Bicomponent Solutions Research Articles

Unravelling competitive adsorption phenomena in the aqueous phase reforming of carboxylic acids on Pt catalysts: An experimental and theoretical study

Biorefinery-derived wastewater is considered a valuable source of energy and chemicals thanks to its organic loading. However, it is constituted by different compounds which influence the performance of a catalytic valorization process. In this work, we investigated the treatment of a synthetic hydrothermal liquefaction-derived wastewater (HTL-WW) via aqueous phase reforming (APR) to obtain hydrogen. As a case study, we examined the underlying driving forces for performance differences in the APR of mono- and bi-component solutions of carboxylic acids as a model corn stover HTL-WW over Pt catalysts via a combined experimental and theoretical approach. In mono-component solutions, the conversion ranked as glycolic acid > propionic acid ≈ acetic acid, and the same was found for the hydrogen production tendency. Binary solutions of glycolic and acetic acid, with different concentration among the constituents, showed a strong inhibition of the acetic acid reactivity due to the prevalent adsorption of glycolic acid on Pt surface. The results from the APR of acetic and propionic acid solutions were less affected by such phenomena. DFT results showed that there are strong, attractive lateral interactions between carboxylic acids due to intermolecular hydrogen bonding that cause all carboxylic acids to preferentially adsorb in dimer structures. The lateral interaction strength was determined for both pure and binary mixtures of carboxylic acid dimers, with results showing that pure mixtures of carboxylic acids have stronger attractions and that glycolic acid dimers see the strongest attractions due to the added terminal hydroxyl functional group. The findings presented herein offer significant insights into the utilization of APR for industrial-like multi-component solutions, as well as for any catalytic process involving small organic compounds in an aqueous phase.

Recovery of rare earth elements (Nd3+ and Dy3+) by using carbon-based adsorbents from spent tire rubber

Two samples of spent tire rubber (rubber A and rubber B) were submitted to thermochemical conversion by pyrolysis process. A450, B450 and A900, B900 chars were obtained from rubber A and rubber B at 450 °C and 900 °C, respectively. The chars were then applied as recovery agents of Nd3+ and Dy3+ from aqueous solutions in mono and bicomponent solutions, and their performance was benchmarked with a commercial activated carbon.The chars obtained at 900 °C were the most efficient adsorbents for both elements with uptake capacities around 30 mg g−1. The chars obtained at 450 °C presented uptake capacities similar to the commercial carbon (≈ 11 mg g−1). A900 and B900 chars presented a higher availability of Zn ions that favored the ion exchange mechanism. It was found that Nd3+ and Dy3+ were adsorbed as oxides after Zn was released from silicate structures (Zn2SiO4).A900 char was further selected to be tested with Nd/Dy binary mixtures and it was found a trend to adsorb a slightly higher amount of Dy3+ due to its smaller ionic radius. The uptake capacity in bicomponent solutions was generally higher than for single component solutions due to the higher driving force triggered by the higher concentration gradient.

Removal of Paracetamol and Cu2+ from Water by Using Porous Carbons Derived from Agrowastes

Dende and babassu coconuts are largely used in tropical countries, namely in Brazil, for the extraction of oils from kernels. The remaining biowastes are industrially processed to produce porous carbons (PCs). PCs derived from dende and babassu biowastes and produced at an industrial scale have been characterized by textural, chemical, and ecotoxicological parameters. A commercial activated carbon (CC) of mineral origin has been used as a benchmarking material. Although the CC sample presented a higher surface area (SBET = 1083 m2/g), the PCs derived from the biowastes were richer in micropores (Vmicro = 0.25–0.26 cm3/g), while the CC carbon presented wider pore size distribution with a higher mesopore volume (Vmeso = 0.41 cm3/g). All the adsorbents used in this work have shown a non-acute ecotoxic behavior for the bacterium Vibrio fischeri (EC50-30 min > 99% v/v). The adsorbents have been tested for paracetamol and Cu2+ adsorption in mono- and bicomponent solutions. The uptake capacities of paracetamol (qe, 98–123 mg g−1) and Cu2+ (qe, 15–18 mg g−1) from monocomponent solutions were similar to the ones obtained in the bicomponent solutions, indicating no competition or cooperative effects but a site-specific adsorption. This finding represents an advantage for the removal of these adsorbates when present in the same solution as they can be adsorbed under similar rates as in the single systems. Paracetamol adsorption was related to micropore filling, π-π interactions, and H-bonding, whereas Cu2+ removal was attributed to the cation exchange mechanism and complexation to the hydroxyl groups at the carbons’ surface.

