Adsorption of phenolic compounds from water by a novel ethylenediamine rosin-based resin: Interaction models and adsorption mechanisms

Investigating the adsorption processes of polymer resins for the removal of micropollutants: A comprehensive review in the field of environmental remediation

The growing worry for human health stems from the fact that micropollutants (MPs), particularly dyes, are more common in aquatic settings. These particles pose a serious risk to both humans and animals since they have been found in a variety of bodily fluids and waste products from both humans and animals. MPs pose significant dangers to human health and other living things due to their extended half-lives, high fragmentation propensity, and capacity to absorb organic pollutants as well (MB, MR, MO and CV dyes) and heavy metals as well (Pb(II), Cd(II) Co(II) Cr(III) and Ag(I) ….). They also contribute to the degradation of terrestrial and aquatic habitats. Sustainable and effective methods for removing MPs from wastewater and treating organic micropollutants in an environmentally friendly manner are being developed in order to address this problem. This work offers a thorough review of adsorption technology as a productive and environmentally friendly means of eliminating MPs from aqueous environments, with an emphasis on developments in the application of polymeric resin in MP removal. The review examines the adsorption process and the variables that affect adsorption efficiency, including the characteristics of the micropollutant, the resin, and the solution. To improve understanding, a number of adsorption mechanisms and models are explored. The study also addresses the difficulties and future possibilities of adsorption technology, emphasising the need to optimize resin characteristics, create sustainable and affordable regeneration techniques, and take into account the environmental effects of adsorbent materials.

Adsorption behavior of different cresols on bismuthene: a DFT study

Phenolic compounds present in wastewater were utilized for first-principle calculations based on DFT to observe adsorption effects. Results indicate that bismuthene exhibits different adsorption characteristics for different compounds. Following the adsorption process, the aromatic ring remains in the same plane, while CH3 and OH groups move upward, causing slight changes in the molecules' overall position. The calculated results show that bisphenol A has the least atomic distance (4.00 Å) from the bismuthene surface and the highest adsorption energy value (12.8509 eV), indicating the stability and smoothness of the adsorption process. The electronic properties results reveal that phenolic compounds exhibit overlapping peaks at a distance from the Fermi level, describing the stability of the adsorption system. Additionally, the charge transfer results mirror the adsorption energy calculation results, showing that the bisphenol A adsorption system accepts a greater amount of (-0.116e) charge from the bismuthene surface, demonstrating a strong adsorption effect.

A review on recent advancements in extraction, removal and recovery of phenols from phenolic wastewater: Challenges and future outlook

Water pollution is the major problem seen in today's scenario and even pollutants at low concentration harms our environment. In industrial sector usage of phenol is seen even at low concentrations. The interaction of phenol in the environment provides adverse effects to living beings. This review focuses on the toxicity of phenol and its impact towards environment and human health. The treatment techniques such as distillation, extraction, wet air oxidation, membrane process, electrochemical oxidation, biological treatment and finally adsorption techniques were discussed. Among many treatment techniques so far utilized in the treatment of phenol, adsorption was considered as one of the best technique due to its advantages such as reusability, ease in operation, large availability etc., This review also highlights the adsorption technique for the cleaner removal of phenol from aqueous solution with novel as well as low-cost adsorbents in the removal of phenolic compounds. This review also discusses about the drawbacks and issues related with adsorption of phenolic compounds.

In Situ Redox Synthesis of Highly Stable Au/Electroactive Polyimide Composite and Its Application on 4-Nitrophenol Reduction

In this study, we developed a series of Au/electroactive polyimide (Au/EPI-5) composite for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) using NaBH₄ as a reducing agent at room temperature. The electroactive polyimide (EPI-5) synthesis was performed by chemical imidization of its 4,4'-(4.4'-isopropylidene-diphenoxy) bis (phthalic anhydride) (BSAA) and amino-capped aniline pentamer (ACAP). In addition, prepare different concentrations of Au ions through the in-situ redox reaction of EPI-5 to obtain Au nanoparticles (AuNPs) and anchored on the surface of EPI-5 to form series of Au/EPI-5 composite. Using SEM and HR-TEM confirm the particle size (23-113 nm) of the reduced AuNPs increases with the increase of the concentration. Based on CV studies, the redox capability of as-prepared electroactive materials was found to show an increase trend: 1Au/EPI-5 < 3Au/EPI-5 < 5Au/EPI-5. The series of Au/EPI-5 composites showed good stability and catalytic activity for the reaction of 4-NP to 4-AP. Especially, the 5Au/EPI-5 composite shows the highest catalytic activity when applied for the reduction of 4-NP to 4-AP within 17 min. The rate constant and kinetic activity energy were calculated to be 1.1 × 10^-3 s^-1 and 38.9 kJ/mol, respectively. Following a reusability test repeated 10 times, the 5Au/EPI-5 composite maintained a conversion rate higher than 95%. Finally, this study elaborates the mechanism of the catalytic reduction of 4-NP to 4-AP.

