Adsorption Of Heavy Metal Cations Research Articles

Synthesis of a three-dimensional reduced graphene oxide aerogel decorated with (Fe3O4@SiO2–NH2)–COC2H4COOH for adsorption of heavy metal cations

Hereunder, a new method for the synthesis of a three-dimensional (3D) reduced graphene oxide (r-GO) nanohybrid is presented by the use of a synthetic novel crosslinker ((Fe3O4@SiO2–NH2)–COC2H4COOH) designed for multifunctional purposes. This crosslinker not only provide a three-dimensional structure for the adsorbent (increasing adsorption capacity), but also it enables the magnetically separation of the 3D r-GO nanohybrid. According to high-resolution transmission electron microscopy (HRTEM), the r-GO sheets were well decorated with nearly spherical (Fe3O4@SiO2–NH2)–COC2H4COOH nanoparticles with an average size of 60 nm. More importantly, the X-ray photoelectron spectroscopy (XPS) showed that the 3D r-GO nanohybrid contains several oxygenous and nitrogenous functional groups that makes it an ideal heavy metallic cations adsorbent. In addition, the synthesized 3D r-GO nanohybrid showed a maximum adsorption capacity of ∼455, 448 and 232 mg/g for lead, cadmium, and copper, respectively; besides, the exothermic adsorption of these cations followed a pseudo-second-order model. It was also found that an effective metal desorption step can be achieved by using a mixture of nitric acid and acetonitrile. The adsorption percentage of the 3D r-GO nanohybrid remained unchanged after five cycles of adsorption–desorption step. At last, the experimentally observed adsorption/desorption behaviors were justified using the density functional theory (DFT).

High‐Content Hydroxyapatite Carbon Composites for the Electrochemical Detection of Heavy Metal Cations in Water

AbstractThe great performance of nanostructured hydroxyapatite (Hap) in adsorbing heavy metal cations with the good electrical conductivity of high‐surface carbon materials was here combined for the crafting of high‐content hydroxyapatite electrodes (Hap 84–96 wt.%) endowed with the synergistic capability of detection and adsorption of heavy metal cations by water solutions. To improve the sustainability of the sensor, a mesoporous carbon (derivable by bio‐waste) was selected as scaffold for depositing Hap by simply co‐precipitation. The composite with 92 wt.% of Hap, which exhibited ca. 1 : 1 ratio between the exposed area of Hap and carbon (by Brunauer‐Emmett‐Teller method), invariably showed an average stripping oxidation peak intensity of ca. 250 μA cm−2 and 150 μA cm−2 for a 50 μM Pb2+ and Cu2+ solution, respectively. Control experiments showed that the above sensor outperformed the sensibility of two low‐content Hap electrodes (4 and 8 wt.%), representative of the best performing Hap‐carbon composites available in literature.

Effect of microplastics on the binding properties of Pb(ii) onto dissolved organic matter: insights from fluorescence spectra and FTIR combined with two-dimensional correlation spectroscopy.

Heavy metal cations are a typical type of inorganic pollutant that has persistent distribution characteristics in aquatic environments and are easily adsorbed on carriers, posing serious threats to ecological safety and human health. Some studies have shown that the coexistence of dissolved organic matter (DOM) and microplastics (MPs) promotes the adsorption of heavy metal cations, but the mechanism of promoting the adsorption process has not been thoroughly studied. In this study, the effect of polystyrene microplastics (PSMPs) on the binding properties of Pb2+ onto humic acid (HA) in aquatic environments was investigated by spectral analysis and two-dimensional correlation (2D-COS) analysis. When PSMPs co-existed with HA, the adsorption capacity of Pb2+ increased. On the one hand, Pb2+ is directly adsorbed on HA through the mechanism of complexation reaction, ion exchange and electrostatic interaction. On the other hand, Pb2+ is first adsorbed on PSMPs by electrostatic action and indirectly adsorbed on HA in the form of PSMPs-Pb2+ owing to the interaction between HA and PSMPs, which increases the adsorption amount of Pb2+ on HA. This study is significant for studying the migration and regression of heavy metal cation contaminants when PSMPs co-exist with DOM in an aqueous environment.

