Isotherms and thermodynamics for the sorption of heavy metal ions onto functionalized sporopollenin

A new bodipy/pillar[5]arene functionalized magnetic sporopollenin for the detection of Cu(II) and Hg(II) ions in aqueous solution

In this study, a new bodipy/pillar[5]arene functionalized magnetic MS-Sp-P[5]-bodipy microcapsule sensor was prepared based on the use of environmentally friendly for the selective and sensitive detection of Cu(II) and Hg(II) ions in aqueous media. SEM results used in the characterization process of the materials synthesized at each stage confirmed the structural and morphological changes in the pore structure, while other characterization results (FT-IR and XRD) elucidated the role of pillar[5]arene compound and bodipy dye in the synthesis of magnetic microcapsule sensors. The colloidal solution of MS-Sp-P[5]-bodipy (water/ethanol)) showed two fluorescence bands centered at 402 and 540 nm. The detection limits of MS-Sp-P[5]-bodipy for Hg(II) and Cu(II) were calculated to be 0.06 µM and 2.27 µM, respectively (at 540 nm). The linear range of the magnetic sensor for Hg(II) and Cu(II) was found to be in the range of 1-150 µM and 10-150 µM, respectively. The experimental results (response time, pH, temperature, sensitivity and selectivity) demonstrated the applicability and potential of the prepared magnetic microcapsule sensor for the detection of Cu(II) and Hg(II) in water and tap water samples containing heavy metal ions.

Phosphogypsum-Modified Vinasse Shell Biochar as a Novel Low-Cost Material for High-Efficiency Fluoride Removal

In this study, vinasse shell biochar (VS) was easily modified with phosphogypsum to produce a low-cost and novel adsorbent (MVS) with excellent fluoride adsorption performance. The physicochemical features of the fabricated materials were studied in detail using SEM, EDS, BET, XRD, FTIR, and XPS techniques. The adsorption experiments demonstrated that the adsorption capacity of fluoride by MVS was greatly enhanced compared with VS, and the adsorption capacity increased with the pyrolysis temperature, dosage, and contact time. In comparison to chloride and nitrate ions, sulfate ions significantly affected adsorption capacity. The fluoride adsorption capacity increased first and then decreased with increasing pH in the range of 3-12. The fluoride adsorption could be perfectly fitted to the pseudo-second-order model. Adsorption isotherms matched Freundlich and Sips isotherm models well, giving 290.9 mg/g as the maximum adsorption capacity. Additionally, a thermodynamic analysis was indicative of spontaneous and endothermic processes. Based on characterization and experiment results, the plausible mechanism of fluoride adsorption onto MVS was proposed, mainly including electrostatic interactions, ion exchange, precipitation, and hydrogen bonds. This study showed that MVS could be used for the highly efficient removal of fluoride and was compatible with practical applications.

Targeting of platinum capture under 1+1 aqua regia using robust and recyclable polymeric polyamine resin: Adsorption performance and mechanism

The targeted capture of platinum from complex and harsh acidic digests such as those platinum-containing secondary resources is essential from the perspectives of green development. Here, a polyamine chelating resin (CMPs-PEI) with excellent selectivity and acid resistance was prepared by a nucleophilic substitution reaction using chloromethylated polystyrene as the parent and polyethyleneimine as the modifier. The experimental results revealed that the adsorbent showed excellent adsorption effect on platinum under different acidities, and its maximum adsorption capacity was up to 337 mg/g at pH 2. More impressively, a rather high capacity of 162.41 mg/g was achieved in 1 + 1 aqua regia (pH -0.7), which was much higher than other adsorbent materials under the same conditions. In addition, the recovery of platinum by CMPs-PEI in practical platinum-containing iron concentrate abatement solution was 100 %. Mechanistic studies showed that the protonated amine groups on CMPs-PEI bound PtCl₆^2- and partially reduced PtCl₄^2- by electrostatic attraction. Meanwhile, the excellent regeneration performance of CMPs-PEI indicated that it showed great potential for green and economic recovery of precious metal ions.

