Comparative of the removal of Pb2+, Cd2+ and Ni2+ by nano crystallite hydroxyapatite from aqueous solutions: Adsorption isotherm study

Release of heavy metal onto the water and soil as a result of agricultural and industrial activities may pose a serious threat to the environment. In this study, the adsorption behavior of nano hydroxyapatite with respect to Pb²⁺, Cd²⁺ and Ni²⁺ has been studied in order to consider its application to purity metal finishing wastewater. The batch method has been employed, using metal concentrations in solution ranging from 100 to 400 mg/L. The uptake capacity and distribution coefficients (K_d) were determined for the adsorption system as a function of sorbate concentration. The Langmuir, Freundlich, and Dubinin–Kaganer–Radushkevich (DKR) isotherms applied for sorption studies showed that the amount of metal sorbed on nano hydroxyapatite. It was found that the adsorption phenomena depend on charge density and hydrated ion diameter. According to the equilibrium studies, the selectivity sequence can be given as Pb²⁺ > Cd²⁺ > Ni²⁺. These results show that nano hydroxyapatite holds great potential to remove cationic heavy metal species from industrial wastewater.     

Preparation of Activated Carbon From Olive Stone Waste: Optimization Study on the Removal of Cu2+, Cd2+, Ni2+, Pb2+, Fe2+, and Zn2+ from Aqueous Solution Using Response Surface Methodology

The removal efficiencies of Cu²⁺, Cd²⁺, Ni²⁺, Pb²⁺, Fe²⁺, and Zn²⁺ from aqueous solution with olive stone activated carbon (OSAC) were investigated in this paper. Central composite design method was used to optimize the preparation of OSAC by chemical activation using potassium hydroxide (KOH) as chemical agent. The optimum conditions obtained were 715°C activation temperature, 2 hours activation time, and 1.53 impregnation ratio. This resulted in removal of 99.25% Cu²⁺, 94.98% Cd²⁺, 99.08% Ni²⁺, 99.33% Pb²⁺, 99.41% Fe²⁺, and 99.17% Zn²⁺, as well as 73.94% OSAC yield. The surface characteristics of the activated carbon (AC) prepared under optimized condition were examined by pore structure analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy. The Brunauer–Emmett–Teller (BET) surface area, total pore volume, and average pore diameter of the prepared activated carbon were 886.72 m²/g, 0.507 cm³/g, and 4.22 nm, respectively. The equilibrium data of the adsorption was well fitted to the Langmuir and the highest value of adsorption capacity (Q) on the OSAC was found for Fe²⁺ (57.47 mg/g), followed by Pb²⁺ (22.37 mg/g), Cu²⁺ (17.83 mg/g), Zn²⁺ (11.14 mg/g), Ni²⁺ (8.42 mg/g), and Cd²⁺ (7.80 mg/g). The prepared OSAC can be used for efficient removal of metals from contaminated wastewater.     

Study of the selection mechanism of heavy metal (Pb2+, Cu2+, Ni2+, and Cd2+) adsorption on clinoptilolite

The study was carried out on the sorption of heavy metals (Ni2+, Cu2+, Pb2+, and Cd2+) under static conditions from single- and multicomponent aqueous solutions by raw and pretreated clinoptilolite. The sorption has an ion-exchange nature and consists of three stages, i.e., the adsorption on the surface of microcrystals, the inversion stage, and the moderate adsorption in the interior of the microcrystal. The finer clinoptilolite fractions sorb higher amounts of the metals due to relative enriching by the zeolite proper and higher cleavage. The slight difference between adsorption capacity of the clinoptilolite toward lead, copper, and cadmium from single- and multicomponent solutions may testify to individual sorption centers of the zeolite for each metal. The decrease of nickel adsorption from multicomponent solutions is probably caused by the propinquity of its sorption forms to the other metals and by competition. The maximum sorption capacity toward Cd2+ is determined as 4.22 mg/g at an initial concentration of 80 mg/L and toward Pb2+, Cu2+, and Ni2+ as 27.7, 25.76, and 13.03 mg/g at 800 mg/L. The sorption results fit well to the Langmuir and the Freundlich models. The second one is better for adsorption modeling at high metal concentrations.     