Oxidized Biomass and Its Usage as Adsorbent for Removal of Heavy Metal Ions from Aqueous Solutions.

Nowadays, very coarse wool fibers are considered waste biomass and are discarded at random or burned. Therefore, it is of actual interest to valorize coarse wool fibers as utile products. In this sense, we report herein an environmentally-friendly process for the preparation of a new material based on oxidized wool fibers and designed for efficient adsorption of heavy metals from wastewater. The morphology and the structure of the obtained product were characterized by scanning electron microscopy (SEM) coupled with an X-ray energy-dispersive module (EDX) and by Fourier-transform infrared spectroscopy (FTIR). Likewise, the performances of the oxidized wool fibers for the adsorption of heavy metal cations (Cu2+, Cd2+, Pb2+) from aqueous solutions were tested. The adsorption kinetics data were analyzed by applying the pseudo-first-order (PFO) and pseudo-second-order (PSO) kinetic models. The equilibrium of the adsorption process was investigated by using the Freundlich and Langmuir isotherm models. According to the Langmuir isotherms registered at 300 K, the maximum adsorption capacities of the oxidized wool were found to increase from Cu2+ (9.41 mg/g) and Cd2+ (10.42 mg/g) to Pb2+ (30.71 mg/g). Consequently, the removal efficiency of metal ions was found to vary in the range of 96.8–99.7%. The thermodynamic parameters (e.g., enthalpy, entropy, and Gibbs free energy) were calculated and discussed.

Caracterización de algas recolectadas en la Baixada Santista litoral y sus posibles usos como biosorbentes de cationes de metales pesados

This work aims to characterize biosorbent materials based on seaweed present on the littoral of Baixada Santista (São Paulo state, Brazil), and test their adsorption properties to remove heavy metal cations (Co+2, Pb+2, and Cd+2) in water, aiming its future application in situ remediations degraded ecosystems. Three types of natural seaweed were studied: Sargassum sp, Ulva lactuca, and Padina sp. These biosorbents were collected, pretreated, and modified by two chemical treatments: 1) Protonation with HCl, and, 2) Oxidation with KMnO4. The preliminary results showed that the Ulva lactuca is promising for the adsorption of heavy metal cations in water, which is also very attractive due to its great availability in the ecosystem, and it is renewable. The biosorbents (natural and modified by chemical treatments) were characterized by Fourier Transform Infrared Spectroscopy (FTIR), and by Scanning Electron Microscopy (SEM). The best heavy metal removal values for the best biosorbent Ulva lactuca (after chemical treatment) were:  65 mg.g-1  for Co (II), 71 mg.g-1 for Cd(II), and 78 mg.g-1 for Pb(II).

Sodium-modified mesoporous TiO2: Sol-gel synthesis, characterization and adsorption activity toward heavy metal cations

Experimental samples of mesoporous TiO2 with protonated and sodium-modified surfaces were obtained by sol-gel method. XRD, IR, X-ray fluorescence, and energy dispersive spectroscopy were used to characterize their crystalline structure, morphology and surface functional groups. The surface area of, and pore size distribution in the obtained samples were measured by the nitrogen adsorption/desorption isotherm, and calculated using the BET and non-local DFT theories. The adsorption of the Zn(II), Sr(II) and Ba(II) cations by the protonated and sodium-modified TiO2 surfaces was studied. The dependence of adsorption of the Zn(II), Sr(II) and Ba(II) cations on agitation time, solution acidity, and equilibrium concentrations of cations was investigated in a batch mode. It was shown that the kinetic model based on the pseudo-second order equation applied to the experimental results of adsorption of heavy metal cations by both adsorbents gives the highest coefficients of linear approximation (R2 = 0,99). Two most common adsorption theories, Langmuir and Freundlich, were used to analyze equilibrium adsorption data. Nonlinear approximation shows, that the Freundlich adsorption theory provides higher R2 and lower χ2, than Langmuir adsorption theory for adsorption of heavy metal cations by sodium-modified TiO2 surface. The maximum adsorption of the Zn(II), Sr(II) and Ba(II) cations by the sodium-modified TiO2 surface exceeds that of base sorbent with protonated surface by 2,27; 2,65 and 2,64 times, respectively. Experimental maximum adsorption values of Na-TiO2 toward zinc, strontium and barium cations are 93 mg·g−1; 208,4 mg·g−1, and 274,6 mg·g−1 respectively.Higher metal cations adsorption by Na-TiO2 is due to the Na+ cations, which released, through the ion exchange process. Sodium cations cause the dissociation of water molecules and local alkalization of the aqueous medium, which leads to the reduction of double-charged zinc, strontium and barium cations to single-charged ZnOH+, SrOH+ and BaOH+ cations respectively. Sodium-modified TiO2 involves only one ≡ТіОNa adsorption center in adsorption of the MeOH+ cation, while the protonated Н-ТіО2 sorbent spends two ≡ТіОНδ+ acid centers to bind the double-charged cation.

