined using the first-order, pseudo-first order, pseudo-second order and Elovich kinetic models, as well as additional diffusion models. The results showed that the pseudo-second-order model best correlated the adsorption data with R² values of 1.000, 0.998 and 1.000 for NiCoTi, NiCoLa and MnNiAl-LDH respectively. Diffusion of the adsorbate was best correlated by the Weber-Morris intraparticle diffusion model with R² values of 0.9753, 0.8472 and 0.9412 for NiCoTi, NiCoLa and MnNiAl-LDH respectively. Thermodynamic studies showed that the adsorption was spontaneous and exothermic with a high probability of sticking.     

Removal of mercury(II) from aqueous solutions and chlor-alkali industry wastewater using 2-mercaptobenzimidazole-clay

The 2-mercaptobenzimidazole loaded natural clay was prepared for the removal of Hg(II) from aqueous media. Adsorption of the metal ions from aqueous solution as a function of solution concentration, agitation time, pH, temperature, ionic strength, particle size of the adsorbent and adsorbent dose was studied. The adsorption process follows a pseudo-second-order kinetics. The rate constants as a function of initial concentration and temperature were given. The adsorption of Hg(II) increased with increasing pH and reached a plateau value in the pH range 4.0-8.0. The removal of Hg(II) was found to be >99% at an initial concentration of 50 mg/l. Mercury(II) uptake was found to increase with ionic strength and temperature. Further, the adsorption of Hg(II) increased with increasing adsorbent dose and decrease with adsorbent particle size. Sorption data analysis was carried out using Langmuir and modified Langmuir isotherms for the uptake of metal ion in an initial concentration range of 50-1,000 mg/l. The significance of the two linear relationships obtained by plotting the data according to the conventional Langmuir equation is discussed in terms of the binding energies of the two population sites involved which have a widely differing affinity for Hg(II) ions. Thermodynamic parameters such as changes of free energy, enthalpy, and entropy were calculated to predict the nature of adsorption. It was found that the values of isosteric heat of adsorption were varied with surface loading. The chlor-alkali industry wastewater samples were treated by MBI-clay to demonstrate its efficiency in removing Hg(II) from wastewater.     

Environmental assessment of a road site built with MSWI residue

A 23-year-old road built with MSWI residue (mix of fly and bottom ashes) was investigated through the environmental assessment of the residue, soils (adjacent to and underlying the road) and seepage waters. The pH and ANC_4.3 of the material indicate a low carbonation and a high alkaline stock. The material leaches few trace elements. The underlying road soil shows significant effects with respect to K and Na, attributable to the MSWI residue. Effects regarding Cd, Cr, Cu and Ni are observed, yet pollution thresholds are not exceeded. Compared to groundwater thresholds, the MSWI residue percolate is of poor to very poor quality (French reference system — FWQAS) in terms of pH, K, Na, Cl⁻, F⁻, As and Cu. It lies above the intervention values of the Dutch Soil Protection Act (DSPA) for Cu, Ni and Pb. Downstream, water from the road shoulder (W_Sdr) is of very poor quality with respect to Na and Cl⁻, and fair to poor quality regarding K. All other parameters comply with the best quality thresholds (FWQAS and DSPA). The high Cl⁻ concentration of W_Sdr would not fit for direct discharge in any watercourse. Toward a weakly-mineralised water, Cd and Cu would also be penalizing. The geometry of the road site creates penalizing conditions increasing the washing of the MSWI residue. The road structure does not cause downstream effect as regards trace elements, but effects exist for Cl⁻, Na and K. Opposite downstream effects are observed (Ca, Mg, Mn and SO₄²⁻) due to farming treatments and the nature of the local soil.     

