Chitosan N-benzyl sulfonate derivatives as sorbents for removal of metal ions in an acidic medium

We synthesized chitosan-based sorbents for the uptake of metal cations in acidic solutions. Chitosan was reacted with 2-formylbenzene sodium sulfonate and 4-formyl-1,3-benzene sodium disulfonate in the presence of NaCNBH₃ to yield N-benzyl mono- and disulfonate derivatives of chitosan. IR and NMR spectra confirmed the presence of benzyl sulfonate groups. The degrees of substitution of the monosulfonate chitosan derivatives were in the range of 80%, while those of disulfonate derivatives were about 50%. These sulfonate derivatives of chitosan were tested on the sorption of heavy metals Cd²⁺, Zn²⁺, Ni²⁺, Pb²⁺, Cu²⁺, Fe³⁺, and Cr³⁺. The sorption capacities for disulfonate compounds were better than for monosulfonate compounds. This phenomenon was attributed to the amphoteric character of the monosulfonate derivatives. To improve the capacity of adsorption of monosulfonate compounds, the amino groups of these compounds were protected by the benzyloxycarbonyl groups. The protection of amino groups of disulfonate derivatives by benzyloxycarbonyl also improved their sorption capacity. The resulting protected polymers were tested for sorption of heavy metals. Both protected polymers were more efficient than are the parent nonprotected polymers. The synthesized sulfonate derivatives of chitosan are especially adapted to the sorption of heavy metals from the acidic industrial effluents. © 1996 John Wiley & Sons, Inc.     

SORPTION PROCESSES OF NATURAL IRANIAN BENTONITE EXCHANGED WITH CD2+, CU2+, NI2+, AND PB2+ CATIONS

Experimental studies on the retention of cadmium (Cd²⁺), copper (Cu²⁺), nickel (Ni²⁺), and lead (Pb²⁺) by bentonite samples from Iran were conducted using single- and multiple-component solutions. Based on the sorption capacity of bentonite the following order was obtained for single- and multiple-component solutions: Pb²⁺ > Cd²⁺ > Ni²⁺ > Cu²⁺. The maximum adsorption capacities of bentonite with metals in single- and multiple-component solutions were 29.5%, 22.5%, 19.2%, and 17.1% and 13.5%, 13.4%, 12.1%, and 9.1% for Pb²⁺, Cd²⁺, Ni²⁺, and Cu²⁺, respectively. Desorption isotherms of Cd²⁺, Cu²⁺, Ni²⁺, and Pb²⁺ deviated significantly from the sorption isotherms, thereby indicating irreversible or very slowly reversible sorption. Finally, soil solution saturation indices and metal speciation were assessed using the Visual MINTEQ 2.6 program and the probability of mineral precipitation was supported by scanning electron microscopy.     

Magnesium ferrite nanoparticles as a magnetic sorbent for the removal of Mn2+, Co2+, Ni2+ and Cu2+ from aqueous solution

The aim of this research was to prepare magnesium ferrite (MgFe₂O₄) magnetic nanoparticles and to investigate their sorption characteristics towards Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ ions in aqueous solution. MgFe₂O₄ was synthesized by glycine-nitrate combustion method and was characterized by low crystallinity with crystallite size of 8.2?nm, particle aggregates of 13–25?nm, BET surface area of 14?m²/g and pore size of 8.0?nm. Sorption properties of MgFe₂O₄ towards Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ ions were studied using one-component model solutions and found to be dependent on metal ions concentration, contact time, pH and conditions of regeneration experiment. The highest sorption capacity of MgFe₂O₄ was detected towards Co²⁺ (2.30?mmol?g¹) and Mn²⁺ (1.56?mmol?g^?1) and the lowest towards Ni²⁺ (0.89?mmol?g^?1) and Cu²⁺ (0.46?mmol?g^?1). It was observed that sorption equilibrium occurs very quickly within 20–60?min. The pH_zpc of sorbent was calculated to be 6.58. At studied pH interval (3.0–7.0) the sorption capacity of MgFe₂O₄ was not significantly affected. Regeneration study showed that the metal loaded sorbent could be regenerated by aqueous solution of 10^?3 M MgCl₂ at pH 6.0 within 120?min of contact time. Regeneration test suggested that MgFe₂O₄ magnetic sorbent can be efficiently used at least for four adsorption-desorption cycles. The high sorption properties and kinetics of toxic metal ion sorption indicates good prospects of developed sorbent in practice for wastewater treatment.     