PdCu alloy prepared by ultrasonic method catalyzes the degradation of p-nitrophenol

PdCu alloy nanocatalysts supported on NiFe layered double hydroxide (PdCu-LDHs) were prepared by a green ultrasound-assisted reduction method. The cavitation effect of ultrasound made part of CO₃^2- decompose to CO₂, and NO₃^- and Cl^- replace intercalation, which anchor the PdCu between layers. The action of ultrasound dissociated hydroxyl groups (-OH) on surface of LDHs to H· to reduce Cu²⁺ and Pd²⁺ to Cu⁰ and Pd⁰ and Cu promote the synergy between Pd alloy and LDHs. The electronic effects between Cu and Pd improved the catalytic performance for the reduction reaction of 4-NP and the stability of PdCu-LDHs. The PdCu-LDHs prepared at 400 W, 25 kHz, 1 h, can completely degrade p-nitrophenol (4-NP) within 5 min with n(4-NP)/n(Pd) = 50 and n(4-NP)/n(NaBH₄) = 0.15. The TOF value is 988.20 h^-1, which is 27.7 times that of Pd/C catalyst (commercial).

Effective adsorption and catalytic reduction of nitrophenols by amino-rich Cu(I)-I coordination polymer

Nitrophenols are identified as the priority organic pollutants due to the chemical stability, water solubility, persistence, and toxicity to human health and the environment. Hence, removal of nitrophenols from waste water is vitally essential. In this study, amino-rich coordination polymer Cu₂I₂(MA)₂ (MA = melamine) has been applied for efficient adsorption and catalytic reduction of nitrophenols, like 4-nitrophenol (4-NP), 2, 4-dinitrophenol (DNP) and 2, 4, 6-trinitrophenol (TNP). The effect of various parameters like contact time, initial concentrations, pH, and temperature on adsorption were investigated. The adsorption of nitrophenols fitted the pseudo-second-order kinetic model and Langmuir isotherms model well. The maximum adsorption capacities were 285.71, 232.02, and 131.57 mg g^-1 for 4-NP, DNP, and TNP when initial concentrations were 50 mg L^-1 at 293.15 K, respectively. The adsorption of nitrophenols is a spontaneous, endothermic, and entropy-driven process. The reduction reaction followed the pseudo-first-order kinetics, and the kinetic rate constants were 0.4413, 0.3167, and 0.17538 min^-1 for 4-NP, DNP, and TNP, respectively. The effect of initial nitrophenols concentration, anions, and temperature on reduction process was investigated. The mechanism of adsorption and catalytic reduction of Cu₂I₂(MA)₂ was studied. The results demonstrated that Cu₂I₂(MA)₂ exhibits excellent adsorption and catalytic activity to remove nitrophenols.

Ionic liquid decorated MXene/Poly (N-isopropylacrylamide) composite hydrogel with high strength, chemical stability and strong adsorption

