Multiple Adsorption Cycles Research Articles

Ti3C2TX MXene/loofah-derived carbon aerogel for high-efficiency adsorption of organic pollutants in wastewater

The contamination of wastewater by organic pollutants significantly impacts human health and the environment due to their carcinogenic nature and various adverse effects. To address this issue, this study offers a high-efficiency and low-cost biomass-based carbon aerogel adsorbent, which was prepared through the hydrothermal carbonization of loofah, followed by Ti3C2TX MXene impregnation. The aerogel features a porous three-dimensional network structure and a substantial specific surface area, facilitating broad-spectrum adsorption capabilities for various dyes and drugs. The aerogel achieved impressive adsorption capacities of 175.29 and 75.73 mg/g for cationic methylene blue and Rhodamine B dyes, and 106.33 and 93.29 mg/g for anionic methyl orange and Congo red dyes, as well as 86.25 mg/g for tetracycline hydrochloride, surpassing other reported biomass-based aerogels. Furthermore, it demonstrated effective decolorization ability for wastewater containing mixed dyes. Notably, it exhibited excellent recycling and regeneration properties, maintaining a high removal rate after multiple cycles of adsorption–desorption. The adsorption process of dye/drug by the aerogel followed Langmuir’s monomolecular layer adsorption model, exhibiting spontaneous, endothermic, and disorder-increasing behavior in alignment with the pseudo-second-order kinetic model. This study presents an efficient biomass-based aerogel for the removal of organic pollutants from wastewater.

Enhancing fluoride ion removal from aqueous solutions and glass manufacturing wastewater using modified orange peel biochar magnetic composite with MIL-53

In this study, we developed new adsorbents derived from orange peel biochar (BCOP) and enhanced them with CoFe2O4 magnetic nanoparticles (BCOP/CoFe2O4) and MIL-53(Al) (BCOP/CoFe2O4/MIL-53(Al)). These adsorbents were utilized to remove fluoride (FL) ions from aqueous solutions. We analyzed the properties of these adsorbents using a range of techniques, including FTIR, XRD, SEM, EDX-Map, VSM, Raman spectroscopy, and BET. Our findings indicate that the components interact effectively with one another. Specifically, the BCOP/CoFe2O4/MIL-53(Al) sample exhibited a specific surface area of 196.430 m2/g and a magnetic saturation value of 9.704 emu/g. The maximum FL ion adsorption capacities for BCOP, BCOP/CoFe2O4, and BCOP/CoFe2O4/MIL-53(Al) were 7.618, 16.330, and 37.320 mg/g, respectively, indicating that the modifications significantly enhanced the adsorption capacity. The optimum fluoride ion removal rates using BCOP, BCOP/CoFe2O4, and BCOP/CoFe2O4/MIL-53(Al) were 97.88%, 98.23%, and 99.06%, respectively, at adsorbent doses of 2.5, 1.5, and 0.8 g/L, contact times of 90, 70, and 50 min, pH 4, temperature 50 °C, and a FL concentration of 10 mg/L. Thermodynamic studies revealed that the adsorption process was spontaneous and endothermic, with increased randomness between the adsorbent and fluoride ions. Kinetic analyses showed that fluoride ion adsorption by BCOP/CoFe2O4/MIL-53(Al) followed a pseudo-second-order (PSO) model, while BCOP and BCOP/CoFe2O4 followed a pseudo-first-order (PFO) model. Additionally, the equilibrium data for fluoride ion adsorption on BCOP/CoFe2O4/MIL-53(Al) adhered to the Freundlich model, whereas the other samples conformed to the Langmuir model. The study evaluates the effectiveness of BCOP, BCOP/CoFe2O4, and BCOP/CoFe2O4/MIL-53(Al) in removing FL ions from glass manufacturing wastewater, highlighting the superior performance of the magnetic composite due to its enhanced surface area and functional groups. Notably, the adsorbents demonstrated good regenerative capabilities, maintaining high performance over multiple adsorption cycles.