Carbon-encapsulated magnetic nanoparticles as separable and mobile sorbents of heavy metal ions from aqueous solutions

Carbon-encapsulated magnetic nanoparticles (CEMNPs) are studied as mobile sorbents for removal of heavy metal ions (Cu²⁺, Co²⁺, Cd²⁺) from aqueous solutions. The ion uptakes achieve 95% for cadmium and copper. CEMNPs-based sorbents also have excellent adsorption capacities (between 1.23 and 3.21 mg/g), which are considerably higher than the capacities of activated carbons (between 0.37 and 0.39 mg/g).     

Chelating polymer bearing triazolylazophenol moiety as the functional group

The chelating polymer-bearing triazolylazophenol moiety as the functional group was synthesized, its metal adsorption properties for 6 divalent heavy metal ions; Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, and Pb²⁺ were investigated. The capacity of the polymer for Cu²⁺ achieved 8.7 mEq/g in pH 5.3 solution. The polymer showed remarkable color changes from orange to red violet or blue violet with its chelations to the heavy metal ions. The metal adsorption rates of the polymer were rapid in performing complete capacity saturation of heavy metal ions in about 30 min. The capacities varied little the presence of alkali or alkaline earth metal ions in solutions. The perfect elimination of metals from the polymer–M²⁺ chelates were performed with mineral acid solutions. The metal ions; Cu²⁺ and Ni²⁺ in plating-process solutions were effectively removed by the chelating polymer, and the polymer can be practically used for the removal of these ions from waste water.     

REMOVAL OF Cd2+, Cu2+, AND Ni2+ METALS FROM SIMULATED WASTEWATER IN SINGLE AND COMPETITIVE SYSTEMS USING LOCAL IRAQI PHOSPHATE ROCKS

The equilibrium uptake of cadmium (Cd²⁺), copper (Cu²⁺), and nickel (Ni²⁺) ions, both singly and in combination, by local Iraqi phosphate rocks (PR) was studied in a batch system. The phosphate rock was characterized using BET, FT-IR, XRD, and SEM techniques. Adsorption isotherms were developed for both the single and ternary-component systems and expressed by the mono- and multicomponent Langmuir, Freundlich, Redlich-Peterson, and Dubinin-Radushkevich adsorption models; model parameters were estimated by the nonlinear regression method using STATISTICA version 6 software. To understand the action of metals uptake, factors influencing the adsorption of the heavy metals including pH, initial metal ion concentration, weight of the adsorbent, mixing speed, contact time, and temperature were investigated. It was found that the mono- and multicomponent adsorption equilibrium data fitted very well to the Langmuir model with high determination coefficient (R ²). The maximum loading capacities (q _max) were 70.852, 53.372, and 48.045 mg/g for Cd²⁺, Cu²⁺, and Ni²⁺ respectively. However, in the ternary system the loading capacity decreased because of competition between ions to binding sites of the adsorbent. Adsorption data were modeled using the pseudo-first- and pseudo-second-order kinetic and intraparticle diffusion models. It was seen that the pseudo- first-order kinetic equation could best describe the adsorption kinetics. Thermodynamic parameters showed that the adsorption of investigated heavy metals onto PR was endothermic and spontaneous in nature and the process is physiosorption. Fourier transform-infrared spectroscopy (FT-IR) analysis indicated that carboxylic (C?O), phosphine (p-H), and hydroxyl (–OH) groups in PR played an important role in the adsorption process. In conclusion, PR was found suitable as an abundant adsorbent for removal of the selected metal ions from aqueous solutions.     

