Maximum Sorption Capacity Research Articles

Porous Core-membrane Microstructured Nanomaterial Composed of Deep Eutectic Solvents and MOF-808 for CO2 Capture.

A series of porous core-membrane microstructured nanomaterials, constructed of a deep eutectic solvent (DES) membrane and porous MOF-808 core via liquid surface tensions and electrostatic interactions, are introduced for carbon dioxide capture with the sorption mechanism coupling diffusion, physisorption, and chemisorption. MOF-808 as the porous core considerably improves the diffusion interactions for DES membranes, hence significantly enhancing the sorption performance of DESs. Although the DES consisted by monoethanolamine and tetrapropylammonium chloride (MEA-TPAC-7) has the highest sorption capacity among all DESs, it is only 4.39 mmol g-1 at 2.4 bar and further attenuates by fastidious diffusion interactions when increasing viscosity or dose. The sorption capacities of DES@MOF-120 are 5.18 mmol g-1 at 3.0 bar and 4.78 mmol g-1 at 2.4 bar without apparent sorption hysteresis in pressure swing sorption, which are substantially improved contrasted to MEA-TPAC-7. The sorption isotherms are reconstructed via Sips models considering surface heterogeneity with regression correlation coefficients over 0.9454 to forecast maximum sorption capacity over 6.33 mmol g-1 .

Biochar as an effective material for acetone sorption and the effect of surface area on the mechanism of sorption

Walnut shells and apricot pits were used to produce non-activated, air-activated and steam-activated biochar. The specific surface area decreased in the order steam-activated (500–727 m 2.g-1), air-activated (59–514 m2.g-1) and non-activated biochars (1.71–236 m2.g-1). The results indicated that water steam created a multi-layer block structure with a well-developed porous structure, especially at 900 °C, while activation with air resulted in a more fragmented structure with a higher amount of coarse pores, leading to lower specific surface values. Acetone sorption experiments were performed in order to determine the acetone sorption capacity and to evaluate the acetone sorption kinetics of the biochars, as well as to identify the possible mechanism of sorption. The maximum sorption capacity estimated from the adsorption isotherms up to a relative pressure of 0.95 ranged from 60.3 to 277.3 mg g−1, and was highest in the steam-activated biochar with the largest surface area. The acetone adsorption isotherms were fitted with different adsorption models, where the Fritz-Schlunder model showed the best fitting results. The adsorption kinetics was evaluated using two kinetics models - pseudo first order and pseudo second order. The results indicated that the biochars with a large surface area exhibited physical sorption through van der Waals forces as the dominant mechanism, while acetone sorption on samples with a smaller surface area can be attributed to a mixed dual sorption mechanism, which combines physical sorption and chemisorption on oxygen functional groups. The perfect reusability of the biochars was confirmed by four consecutive adsorption-desorption cycles.

Sorption of copper (II) ions by a composite sorbent based on chitosan and montmorillonite

A composite sorbent based on chitosan and montmorillonite has been developed for the extraction of heavy metal ions from aqueous solutions. The optimal chitosan / montmorillonite ratio for obtaining sorbent granules has been determined. Equilibriumkinetic studies of the process of copper (II) ions extraction in the heterophase system "aqueous solution of metal sulphate - modified sorbent" have been carried out.The treatment of sorption isotherms of copper (II) ions by the initial chitosan and a chitosan based composite according to the Langmuir equation made it possible to determine the maximum sorption capacities of these materials (А∞). It has been established that A∞ of the chitosan/montmorillonite composite sorbent exceeds the maximum sorption capacity for the original chitosan by more than two times.The effect of pH on the sorption of copper ions by chitosan-based sorbents is due to the competition of metal cations and protons for sorption sites. In the course of competitive chemisorption, protons deactivate amino groups - the main sorption centers, converting them into an inactive, H-salt form, which leads to a decrease in the sorption capacity of chitosan in relation to copper ions.Changes in the composition of the modified sorbent compared to the original chitosan are confirmed by infrared spectroscopy data. Microscopic studies using the method of scanning electron microscopy show the presence of changes in the surface structure of chitosan granules when montmorillonite is introduced into the composition of the sorbent.