Methylene blue and acid red adsorption on biochar made from modified sugarcane bagasse: A dynamic, equilibrium, and thermodynamic investigation

This study synthesized biochar adsorbents from chemically activated sugarcane bagasse using ZnCl2 at pyrolysis temperatures of 400, 500, and 600°C. The modified bagasse biochar was used to remove methylene blue (MB) and acid red (AR) dyes. The surface characteristics of the modified bagasse biochars were analyzed using Scanning Electron Microscope (SEM), Fourier Transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) analysis. Batch adsorption experiments were conducted to assess the impact of various parameters on adsorption performance. Among the different bagasse biochar samples, Zn-BC-600 exhibited superior adsorption capacities for MB and AR with values of 182.225 and 43.324 mg/g, respectively. The adsorption efficiency was significantly influenced by pH, with optimal conditions at pH = 6.0 for MB and pH = 2.0 and 10.0 for AR. The adsorption process for MB and AR on Zn-BCs followed a pseudo-second-order kinetic model, indicating chemisorption as the primary mechanism. Adsorption isotherm studies revealed that Zn-BCs conform to the Freundlich model, proposing a multilayer adsorption due to the heterogeneity of the biochar surface. Regeneration experiments indicated that Zn-BCs could be reused for multiple adsorption cycles. In conclusion, the modified bagasse biochar showed strong adsorption affinity for both MB and AR, particularly for MB, making it a promising adsorbent for treating printing and dyeing wastewater.

Preparation of Steel-Slag-Based Hydrotalcite and Its Adsorption Properties on Cl− and SO42−

Large amounts of chloride ions (Cl−) and sulfate ions (SO42−) are present in salt-washing wastewater, making it unsuitable for direct release. Adsorption can be used to eliminate Cl− and SO42− from salt-washing wastewater, and hydrotalcite is an excellent adsorbent with high adsorption properties for these ions because of a layered bimetallic hydroxide structure. The selective extraction of various metals, such as calcium, magnesium, aluminum, and iron, from steel slag via acid leaching facilitates the utilization of steel slag in the preparation of hydrotalcite. In this study, the leaching mechanism of metal in steel slag was investigated using steel slag as a raw material and acetic acid as the reaction medium. The study obtained the optimal leaching mechanism for preparing hydrotalcite. Hydrotalcite was synthesized from the steel slag leaching solution by hydrothermal synthesis, and its structure was characterized. The adsorption performance of Cl− and SO42− in salt-washing wastewater was investigated by solution adsorption experiments. The removal rates of Cl− and SO42− in salt-washing wastewater reached 12.8% and 38.0%, respectively. After multiple adsorption cycles, the removal rates increased to 98.0% for Cl− and 96.4% for SO42−.

Enhanced atmospheric water harvesting efficiency through green-synthesized MOF-801: a comparative study with solvothermal synthesis

Adsorption-based atmospheric water harvesting has emerged as a compelling solution in response to growing global water demand. In this context, Metal–organic frameworks (MOFs) have garnered considerable interest due to their unique structure and intrinsic porosity. Here, MOF 801 was synthesized using two different methods: solvothermal and green room temperature synthesis. Comprehensive characterization indicated the formation of MOF-801 with high phase purity, small crystallite size, and excellent thermal stability. Nitrogen adsorption–desorption analysis revealed that green-synthesized MOF-801 possessed an 89% higher specific surface area than its solvothermal-synthesized counterpart. Both adsorbents required activation at a minimum temperature of 90 °C for optimal adsorption performance. Additionally, green-synthesized MOF-801 demonstrated superior adsorption performance compared to solvothermal-synthesized MOF-801, attributed to its small crystal size (around 66 nm), more hydrophilic functional groups, greater specific surface area (691.05 m2/g), and the possibility of having a higher quantity of defects. The maximum water adsorption capacity in green-synthesized MOF-801 was observed at 25 °C and 80% relative humidity, with a value of 41.1 g/100 g, a 12% improvement over the solvothermal-synthesized MOF-801. Remarkably, even at a 30% humidity level, green-synthesized MOF-801 displayed a considerable adsorption capacity of 31.5 g/100 g. Importantly, MOF-801 exhibited long-term effectiveness in multiple adsorption cycles without substantial efficiency decline.