Functionalization of carbon from rubber fruit shells (Hevea brasiliensis) with silane agents and its application to the adsorption of bi-component mixtures of methylene blue and crystal violet.

In this research, activated carbon was obtained from rubber fruit shells (ACRPs). The obtained activated carbon (ACRPs) was modified by magnetite particle coating and silanization with triethoxyiphenylsilane (TEPS) to produce a new magnetic adsorbent (ACRPs-MS). The affinity of as-prepared adsorbent (ACRPs-MS) toward methylene blue (MB) and crystal violet (CV) dyes was tested in mono-component and bi-component solutions. Structural characterization proves the success of the magnetite coating process and the silanization of ACRPs. In the infrared (IR) spectroscopy spectrum of ACRPs-MS, Si-O-Fe and Si-O-Si bonds were identified, which indicated the presence of magnetite and silane. This is also supported by the elemental composition contained in the energy-dispersive X-ray (EDX) diffractogram. In addition, the presence of the porous structure of the surface of the material and the increase in the specific surface area increase the accessibility of contaminants such as MB and CV dyes to be adsorbed to the ACRPs-MS adsorption site effectively. The experimental results showed that the adsorption of mono-component MB and CV dyes by ACRPs-MS was optimum at pH8 and an interaction time of 60min. The adsorption kinetics of mono-component MB and CV dyes by ACRPs-MS tended to follow pseudo-second-order kinetics (PSO) models with PSO rate constant (k2) values of 0.198 and 0.993gmg-1min-1, respectively. The adsorption of MB and CV dyes by ACRPs-MS in a bi-component mixture tends to follow the Langmuir isotherm model with adsorption capacity (qm) values of 85.060 and 90.504mgg-1, respectively. Analysis of adsorption data on the bi-component mixture between MB and CV by ACRPs-MS with the Langmuir isotherm equation for a binary mixture resulted in qm of 22.645 × 10-3mmol equiv g-1. ACRPs-MS material can be used repeatedly five times with adsorption ability > 80%. Desorption of MB and CV dyes was carried out using 0.05M HCl solution. ACRPs-MS material was able to adsorb MB and CV dyes with a large adsorption capacity and could be used in repeated adsorption. Thus, it can be stated that ACRPs-MS can be used as an effective adsorbent for MB and CV dyes, either singly or in a bi-component mixture.

Removal of Cr(VI) and Ag(I) by grafted magnetic zeolite/chitosan for water purification: Synthesis and adsorption mechanism

In this paper, a novel grafted zeolite/Fe3O4/chitosan (ZMC-MAH-TEPA) adsorbent was greenly synthesized and evaluated for the removal of Cr(VI) and Ag(I) in single and bi-component solutions. The characterization data of XRF, XRD, FT-IR, VSM, TGA, BET and SEM showed the successful fabrication of the adsorbent with abundant -NH2 and -NH- as well as great recovery properties (11.70 emu/g). The effects of experimental parameters, including pH value, initial concentration, temperature, time, and coexisting ions on single and bi-component adsorption, were investigated. The results demonstrated that the adsorption capacities increased with the enhanced shaking time and concentration until equilibrium was reached. The optimum pH value was 3 for Cr(VI) adsorption and 5 for Ag(I) adsorption. The maximum adsorption capacities for Cr(VI) and Ag(I) ions, obtained by the Langmuir model, were 50.75 and 70.12 mg·g−1 in single metal solutions and 45.45 and 58.94 mg·g−1 in bi-component metal solutions (Cr(VI)/Ag(I) = 1:1), respectively. Additionally, the adsorption mechanism of Cr(VI) and Ag(I) was explained in terms of electrostatic interaction and hydrogen bonding between metal ions and -NH2 and -NH- in ZMC-MAH-TEPA. Taken together, this study provides a clean approach to synthesizing chitosan-based adsorbents for the efficient removal of Cr(VI) and Ag(I) ions.