Evaluation of templated N/P co-doped hierarchical mesoporous biocarbon/2D-molybdenum disulfide/polypyrrole composite as a supercapacitor electrode for U(VI) electrosorption

In this work, a templated N/P co-doped hierarchical porous biocarbon was prepared through the carbonization of sugar at high temperature (700 °C). Then, this porous biocarbon was in-situ functionalized with molybdenum disulfide nanosheets through a hydrothermal treatment reaction to get the composite, SC/MoS2. Later, SC/MoS2 on a nickel foam substrate was electrodeposited with different concentrations of polypyrrole, a conducting polymer, at −0.9 V. The prepared composite electrodes (SC/MoS2/PPy) were characterized thoroughly using FTIR, XRD, BET, and SEM. The orderly developed mesoporosity and N, P doping inside the porous carbon network was found to be highly conducive for the U(VI) electrosorption accomplished through capacitive deionization (CDI). The composites had remarkable specific capacitance (95.4 F/g), a large specific surface area (174.4–273.6 m2/g), improved mesopore volume (0.58 cm3/g) and excellent Vm/Vt ratio (0.80). SC/MoS2/PPy-2, among other composites, revealed fast electrosorption kinetics and excellent selectivity with a maximum sorption capacity of 300.66 ± 8.02 mg/g at −0.9 V. The SC/MoS2/PPy-2 retained relatively small charge transfer resistance Rct (1.22 Ω cm2), minute electrolytic resistance Rs (0.77 cm2), and a large double layer constant phase element qdl (0.0369 S sn/cm2) which makes it suitable for U(VI) ion diffusion and fast electron transfer during CDI performance. The composite electrode materials offer novel and potent desalination applications, specifically in uranium extraction from aqueous media.

Insights into chloride sorption and phase transformation of the synthesized Ca-Al bimetallic oxides in flue gas desulfurization wastewater

Sorbents enriched with Ca3Al2O6 (C3A) and Ca12Al14O33 (C12A7) were successfully synthesized by a solid-state sintering method for Cl− removal from the flue gas desulfurization (FGD) wastewater. C3A and C12Al7-rich sorbents prepared at 1200 and 1100 °C achieved the highest Cl− removal of 83.3% and 73.1%, and the former had a higher aluminum utilization rate of 45.2%. Compositional analyses revealed that sorbents synthesized using α-Al2O3 had higher atomic density, higher ratio of absorbed oxygen to lattice oxygen, and higher AlO45−/AlO69− ratio than those using Al2O3, resulting in enhanced reactivity and superior Cl− removal performance. Higher calcination temperature also improved the crystallinity of bimetallic oxides. The sorption isotherms and thermodynamic studies confirmed that the sorption of Cl− on Ca-Al oxides was spontaneous and exothermic, and the maximum sorption capacities were 243.7 mg/g on C3A and 204.1 mg/g on C12Al7, respectively. Kinetics and characterizations suggested that the hydration-induced mineral phase transformation led to structural reconstruction, and the sorption mechanism involved a synergistic action of chemisorption (as the primary force) and physisorption. These results suggested that Ca-Al-based sorbents are highly promising alternatives for application in the zero liquid discharge process of FGD wastewater.

Fabrication of magnesium oxide–calcium alginate hydrogel for scaffolding yttrium and neodymium from aqueous solutions

In this research, the possibility of using sustainable nano-MgO/Ca-alginate beads for efficient sorption of some rare earth metal ions such as neodymium(III) and yttrium(III) from an aqueous acidic solution was explored. The nano-MgO/Ca-alginate beads adsorbent was characterized before and after sorption of Nd(III) and Y(III) using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), energy dispersive X-ray analysis (EDX), and X-ray diffraction (XRD) techniques. Batch sorption parameters were investigated, such as contact time, initial metal ion concentration, and adsorbent dose (V/m). The calculated experimental results showed that the suitable selected sorption conditions were carried out using 100 mg/L of Nd(III) and Y(III) with nano MgO/Ca-alginate beads (contact time = 90 min, pH = 2, V/m = 0.05 L/g). The maximum sorption capacity of 0.1 g of nano MgO/Ca-alginate was found to be 7.85 mg/g and 5.60 mg/g for Nd(III) and Y(III), respectively. The desorption of Nd(III) and Y(III) from the loaded nano MgO/Ca-alginate was achieved with 1.0 M sulfamic acid and found to be 51.0% and 44.2%, respectively. The calculated thermodynamic parameters for the nano MgO/Ca-alginate/Nd/Y system show that the positive charge of ΔHo confirmed the endothermic nature of the sorption process, ΔSo (positive) indicates an increase in reaction system disordering, and ΔGo (negative) indicates a spontaneous process. These kinetic results indicate that the sorption process of Nd(III) and Y(III) on nano MgO/Ca-alginate beads is performed by the chemisorption process.

