Synthesis, characterization of Fe3O4@glycine doped polypyrrole magnetic nanocomposites and their potential performance to remove toxic Cr(VI)

Polypyrrole Coating via Lemieux-von Rudloff Oxidation on Magnetite Nanoparticles for Highly Efficient Removal of Chromium(VI) from Wastewater

An alternative way for the coating of polypyrrole (PPy) polymer on hydrophobic magnetite (Fe3O4) nanoparticles is reported here to capture toxic chromium ions, Cr (VI), present in water. Iron oxide magnetic nanoparticles (Fe3O4) were synthesized by the conventional coprecipitation technique using FeCl3·6H2O and FeSO4·7H2O iron precursors and subsequently modified with oleic acid (OA). Then OA-Fe3O4 hydrophobic nanoparticles were oxidized using the Lemieux-von Rudloff reaction to transfer OA into hydrophilic azelaic acid (AA) (HOOC(CH2)7COOH-modified magnetic nanoparticles (AA-Fe3O4). Finally, a PPy polymer coating was formed by a seeded polymerization of pyrrole, using AA-Fe3O4 as seeds. The average size of PPy/Fe3O4 nanocomposites is 12.33 nm and is almost spherical in shape. The surface composition is confirmed by FTIR and thermogravimetry analyses. An X-ray diffraction study confirmed the formation of highly crystalline Fe3O4 nanoparticles, and the crystallinity was retained after the surface modification. The adsorption study suggested that the Cr(VI) ion adsorption is highly pH-dependent and the maximum amount of adsorption is obtained at pH 2.0. The adsorption results revealed that the Langmuir model provided the best fit for the isotherm, with a maximum adsorption capacity reaching approximately 173.22 mg g-1 at 323 K. Spontaneous and endothermic adsorption processes were confirmed by evaluating the thermodynamic parameters obtained in this investigation. The kinetics study showed that the interaction between Cr(VI) ions and magnetic nanocomposites was directed by a pseudo-second-order rate process indicating chemisorption. The prepared PPy/Fe3O4 nanocomposites would be promising adsorbents to purify water by eliminating Cr(VI) metal ions from wastewater.

Facile and green synthesis of recyclable, environmentally friendly, chemically stable, and cost-effective magnetic nanohybrid adsorbent for tetracycline adsorption

Antibiotic contamination of water sources, particularly tetracycline (TC) contamination, has emerged as one of the global issues that needs action. In this research, ZnCoFe2O4@Chitosan (Ch) as a magnetic nanohybrid adsorbent was synthesized using the microwave-assisted co-precipitation method, and their efficiency for the TC adsorption process was investigated. FESEM (Field Emission Scanning Electron Microscope), EDX (Energy Dispersive X-ray), Mapping and line Scan, XRD (X-Ray Diffraction), FTIR (Fourier Transform Infrared Spectrometer), VSM (Vibrating Sample Magnetometer), Thermogravimetric analysis (TGA) and BET (Brunauer Emmett Teller) techniques were used to check and verify its physical and chemical properties. The removal of TC via the adsorption process from synthetic and real wastewater samples was investigated. The factors determining the TC adsorption process, comprising tetracycline concentration (5-30 mg/L), adsorbent dosage (0.7-2 g/L), contact time (2-45 min), and pH (3-11), were evaluated. The removal effectiveness for the synthetic sample and the real wastewater sample was 93 % and 80 %, respectively, under the ideal TC adsorption process parameters of pH 3, adsorbent dosage 1 g/L, TC initial concentration 5 mg/L, and contact time 30 min. According to kinetic and equilibrium studies, the adsorption of TC by ZnCoFe2O4@Ch follows pseudo-second-order kinetics and the Freundlich isotherm. Additionally, it was determined through the analysis of thermodynamic data that the process of exothermic adsorption is spontaneous and is followed by a decrease in disorder (ΔH = -15.16 kJ/mol, ΔS = -28.69 kJ/mol, and ΔG = -6.62 kJ/mol). After five cycles of recovery and regeneration, the ZnCoFe2O4@Ch magnetic nanocomposite was able to remove 65 % of the TC pollutant and had good chemical stability. The results showed that the magnetic nano-adsorbent ZnCoFe2O4@Ch is a novel magnetic nano-adsorbent with high adsorption capacity that can be utilized to eliminate pharmaceutical contaminants from aqueous solutions.