红麻纤维改性及其对Ni2+、Cu2+、Cd2+的吸附性研究

向天然纤维链上吸附性功能基制得的改性纤维不仅对金属离子的吸附容量,而且能应用于废水处理和环境保护等诸多领域。如果将大量废弃残麻接枝改性为对应吸附材料,并用于治理废水污染,则更具“双废开发,双废利用”价值。我们以信阳盛产的红麻纤维为母体,选取4-(2-吡啶偶氮)间苯二酚为功能基,在相关工作基础上,制备了4-(2-吡啶偶氮)间苯二酚基红麻纤维。同时,测试红麻纤维对Ni^2 、Cu^2 、Cd^2 的吸附性能,探讨了吸附温度、时间及介质酸度等因素对吸附的影响。     

The starch modified montmorillonite for the removal of Pb(II), Cd(II) and Ni(II) ions from aqueous solutions

In the present study, we attempted to synthesize a novel sorbent from the starch modified montmorillonite for the removal of Pb(II), Cd(II), and Ni(II) ions from aqueous solutions. Structure and properties of the adsorbent were characterized by Fourier-transformed infrared(FT-IR) spectroscopy, X-ray diffraction (XRD), and Field emission scanning electron microscopic (FE-SEM) techniques. Batch experiments were confirmed through the effect of different conditions including pH, contact time, initial metal concentration and adsorbent dose. Specifically, the optimum value of adsorbent dose was achieved as 20 g/l for the removal of almost metal ions. The adsorption data was fitted with the optimum pH value as 5 for all experiments. The contact time at which the uptake of maximum metal adsorption was observed within 45 min for Pb(II), 90 min for Cd(II), and 60 min for Ni(II). In addition, it was revealed in our study that the equilibrium data obeyed the Langmuir model, and the adsorption kinetic followed a pseudo second-order rate model. Obtained results were noticeable for a modified phyllosilicate adsorbent, and with such a simple and low-cost modification for montmorillonite, the potential of this material as an economical and effective adsorbent for the removal of metal ions from aqueous solution was considerably elevated.     

Remove of Heavy Metals(Cu2+, Pb2+, Zn2+ and Cd2+) in Water Through Modified Diatomite

At present, heavy metal pollution has become a major environmental problem, influencing the survival of human and other creatures. Developing heavy metal ion adsorbents, which are environment friendly, of low cost and good performance is one of the effective means to solve heavy metal pollution. Rich low-grade diatomite mineral, as raw material, was modified with calcium carbonate to improve the adsorption properties of diatomite for heavy metal ions. The effects of dosage(m), pH, adsorbing time(t), temperature(T) and concentration of adsorbent(c) on the removal rate of heavy metal ions(Cu²⁺, Pb²⁺, Zn²⁺ and Cd²⁺) were studied. The results show that under the suitable conditions, T=15 ℃, c=1.5 mmol/L, m=10 g/L, t=60 min, in a weak acid environment, the removal effect of the four kinds of metal ions by modified diatomite is the best.     

绿茶对水溶液中Pb2+和Cd2+吸附性能初步研究

研究了绿茶对溶液中Pb2 和Cd2 离子的吸附和解吸性质。考察了pH、温度、吸附时间对绿茶吸附性能的影响,得到吸附动力学曲线和吸附等温线。结果表明,茶叶在pH为4~6的弱酸性范围内对两种金属离子的吸附效果最佳,在30℃时,茶叶对Pb2 和Cd2 的饱和吸附量分别为46.66 mg/g和33.29mg/g,吸附符合Langmuir吸附等温方程,并对吸附机理进行了初步的探讨。对解吸条件研究发现,用0.1 mol/L HCl和EDTA作为解吸剂,对Pb2 和Cd2 的解吸效果较好,解吸率达80%以上,可有效回收重金属Pb2 和Cd2 。     