Adsorption of Heavy Metal Cations by Base Metal Sulfides in the Broken Spur and TAG Hydrothermal Fields, Atlantic Ocean

Data on the mineral and chemical composition of samples of sulfide deposits from the Broken Spur and TAG (Mid-Atlantic Ridge) are presented. The main minerals in the Broken Spur field are marcasite, pyrrhotite, pyrite, chalcopyrite, and sphalerite; in sample from TAG: chalcopyrite, pyrite, and marcasite. It has been established that these sulfide minerals of Fe, Cu, and Zn are natural ion exchangers and belong to the class of adsorbents. Exchange capacity of sulfide minerals in terms of heavy metal cations (Ni2+, Co2+, Cd2+, and Pb2+) is 0.022–0.32 mg-equiv/g. In the exchange reaction products, the mineral composition of sulfide deposits is retained, and new phases do not appear. It is suggested that the adsorbed heavy metal cations populate either vacant cationic or interstitial defect sites in the structures of sulfide minerals. Bond strength of the adsorbed heavy metal cations with the main structural elements of minerals is low, which is confirmed by their high extraction in an acid medium. The results of adsorption-desorption experiments indicate two forms of heavy metal cations in sulfide minerals: adsorbed (basic) and chemically bound.

Physical study of cobalt ferrite and its application in purification of water

The purpose of this work to find the effect of magnetic material on adsorption of heavy metal cations (Cr6+, Cd2+ and Cu2+). Consequently, hexagonal cobalt ferrite (CoFe2O4) was prepared simply by flash method followed by calcination. The prepared sample was characterized using X-ray diffraction and FTIR which revealed the structure of nanoferrite. Field emission scanning electron microscopy and EDX explore the hexagonal-shaped product. The obtained results from surface area analysis (BET) showed that cobalt ferrite has large surface area (71.564 m2/g). The magnetic properties were studied by VSM and Faraday’s method from which the sample acts as ferromagnetic material with large value of saturation magnetization (66.380 emu/g). Electrical properties such as conductivity and activation energy were studied using LCR bridge; the data confirmed semiconductor behavior of sample. The sample under investigation exhibited very good adsorption efficiency for heavy metal cation (Cr6+, Cd2+ and Cu2+) from wastewater. The maximum adsorption appeared for Cd6+ at pH 6 and contact time 8 h.

Mechanisms of Adsorption of Heavy Metal Cations from Waters by an Amino Bio-Based Resin Derived from Rosin.