Mechanochemical synthesis of graphitic carbon nitride/graphene oxide nanocomposites for dye sorption

The nanocomposites of graphitic carbon nitride supported on graphene oxide (g-C3N4/GO) were synthesized using the mechanochemical method, effectively leveraging the synergistic benefits of mechanical energy and chemical reactions. The sorption performance of g-C3N4/GO for methylene blue (MB) was explored using the Langmuir adsorption isotherm. The g-C3N4/GO nanocomposite exhibited a maximum sorption capacity (qmax) value of 116.41 ± 5.46 mg g−1 for MB at pH 7, while GO and g-C3N4 displayed qmax values of 55.71 ± 3.11 and 17.01 ± 1.65 mg g−1, respectively. The superior qmax value of g-C3N4/GO was attributed to the mechanochemical exfoliation of both GO and g-C3N4, resulting in its increased surface area and favorable surface characteristics. The highest sorption of MB on g-C3N4/GO was achieved at pH 10, with the qmax value of 191.20 ± 9.94 mg g−1. Furthermore, g-C3N4/GO demonstrated good reusability, maintaining a removal efficiency of 92% after five consecutive sorption cycles of MB. The sorption process was spontaneous at all the tested temperatures. A positive ΔH0 value of 18.8 kJ mol−1 suggests that the sorption process is predominantly physisorption. In the case of the negatively charged methyl orange (MO), no sorption occurred on the g-C3N4/GO. A red shift of 22 nm in the λmax of MO was instead observed due to the protonation of the azo group.

Chitosan functionalized with pyrazolinone derivative for water treatment: Application to Hg(II) removal

Due to its high toxicity, the removal of mercury from groundwater in contaminated industrial areas is of critical importance to avoid health problems for living beings. The functionalization of chitosan with pyrazolinone derivative, allows designing a sorbent (CH-PYZ) with high efficiency and selectivity for mercury sorption at acidic pH values (1.40 mmol Hg g−1, at pH 3). The sorbent is characterized by elemental analysis, thermogravimetric and textural analyses (increase in specific surface area and decrease in pore size), Fourier transform infrared spectroscopy, and shift of the pH point of zero charge toward higher value. The sorption was mainly performed through carbonyl, thiocarbonyl, hydroxyl, and amine groups. Under selected experimental conditions, sorption equilibrium is reached in 40 min (faster than crosslinked chitosan, CH) and the kinetic profile is fitted by the pseudo-first order rate equation. The Langmuir equation finely fits sorption isotherms: the functionalization improves both the maximum sorption capacity and the affinity coefficient (by four to six folds). The benefit of the functionalization is also demonstrated by the improved stability of the sorbent at recycling (loss at the fifth cycle does not exceed 2 % for CH-PYZ, against 8 % for CH). The grafting of pyrazolinone derivative brings another advantage in terms of selectivity against other mono-, di- and tri- valent metal ions. The sorbent also preferentially sorbs mercury from groundwater collected in a contaminated area. Under selected experimental conditions, the sorbent allows decontaminating the collected sample for livestock feeding, but the treated water cannot reach the levels for human drinking water.

Sorption Capacity of Carbon-Based Mandarin Orange Peels for Removing Methylene Blue and Ibuprofen from Water