Heavy metal adsorption ability of a new composite material based on starch strengthened with chemically modified cellulose

Adsorption of heavy metals (Pb, Zn, and Cu) on a new bioadsorbent based on starch reinforced with modified cellulose with toluene‐diisocyanate has been studied using batch‐adsorption technology. The study was carried out in order to find if this bio material, designed for seedling pots manufacture, is able to act like a barrier between soil pollutants and plants. The influence of contact time, pH, adsorbent dose, and salt concentrations was also evaluated. The obtained data were examined using the Langmuir and Freundlich adsorption models. Optimal results were obtained at pH 5.0, temperature of 25°C, contact time of 120 minutes, and an adsorbent dose of 4 mg/mL. Experimental data along with computed Langmuir parameters show that the adsorption process is favorable, and the maximum adsorption capacity of the adsorbent for lead, zinc, and copper was 66.66, 58.82, and 47.61 mg/g, respectively.     

Thermodynamics of Pb2+ and Ni2+ adsorption onto natural bentonite from aqueous solutions

Removal of Pb2+ and Ni2+ from aqueous solutions by sorption onto natural bentonite was investigated. Experiments were carried out as a function of particle size, the amount of bentonite, pH, concentration of metals, contact time, and temperature. The adsorption patterns of metal ions onto followed the Langmuir, Freundlich, and Dubinin-Radushkevich isotherms. This included adsorption isotherms of single-metal solutions at 303 K by batch experiments. The thermodynamic parameters (DeltaH,DeltaS,DeltaG) for Pb2+ and Ni2+ sorption onto bentonite were also determined from the temperature dependence. The adsorptions were endothermic reactions. The results suggested that natural bentonite is suitable as a sorbent material for recovery and adsorption of metal ions from aqueous solutions.     

介孔分子筛表面功能膜的制备及对水体中铅汞镉的去除作用

表面改性;功能膜材料;重金属;吸附;介孔分子筛表面功能膜的制备及对水体中铅汞镉的去除作用     

Chemically modified kapok fiber for fast adsorption of Pb2+, Cd2+, Cu2+ from aqueous solution

Kapok fiber, a natural hollow fiber with thin shell and large cavity, has rarely been used as adsorbent for heavy metal ions. In this paper, kapok fibers were modified with diethylenetriamine pentaacetic acid (DTPA) after hydrophilicity treatment. The adsorption behavior of the resultant kapok-DTPA influenced by pH, adsorption time and initial concentration of metal ion was investigated. The results demonstrate that adsorption equilibrium was reached within 2 min for Pb²⁺ and Cd²⁺. Adsorption kinetics showed that the adsorption rate was well fitted by pseudo-second-order rate model. The adsorption isotherms were studied, and the best fit was obtained in the Langmuir model. The maximum adsorption capacities of kapok-DTPA were 310.6 mg g^?1 for Pb²⁺, 163.7 mg g^?1 for Cd²⁺, 101.0 mg g^?1 for Cu²⁺, respectively. After eight desorption and re-adsorption loops, the lost adsorption capacities for Pb²⁺ and Cu²⁺ were less than 10 %. Because of the large specific area derived from the hollow fiber structure, kapok-DTPA exhibited much better adsorption capacity compared with many other reported adsorbents based on natural materials.     