Organic phenolic pollutants in industrial wastewater cause severe environmental pollution and physiological damage. Poly (N-isopropylacrylamide) (PNIPAM) hydrogels generally have poor mechanical strength and are also intrinsically frangible, limiting their widespread applications in wastewater treatment. Combining them with 2-dimensional materials can also only improve the mechanical properties of hydrogels. Here, we report a high-strength, chemical stability and strong adsorption MXene/poly (N-isopropylacrylamide) (PNIPAM) thermosensitive composite hydrogel for efficient removal of phenolic pollutants from industrial wastewater. Ionic liquids (ILs) were grafted onto the surface of MXenes and introduced into NIPAM monomer solution to obtain composite hydrogels by in-situ polymerization for improved mechanical strength and adsorption capacity of the composite hydrogel. Compared with the MXene/PNIPAM composite hydrogel, the introduction of ILs simultaneously improves the mechanical and adsorption properties of the composite hydrogel. The ILs bind to the surface of MXene flakes through electrostatic interactions, which improved the thermal stability and oxidation resistance of MXenes while maintaining its good dispersion. Using 1-Ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) modified MXene (MXene-EMIMBF4) did not change significantly were observed after aging for 45 days. As-prepared composite hydrogels demonstrated excellent mechanical properties, reusability, and high adsorption capacity for p-Nitrophenol (4-NP). The MXene-EMIMBF4/PNIPAM hydrogel could recover after ten 95% strain compression cycles under the synergistic effect of chemical bonding and electrostatic attraction. Its maximum adsorption capacity for 4-NP was 200.29 mg g^-1 at room temperature, and the adsorption capacity maintained at ∼90% of its initial value after five adsorption cycles, which was related to the introduction of EMIMBF4 to form a denser network structure. The adsorption data followed the pseudo-second-order kinetics and Freundlich models.

Ultrasonic assisted preparation of ultrafine Pd supported on NiFe-layered double hydroxides for p-nitrophenol degradation

NiFe-layered double hydroxide (NiFe-LDH)-loaded ultrafine Pd nanocatalysts (Pd/NiFe-LDHs) were prepared by a facile ultrasonic-assisted in situ reduction technology without any stabilizing agents or reducing agents. Pd/NiFe-LDHs were characterized by FT-IR, XRD, XPS, and TEM. PdNPs are uniformly dispersed on NiFe-LDHs with a particle size distribution of 0.77-2.06 nm and an average particle size of 1.43 nm. Hydroxyl groups in Fe-OH and Ni-OH were dissociated into hydrogen radicals (·H) excited by ultrasound, and ·H reduced Pd²⁺ to ultrafine PdNPs. Then, Pd was coordinated with O in Ni-O and Fe-O, which improved the stability of the catalysts. Pd/NiFe-LDHs completely degraded 4-NP in 5 min, and the TOF value was 597.66 h^-1, which was 16.7 times that of commercial Pd/C. The 4-NP conversion rate remained at 98.75% over Pd/NiFe-LDHs after 10 consecutive catalytic cycles. In addition, the catalyst also has high catalytic activity for the reduction of Congo red, methylene blue, and methyl orange by NaBH₄.

Removing Calcium Ions from Remelt Syrup with Rosin-Based Macroporous Cationic Resin

Mineral ions (mainly calcium ions) from sugarcane juice can be trapped inside the heating tubes of evaporators and vacuum boiling pans, and calcium ions are precipitated. Consequently, sugar productivity and yield are negatively affected. Calcium ions can be removed from sugarcane juice using adsorption. This paper described the experimental condition for the batch adsorption performance of rosin-based macroporous cationic resins (RMCRs) for calcium ions. The kinetics of adsorption was defined by the pseudo-first-order model, and the isotherms of calcium ions followed the Freundlich isotherm model. The maximal monolayer adsorption capacity of calcium ions was 37.05 mg·g^-1 at a resin dosage of 4 g·L^-1, pH of 7.0, temperature of 75 °C, and contact time of 10 h. It appeared that the adsorption was spontaneous and endothermic based on the thermodynamic parameters. The removal rate of calcium ions in remelt syrup by RMCRs was 90.71%. Calcium ions were effectively removed from loaded RMCRs by 0.1 mol·L^-1 of HCl, and the RMCRs could be recycled. The dynamic saturated adsorption capacity of RMCRs for calcium ions in remelt syrup was 37.90 mg·g^-1. These results suggest that RMCRs are inexpensive and efficient adsorbents and have potential applications for removing calcium ions in remelt syrup.

