Biosorption of copper ions from aqueous solutions by Spirulina platensis biomass

In this study, the economically important micro-alga (cyanobacterium) Spirulina platensis was used as biosorbent for the removal of copper from aqueous solutions. The cyanobacterium was exposed to various concentrations of copper and adsorption of copper by the biomass was evaluated under different conditions that included pH, contact time, temperature, concentration of adsorbate and the concentration of dry biomass. Increased adsorption of copper by the non-living biomass was recorded with gradually increasing pH, and a maximal uptake by the biomass was observed at pH 7. The adsorption of copper was found to increase gradually along with decrease in biomass concentration. Biosorption was found to be at a maximum (90.6%), in a solution containing 100 mg copper/L, at pH 7, with 0.050 g dry biomass and at 37 °C with 90 min of contact time. Analysis of the spectrum obtained with atomic absorption spectrophotometer (AAS), indicated that the adsorbent has a great potential to remove copper from aqueous media contributing to an eco-friendly technology for efficient bioremediation in the natural environment.     

Pervaporation separation of water/alcohol mixtures using composite membranes based on polyelectrolyte multilayer assemblies

Composite pervaporation membranes composed of an asymmetric polyamide-6 membrane and an ultrathin self-assembled polyelectrolyte separating layer are described. The supporting membrane was prepared from both an unmodified polyamide-6 and a comb-like polymer with carboxyl terminated polyamide-6 side chains. A high end group concentration was found to be advantageous for sufficient adhesion of the multilayer systems on the supports. Up to 20 layers were deposited onto the membrane surface by dipping the membranes in aqueous solutions containing oppositely charged polyelectrolytes. The polyanions used were poly(acrylic acid), poly(styrene sulfonic acid) and alginic acid. The polycations used were poly(diallyldimethylammoniumchloride), chitosan and poly(ethylenimine). Performance of these membranes depends strongly on the layer number and on the type of polyelectrolytes. In general, membranes modified with two weak polyelectrolytes of high charge density gave the best separation properties while those modified with strong polyelectrolytes of low charge density led to poorer separation properties. However, the highest separation factor (≥10,000) for a water/2-propanol mixture (12/88 w/w) at permeate flux of 300 g/m²h was obtained with six double layers consisting of poly(ethylenimine) and alginic acid. These composite membranes were stable over an operating period of at least 400 h.     

Enhancing the ion-transport selectivity of multilayer polyelectrolyte membranes

Alternating adsorption of polycations and polyanions on permeable supports provides a convenient and versatile method for preparing composite membranes with selective, ultrathin polyelectrolyte skins. Control over charge and composition in the polyelectrolyte skin allows highly selective separation of ions according to charge, size, or hydration energy.     

High-flux nanofiltration membranes prepared by adsorption of multilayer polyelectrolyte membranes on polymeric supports

Layer-by-layer deposition of anionic and cationic polyelectrolytes readily converts polymeric ultrafiltration membranes into materials capable of nanofiltration. ATR-FTIR spectra confirm that layer-by-layer deposition occurs on the ultrafiltration substrates, and adsorption of as few as 2.5 bilayers of poly(styrenesulfonate) (PSS)/protonated poly(allylamine) (PAH) or 3.5 bilayers of PSS/poly(diallyldimethylammonium chloride) (PDADMAC) reduces the molecular weight cutoff of polyethersulfone ultrafiltration supports from 50 kDa to <500 Da. Deposition of multilayer polyelectrolyte films on 300 and 500 kDa membranes also decreases molecular weight cutoffs, but solute rejections are significantly lower when using these supports, suggesting that the polyelectrolyte films do not completely cover large (0.2-0.4 microm in diameter) pores. On the 50 kDa substrates, PSS/PDADMAC films containing 3.5 bilayers exhibit a 95% rejection of SO(4)(2-) and a chloride/sulfate selectivity of 27, whereas 4.5-bilayer PSS/PAH coatings show a glucose/raffinose selectivity of 100. Pure water flux for [PSS/PAH](3)PSS-coated membranes at 4.8 bar is 1.6 m(3)/(m(2)day), which is more than 2-fold higher than that through a commercial 500 Da membrane.     