Adsorption of Scandium and Yttrium from Aqueous Solutions by Purolite C100Na Resin: Equilibrium and Kinetic Modeling

ABSTRACT: Adsorption of Sc from single and bi-component Sc-Y solutions by Purolite C100Na was studied experimentally and kinetic and thermodynamic characteristics are described. The extended Freundlich isotherm was found to be successful in validating the experimental results. Moreover, curve fitting the time-dependent data into different kinetics mechanisms showed a satisfactory correlation with the pseudo-second-order model. Binary system results show a decrease in Sc adsorption capacity of the absorbent in the presence of secondary ions because of competition for adsorption sites. Furthermore, thermodynamic parameters indicate similarity of reaction mechanisms for both single and binary systems, with Sc absorption adversely affected by temperature. Data from experiments on synthetic electrolytes with Y/Sc ratio of 5 found in actual mining copper leach solution were used for extracting scandium by circulating mine-leach solution through a resin column. The results demonstrate a preferential collection of Sc ions despite the fivefold concentration of Y over Sc. The elusion studies showed that the yttrium desorption peak occurs before that of Sc which, corroborates the adsorption isotherm findings. This results in a 180 mgL-1 Sc rich solution or 60:1 concentration ratio over the original copper leach solution.

Contrastive study on β-cyclodextrin polymers resulted from different cavity-modifying molecules as efficient bi-functional adsorbents

The adsorption capacity of existing β-CD-based adsorbents is generally restrained by the limited dimension of β-CD's inherent cavity. To find an effective way to expand the inclusion/adsorption capacity of β-CD, a series of N-containing groups, amine with straight chain, imidazole with rigid five-membered ring and pyridine with rigid six-membered ring, are firstly utilized to alkylate the secondary rim of β-CD through the thiol-Michael addition. The capsulation ability of the resultant β-CD derivatives are compared and the β-CD derivatives appended with aromatic imidazole or pyridine provide extremely rich host surroundings for loading Rhodamine B (RB), which is identified by the 1H NMR titration and UV–Vis spectroscopy. The bi-functional adsorbents correlative to those β-CD derivatives are then synthesized by the polymerization of vinylated β-CD and the corresponding vinyl N-containing monomers, and applied to remove RB and Cd (II) from the aqueous condition. Governed by multiple factors such as porosity, surface charge and binding affinity, the imidazole modified β-CD adsorbent revealed the best adsorption efficiency for organic dyes and metal ions, in both single- and bi-component solutions. Our work provides effective strategy and reliable basis for the design and fabrication of β-CD-based materials with high capacity and multi-functionality.

Cadmium and iron removal from phosphoric acid using commercial resins for purification purpose.

Three commercial resins bearing sulfonic, amino phosphonic, or phosphonic/sulfonic reactive groups have been tested for the removal of iron and cadmium from phosphoric acid solutions. The sorption properties are compared for different experimental conditions such as sorbent dosage (0.5-2.5gL-1), phosphoric acid concentration (from bi-component solutions, 0.25-2M), and metal concentrations (i.e., in the range 0.27-2.7mmolCdL-1 and 0.54mmolFeL-1) with a special attention paid to the impact of the type of reactive groups held on the resins. The sulfonic-based resin (MTC1600H) is more selective for Cd (against Fe), especially at high phosphoric acid concentration and low sorbent dosage, while MTS9500 (aminophosphonic resin) is more selective for Fe removal (regardless of acid concentration and sorbent dosage). Equilibrium is reached within 2-4h. The resins can be ranked in terms of cumulative sorption capacities according the series: MTC1600H > MTS9570 > MTS 9500. Sulfuric acid (0.5-1M) can be efficiently used for the desorption of both iron and cadmiumfor MTC1600H, while for MTS9570 (phosphonic/sulfonic resin) sulfuric acid correctly desorbs Cd (above 96% at 1M concentration), contrary to Fe (less than 30%). The aminophosphonic resin shows much poorer efficiency in terms of desorption. The sulfonic resin (i.e., MTC1600H) shows much higher sorption capacity, better selectivity, comparable uptake kinetics (about 2h equilibrium time), and better metal desorption ability (higher than 98% with 1M acid concentration, regardless of the type of acid). This conclusion is confirmed by the comparison of removal properties in the treatment of different types of industrial phosphoric acid solutions (crude, and pre-treated H3PO4 solutions). The three resins are inefficient for the treatment of crude phosphoric acid, and activated charcoal pre-treatment (MTC1600H reduced cadmium content by 77%). However, MTC1600H allows removing over 93% of Fe and Cd for H3PO4 pre-treated by TBP solvent extraction, while the others show much lower efficiencies (< 53%).