Amine-amide functionalized graphene oxide sheets as bifunctional adsorbent for the removal of polar organic pollutants

Effective mitigation of polar organic impurities from industrial effluents is a global environmental challenge. Here, we describe the solvothermal synthesis of ammonia-functionalized graphene oxide (NH₃GO) sheets for adsorptive removal of diverse organic pollutants, such as cationic dye basic blue 41 (BB41), anionic dye methyl orange (MO), and ionic 4-nitrophenol (4-NP), in aqueous media. Structural analysis of NH₃GO suggest a potent role of surface acidic and basic binding sites in adsorption of targets through an interplay of dynamic experimental variables, e.g., contact time, pH, initial adsorbate concentration, adsorbent mass, and temperature. At an initial pollutant concentration of 20 mg/L, equilibrium adsorption capacities for BB41, MO, and 4-NP were estimated at 199.5, 64.0, and 54.1 mg/g, respectively, with corresponding partition coefficients of 4156, 79.4, and 14.3 L/g, respectively. Experimental data of all three organic pollutants are best fitted by the pseudo-second-order kinetic model. The adsorption isotherm of BB41 follows a multilayer adsorption pattern, while those of MO and 4-NP fit into a monolayer adsorption pattern. The endothermic and spontaneous nature of the adsorption processes has also been explored for the three targets on NH₃GO based on thermodynamic analysis. The prepared NH₃GO sheets appear to be a promising adsorbent for the removal of polar organic dyes and aromatics in the solution phase.

A facile modification of cation exchange resin by nano-sized goethite for enhanced Cr(VI) removal from water

A novel macroporous strong acidic cation exchange resin (D001) modified by nano-sized goethite (nFeOOH@D001) was fabricated by using a facile ethanol dispersion and impregnation method, and its efficiency for Cr(VI) removal was tested thereafter. Due to the dispersing effect of ethanol, FeOOH particles of 20-150 nm were coated on the D001 surfaces. The nFeOOH@D001 obtained a Cr(VI) removal efficiency and capacity of 80.2% and 7.4 mg/g respectively, 5 times and 8 times higher than that of the pristine D001. The Cr(VI) removal by nFeOOH@D001 followed the pseudo second-order kinetics and the Langmuir adsorption model. Column experiments also demonstrated that the nFeOOH@D001 exhibited a much better ability to remove Cr(VI) as compared to the D001. Additionally, the nFeOOH@D001 showed a potential for reusability and renewability. The adsorbed nFeOOH@D001 could be easily desorbed by 0.1 M acetic acid and a reuse efficiency of 92.7% could be maintained after 4 desorption-adsorption cycles. The used nFeOOH@D001 could be eluted by 0.1 M HCl to remove nFeOOH, and the renewed D001 could be recoated by nFeOOH and achieved a regeneration rate of 97.8% for Cr(VI) removal. The above results indicated that nano-sized goethite modification is a promising method to endow D001 with the ability to remove Cr(VI) from water.

Ionic Liquid Agar-Alginate Beads as a Sustainable Phenol Adsorbent

Cleaning wastewater containing low concentrations of phenolic compounds is a challenging task. In this work, agar–alginate beads impregnated with trihexyltetradecylphosphonium bromide ([P₆₆₆₁₄][Br]) ionic liquid adsorbent were synthesized as a potential adsorbent for such applications. FTIR, TGA, SEM, EDX and PZC studies were performed to characterize and understand the physicochemical properties of the adsorbent. The Fourier transformation infrared spectroscopy (FTIR) study showed that [P₆₆₆₁₄][Br] ionic liquid was effectively incorporated into the agar–alginate structure. TGA and SEM confirmed comparative enhanced thermal stability and porous surface, respectively. Chemical reaction rate-altering parameters, i.e., pH, contact time, initial phenol concentration and temperature, are optimized at highest phenol removal. It was found that the maximum phenol adsorption capacity and highest removal efficiency by the adsorbent occurred at pH 2, initial phenol concentration of 150 mg/L, beads dosage of 6 mg/mL and contact time of 2 h with values of 16.28 mg/g and 65.12%, respectively. The pseudo-second order model fitted the adsorption kinetics well, and the Freundlich isotherm model gave the experimental data the best fit. Analysis of thermodynamic data demonstrated that the adsorption process is fundamentally exothermic in nature, and low temperature favors spontaneity of the chemical reaction. Regeneration studies indicated that the adsorbent can at least be used for four cycles in such applications without any considerable loss in adsorption efficiency.

Studies of a bola-type bis(dithiafulvene) molecular system: synthesis, crystal structure, and electrochemical properties

A bis(dithiafulvene) compound that contains a 1,3-diphenoxypropane central unit was designed and investigated in this work.