Rosin derived from conifer trees is used as the basis for a novel environmentally-friendly adsorbent prepared from a sustainable resource. After treatment with ethylenediamine, ethylenediamine rosin-based resin (EDAR) is produced, which possesses cation exchange capacity that is comparable to that of the best commercial synthetic resins. This is demonstrated by its application to the removal of Pb, Cd, and Cu from water, in single and multicomponent systems. Maximum uptake was obtained at pH 5 and in the order Pb(II) > Cd(II) > Cu(II). The maximum adsorption of Pb was ~1.8 mmol/g, but the adsorption process resembled the Freundlich isotherm, whereas the adsorption of Cd(II) and Cu(II) followed the Langmuir isotherm. In the multicomponent systems, there was direct competition between Pb and Cd for sorption sites, whereas the results with Cu indicated it had a preference for different types of sites compared to Pb and Cd. The EDAR resin could be efficiently regenerated and used repeatedly with only a small decrease in performance. Characterization of EDAR, and investigations of its adsorption mechanisms using physical, spectroscopic, and theoretical techniques, including fourier transform infrared spectroscopy (FTIR), 13C nuclear magnetic resonance (13C NMR), scanning electron microscope (SEM), Brunauer Emmett Teller (BET) method, elemental analysis, thermogravimetric analysis (TGA), and molecular dynamics calculations, showed that amino groups have a critical role in determining the cation adsorption properties. We conclude that this new adsorbent derived from an abundant natural material has the potential to make valuable contributions to the routine removal of heavy metal ions (HMs) from drinking water and wastewater.

Pectin adsorption on amorphous Fe/Al hydroxides and its effect on surface charge properties and Cu(II) adsorption

The purpose of this study was to elucidate the mechanisms for pectin-enhanced adsorption of heavy metal cations on variable charge minerals. Batch experiments were conducted to investigate the adsorption of pectin and copper(II) by amorphous Fe/Al hydroxides. The morphology, mineralogy, and functional groups of pectin–Fe/Al hydroxides were examined using X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy analysis. The amount of pectin adsorbed by amorphous Al(OH)3 was much greater than that by amorphous Fe(OH)3 at pH values between 3.5 and 6.5 due to the higher positive charge density on Al(OH)3 and greater electrostatic attraction between the hydroxide and pectin compared with Fe(OH)3. The addition of pectin decreased the positive surface charge on amorphous Fe and Al hydroxides. The presence of pectin enhanced the adsorption of Cu(II) by the Fe and Al hydroxides. The increase in Cu(II) adsorption on amorphous Fe hydroxide was more obvious at low pH values than at higher pH values, while an opposite changing trend was observed for amorphous Al hydroxide. At pH 3.9, 4.3, and 4.9, pectin increased Cu(II) adsorption by Fe hydroxide from 24.4, 76.6, and 177.0 mmol/kg to 61.6, 98.8, and 192.0 mmol/kg, i.e., Cu(II) adsorption was increased by 37.2, 22.2, and 15.0 mmol/kg, respectively. At pH 4.3 and 4.9, pectin increased Cu(II) adsorption by Al hydroxide from 3.7 and 27.0 mmol/kg to 17.3 and 69.4 mmol/kg, i.e., Cu(II) adsorption was increased by 13.6 and 42.4 mmol/kg, respectively. The greater adsorption of pectin by Al hydroxide was mainly responsible for the larger enhancement of pectin on Cu(II) adsorption on Al hydroxide at higher pH values compared with Fe hydroxide. The adsorption of pectin on Fe and Al hydroxides decreased the positive charge on the hydroxides and thus enhanced the adsorption of Cu(II) by the hydroxides.

Sequestration of heavy metal cations on montmorillonite by thermal treatment

Clay minerals are low-cost, high-efficient, and environmentally-friendly adsorbents for heavy metal cations. Proper disposal of the spent clay minerals, however, is still a big challenge holding back their wide applications in environmental remediation. In this work, the spent montmorillonites (Mt) after the adsorption of Cu2+ or Cd2+ were thermally treated, with the aim of in-situ sequestrating the adsorbed heavy metal cations. The structural characteristics of the calcined Mt samples were investigated using X-ray diffraction and X-ray photon spectroscopy, and the sequestration efficiency was tested by ammonium acetate and HCl washing. The results of this work demonstrated that Cu2+ cations could migrate into both the ditrigonal cavities on the tetrahedral sheet and vacant sites on the octahedral sheet of Mt after thermal treatment due to its small ion radius. In this case, Cu2+ cations could be efficiently sequestrated on Mt layers, e.g., less than 3.2% desorption by ammonium acetate washing and less than 5% desorption by HCl washing for the 400°C treated Cu–Mt. As for Cd2+ cations, they could hardly migrate into Mt layers, and thus much higher calcination temperature (e.g., 700°C) was needed to efficiently sequestrate them on Mt. In this case, Cd2+ cations were mainly sequestrated by the collapse of Mt layers and/or the deformation of Mt structure, which could block the desorption pathway for Cd2+ cations. Interestingly, as the thermal treatment temperature increased to a critical value (i.e., 400°C for Cu–Mt and 500°C for Cd–Mt), the structural Al3+ could be preferably dissolved by HCl than the adsorbed heavy metal cations; ammonium acetate could hardly dissolve the structural Al3+. This work demonstrated that thermal treatment could be a practical method for safe disposal of the spent Mt after the adsorption of heavy metal cations.

