Simultaneous Adsorption and Reduction of Cr(VI) to Cr(III) in Aqueous Solution Using Nitrogen-Rich Aminal Linked Porous Organic Polymers

Polyaniline-Based Cationic Porous Organic Polymers for Fast and Efficient Anion-Exchange-Driven Capture of Cr2O7 2

Efficient treatment of wastewater contaminated with carcinogenic Cr(VI) has been a long-term challenge for both academic and industrial research efforts. Removal of Cr(VI) species by ion exchange is a relatively simple and efficient method, and its combination with highly tailorable nanomaterials is promising for the treatment of such wastewater. Here, we report a type of cationic porous organic polymer (POP), namely, PTPA-PIP, which can be prepared simply by converting the corresponding aromatic polyamine PTPA to its protonated form, thereby significantly increasing its hydrophilicity and ability to disperse homogeneously in water, crucial for application in water treatment. In addition to detailed characterization of the physicochemical properties of PTPA-PIP (including using Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), and solid-state NMR techniques), adsorption experiments demonstrate that PTPA-PIP removes low-concentration dichromate anions with very high performance, including excellent exchange capacity (maximum capacity of 230 mg Cr2O7 2-/g PTPA-PIP), ultrafast removal (initial adsorption rate of 83 mg g-1 min-1), excellent selectivity (∼10% loss of adsorption capacity in the presence of 40-fold concentration of competing anions), as well as superior reusability (reusable for at least 5 cycles without compromised performance). These results demonstrate that PTPA-PIP is an outstanding candidate for application in industrial settings for the effective removal of harmful Cr(VI) pollutants in wastewater.

Schiff-base Polymer Immobilized Ruthenium for Efficient Catalytic Cross-coupling of Secondary Alcohols with 2-amino- and γ-aminobenzyl Alcohols to Give Quinolines and Pyridines

A Schiff-base porous polymer has been impregnated with ruthenium trichloride for acceptor-free dehydrogenation coupling (ADC) of secondary alcohols with γ-amino- and 2-aminobenzyl alcohols to give pyridines and quinolines. This heterogenous catalyst exhibited high catalytic efficiency over repeated cycles with wide functional group tolerance.

Chromium removal at neutral pHs via electrochemical Cr(VI) reduction and subsequent Cr(III) adsorption with MoS2 nanoflowers-modified graphite felt

The operation performance and stability of electrochemical Cr(VI) reduction are strongly restricted at neutral pHs (e.g., drinking water and groundwater) by the high Cr(VI) oxidation potentials and cathode passivation of Cr(OH)₃ precipitates. Herein, we fabricated MoS₂ nanoflowers-modified graphite felt (GF-MoS₂) to construct the electrochemical apparatus (EA) and adsorption column (AC), attempting to stable and effective Cr(VI) removal at neutral pHs via electrochemical Cr(VI) reduction and subsequent Cr(III) adsorption. In EA with a sequential oxidation-reduction process, Cr(VI)-contaminated influent (5 mg/L) at neutral pHs (6.0-8.0) was oxidized first by anode to generate large amounts of H⁺ ions via H₂O oxidation, decreasing the pH of anode-oxidized influent to ∼2.5 at 2.6 V and 1000 L/m²/h. Subsequently, the acidic anode-oxidized influent was further reduced by GF-MoS₂ cathode, promoting significantly Cr(VI) reduction via decreasing Cr(VI) oxidation potentials and alleviating Cr(III) precipitation on cathode. These results enabled the stable and effective operation of GF-MoS₂-based EA with almost Cr(VI) reduction to Cr(III). With further assembling GF-MoS₂-based AC, Cr(III) species in EA effluent were easily adsorbed or intercepted by GF-MoS₂, achieving undetectable Cr species in AC effluent. Combination techniques of GF-MoS₂-based electrochemical reduction and adsorption can be an effective approach for remediating Cr(VI)-contaminated water at neutral pHs.

A Core-Shell Amino-Functionalized Magnetic Molecularly Imprinted Polymer Based on Glycidyl Methacrylate for Dispersive Solid-Phase Microextraction of Aniline

A core-shell amino-functionalized glycidyl methacrylate magnetic molecularly imprinted polymer (MIP) was synthesized by the suspension polymerization/surface imprinting method and characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), mercury porosimetry, nitrogen gas adsorption–desorption, and elemental analysis. This MIP was used as the sorbent in dispersive solid-phase microextraction (DSPME) of aniline from textile wastewater prior to high-performance liquid chromatography-mass spectrometry (HPLC-MS) measurements. Since aniline is toxic and a probable human carcinogen, its determination in water is of great significance. This is a challenging task because aniline is usually present at trace levels. The effects of different DSPME variables on the preconcentration efficiency have been studied by using the Plackett–Burman screening design of experiments (DoE) followed by response surface methodology optimization using the Box-Behnken design. Thus, DoE enabled the investigation of several variables simultaneously. Under optimized conditions, aniline was effectively and selectively separated by a small amount of the DSPME sorbent and detected in real textile wastewater samples. The method detection limit of 1 ng mL−1 was attained, with good method linearity and acceptable recovery and precision. The results showed that the studied MIP could be a reliable DSPME sorbent for efficiently analyzing trace aniline in real wastewater samples.