Electronic properties and reactivity of oxidized graphene nanoribbons and their interaction with phenol

The effect of the oxidized functional groups on the structural, electronic, and reactivity properties of armchair graphene nanoribbons has been investigated in the framework of the density functional theory. The presence of functional groups near the edges stabilizes the oxidized graphene nanoribbons (OGNRs) more than substituting near the center. Overall, we found slight differences in the electronic properties of OGNRs concerning the pristine ones. The oxygen contribution of functional groups to the DOS is found in the conducting energy bands far from the Fermi level. Consequently, the semiconducting behavior is maintained after doping. Based on the reactivity of OGNRs, the most promising nanostructures were proposed as adsorbents studying the interaction and complexation with phenol, a critical pollutant removed mainly by hydrotreating processes (HDO) to produce bio-oil. Parallel and perpendicular phenol conformations were found towards the OGNRs in the optimized complexes driven by a physisorption process. These results provide significant insights for catalytic processes that use biomass derivatives containing phenolic compounds. The physisorption of streams containing pollutants on OGNRs could be adapted to new technological applications for the remotion of aromatic compounds under environmentally friendly operational conditions.

Chiral Quaternary Ammoniums Derived from Dehydroabietylamine: Synthesis and Application to Alkynylation of Isatin Derivatives Catalyzed by Silver

Abietic acid and its derivatives have broadly been used in fine chemicals and are renewable resources. Its inherent chiral rigid tricyclic phenanthrene skeleton is unique. Its utilities in asymmetric catalysis remain to be explored. A series new amide-type chiral quaternary ammoniums bearing dehydroabietylamine were designed, and prepared by two convenient steps. Acylation of dehydroabietylamine with bromoacetyl chloride afforded amide holding bromoacetyl group in higher yields using triethyl amine as base. Subsequent quaternization reaction gave the desired amide-type chiral quaternary ammoniums. The new chiral quaternary ammoniums can be used as phase-transfer catalyst (PTC) for the transition metal-catalysed alkynylation of isatin derivatives.

A Review on Ion-Exchange Membrane Fouling during the Electrodialysis Process in the Food Industry, Part 1: Types, Effects, Characterization Methods, Fouling Mechanisms and Interactions

Electrodialysis (ED) was first established for water desalination and is still highly recommended in this field for its high water recovery, long lifetime and acceptable electricity consumption. Today, thanks to technological progress in ED processes and the emergence of new ion-exchange membranes (IEMs), ED has been extended to many other applications in the food industry. This expansion of uses has also generated several problems such as IEMs' lifetime limitation due to different ageing phenomena (because of organic and/or mineral compounds). The current commercial IEMs show excellent performance in ED processes; however, organic foulants such as proteins, surfactants, polyphenols or other natural organic matters can adhere on their surface (especially when using anion-exchange membranes: AEMs) forming a colloid layer or can infiltrate the membrane matrix, which leads to the increase in electrical resistance, resulting in higher energy consumption, lower water recovery, loss of membrane permselectivity and current efficiency as well as lifetime limitation. If these aspects are not sufficiently controlled and mastered, the use and the efficiency of ED processes will be limited since, it will no longer be competitive or profitable compared to other separation methods. In this work we reviewed a significant amount of recent scientific publications, research and reviews studying the phenomena of IEM fouling during the ED process in food industry with a special focus on the last decade. We first classified the different types of fouling according to the most commonly used classifications. Then, the fouling effects, the characterization methods and techniques as well as the different fouling mechanisms and interactions as well as their influence on IEM matrix and fixed groups were presented, analyzed, discussed and illustrated.

