Adsorption Characteristics Of Metal Ions Research Articles

Sulfide modifies physicochemical properties and mercury adsorption of microplastics

Microplastics (MPs) tend to accumulate and undergo a sulfur weathering process that leads to significant surface changes in sulfur-rich anaerobic environments, such as sewage and wastewater treatment plants. Aged MPs can have a profound impact on environmental behaviors of various toxic pollutants, especially heavy metals. Although previous studies have investigated the adsorption characteristics of metal ions on MPs that are aged in aerobic environments, the sorptive interactions of sulfur-aged MPs in anaerobic environments with mercury, i.e., Hg(II), are largely unknown. In this study, laboratory investigations were conducted to study the sorptive behaviors of Hg(II) by six common MPs treated anaerobically in the presence of sulfide. Adsorption isotherms show that the sulfur aging process greatly enhances the MP sorption capacity of Hg(II). The mechanisms including changes in the specific surface area, electrostatic interactions, surface precipitation, and surface functional groups are responsible for the enhanced adsorption capacities of sulfur-aged MPs. The thiol group that forms on the MP surface plays a dominant role in enhancing the MP adsorption capacity of Hg(II), which is determined by the formation of unsaturated bonds in the molecular chains of MPs. Furthermore, the pathways of surface chemical transformation of MPs during sulfur aging have been proposed. This study promotes our understanding of the potential hazard of MPs as well as the fate and transport of heavy metals in the presence of aged MPs.

Adsorption of Metallic Ions on Amidoxime-Chitosan/Cellulose Hydrogels

Adsorption using natural compounds is an attractive separation technique for recovering heavy metals from aqueous media. Although chitosan, which is a natural polysaccharide, is an environmentally benign adsorbent, it dissolves in an acidic aqueous medium. In this study, we prepared adsorbents consisting of chitosan modified with amidoxime groups for improving metal adsorptivity, and cellulose for improving gel stability using an ionic liquid, and examined their adsorption characteristics for metal ions. The prepared amidoxime-chitosan/cellulose hydrogels had a mechanical strength without cross-linking. All the investigated metals were adsorbed on the amidoxime-chitosan/cellulose hydrogels in the following adsorptivity order: Cu ≈ Ag > Ni > Zn. The adsorptivity of the metal ions increased with pH due to a proton exchange reaction. From the Langmuir adsorption isotherm, the Langmuir constant for Cu exceeded those of other metals because amidoxime has higher Cu affinity. The pseudo-second-order reaction model best described the adsorption kinetics with metal chelate formation being the rate-determining step. Because amidoxime-chitosan/cellulose hydrogels had higher physical stability and higher Cu selectivity, they were found to be a promising, environmentally benign adsorbent.

Adsorption mechanism of cadmium on microplastics and their desorption behavior in sediment and gut environments: The roles of water pH, lead ions, natural organic matter and phenanthrene

Microplastics (MPs) in aquatic systems can act as a vector for various toxic contaminants, such as metal ions. Although some studies have investigated the adsorption characteristics of metal ions on MPs, the desorption behaviors of metal ions from MPs in different environments are largely unknown. Here, the adsorption of cadmium (Cd(II)) onto five different types of MPs were compared to examine the relationship between the surface characteristics and the adsorption properties of MPs. Our results showed that polyamide had the highest Cd(II) adsorption capability with a value of 1.70 ± 0.04 mg/g, followed by polyvinyl chloride (1.04 ± 0.03 mg/g), polystyrene (0.76 ± 0.02 mg/g), acrylonitrile butadiene styrene (0.65 ± 0.02 mg/g) and polyethylene terephthalate (0.25 ± 0.01 mg/g). The specific surface area and total pore volume were closely correlated with the adsorption capacity of the MPs, and the π–π interaction, electrostatic interaction and oxygen-containing functional groups played crucial roles in the adsorption of Cd(II) onto the MPs. The sorption capabilities of Cd(II) onto the MPs first increased and then decreased with increasing solution pH from 2.0 to 9.0. In addition, the adsorption capacities were suppressed with the presence of lead ions (20–80 mg/L), while the coexistence of phenanthrene had a minor impact. Interestingly, the presence of humic acid promoted the desorption of Cd(II) from the MPs both in the synthetic earthworm gut and in the sediment system. A higher desorption rate was observed in the simulated gut environment, suggesting that metal-contaminated MPs would pose higher ecological risks to macroinvertebrates. Overall, our findings provide a better understanding of the sorption mechanism of Cd(II) onto MPs and the desorption behavior under different environmental conditions in aquatic ecosystems.

