Equilibrium adsorption isotherms for basic dyes onto lignite

The adsorption of two basic dyes in aqueous solutions onto lignite is reported. The adsorption equilibrium isotherms are recorded for the dyes in single component solution. The isotherms are plotted to obtain the Freundlich constants, the Langmuir constants, and the Redlich-Peterson constants.     

The Adsorption of Pollutants by Peat,Lignite and Activated Chars

The ability of peat, lignite and activated chars made from peat and lignite to adsorb dyes and metals from wastewater and NO₂ from air was investigated. Equilibrium isotherms were determined to assess the maximum adsorption capacity of the adsorbents for the pollutants. Kinetic studies for the adsorption of dyes and metal ions onto the adsorbents were undertaken in agitated batch adsorbers. Mass transport models were tested to predict the concentration decay curves in batch adsorbers. The models tested were single resistance models based on the assumption of a single external mass transfer coefficient and two resistance models which included an internal diffusion coefficient and an external mass transfer coefficient. The surface phenomena which influence the extent and the rate of uptake have been studied. The equilibrium capacity data conform to Langmuir plots. A previously proposed model was used to evaluate the external single resistance mass transfer model and was successfully applied to predict the adsorption of metal ions in single component systems under batch conditions. It has been shown that the assumption of negligible intraparticle diffusion is valid and that external film diffusion is the rate limiting step in describing the adsorption processes at high sorbent loadings. The same type of result is not observed for the adsorption of coloured organic matter onto peat where the sorption processes cannot be successfully modelled by use of a single resistance model and a two resistance model incorporating internal diffusion is required. The surface phenomena which influence the extent and the rate of uptake of NO₂ have been studied. The type of chars produced and the activation processes affect the adsorption. As activation increases, micropore volume and surface area increase and the maximum capacity of the adsorbent increases. Surface area alone is not the only parameter which affects equilibrium uptake. © 1997 SCI.     

Retention of metallic cations by lignites and humic acids

Adsorption of strontium, lead, uranium and thorium ions from their solutions by several Spanish lignites have been studied. Adsorption isotherms are adequately described by means of the Langmuir equation and can be characterized by two numerical constants: the sorption capacity of lignite, and the geochemical enrichment factor (GEF). Very high values of this GEF have been found for heavy metals. Humic acids were extracted from the lignites and their metal binding ability was determined as a function of pH. Higher pH favours metal retention, also higher atomic weight and valency. A role of humic substances in the retention and accumulation of metals in coals is suggested.     

Nickel and copper removal from aqueous solution by an immature coal (leonardite): effect of pH,contact time and water hardness

The removal of Ni(II) and Cu(II) from aqueous solutions by a low cost sorbent (leonardite) was studied. The metal uptake was pH‐dependent and the maximum sorption for two metals was obtained at around pH 5–6. Batch kinetic studies showed that equilibrium time was reached after 2 h of contact time. Equilibrium isotherms were obtained for the adsorption data of the two metals in single and binary systems. Equilibrium data were fitted to Langmuir and Freundlich models and the maximum adsorption capacities were found to be 0.33 mmol of copper and 0.26 mmol of nickel per gram of leonardite. In binary solutions containing the two metals an important reduction of nickel uptake was observed while the sorption of copper was less affected. The presence of Ca²⁺ affected the removal of both copper and nickel ions, although the adsorption of nickel was reduced more than that of copper. Copyright © 2005 Society of Chemical Industry     

Equilibrium Parameters for the Sorption of Copper,Cadmium and Zinc Ions onto Peat

This paper details a study into the sorption of three divalent metal ions—namely cadmium, copper and zinc—onto peat, in single component, binary and ternary systems. The Langmuir Freundlich and Redlich–Peterson equilibrium isotherms for each metal ion in each system have been determined and correlated. The Langmuir isotherms have been found to have the highest regression correlation coefficients. © 1997 SCI.     