Efficiency of succinylated-olive stone biosorbent on the removal of cadmium ions from aqueous solutions

Chemical functionalization of olive stone wastes with succinate linkers can potentially improve the performance of wastewater treatment technologies via enhanced adsorption and high affinity of the covalently attached succinate groups for heavy metals. In this study, a novel reusable adsorbent material based on agricultural waste has been synthesized by esterifying the lignocellulosic matrix of olive stones with succinic anhydride in toluene under basic conditions. Characterization of the as-prepared material by FTIR and solid-state MAS ¹³C NMR spectroscopies and TGA confirmed that the heterogeneous esterification has proceeded very efficiently to yield the succinylated-olive stone (S–OS). Subsequent alkaline treatment of S–OS with saturated NaHCO₃ aqueous solution led to the resulting sodic material (NaS–OS), which was subjected to batch experiments in order to evaluate its cadmium-removing efficiency from aqueous solutions at realistic concentrations of cadmium found in industrial effluents. The results obtained from the sorption characteristics have revealed that NaS–OS material is highly effective in removing cadmium from aqueous solutions, with a maximum uptake capacity of 200 mg g⁻¹ (1.78 mmol g⁻¹). The Langmuir isotherm model was found to fit adequately the equilibrium isotherm data. Cadmium adsorption occurs rapidly and the adsorption mechanism is a chemical sorption via ionic exchange between the adsorbate and adsorbent. Thermodynamic parameters were also evaluated from the effect of temperature studies. Regenerability of NaS–OS material was ascertained by quantitative desorption of cadmium with 1 M aqueous NaCl and the reusability of the matrix after five repeated cycles led to nearly no attenuation in its performance (less than 2% in the sorption capacity), indicating that repeated use of NaS–OS is quite feasible. Compared to other low-cost adsorbents utilized for the removal of Cd(II) from water/wastewater, NaS–OS shows higher sorption capacity. These results have important implications for the design of low-cost adsorbents based on agricultural wastes.     

Synthesis of calcium alginate nanoparticles for removal of lead ions from aqueous solutions

Calcium alginate nanoparticles (CANPs) were synthesized to remove lead ion [Pb(??)] as pollutant of environment from aqueous solutions. The produced CANPs were characterized by Fourier transform infrared spectroscopy (FTIR), particle size analysis (PSA) and scanning electron microscope (SEM). Various factors, which affected adsorption efficiency of lead ions by CANPs, such as pH (pH from 1 to 8), initial ions concentration (in the range of 25 to 125 mg L^–1), contact time (varying from 5 to 120 min), and adsorbent dose (50 to 500 mg L^–1), were investigated for determination of optimum experimental conditions. The result of tests showed that the investigated factors had significant effects on adsorption of Pb(??) ions and the maximum adsorption percentage of lead at pH = 6~7, 25 mg L^–1 initial ions concentration, contact time of more than 140 min. and for adsorbent dose at 500 mg L^–1. Also these results demonstrated the effective adsorption of Pb²⁺ ions by synthesized CANPs that occurred due to a high surface area of CANPs and the presence of anionic carboxylate functional groups and allowed effective absorbing and removing Pb(??) ions from aqueous solutions. Thus, these nanoparticles were able to remove over 99% of lead ions from solution.     

Metalloporphyrin–polyelectrolyte assemblies in aqueous solution: Influence of the metal center and the polyelectrolyte architecture

This study investigates the influence of different metal centers in porphyrins and of different polyelectrolyte architectures on the formation of supramolecular metalloporphyrin–polyelectrolyte assemblies in aqueous solution via electrostatic self‐assembly. Metal‐analogues of the tetravalent anionic meso‐tetrakis(4‐sulfonatophenyl)‐porphyrin (with Zn²⁺, Co²⁺, Ni²⁺, Mn³⁺, and Fe³⁺) are combined with the cationic dendrimer of generation 4 or with the linear polydiallyldimethyl‐ammoniumchloride. Dynamic light scattering and atomic force microscopy reveal that the different molecular geometries of the metalloporphyrins resulting from axial ligands determine the size and the stability of the aggregates. A thermodynamic study elucidates the importance of the polymer architecture in controlling the size of the assembly and the role of the metal center. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 484–500     

Highly efficient removal of toxic lead ions from aqueous solutions using a new magnetic metal‐organic framework nanocomposite

A magnetic metal‐organic framework (MOF) nanocomposite was successfully prepared by a new and green strategy through reasonable design. Magnetic MOF of Fe₃O₄‐NHSO₃H@HKUST‐1 nanocomposite use for removal of lead ions as an environmental pollutant. The experimental results indicated that the nano adsorbent of Fe₃O₄‐NHSO₃H@HKUST‐1 can removed lead ions under optimum operational conditions. The dosage of the nanocomposite, pH of the sample solution, and contact time were obtained to be 10 mg, 7.0, and 90 min, respectively, while the initial concentration of Pb(II) ions of 400 mg/L was used. A kinetic study indicated that a pseudo‐second‐order model agreed well with the experimental data. The isotherm experiments revealed that the Langmuir model attained better fits to the equilibrium data than the Freundlich model. The maximum adsorption capacity of the adsorbent for the removal of lead under the optimum operational conditions of pH 7.0 and temperature 25°C was found to be 384.6 mg/g. The thermodynamic parameters indicate that the adsorption of lead is spontaneous and endothermic. The magnetic MOF nanocomposite could be recovered easily and reused many times without significant loss of its nano‐adsorbent activity. The proposed method is simple, eco‐friendly, low cost, and efficient in the removal of lead ions from aqueous solutions.     