Pharmaceutical pollutants in water pose a serious environmental challenge. This research compared the adsorption capacity of mandarin orange peels (MOP) and activated carbon mandarin orange peels (AC-MOP) to adsorb methylene blue (MB) and Ibuprofen (IBF) from an aqueous solution. This is the first study to report on the uptake of Ibuprofen using carbonized mandarin orange peels activated with hydrochloric acid. The biomaterials were characterized using FTIR and SEM. Batch experiments with operational parameters such as pH, contact time, concentration and temperature were investigated for the adsorption of MB and IBF. Isotherms, kinetic calculations and thermodynamic parameters were calculated for the adsorption of MB and IBF. A positive ΔH° suggested the reaction was endothermic, and ΔG° values showed that the sorption process was spontaneous. The isotherm models best fit the Langmuir model with maximum sorption capacities of 74.15 and 78.15 mg/g for MB and IBF, respectively. The adsorption rate for MB was fast and took place within the first 10 min, whilst the removal of IBF was observed at 40 min. The kinetic model evaluation showed that pseudo-second-order was a suitable fit for the mechanism. The re-usability data indicated that the recovery of MB was 70.13%, and IBF was 87.17%. The adsorption capacity of IBF with the carbon-based MOP was higher than that of MB. The results indicated that AC-MOP could be used as an adsorbent for MB and IBF from water. The major advantage of this method is its effectiveness in reducing the concentration of dyes and pharmaceutical pollutants using inexpensive adsorbents.

Effective removal of arsenite from water using polylactic acid ZIF-8 biocomposite nanofiber

Water purification from As(III)-contaminated groundwater is difficult but highly needed. Herein, a new polylactic acid ZIF-8 biocomposite nanofiber mat (ZIF-8@PLA/NFM) was fabricated using an electrospinning technique for As(III) decontamination. The active component, ZIF-8 nanoparticles, are uniformly embedded in sustainable PLA fibers and can be rapidly contacted by As(III), achieving fast kinetics and high utilization of nanoparticles. The removal experiments show that the ZIF-8@PLA/NFM can effectively remove As(III), especially in combination with H2O2. The 50%-ZIF-8@PLA/NFM with 1 mM H2O2 reduced 1000 μg/L As(III) to less than 10 μg/L in just 5 min through the synergy of oxidation and adsorption. The maximum sorption capacity for As(III) on 50-ZIF-8@PLA/NFM was 11.61 ± 0.99 mg/g, which increased to 39.25 ± 3.84 mg/g with the addition of H2O2. It performed well in the pH range of 4–9. The combination of H2O2 broadened its effective pH operating range (3–10) as well as enhanced interference resistance, enabling deep removal of As(III) across a wide range of water environments. The As(III)-spiked natural water (100 μg/L) could be purified to drinking standard level by ZIF-8@PLA/NFM within 60 min. In combination with H2O2, the removal efficiency was reduced by only 1.5% at the fifth reuse. Macroscopic experiments and microscopic characterization suggest that the adsorption follows the inner-sphere complexes mechanism. The study provides a novel approach for the fabrication of efficient, easy-to-use, and sustainable MOFs-based biocomposite for As(III) decontamination.

Rice husk ash as sorbent for solid phase extraction of diclofenac, ibuprofen and carboplatin residues from waters

Carboplatin, ibuprofen and diclofenac are among drugs classified as emergent pharmaceutical contaminants that impact negatively the environment. Development of affordable procedures for their quantification and removal from waters is gained interest in the scientific community. The present study was aimed at the characterization of rice husk ash as sorbent for the solid phase extraction of mentioned drugs in waters. Optimal sorbent dose, pH dissolution and contact time were selected. Up to the best of our knowledge, the good performance of rice husk ash for extraction of carboplatin, ibuprofen and diclofenac from aqueous dissolutions is demonstrated for the first time in the present study, achieving a maximum sorption capacity of 5.843 mg.g−1, 2.321 mg.g−1 and 2.316 mg.g−1, respectively, which are higher than those reported for others pharmaceutical products with husk rice ashes. Kinetic of sorption was well modeled by a Lagergren pseudo first order model for diclofenac and by a pseudo second order model of Ho for ibuprofen and carboplatin. Sorption at equilibrium conditions was well modeled by Freundlich and Toth isotherms for diclofenac and ibuprofen, while Sips, Toth and Dubinin-Radushkevich isotherms adjusted well for carboplatin. Kinetic and at equilibrium conditions studies confirmed the high complexity of involved sorption mechanisms in the three adsorbate/rice husk ash systems considered.