Sorption isotherms of metal ions onto an N-(2-sulfoethyl)chitosan-based material from single- and multi-component solutions

The scope of work is to study the mutual influence of metal ions during their sorption by sulfoethylated chitosan. The sorption isotherms of metal ions from single- and multi-component solutions are obtained. The sorption capacity of the sorbent towards Ag(I) and Cu(II) is revealed to be 1.63 and 1.41 mmol/g in single-, and 1.40 and 0.85 mmol/g in five-component solution. By comparing the affinity parameter and capacity of sulfoethylated chitosan towards ions in single- and multi-component solutions, it is concluded that Ag(I) and Cu(II) ions suppress the sorption of cobalt(II), nickel(II), zinc(II), cadmium(II), magnesium(II), calcium(II), strontium(II), barium(II), manganese(II) and lead(II).     

Comparison of Experimental and Simulated Adsorption of Binary Metal Ions using Sawdust Modified by Citric Acid

With the aim of removing binary metal ions from aqueous solutions, the adsorption characteristics of sawdust modified with citric acid are investigated using adsorption kinetics and isotherms in both an experiment and a numerical simulation. The adsorption of metal ions is characterized by the competitive adsorption in binary metal ion systems that results from the stability constants between metal ions and citrate in the modified sawdust. These findings suggest that competitive adsorption and the affinities of the metal ion adsorbents play important roles in the removal of metal ions and that the numerical simulation can predict the adsorption characteristics of the modified sawdust.     

Removal of Cu(II) from aqueous solutions by recycled tire rubber

A batch adsorption system was applied to study the adsorption of Cu(II) ions from aqueous solutions by crumb rubber. The effects of pH ranging from 1.5 to 7.0, contact time ranging from 6 to 96 h and initial metal concentration ranging from 1 mg L^− 1 to 50 mg L^− 1 on the removal of Cu(II) were studied. Results show that adsorption of Cu(II) is pH-dependent and the best results are obtained at pH = 6.0. Results also show that copper uptake is accompanied by displacement of zinc and therefore probably involves an ion exchange type mechanism. Langmuir and Freundlich adsorption models were applied to describe the isotherms and isotherm constants. Equilibrium data agreed very well with the Langmuir model. Results clearly show that crumb rubber is an effective adsorbent for the removal of Cu(II) from aqueous solutions.     

Copper and cadmium extraction from highly concentrated phosphoric acid solutions using calcium alginate gels enclosing bis(2,4,4‐trimethylpentyl)thiophosphinic acid

The availability of alginate gels enclosing Cyanex 302 [bis(2,4,4‐trimethylpentyl)thiophosphinic acid] for the uptake of cadmium and copper from highly concentrated solutions of industrial phosphoric acid wet process phosphoric acid (WPA)] was studied. For this purpose, beads of alginate gels enclosing microdrops of kerosene solutions of the industrial extractant Cyanex 302 at different concentrations were prepared. The experimental procedure gives rise to a composite bead in which alginate is the continuous phase and the organic extractant forms the discrete homogeneously distributed phase within the bead. The equilibrium in this three‐phase system (phosphoric acid–extractant solution–alginate gel) was modelled in terms of the corresponding distribution factors, the main chemical reactions and their equilibrium constants. Retention isotherms of both metal ions were obtained experimentally at four concentrations (1.0, 2.5, 5.0 and 7.5 mol L^?1) of pure phosphoric acid. High metal removal efficiency, due to liquid–liquid extraction processes, was observed even in the most acidic conditions. High values of the extraction constants were estimated, with the distribution coefficients between aqueous and alginate phase being near unity. Finally, the results obtained with industrial WPA are in close agreement with those predicted by the physicochemical model developed in synthetic media. Copyright © 2006 Society of Chemical Industry     

