Binary Ion Systems Research Articles

Pit-lake remediation by chemically activated Chlorocardium rodiei: Simultaneous metal ion removal from acidic waters

The current study investigates the valorization of waste wood from a tropical hardwood found in Guyana (Greenheart – Chlorocardium rodiei) to high surface area activated carbons (AC). We subsequently deployed these adsorbents to sequester Mn 2+, Fe3+, and Al3+ from the acidic waters of a recreational bauxite pit-lake. We studied the impact of activation parameters such as temperature, impregnation ratio and acid concentration on the texture and surface chemistry of ACs and demonstrate that optimized low pH at point-of-zero charge (pHpzc) ACs are efficient adsorbents for the target ions. A mesoporous AC with specific surface area of 2208 m2/g, 11 % surface oxygen and pHpzc of 1.98 was produced under optimized conditions. ACs removed 93–100 % of target ions from pit-lake waters at a native pH of 3.1. Al3+ exerted an antagonistic effect on Mn2+ adsorption in synthetic binary ion systems reducing adsorption by as much as 56 %. The Sips Model fitted the adsorption data best predicting maximum adsorption capacities for Mn2+, Fe3+ and Al3+ of 17.8 mg/g, 23.7 mg/g, and 6.12 mg/g for these low pHpzc optimized materials. These materials show great promise in removing heavy metals from acidic waters.

Synthesis of -thiazole Schiff base modified SBA-15 mesoporous silica for selective Pb(II) adsorption

BackgroundThe selective removal of Pb(II) ions is meaningful not only to the waste water treatment but also the lead recycling. MethodsIn this study, two kinds of thiazole Schiff base modified mesoporous silica, SBA-NS, SBA-ENS, were prepared by modifying SBA-15 with aminopropyl and [2-aminoethylamino]-propyl groups, respectively, and then followed by Schiff condensation with 2-aldehyde-thiazole. The effects of pH, time, ions concentration, and temperature on the Pb(II) adsorption performance were investigated. Significant FindingsThe kinetics analysis and adsorption isotherms revealed that the overall Pb(II) adsorption process by the two adsorbents was more consistent with the pseudo-second-order kinetic model and Langmuir isotherm model. The thermodynamic parameters showed spontaneous and exothermic Pb(II) adsorption nature onto SBA-NS and SBA-ENS. Compared with amino modified silica precursors, SBA-NS and SBA-ENS exhibited improved adsorption selectivity for Pb(II) in binary metal ion systems with co-existing cations. Besides, the adsorption behavior is not affected by the ionic strength, and the adsorbents can be easily reused without significant loss in of Pb(II) removal efficiency. The density functional theory method demonstrated that the imine N atoms on the two adsorbents played a dominant role during the Pb(II) sorption process.

Preparation of bifunctional polysilsesquioxane/carbon nanotube magnetic composites and their adsorption properties for Au (III)

Bifunctional polysilsesquioxane/carbon nanotube magnetic composites were prepared by coating the polysilsesquioxane with amino and thiol groups on carboxyl carbon nanotubes (CNTs-COOH) embedded with magnetic ferroferric oxide (Fe3O4). The morphology and physicochemical properties of the composites were characterized by FT-IR, SEM, VSM, XRD, XPS and BET, and the adsorption capacities of these composites for Au(III) was investigated systematically. The thermodynamic adsorption curves conform to the Langmuir model, and the kinetics curves can be fitted to the pseudo-second-order model. The adsorption capacities of the composites for Au(III) at 35 ℃ varied from 2.01 mmol/g to 2.82 mmol/g according to the Langmuir model. Selective adsorption tests showed that the bifunctional composites could selectively adsorb Au(III) in a number of binary metal ions systems. It is expected that the bifunctional polysilsesquioxane/carbon nanotube magnetic composites can be used to recover low concentration Au(III) from waste water.