Sorption of Ibuprofen by chemically treated maize cob

Potable water availability has been drastically reduced because of the indiscriminate discharge of pharmaceuticals into rivers and surrounding areas. Polluted water disrupts aquatic life and affects human health. This study investigated the potential of using NaOH-activated maize cobs for removing Ibuprofen (IBP) from a synthetic solution. The sorption capacity of the base-treated maize cob (BMC) and untreated maize cob (UMC) was compared. Batch adsorption experiments were conducted using several parameters, including a range of pH values (2–10), contact time (1–100 min), initial concentration (15–60 mg/L) and temperatures (25–65 °C). Ibuprofen's highest sorption capacity (44.92 mg/g) was obtained with BMC at pH 8.0, whilst the adsorption by UMC was 41.81 mg/g at pH 7.99. The sorption trend by both BMC and UMC indicated that the uptake of Ibuprofen increased at initial concentrations of 34.77 and 28.66 mg/g, respectively. The non-linear form of the Freundlich isotherm model best fits with the experimental results, describing the favorability of chemical interactions between IBP and both adsorbents. The removal time was fast, and the adsorption kinetics was based mainly on the pseudo-first-order model with capacities of 45.96 mg/g for BMC and 42.30 mg/g for UMC. The negative ∆Go and ∆H° values proved that the adsorption process was spontaneous and exothermic, with maximum capacities of 44.07 and 40.33 mg/g obtained at 25 ℃ by BMC and UMC, respectively. The chemically treated BMC showed better sorption than the UMC. Batch studies showed that the overall maximum sorption capacities were 91.07% and 90.67% for BMC and UMC respectively. This research showed that maize cobs can be used as an adsorbent for removing Ibuprofen from solutions.

Polydimethylsiloxane-carbon nanotubes-based hydrophobic sponge for treatment of palm oil mill effluents with enhanced reusability

Improper treatment and discharge of palm oil mill effluents (POME) into the water bodies have become one of the leading causes of aqueous contamination due to the release of a large volume of POME into the environment. This study reports the development of poly(dimethylsiloxane) (PDMS) and carbon nanotubes (CNTs) supported sorbent material to reduce the oil and grease (O&G) content of POME. The morphology and chemical properties of the prepared material were characterized using SEM-EDX, FTIR, Raman spectroscopy, XRD, TGA, water contact angle, and pH point of zero charge (pHPZC) analysis. CNT-PDMS optimal O&G removal capacity has been determined using batch experiments with varying parameters, including CNT wt%, contact time, pH, and initial POME concentration. The introduction of CNT significantly improves the oil sorption capacity almost three times as compared to pure PDMS. The maximum sorption capacity achieved was 658.09 ± 7.21 mg/g with the O&G removal of 84% within 8 min using initial POME concentration (1:20) and at room temperature. The study shows that the O&G sorption process using PDMS and CNT-PDMS-0.8 followed the pseudo-second-order kinetic model. Moreover, the adsorption isotherms study revealed that the adsorption process can be described by the Freundlich isotherm model based on the R2 values of 0.98075 and 0.99981 for PDMS and CNT-PDMS-0.8, respectively. Furthermore, the composites also show excellent reusability, retaining high O&G sorption and removal even after the tenth cycle.

A Comparative Study of Cr(VI) Sorption by Aureobasidium pullulans AKW Biomass and Its Extracellular Melanin: Complementary Modeling with Equilibrium Isotherms, Kinetic Studies, and Decision Tree Modeling.

Melanin as a natural polymer is found in all living organisms, and plays an important role in protecting the body from harmful UV rays from the sun. The efficiency of fungal biomass (Aureobasidium pullulans) and its extracellular melanin as Cr(VI) biosorbents was comparatively considered. The efficiency of Cr(VI) biosorption by the two sorbents used was augmented up to 240 min. The maximum sorption capacities were 485.747 (fungus biomass) and 595.974 (melanin) mg/g. The practical data were merely fitted to both Langmuir and Freundlich isotherms. The kinetics of the biosorption process obeyed the pseudo-first-order. Melanin was superior in Cr(VI) sorption than fungal biomass. Furthermore, four independent variables (contact time, initial concentration of Cr(VI), biosorbent dosage, and pH,) were modeled by the two decision trees (DTs). Conversely, to equilibrium isotherms and kinetic studies, DT of fungal biomass had lower errors compared to DT of melanin. Lately, the DTs improved the efficacy of the Cr(VI) removal process, thus introducing complementary and alternative solutions to equilibrium isotherms and kinetic studies. The Cr(VI) biosorption onto the biosorbents was confirmed and elucidated through FTIR, SEM, and EDX investigations. Conclusively, this is the first report study attaining the biosorption of Cr(VI) by biomass of A. pullulans and its extracellular melanin among equilibrium isotherms, kinetic study, and algorithmic decision tree modeling.