Renewable and robust biomass waste-derived Co-doped carbon aerogels for PMS activation: Catalytic mechanisms and phytotoxicity assessment

Developing monolithic carbon-based catalyst with low cost, easy separation and high performance to degrade pollutants via PMS activation is crucial. In this work, a series of novel monolithic Me-CA catalysts based on biomass derived carbon aerogel were prepared by hydrothermal method using waste watermelon peel as raw material. Co-CA catalyst showed excellent performance to activate PMS for 2, 4-DCP degradation in different temperature and different water matrices. Different pollutants, such as ciprofloxacin (CIP), bisphenol A (BPA), and 2, 4-dichlorophenoxyacetic acid (2, 4-D) could also be removed in the Co-CA/PMS system. As expected, Co-CA could be easily separated from degraded solution, and show high stability and reusability for PMS activation with a lower cobalt leaching. Based on the results of the quenching tests, electron paramagnetic resonance (EPR) spectra, Chronoamperometric test (i-t curves) and electro-chemical impedance spectroscopy (EIS), the PMS activation mechanism was proposed. The phytotoxicity assessment determined by germination situation of mung bean indicated that PMS activation could eliminate the hazards of 2, 4-D. Therefore, this study provides a low cost, efficient and environmental-friendly monolithic biomass carbon aerogel catalyst for different pollutants degradation, which further advances monolithic catalyst for practical wastewater treatment.

Adsorption of 4-Nitrophenol on calcium alginate-multiwall carbon nanotube beads: Modeling, kinetics, equilibriums and reusability studies

In this study calcium alginate-multiwall carbon nanotube (CA/MWCNTs) was synthesized using (CA) calcium alginate and multiwall carbon nanotube (MWCNTs), and its efficiency in adsorption of 4-Nitrophenol (4-NP) in aqueous solution was studied. The structure and properties of the synthesized adsorbent were investigated using scanning electron microscope (SEM), thermal gravimetric analysis (TGA), Fourier transform infrared (FTIR), and X-ray diffraction (XRD). The experimental design was performed using Box-Behnken design (BBD) in which variables pH, CA/MWCNTs, and temperature were examined. The results of the effect of temperature on the removal efficiency of 4-NP showed that the adsorption efficiency decreases with increasing temperature. The results of nonlinear isotherm and kinetics models showed that Langmuir and pseudo-second-order models were more consistent than other models. The maximum adsorption capacity of 4-NP in this study by CA, MWCNTs, and CA/MWCNTs was 136, 168.4, and 58.8 mg/g, respectively, which indicates that the use of MWCNTs on CA could increase the adsorption capacity. The results of reuse of the synthesized adsorbent at 4-NP removal also showed that after 5 reuse of the adsorbent, the removal of 4-NP using CA/MWCNTs is reduced by about 10%, which shows that the synthesized adsorbent can be used several times to adsorb contaminants without significant reduction in the efficiency.

Insights into the p-nitrophenol adsorption by amidoxime-modified poly(acrylonitrile-co-acrylic acid): characterization, kinetics, isotherm, thermodynamic, regeneration and mechanism study

This study performs an appraisal of the adsorptive capacity of amidoxime-modified poly(acrylonitrile-co-acrylic acid) or abbreviated as (AO-modified poly(AN-co-AA)) for the p-nitrophenol (PNP) adsorption, from aquatic environments via batch system. The AO-modified poly(AN-co-AA) polymer was developed with redox polymerization, and then altered by using hydroxylamine hydrochloride (HH). Tools used to describe the physicochemical and morphological characteristics of the AO-modified poly(AN-co-AA) were Fourier transform infrared (FTIR) spectroscopy, CHN elemental analysis, X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The adsorption kinetics were examined by pseudo-first order, pseudo-second order, Elovich and intraparticle diffusion kinetic models. Meanwhile, the isotherms were investigated by Langmuir, Freundlich, Temkin and Redlich-Peterson models. It was found that the adsorption was best fitted with pseudo-second order, and agreed with both Langmuir and Freundlich isotherm models. It was described best with the Freundlich isotherm due to highest R 2 (0.999). The maximum adsorption capacity was 143.06 mg g-1 at 298 K, and thermodynamic functions showed that the adsorption process was exothermic. Also, following five regeneration cycles, the adsorbent recorded 71.7% regeneration efficiency. The finding in this study indicates that the AO-modified poly(AN-co-AA) is an effective adsorbent to remove PNP from an aqueous solution.

