The influence of pH,contact time,ionic strength,temperature, and fullerene on the adsorption of Cu(II) onto magnetic multi-walled carbon nanotubes

The influences of pH, contact time, absorbent dose, temperature and C₆₀(C(COOH)₂)_n on Cu(II) adsorption onto the magnetic multi-walled carbon nanotubes (MMWCNTs) were studied by batch technique. The dynamic process showed that the adsorption of Cu(II) onto MMWCNTs matched well with the pseudo-second-order kinetics model. The adsorption of Cu(II) onto MMWCNTs was dependent on pH values significantly, the adsorption percentage increased observably at pH 5.0–7.0, and then maintained a steady state with pH increased. Through simulating the adsorption isotherms by Langmuir, Freundlich and Dubini-Radushkevich models, respectively, it could be seen that the adsorption pattern of Cu(II) onto MMWCNTs was mainly surface complexation. The presence of C₆₀(C(COOH)₂)_n could enhance the adsorption content of Cu(II) onto MMWCNTs at low pH, but restrained that at higher pH.     

Removal of copper(II) and lead(II) from aqueous solution by manganese oxide coated sand I. Characterization and kinetic study

The preparation, characterization, and sorption properties for Cu(II) and Pb(II) of manganese oxide coated sand (MOCS) were investigated. A scanning electron microscope (SEM), X-ray diffraction spectrum (XRD) and BET analyses were used to observe the surface properties of the coated layer. An energy dispersive analysis of X-ray (EDAX) and X-ray photoelectron spectroscopy (XPS) were used for characterizing metal adsorption sites on the surface of MOCS. The quantity of manganese on MOCS was determined by means of acid digestion analysis. The adsorption experiments were carried out as a function of solution pH, adsorbent dose, ionic strength, contact time and temperature. Binding of Cu(II) and Pb(II) ions with MOCS was highly pH dependent with an increase in the extent of adsorption with the pH of the media investigated. After the Cu(II) and Pb(II) adsorption by MOCS, the pH in solution was decreased. Cu(II) and Pb(II) uptake were found to increase with the temperature. Further, the removal efficiency of Cu(II) and Pb(II) increased with increasing adsorbent dose and decreased with ionic strength. The pseudo-first-order kinetic model, pseudo-second-order kinetic model, intraparticle diffusion model and Elovich equation model were used to describe the kinetic data and the data constants were evaluated. The pseudo-second-order model was the best choice among all the kinetic models to describe the adsorption behavior of Cu(II) and Pb(II) onto MOCS, suggesting that the adsorption mechanism might be a chemisorption process. The activation energy of adsorption (E(a)) was determined as Cu(II) 4.98 kJ mol(-1) and Pb(II) 2.10 kJ mol(-1), respectively. The low value of E(a) shows that Cu(II) and Pb(II) adsorption process by MOCS may involve a non-activated chemical adsorption and a physical sorption.     

Adsorptive removal of Cu(II) from aqueous solutions using collagen-tannin resin

The collagen-tannin resin (CTR), as a novel adsorbent, was prepared via a reaction of collagen with black wattle tannin and aldehyde, and its adsorption properties to Cu(II) were systematically investigated, including pH effect, adsorption equilibrium, adsorption kinetics, and column adsorption. The adsorption capacity of Cu(II) on CTR was pH-dependent, and it increased with the increase of solution pH. The adsorption isotherms were well described by Langmuir isotherm model with correlating constant (R(2)) higher than 0.99. The adsorption capacity determined at 303 K was high up to 0.26 mmol/g, which was close to the value (0.266 mmol/g) estimated from Langmuir equation. The adsorption capacity was increased with the increase of temperature, and thermodynamic calculations suggested that the adsorption of Cu(II) on CTR is an endothermic process. The adsorption kinetics were well fitted by the pseudo-second-order rate model. Further column studies suggested that CTR was effective for the removal of Cu(II) from solutions, and more than 99% of Cu(II) was desorbed from column using 0.1 mol/L HNO(3) solution. The CTR column can be reused to adsorb Cu(II) without any loss of adsorption capacity.     