Enhanced complexation and electrostatic attraction through fabrication of amino- or hydroxyl-functionalized Fe/Ni-biochar composite for the adsorption of Pb(II) and Cd(II)

To enhance Pb(II) and Cd(II) elimination, new composites (FeNi-RSN-(OH)(NH2) and FeNi-RSN-OH) were fabricated by loading biochar with Fe-Ni nanoparticles and functionalizing biochar by amination/hydroxylation in the study. The maximum sorption capacities of both adsorbents toward Pb(II)/Cd(II) were 217.09/209.36 mg/g and 242.15/229.52 mg/g, respectively, which were 4.30–4.79 times higher than those of the raw biochar. The significantly enhanced adsorption capacity could be attributed to the increased O/N-containing groups and Fe-Ni nanoparticles on the adsorbent surface. The introduction of Fe-Ni nanoparticles and O/N-containing groups promoted the complexation and electrostatic interactions and made them playing major roles in the adsorption. Besides, ions exchange and physical adsorption played non-negligible roles in the adsorption process. Additionally, the both adsorbents exhibited favorable anti-interference ability and cycling stability. Taken together, the study revealed that the new biochar composites of FeNi-RSN-(OH)(NH2) and FeNi-RSN-OH could be used as a reusable magnetic adsorbents with promising prospect in current practice for the effective remediation of heavy metals-bearing wastewater. The study not only provided a feasible design, synthesis and optimization strategy of biochar for heavy metals contaminants removal, but also realized the sustainable utilization of waste.

An Innovative Look into Ammonium Nitrogen Removal Using Algae and Zeolites as an Element of a Circular Bioeconomy

This work focused on the potential of simultaneously removing ammonium nitrogen from industrial wastewater using immobilized microalgae and powdered zeolite. Experiments were performed with different species and doses of microalgae embedded in spherical hydrogels in semicontinuous conditions. Ammonium nitrogen uptake by microalgae promoted the slow release of previously adsorbed ammonium nitrogen from zeolite that was then also absorbed by microalgae. Results showed that immobilized microalgae can reach a removal efficiency of up to 60% (C. vulgaris) and 42% (S. armatus). A higher removal efficiency was obtained for zeolites and immobilized C. vulgaris or S. armatus up to 86% and 79%, respectively. Moreover, a higher maximum sorption capacity for C. vulgaris (13.8 mg/g) was achieved than for S. armatus (5.5 mg/g). The recycling of spent hydrogel, zeolite, and wastewater is possible. Such an approach represents a circular bioeconomy loop.

A comprehensive study for the potential removal of 152+154Eu radionuclides using a promising modified strontium-based MOF

A facile modification of a strontium-based MOF using oxalic acid was carried out to prepare MTSr-OX MOF, which was used as a potential substance for eliminating 152+154Eu radioisotopes. Various analytical techniques were used to characterize MTSr-OX-MOF. The prepared MOF had a rod-like structure with a BET surface area of 101.55 m2 g−1. Batch sorption experiments were used to investigate the sorption performance of MTSr-OX-MOF towards 152+154Eu radionuclides where different parameters like pH, contact time, initial 152+154Eu concentration, ionic strength, and temperature were scrutinized to determine the optimum conditions for 152+154Eu removal. MTSr-OX-MOF showed superior effectiveness in the elimination of 152+154Eu with a maximum sorption capacity of 234.72 mg g−1 at pH 3.5. Kinetics fitted with the pseudo-second-order model and the Langmuir model correctly described the sorption mechanism. The thermodynamic variables were carefully examined, demonstrating that the 152+154Eu sorption was endothermic as well as spontaneous. The MTSr-OX-MOF has been found to be a significantly more effective sorbent towards 152+154Eu than that of many other adsorbents. When applied to real active waste, MTSr-OX-MOF demonstrated excellent removal performance for a wide range of radionuclides. As a result, the MTSr-OX-MOF can be recognized as an attractive solution for the 152+154Eu purification from active waste.