On the Sorbent Ability and Reusability of Graphene-Oxide–Chitosan Aerogels for the Removal of Dyes from Wastewater

One of the most persistent issues affecting people worldwide is water contamination due to the indiscriminate disposal of pollutants, causing severe environmental problems. Dyes are among the most harmful contaminants because of their high chemical stability and consequently difficult degradation. To remove contaminants from water, adsorption is the most widely used and effective method. In this work, we recall the results already published about the synthesis, the characterization and the use of porous graphene-oxide-chitosan aerogels as a sorbent material. Those systems, prepared by mixing GO sheets and CS chains, using APS as a cross-linking agent, and by further lyophilization, were further characterized using nano-computed tomography, supplying more understanding about their micro and nano-structure. Their sorbent ability has been investigated also by the study of their isotherm of adsorption of two different anionic dyes: Indigo Carmine and Cibacron Brilliant Yellow. Those analyses confirmed the potentialities of the aerogels and their affinity for those anionic dyes. Moreover, the possibility of regenerating and reusing the material was evaluated as a key aspect for applications of this kind. The treatment with NaOH, to promote the desorption of adsorbed dyes, and subsequent washing with HCl, to re-protonate the system, ensured the regeneration of the gels and their use in multiple cycles of adsorption with the selected water contaminants.

Adsorption of potentially harmful elements by metal-biochar prepared via Co-pyrolysis of coffee grounds and Nano Fe(III) oxides

Nano Fe(III) oxide (FO) was used as an amendment material in CO2-assisted pyrolysis of spent coffee grounds (SCG) and its impacts on the syngas (H2 & CO) generation and biochar adsorptive properties were investigated. Amendment of FO led to 153 and 682% increase of H2 and CO in pyrolytic process of SCG, respectively, which is deemed to arise from enhanced thermal cracking of hydrocarbons and oxygen transfer reaction mediated by FO. Incorporation of FO successfully created porous structure in the produced biochar. The adsorption tests revealed that the biochar exhibited bi-functional capability to remove both positively charged Cd(II) and Ni(II), and negatively charged Sb(V). The adsorption of Cd(II) and Ni(II) was hardly deteriorated in the multiple adsorption cycles, and the adsorption of Sb(V) was further enhanced through formation of surface ternary complexes. The overall results demonstrated nano Fe(III) oxide is a promising amendment material in CO2-assisted pyrolysis of lignocellulosic biomass for enhancing syngas generation and producing functional biochar.

Effective adsorption of Ultra-dilute CO2 over Polyethyleneimine-based adsorbent for H2 purification

Ultrahigh-purity hydrogen (6 N grade) suitable for hydrogen fuel cells requires the removal of CO2 impurity from commercial hydrogen feed. In this study, CO2 adsorption over a series of potential solid adsorbents was assessed at both high (0.1–1 bar) and low (hundreds of part-per-million) concentrations. With a distinct trend at higher concentrations (0.1–1 bar), PEI/S showed a remarkable CO2 capacity of 0.86 mmol/g at concentration as low as hundred part-per-million and outperformed the other adsorbents. The impacts of polyethylenimine (PEI) loading, adsorption temperature, co-existing H2O, and regenerability were investigated systematically. Adsorption isotherms of PEI/S at various loadings were represented with the Langmuir–Freundlich model, while adsorption kinetics were simulated and fitted with the AFO model. The effectiveness of PEI/S for CO2 removal was further investigated in dynamic fixed-bed breakthrough experiments. The co-presence of trace water vapor in the feed stream showed negligible inhibition on CO2 adsorption. In addition, multiple cycles of adsorption–desorption tests demonstrated the excellent regenerability of the PEI/S adsorbents. This study gave a comprehensive evaluation and demonstration of supported polyethylenimine as a potential TSA adsorbent for adsorptive removal of trace CO2 for ultrahigh purity H2 production.