Removal of Pb2+ and Cd2+ ions from aqueous solutions using guanidine modified hydrogels

In this study, experimental measurements have been made on the batch adsorption of cadmium and lead ions from aqueous solutions using poly(guanidine modified 2‐acrylamido‐2‐methylpropan sulfonic acid/acrylic acid/N‐vinylpyrrolidone/2‐Hydroxyethyl methacrylate), P(AMPSG/AAc/NVP/HEMA) hydrogels. The guanidyl end group bearing AMPSG monomer was synthesized from the reaction of AMPS and guanidine. The hydrogels were prepared by UV‐curing technique. The morphology of the dry H10‐hydrogel sample was examined by SEM. The influence of the uptake conditions, such as pH, functional monomer per cent, contact time, initial feed concentration, and foreign metal ions on the metal ion binding capacity of hydrogel, was also tested. The selectivity of the hydrogel toward the different metal ions tested was Hg(II) > Pb(II) > Au(III) > Cd(II). The adsorption isotherm models were applied to the experimental data, and it was seen that the Langmuir isotherm model was the best fit for the adsorption of Cd(II) and Pb(II) ions on P(AMPSG/AAc/NVP/HEMA) hydrogel. It was found that adsorbed lead and cadmium ions on P(AMPSG/AAc/NVP/HEMA) hydrogel can be effectively desorbed by acid leaching and the regenerated P(AMPSG/AAc/NVP/HEMA) hydrogel can be reused almost five times less without any loss of adsorption capacity. Copyright © 2009 John Wiley & Sons, Ltd.     

Removal of Cd(II), Cu(II), and Pb(II) by adsorption onto natural clay: a kinetic and thermodynamic study

In this work, we study the elimination of three bivalent metal ions (Cd²⁺, Cu²⁺, and Pb²⁺) by adsorption onto natural illitic clay (AM) collected from Marrakech region in Morocco. The characterization of the adsorbent was carried out by X-ray fluorescence, Fourier transform infrared spectroscopy and X-ray diffraction. The influence of physicochemical parameters on the clay adsorption capacity for ions Cd²⁺, Cu²⁺, and Pb²⁺, namely the adsorbent dose, the contact time, the initial pH imposed on the aqueous solution, the initial concentration of the metal solution and the temperature, was studied. The adsorption process is evaluated by different kinetic models such as the pseudo-first-order, pseudo-second-order, and Elovich. The adsorption mechanism was determined by the use of adsorption isotherms such as Langmuir, Freundlich, and Temkin models. Experiments have shown that heavy metals adsorption kinetics onto clay follows the same order, the pseudo-second order. The isotherms of adsorption of metal cations by AM clay are satisfactorily described by the Langmuir model and the maximum adsorption capacities obtained from the natural clay, using the Langmuir isotherm model equation, are 5.25, 13.41, and 15.90 mg/g, respectively for Cd(II), Cu(II), and Pb(II) ions. Adsorption of heavy metals on clay is a spontaneous and endothermic process characterized by a disorder of the medium. The values of ΔH are greater than 40 kJ/mol, which means that the interactions between clay and heavy metals are chemical in nature.     

Interaction Structure and Affinity of Zwitterionic Amino Acids with Important Metal Cations (Cd2+, Cu2+, Fe3+, Hg2+, Mn2+, Ni2+ and Zn2+) in Aqueous Solution: A Theoretical Study

Heavy metals are non-biodegradable and carcinogenic pollutants with great bio-accumulation potential. Their ubiquitous occurrence in water and soils has caused serious environmental concerns. Effective strategies that can eliminate the heavy metal pollution are urgently needed. Here the adsorption potential of seven heavy metal cations (Cd²⁺, Cu²⁺, Fe³⁺, Hg²⁺, Mn²⁺, Ni²⁺ and Zn²⁺) with 20 amino acids was systematically investigated with Density Functional Theory method. The binding energies calculated at B3LYP-D3/def2TZVP level showed that the contribution order of amino acid side chains to the binding affinity was carboxyl > benzene ring > hydroxyl > sulfhydryl > amino group. The affinity order was inversely proportional to the radius and charge transfer of heavy metal cations, approximately following the order of: Ni²⁺ > Fe³⁺ > Cu²⁺ > Hg²⁺ > Zn²⁺ > Cd²⁺ > Mn²⁺. Compared to the gas-phase in other researches, the water environment has a significant influence on structures and binding energies of the heavy metal and amino acid binary complexes. Collectively, the present results will provide a basis for the design of a chelating agent (e.g., adding carboxyl or a benzene ring) to effectively remove heavy metals from the environment.     