Removal of metal ions using lignite in aqueous solution—Low cost biosorbents

Turkish lignite can be used as a new adsorption material for removing some toxic metals from aqueous solution. The adsorption of lignite (brown young coals) to remove copper (Cu²⁺), lead (Pb²⁺), and nickel (Ni²⁺) from aqueous solutions was studied as a function of pH, contact time, metal concentration and temperature. Adsorption equilibrium was achieved between 40 and 70 min for all studied cations except Pb²⁺, which is between 10 and 30 min. The adsorption capacities are 17.8 mg/g for Cu²⁺, 56.7 mg/g for Pb²⁺, 13.0 mg/g for Ni²⁺ for BC₁ (Ilg?n lignite) and 18.9 mg/g for Cu²⁺, 68.5 mg/g for Pb²⁺, 12.0 mg/g for Ni²⁺ for BC₂ (Beysehir lignite) and 7.2 mg/g for Cu²⁺, 62.3 mg/g for Pb²⁺, 5.4 mg/g for Ni²⁺ for AC (activated carbon). More than 67% of studied cations were removed by BC₁ and 60% BC₂, respectively from aqueous solution in single step. Whereas about 30% of studied cations except Pb²⁺, which is 90%, were removed by activated carbon. Effective removal of metal ions was demonstrated at pH values of 3.8–5.5. The adsorption isotherms were measured at 20 °C, using adsorptive solutions at the optimum pH value to determine the adsorption capacity. The Langmuir adsorption isotherm was used to describe observed sorption phenomena. The rise in temperature caused a slight decrease in the value of the equilibrium constant (K_c) for the sorption of metal ions. The mechanism for cations removal by the lignite includes ion exchange, complexation and sorption. The process is very efficient especially in the case of low concentrations of pollutants in aqueous solution, where common methods are either economically unfavorable or technically complicated.     

Selective removal of copper ions from aqueous solutions using modified silica beads impregnated with LIX 84

Silica beads immobilized with 2‐hydroxy‐5‐nonylacetophenoneoxime (LIX 84) were prepared after silica surface modification by γ‐aminopropyltriethoxysilane (SB‐L). Batch and packed‐column tests were conducted to evaluate the metal ion removal capabilities of the prepared adsorbent. Equilibrium isotherms of the SB‐L with aqueous solutions containing copper ions were obtained. In addition, the kinetic performances for copper ion removal from aqueous solutions were investigated. The results showed that the amount of extraction increases with solution pH in the range between 1.5 and 5. The selectivity was also experimentally investigated, these results showed that the SB‐L adsorbed copper ions selectively in the presence of other metal ions such as Ni²⁺, Co²⁺, Zn²⁺, Cd²⁺, Ca²⁺ and Mg²⁺. From the regeneration experiments, it was found that the copper ions adsorbed at the SB‐L surface were recovered by acidic solutions. The recovery ratios were between 78% and 90%, depending on the types of acidic solutions. The results showed that the SB‐L prepared may be used for the selective extraction of copper ions from aqueous solutions. © 1999 Society of Chemical Industry     

Adsorption and complexation mechanisms of heavy metal uptake in activated sludge

Differences were observed between the uptake of cadmium, copper, manganese and nickel by activated sludge biomass: their removal was studied when a range of metal concentrations was added to resuspended mixed liquor solids in the absence of possibly competitive organic ligands. The predominant mechanism of metal removal was passive uptake with some indication of binding site specificity for copper and possibly manganese. The data obtained were interpreted in the form of adsorption isotherms. The results were used to calculate conditional stability constants (K′) of the complexes formed, and the complexation capacity of the biomass for heavy metal uptake. Studies were conducted over a range of sludge ages from 3 to 12 days. Log₁₀K′ values between 4.6 and 6.7 were found. However, there was no direct relationship between sludge age and K′. EDTA was used to desorb bound metal: this provided a means of differentiating between the surface complexes and the unexchangeable metal such as that taken up intracellularly. There was a difference in the adsorption affinity series of the metals when EDTA was present. This indicated that more than one mechanism for metal uptake was operating, and that the relative importance of physical and chemical absorption varied with each metal.     