Adsorption characteristics of white pottery clay towards Pb(II), Cu(II), and Cd(II)

The adsorption characteristics of metal ions in unitary (Pb(II), Cu(II), and Cd(II)); binary (Pb(II)-Cu(II), Pb(II)-Cd(II), and Cu(II)-Cd(II)); and ternary (Pb(II)-Cu(II)-Cd(II)) systems in white pottery clay were investigated. The influence of the white pottery clay content, pH value, and ion strength on Pb(II) adsorption was analyzed, and the kinetic and isothermal equilibrium adsorption characteristics of Pb(II), Cu(II), and Cd(II) are discussed. The results showed that the adsorption reactions of white pottery clay for Pb(II), Cu(II), and Cd(II) are all rapid reactions that reach equilibrium in 180 min. The pseudo-second-order kinetic model fits the experimental results well. The Langmuir model can accurately predict the isothermal adsorption process of Pb(II), Cu(II), and Cd(II), and the monolayer maximum adsorption capacity of white pottery clay reached 159.236, 38.491, and 26.991 mg/L, respectively. Cu(II) can significantly inhibit the adsorption of Pb(II) on white pottery clay in the Pb(II)-Cu(II) binary system, and the inhibition effect is stronger at a higher Cu(II) concentration, while Cd(II) shows less of an inhibitory effect in the Pb(II)-Cd(II) binary system. The competitive adsorption effect superimposes in the Pb(II)-Cu(II)-Cd(II) ternary system, which results in a significant decrease in the capacity of white pottery clay to adsorb all three metals. Among them, the adsorption capacity of Pb(II) decreases with increasing Cu(II) and Cd(II) concentrations, whereas the adsorption of Cu(II) and Cd(II) is less affected by concentration changes of Pb(II).

Application of silver nanoparticles toward Co(II) and Pb(II) ions contaminant removal in groundwater

Applications of nanomaterials has recently been of keen interest to researchers.This fascinating drive ensued due to their unique properties such as optical, magnetic, ease of synthesis, large surface area, and tunable surface chemistry and functionalization that are remarkably different from that of the bulk material. In this work, silver nanoparticles were synthesized and characterized using UV–Vis spectroscopy and scanning electron microscopy. The UV–Vis spectra obtained showed absorption peak at 406 nm wavelength and scanning electron microscope reveals an image of size, 20 nm. The efficiency of our nanomaterial was first tested using standard solutions of cobalt and lead. A bathochromic shift in the absorption wavelength from 406 to 445 nm and from 406 to 458 nm for Cobalt(II) and Lead(II), respectively, indicates an adsorption has taken place. Adsorption characteristics of the nanoparticles evaluated at various incubation periods indicates a percent reduction in cobalt(II) from 33.13 to 53.34% and 79.9–92.92% for lead(II) from day 1–14. This indicates high removal efficiency for lead(II) than cobalt(II) in the proof of concept experiment. The results obtained further reveal that metal ion removal from complexes using silver nanoparticles is time-dependent. The effectiveness of our nanomaterial toward metal ion removal from groundwater was tested using inductively coupled plasma optical emission spectroscopy. The results obtained reveal removal efficiencies of 24% for cobalt and 77% for lead. It is important to note that metal ion concentrations reduced as the incubation periods increased. This is in line with the proof of concept experiment using complex solutions of cobalt and lead. Notably, the percent removal of cobalt was quite low compared to proof of concept experiment. These observations suggest a further research into understanding the adsorption characteristics of metal ions to the surface of nanomaterials in aqueous media.

Preparation and Performance Study on Sodalite/Magnetite from Tourmaline

Sodalite/Magnetite was efficiently fabricated by a one-step hydrothermal route using natural tourmaline as a silicon-aluminum source. The obtained products were characterized by X-ray diffraction, field emission scanning electron microscope, and elemental analysis (ICP) and N2 adsorption-desorption isotherm. In addition, the adsorption characteristics of metal ions (Cu2+, Co2+, Cr3+) on the sodalite were investigated. The results show that sodalite covered by octahedral particles of Fe3O4 was successfully obtained under hydrothermal treatment temperature at 300 °C. Nitrogen adsorption studies of sodalities showed the pore size around 0.7 nm and BET surface area over 0.315 m2/g. The adsorption capacities of Cu2+, Co2+and Cr3+ on sodalite/magnetite were 25.95, 8.90 and 4.1 mg/g.