Recyclable Magnetic Cu/CuFe2O4 Nanocomposites for the Rapid Degradation of 4-NP

Magnetic Cu/CuFe2O4 nanocomposites were prepared by the one-pot thermal decomposition of acetylacetone compounds. Adjusting the molar ratios of Fe to Cu was used to control the content of Cu in the synthetic process. XRD, TEM, XPS and UV-Vis were employed to reveal detailed structural and catalytic activities of Cu/CuFe2O4 nanocomposites. Magnetic measurements demonstrated that Cu/CuFe2O4 nanocomposites possessed a considerable magnetic saturation. Cu/CuFe2O4 nanocomposites showed superb efficiency in the degradation of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). 4-NP could be reduced by Cu/CuFe2O4 nanocomposites within 40 s in the attendance of NaBH4. Cu nanocrystals played an indispensable rose in the enhancement of catalytic performance. The synergistic effect of Cu and CuFe2O4 nanocrystals achieved the high-efficiency catalytic reduction for 4-NP. After six recycling experiments, the efficiency of Cu/CuFe2O4 nanocomposites was almost stable. Our work advances a straightforward strategy to synthesize efficient and recoverable Cu/CuFe2O4 nanocomposites, which has promising utilizations in the purifying of nitrophenolic contamination.

Adsorption of Anthocyanins by Cation and Anion Exchange Resins with Aromatic and Aliphatic Polymer Matrices

This study examines the mechanisms of adsorption of anthocyanins from model aqueous solutions at pH values of 3, 6, and 9 by ion-exchange resins making the main component of heterogeneous ion-exchange membranes. This is the first report demonstrating that the pH of the internal solution of a KU-2-8 aromatic cation-exchange resin is 2-3 units lower than the pH of the external bathing anthocyanin-containing solution, and the pH of the internal solution of some anion-exchange resins with an aromatic (AV-17-8, AV-17-2P) or aliphatic (EDE-10P) matrix is 2-4 units higher than the pH of the external solution. This pH shift is caused by the Donnan exclusion of hydroxyl ions (in the KU-2-8 resin) or protons (in the AV-17-8, AV-17-2P, and EDE-10P resins). The most significant pH shift is observed for the EDE-10P resin, which has the highest ion-exchange capacity causing the highest Donnan exclusion. Due to the pH shift, the electric charge of anthocyanin inside an ion-exchange resin differs from its charge in the external solution. At pH 6, the external solution contains uncharged anthocyanin molecules. However, in the AV-17-8 and AV-17-2P resins, the anthocyanins are present as singly charged anions, while in the EDE-10P resin, they are in the form of doubly charged anions. Due to the electrostatic interactions of these anions with the positively charged fixed groups of anion-exchange resins, the adsorption capacities of AV-17-8, AV-17-2P, and EDE-10P were higher than expected. It was established that the electrostatic interactions of anthocyanins with the charged fixed groups increase the adsorption capacity of the aromatic resin by a factor of 1.8-2.5 compared to the adsorption caused by the π-π (stacking) interactions. These results provide new insights into the fouling mechanism of ion-exchange materials by polyphenols; they can help develop strategies for membrane cleaning and for extracting anthocyanins from juices and wine using ion-exchange resins and membranes.

Mechanochemically Synthesised Coal-Based Magnetic Carbon Composites for Removing As(V) and Cd(II) from Aqueous Solutions

The continued decrease in water quality requires new advances in the treatment of wastewater, including the preparation of novel, effective, environmentally friendly, and affordable sorbents of toxic pollutants. We introduce a simple non-conventional mechanochemical synthesis of magnetically responsive materials. Magnetic lignite and magnetic char were prepared by high-energy ball co-milling from either raw Slovak lignite or coal-based char together with a ferrofluid. The products were characterised by X-ray diffraction, electron microscopy, ⁵⁷Fe Mössbauer spectroscopy, X-ray photoelectron spectroscopy (XPS), volumetric magnetic susceptibility, and low-temperature nitrogen adsorption, and both magnetic carbons were comparatively tested as potential sorbents of As(V) oxyanions and Cd(II) cations in aqueous solutions. The magnetic char was an excellent sorbent of As(V) oxyanions (Q_m = 19.9 mg/g at pH 3.9), whereas the magnetic lignite was less effective. The different sorption properties towards arsenic anions may have been due to different oxidation states of iron on the surfaces of the two magnetic composites (determined by XPS), although the overall state of iron monitored by Mössbauer spectroscopy was similar for both samples. Both magnetic composites were effective sorbents for removing Cd(II) cations (Q_m (magnetic lignite) = 70.4 mg/g at pH 6.5; Q_m (magnetic char) = 58.8 mg/g at pH 6.8).