Sorption of nickel (II) and manganese (II) ions from aqueous solutions

Mine water from non-ferrous metal deposits is often contaminated with nickel and manganese ions. The entry of these ions, especially nickel, into surface waters and underground aquifers is undesirable since it has a negative effect on living organisms and worsens the condition of drinking water sources. One of the promising methods for selectively extracting nickel ions and obtaining an eluate suitable for further use is sorption by weakly acid cation exchangers with chelate groups of iminodiacetic acid.&#x0D; As part of the study, sorption isotherms of nickel and manganese ions by Lewatit MonoPlus TP 207 cation exchanger in mono- and bicomponent systems were obtained. In monocomponent systems, the maximum static exchange capacity (SEC) of the cation exchanger for nickel ions is 952 mmol/dm3, and in bicomponent systems – 741 mmol/dm3; for manganese ions– 71 mmol/dm3 and 49 mmol/dm3, respectively. It is obvious that the studied cation exchanger has a greater capacity for nickel ions than for manganese ions.&#x0D; The influence of a temperature increase from 300 to 330 K on the sorption of nickel and manganese ions was established: in monocomponent systems, the maximum degree of extraction of the former increases from 65 to 77 % (SEC from 337 to 399 mmol/dm3), and the latter from 21 to 35 % (SEC – from 140 to 229 mmol/dm3); in bicomponent systems, the extraction of nickel ions increases from 59 to 78 % (SEC – from 307 to 429 mmol/dm3), and manganese ions decreases from 20 to 17 % (SEC – from 164 to 131 mmol/dm3). The predominant increase in the indicators is due to the filling of the sorption centers of the ion-exchange resins, which are energetically unfavorable for the exchange of counterions at a lower temperature.&#x0D; The influence of the pH of the solution on sorption was determined: the intensification of the process for nickel ions is observed in the pH range of 8.0-8.5 in a monocomponent solution and 8.0-9.0 in a bicomponent solution, for manganese ions in the range of 8.0-9.5 in both cases. The increase in the degree of extraction of ions and the exchange capacity of the ion exchanger with increasing pH is associated with the appearance of singly charged hydroxocations, dissociation of the functional groups of the sorbent and, to some extent, with the subsequent formation of insoluble forms of nickel and manganese. However, with increasing pH, a decrease in the selectivity of nickel extraction is observed: the ion separation coefficient decreases from 14.0 to 6.0 in the pH range of 6.0-11.0.

Nano-assembled oligosilane–pyrazoline structures and their optical properties

Specific interactions between low molecular weight poly[diphenylsilane-co-methyl(H)silane] and 1,3-diphenyl-5-{4-[(4-vinylbenzyl)oxy]phenyl}-4,5-dihydropyrazole in solution have been investigated. Thus, a concentrated polysilane solution containing low amounts of pyrazoline was irradiated with UV light using predetermined conditions to produce a photo-induced fragmentation of the polysilane backbone. Spectrophotometric analysis of the bicomponent solution before and after UV irradiation suggested that polysilane and pyrazoline interact, which leads to their aggregation. Quantum chemical calculation indicated that a nano-assembling process between the two components is possible, and proved the Van der Waals (VdW) nature of the main interactions between the two components. The association between polysilane and pyrazoline modifies considerably the internal charge transfer within pyrazoline's chromophore, which results in fluorescence quenching. The electronic effects within the aggregate were studied using quantum computational calculations. Owing to the polysilane influence, polysilane–pyrazoline nanostructures have specific optical properties, which could be used to develop novel materials with fluorescence sensing ability.

