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This study explored the fabrication of Polypyrrole (PPy) and Granular Activated Carbon (GAC) composites (PPy‐GAC) for effective removal of toxic hexavalent chromium (Cr(VI)) from aqueous solutions. Two synthesis methods are employed: (1) electrostatic deposition of PPy onto pre‐charged GAC paper and (2) in‐situ chemical polymerization of pyrrole monomer with GAC particles. Batch adsorption experiments investigated the impact of various operational parameters on Cr(VI) removal. Compared to pristine GAC (54.64 mg g−1), the PPy‐GAC composite exhibited a remarkable 3‐fold increase in equilibrium adsorption capacity, reaching 175.44 mg g−1. Pseudo‐second‐order kinetic model (R2 > 0.999) accurately described the adsorption kinetics, while the Langmuir isotherm model (R2 > 0.99) provided a good fit for the equilibrium data. Maximum adsorption capacity (qmax) increased with temperature, reaching 204.08, 243.90, and 270.27 mg g−1 at 298, 308, and 318 K, respectively. Furthermore, a fixed‐bed column experiment examined the composite's effectiveness in continuous Cr(VI) removal, demonstrating its suitability for practical applications. Notably, the PPy‐GAC composite successfully removed Cr(VI) from a real wastewater sample containing 68 µg L−1 Cr(VI) obtained from a ferrochrome industry, highlighting its potential for real‐world remediation. [ABSTRACT FROM AUTHOR]

This research focuses on valorising waste burnt tires (BTs) through a two-phase oxidation process, leading to the production of onion-like carbon-based nanostructures. The initial carbonization of BTs yielded activated carbon (AC), denoted as "BTSA", followed by further oxidation using the modified Hummer's method to produce onion-like carbon designated as "BTHM". Brunauer–Emmett–Teller (BET) surface area measurements showed 5.49 m2/g, 19.88 m2/g, and 71.08 m2/g for raw BT, BTSA, and BTHM, respectively. Additional surface functionalization oxidations were observed through Fourier-Transform Infrared (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM) analyses. Raman spectroscopy indicated an increased graphitic nature during each oxidation stage. BTHM was assessed in batch adsorption studies for cupric wastewater remediation, revealing a two-phase pseudo-first-order behaviour dominated by mass transfer to BTHM. The maximum adsorption capacity for Cu2+ on BTHM was determined as 136.1 mg/g at 25 °C. Langmuir adsorption isotherm best described BTHM at a solution pH of 6, while kinetics studies suggested pseudo-second-order kinetics. Furthermore, BTHM, laden with Cu2+, served as a catalyst in a model coupling reaction of para-idoanisole and phenol, successfully yielding the desired product. This study highlights the promising potential of BTHM for both environmental remediation and catalytic reuse applications to avoid the generation of secondary environmental waste by the spent adsorbent. [ABSTRACT FROM AUTHOR]

Tunability of key length scales including nanodimensionality, mean free path, localization length, and cyclotron radius gives opportunities to fabricate nanodevices with new functionalities. Herein, in order to tune localization length, composite nanorods (CNRs) of 2-naphthalene sulfonic acid doped polyaniline (PANI-NSA) and nickel ferrite nanoparticles (NiFe2O4 NPs) are synthesized via an in situ chemical polymerization method. The nanorods' structure and the incorporation of the NiFe2O4 NPs into the PANI-NSA matrix are envisaged by various characterization techniques. The presence of a hysteresis loop with minor coercivity and remanence suggests the ferrimagnetic property of PANI-NSA/NiFe2O4 CNRs at room temperature. Investigation of electrical resistivity as a function of temperature in the absence of an external magnetic field establishes quasi-one-dimensional variable range hopping conduction mechanism of the PANI-NSA/NiFe2O4 CNR samples. CNR samples with two different loadings of NiFe2O4 NPs demonstrate substantial amounts of magnetoresistance (MR) at all the temperatures (300–50 K) studied. Intriguingly, a transition from positive to negative MR is observed with an increase in temperature from 200 to 300 K for CNR samples with less amount of NiFe2O4 (CNRs 1), whereas MR is positive for CNRs with higher loading of NiFe2O4, throughout the studied temperatures. Positive and negative MR behaviors of the CNR samples are quantitatively elucidated in terms of wave function shrinkage and forward interference models. Deduced localization length from the forward interference regime for CNRs 1 is about one order of magnitude larger than that in the wave function shrinkage regime. Thus, tuning of localization length can be achieved qualitatively through appropriate loading of NiFe2O4 NPs. [ABSTRACT FROM AUTHOR]