Confined space synthesis of chromium–based metal–organic frameworks in activated carbon: Synergistic effect on the adsorption of contaminants of emerging concern from water

The steadfast presence of contaminants of emerging concern (CECs) in the environment calls for tailored remediation strategies. In this regard, Cr-based metal-organic frameworks (MOFs; MIL-100Cr and MIL-101Cr) were grown inside of activated carbon (AC) pores via confined synthesis for a superior adsorptive removal of those CECs from water. The composites CMOF-100Cr and CMOF-101Cr, as well as the apohost AC and pure MOFs, were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis by X-rays (EDAX), nitrogen adsorption–desorption, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy, and zeta potential measurements. XRD, SEM/EDAX, TGA, and pore size distribution data provided direct evidence of the successfully confined space syntheses of the hierarchical composites. Occupancy of the large voids of AC by the MOF was 100% and 43% for CMOF-100Cr and CMOF-101Cr, respectively. The adsorption capacity of the materials was evaluated in both single- and multi-component fashion at neutral pH and low CEC concentrations (μg L−1). The CECs were caffeine (CFN), carbamazepine (CBZ), clofibric acid (CA), naproxen (NPX), and metabolites 10,11-epoxycarbamazepine (Ep-CBZ), o-desmethylnaproxen (o-DMN), paraxanthine (PXN), and salicylic acid (SA). In general, the observed capacities for both single and multi-component adsorption of CECs increased as follows MIL-100Cr < < MIL-101Cr < CMOF-101Cr < AC < < CMOF-100Cr. Compared to the composite containing MIL-100Fe (i.e., CMOF-100Fe) previously developed by our group, the substitution of the metal node by Cr3+ produced significant enhancements in CEC uptake capacities. The affinity of CMOF-100Cr toward CECs increases as follow: SA < CA< o-DMN < NPX < PXN < CFN < Ep-CBZ < CBZ. Environmental significanceThe persistence of contaminants of emerging concern (CECs) in water mandates the development of tailored remediation strategies. To be suitable, these must consider efficacy and avoid undesired byproducts. An attempt to individually grow two chromium-based nanoporous metal-organic frameworks, each possessing particular linkers, within the pores of an activated carbon via confined space synthesis has proven to be effective in the adsorptive removal of a set of CECs that included metabolites. Furthermore, the adsorption was conducted in both single- and multi-component fashion to gain insight into the CECs competitive nature during uptake. The hierarchical composite adsorbents exhibited superior uptake capacity because of the synergistic combination of hydrophobicity and specific interactions between the metal node and the CECs, while multiple adsorption cycles were possible via thermal regeneration.

Surface-Encapsulated Bismuth Molybdate-Layered Silicate Hybrids as Sorbents for Photocatalytic Filtration Membranes.

Groundwater is being depleted globally at an average rate of more than one meter per year, during a period when more than a quarter of the human population has no access to potable water. Aside from overexploitation, freshwater security is also threatened by climate change and chemical pollution. The contamination of surface and groundwater by industrial substances is also undermining the vitality of ecosystems. It was previously shown that {100}-faceted Bi2MoO6-Laponite hybrids effectively bind and photodegrade molecular species, aiding in the decontamination of water. In this study, the encapsulation of Bi2MoO6-Laponite particles with the polymers butyl acrylate and styrene further enhanced adsorption of methylene blue by 31.4%, with a specific adsorption capacity of 192 μmol/g. The polymer-particle composites were deposited to form membranes and their efficacies in water filtration and photodegradation were examined. Among the different surface modifications examined, the highest dye sorption was obtained by butyl acrylate and styrene (3:2) with a 5 mol % cross-linker. This study provides a method for enhancing the molecular adsorption of composite particles used in membranes capable of multiple cycles of adsorption and photodegradation, advancing the application of such systems to water filtration.

