Highly Efficient Magnetic Nitrogen-Doped Porous Carbon Prepared by One-Step Carbonization Strategy for Hg2+ Removal from Water

Thioether-functionalized porous β-cyclodextrin polymer for efficient removal of heavy metal ions and organic micropollutants from water

Herein, a thioether-functionalized porous β-cyclodextrin polymer (P(Bn-S-CD)) was prepared for efficient removal of heavy metal ions and organic micropollutants (OMPs) from water. P(Bn-S-CD) showed a surface area of 763 m2/g and a sulfur content 5.83 wt%. Based on screening studies, Hg2+ and diclofenac sodium (DS) were selected as model pollutants. P(Bn-S-CD) could adsorb Hg2+ and DS simultaneously, while the adsorbed Hg2+ afforded positive charges to the primary rims of CDs, greatly enhancing the adsorption rate and adsorption capacity of DS. Although the adsorbed DS showed no obvious effect on Hg2+ adsorption, it improved the affinity of Hg2+ upon P(Bn-S-CD). Adsorption mechanism studies confirmed the essential role of electrostatic interactions for these results. P(Bn-S-CD) also showed good selectivity towards heavy metal ions, excellent adsorption performance in real water at environmental levels and good reusability, implying great promise for water treatment.

Magnetic sulfur-doped carbons for mercury adsorption

Mercury pollution is a significant threat to the environment and health worldwide. Therefore, effective and low-cost absorbents that are easily scalable are needed for real-world applications. Enlarging the surface area of the materials and doping with heteroatoms are two of the most common strategies to cope with this problem. Sulfur-doped activated carbon synthesized from the carbonization of inverse vulcanized thiopolymers makes it possible to combine both large specific surface area and doping of heteroatoms, resulting in outperformance in mercury uptake against commercial activated carbons. Convenient recovery of mercury absorbents after treatment should be beneficial in mercury collecting and recycling. Therefore, magnetic sulfur-doped carbons (MSCs) were prepared by functionalizing sulfur doped carbons through chemical precipitation with magnetic iron oxides. Besides the characterisations of materials, mercury uptake experiments, such as stactic test, capacity test, impact of solution pH, and mixed ions interferences were performed. These MSCs exhibit high specific surface area (1,329 m²/g), high sulfur content (up to 14.8 wt%), porous structure, low cost, and are convenient for retrieval. MSCs are demonstrated high uptake capacity (187 mg g^-1) and efficiency in mercury solution and multifunctional absorption in mixed ions solution, showing their potential to be applied in water purification and environmental remediation.

Porous BMTTPA-CS-GO nanocomposite for the efficient removal of heavy metal ions from aqueous solutions

In this study, a stable, cost-effective and environmentally friendly porous 2,5-bis(methylthio)terephthalaldehyde-chitosan-grafted graphene oxide (BMTTPA-CS-GO) nanocomposite was synthesized by covalently grafting BMTTPA-CS onto the surfaces of graphene oxide and used for removing heavy metal ions from polluted water. According to well-established Hg2+-thioether coordination chemistry, the newly designed covalently linked stable porous BMTTPA-CS-GO nanocomposite with thioether units on the pore walls greatly increases the adsorption capacity of Hg2+ and does not cause secondary pollution to the environment. The results of sorption experiments and inductively coupled plasma mass spectrometry measurements demonstrate that the maximum adsorption capacity of Hg2+ on BMTTPA-CS-GO at pH 7 is 306.8 mg g-1, indicating that BMTTPA-CS-GO has excellent adsorption performance for Hg2+. The experimental results show that this stable, environmentally friendly, cost-effective and excellent adsorption performance of BMTTPA-CS-GO makes it a potential nanocomposite for removing Hg2+ and other heavy metal ions from polluted water, and even drinking water. This study suggests that covalently linked crucial groups on the surface of carbon-based materials are essential for improving the adsorption capacity of adsorbents for heavy metal ions.