Synthesis of rare earth metal oxide nanoparticle for simultaneous removal of fluoride and As(III) from aqueous solution

This study aims to investigate the sorption behavior of As(III) in presence of fluoride ion in an aqueous solution. Conventionally the As(III) is removed by converting it to As(V) with certain oxidants followed by sorption or precipitation. Limited information is available for As(III) sorption in presence of fluoride ions. The present study deals with single-step sorption of As(III) in the absence and presence of fluoride ion with rare earth metal oxide as adsorbent. The nanoparticles of CeO2 were synthesized by a low-temperature chemical precipitation method. The CeO2 as adsorbent is tested for sorption of As(III) and fluoride in a single system. The solution pH has a significant role in the sorption of fluoride ion however, negligible effect on As(III) sorption in the pH range of 4–8. The adsorbent showed the significant uptake capacity for arsenic and fluoride even in binary ion systems as 81.9 F mg/g and 3.3 As(III) mg/g respectively. The spent adsorbent is efficiently reused for ion sorption after regeneration and activation.

A novel route for the removal of Cu(II) and Ni(II) ions via homogeneous adsorption by chitosan solution

Abstract An easy and efficient homogeneous adsorption of chitosan for metal ions in a single and binary metal ion systems was investigated. The chitosan solution was firstly mixed into the metal ion solution to quickly chelate metal ions. Then chitosan-metal ion nanoparticles were formed when sodium phytate was added into mixed solution and finally separated by centrifugation. The homogeneous adsorption properties of chitosan for Cu(II) and Ni(II) ions under different adsorption conditions were investigated in detail. The adsorption of Cu(II) and Ni(II) followed the Langmuir model and the pseudo-second order kinetic model. The maximum adsorption capacities for Cu(II) and Ni(II) ions, were 405 and 315 mg/g, respectively, initial concentration 1000 mg/L of Cu(II) or Ni(II) ions, pH 5.2, and temperature 30 °C. These values were five and eight times as much as pure chitosan resin reported, showing a high performance/price ratio although no regeneration. Phosphorus atoms were not determined in the liquid supernatant by ICP though addition of sodium phytate, suggesting no secondary pollution occurred after addition of sodium phytate. These results demonstrated that the homogeneous adsorption of chitosan solution for metal ions was a promising clear production process.

Use of apple seeds as new source for synthesis of polyacrylonitrile-based adsorbent to remove Pb(II)

Bromoactylated apple seeds (BAS) was used as new source for the synthesis of environmental adsorbent. Apple seeds were modified by bromoacetyl bromide to obtain a macroinitiator for single electron transfer-living radical polymerization (SET-LRP) of acrylonitrile (AN). The amidoxime (AO) adsorbent was prepared by the reaction of the graft copolymer bromoactylated apple seeds (BAS)/polyacrylonitrile (BAS-g-PAN) with hydroxylamine. Amidoxime BAS-g-PAN (AO BAS-g-PAN) was used to remove Pb(II) and the maximum adsorption for Pb(II) was 1.58 mmol/g. AO BAS-g-PAN could also selectively adsorb Pb(II) from binary ion systems in the existence of Ag(I), Ni(II) and Zn(II). This efficient modifying approach provides a new powerful mean toward filling the gap on apple waste as a potential source for controlling heavy metal pollution.

Selective adsorption of Pb(II) from aqueous solution using porous biosilica extracted from marine diatom biomass: Properties and mechanism

Biosilica with a surface area of 143m2g−1 derived from marine diatoms was prepared using an easy two-step method involving washing with dilute acid and baking. The extracted biosilica was used to remove divalent lead ions, i.e., Pb(II), from aqueous solution. The effects on Pb(II) adsorption of initial pH, shaking speed, and adsorbent loading were investigated. The adsorption of Pb(II) in the presence of other ions was also investigated. The biosilica showed a high adsorption capacity with high selectivity for Pb(II). The experimental maximum adsorption capacity was 108.2–120.4mgg−1 at an adsorbent loading of 1gL−1. The adsorption process was best described by the Langmuir model. The adsorbent selectively adsorbed Pb(II) from binary ion systems in the presence of Cu(II), Cd(II), Ni(II), and Ag(I). The results of this study show that biosilica extracted from fresh marine diatoms is a more efficient and selective adsorbent for Pb(II) than other inorganic adsorbents.