Fluorine adsorption on floating iron nanoparticles confined to gigaporous structure of large adsorbent water spheres

Effective defluoridation of artesian well water can be performed with iron nanoparticles confined to expanded reticulated polymer network of polyvinyl alcohol (PVA) containing a high quantity of water. For this purpose, large (3433 ± 63 μm) adsorbent water spheres, meaning spheres containing Fe2O3 (15.8 wt%)-PVA (8.2 wt%)-H2O (76.0 wt%), were manufactured (sol–gel process) and characterized (TG/DTA, XRD, MÖSSBAUER, SEM/EDS, BET, FTIR, and XPS). In the resulting spongy water spheres, gigapores (140,000 nm) were filled with loosely agglomerated and floating naked nanoparticles (<20 nm) of octahedral [Fe2O2(H2O)8]2+ and/or [Fe2O3(H2O)6]0 complexes without prejudice to the chemical and mechanical (35.0 ± 0.4 kPa) stability of the nanostructured adsorbent. The built-in mesoporous and gigaporous structure provided good pore connectivity, which significantly reduced the adsorption rate limitation imposed by boundary-layer and intraparticle diffusion effects as well as it has enhanced the adsorptive capacity (from 77.9 to 204.9 mgF/g) of the referred adsorbent water spheres. XPS proved the chemical interaction mechanism in F–Fe–PVA–H2O system. Fluoride chemisorption occurs on PVA (marginally; (-CH2CHF-)n, (-CH2CF2-)n, and (-CF2CF2-)n) and Fe (predominantly; octahedral Fe2F5.7H2O complex) particles. Adsorbent water spheres can defluorinate natural waters in multiple adsorption cycles in fixed bed columns after fluorine desorption with NH4OH.

Biomass as source for hydrochar and biochar production to recover phosphates from wastewater: A review on challenges, commercialization, and future perspectives

Excessive phosphate run-off with total phosphorus concentration greater than 20 μg P L−1 triggers the growth of harmful algal species in waterbodies and potentially leads to eutrophication. This has severe negative implications on aquatic environment and impacts human health. The annual economic impact of harmful algal blooms is reported to be as high as $25 million for public health and commercial fishery sector, $29 million for recreation/tourism sector and $2 million for monitoring and management. Adsorption is widely considered as an effective and economic strategy to achieve extremely low concentration of phosphorus. The char produced by valorizing various waste biomasses have been gaining attention in phosphorus remediation owing to their availability, their ability to regenerate and reuse. This review paper exclusively focuses on utilizing hydrochar and biochar synthesized from waste biomass, respectively, through hydrothermal carbonization and slow pyrolysis to mitigate phosphorus concentration and potential strategies for handling the spent char. The key mechanisms involved in phosphate adsorption are electrostatic interaction, ion exchange and complexation. The maximum adsorption capacity of hydrochar and biochar ranges from 14–386 mg g−1 and 3–887 mg g−1, respectively. Hydrochar and biochar are cost-effective alternative to commercial activated carbon and spent char can be used for multiple adsorption cycles. Furthermore, extensive research studies on optimizing the feedstock, reaction and activation conditions coupled with technoeconomic analysis and life cycle assessment could pave way for commercialization of char-based adsorption technology.

Cover Feature: Inherent Ethyl Acetate Selectivity in a Trianglimine Molecular Solid (Chem. Eur. J. 41/2021)

Guided by crystal structure prediction, a “templating” strategy was used to construct selective binding sites in a trianglimine macrocycle crystal for ethyl acetate, an important chemical raw material and solvent. The resulting molecular crystals exhibit inherently high selectivity towards ethyl acetate, and hence can separate ethyl acetate from azeotropic mixtures with ethanol. The crystals show reasonable adsorption kinetics, good reliability after multiple adsorption cycles, and hold promise for practical separation or detection applications. More information can be found in the Full Paper by G. M. Day, M. Liu, A. I. Cooper, et al. (DOI: 10.1002/chem.202101510).