This study focuses on a greener approach to synthesizing activated carbon by carbonizing Platamus occidentalis tree fibers (TFSA) with 98% H2SO4 at 100 °C. The resulted TFSA was employed as an effective adsorbent for copper ions in aqueous media, yielding copper decorated TFSA (Cu@TFSA). The successful adsorption of copper onto the TFSA was proven through extensive characterization techniques. Herein, the TEM and XPS showed that copper nanoparticles were formed in situ on the TFSA surface, without the use of additional reducing and stabilizing agents nor thermal treatment. The surface areas of TFSA and Cu@TFSA were 0.0150 m2/g and 0.3109 m2/g, respectively. Applying the Cu@TFSA as an antimicrobial agent against Escherica coli (E. coli) and Salmonella resulted in the potential mitigation of complex secondary pollutants from water and wastewater. The Cu@TFSA exhibited outstanding antimicrobial activity against E. coli and Salmonella in both synthetic and raw water samples. This demonstrated a complete growth inhibition observed within 120 min of exposure. The bacteria inactivation took place through the destruction of the bacteria cell wall and was confirmed by the AFM analysis technique. Cu@TFSA has the potential to be used in the water and wastewater treatment sector as antimicrobial agents. [ABSTRACT FROM AUTHOR]

A cationic adsorbent, namely polyamine/folic acid composite (PFC) was used to remove Cr(VI) from aqueous solutions. The optimum pH was 2.0, achieving Cr(VI) removal of 99.4% at an initial concentration 200 mg/L, PFC dosage 0.5 g/L and temperature 298 K within 90 min. Under the acidic condition, electrostatic attractions between anionic species of chromium (HCrO4-and Cr2O72-) and cations on PFC (NR4+ and H+) enhanced Cr(VI) uptake. Additional removal mechanisms including anion exchange with Cl− (because of the use of epichlorohydrin for PFC preparation), reduction of Cr(VI) to Cr(III) and physical interaction could be involved in the adsorption process. Artificial neural network containing a first layer with five inputs, a hidden layer with eight neurons and the last layer with one output was able to predict the Cr(VI) removal efficiency (R2 = 0.919). The total cost of scaling up the adsorption system was $3.53 per m3 of wastewater containing 200 mg‐Cr(VI)/L. [ABSTRACT FROM AUTHOR]

In this paper, graphite‐like carbon nitride‐indium vanadate (g‐C3N4/InVO4) composites have been synthesized via a mixing‐calcination method. Physico‐chemical and photocatalytic experiments suggested that the optimized g‐C3N4/InVO4 composite demonstrates highest photo‐activity in degrading Rhodamine B and para‐nitrophenol as target pollutants. The electrochemical impedance spectroscopic (Mott‐Schottky) analysis confirms n‐type semiconductivity for these materials whereas the composite material exhibited highest 13 μA/cm2 photocurrent under periodic UV‐Visible irradiation for water oxidation. The relative band positions indicate inter‐band interactions between heterojunctions of g‐C3N4 and InVO4 facilitating the separation and migration of photogenerated electron‐hole pairs and a stable performance was reported. [ABSTRACT FROM AUTHOR]

Studies on magnetic field exposure of congo red contaminated water employing polypyrrole magnetic nanocomposite is reported. Alternating magnetic poles as a function of time has been used to move functionalized nanoparticles in congo red contaminated water. A maximum removal of 94% was observed for the adsorption of 100 mg/L of the adsorbate using 0.15 g of adsorbent at a magnetic field and exposure time of 18.99 mT and 120 min. Percentage of congo red dye removed increased with an increase in the magnetic exposure time of 10–120 min (79–94%). The magnetic force exerted on the magnetic nanoparticles leads to increased adsorption of congo red owing to increased velocity and reorientation of the charged particles. The Langmuir isotherm model had the highest correlation coefficient value and fitted well with the experimental data. The maximum adsorption capacity of 119.76 mg/g was observed using this isotherm model. [ABSTRACT FROM AUTHOR]