Ultrafiltration Membranes Based on Various Acrylonitrile Copolymers

The structure and properties of ultrafiltration membranes synthesized from bicomponent solutions in N,N-dimethylformamide using five commercial acrylonitrile copolymers of various compositions and molecular masses have been studied. The molecular mass characteristics of the copolymers (Mw, Mw/Mn) have been determined; the viscosity properties of dilute and concentrated solutions have been studied. It has been shown that depending on the chemical composition and molecular mass of the copolymer, the concentration dependence of the water flux is different: for copolymers with a molecular mass of Mw of 76 000–81 000 g/mol, with an increase in the copolymer concentration in solution from 12 to 16%, the water flux of the membranes decreases from 300–500 to 40–150 L/(m2 h) depending on the copolymer composition. For samples with a higher molecular mass (Mw = 99 000 and 107 000 g/mol), the water flux of the membranes hardly depends on the copolymer concentration in the casting solution; it is 150 and 75 L/(m2 h), respectively. The rejection factor of the membranes with a molecular mass of 40 000 g/mol for polyvinylpyrrolidone increases with increasing copolymer concentration in the casting solution regardless of the chemical composition and molecular mass of the copolymer. Scanning electron microscopy studies of the membrane structure have shown that membranes synthesized from copolymers with a higher molecular mass have a denser structure and a thicker selective layer than the respective parameters of membranes synthesized from acrylonitrile copolymers with a lower molecular mass, which are characterized by the presence of large macrovoids in the membrane matrix. These differences in the membrane structure are attributed to different viscosities of the casting solutions at identical copolymer concentrations.

Chitosan-based Magnetic Composites - Efficient Adsorbents for Removal of Pb(II) and Cu(II) from Aqueous Mono and Bicomponent Solutions

A series of three chitosan-based magnetic composites was prepared through a simple coprecipitation method. It was investigated the influence of mass ratio between chitosan and magnetite on the physical and chemical properties of the composites in order to establish the optimum conditions for obtaining a composite with good adsorption capacity for Pb(II) and Cu(II) from mono and bicomponent aqueous solutions. It was found that the microspheres prepared using mass ratio chitosan / magnetite 1.25/1, having a saturation magnetization of 15 emu g--1, are the best to be used as adsorbent for the metal ions. The influence of different parameters such as initial pH values, contact time, initial concentration of metal ions, on the adsorption of Pb(II) and Cu(II) onto the chitosan-based magnetic adsorbent was investigated in details. The adsorption process fits the pseudo-second-order kinetic model in both mono and bicomponent systems, and the maximum adsorption capacities calculated on the basis of the Langmuir model were 79.4 mg g--1 for Pb(II) and 48.5 mg g--1 for Cu(II) in monocomponent systems, while in bicomponent systems were 88.3 and 49.5 mg g--1, respectively. The results revealed that the as prepared chitosan-based magnetic adsorbent can be an effective and promising adsorbent for Pb(II) and Cu(II) from mono and bicomponent aqueous solutions.

Multi-component mathematical model based on mass transfer coefficients for prediction of the Zn and Cd ions biosorption data by E. densa in a continuous system

The objective of this study was to evaluate the biosorption dynamics of heavy metals by the dead macrophyte Egeria densa in fixed bed column. Experiments were conducted with mono- and bi-component solutions of Cd(II) and Zn(II) at pH 4.0, temperature of 30 °C and volumetric flow rate range between 2 and 6 cm3 min−1. A mass transfer mathematical model was applied for describing the mono-component biosorption dynamics. In this model, the equilibrium was represented by the batch Langmuir isotherm, and intraparticle diffusion was considered as the rate-limiting step for the mass transfer. The mass transfer coefficient (KS) was estimated by the downhill simplex optimization method for each volumetric flow tested, while the axial dispersion coefficient was calculated by empirical correlations. The KS coefficients and the equilibrium parameters obtained in a mono-component batch system were validated using data from the breakthrough curves of the Cd(II) and Zn(II) binary mixture obtained for different volumetric flows and initial concentrations of each metal ion.