Competitive adsorption of copper(II), cadmium(II), lead(II) and zinc(II) onto basic oxygen furnace slag

Polluted and contaminated water can often contain more than one heavy metal species. It is possible that the behavior of a particular metal species in a solution system will be affected by the presence of other metals. In this study, we have investigated the adsorption of Cd(II), Cu(II), Pb(II), and Zn(II) onto basic oxygen furnace slag (BOF slag) in single- and multi-element solution systems as a function of pH and concentration, in a background solution of 0.01M NaNO(3). In adsorption edge experiments, the pH was varied from 2.0 to 13.0 with total metal concentration 0.84mM in the single element system and 0.21mM each of Cd(II), Cu(II), Pb(II), and Zn(II) in the multi-element system. The value of pH(50) (the pH at which 50% adsorption occurs) was found to follow the sequence Zn>Cu>Pb>Cd in single-element systems, but Pb>Cu>Zn>Cd in the multi-element system. Adsorption isotherms at pH 6.0 in the multi-element systems showed that there is competition among various metals for adsorption sites on BOF slag. The adsorption and potentiometric titrations data for various slag-metal systems were modeled using an extended constant-capacitance surface complexation model that assumed an ion-exchange process below pH 6.5 and the formation of inner-sphere surface complexes at higher pH. Inner-sphere complexation was more dominant for the Cu(II), Pb(II) and Zn(II) systems.     

Adsorption characteristics of heavy metal ions onto a low cost biopolymeric sorbent from aqueous solutions

In this study, the adsorption conditions of Cu(II), Pb(II) and Cd(II) metal ions onto sporopollenin have been studied. The different variables effecting the sorption capacity such as pH of the solution, adsorption time, initial metal ion concentration and temperature have been investigated. Adsorption isotherms correlated well with the Freundlich type adsorption isotherm and adsorption capacities were found to be 0.0195, 0.0411 and 0.0146 mmol g(-1) for Cu(II), Pb(II) and Cd(II) metal ions, respectively. Experimental data were also evaluated to find out kinetic characteristics of the adsorption process. Adsorption processes for three target heavy metal ions were found to follow pseudo-second order type adsorption kinetics. Intraparticle diffusion was found to take part in adsorption processes but it could not be accepted as the primary rate-determining step. The mean free energies of adsorption (E) were found to be between 8 and 16 kJ mol(-1) for the metal ions studied and therefore adsorption mechanism for the adsorbent was explained as an ion-exchange process. But it was observed that chelating effect is also playing an important role in the adsorption of metal ions onto sporopollenin. Thermodynamic parameters, DeltaH degrees , DeltaS degrees and DeltaG degrees were also calculated from graphical interpretation of the experimental data. Standard heats of adsorption (DeltaH degrees ) were found to be endothermic and DeltaS degrees values were calculated to be positive for the adsorption of Cu(II), Pb(II) and Cd(II) ions onto the adsorbent. Negative DeltaG degrees values indicated that adsorption process for these three metal ions onto sporopollenin is spontaneous.     

Copper(II) and zinc(II) biosorption on Pinus sylvestris L

The biosorption properties of copper(II) and zinc(II) onto a cone biomass of Pinus sylvestris L. was investigated by using batch techniques. The biosorption studies carried out with single metal solutions. The removal of copper(II) and zinc(II) from aqueous solution increased with pH and sharply decreased when pH of the solution was decreased. The maximum biosorption efficiency of P. sylvestris was 67% and 30% for Cu(II) and Zn(II), respectively. Batch kinetic and isotherm of biosorption metal ions were investigated. The second-order kinetic model was used to correlate the experimental data. The Freundlich and Langmuir model can describe the adsorption equilibrium of metal(II) on cone biomass. The biosorption constants were found from the Freundlich and Langmuir isotherms at 25 degrees C. It is found that the biosorption data of metals on cone biomass fitted both the Freundlich and Langmuir adsorption models.     

氨基磷酸螯合树脂(D418)高效去除Cu(II)的性能与机制

为阐明氨基磷酸螯合树脂(D418)在水体中高效去除Cu(II)的作用机制,通过吸附实验系统考察了pH、离子强度、接触时间、温度等因素对D418树脂去除Cu(II)的影响,并通过吸附动力学模型、等温吸附模型和位点能量分布理论分析其去除机制。研究结果表明:Cu(II)溶液初始pH=9.00时,Cu(II)最大去除率达到97.20%,且Zeta电位变化对Cu(II)去除率影响符合Boltzmann模型。离子强度在0~0.10 mol/L增加,有利于促进D418树脂去除Cu(II)。根据线性相关系数大小比较,D418树脂吸附Cu(II)过程最符合颗粒内扩散模型和Sips模型。以Sips模型计算热力学参数和吸附位点能量分布,D418树脂对Cu(II)的去除为自发进行的吸热过程。Cu(II)先占据D418树脂高能量位点,再占据低能量位点。基于XPS和FTIR数据分析,D418树脂去除Cu(II)的机制主要是静电吸引、化学沉淀和内层络合作用。      