Adsorptive removal of pharmaceuticals from water using metal-organic frameworks: A review

Pharmaceutical pollution has emerged as a highly concerned issue due to its adverse effects. Elevated concentrations of pharmaceuticals in water should be regulated to satisfy the requirement for the provision of clean water. Metal-organic frameworks (MOFs) with high specific surface area, controllable porous structure, and facile modification can serve as promising adsorbents for the removal of pharmaceutical contaminants from water. In this review, a selected collection illustrating the reliable strategies and concepts to prepare the MOFs-based materials with superior water stability is described. In addition, recent progress on the adsorptive removal of pharmaceutical pollutant using burgeoning and functional MOFs is also summarized in terms of maximum capacity, equilibrium time, and regenerate ability. Meanwhile, to understand the adsorption mechanism, related interactions including coordination with unsaturated site, pore-filling effect, hydrogen bonding, electrostatic, and π-π stacking are further discussed. Finally, critical perspectives/assessment of future research emphasising on fabricating desirable MOFs and establishing structure-property relationships to facilitate capture performance are identified.

High adsorption capacity and super selectivity for Pb(Ⅱ) by a novel adsorbent: Nano humboldtine/almandine composite prepared from natural almandine

This study firstly reported a novel nano humboldtine/almandine composite (NHLA composite) prepared directly from almandine through one-pot method based on the interaction of almandine and oxalic acid. The formation of humboldtine/almandine binary phase from natural almandine was determined by X-ray diffraction. Analysis of scanning & transmission electron microscope showed that large amount of nano humboldtine with uniform size (average size of 15.59 nm) were loaded on the almandine sheets. Compared with raw minerals, Pb(Ⅱ) removal capacity of synthesized composite was significantly increased, demonstrating that the main active ingredient for Pb(Ⅱ) removal was humboldtine phase rather than almandine itself. Pb(Ⅱ) adsorption capacity was increased with the increasing of initial pH value or temperature. Langmuir isotherm and Pseudo-second order kinetic equation were well fitted with experimental results and the maximum Pb(Ⅱ) adsorption capacity from Langmuir isotherm was 574.71 mg/g at temperature of 25 °C. In addition, heavy metal removal experiments in coexisting systems of multiple heavy metal ions manifested that the composite had a high selectivity for Pb(Ⅱ) adsorption. Ion exchange, surface complexation and electrostatic interaction have involved in the Pb(Ⅱ) adsorption. The synthesized composite was considered as a low cost, high efficiency, super selectivity and easy to mass production material for Pb(Ⅱ) adsorption from solution.

Engineering magnetic N-doped porous carbon with super-high ciprofloxacin adsorption capacity and wide pH adaptability

We report a high performance magnetic N-doped nanoporous carbon (MNPC) adsorbent synthesized by a simple single-step pyrolysis protocol. Grinding the mixture of ZnO nanoparticles, cobalt hydroxide and 2-methylimidazole produced Zn/Co-ZIFs that were converted into MNPC following subsequent pyrolysis in N₂ atmosphere. The optimized MNPC-700-0.4 adsorbent, obtained at 700 °C with Co/(Zn + Co) molar ratio of 0.4, is featured with super-high ciprofloxacin (CIP) adsorption capacity of 1563.7 mg g^-1 at 25 °C, fast adsorption dynamics (1.5 h of adsorption equilibrium time), wide pH adaptability (almost unchanged CIP adsorption capacity in pH 4-10), and good magnetic property. The magnetic property and CIP adsorption performance can be easily regulated by modulating the molar ratio of Co/(Zn + Co) and the pyrolysis temperature. The optimal MNPC-700-0.4 was chosen to explore adsorption kinetics and isotherm. The effects of pH, ionic strength and humic acid on CIP adsorption were investigated. CIP adsorption obeyed pseudo-second-order kinetics and well fitted the Langmuir adsorption model. The favorable textural properties (high surface area and pore volume), riched nitrogen structure and large amounts of defects endow the MNPC-700-0.4 lots of sites for CIP adsorption. The CIP adsorption onto MNPC-700-0.4 was mainly controlled by the electrostatic interaction, hydrophobic interaction, π-π stacking and hydrogen bond.