Application of coconut shell, banana peel, spent coffee grounds, eucalyptus bark, piassava (Attalea funifera) and water hyacinth (Eichornia crassipes) in the adsorption of Pb2+ and Ni2+ ions in water

In this study, six residual plant materials were tested as adsorbents to remove Pb2+ and Ni2+ ions from water. The influence of variables such as PH, contact time and adsorption isotherms parameters in adsorption process was studied. The assessment of compatibility with cement of the used contaminated adsorbents has also been performed. The concentration of the studied metal ions was determined by dispersive energy x-ray fluorescence spectrometry. In the studies of pH and kinetics, it was verified that Pb2+ ions were more adsorbed than the Ni2+ ions. The highest values for adsorption capacity were found at pH equal to 4.5 for Pb2+, and at pH equal to 5 for Ni2+ .The adsorption kinetics were fitted to the pseudo-second order model for the both metals. The Langmuir isotherm allowed to estimate the adsorption capacity of the materials for mono and bicomponent solutions, which were superior to those observed in literature. A new proposal for the final destination of the used adsorbents contaminated with metal ions, proved to be a viable alternative for its immobilization.

Uranium and europium sorption on amidoxime-functionalized magnetic chitosan micro-particles

Magnetic chitosan particles were successfully modified by amidoxime-grafting (as evidenced by FTIR analysis, SEM-EDX analysis, elemental analysis, X-ray diffraction (XRD), thermogravimetric analysis and titration). The effect of pH was investigated showing optimum sorption at pH 4 for U(VI) and pH 5 for Eu(III). Uptake kinetics are relatively fast: the equilibrium was reached within 60–90 min; and the kinetic profiles were preferentially fitted by the pseudo-second order rate equation. Sorption isotherms are equally fitted by the Langmuir and the Sips equations; under optimal conditions maximum sorption capacity reaches 1.5 mmol U g−1 and 2.47 mmol Eu g−1. In bi-component solution, at pH close to 4.9, uranyl is enriched on the sorbent (higher selectivity coefficient) while maintaining high sorption capacities. The selectivity for Eu(III) sorption is higher at pH 2.3 but at the expense of a decrease in sorption capacities. Metal ions can be readily and fast desorbed using 0.5 M HCl solutions: 30–90 min are sufficient for achieving the complete desorption of U(VI) and about 95% of Eu(III) desorption. Sorption and desorption performances are maintained almost constant over 5 cycles of sorption/desorption: the sorbent can be efficiently recycled. Uranium was successfully recovered from alkaline leachate of a sedimentary dolostone ore material.

Competitive adsorption characteristics of rhenium in single and binary (Re-Mo) systems using Purolite A170

In this study adsorption of rhenium ions from single and bi-component solutions (Re-Mo) by Purolite A170 was studied experimentally and described by isotherm, kinetic and thermodynamic modeling. Considering coefficient of determination (R2) and values of root mean squared error (RMSE) for the multicomponent isotherms, the extended model of Freundlich isotherm was found to be successful. Moreover, fitting the time-dependent data into different mechanisms showed that the data comply well with the pseudo-second order model. Results from the binary systems demonstrated that the presence of the secondary metal ions in the system causes a decrease in the adsorption capacity of rhenium, which is mainly due to the competitive effects of metals for adsorption sites. Furthermore, evaluation of thermodynamic parameters showed that the reaction mechanisms are different for both systems; however, due to negative values of ΔH, in competitive condition the adsorption of rhenium becomes more feasible with increasing the temperature.

Behavior of Ni(II) and Mn(II) in single and binary aqueous solutions in the adsorption process by rice hull ashes (RHA)

ABSTRACTThe retention of nickel and manganese by calcined rice hull ashes (RHA) in single and binary solutions was determined as a function of metal concentration and time. The maximum adsorptions of RHA for Ni(II) and Mn(II) were 7.27 and 6.45 mg/g from monocomponent solutions, and 4.6 and 3.8 mg/g from bicomponent solutions, respectively. The kinetic experimental data best fit a pseudo-second-order model. The k2 is higher for Mn(II) than Ni(II) considering the monocomponent solutions and this parameter is similar between them if the bicomponent solution is considered. The metallic species were partially desorbed from RHA by water.