Adsorption of heavy metal cations by Na-clinoptilolite: Equilibrium and selectivity studies

This paper summarizes the conclusions of experiments conducted on the adsorption of Cd2+, Co2+, Cu2+, Mn2+, Ni2+, Pb2+ and Zn2+ onto zeolite. The focus of the experiments was to establish the influence of the initial pH of the contact solution as well as the selectivity of zeolite on the efficiency of the adsorption process. To this end, experimental adsorption isotherms were established for the pH values ranging from 1 to 4 by using the Na-form of clinoptilolite (particle size range 0.5–1 mm) as an adsorbent. Langmuir, Freundlich and Dubinin-Raduschkevich isotherm models were used to validate the experimental data and the Gibbs free energy was calculated based on the distribution coefficient. From the Langmuir model, correlations between the maximum adsorption capacity and selected physical–chemical parameters of the cations studied were established. The results of the experiments suggest that the selectivity of zeolite is strongly influenced by the pH of the contact solution, dehydration energy of cations, diffusion coefficient and the pH at which the precipitation of hydroxides occurs.

Adsorption Studies for the Removal Heavy Metal by Chitosan-G-Poly (Acrylicacid-Co-Acrylamide) Composite

In present research work natural bio polymer “Chitosan” was grafted onto Acrylic acid and Acrylamide and adsorption of some heavy metal studied by batch method. Synthesis of grafted chitosan supersorbent was synthesized by radical polymerization method. The adsorption of heavy metal cations, Cu(II), Cd(II), Ni(II), and Pb(II) from aqueous solution by newly-synthesized superabsorbent composite of chitosan-g-poly (acrylicacid-co-acrylamide) was investigated. The superabsorbent gel was characterized on the basis of FTIR, X-ray differation, Scanning electron Microscopy and thermal properties. The percentage adsorptions of metal ions on adsorbent were determined by batch methods using atomic absorption spectrophotometry (AAS). The effect of experimental parameters, such as pH, treatment time, temperature, adsorbent dose, initial metal ion concentra¬tion on the removal of metal ions was also studied. Chitosan-g-poly (acrylicacid-co-acrylamide) proved to be an effective adsorbent for the removal of different heavy metal ions from aqueous solution.

Preparation and characterisation of tamarind 4-hydroxybenzoic acid (THBA) resin and its use in extraction of heavy metal ions from industrial wastewater

The adsorption of heavy metal cations, Pb(II), Cd(II), Cu(II), Zn(II) and Fe(II) from aqueous solution by newly-synthesized tamarind 4-hydroxybenzoic acid (THBA) resin was investigated. The resin was characterised on the basis of FTIR, elemental analysis, ion-exchange capacity and physico-chemical properties. The distribution coefficients (Kd) and percentage adsorption of metal ions on resin were determined by batch methods using atomic absorption spectrophotometry (AAS). The effect of experimental parameters, such as pH, treatment time, temperature, adsorbent dose, initial metal ion concentration and flow rate, on the removal of metal ions was also studied. THBA resin proved to be an effective adsorbent for the removal of different heavy metal ions from aqueous solution; removal efficiency followed the order: Fe(II) > Cu(II) > Zn(II) > Cd(II) > Pb(II). These results suggest that the cation exchange resin THBA holds great potential to remove cationic heavy metal species from industrial wastewater.