Recovery of rhodium from glacial acetic acid manufacturing effluent using cellulose-based sorbent

Rhodium (Rh) is a rare and highly demanded metal in metallurgy, making its efficient recovery from waste streams essential. However, there is a lack of detailed studies on the recovery of Rh from acidic waste effluents using biosorbents. This study aims to extract RhIII from acidic effluents using dithiocarbamate-modified cellulose (DMC) as a biosorbent, and subsequently recover the extracted Rh in its elemental form (Rh0). The parameters affecting the RhIII extractability of DMC, such as solution pH, acid concentration, Cl− ion concentration, contact time, and sorption capacity at different temperatures, were optimized. The sorption kinetics of RhIII onto DMC was best fitted to the pseudo-second-order (PSO) model, the equilibrium sorption isotherm data fitted well with the Langmuir model. DMC had a maximum sorption capacity of 2.57 mmol g−1, which is substantially higher than that reported in previous studies. Waste effluent (Rh-containing glacial acetic acid) obtained from the acetic acid manufacturing industry was used to assess the applicability of DMC in capturing RhIII from a real sample. DMC was capable of sorbing approximately 90 % of RhIII from the real sample of Rh-containing glacial acidic acid. The sorbed RhIII was recovered in elemental form (Rh0) by incineration of RhIII-loaded DMC, yielding >99 %. The sorption of RhIII onto DMC followed a chemisorption mechanism that was confirmed by sorption experiments, Fourier-transform infrared spectroscopy (FTIR), and X-ray absorption spectroscopy (XAS) analyses. This study demonstrates the applicability of DMC in the efficient recovery of Rh from waste streams.

Sorption of Metal Ions from Aqueous Solutions by Humic Substances

Humic substances (HSs) extracted from brown coal, peat, and other sources are considered as anefficient and affordable sorbent used to trap and bind heavy metal ions, which are hazardous to the environment.This paper provides an overview of modern works on this subject matter. Typical structural characteristicsand properties of HSs and methods for their extraction from brown coal, peat, swamp waters, and othermedia are described, and quantitative results of a wide range of experiments on the sorption of metal ions byHSs are presented. Significant fluctuations in the measured sorption capacity of HSs in different experimentsprobably arise not so much due to variations in the elemental composition and structure of HSs extractedfrom different sources, but they are associated with experimental conditions, such as the acidity (pH) of solution,ionic strength, concentration of metal ions, and concentration of HSs in the solution. In terms of theorder of magnitude, the maximum sorption capacity of HSs is comparable to the total concentration of surfacecarboxyl and hydroxyl groups, and it amounts to several millimoles of metal ions per gram of HSs

Efficient adsorptive removal of Co2+ from aqueous solution using graphene oxide.

This study aimed to utilize synthesized graphene oxide (GO) for adsorptive removal of cobalt ions and investigate the adsorption mechanism using advanced techniques such as X-ray absorption spectra (XAFS). The GO was synthesized via an improved Hummers method, resulting in high surface area (93.7 m2/g) and abundant oxygen-containing functional groups. Various characterizations, including SEM, TEM, Raman, FT-IR, TG, potentiometric titrations, and N2 sorption-desorption measurements, were employed to characterize the GO. The adsorption behavior of GO towards Co2+ was investigated, and the results showed that the adsorption process followed a pseudo-second-order kinetic model and the Langmuir model, with a maximum sorption capacity of 93.7 mg/g. The adsorption process was chemisorption and endothermic, with GO showing adsorption selectivity order of Co2+ > Sr2+ > Cs+. Based on various characterizations such as X-ray absorption near-edge spectroscopy (XANES), extended X-ray absorption fine structure (EXAFS), FT-IR, and XPS, the sorption mechanism of Co2+ onto GO was discussed, with the results indicating that coordination and electrostatic interaction were the primary adsorption mechanisms, with oxygen-containing functional groups playing a vital role. The first coordinating atom for Co2+ was O, and the coordination environment was similar to that of cobalt acetate and CoO. Overall, this study provides comprehensive understanding of the adsorption behavior and mechanism of Co2+ onto GO, highlighting its potential as an effective adsorbent for removing nuclides from aqueous solution.