Effect of Mg2+ ions on competitive metal ions adsorption/desorption on magnesium ferrite: Mechanism, reusability and stability studies

The adsorption behavior of magnesium ferrite in single- and multicomponent metal ions solutions in the presence of Mg2+ ions were studied. A dramatic decrease in the adsorption capacity of magnesium ferrite towards Mn2+, Co2+, and Ni2+ ions for comparison study of single- and multicomponent solutions was established. The affinity of the sorbent in accordance with the maximum sorption capacities increases in the following order Cu2+ > Co2+ > Ni2+ > Mn2+. High efficiency of magnesium ferrite regeneration (~100%) with aqueous solutions of magnesium chloride in the concentration range of 0.001–0.1 M was shown. The low degree of toxic metal ions desorption combined with XRD, IR spectroscopy, and EDX analysis data indicate the key role of Mg2+ ion adsorption in the magnesium ferrite adsorbent regeneration. The positive effect of the introduction of Mg2+ ions into multicomponent solutions on metal ions adsorption was established, which is accompanied by an increase in the maximum sorption capacity for all metal ions and especially significant increase in the selectivity towards Cu2+ ions (2.41 mmol/g). The stability of the crystal structure of magnesium ferrite and a low degree of Mg2+ and Fe3+ ions leaching during multiple cycles of adsorption and regeneration of the adsorbent were observed.

Effect of modification of UiO-66 for CO2 adsorption and separation of CO2/CH4

UiO-66 and TETA/UiO-66 were synthesized by the solvothermal and impregnation methods for the study of CO2 adsorption and separation of CO2/CH4 by volumetric method. Adsorbents were characterized by X-ray diffraction (XRD), N2 adsorption-desorption isotherm (BET analyzer), FT-IR spectroscopy, Thermogravimetric analysis (TGA), Scanning electron microscopy (SEM), and elemental analysis. All characterization results have confirmed that incorporated TETA was present and occupied pores of UiO-66. High adsorption of CO2 was obtained for 25TETA/UiO-66 compared with UiO-66 by chemical interaction between CO2 and adsorbent. Along with this, a decrease in CH4 adsorption has been observed by a change in surface area and no interaction between them. The selectivity of CO2/CH4 was higher for 25TETA/UiO-66 because of the large difference in adsorption capacities of CO2 and CH4. The heat of CO2 adsorption for TETA incorporated UiO-66 was 54.6 KJ/mol at low coverage of CO2 and CO2 adsorption capacity was constant in multiple adsorption cycles.

Adsorptive desulfurization of jet fuels over TiO2-CeO2 mixed oxides: Role of surface Ti and Ce cations

A Ti0.9Ce0.1O2 oxide-based adsorbent with high surface area mesopores was studied for adsorptive desulfurization of jet fuel (JP-5: 1055 ppm-w of sulfur) using several techniques, including GC-PFPD, N2 adsorption-desorption, XRD, XPS and TPD. Ti0.9Ce0.1O2 oxide-based adsorbent effectively adsorbed sulfur and achieved the sulfur reduction of the jet fuel from 1055 ppm-w to lower than 1 ppm-w in multiple cycles of adsorption in a fixed-bed flow system. The spent adsorbent can be regenerated in-situ at the elevated temperature by using air. Some of the sulfur atom in the organic sulfur compounds could be oxidized to form sulfate species by reaction with the surface active oxygen species, while the surface (Ti4+, Ce4+) cations of adsorbent were reduced simultaneously upon adsorption of the sulfur compounds. The formed sulfate species were further removed from the surface during the oxidative regeneration step under an air flow. The deactivation of the adsorbent was potentially caused by sintering and metal cation migration on the surface.

Araucaria heterophylla resin-coated magnetic nanosorbent: a greener approach for the abatement of Mesotrione and Metsulfuron methyl herbicides

ABSTRACT The present study reports the synthesis of a green sorbent using Araucaria heterophylla resin coated on magnetic nanoparticles for the efficient abatement of herbicides; Mesotrione and Metsulfuron methyl from aqueous solution. Characterisation of the sorbent was done by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) that confirmed coated nanoparticles as small agglomerates containing various functional groups. Optimisation of pH, initial concentration and contact time were performed to achieve maximum adsorption. In addition to this, Freundlich and Langmuir isotherm models have been applied to study the adsorption behaviour of these herbicides. Maximum percentage removal of 92% and 88% for Mesotrioneand metsulfuron methyl was obtained respectively. Adsorption process followed Langmuir isotherm and q max of 18.3 mg/g (Mesotrione) and 9.3 mg/g (metsulfuron) were found. The synthesised nanoparticlesare biocompatible, cost effective and can be regenerated for multiple cycles of adsorption.