Competitive adsorption of Pb2+, Cu2+, and Cd2+ ions on microporous titanosilicate ETS-10

In the present study, the competitive adsorption characteristics of binary and ternary heavy metal ions Pb2+, Cu2+, and Cd2+ on microporous titanosilicate ETS-10 were investigated in batch systems. Pure microporous titanosilicate ETS-10 was synthesized with P25 as the Ti source and characterized by the techniques of X-ray diffraction (XRD), field emission-scanning electron microscope (FESEM), nitrogen adsorption, and zeta-potential. Equilibrium and kinetic adsorption data showed that ETS-10 displays a high selectivity toward one metal in a two-component or a three-component system with an affinity order of Pb2+ > Cd2+ > Cu2+. The equilibrium behaviors of heavy metals species with stronger affinity toward ETS-10 can be described by the Langmuir equation while the adsorption kinetics of the metals can be well fitted to a pseudo-second-order (PSO) model.     

Synthesis of Nanosilica for the Removal of Multicomponent Cd2+ and Cu2+ from Synthetic Water: An Experimental and Theoretical Study

Copper and cadmium ions are among the top 120 hazardous chemicals listed by the Agency for Toxic Substances and Disease Registry (ATSDR) that can bind to organic and inorganic chemicals. Silica is one of the most abundant oxides that can limit the transport of these chemicals into water resources. Limited work has focused on assessing the applicability of nanosilica for the removal of multicomponent metal ions and studying their interaction on the surface of this adsorbent. Therefore, this study focuses on utilizing a nanosilica for the adsorption of Cd²⁺ and Cu²⁺ from water. Experimental work on the single- and multi-component adsorption of these ions was conducted and supported with theoretical interpretations. The nanosilica was characterized by its surface area, morphology, crystallinity, and functional groups. The BET surface area was 307.64 m²/g with a total pore volume of 4.95×10−3 cm³/g. The SEM showed an irregular amorphous shape with slits and cavities. Several Si–O–Si and hydroxyl groups were noticed on the surface of the silica. The single isotherm experiment showed that Cd²⁺ has a higher uptake (72.13 mg/g) than Cu²⁺ (29.28 mg/g). The multicomponent adsorption equilibrium shows an affinity for Cd²⁺ on the surface. This affinity decreases with increasing Cu²⁺ equilibrium concentration due to the higher isosteric heat from the interaction between Cd and the surface. The experimental data were modeled using isotherms for the single adsorption, with the Freundlich and the non-modified competitive Langmuir models showing the best fit. The molecular dynamics simulations support the experimental data where Cd²⁺ shows a multilayer surface coverage. This study provides insight into utilizing nanosilica for removing heavy metals from water.     

7种胺基键合硅胶的制备及其对重金属Pb2+的吸附

制备了氨丙基键合硅胶（SiO₂-N）、乙二胺-N-丙基键合硅胶（SiO₂-2N）、二乙烯三胺基键合硅胶（SiO₂-3N）、三乙烯四胺基键合硅胶（SiO₂-4N）、四乙烯五胺基键合硅胶（SiO₂-5N）、五乙烯六胺基键合硅胶（SiO₂-6N）和聚乙烯亚胺基键合硅胶（SiO₂-nN）,一步法制备的SiO₂-N和SiO₂-2N的胺基键合密度高达2.07 mmol/g和1.71mmol/g,两步法制备的SiO₂-nN的胺基键合密度为0.02mmol/g,其余胺基键合硅胶中胺基密度约为0.50mmol/g。这7种胺基键合硅胶被用于水溶液中常见重金属离子Pb²⁺的吸附研究。结果表明,在30℃条件下,分别加入10 mL 400 mg/L的Pb²⁺溶液（pH 5）和20 mg胺基键合硅胶进行吸附,10 h后,Pb²⁺吸附量达到最大,吸附过程符合Freundlich等温方程。SiO₂-N、SiO₂-2N、SiO₂-3N、SiO₂-4N、SiO₂-5N、SiO₂-6N和SiO₂-nN对Pb²⁺的吸附量依次为131.28、138.98、85.37、75.22、61.87、79.12和114.06 mg/g,这些胺基键合硅胶在吸附Pb²⁺方面均非常具有潜力。     