Remediation of mercury contaminated soil, water, and air: A review of emerging materials and innovative technologies

Mercury contamination in soil, water and air is associated with potential toxicity to humans and ecosystems. Industrial activities such as coal combustion have led to increased mercury (Hg) concentrations in different environmental media. This review critically evaluates recent developments in technological approaches for the remediation of Hg contaminated soil, water and air, with a focus on emerging materials and innovative technologies. Extensive research on various nanomaterials, such as carbon nanotubes (CNTs), nanosheets and magnetic nanocomposites, for mercury removal are investigated. This paper also examines other emerging materials and their characteristics, including graphene, biochar, metal organic frameworks (MOFs), covalent organic frameworks (COFs), layered double hydroxides (LDHs) as well as other materials such as clay minerals and manganese oxides. Based on approaches including adsorption/desorption, oxidation/reduction and stabilization/containment, the performances of innovative technologies with the aid of these materials were examined. In addition, technologies involving organisms, such as phytoremediation, algae-based mercury removal, microbial reduction and constructed wetlands, were also reviewed, and the role of organisms, especially microorganisms, in these techniques are illustrated.

Unprecedented Selectivity and Rapid Uptake of CuS Nanostructures toward Hg(II) Ions

Fast, selective, and effective enrichment is critical for onsite detection and online monitoring of extremely low-concentration toxic heavy metal ions in complex environmental samples. In the current work, varied CuS nanostructures (hollow nanospheres, nanoflowers, nanoparticles) were prepared and applied to the enrichment of Hg(II) ions. Surprisingly, the as-prepared CuS nanostructures exhibited unprecedented ultrahigh selectivity and rapid uptake toward Hg(II) ions in the presence of other seven metal ions, suggesting specificity of mercury enrichment by the CuS nanostructures. Upon treating a 100 mL aqueous sample containing 8 different metal ions with only 10 mg of CuS hollow nanospheres, over 99.5% of Hg(II) ions could be removed within just 1 min, achieving a final Hg(II) ion level down to 0.1 ppb. This excellent selectivity was well accounted for by the Hard Soft Acid Base theory and especially the solubility product constant, where the solubility product constant of CuS is higher than that of HgS but lower than that of sulfides of other interfering metal ions. The current results are striking and would open a new avenue to the search for highly selective and efficient absorptive nanomaterials toward varied heavy metal ions.

Heteroatom-doped magnetic hydrochar to remove post-transition and transition metals from water: Synthesis, characterization, and adsorption studies

Efforts to improve water quality have led to the development of green and sustainable water treatment approaches. Herein, nitrogen-doped magnetized hydrochar (mSBHC-N) was synthesized, characterized, and used for the removal of post-transition and transition heavy metals, viz. Pb²⁺ and Cd²⁺ from aqueous environment. mSBHC-N was found to be mesoporous (BET surface area - 62.5 m²/g) and paramagnetic (saturation magnetization - 44 emu/g). Both, FT-IR (with peaks at 577, 1065, 1609 and 3440 cm^-1 corresponding to Fe - O stretching vibrations, C - N stretching, N - H in-plane deformation and stretching) and XPS analyses (with peaks at 284.4, 400, 530, 710 eV due to C 1s, N 1s, O 1s, and Fe 2p) confirmed the presence of oxygen and nitrogen containing functional groups on mSBHC-N. The adsorption of Pb²⁺ and Cd²⁺ was governed by oxygen and nitrogen functionalities through electrostatic and co-ordination forces. 75-80% of Pb²⁺ and Cd²⁺ adsorption at C_o: 25 mg/L, either from deionized water or humic acid solution was accomplished within 15 min. The data was fitted to pseudo-second-order kinetic and Langmuir isotherm models, with maximum monolayer adsorption capacities being 323 and 357 mg/g for Cd²⁺and Pb²⁺ at 318 K, respectively. Maximum Cd²⁺ (82.6%) and Pb²⁺ (78.7%) were eluted with 0.01 M HCl, simultaneously allowing minimum iron leaching (2.73%) from mSBHC-N. In conclusion, the study may provide a novel, economical, and clean route to utilize agro-waste, such as sugarcane bagasse (SB), for aquatic environment remediation.