Decolorization of Rhodamine B by silver nanoparticle-loaded magnetic sporopollenin: characterization and process optimization

Silver nanoparticles (Ag NPs) were reduced on the surface of magnetic sporopollenin (Fe₃O₄@SP) modified with poly-dopamine to enhance the degradation capability for Rhodamine B (RhB). The polydopamine-coated Fe₃O₄@SP (PDA@ Fe₃O₄@SP) acts as a self-reducing agent for Ag⁺ ions to Ag⁰. The structural properties of the synthesized nanocomposite were determined using Fourier transform infrared spectrometry (FTIR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), inductively coupled plasma mass spectrometry (ICP-MS), and vibrating sample magnetometer (VSM). The systematic study of the degradation process was performed using Response Surface Methodology (RSM) to determine the relationship between the four process variables, namely, initial RhB concentration, NaBH₄ amount, catalyst amount, and time. Optimum points were determined for these four parameters using both matrix and numerical optimization methods. Under optimum conditions, RhB was decolorized with a yield of 98.11%. The apparent activation energy (E_a) and rate constant (k) for the degradation were 24.13 kJ/mol and 0.77 min^-1, respectively. The reusability studies of the Ag@PDA@Fe₃O₄@SP exhibited more than 85% degradation ability of the dye even after five cycles. As a result, Ag@PDA@Fe₃O₄@SP possessed high catalytic activity, fast reduction rate, good reusability, easy separation, and simple preparation, endowing this catalyst to be used as a promising catalyst for the decolorization of dyes in aqueous solutions.

Sporopollenin based materials as a versatile choice for the detoxification of environmental pollutants - A review

Before making the transfer to land, plants survive in water for millions of years to avoid the severe circumstances that prevail on lands, such as drought and UV radiation. All land plant spores are coated in sporopollenin, a substance that has developed to endow pollen and spore shells with exceptional, one-of-a-kind qualities. In a nutshell, sporopollenin-coated spores are a unique invention only seen in land plants. Sporopollenin, discovered in the outer exine layer of pollen walls, is a lipid and phenolic-based polymer with high carbon, hydrogen, and oxygen cross-linking. Products based on sporopollenin can remediate toxic pollutant contamination in the aquatic environment. This research and development are now underway. In this review, we show how sporopollenin-based adsorbents act in environmental challenges and their immense promise for this application via remarkable physical and chemical characteristics. A comparison is made of the benefits of various sporopollenin-modified structures. This strategy will further our understanding of how a biopolymer's structure can be accommodated to address emerging environmental challenges, revealing more about sporopollenin's dynamical nature.

Fe-functionalized paramagnetic sporopollenin from pollen grains: one-pot synthesis using ionic liquids

The preparation of Fe-decorated sporopollenins was achieved using pollen grains and an ionic liquid as solvent and functionalizing agent. The integrity of the organic capsules was ascertained through scanning electron microscopy studies. The presence of Fe in the capsule was investigated using FT-IR, X-ray photoemission spectroscopy and energy-dispersive X-ray spectroscopy. Electron paramagnetic resonance and magnetization measurements allowed us to demonstrate the paramagnetic behavior of our Fe-functionalized sporopollenin. A few potential applications of pollen-based systems functionalized with magnetic metal ions via ionic liquids are discussed.

New effective 3-aminopropyltrimethoxysilane functionalized magnetic sporopollenin-based silica coated graphene oxide adsorbent for removal of Pb(II) from aqueous environment

A new effective adsorbent, 3-aminopropyltrimethoxysilane functionalized magnetic sporopollenin (MSp@SiO₂NH₂) based silica-coated graphene oxide (GO), (GO@SiO₂-MSp@SiO₂NH₂) was successfully synthesized and applied for the first time in the removal of hazardous Pb(II) ions from aqueous solution. The properties of the composite were characterized using Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX) and vibrating-sample magnetometery (VSM). Evaluation of GO@SiO₂-MSp@SiO₂NH₂ adsorption performance at optimum conditions revealed that the adsorbent has a maximum adsorption capacity of 323.5 mg/g for Pb(II) using 50-200 mg/L initial Pb(II) ions concentrations. Initial and final concentrations of Pb(II) ions in aqueous solution were analyzed using graphite furnace atomic absorption spectroscopy (GF-ASS). The adsorption behavior of Pb(II) ions onto GO@SiO₂-MSp@SiO₂NH₂ was studied using Langmuir, Freundlich and Temkin isotherms models. The values of coefficient of determination showed that the adsorption best fitted the Langmuir model (R² = 0.9994). Kinetic studies suggested that the adsorption of Pb(II) ion followed a pseudo-second-order rate model (R² = 1.00) and thermodynamic studies revealed that the adsorption process is endothermic and spontaneous. The effect of co-existing ions on Pb(II) ion adsorption were also studied and found to have considerable effects only at higher matrix concentration. The adsorbent can be reused up to ten times and retain its good adsorption capacity. In addition, GO@SiO₂-MSp@SiO₂NH₂ showed great potential for Pb(II)removal from industrial wastewater samples.