Kinetics and Equilibrium Studies for the Removal of Cobalt, Manganese, and Silver in Ethanol using Dowex 50W-x8 Cation Exchange Resin

Organic solvents such as ethanol, find a wide range of applications in fuel, pharmaceutical industries, food industries, and paint formulations, among others. The removal of Ag(I), Co(II), and Mn(II) ions in ethanol by cation exchange resin, Dowex 50W-x8, was investigated. The adsorption characteristics of metal ions onto Dowex 50W-x8 resin were described by Langmuir isotherms. The maximum sorption exchange capacities at 298 K were obtained as 47.4 mg g−1, 52.6 mg g−1, and 58.5 mg g−1 for Ag(I), Co(II), and Mn(II), respectively. The data was also fitted to Temkin and Dubinin-Radushkevich adsorption isotherm models to evaluate other adsorption properties. The ion exchange of silver, cobalt, and manganese on cation exchange resin followed pseudo-second-order kinetics, and the intraparticle diffusion was rate-determining step. The thermodynamic parameters indicated that the sorption of metal ions onto Dowex 50W-x8 resin was spontaneous (negative ΔG°) and endothermic in nature (positive ΔH°) implying that the adsorption capacity increased with increasing temperature. The resin can be regenerated by eluting metal ions with 3.0 mol L−1 HNO3 followed by washing it with 10 mL of Millipore water and 10 mL of 2.0 M NaOH, respectively. The proposed method was applied for metal ion removal in real ethanol samples.

Synthesis of diethylaminoethyl dextran hydrogel and its heavy metal ion adsorption characteristics

Epichlorohydrin-crosslinked diethylaminoethyl dextran (DEAE-D/ECH) hydrogel was synthesized by intermolecular side-chain reaction of DEAE-D hydroxyl groups with monomeric crosslinking agent, ECH. Swelling ability, adsorption capacity and metal removal of the hydrogel were profoundly determined and some structural parameters for the hydrogel such as volume of non-swollen gel, percentages of gellation, swelling ratio and equilibrium water content were evaluated in this study.The ability of removing heavy metal ions from Orontes River by the synthesized hydrogel, thoroughly characterized by photometric spectrometer and the adsorption characteristics of metal ions, was investigated as well as surface morphologies of the hydrogel before and after metal adsorption were examined by SEM.Structure of DEAE-D/ECH gel was analyzed by FTIR, TGA, and DSC. Gellation point of binary system reaction between DEAE-D and ECH was determined via monitoring viscosity changes during reaction. The order of affinity based on amount of metal ion uptake was found as follows: Zn2+>Mn2+>Pb2+>Cd2+.

Adsorption characteristics of metal ions by CO 2-fixing Chlorella sp. HA-1

Single and binary metal systems were employed to investigate the removal characteristics of Pb 2+, Cu 2+, Cd 2+, and Zn 2+ by Chlorella sp. HA-1 that were isolated from a CO 2 fixation process. Adsorption test of single metal systems showed that the maximum metal uptakes were 0.767 mmol Pb 2+, 0.450 mmol Cd 2+, 0.334 mmol Cu 2+ and 0.389 mmol Zn 2+ per gram of dry cell. In the binary metal systems, the metal ions on Chlorella sp. HA-1 were adsorbed selectively according to their adsorption characteristics. Pb 2+ ions significantly inhibited the adsorption of Cu 2+, Zn 2+, and Cd 2+ ions, while Cu 2+ ions decreased remarkably the metal uptake of Cd 2+ and Zn 2+ ions. The relative adsorption between Cd 2+ and Zn 2+ ions was reduced similarly by the presence of the other metal ions.