Binary component sorption of Cu(II) and Pb(II) with activated carbon from Eucalyptus camaldulensis Dehn bark

The objective of this work is to illustrate the potential in the use of activated carbon in the binary component sorption of copper and lead ions. Eucalyptus bark was used as a precursor for the activated carbon which was prepared through the phosphoric acid activation process. This activated carbon was then used for the sorption of copper and lead ions. The quantity of the metal ions in the solution was measured with the Flame & Graphite Furnace Atomic Adsorption Spectrophotometer. The results indicated that the optimal pH for sorption was 5. The maximum sorption capacities for Cu(II) and Pb(II) were 0.45 and 0.53 mmol g⁻¹. Carboxylic, amine and amide groups were found to involve in the sorptions of Cu(II) and Pb(II). A major mechanism for the uptake of both heavy metals was proven not to be ion exchange but adsorption. In binary component sorptions, activated carbon still could sorb Pb(II) in a greater amount than Cu(II). However, the presence of the secondary metal ions suppressed the sorption of the primary metal ions. There seemed to have a linear inverse dependency between the sorption capacity and the concentration of the secondary metal ion.     

EFFECT OF COPPER AND CADMIUM BINDING ON FLOCCULATION OF FERRIC OXIDE PARTICLES

ABSTRACT

The sorption of copper and cadmium ions from aqueous solutions by ferric oxide particles was studied using batch equilibrium and kinetic experiments. The sorption process was found to be pH dependent, with the uptake increasing at high pH values. An increase in equilibrium pH was observed when the initial pH was in the acidic range, and a decrease from initial values was observed in the basic range, in the case of both copper and cadmium sorption. The former phenomenon is due to competition between metal and proton binding, and the latter is due to precipitation mechanisms at high initial pH values. A large increase in the zeta potential of the particles from baseline values was observed during equilibrium sorption. This increase occurs as a result of surface charge neutralization due to metal ion uptake. Particle destabilization appears to occur as a result of metal ion sorption. Kinetic experiments indicate that the uptake of copper by ferric oxide particles is a slow process. The pH histories were similar to those obtained in the sorption equilibrium experiments. Changes in the size distribution of the ferric oxide particles due to aggregate formation during uptake of ions were observed in the kinetic studies. These findings indicate a potential role of metal ion uptake in particle flocculation kinetics through alteration of the surface electrostatic potential.     

A model for the adsorption of single metal ion solutes in aqueous solution onto activated carbon produced from pecan shells

Adsorption isotherms for activated carbon made from pecan shells have been obtained at 25 °C and an approximate pH of 3 for a number of metal ion solutes. It was found that the Slips and Freundlich equations were satisfactory for explaining the experimental data. The correlation of metal ion adsorption with the solute parameters of metal ion electronegativity and first stability constant of the metal hydroxide was investigated. In the case of most of the metal ions studied, higher electronegativities and stability constants corresponded to the higher adsorption levels of metal ions onto the activated carbon. A correlation was developed that predicts the constants of the Freundlich equation from the selected parameters of the metal ions, and thus can predict the adsorption isotherms at constant pH. The developed correlation gives results with acceptable deviations from experimental data. A procedure is proposed for obtaining similar correlations for different conditions (temperature, pH, carbon type and dosage). The ratio of equivalent metal ions adsorbed to protons released is calculated for the studied metal ions over a range of concentrations. In most cases, particularly at low concentrations, this ratio is close to one, confirming that ion exchange of one proton with one equivalent metal ion is the dominant reaction mechanism.     

趋磁细菌对金属离子的吸附特性研究

研究了单元体系和三元体系中趋磁细菌(MTB)对Au3 ,Cu2 和Ni2 的吸附特性,用Langmuir吸附等温模型拟合了吸附等温线实验数据。较高的相关系数表明该吸附过程可以用Langmuir模型来描述。在三元体系竞争吸附实验中,MTB对Au3 的吸附量较之单元系统有所增加,而Cu2 和Ni2 的吸附量明显降低。吸附动力学实验结果表明,MTB对三种金属离子的吸附都属于快速过程,对Au3 的吸附在短时间内可完成,而且几乎完全吸附。所有吸附过程均符合拟二阶动力学模型。     

Nerve Growth Factor Peptides Bind Copper(II) with High Affinity: A Thermodynamic Approach to Unveil Overlooked Neurotrophin Roles