In the present study, a new composite adsorbent, chitosan/bentonite/manganese oxide (CBMnO) beads, cross-linked with tetraethyl-ortho-silicate (TEOS) was applied in a fixed-bed column for the removal of Mn (II) from water. The adsorbent was characterised by scanning electron microscopy (SEM), Fourier transform infra-red (FT-IR), N2 adsorption-desorption and X-ray photoelectron spectroscopy (XPS) techniques, and moreover the point of zero charge (pHpzc) was determined. The extend of Mn (II) breakthrough behaviour was investigated by varying bed mass, flow rate and influent concentration, and by using real environmental water samples. The dynamics of the column showed great dependency of breakthrough curves on the process conditions. The breakthrough time (tb), bed exhaustion time (ts), bed capacity (qe) and the overall bed efficiency (R%) increased with an increase in bed mass, but decreased with the increase in both influent flow rate and concentration. Non-linear regression suggested that the Thomas model effectively described the breakthrough curves while large-scale column performance could be estimated by the bed depth service time (BDST) model. Experiments with environmental water revealed that coexisting ions had little impact on Mn (II) removal, and it was possible to achieve 6.0 mg/g breakthrough capacity (qb), 4.0 L total treated water and 651 bed volumes processed with an initial concentration of 38.5 mg/L and 5.0 g bed mass. The exhausted bed could be regenerated with 0.001 M nitric acid solution within 1 h, and the sorbent could be reused twice without any significant loss of capacity. The findings advocate that CBMnO composite beads can provide an efficient scavenging pathway for Mn (II) in polluted water. [ABSTRACT FROM AUTHOR]

The present paper describes photocatalytically active In2O3 thin films developed using a direct drop-cast method on F-doped tin oxide (FTO) coated glass substrates using 10 mM In(NO3)3 dissolved in ethylene glycol containing 0–0.0125 M Triton-X 100 (TX-100) surfactant and annealed in air at 600 °C to obtain the desired metal oxide. The absorption spectrum measured the direct band gap of the surfactant modified In2O3 as 3.48 eV along with an indirect gap of 2.69 eV indicating near visible absorptivity of the materials, which was established through linear sweep voltammetry under periodic UV-Vis and visible irradiation for oxidation of water and a sacrificial reagent, SO32−. The electrochemical impedance spectroscopic (Mott–Schottky) analysis confirms n-type semiconductivity for these materials. Addition of an optimized level of 0.01 M TX-100 surfactant to the precursor solution improves the photoelectrochemical performance of the film to 2.3 fold. The electrochemical action spectra indicate a maximum value of the incident photon to current conversion efficiency (IPCE) for the 0.01 M surfactant modified In2O3 of 28% and the corresponding absorbed photon to current conversion efficiency (APCE) of 40%. Addition of surfactant to the In3+ precursor solution results in uniformly distributed particle growth on the surface with better crystallinity. [ABSTRACT FROM AUTHOR]

Polythiophene/graphene oxide (PTh/GO) nanocomposite (NC) was prepared through polymerisation of thiophene in the presence of GO and was used for mercury ions (Hg2+) adsorption in aqueous solutions. Equilibrium studies showed that mercury removal was strongly influenced by solution pH and GO composition in the NC. The equilibrium data were well described by both Langmuir and Freundlich isotherm models, with a Langmuir maximum adsorption capacity of 113.6 mg/g. Adsorption kinetics were rapid and correlated well with the pseudo-second-order model. The thermodynamic studies indicated that the adsorption was spontaneous and endothermic in nature, and occurred through a physicochemical mechanism. Desorption studies revealed that PTh/GO NC could be used repeatedly for three adsorption-desorption cycles without a significant loss in its capacity. Competing ions reduced mercury uptake although considerable values were still attained. The findings of this study suggest that PTh/GO NC is a potential adsorbent for Hg2+ removal from aqueous solutions. [ABSTRACT FROM AUTHOR]