Removal of Cr(VI) and Hg(II) ions from wastewater by novel β-CD/MGO-SO3H composite

A novel magnetic adsorbent β-CD/MGO-SO3H with excellent hydrophilicity and high adsorption capacity was developed for removal of Cr(VI) and Hg(II) ions from wastewater. The adsorbent was characterized by transmission electron microscopy, X-ray diffraction and vibrating sample magnetometer. The kinetic adsorption test showed that the adsorptions of Cr(VI) and Hg(II) ions on the adsorbent fitted well with the pseudo-second order kinetics. The adsorption isotherms indicated that the adsorptions of Hg(II) and Cr(II) followed the Langmuir and the Freundlich models in single metal ion systems, respectively, while in binary metal ion systems they all followed the Langmuir model. The thermodynamic parameters revealed that the adsorption process was spontaneous and endothermic. Results showed that the as-prepared β-CD/MGO-SO3H composite could be utilized as an efficient and magnetically separable adsorbent for Cr(II) and Hg(II) in wastewater.

Adsorption of lead and copper on bentonite and grapeseed activated carbon in single- and binary-ion systems

ABSTRACTIn this study, bentonite originating from Turkey (Eskişehir province) and activated carbon obtained from grapeseed were used as adsorbents for the removal of lead (Pb2+) and copper (Cu2+) ions from aqueous solutions. Experiments were performed in single- and binary-ion systems at constant temperature of 298 K and pH value of 5. In order to describe the adsorption mechanism Langmuir, Freundlich and Temkin isotherms were used. The total adsorption capacity values of adsorbents were compared. It was observed that the total adsorption capacity values were changed depending on the type of adsorbent used, type of metal ion and interaction between metal ions.

Competitive adsorption of magnesium and calcium with phosphate at the goethite water interface: Kinetics, equilibrium and CD-MUSIC modeling

In natural environments, competitive interactions of ions with charged particles often control bioavailability and mobility of ions. In these systems, chemical reactions are often in a semi-equilibrium state; thus, along with equilibrium data, kinetic data are of great importance in predicting ion bioavailability and mobility. Therefore, in this research, kinetics and equilibrium adsorption interactions of magnesium, calcium and phosphate on goethite are investigated as a function of time, pH, ion loading and ionic strength in single and binary ion systems. The thermodynamically valid model parameters, obtained from single ion systems by applying the CD-MUSIC model, are used to predict ion interactions in more complex systems, i.e. binary ion systems. Results indicate that the kinetics of phosphate and magnesium adsorption is pH-dependent and electrostatic attractive and repulsive forces dominantly control the reaction. Thus, adsorption of magnesium and calcium influences significantly both the amount of adsorbed phosphate and the reaction time, and vice versa. Therefore, the equilibration time for phosphate and magnesium adsorption on goethite is approximately ≤1h when electrostatic forces are attractive and approximately 24h when electrostatic forces are repulsive. Variation in ionic strength (0.01–0.3M NaCl) has no significant effect on the magnesium and calcium adsorption, suggesting a large difference in the adsorption energy of Ca and Mg compared to Na, which is very likely due to the difference in their adsorption mechanism. Based on the model calculations, formation of two inner sphere surface complexes, as (FeOH)2Mg and (FeOH)2MgOH, is the dominant mechanism for magnesium adsorption. For calcium, however, a monodentate outer sphere surface complex dominates its adsorption at acid pH range and a monodentate inner sphere complex at basic pH range (FeOHCa). This difference results in a different amount of charge on electrostatic planes that influences strongly phosphate adsorption such that phosphate adsorption is significantly higher in Ca–PO4 systems than in Mg–PO4 systems.

Facile synthesis of PVA/CNTs for enhanced adsorption of Pb2+ and Cu2+ in single and binary system