Sorption characteristics of heavy metal ions by a natural zeolite

Zeolites have been shown to be effective adsorbents for the removal of heavy metals from aqueous solutions. A natural material from Cuba, containing zeolite, has been used for the removal of several metal ions, namely Cu²⁺, Zn²⁺, and Ni²⁺, to evaluate its potential use as a low‐cost adsorbent. Batch experiments have been conducted to evaluate the process kinetics and the removal equilibrium at different pH values, metal and zeolite concentrations. Pseudo‐second order kinetics and Freundlich equilibrium parameters have been obtained. Results suggested that this natural zeolite has a high potential for heavy metal retention. The selectivity of the studied metals was determined as Cu²⁺ ? Zn²⁺ > Ni²⁺, related to the first hydrolysis equilibrium constant. The metal removal efficacy was strongly dependent on pH, and to a lesser extent on metal/zeolite ratio. Copyright © 2005 Society of Chemical Industry     

Characterization of Adsorptive Capacity and Investigation of Mechanism of Cu2+, Ni2+ and Zn2+ Adsorption on Mango Peel Waste from Constituted Metal Solution and Genuine Electroplating Effluent

Abstract

The present study reports the potential of mango peel waste (MPW) as an adsorbent material to remove Cu²⁺, Ni²⁺, and Zn²⁺ from constituted metal solutions and genuine electroplating industry wastewater. Heavy metal ions were noted to be efficiently removed from the constituted solution with the selectivity order of Cu²⁺ > Ni²⁺ > Zn²⁺. The adsorption process was pH-dependent, while the maximum adsorption was observed to occur at pH 5 to 6. Adsorption was fast as the equilibrium was established within 60 min. Maximum adsorption of the heavy metal ions at equilibrium was 46.09, 39.75, and 28.21 mg g for Cu²⁺, Ni²⁺, and Zn²⁺, respectively. Adsorption data of all the three metals fit well the Langmuir adsorption isotherm model with 0.99 regression coefficient. Release of alkali and alkaline earth metal cations (Na⁺, K⁺, Ca²⁺, Mg²⁺) and protons H⁺ from MPW, during the uptake of Cu²⁺, Ni²⁺, and Zn²⁺, and EDX analysis of MPW, before and after the metal sorption process, revealed that ion exchange was the main mechanism of sorption. FTIR analysis showed that carboxyl and hydroxyl functional groups were involved in the sorption of Cu²⁺, Ni²⁺, and Zn²⁺. MPW was also shown to be highly effective in removing metal ions from the genuine electroplating industry effluent samples as it removed all the three metal ions to the permissible levels of discharge legislated by environment protection agencies. This study indicates that MPW has the potential to effectively remove metal ions from industrial effluents.     

Evaluation of ion exchange resins for recovery of metals from electroplating sludge

In the present study, the recovery of metal ions from industrial solid residues from a galvanoplasty industry (Rio de Janeiro, Brazil) was investigated by cationic and anionic ion exchange resins. The electroplating residues were composed of the metals Cu²⁺, Fe³⁺, Al³⁺, Ni²⁺, and Cr³⁺. The studies of sorption were conducted under batch and column conditions. Based on these studies, the sorption parameters and the breakthrough curves for both resins were determined. Studies of the sorption equilibrium and kinetics were also performed. The maximum sorption capacities q _e (mg g^?1) of the cationic resin were: Cu²⁺: 1.9, Fe³⁺: 0.6 and Al³⁺: 0.4. For the anionic resin, the maxim values of q _e were Cu²⁺: 0.4 and Fe³⁺: 0.1. The Freundlich model was more adequate to describe the ion exchange equilibrium and the sorption mechanism fit the pseudo second-order kinetic model for both resins. The breakpoint of Cu²⁺ (100 ppm) occurred after passing 1,860 and 2,220 cm³ of residue solution through 20.0 g of the resins (column with h:6.0 cm and d:4.3 cm, flow rate: 60 cm³ min^?1). The column regeneration was carried out for five sorption–desorption cycles using H₂SO₄ 2.4 mol L^?1 (cationic) and HCl 2.0 mol L^?1 (anionic).     