Amine functionalized magnetic nano-composite materials for the removal of selected endocrine disrupting compounds and its mechanism study

A novel adsorbent successfully synthesized using recyclable silica, nano magnetite and N1-(3 trimethoxisilylpropyl) diethylenetriamine (TRIS) denoted as MNCMT. Three endocrine disrupting compounds (EDCs) such as bisphenol A (BPA), ibuprofen (IBP) and clorofibric acid (CFA) were selected as model drugs for this study. The sorption capacities of EDCs by MNCMT were found to be 182.6 mg g−1 for BPA, followed by CFA at 101.8 mg g−1 and 72.6 mg g−1 for IBP. The removal process matched with Langmuir isotherm and pseudo second order kinetic models with determination coefficient (R2) above 0.99. The adsorbent was regenerated, recovered and reused for multiple cycles of adsorption. The physical-chemical properties and experimental data revealed that the chemical sorption is more dominant than physical sorption. Hydrogen bonding, π-π and electrostatic attractions provide intrinsic information on the removal mechanism.

Enhanced and Selective Adsorption of Zn(II), Pb(II), Cd(II), and Hg(II) Ions by a Dumbbell- and Flower-Shaped Potato Starch Phosphate Polymer: A Combined Experimental and DFT Calculation Study.

Microwave–ultrasound-assisted facile synthesis of a dumbbell- and flower-shaped potato starch phosphate (PSP) polymer, hereafter PSP, was carried out by cross-linking the hydroxyl groups of native potato starch (NPS) using phosphoryl chloride as a cross-linking agent. Structural and morphological analysis manifested the successful formation of the dumbbell- and flower-shaped PSP biosorbent with enhanced specific surface area and thermal stability. Viscoelastic behavior of NPS and PSP suggested increased rigidity in PSP, which helped the material to store more deformation energy in an elastic manner. The synthesized PSP biosorbent material was successfully tested for efficient and quick uptake of Zn(II), Pb(II), Cd(II), and Hg(II) ions from aqueous medium under competitive and noncompetitive batch conditions with qm values of 130.54, 106.25, 91.84, and 51.38 mg g–1, respectively. The adsorption selectivity was in consonance with Pearson’s hard and soft acids and bases (HSAB) theory in addition to their order of hydrated radius. Adsorption of Zn(II), Pb(II), Cd(II), and Hg(II) followed a second-order kinetics and the adsorption data fitted well with the Langmuir isotherm model. Quantum computations using density functional theory (DFT) further supported the experimental adsorption selectivity, Zn(II) > Pb(II) > Cd(II) > Hg(II), in terms of metal–oxygen binding energy measurements. What was more intriguing about PSP was its reusability over multiple adsorption cycles by treating the metal(II)-complexed PSP with 0.1 M HCl without any appreciable loss of its adsorption capacity.

Adsorption of Ag(I) ions from wastewaters using poly(2-aminothiazole): kinetic and isotherm studies

In this study, 2-aminothiazole, (2AT), was polymerized with benzoyl peroxide in 1,4-dioxane solution, and adsorption efficiencies of poly(2-aminothiazole), P-2AT, for the Ag(I) ions to remove from the aqueous solutions were investigated. Adsorption experiments were studied at different pH, contact time and initial Ag(I) ion concentration in a batch system. The optimal pH for Ag(I) adsorption onto P-2AT was found to be 5.0, and the maximum adsorption capacity was determined to be 336.98 mg/g for 1200 mg/L Ag(I) solution at 90 min. P-2AT adsorbents were followed up by recycling in multiple adsorption cycles. The results showed that adsorbent can be used several times. Ag(I) ion adsorption performance of the P-2AT was investigated in conjunction with Cu(II) and Zn(II) ions. The selectivity series of ions were found as Ag(I) > Cu(II) > Zn(II). According to the experimental data, the adsorption reaction fitted the pseudo-second-degree kinetic model and the Langmuir isotherm equation.