Niobium carbide (NbC) nanoparticles embedded on the surface of carbon spheres (CS) were synthesized at 1350 °C by the carbothermal reduction of niobium oxide precursor in flowing argon (Nbc@CS). The morphology, crystal structure, and magnetic properties of the hybrid nanocomposite were investigated by means of electron microscopy, X-ray diffraction and a superconducting quantum interference device. It was found that the NbC@CS nanocomposites exhibit type-II superconductivity with a critical temperature (Tc) of 8–12 K, typical for stoichiometric NbC. The superconducting hysteresis loop reveals several interesting traits, including strong vortex pinning, the presence of asymmetry and a high penetration field. Moreover, the sample shows much improved irreversible (Hirr), lower (Hc1) and upper (Hc2) critical fields. The coherence length (ξ), penetration depth (λ), and Ginzburg–Landau (κ) parameters for the sample were estimated to be 9.78 nm, 33 nm and 3.39, respectively. [ABSTRACT FROM AUTHOR]

The decoration of carbon spheres (CS) by highly dispersed tantalum carbide nanoparticles (TaC NPs) was achieved, for the first time by a unique carbothermal reduction method at 1350 °C for 30 min under reduced oxygen partial pressure. TaC NPs decorated CS composites were then extensively characterized by powder X-ray diffraction and electron microscopy techniques. The composite spheres were approximately 0.8–1 μm in diameter with an average size of 41 nm for the TaC NPs located at the surface. Transmission electron microscopy and Raman analysis showed the formation of the graphene layer at the outer surface of the TaC NPs. An anomalous ferromagnetic response with a spin-glass like behavior has been observed at low temperature in the dc magnetization study with complete suppression of the superconducting response. For ease of synthesis and high reproducibility, this technique opens a new paradigm in the preparation of carbon sphere supported high melting metal carbide nanoparticles for various technological purposes. [ABSTRACT FROM AUTHOR]

Polypyrrole (PPy)–coated magnetite (Fe3O4) hybrid particles were synthesized under sonication. PPy was coated on the surface of Fe3O4 microspheres, whereas pyrrole monomers filled the interior of the Fe3O4 particles and were then polymerized. The structure of the Fe3O4–PPy microspheres was confirmed by transmission electron microscopy. The electric and magnetic properties were confirmed by optical microscopy and vibrating sample magnetometry, respectively. The suspension of the Fe3O4–PPy composite microspheres dispersed in silicone oil exhibited both electrorheological and magnetorheological properties when measured using a rotational rheometer under an applied electric and magnetic field, respectively. [ABSTRACT FROM AUTHOR]

Fe0 nanoparticle-supported polyaniline (PANI) composite nanofibers were prepared as an additive for carbonyl iron (CI)-based magnetorheological (MR) fluids to improve the MR properties and dispersion stability. A simple chemical strategy was adopted to synthesize the PANI/Fe0 composite nanofibers. The synthesis method was based on the initial fabrication of interconnected PANI nanofibers by a rapidly mixed polymerization process using ferric chloride (FeCl3) as the oxidant and the subsequent reductive support of Fe0 nanoparticles onto the PANI nanofiber matrix using the polymerization by-products as a metal precursor. X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy showed that the fabricated nanofibers were composed of PANI and Fe0. Scanning and transmission electron microscopy imaging confirmed that the PANI/Fe0 composite nanofibers were 80–150 nm in diameter with an interconnected matrix. The MR fluid with the PANI/Fe0 composite nanofibers dispersed in mineral oil under an external magnetic field showed enhanced MR properties compared to that without an additive. Turbiscan data also confirmed the improved sedimentation properties of the MR fluid with an additive. [ABSTRACT FROM AUTHOR]

Attapulgite (ATP), a fibrous nanoclay mineral, was adopted as an additive in this study to improve the sedimentation problem of soft magnetic carbonyl iron (CI)-based magnetorheological (MR) fluids caused by the density mismatch between the CI particles and medium oil. The MR characteristics of the two MR fluid systems with and without ATP were measured and compared using a rotational rheometer under different magnetic field strengths. Scanning electron microscopy indicated that ATP filled the interspaces among the CI particles, explaining the improved dispersion stability of the MR fluid based on the Turbiscan sedimentation measurements. Despite the slight decrease in MR characteristics, the MR fluid with the additive exhibited the typical MR performance of an increase in shear stress in an applied magnetic field. [ABSTRACT FROM AUTHOR]