Multiwall carbon nanotubes (CNTs) were entrapped into polymer matrix by poly(vinyl alcohol) (PVA)-boric acid crosslinking. Thus, a novel macroporous composite adsorbent (PVA/CNTs) was obtained and used to remove heavy metal ions. Compared with CNTs, PVA/CNTs could effectively adsorb Pb2+ and Cu2+ from binary ion systems in the existence of HA, Zn2+, Cd2+, Ca2+, and surfactant, respectively. The results indicated that sorption of Pb2+ and Cu2+ on PVA/CNTs was strongly dependent on pH values, and independent of ionic strength. PVA/CNTs beads exhibited special selectivity for Pb2+ ions in the presence of NaCl, anionic surfactant, and coexisting ions. The kinetic sorption can be described using a pseudo-second-order model very well. Chemical reaction such as surface complexation was the main sorption mechanism. The results from the sequential adsorption–desorption cycles showed that PVA/CNTs beads exhibited good desorption and reusability. The PVA/CNTs beads were prepared by a simple way and they are easily recovered from aqueous solution and efficiently regenerated. PVA/CNTs could be a promising alternative to activated carbon for wastewater treatment.

Competitive adsorption-desorption reactions of two hazardous heavy metals in contaminated soils.

Investigating the interactions of heavy metals is imperative for sustaining environment and human health. Among those, Cd is toxic for organisms at any concentration. While Ni acts as a micronutrient at very low concentration but is hazardous toxic above certain threshold value. In this study, the chemical adsorption and desorption reactions of Ni and Cd in contaminated soils were investigated in both single and binary ion systems. Both Ni and Cd experimental data demonstrated Langmuir type adsorption. In the competitive systems, an antagonistic effect was observed, implying that both ions compete for same type of adsorption sites. Adverse effect of Cd on Ni adsorption was slightly stronger than that of opposite system, consistent with adsorption isotherms in single ion systems. Variation in ionic strength indicated that Ca, a much weaker adsorbate, could also compete with Cd and Ni for adsorption on soil particles. Desorption data indicated that Cd and Ni are adsorbed very tightly such that after four successive desorption steps, less than 0.5% of initially adsorbed ions released into the soil solution. This implies that Ca, at concentration in equilibrium with calcite mineral, cannot adequately compete with and replace adsorbed Ni and Cd ions. This adsorption behavior was led to considerable hysteresis between adsorption and desorption in both single and binary ion systems. In the binary ion systems, desorption of Cd and Ni was increased by increase in both equilibrium concentration of adsorbed ion and concentration of competitor ion. The overall results obtained in this research indicate that Cd and Ni are strongly adsorbed in calcareous soil and Ca, the major dissolved ion, insignificantly influences metal ions adsorption. Consequently, the contaminated soils by Ni and Cd can simultaneously be remediated by environmentally oriented technologies such as phytoremediation.

Comparison of Experimental and Simulated Adsorption of Binary Metal Ions using Sawdust Modified by Citric Acid

With the aim of removing binary metal ions from aqueous solutions, the adsorption characteristics of sawdust modified with citric acid are investigated using adsorption kinetics and isotherms in both an experiment and a numerical simulation. The adsorption of metal ions is characterized by the competitive adsorption in binary metal ion systems that results from the stability constants between metal ions and citrate in the modified sawdust. These findings suggest that competitive adsorption and the affinities of the metal ion adsorbents play important roles in the removal of metal ions and that the numerical simulation can predict the adsorption characteristics of the modified sawdust.

Cost Effective Adsorption of Aluminium and Iron from Synthetic and Real Wastewater by Rice Hull Activated Carbon (RHAC)

The adsorption of aluminium(III) and iron(III) ions from their single and binary systems, by RHAC was investigated in a batch system. The activated carbon prepared from rice hulls was characterized by scanning electron microscopy and Fourier transformation infrared techniques. Batch adsorption experiments were performed under different operating conditions including pH (2 - 5), adsorbent dosage (0.5 - 2.0 g/l), initial ion concentration (5 - 100 mg/l), and contact time (30 - 240 min). The equilibrium time for maximum ions removal was found to be 180 min in single and binary ions systems. The kinetics of adsorption was evaluated using the pseudo-first order, pseudo-second order and Elovich kinetic models. The Langmuir, Freundlich and Temkin equilibrium models were applied to the adsorption experimental data. Real wastewater samples were collected from different locations to investigate the efficiency of rice hull activated carbon in treating real samples. The real wastewater samples were treated with the activated carbon prepared from rice hulls and a commercial activated carbon. The results showed that the activated carbon prepared in the present work was more efficient in the removal of aluminium and iron from real wastewater as compared to the commercial activated carbon which is more advantageous considering both economics and environmental parameters.