Adsorption of Cu(II) from industrial liquid waste on Na-bentonite and Al-PILC following a full factorial design

The paper reports a study of the performance of Maghnia bentonite in a purified and modified state for the removal of Cu(II) from industrial liquid waste in the region of Oran (North West Algeria). Bentonite was firstly treated to produce a Na-bentonite, then modified with an aluminum solution containing molar ratio OH/Al of 1.8 and finally calcined at 450 °C. The polymer [AlO₄Al₁₂(OH)₂₄(H₂O)₁₂]⁷⁺ formed in solution was adsorbed by surface complexation on the bentonite, which is known to have a high capacity to fix metal cations. The prepared materials were characterized by DRX, BET and EDX. In order to find the optimum conditions, a full factorial design of 2⁴ allowed us to determine the main effects and interactions of the factors studied: pH, mass of materials, contact time and temperature. The results obtained show that the best rate of adsorption of copper requires a pH = 10, a mass = 0.8 g, a stirring time = 80 min, and a temperature = 25 °C. The adsorption capacity of treated bentonite increased considerably from 4.147 mg/g for Na-bentonite to 7.173 mg/g for pillared aluminum bentonite. This shows the strong adsorption of copper compared with Na-bentonite, caused by its high surface area.     

Enhanced adsorption of Cd (II) on a hydrous Al (III) floc in the presence of a modified form of polyethylenimine

A polymer modified with succinic anhydride has been investigated for the adsorption of cadmium (II) on a freshly precipitated aluminium (III) hydroxide floc. The proportion of chelate attached to the polymer is varied to determine the relationship between carboxyl and amino groups on the polyelectrolyte, in terms of enhanced adsorption of cadmium (II) on a hydrous aluminium floc. The presence of polyelectrolyte enhanced the adsorption of 3.3 ppm Cd (II) on a 333 ppm Al (III) floc at every concentration of polyelectrolyte investigated. The proportion of succinic anhydride attached to the polymer had an impact on the increased adsorption of Cd (II) on an Al (III) floc observed. A decreasing proportion of succinic anhydride to polymer resulted in a decrease in the amount of cadmium adsorbed on the floc. Above pH 8, a decrease in the % Cd (II) adsorbed on the floc and % Al (III) retained within the floc decreases with the presence of polyelectrolyte as a result of the formation of soluble Cd-Polyethylenimine-succinic acid (PEISA) complexes. When the Al-PEISA combination was applied to a complex matrix where Cd (II), Cu (II) and Ni (II) ions competed for adsorption, enhanced adsorption was observed for Cd (II) and Ni (II). At pH 7, dissolution of the floc observed with the addition of discrete chelates was not observed with the addition of polyelectrolytes.     

Removal of arsenic from water: Effect of calcium ions on As(III) removal in the KMnO4–Fe(II) process

A novel KMnO₄–Fe(II) process was developed in this study for As(III) removal. The optimum As(III) removal was achieved at a permanganate dosage of 18.6 μM. At the optimum dosage of permanganate, the KMnO₄–Fe(II) process was much more efficient than the KMnO₄–Fe(III) process for As(III) removal by 15–38% at pH 5–9. The great difference in As(III) removal in these two processes was not ascribed to the uptake of arsenic by the MnO₂ formed in situ but to the different properties of conventional Fe(III) and the Fe(III) formed in situ. It was found that the presence of Ca²⁺ had limited effects on As(III) removal under acidic conditions but resulted in a significant increase in As(III) removal under neutral and alkaline conditions in the KMnO₄–Fe(II) process. Moreover, the effects of Ca²⁺ on As(III) removal in the KMnO₄–Fe(II) process were greater at lower permanganate dosage when Fe(II) was not completely oxidized by permanganate. This study revealed that the improvement of As(III) removal at pH 7–9 in the KMnO₄–Fe(II) process by Ca²⁺ was associated with three reasons: (1) the specific adsorption of Ca²⁺ increased the surface charge; (2) the formation of amorphous calcium carbonate and calcite precipitate that could co-precipitate arsenate; (3) the introduction of calcium resulted in more precipitated ferrous hydroxide or ferric hydroxide. On the other hand, the enhancement of arsenic removal by Ca²⁺ under acidic conditions was ascribed to the increase of Fe retained in the precipitate. FTIR tests demonstrated that As(III) was removed as arsenate by forming monodentate complex with Fe(III) formed in situ in the KMnO₄–Fe(II) process when KMnO₄ was applied at 18.6 μM. The strength of the “non-surface complexed” As–O bonds of the precipitated arsenate species was enhanced by the presence of Ca²⁺ and the complexation reactions of arsenate with Fe(III) formed in situ in the presence or absence of Ca²⁺ were proposed.