Removal of Cd2+, Cu2+, Ni2+, and Pb2+ ions from aqueous solutions using tururi fibers as an adsorbent

This work investigates the removal of Cd²⁺, Cu²⁺, Ni²⁺, and Pb²⁺ ions from aqueous solutions using tururi fibers as an adsorbent under both batchwise and fixed‐bed conditions. It was found that modification of the tururi fibers with sodium hydroxide increased the adsorption efficiencies of all metal ions studied. The fractional factorial design showed that pH, adsorbent mass, agitation rate, and initial metal concentration influenced each metal adsorption differently. The kinetics showed that multi‐element adsorption equilibria were reached after 15 min following pseudo‐second‐order kinetics. The Langmuir, Freundlich, and Redlich–Peterson models were used to evaluate the adsorption capacities by tururi fibers. The Langmuir model was found to be suitable for all metal ions. Breakthrough curves revealed that saturation of the bed was reached in 160.0 mL with Cd²⁺ and Cu²⁺, and 52.0 mL with Ni²⁺ and Pb²⁺. The Thomas model was applied to the experimental data of breakthrough curves and represented the data well. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40883.     

Adsorption for metal ions of chitosan coated cotton fiber

A kind of adsorbent for metal ions, cotton fiber coated by high loading of chitosan (SCCH) was prepared. Its structure was characterized by elemental analysis, scanning electronic microscopy (SEM), Fourier transform infrared spectrum (FTIR), and wide‐angle X‐ray diffraction (WAXD). The adsorption properties of SCCH for Cu²⁺, Ni²⁺, Pb²⁺, Cd²⁺, such as saturated adsorption capacities, static kinetics, and isotherm were investigated. The adsorption for Ni²⁺, Pb²⁺, and Cd²⁺ was controlled by liquid film diffusion, but by particle diffusion for Cu²⁺. The adsorption process for Cu²⁺, Ni²⁺, Cd²⁺ could be described with Langmuir or Freundlich equation, but only with Freundlich equation for Pb²⁺. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Catalytic Ozonation of m-Dinitrobenzene

The efficiency of catalytic ozonation with homogeneous (containing dissolved ions of Fe²⁺, Mn²⁺, Cu²⁺, Ni²⁺, Co²⁺, V⁵⁺, Cr³⁺, Mo⁶⁺) and heterogeneous (MnO₂, Ni₂O_3, Fe₂O₃, CuO, Al₂O₃, CoO, V₂O₅, Cr₂O₃, MoO₃, TiO₂) catalysts and non-accompanied ozonation was compared for degradation of m-dinitrobenzene (m-DNB). Several transition metals in homogeneous and heterogeneous form improved significantly the ozone performance for degradation of m-DNB. This improvement was found to be due to supplementary formation of reactive species (hydroxyl radicals) and better ozone utilization. The effects observed were found to be strongly dependent on the treatment conditions.     

Application of insoluble cellulose xanthate for the removal of heavy metals from aqueous solution

Insoluble cellulose xanthate (ICX), O-alkyl dithiocarbonate of cellulose, was synthesized and used for the removal of heavy metal ions from aqueous solutions. ICX possessed carbon disulfide (CS₂) as a functional group, which was obtained by esterification of the hydroxyl group on cellulose polymer matrix with CS₂. CS₂ could form complexes with divalent transition metal ions, and the resulting ICX-metal complex was water-insoluble and settled easily. The optimum composition for ICX synthesis was cellulose/NaOH/CS₂=1: 2: 2.3 in mole base, which showed the highest removal capacity. The selectivity and binding capacity of ICX for heavy metals were in the order of Pb²⁺> Cd²⁺> Ni²⁺ and Cd²⁺> Pb²⁺> Ni²⁺, respectively. More than 90 % of the initial amount of heavy metals was removed within 30 min. The optimum pH was neutral or slightly alkaline, and more than 40 % of initial heavy metals was removed even in the acidic range of pH 2 to 3.     