Kinetic modeling analysis for the removal of cesium ions from aqueous solutions using polyaniline titanotungstate

Polyaniline titanotungstate has been synthesized by incorporation of organic polymer polyaniline into the inorganic precipitate of titanotungstate. This material was characterized using X-ray, IR and TGA studies. The influences of initial concentration of metal ions, particle size and temperature have been reported. The comparison of composite and inorganic materials was studied and indicating that the composite material is better than the inorganic in selectivity of Cs⁺ ions. Thermodynamic parameters, such as changes in Gibbs free energy (ΔG), enthalpy (ΔH), and entropy (ΔS) have been calculated. The numerical values of ΔG decrease with an increase in temperature, indicating that the sorption reaction of adsorbent was spontaneous and more favorable at higher temperature. The positive values of ΔH correspond to the endothermic nature of sorption processes and suggested that chemisorptions were the predominant mechanism. A comparison of kinetic models applied to the sorption rate data of Cs⁺ ions was evaluated for the pseudo first-order, the pseudo second-order, intraparticle diffusion and homogeneous particle diffusion kinetic models. The results showed that both the pseudo second-order and the homogeneous particle diffusion models were found to best correlate the experimental rate data. Self diffusion coefficient (D_i), Activation energy (Ea) and entropy (ΔS^*) of activation were also computed from the linearized form of Arrhenius equation.     

Ligand adsorption on an activated carbon for the removal of chromate ions from aqueous solutions

The results presented in this work are related to the design of a guideline to develop specific properties at the surface of an activated carbon (AC). For this, two model aromatic compounds have been synthesized and their electrolytic behavior in aqueous solutions was studied by a potentiometric method. The textural characteristics of the activated carbon were determined by porosimetry methods. The nature of oxygen-carrying functions and the acid-base behavior of the AC surface were characterized by TPD and potentiometric titration methods, respectively. The adsorption and desorption equilibria of the aromatic compounds on activated carbon were measured in aqueous solutions, and the hysteresis between adsorption and desorption, which reveals irreversible adsorption, was discussed on the basis of the frontier orbital theory. HOMO and LUMO orbitals of the adsorbent and adsorbates were calculated, and irreversible adsorption was attributed to the small energy difference between HOMO and LUMO of the aromatic adsorbates and the adsorbent. Adsorption equilibria of K2CrO4 in aqueous solution on the AC alone and on the AC-aromatic ligand adsorbents, respectively, prove the efficient development of specific chemical functions at the carbon surface provided by the adsorbed aromatic compounds.     

Sorption investigation on the removal of metal ions from aqueous solutions using chelating terpolymer resin

A novel chelating terpolymer resin has been synthesized from anthranilic acid, phenylhydrazine, and formaldehyde by condensation in glacial acetic acid. The structure of the chelating resin was clearly elucidated by use of a variety of spectral techniques, for example FTIR, and ¹H and ¹³C NMR spectroscopy. The average molecular weight of the terpolymer resin was determined by gel-permeation chromatography. The empirical formula and empirical weight of the resin were determined by elemental analysis. The physicochemical properties of the terpolymer resin were determined. Scanning electron microscopy was used to establish the surface features of the chelating resin. The ion-exchange behaviour of the resin for specific metal ions, viz. Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, and Pb²⁺, was evaluated by a batch equilibrium method. The study was extended to three variations: evaluation of metal ion uptake in the presence of different electrolytes at different concentrations; evaluation of metal ion uptake at different pH; and evaluation of metal ion uptake at different times. Further, the reusability of the resin was also determined to assess the efficiency of the resin after a few cycles of sorption. From the results it was observed that the resin acts as an effective chelating ion-exchanger.     