Nerve growth factor (NGF) is a protein essential to neurons survival, which interacts with its receptor as a non-covalent dimer. Peptides belonging to NGF N-terminal domain are able to mimic the activity of the whole protein. Such activity is affected by the presence of copper ions. The metal is released in the synaptic cleft where proteins, not yet identified, may bind and transfer to human copper transporter 1 (hCtr1), for copper uptake in neurons. The measurements of the stability constants of copper complexes formed by amyloid beta and hCtr1 peptide fragments suggest that beta-amyloid (Aβ) can perform this task. In this work, the stability constant values of copper complex species formed with the dimeric form of N-terminal domain, sequence 1–15 of the protein, were determined by means of potentiometric measurements. At physiological pH, NGF peptides bind one equivalent of copper ion with higher affinity of Aβ and lower than hCtr1 peptide fragments. Therefore, in the synaptic cleft, NGF may act as a potential copper chelating molecule, ionophore or chaperone for hCtr1 for metal uptake. Copper dyshomeostasis and mild acidic environment may modify the balance between metal, NGF, and Aβ, with consequences on the metal cellular uptake and therefore be among causes of the Alzheimer’s disease onset.     

Competitive Biosorption of Acid Dyes from Binary Solutions onto Enteromorpha prolifera: Application of the First Order Derivative Spectrophotometric Analysis Method

The biosorption of Acid Red 274 and Acid Red 337 dyes from single and binary solutions on Enteromorpha prolifera was investigated in a single stage batch system. The first order derivative spectrophotometry was tested in order to analyse the studied binary solutions of the selected dyes. The single- and multi-component Langmuir and Freundlich isotherm models were applied to the experimental equilibrium data and the isotherm parameters were estimated. It was observed that the uptake amounts of the first component decreased with increasing concentration of the second component from binary solution. As a result, the binary biosorption of AR274 and AR337 dyes on E.prolifera have an antagonistic effect. The binary biosorption of AR274 and AR337 dyes in a single stage batch system was modelled and the equilibrium concentrations of the exit stream were found by using the experimental equilibrium curves and operating lines for the biosorption of single and binary dye solutions.     

Removal of Cu2+ and Pb2+ ions from aqueous solutions by starch-graft-acrylic acid/montmorillonite superabsorbent nanocomposite hydrogels

In this study, the removal of copper(II) and lead(II) ions from aqueous solutions by Starch-graft-acrylic acid/montmorillonite (S-g-AA/MMT) nanocomposite hydrogels was investigated. For this purpose, various factors affecting the removal of heavy metal ions, such as treatment time with the solution, initial pH of the solution, initial metal ion concentration, and MMT content were investigated. The metal ion removal capacities of copolymers increased with increasing pH, and pH 4 was found to be the optimal pH value for maximum metal removal capacity. Adsorption data of the nanocomposite hydrogels were modeled by the pseudo-second-order kinetic equation in order to investigate heavy metal ions adsorption mechanism. The observed affinity order in competitive removal of heavy metals was found Cu²⁺ > Pb²⁺. The Freundlich equations were used to fit the equilibrium isotherms. The Freundlich adsorption law was applicable to be adsorption of metal ions onto nanocomposite hydrogel.     

Palladium Recovery from Dilute Effluents using Biopolymer‐Immobilized Extractant

Abstract

Cyanex 301‐immobilized material (prepared by immobilization into an alginate matrix) was tested for Pd sorption in 1 M HCl solutions with a special attention to sorption isotherms and uptake kinetics. This immobilized extractant had great affinity for Pd, as shown by the initial slope of the sorption isotherms. Sorption capacities as high as 150 mg Pd g^?1 were obtained in 1 M HCl solutions. However, kinetics was slow, compared to conventional resins. The main limiting step in the process is the diffusion of metal ions into the matrix. The influence of parameters such as HCl concentration, NaCl addition, presence of Pt (as a competitor metal) has been checked. It appeared that sorption performance of Cyanex 301‐immobilized material was hardly influenced by the addition of NaCl and by HCl concentration (below 2.5 M). The resin was remarkably selective for Pd, versus Pt, especially at 1 M HCl concentration. Loaded resins can be desorbed using thiourea solutions.