Conducting composites of polymethylmethacrylate and acetylene black were prepared via potassium chromate–sodium arsenite initiated redox polymerization of methylmethacrylate in presence of a suspension of acetylene black in aqueous methanol medium at 60°C. Prolonged extraction of the composite by tetrahydrofuran failed to extract the polymethylmethacrylate completely from the acetylene black surface, as confirmed by Fourier Transform Infrared studies. Scanning electron microscopic analyses revealed the formation of agglomerates of particles of nonuniform sizes and shapes. Thermal stability of the composite was appreciably improved relative to that for the unmodified base polymer. In sharp contrast to the d.c. conductivity of polymethylmethacrylate homopolymer (10 -13 S/cm), the conductivity of the composites reached values between 10 -4 S/cm to 10 -2 S/cm corresponding to acetylene black loading of 7% to 25%. [ABSTRACT FROM AUTHOR]

Analytical limitations have constrained the determination of nanopollution character from real-world sources such as nano-enabled products (NEPs), thus hindering the development of environmental safety guidelines for engineered nanomaterials (ENMs). This study examined the properties of ENMs in 18 commercial products: sunscreens, personal care products, clothing, and paints—products exhibiting medium to a high potential for environmental nanopollution. It was found that 17 of the products contained ENMs; 9, 3, 3, and 2 were incorporated with nTiO2, nAg, binaries of nZnO + nTiO2, and nTiO2 + nAg, respectively. Commonly, the nTiO2 were elongated or angular, whereas nAg and nZnO were near-spherical and angular in morphology, respectively. The size ranges (width × length) were 7–48 × 14–200, 34–35 × 37–38, and 18–28 nm for nTiO2, nZnO, and nAg respectively. All ENMs were negatively charged. The total concentration of Ti, Zn, and Ag in the NEPs were 2.3 × 10−4–4.3%, 3.4–4.3%, and 1.0 × 10−4–11.3 × 10−3%, respectively. The study determined some key ENM characteristics required for environmental risk assessment; however, challenges persist regarding the accurate determination of the concentration in NEPs. Overall, the study confirmed NEPs as actual sources of nanopollution; hence, scenario-specific efforts are recommended to quantify their loads into water resources. [ABSTRACT FROM AUTHOR]

A novel, modified polypyrrole/m-phenylediamine (PPy–mPD) composite, decorated with magnetite (Fe3O4) nanoparticles, and prepared via an in-situ oxidative polymerisation, was investigated. The PPy–mPD/Fe3O4 nanocomposite was employed for the removal of highly toxic oxyanion hexavalent chromium Cr(VI) from an aqueous solution. The structure and successful formation of the PPy–mPD/Fe3O4 nanocomposite was confirmed and investigated using various techniques. The presence of Fe3O4 was confirmed by high resolution transmission electron microscopy, with an appearance of Fe lattice fringes. The estimation of the saturation magnetisation of the nanocomposite, using a vibrating sample magnetometer, was observed to be 6.6 emu/g. In batch adsorption experiments, PPy–mPD/Fe3O4 nanocomposite (25 mg) was able to remove 99.6% of 100 mg/L of Cr(VI) at pH 2 and 25 °C. Adsorption isotherms were investigated at different Cr(VI) concentration (100–600 mg/L) and temperature (15–45 °C). It was deduced that adsorption follows the Langmuir model, with a maximum adsorption capacity of 555.6 mg/g for Cr(VI) removal. Furthermore, isotherm data were used to calculate thermodynamic values for Gibbs free energy, enthalpy change and entropy change, which indicated that Cr(VI) adsorption was spontaneous and endothermic in nature. Adsorption–desorption experiments revealed that the nanocomposite was usable for two consecutive cycles with no significant loss of adsorption capacity. This research demonstrates the application potential for the fascinating properties of PPy–mPD/Fe3O4 nanocomposite as a highly efficient adsorbent for the removal of heavy metal ions from industrial wastewater. [ABSTRACT FROM AUTHOR]