Adsorptive Removal of Metal (Cu++, Co++ and NI++) Ions from Aqueou Solution Over Powdered Activated Carbon: A Kinetic and Equilibrium Study

Water pollution is one of the most undesirable environmental problems in the world and it requires solutions. Textile industries produce a lot of wastewater, which contains a number of contaminants, including acidic or caustic dissolved solids, toxic compounds and many different dyes. Many of the heavy metals are hazardous and may affect aquatic life causing various diseases and disorders. The aim of the present work is to explore the possibility of using these carbonaceous materials as low-cost adsorbents. The removal of heavy metals from industrial effluents is a major priority before their discharge on environment. Developed processes require expensive and in many cases advanced technologies. Commercially activated carbon is more costly, such that cost of investment may not permit to use effectively. We report that the low cost carbon system, which were obtained from used up commercial batteries Nippo and BPL are used for the effective adsorption of heavy metal cations, Cu ++ , Ni ++ and Co ++ , colouring metal ions also adsorb active low molecular weight organic compounds like phenols, carboxylic acid and phenyl acetic acid. Carbon d o s e required for maximum percentage of adsorption was found as 55.8, 50.5 and 54.2 in the case of Cu ++ , Ni ++ and Co ++ ions respectively per gram of isotherm constants after studying Langmuir and Freundlich method were determined. Plot of metal ion adsorbed in mg vs. equilibrium metal concentration are linear at low concentration and flat at higher concentration. This supports the Langmuir theory that the intermolecular forces between the sorbate and sorbent would not be significant beyond the first sorbed layer and that a portion of the sorbate molecules adheres, while the remainder renounce into the liquid phase. Under the kinetics, the plots of the concentration of metal ions i.e. log (1-u (t)) vs. contact time are linear, indicates that the sorption could be a first order reversible kinetics.

Dynamic hydrothermal synthesis of Al-substituted 11 Å tobermorite from solid waste fly ash residue-extracted Al2O3

Fly ash residue (hereafter, FAR) is the by-product of pulverized coal combustion fly ash-extracted Al2O3. It results in a hazardous industrial solid waste if it does not have appropriate treatment and utilization. Al-substituted 11 A tobermorite is successfully synthesized from FAR/SiO2 mixture by dynamic hydrothermal treatment at 220 °C for 6 h. FAR and its hydrothermal reaction products are studied by chemical analysis, XRD, SEM, FTIR, and BET methods. The XRD results show that dicalcium silicate existing in FAR has been converted into tobermorite after the hydrothermal treatment. The main crystalline phases of product are Al-substituted 11 A tobermorite and minor calcite. SEM results show that the hydrothermal products of the FAR/SiO2 mixture consist of many tiny needlelike and platy crystals which form micro-porous spherical particles, ranging in size from a few microns to dozens of microns, and have a specific surface area of 49.004 m2/g. The Al-substituted tobermorite-bearing products have a high performance of exclusion of Cr3+ from acidified aqueous media, and the adsorption efficiency of Cr3+ is 98 %. The exclusion reaction proceeds rapidly, reaching equilibria within 1 h. The results show that this product has a potential to be used in industrial processes for adsorption of heavy metal cations from wastewater.

New Applications of Sulfonated Derivatives of Polystyrene Waste

The solid silica sulfuric acid was used to heterogeneous sulfonation of polystyrene waste dissolved in organic solvent. After sulfonation, small suspended particles of polystyrene derivatives were easily separated from much bigger particles of silica sulfuric acid by filtration and from solvent mostly by decantation and additionally by evaporation. The characteristics of adsorption of heavy metal cations on resins from polystyrene were compared with that of commercial resins. It was proved that synthesized resins are effective cation exchangers. The advantage of obtained resins was their high rate of metal removal.