Removal of chromium(vi) from polluted wastewater by chemical modification of silica gel with 4-acetyl-3-hydroxyaniline

In the current study, a new adsorbent that is insoluble in water and many acid solutions and has a high adsorption capacity for Cr(vi) metal ions was synthesized. In the synthesis process, 3-chloropropyl-trimethoxysilane (CPTS) was first modified on a silica gel (Si) surface. Secondly, 4-acetyl-3-hydroxyaniline (AHAP) was immobilized on the modified silica gel compound (Si-CPTS). As a result of the immobilization process, a new adsorbent compound named Si-CPTS-AHAP (silica gel-3-chloropropyltrimethoxy silane 4-acetyl-3-hydroxyaniline) was obtained, which was used to separate Cr(vi) ions from aqueous solution (K₂Cr₂O₇) and industrial wastewater. The material was characterized using scanning electron microscopy and Fourier-transform infrared spectroscopy. The amount of chromium adsorbed was detected by ultraviolet-visible spectroscopy. The adsorption was evaluated using batch methods. The effects of temperature, pH, concentration, adsorbent amount and interaction time on the adsorption of Si-CPTS-AHAP were also investigated. The adsorption of Cr(vi) ions on Si-CPTS-AHAP was investigated via adsorption kinetics, isotherm and thermodynamic studies. The value of the isotherm parameters and the highest adsorption yields were calculated from the Dubinin–Radushkevich, Freundlich and Langmuir isotherm equations. Thermodynamic features such as entropy (ΔS), enthalpy (ΔH) and free energy (ΔG) were also calculated from the experimental results. The experimental results showed that the best recoveries of Cr(vi) metal ions are under the conditions of 180 min (interaction time), 0.05 g (adsorbent amount) and 323.15 K (temperature) at pH 2. Si-CPTS-AHAP can be used for the removal of poisonous pollutants in wastewater.

Use of a newly synthesized Si-CPTS-AHAP adsorbent in the removal of Cr(vi) ions in wastewater treatment systems may potentially lead to low cost and highly efficient heavy metal removal.

Magnetite-sporopollenin/graphene oxide as new preconcentration adsorbent for removal of polar organophosphorus pesticides in vegetables

In this study, a new magnetic adsorbent based on magnetite-sporopollenin/graphene oxide (Fe₃O₄-SP/GO) was successfully developed. The adsorbent was applied for magnetic solid phase extraction (MSPE) of three selected polar organophosphorus pesticides (OPPs), namely, dimethoate, phenthoate, and phosphamidon, prior to gas chromatography analysis with electron capture detection (GC-μECD). The Fe₃O₄-SP/GO adsorbent combines the advantages of superior adsorption capability of the modified sporopollenin (SP) with graphene oxide (GO) and magnetite (Fe₃O₄) for easy isolation from sample solution. Several MSPE parameters were optimized. Under optimized conditions, excellent linearity (R² ≥ 0.9994) was achieved using matrix match calibration in the range of 0.1 to 500 ng mL^-1. The limit of detection (LOD) method (S/N = 3) was from 0.02 to 0.05 ng mL^-1. The developed Fe₃O₄-SP/GO MSPE method was successfully applied for the determination of these three polar OPPs in cucumber, long beans, bell pepper, and tomato samples. Good recoveries (81.0-120.0%) and good relative standard deviation (RSD) (1.4-7.8%, n = 3) were obtained for the spiked OPPs (1 ng mL^-1) from real samples. This study is beneficial for adsorptive removal of toxic pesticide compounds from vegetable samples.

Novel Phenanthrene Sorption Mechanism by Two Pollens and Their Fractions

A pair of pollens (Nelumbo nucifera and Brassica campestris L.) and their fractions were characterized by elemental analysis and advanced solid-state (13)C NMR techniques and used as biosorbents for phenanthrene (Phen). Their constituents were largely aliphatic components (including sporopollenin), carbohydrates, protein, and lignin as estimated by (13)C NMR spectra of the investigated samples and the four listed biochemical classes. The structure of each nonhydrolyzable carbon (NHC) fraction is similar to that of sporopollenin. The sorption capacities are highly negatively related to polar groups largely derived from carbohydrates and protein but highly positively related to alkyl carbon, poly(methylene) carbon, and aromatic carbon largely derived from sporopollenin and lignin. The sorption capacities of the NHC fractions are much higher than previously reported values, suggesting that they are good sorbents for Phen. The Freundlich n values significantly decrease with increasing concentrations of poly(methylene) carbon, alkyl C, aromatic moieties, aliphatic components, and the lignin of the pollen sorbents, suggesting that aliphatic and aromatic structures and constituents jointly contribute to the increasing nonlinearity. To our knowledge, this is the first investigation of the combined roles of alkyl and aromatic moiety domains, composition, and accessibility on the sorption of Phen by pollen samples.