Hydrous iron oxide for removal of inorganic contaminants in simulated stormwater: A batch sorption kinetics study

Urban stormwater runoff, which consists of inorganic and organic contaminants, is a major source of pollutants to receiving waters and therefore they need to be removed. Simultaneous removal of contaminants, Cd²⁺, Cu²⁺, Ni²⁺, Zn²⁺ (heavy metal cations), and SeO₄²⁻ (oxyanion) from a simulated stormwater by a hydrous ferric oxide (HFO) was studied in batch and column sorption experiments. In the batch experiment the rate of sorption of the ions was rapid at the beginning and reached equilibrium in approximately 300 min. The amounts of ions sorbed were proportionate to the respective initial concentration of the ions added to the HFO. Cluster analysis showed that all heavy metals had similar sorption behavior, whereas Se had a distinctly different sorption process. Of the three different kinetic models tested the pseudo-first order kinetic model fitted the data the best. The column experimental results beyond 180 min were consistent with those of the batch experiment that the removal efficiencies of the ions were in proportion to the ion concentration in the feed. Below 180 min, Cu appeared to be preferentially removed than Zn.     

Biosynthesized magnetite-perovskite (XFe2O4-BiFeO3) interfaces for toxic trace metal removal from aqueous solution

X-modified magnetite (XFe₂O₄; X?=?Cr, Mn, Fe, Co or Ni) was synthesized from goethite reduction, and inserted into the Fe-vacancy of perovskite (BiFeO₃), via microbial Fe³⁺→Fe²⁺ reduction by Shewanella (e.g. Shewanella oneidensis MR-1 and Shewanella putrefaciens CN32). We demonstrated that the average adsorption intensities of nine toxic trace metals (Cr³⁺, Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, and Hg²⁺), in Freundlich mode were 8.29–10.79 multiples higher than that in Langmuir mode, being more competitive than previously reported values. The fluorescence quenching is attributed to the orbital hybridization of molecular oxygen activation and trace metal (M) ions, which weakens the X²⁺-O-Fe³⁺-O-(Fe³⁺) coupling orbital. In addition Shewanella putrefaciens CN32 creates more oxygen vacancies to modify Ni↓-Fe↓-O↑ d*-p hybridized orbitals for enhancing the local spin-orbit coupling with Cd-4d¹⁰. This design idea can be extended to other direct biosynthetic magnetite-perovskite as highly efficient toxic trace metal removal agents.     

PVA cryogel membranes as a promising tool for the retention and separation of metal ions from aqueous solutions

The sorption and transport of metal ions by poly(vinyl alcohol) hydrogel membranes (PVA HG), obtained by physical crosslinking through the freezing/thawing method, was analyzed using aqueous nitrate solutions of copper, lead, and nickel, at concentrations ranging from 1 to 100 mM, at 25°C. The sorption of heavy metal by PVA HG has been characterized by swelling and loading degrees. The effect of the heavy metals incorporation on the chemical properties of PVA HG matrices has been studied using SEM, to observe changes in the surface morphology of PVA HG membranes, and FTIR–ATR, aiming to monitor the heavy metals ions sorption into PVA hydrogel membranes. The analysis of permeation and diffusion coefficients of 100 mM aqueous solutions of Cu²⁺, Ni²⁺, and Pb²⁺ show that the diffusion process may be mainly described by hydrodynamic models; however, the transport process shows that the distribution coefficient for the different heavy metals are always higher than one, in agreement, with the sorption studies. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of Ni promoter in the oxide precursors of MoS2/MgO–Al2O3 catalysts tested in dibenzothiophene hydrodesulphurization