Prediction of metal-adsorption behaviour in the remediation of water contamination using indigenous microorganisms

In recent years, the adsorption of heavy metal cations onto bacterial surfaces has been studied extensively. This paper reports the findings of a study conducted on the heavy metal ions found in mine effluents from a mining plant where Co(2+) and Ni(2+) bearing minerals are processed. Heavy metal ions are reported to be occasionally present in these mine effluents, and the proposed microbial sorption technique offers an acceptable solution for the removal of these heavy metals. The sorption affinity of microorganisms for metal ions can be used to select a suitable microbial sorbent for any particular bioremediation process. Interactions of heavy metal ions (Co(2+) and Ni(2+)) and light metal ions (Mg(2+) and Ca(2+)) with indigenous microbial cells (Brevundimonas spp., Bacillaceae bacteria and Pseudomonas aeruginosa) were investigated using the Langmuir adsorption isotherm, pseudo second-order reaction kinetics model and a binary-metal system. Equilibrium constants and adsorption capacities derived from these models allowed delineation of the effect of binding affinity and metal concentration ratios on the overall adsorption behaviour of microbial sorbents, as well as prediction of performance in bioremediation systems. Although microbial sorbents used in this study preferentially bind to heavy metal ions, it was observed that higher concentrations (>90mg/ℓ) of light metal ions in multi-metal solutions inhibit the adsorption of heavy metal ions to the bacterial cell wall. However, the microbial sorbents reduced Ni(2+) levels in the mine-water used (93-100% Ni(2+) removal) to below the maximum acceptable limit of 350μg/ℓ, established by the South African Bureau of Standards. Competition among metal ions for binding sites on the biomaterial surface can occur during the bioremediation process, but microbial sorption affinity for heavy metal ions can enhance their remediation in dilute (<5mg/ℓ heavy metal) wastewaters.

Efficient separation of heavy metal cations by anchoring polyacrylic acid on superparamagnetic magnetite nanoparticles through surface modification

Magnetite nanoparticles are an exceptional adsorbent materials due to their magnetic properties and good adsorption capacity. The aim of this work is to investigate the suitability of magnetite nanoparticles for adsorption of heavy metal cation and its efficiency. Magnetic iron oxide nanoparticles were successfully prepared by a coprecipitation method followed by modification with 3-aminopropyl triethoxysilane (APTES) and acryloyl chloride (AC) subsequently. Then the surface of modified nanoparticles was modified by graft polymerization with acrylic acid. The grafted magnetite nanoparticles were next used for separation of heavy metal cations. The adsorption of heavy metal cations from aqueous solution by polyacrylic acid grafted onto magnetite nanoparticles was studied too. The ability of heavy metal adsorption of these nanoparticles for removal from aqueous solutions was measured with atomic absorption technique and they showed their potential for the separation of heavy metal cations such as Cd 2+, Pb 2+, Ni 2+ and Cu 2+. The obtained nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA) and DSC analyses with the size ranging from 10 to 23 nm. The magnetite nanoparticles exhibited superparamagnetism above 300 K and the saturation magnetization was 57.1 emu/g at 300 K.

Synthesis of nanoporous TiO2 materials using a doubly surfactant system and applying them as useful adsorbents

Hydrothermal and non-hydrothermal nanoporous TiO2 materials were synthesized via a doubly surfactant route by using cationic cetyltrimethylammonium bromide and anionic sodium dodecyl sulfate surfactants as the molecular template/structure directing agent. Hydrothermal treatment was performed for comparison. The bulk chemical and phase compositions, crystalline structures, particle morphologies, thermal stabilities and surface texturing were determined by means of X-ray powder analysis, SEM and N2 sorptiometry. The nanoporous TiO2 materials were found to have a spherical morphology with a diameter range of 50–200 nm and a high surface area (390 m2 g−1). Hydrothermal and non-hydrothermal nanoporous TiO2 materials were applied for adsorption of heavy metal cations and the toxic organic compound, copper phthalocyanine, from water for evaluation of their adsorption properties. Both nanoporous TiO2 materials were found to have similar adsorption capacities toward heavy metal cations and CuPc. Both hydrothermal and non-hydrothermal TiO2 nanoporous materials were found to have very good potential for application as a new adsorbent especially for adsorbing heavy metal cations from wastewaters.