Triazine-based porous organic polymers for reversible capture of iodine and utilization in antibacterial application

The capture and safe storage of radioactive iodine (¹²⁹I or ¹³¹I) are of a compelling significance in the generation of nuclear energy and waste storage. Because of their physiochemical properties, Porous Organic Polymers (POPs) are considered to be one of the most sought classes of materials for iodine capture and storage. Herein, we report on the preparation and characterization of two triazine-based, nitrogen-rich, porous organic polymers, NRPOP-1 (SA_BET = 519 m² g⁻¹) and NRPOP-2 (SA_BET = 456 m² g⁻¹), by reacting 1,3,5-triazine-2,4,6-triamine or 1,4-bis-(2,4-diamino-1,3,5-triazine)-benzene with thieno[2,3-b]thiophene-2,5-dicarboxaldehyde, respectively, and their use in the capture of volatile iodine. NRPOP-1 and NRPOP-2 showed a high adsorption capacity of iodine vapor with an uptake of up to 317 wt % at 80 °C and 1 bar and adequate recyclability. The NRPOPs were also capable of removing up to 87% of iodine from 300 mg L⁻¹ iodine-cyclohexane solution. Furthermore, the iodine-loaded polymers, I₂@NRPOP-1 and I₂@NRPOP-2, displayed good antibacterial activity against Micrococcus luteus (ML), Escherichia coli (EC), and Pseudomonas aeruginosa (PSA). The synergic functionality of these novel polymers makes them promising materials to the environment and public health.

Highly Efficient Visible Light Photodegradation of Cr(VI) Using Electrospun MWCNTs-Fe3O4@PES Nanofibers

The development of highly efficient photocatalysis has been prepared by two different methods for the photodegradation of Cr(VI) from an aqueous solution under visible light. The electrospun polyethersulfone (PES)/iron oxide (Fe3O4) and multi-wall carbon nanotubes (MWCNTs) composite nanofibers have been prepared using the electrospinning technique. The prepared materials were characterized by SEM and XRD analysis. The result reveals the successful fabrication of the composite nanofiber with uniformly and smooth nanofibers. The effect of numerous parameters were explored to investigate the effects of pH value, contact time, concentration of Cr(VI), and reusability. The MWCNTs-Fe3O4@PES composite nanofibers exhibited excellent photodegradation of Cr(VI) at pH 2 in 80 min. The photocatalysis materials are highly stable without significant reduction of the photocatalytic efficiency of Cr(VI) after five cycles. Therefore, due to its easy separation and reuse without loss of photocatalytic efficiency, the photocatalysis membrane has tremendous potential for the removal of heavy metals from aqueous solutions.

Innovative Magnetite Based Polymeric Nanocomposite for Simultaneous Removal of Methyl Orange and Hexavalent Chromium from Water

One of the most important directions for environmental remediation is the effective removal of dyes and toxic heavy metals from water using newly fabricated nanoadsorbents. Here, magnetic Fe3O4 nanoparticles were combined with nitrogen-containing functional group polymers chitosan (CS) and polypyrrole (ppy) to synthesize a nanocomposite (polypyrrole@magnetic chitosan) useful for removing methyl orange (MO) and hexavalent chromium (Cr (VI)) from water. The physicochemical properties of the nanocomposite were determined using SEM, TEM, XRD, FT–IR, and TGA techniques. The effect of different factors on the adsorption system was studied including the contact time, pH, and the effect of co-existed ions. The kinetic study illustrated that the adsorption fit well with Langmuir isotherm. The maximum adsorption capacity of MO and Cr (VI) was found to be 95 and 105 mg/g, respectively. The reusability of the nanocomposite was studied for up to five cycles using 0.1 M NaOH as eluent with a slight decrease of adsorbent efficiency. Furthermore, the removal mechanism studied suggested the removal of MO via adsorption and Cr (VI) via chemical reduction and adsorption. This study suggests that a ppy@magnetic chitosan nanocomposite is a promising nanoadsorbent for removing MO and Cr (VI) from water.