Metallophthalocyanine-Based Molecular Dipole Layer as a Universal and Versatile Approach to Realize Efficient and Stable Perovskite Solar Cells

It is well known that tailoring the interfacial structure is very important for perovskite solar cells, especially for its performance and stability. Here, we report a universal and versatile method of modulating the energetic alignment between the perovskite and hole-transporting layer by introducing a multifunctional dipole layer based on metallophthalocyanine derivatives copperphthalocyanine (CuPc) or highly fluorinated copper hexadecafluorophthalocyanine (F₁₆CuPc). Both molecules were introduced through an "antisolution" process to treat the surface of organic-inorganic CH₃NH₃PbI₃ perovskite. The dipole layer can well align the interfacial energy levels, passivate the CH₃NH₃PbI₃ surface, and fill the grain boundaries, resulting in greatly suppressed charge recombination. As a result, our planar CH₃NH₃PbI₃ perovskite devices exhibit the best power conversion efficiency of 20.2%, with significantly enhanced open-circuit voltages ( V_oc) of 1.112 V (CuPc) and 1.145 V (F₁₆CuPc), which is a record high V_oc value for CH₃NH₃PbI₃ thin-film solar cells. More importantly, the use of highly fluorinated F₁₆CuPc produces a significantly more hydrophobic surface, leading to drastically improved long-term stability under ambient conditions. We believe that our study offers a general approach to making multifunctional dipole layers, which are necessary for achieving both stable and efficient perovskite solar cells.

A superfast hexavalent chromium scavenger: Magnetic nanocarbon bridged nanomagnetite network with excellent recyclability

In this work, a nanocarbon bridged nanomagnetite network (NC-NMN) is developed through the electrospinning of epichlorohydrin functionalized polystyrene (f-PS), followed by the direct calcination of f-PS and ferric nitrate, which is capable of superfast removing hexavalent chromium (Cr(VI)) from polluted water within only 15 s benefiting from its gridding framework, with an adsorption rate constant of 1.64 g mg^-1 min^-1 according to the pseudo-second-order kinetics. The well-fitted Langmuir isotherm model indicates a monolayer adsorption for Cr(VI) on NC-NMN. The thermodynamic parameters including negative ΔG° and positive ΔH° demonstrate that the Cr(VI) adsorption on NC-NMN is spontaneous and endothermic. The Cr(VI) adsorption retention, which is only 3.8%, is achieved for NC-NMN after five cycles, exhibiting a prominent stability and an excellent recyclability. X-ray photoelectron spectroscopy (XPS), zeta potential and energy-filter transmission electron spectroscopy (EFTEM) results illustrate that both the electrostatic attraction and the network structure of NC-NMN are responsible for the superior Cr(VI) adsorption performance. This work intends to provide a new method for designing the novel structure materials for polluted water treatment.

Fabrication of multi-functional porous microspheres in a modular fashion for the detection, adsorption, and removal of pollutants in wastewater

Water pollution control has become significant challenges in recent years because of their extensive species diversity. It is critical to developing general-purpose materials for environmental rehabilitation. In this paper, a novel module-assembly method is developed to prepare multi-functional materials for treating pollutants in water. Building blocks are porous nanoparticles with a different function. Microspheres (MS) with a diameter of 90 μm are prepared and have a coefficient of variation of 6.8%. The modular fashion of self-assembly process in a microfluidic chip is the crucial factor in fabricating the multifunction material. The assembled microspheres with different building modules still have a specific surface area larger than 400 m² g^-1, and exhibit excellent performance in adsorbing various pollutants in water, such as heavy metal ions and organic dyes. The adsorption capacities of them to Hg²⁺ and orange II reach 150 mg g^-1 and 333 mg g^-1, respectively. The integrated fluorescence probes in microspheres can detect low concentration (9.8 ppb) of Hg²⁺. Microspheres integrated with Fe₃O₄ nanoparticles have a magnetic susceptibility of 6.01 emu g^-1 and can be easily removed from wastewater by applying an external magnetic. Due to the stability of inorganic building blocks, each function in the assembled system is well performed, and multi-functional "All-in-One" materials can be easily fabricated.

Sulfur-rich covalent triazine polymer nanospheres for environmental mercury removal and detection

We describe a facile one-pot synthesis of porous covalent sulfide-bridged polytriazine nanospheres (NOP-28), which can be employed as highly efficient sorbents and at the same time act as selective sensitive sensors towards trace Hg²⁺.