NiMoS catalysts supported on MgO–Al₂O₃ oxides, with 95 and 80 mol% of MgO, were synthesized by sol–gel method. In order to study the Ni promoter effect, MgO–Al₂O₃ supports were impregnated with a pH = 9 solution of Mo and Ni–Mo, respectively; the catalysts were dried (D) and calcinated (C). Catalytic tests showed a Ni promoter effect of 4.5 on the NiMoMg95Al5-D catalyst and 8.5 on the calcinated one. The latter catalyst is more active than a commercial NiMo/Al₂O₃ catalyst. On the other side, the catalyst supported on Mg80Al20 solid did not show any Ni promoter effect. Raman and UV–vis diffuse reflectance spectroscopy showed that during the impregnation step, a strong support interaction with the ion MoO₄^2? takes place on the Mo/MgO–Al₂O₃ solids. After calcination, MoO₄^2? ion remained on the catalyst surface, but increased its interaction with the support. The presence of Ni²⁺_Th, Ni²⁺_Oh and MoO₄^2? ions on dried NiMo/Mg95Al5 catalysts was confirmed, as well as the presence of Ni²⁺_Th, Ni²⁺_Oh, MoO₄^2? and Mo₇O₂₄^6? ions on the calcinated catalyst. This suggests that Ni²⁺ ion allows polymerization of MoO₄^2? to Mo₇O₂₄^6?, produced by Ni²⁺_Oh–MoO₄^2? and Ni²⁺_Oh–Mo₇O₂₄^6? close interactions. The NiMo/Mg80Al20 solids also showed MoO₃ species and a high Ni²⁺_Th concentration. Thus, the Ni promoter effect and therefore, catalytic activity decreased, due to the formation of Ni²⁺_Th–MgO and Ni²⁺_Th–Al₂O₃ spinels.     

Sorption Studies of Terpolymers Based on p-Nitrophenol,Triethylenetetramine, and Formaldehyde

Terpolymer resins have been synthesized by condensation of p-nitrophenol, triethylenetetramine, and formaldehyde in the presence of 2 M NaOH as a catalyst with different molar proportions of monomers. Newly synthesized terpolymers were proved to be selective chelation ion exchangers for metal ions like Fe³⁺, Cu²⁺, Ni²⁺, Co²⁺, Zn²⁺, Cd²⁺, Hg²⁺, and Pb²⁺. A batch equilibrium study was carried out over a wide pH range, shaking time, and in media of various ionic strengths of different electrolytes and shows higher selectivity for Hg²⁺, Cd²⁺, and Pb²⁺. Distribution ratios of metal ions were found to be increased by increasing pH of solutions; hence the resins can be used to recover certain metals from waste solutions and removal of iron from boiler water.     

π‐Complexation Studied by Fluorescence Technique: Application in Desulfurization of Petroleum Product using Magnetic π‐Complexation Sorbents

Abstract

Magnetic π‐complexation sorbents were studied for petroleum product desulfurization by fluorescent technique. The ability of metal cation to form π‐complexation decreases in the order following: Cu⁺>Ni²⁺>Co²⁺>Al³⁺. The order is consistent with that of desulfurization performance of their corresponding magnetic sorbents (γ‐Al₂O₃‐Cu(I)>γ‐Al₂O₃‐Ni(II)>γ‐Al₂O₃‐Co(II)>γ‐Al₂O₃). Both π‐complexation strength and desulfurization performance of the sorbents increase with temperature. The adsorptive performances of magnetic γ‐Al₂O₃‐Cu(I) sorbent to different compounds have the following orders: DBT>fluorene, and pyrene>naphthalene>benzene, respectively. In this study, dibenzothiophene (DBT) was used as a model sulphur‐containing compound for desulfurization. The maximal adsorption amount of magnetic γ‐Al₂O₃‐Cu(I), was 0.362 mmol DBT g^?1.