High-performance towards Cr(VI) removal using multi-active sites of polypyrrole–graphene oxide nanocomposites: Batch and column studies

Hexavalent chromium [Cr(VI)] adsorption onto polypyrrole graphene oxide nanocomposite (PPy–GO NC) From aqueous solutions was explored using batch and packed-bed column modes. The performance of the PPy–GO NC for Cr(VI) removal was evaluated as a function of solution pH, initial Cr(VI) concentration, temperature, bed mass and time. The characterization of PPy–GO NC using HR-TEM, FE-SEM and Raman spectroscopy confirmed that graphite was successfully exfoliated to thin layered graphene sheets and also ensured the presence of the PPy in the PPy–GO NC. Meanwhile the zeta potential data showed that the point of zero charge of the nanocomposite was at pH 6.2. Batch sorption isotherm data at optimum solution pH of 2, was satisfactorily described by the Langmuir isotherm model with a maximum sorption capacity of 625mg/g at 25°C, while the kinetic data fitted well with the pseudo second order kinetic model. Sorption of Cr(VI) onto PPy–GO NC in binary ions systems was also evaluated and results showed that the presence of co-existing ions had no effect on Cr(VI) removal. Expressed through breakthrough curves, the packed-bed Cr(VI) sorption data showed consistency with the ideal s-shape. Moreover, a large volume of Cr(VI) contaminated water (64.08L) was successfully treated to below allowable discharge limit at low influent Cr(VI) concentration (10mg/L) using 2g of PPy–GO NC at a flow rate of 3mL/min. Breakthrough data were successfully described by the Thomas and Yoon–Nelson models.

Preparation of Wheat Straw Matrix-g-Polyacrylonitrile-Based Adsorbent by SET-LRP and Its Applications for Heavy Metal Ion Removal

Polyacrylonitrile (PAN) was grafted onto the surface of a wheat straw matrix (WSM) by single-electron transfer-living radical polymerization (SET-LRP). A novel agricultural residue adsorbent amidoxime WSM-g-PAN (AO WSM-g-PAN) was obtained by modifying WSM-g-PAN with hydroxylamine hydrochloride (NH2OH·HCl). AO WSM-g-PAN was used to remove heavy metal ions. Compared with WSM, the adsorption capacity of AO WSM-g-PAN for Hg(II) increased greatly, and the maximum adsorption capacity was 4.7 mmol g–1. AO WSM-g-PAN could effectively adsorb Hg(II) from binary ion systems in the existence of Ni(II), Pb(II), Cu(II), Zn(II), and Ag(I).

Thiol-functionalized polysilsesquioxane as efficient adsorbent for adsorption of Hg(II) and Mn(II) from aqueous solution

Thiol-functionalized polysilsesquioxane was synthesized and used for the adsorption of Hg(II) and Mn(II) from aqueous solution. Results showed that the optimal pH was about 6 and 5 for Hg(II) and Mn(II), respectively. Adsorption kinetics showed that the adsorption equilibriums were established within 100min and followed pseudo-second-order model. Adsorption isotherms revealed that the adsorption capacities increased with the increasing of temperature. The adsorption was found to be well described by the monolayer Langmuir isotherm model and took place by chemical ion-exchange mechanism. The thermodynamic properties indicated the adsorption processes were spontaneous and endothermic nature. Selectively adsorption showed that PMPSQ can selectively adsorb Hg(II) from binary ion systems in the presence of the coexistent ions Mn(II), Cu(II), Pb(II), Co(II), and Ni(II). Based on the results, it is concluded that PMPSQ had comparable high adsorption efficiency and could be potentially used for the removal of Hg(II) and Mn(II) from aqueous solution.