Adsorption of ionizable organic contaminants on multi-walled carbon nanotubes with different oxygen contents

Multi-walled carbon nanotubes (MWNTs), which are considered to be promising candidates for the adsorption of toxic organics, are released into aqueous environment with their increasing production and application. In this study, the adsorption behaviors of five structurally related ionizable organic contaminants namely perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorooctanesulfonamide (PFOSA), 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-n-nonylphenol (4-NP) onto MWNTs with different oxygen contents (3.84-22.85%) were investigated. The adsorption kinetics was investigated and simulated with pseudo-second-order model. The adsorption isotherms were found to be fitted with Freundlich model and influenced by both the properties of organic chemicals and the oxygen contents of MWNTs. As adsorption capacity decreases dramatically with the increasing of oxygen contents, the MWNTs with the lowest oxygen contents possess the highest adsorption capacity among four MWNTs. For the MWNTs with the oxygen contents of 3.84%, the adsorption affinity related with hydrophobic interaction and π-electron polarizability decreased in the order of 4-NP>PFOSA>PFOS>2,4-D>PFOA. Furthermore, the adsorption characters of five contaminants were affected by solution pH and solute pK(a) considering electrostatic repulse force and hydrogen bonding, which showed the adsorption of MWNTs with lower oxygen content is much sensitive to solution chemistry.     

Adsorption characteristics of Cu(II) and Pb(II) onto expanded perlite from aqueous solution

The adsorption characteristics of Cu(II) and Pb(II) onto expanded perlite (EP) from aqueous solution were investigated with respect to the changes in pH of solution, adsorbent dosage, contact time and temperature of solution. For the adsorption of both metal ions, the Langmuir isotherm model fitted to equilibrium data better than the Freundlich isotherm model. Using the Langmuir model equation, the monolayer adsorption capacity of EP was found to be 8.62 and 13.39 mg/g for Cu(II) and Pb(II) ions, respectively. Dubinin-Radushkevich (D-R) isotherm model was also applied to the equilibrium data and the mean free energies of adsorption were found as 10.82 kJ/mol for Cu(II) and 9.12 kJ/mol for Pb(II) indicating that the adsorption of both metal ions onto EP was taken place by chemical ion-exchange. Thermodynamic functions, the change of free energy (DeltaG degrees ), enthalpy (DeltaH degrees ) and entropy (DeltaS degrees ) of adsorption were also calculated for each metal ions. These parameters showed that the adsorption of Cu(II) and Pb(II) ions onto EP was feasible, spontaneous and exothermic at 20-50 degrees C. Experimental data were also evaluated in terms of kinetic characteristics of adsorption and it was found that adsorption process for both metal ions followed well pseudo-second-order kinetics.     

Removal of heavy metal ions by iron oxide coated sewage sludge

The municipal sewage sludge was modified with iron oxide employed in metal ions removal. The surface modification method was proposed and the effect of parameters in the preparation was studied. The iron oxide coated sludge had higher surface area, pore volume and iron content, compared to uncoated sludge. The suitable conditions for removal of Cu(II), Cd(II), Ni(II) and Pb(II) ions from solutions were investigated using batch method. The suitable pH value in the extraction was 7 for adsorption of Cd(II) and Ni(II), 6 for Cu(II) and 5 for Pb(II) ions. The presence of NaNO(3), Ca(NO(3))(2) and Na(2)SO(4) in metal solution in the concentration of 0.01 M and 0.50 M could reduce the removal efficiency. The adsorption isotherms for the adsorption of the metal ions were defined by Langmuir relation. The maximum adsorption capacity of the iron oxide coated sludge for Cu(II), Cd(II), Ni(II) and Pb(II) was 17.3, 14.7, 7.8 and 42.4 mg g(-1), respectively. The adsorption kinetics for every metal ions followed pseudo-second order model. The metal removal from wastewater by iron oxide coated sludge was also demonstrated.