Separation of fluoride from other monovalent anions using multilayer polyelectrolyte nanofiltration membranes

Nanofiltration (NF) is an attractive technique for reducing F- concentrations to acceptable levels in drinking water, but commercial NF membranes such as NF 270 and NF 90 show minimal Cl-/F- selectivity. In contrast, simple layer-by-layer deposition of 4.5-bilayer poly(styrene sulfonate) (PSS)/poly(diallyldimethylammonium chloride) (PDADMAC) films on porous alumina supports yields NF membranes that exhibit Cl-/F- and Br-/F- selectivities>3 along with solution fluxes that are >3-fold higher than those of the commercial membranes. Fluoride rejection by (PSS/PDADMAC)4PSS membranes, which is >70%, is independent of pressure over a range of 3.6 to 6.0 bar, suggesting that the primary transport mechanism in these films is convection. Moreover, the fact that Br-/F- selectivity is 12% higher than Cl-/F- selectivity suggests that discrimination among the monovalent ions is based on size (Stokes radius). Chloride/fluoride selectivities are essentially constant over Cl-/F- feed ratios from 1 to 60, so these separations will be viable over a range of conditions. Interestingly, PSS/protonated poly(allylamine) films show little Cl-/F- selectivity, and the selectivity of PSS/PDADMAC membranes is a strong function of the number of deposited layers, indicating that NF properties are very sensitive to film structure.     

Response surface methodology for the modelling of copper removal from aqueous solutions using micellar-enhanced ultrafiltration

Response surface methodology (RSM) was used to study the cumulative effect of the various parameters, namely surfactant (sodium dodecyl sulphate (SDS), anionic) concentration, pH, and surfactant/metal molar ratio and to optimise the process conditions for the maximum removal of copper from aqueous solutions via micellar-enhanced ultrafiltration (MEUF). For obtaining the mutual interaction between the variables and optimising these variables, a central composite design (CCD) by use of response surface methodology was employed. The analysis of variance (ANOVA) of the quadratic model demonstrated that the model was highly significant. The model was statistically tested and verified by experimentation. Values of pH at the range of ca. 7.5 were very successful for the separation. The maximum rejection coefficient of 98.4% was obtained for the following optimal conditions: SDS/Cu²⁺ molar ratio *r = 7.85, *pH 7.36, *C_surf = 6.82 g/l SDS. A modification of micellar-enhanced ultrafiltration for the removal of copper from aqueous solutions was studied by the implementation of sodium dodecyl sulphate–polyethylene glycol (PEG) aggregates. A full factorial design (FFD) was employed for studying the effect of molar ratio of surfactant/metal, pH and mass ratio of surfactant/polymer at a constant concentration of surfactant equal to 5 g/l. The comparison of the two systems in the region of their common factors showed that the addition of polyethylene glycol caused a slight increase in rejection coefficient of copper but also could function as ‘scavenger’ for surfactant species.     

Radium removal from aqueous solutions by variously supported ligands

A set of ligands loaded on various supports have been tested to remove radium from aqueous solutions. Crown ethers have demonstrated inefficiency in all cases, while open chain ligands (podands) have shown satisfactory distribution coefficients and uptake rates in particular conditions. Hypotheses to explain the phenomenon are briefly discussed.     

Adsorption of copper(II) ions from aqueous solutions on alumina industrial wastes

Equilibrium adsorption of copper(II) ions on red mud (alumina industrial wastes) modified by various methods was studied. The effect exerted by the nature the modifier (NaHSO₄, NaCl + HCl, and H₂SO₄) on the sorption activity of red mud was determined.     

Electrosorption of ions from aqueous solutions by nanostructured carbon aerogel

Electrosorption is generally defined as potential-induced adsorption on the surface of charged electrodes. After polarization of the electrodes, ions are removed from the electrolyte solution by the imposed electric field and adsorbed onto the surface of the electrodes. Experimental and modeling studies were conducted using two types of carbon aerogel composites of different surface areas to provide a better understanding on the mechanisms of electrosorption. The experimental results revealed that no significant specific adsorption of F- ions occurred, while strong specific adsorption was observed for NO3- and Cu2+ ions. In addition, although the two types of carbon aerogel electrodes had different surface areas, their capacities were found to be very similar because of the electrical double-layer overlapping effect in micropores. An electrical double-layer model developed in our previous work (16), in which the electrical double-layer overlapping correction is included, is expanded in the present work by considering the effect of the specific adsorption on the electrosorption process. Modeling results were compared with experimental data obtained under various conditions. When the overlapping effect and specific adsorption were considered, the model provided results that were in good agreement with experimental data.     

Remediation of copper ions from aqueous solution using hybrid magadiite: kinetics,isotherm and mechanism of removal

Research on Chemical Intermediates - This paper deals with the potential use of hybrid magadiite composite as an alternative adsorbent for the removal of copper ions. Na-magadiite was synthesized...     

Optimized mercapto-modified resorcinol formaldehyde xerogel for adsorption of lead and copper ions from aqueous solutions

Journal of Sol-Gel Science and Technology - Resorcinol formaldehyde (RF) xerogel was modified by mercapto functional groups for removal of Pb(II) and Cu(II) ions from aqueous solutions. The...