Ionic Imprinted Silica-Supported Hybrid Sorbent with an Anchored Chelating Schiff Base for Selective Removal of Cadmium(II) Ions from Aqueous Media

A novel Cd(II)-ion-imprinted silica-supported hybrid sorbent functionalized with tetradentate Schiff bases ligands derived from 2-thiophenecarboxaldehyde and 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane for the selective removal of Cd(II) ions from aqueous media had been synthesized by a surface-imprinting technique in conjunction with a sol–gel process and characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, N2 adsorption–desorption isotherms, and thermogravimetric analysis. The results revealed that the static adsorption capacity of Cd(II) was 29.1 mg·g–1. The imprinted hybrid sorbent exhibited a fast equilibrium time with 30 min, had a stable binding capacity in the range of pH 3.5–9.5, and showed the selective adsorption for Cd(II) in binary ions systems of Cd(II)/Zn(II), Cd(II)/Ni(II), Cd(II)/Cu(II), and Cd(II)/Pb(II). The adsorption/desorption cycles of the imprinted hybrid sorbent could be up to nine times. Langmuir, Freundlich, and Dubinin–Radushkevich isotherm models were applied to analyze the experimental data, and the best interpretation for the experimental data was given by the Langmuir isotherm equation. The adsorption kinetics could be fitted by pseudo-second-order rate equation wonderfully compared with pseudo-first-order, Elovich, and intraparticle diffusion models. Negative values of ΔG° indicated the spontaneous adsorption, and the degree of the spontaneity increased with increasing temperature. The thermodynamic parameters of ΔH° and ΔS° were 11.77 kJ·mol–1 and 74.98 J·K–1·mol–1, respectively. Thus, this novel imprinted hybrid sorbent was a favorable, useful, and promising good candidate material for the selective removal of Cd(II) ions from aqueous media.

Breakthrough studies with mono-, binary- and ternary-ion systems comprised of Fe(II), F− and As(III) using river sand packed columns for groundwater treatment

Groundwater in Assam, India, contains excessive amounts of arsenic (As(III)), fluoride (F(-)) and iron (Fe(II)). The rural and semi-urban population of Assam uses indigenous iron filters fabricated using processed sand (PS) as one of the chief constituents to reduce Fe(II) concentration; however, no efforts have been made to reduce As(III) or F(-) concentrations before use. The present work is directed towards assessing the potential of PS for removal of these ions from mono-, binary- and ternary-ion systems through continuous mode column studies. Synthetic water samples containing fixed concentration of ions were prepared using deionized water. The observed order of breakthrough of ions was: As(III) followed by Fe(II) and F(-) followed by Fe(II) in the case of the binary ion systems of Fe(II) + As(III) and Fe(II) + F(-). The throughput volume for As(III) in the (Fe(II) + As(III)) system and for F(-) in the (Fe(II) + F(-)) system is termed the critical breakthrough throughput volume. In the ternary ion system (Fe(II) + As(III) + F(-)), the order of breakthrough of ions observed was F(-), then As(III) and then Fe(II) and hence the throughput volume F(-) is termed the critical breakthrough throughput volume. Results of column studies also indicate the impact on the uptake of the selected ion by the presence of the other ion present in the binary- and ternary-ion systems.

Adsorption of Pb(II) from aqueous solution by silica-gel supported hyperbranched polyamidoamine dendrimers

The adsorption properties of silica-gel supported hyperbranched polyamidoamine dendrimers (SiO2-G0–SiO2-G4.0) have been investigated by batch method. The effect of pH of the solution, contact time, initial Pb(II) ion concentration, temperature and coexisting metal ions have been demonstrated. The results indicated that the optimum pH value was 5. Adsorption kinetics was found to follow the pseudo-second-order model and controlled by film diffusion. The adsorption isotherms were fitted by Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherm models. Langmuir isotherm model was found to be more suitable to describe the equilibrium data, suggesting the uptake of Pb(II) ions by monolayer adsorption. From D–R isotherm model, the calculated mean free energy E demonstrated the adsorption processes occurred by chemical ion-exchange mechanism. FTIR analysis revealed that amine groups were mainly responsible for the adsorption of Pb(II) by amino-terminated adsorbents, while CO of ester groups also participated in the adsorption process of ester-terminated ones. The adsorbents can selectively adsorb Pb(II) from binary ion systems in the presence of Mn(II), Cu(II), Co(II), and Ni(II). Based on the results, it is concluded that SiO2-G0–SiO2-G4.0 had great potential for the removal of Pb(II) from aqueous solution.