Simultaneous determination of Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ by using second-derivative spectrophotometry method

A new method of simultaneous determination of Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ is proposed here by using the second-derivative spectrophotometry method. In pH=10.35 Borax-NaOH buffer, using meso-tetra (3-methoxyl-4-hydroxylphenyl) porphyrin ([T-(3-MO-4-HP)P]) as chromomeric reagent, micelle solution was formed after Tween-80 surfactant was added into the solution containing Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ ions. The original absorption spectrum of the above complexes was obtained after heating in the boiling water for 25 min. The second-derivative absorption peaks of five metal-porphyrin complexes can be separated from the original absorption spectrum by using chemometric tool. In this way, Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ ions can be determined simultaneously. Under the optimal conditions, the linear ranges of the calibration curve were 0-0.60, 0-0.60, 0-0.40, 0-0.80 and 0-0.48 μg mL(-1) for Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+, respectively. The molar absorptivity of these color systems were 1.38×10(5), 1.01×10(5), 3.24×10(5), 1.07×10(5) and 1.29×10(5)Lmol(-1)cm(-1). The method developed in this paper has advantages in selectivity, sensitivity, operation and can effectively resolve spectra overlapping problem. This method has been applied to determine the real samples with satisfactory results.     

Modeling of ionic equilibria of trace metals (Cu2+, Zn2+, Cd2+) in concentrated aqueous electrolyte solutions at 25 degrees C

This work presents a model of activity coefficients and a database for ionic equilibria of Cu2+, Zn2+, and Cd2+ in (H+, Na+, K+, Mg2+, Ca2+)(OH-, Cl-, NO-3, ClO-4, HSO-4, SO2-(4), HCO-3, CO(2-)3) aqueous media valid up to 6-12 m ionic strength. The activity coefficient of a dissolved species is represented by empirical equation [Formula: see text] , where Agamma is Debye-Hückel constant (1.17 at 25 degrees C), gammai and zi are activity coefficient and charge of a dissolved species i, I is molal ionic strength, bij is model parameter, and mj is molal concentration of dissolved species. The model is applicable to the modeling of ionic equilibria, as well as to simulation of solubility of salts in mixed electrolyte solutions.     

Adsorption of Pb2+, Zn2+, and Cd2+ from waters by amorphous titanium phosphate

In the current study, amorphous titanium phosphate (TiP) was prepared as an adsorbent for heavy metals from waters. Uptake of Pb(2+), Zn(2+), and Cd(2+) onto TiP was assayed by batch tests; a polystyrene-sulfonic acid exchanger D-001 was selected for comparison and Ca(2+) was chosen as a competing cation due to its ubiquitous occurrence in waters. The pH-titration curve of TiP implied that uptake of heavy metals onto TiP is essentially an ion-exchange process. Compared to D-001, TiP exhibits more preferable adsorption toward Pb(2+) over Zn(2+) and Cd(2+) even in the presence of Ca(2+) at different levels. FT-IR analysis of the TiP samples laden with heavy metals indicated that the uptake of Zn(2+) and Cd(2+) ions onto TiP is mainly driven by electrostatic interaction, while that of Pb(2+) ions is possibly dependent upon inner-sphere complex formation, except for the electrostatic interaction. Moreover, uptake of heavy metals onto TiP approaches equilibrium quickly and the exhausted TiP particles could be readily regenerated by HCl solution.