Characterization of mesoporous rice husk ash (RHA) and adsorption kinetics of metal ions from aqueous solution onto RHA

The present study deals with the characterization of low-cost rice husk ash (RHA) for its various physico-chemical properties and adsorption characteristics of metal ions. The average particle size of RHA was 150.47 μm. Proximate analysis showed the presence of high amount of ash in RHA. Bulk density and the heating value of RHA were 104.9 kg/m 3 and 9.68 MJ/kg, respectively. The pore size distribution results showed that the RHA was predominantly mesoporous. The BET surface area was 36.44 m 2/g. The average pore diameter by BET was 42.603 Å. The BJH pore area showed 80% of the pore area due to the mesopores. The polar groups present on the RHA surface imparted considerable cation exchange capacity to it. RHA was found to be an effective adsorbent for the removal of cadmium (Cd(II)), nickel (Ni(II)) and zinc (Zn(II)) metal ions from aqueous solutions. The pH 0 ≈6.0 is found to be the optimum for the removal of individual cations from the aqueous solutions by RHA at an optimum dose of 10 kg/m 3. The kinetics of adsorption showed that the metal ions adsorption on RHA is a gradual process with quasi-equilibrium being attained in 5 h. The pseudo-second-order kinetics represents the equilibrium data well. The effective diffusion coefficient of the cations onto the RHA is of the order of 10 −13 m 2/s.

Enhanced Adsorption of Copper(II) Ion on Novel Amidoxime Chitosan Resin.

A novel resin organized from an amidoxime derivative of chitosan is prepared and the adsorption characteristics of metal ions are examined. Metal ions are adsorbed by forming chelates coordinated by nitrogen atoms of primary amino groups and oxygen atoms of oxime groups. The amidoxime chitosan resin (AO-b-1) retards the adsorption of nickel ion compared with that on N-(sulfopropyl)chitosan (PSC), and the maximum adsorption capacity of copper ion on AO-b-1 is 1.6 times as much as that for PSC. The adsorption capacity of copper ion is further enhanced by alkali treatment of the resin. The amidoxime chitosan resin is found to be an excellent adsorbent with high adsorption capacity and selectivity for copper ions.

Selective Adsorption of Metal Ions on Novel Chitosan-Supported Sulfonic Acid Resin.

A novel chitosan-supported sulfonic acid resin modified by propane sultone was prepared and the adsorption characteristics of metal ions are examined by using a crosslinked chitosan-supported sulfonic acid resin (PSC) and a crosslinked chitosan resin (CLC).In the low acidity region, the metal selectivity of PSC is similar to that of CLC. This suggested that the selectivity of PSC was attributed not to the sulfonate group but to the chitosan matrix. The role of the sulfonate is believed to be enriching the metal concentration in the neighborhood of the chitosan matrix. At the same time, since the hydrogen ion is also enriched in a thin layer near the surface of the main, the characteristic adsorption curves of PSC shift to the high pH region compared with those of CLC. The adsorption equilibrium constants of metal ion on PSC and CLC are evaluated. The maximum adsorption capacity for PSC in the case of adsorption of copper is 1.6 times that of CLC. On the other hand, in the high acidity region, the maximum adsorption capacity for PSC in the case of adsorption of palladium is lower than that for CLC because of steric hindrance.

Adsorption Characteristics of Metal Ions on Chitosan Chemically Modified by D-Galactose

Abstract The adsorption characteristics of metal ions on chitosan chemically modified by D-galactose were examined. The pH dependency on the distribution ratio was found to be affected by the valency of the metal ion, and the apparent adsorption equilibrium constants of the metal ions were determined. The order of adsorption of the metal ions is Ga > In > Nd > Eu for the trivalent metal ions and Cu > Ni > Co for the divalent metal ions. It is believed that amino and hydroxyl groups in the chitosan act as a chelating ligand.

Removal of copper from industrial wastewater by raw charcoal obtained from reeds

AbstractIn the present paper, we study the adsorption of Cu2+ from industrial wastewater and aqueous solution at 293 K, by a by‐product of activated carbon (raw charcoal) obtained from reds. A Method of preparation of raw charcoal was established and the main adsorption characteristics of metal ions were examined, as well as the static and dynamic conditions of the adsorption process. The adsorbent properties of the charcoal used were also studied. The presence of other metal ions in the solution decreases the adsorption capacity for copper, and the chemical nature of the charcoal surface and metal ions have a great significance for the adsorption process. The area of charcoal was about 400 m2 g−1 at a carbonization temperature of 973 K.