Functionalized biogenic hydroxyapatite with 5-aminosalicylic acid – Sorbent for efficient separation of Pb2+ and Cu2+ ions

The biogenic hydroxyapatite (BHAP), obtained by proper treatment of bovine bones, was functionalized with 5-aminosalicylic acid (5-ASA). The coordination of 5-ASA to the surface of BHAP leads to the charge transfer (CT) complex formation accompanied with absorption in visible spectral range. The sorption ability of surface-modified BHAP with 5-ASA (5-ASA/BHAP) for removal of Pb2+ and Cu2+ ions from single- and bi-component solutions was compared with unmodified BHAP. The thorough characterization of both sorbents, BHAP and 5-ASA/BHAP, was performed including X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), nitrogen adsorption-desorption isotherms, as well as diffuse reflection spectroscopy. Sorption kinetics and equilibriums for both ions (Pb2+ and Cu2+) by as-prepared BHAP and 5-ASA/BHAP are quite different. Functionalized sorbent demonstrated faster sorption kinetic and higher maximum sorption capacity for Pb2+ ions from bi-component solutions. From equimolar Pb2+ and Cu2+ mixture with a total concentration of 10−2mol/L, 66% of Pb2+ was recovered using BHAP, while 97% using 5-ASA/BHAP. These preliminary data indicate potential applicability of properly functionalized hydroxyapatite for selective removal of heavy metal ions from contaminated water.

Single and competitive adsorption of OMPs by carbon nanotubes – mechanism and fitting models

The adsorption of three organic micropollutants (diclofenac – DFN, pentachlorophenol – PCP and octylphenol – OP) on two kinds of carbon nanotubes (single walled carbon nanotubes – SWCNT and single walled carbon nanotubes with amine group – SWCNT-NH 2 ) was investigated, in single and bicomponent solution at pH 5. SWCNT-NH 2 had three times lower specific surface area than SWCNT. Significant differences were observed in sorption capacity of SWCNT and SWCNT-NH 2 for given chemicals. The sorption uptake changes in the following order: OP > PCP > DFN for SWCNT and DFN > PCP > OP for SWCNT-NH 2 . A few times higher adsorption of OP on SWCNT came from low OP solubility in water in comparison to PCP and DFN. While, higher adsorption of DFN and PCP on SWCNT-NH 2 was a result of electrostatic attraction between dissociated form of these chemicals and positively charged SWCNT-NH 2 at pH 5. In adsorption from bicomponent solution, significant competition was observed between PCP and DFN due to similar adsorption mechanism on SWCNT-NH 2 . Opposite tendency was observed for SWCNT, DFN did not greatly affect adsorption of PCP and OP since they were very easily absorbable by sigma-sigma interaction.

Comparative and competitive adsorption of Pb(II) and Cu(II) using tetraethylenepentamine modified chitosan/CoFe2O4 particles

In this paper, tetraethylenepentamine (TEPA) modified chitosan/CoFe2O4 particles were prepared for comparative and competitive adsorption of Cu(II) and Pb(II) in single and bi-component aqueous solutions. The characteristics results of SEM, FTIR and XRD indicated that the adsorbent was successfully fabricated. The magnetic property results manifested that the particles with saturation magnetization value of 63.83emug−1 would have a fast magnetic response. The effects of experimental parameters including contact time, pH value, initial metal ions concentration and coexisting ions on single and bi-component adsorption were investigated. The results revealed that the adsorption kinetic was followed pseudo-second-order kinetic model, indicating that chemical adsorption was the rate-limiting step. Sorption isotherms were also determined in single and bi-component solutions with different mass ratio of Cu(II) to Pb(II) (Cu(II)/Pb(II)) and fitted using Langmuir and Freundlich isotherm models. A better fit for Cu(II) and Pb(II) adsorption were obtained with Langmuir model, with a maximum sorption capacity of 168.067 and 228.311mgg−1 for Cu(II) and Pb(II) in single component solution, 139.860 and 160.256mgg−1 in bi-component solution (Cu(II)/Pb(II)=1:1), respectively. The present results suggest that TEPA modified chitosan/CoFe2O4 particles are feasible and satisfactory adsorbent for efficient removal of Cu(II) and Pb(II) ions.