Supercritical CO2 assisted synthesis of sulfur-modified zeolites as high-efficiency adsorbents for Hg2+ removal from water

A facile supercritical CO₂ (SC-CO₂) synthetic strategy has been successfully developed for fabricating a new kind of highly efficient sulfur-modified zeolite sorbent for the removal of Hg²⁺ from water.

Efficient Removal of Heavy Metals from Polluted Water with High Selectivity for Mercury(II) by 2-Imino-4-thiobiuret-Partially Reduced Graphene Oxide (IT-PRGO)

A novel chelating adsorbent, based on the chemical modification of graphene oxide by functionalization amidinothiourea to form 2-imino-4-thiobiuret-partially reduced graphene oxide (IT-PRGO), is used for the effective extraction of the toxic metal ions Hg(II), Cu(II), Pb(II), Cr(VI), and As(V) from wastewater. FTIR and Raman spectroscopy, XRD, and XPS confirm the successful incorporation of the amidinothiourea groups within the partially reduced GO nanosheets through nucleophilic substitution reactions with the acyl chloride groups in the chemically modified GO. The IT-PRGO adsorbent shows exceptional selectivity for the extraction of Hg(II) with a capacity of 624 mg/g, placing it among the top of carbon-based materials known for the high capacity of Hg(II) removal from aqueous solutions. The maximum sorption capacities for As(V), Cu(II), Cr(VI), and Pb(II) are 19.0, 37.0, 63.0, and 101.5 mg/g, respectively. The IT-PRGO displays a 100% removal of Hg(II) at concentrations up to 100 ppm with 90%, 95%, and 100% removal within 15, 30, and 90 min, respectively, at 50 ppm concentration. In a mixture of six heavy metal ions containing 10 ppm of each ion, the IT-PRGO shows a removal of 3% Zn(II), 4% Ni(II), 9% Cd(II), 21% Cu(II), 63% Pb(II), and 100% Hg(II). A monolayer adsorption behavior is suggested based on the excellent agreement of the experimental sorption isotherms with the Langmuir model. The sorption kinetics can be fitted well to a pseudo-second-order kinetic model which suggests a chemisorption mechanism via the amidinothiourea groups grafted on the reduced graphene oxide nanosheets. Desorption studies demonstrate that the IT-PRGO is easily regenerated with the desorption of the metal ions Hg(II), Cu(II), Pb(II), Cr(VI), and As(V) reaching 96%, 100%, 100%, 96%, and 100%, respectively, from their maximum sorption capacities using different eluents. The IT-PRGO is proposed as a top performing remediation adsorbent for the extraction of heavy metals from waste and polluted water.

Iron Nanoclusters as Template/Activator for the Synthesis of Nitrogen Doped Porous Carbon and Its CO2 Adsorption Application

We propose a facile synthesis approach for nitrogen doped porous carbon and demonstrate a novel pore-forming method that iron nanoclusters act as a template or activator at different carbonization temperatures based on Fe³⁺-poly(4-vinyipyridine) (P4VP) coordination. P4VP will completely decompose even in an inert atmosphere, but under the coordination and catalysis of Fe³⁺, it can be converted to carbon at a very low temperature (400 °C). The aggregation of iron nanoclusters in the carbonization process showed different pore-forming methods at different temperatures. The as-prepared materials possess high specific surface area (up to 1211 m² g^-1), large pore volume (up to 0.96 cm³ g^-1), narrow microporosity, and high N content (up to 9.9 wt %). Due to these unique features, the materials show high CO₂ uptake capacity and excellent selectivity for CO₂/N₂ separation. The CO₂ uptake capacity of NDPC-2-600 is up to 6.8 and 4.3 mmol g^-1 at 0 and 25 °C; the CO₂/N₂ (0.15/0.85) selectivity at 0 and 25 °C also reaches 18.4 and 15.2, respectively.

Magnetic sulfur-doped porous carbon for preconcentration of trace mercury in environmental water prior to ICP-MS detection

A novel magnetic sulfur-doped porous carbon (MSPC) was fabricated via a simple one-step carbonization of a mixture of sucrose, basic magnesium sulfate whiskers and Fe₃O₄@SiO₂ nanoparticles.