Synthesis of iron oxide nanoparticles mediated by Camellia sinensis var. Assamica for Cr(VI) adsorption and detoxification

Environment-benign synthesis of nanoparticles (NPs) are of great importance. Plant-based polyphenols (PPs) are electron donor analytes for the synthesis of metal and metal oxide NPs. This work produced and investigated iron oxide nanoparticles (IONPs) from PPs of tea leaves of Camellia sinensis var. assamica for Cr(VI) removal. The conditions for IONPs synthesis were using RSM CCD and found to be optimum at a time of 48 min, temperature of 26 °C, and iron precursors/leaves extract ratio (v/v) of 0.36. Further, these synthesized IONPs at a dosage of 0.75 g/L, temperature of 25 °C, and pH 2 achieved a maximum of 96% Cr(VI) removal from 40 mg/L of Cr(VI) concentration. The exothermic adsorption process followed the pseudo-second-order model, and Langmuir isotherm estimated a remarkable maximum adsorption capacity (Q_m) of 1272 mg g^-1 of IONPs. The proposed mechanistic for Cr(VI) removal and detoxification involved adsorption and its reduction to Cr(III), followed by Cr(III)/Fe(III) co-precipitation.

Adsorption and reduction from modified polypyrrole enhance electrokinetic remediation of hexavalent chromium-contaminated soil

Toxic metal pollutant Cr(VI) in the environment will pose a severe threat to animal and human health. In this work, Fe₃O₄@PPy, Arg@PPy, and Arg/Fe₃O₄@PPy were prepared to enhance adsorption of Cr(VI) by doping Fe₃O₄ nanoparticles and amino radicals into the original PPy structure. Their characteristics were investigated by FTIR, SEM, EDS, BET analysis, and batch adsorption experiments. And they were used as permeable reaction barriers (PRB) to combine with electrokinetic remediation (EKR) to remediate Cr-contaminated soil. Adsorption experiment results showed that the maximum adsorption capacities of PPy, Fe₃O₄@PPy, Arg@PPy, and Arg/Fe₃O₄@PPy for Cr(VI) were 60.43 mg/g, 67.12 mg/g, 159.86 mg/g, and 141.50 mg/g, respectively. They all followed the kinetic pseudo-second-order model and the Langmuir isothermal model with a monolayer adsorption behavior. In the EKR/PRB system, the presence of Fe₃O₄@PPy, Arg@PPy, and Arg/Fe₃O₄@PPy obtained the higher Cr(VI) removal efficiency near the anode than that of the PPy, increasing by 74.60%, 26.04%, and 68.64%, respectively. A strong electrostatic attraction between anion contaminants and protonated modified PPy and a reduction from Cr(VI) to Cr(III) appeared in the EKR remediation process under acid conditions. This study opened up a prospect for applying modified PPy composites to treat toxic metal-contaminated soil.

Polypyrrole-based adsorbents for Cr(VI) ions remediation from aqueous solution: a review

Anthropogenic activities are principally responsible for the manifestation of toxic and carcinogenic hexavalent chromium (Cr(VI)) triggering water pollution that threatens the environment and human health. The World Health Organisation (WHO) restricts Cr(VI) ion concentration to 0.1 and 0.05 mg/L in inland surface water and drinking water, respectively. The available technologies for Cr(VI) ion removal from water were highlighted with an emphasis on the adsorption technology. Furthermore, the characteristics of several polypyrrole-based adsorbents were scrutinized including amino-containing compounds, biosorbents, graphene/graphene oxide, clay materials and many other additives with reported effective Cr(VI) ion uptake. This efficiency in Cr(VI) ions adsorption is attributed to enhanced redox properties, increased number of functional groups as well as the synergistic behaviour of the materials making up the composites. The Langmuir isotherm best described the adsorption processes with maximum adsorption capacities ranging from 3.40-961.50 mg/g. The regeneration of Cr(VI) ion-laden adsorbents was studied. Ion exchange, electrostatic attractions, complexation, chelation reactions with protonated sites and reduction were the mechanisms of adsorption. Nevertheless, there are limited details on comprehensive adsorbent regeneration studies to prolong robustness in adsorption-desorption cycles and utilization of the Cr(VI) ion-laden adsorbent in other areas of research to limit the threat of secondary pollution.

Synthesis of Polymer-Based Magnetic Nanocomposite for Multi-Pollutants Removal from Water

A magnetic polymer-based nanocomposite was fabricated by the modification of an Fe3O4/SiO2 magnetic composite with polypyrrole (PPy) via co-precipitation polymerization to form PPy/Fe3O4/SiO2 for the removal of Congo red dye (CR) and hexavalent chromium Cr(VI) ions from water. The nanocomposite was characterized using various techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), vibration sample magnetometer, and thermogravimetric analysis (TGA). The results confirm the successful fabrication of the nanocomposite in the size of nanometers. The effect of different conditions such as the contact time, adsorbent dosage, solution pH, and initial concentration on the adsorption process was investigated. The adsorption isotherm suggested monolayer adsorption of both contaminants over the PPy/Fe3O4/SiO2 nanocomposite following a Langmuir isotherm, with maximum adsorption of 361 and 298 mg.g-1 for CR dye and Cr(VI), respectively. Furthermore, the effect of water type on the adsorption process was examined, indicating the applicability of the PPy/Fe3O4/SiO2 nanocomposite for real sample treatment. Interestingly, the reusability of the nanocomposite for the removal of the studied contaminants was investigated with good results even after six successive cycles. All results make this nanocomposite a promising material for water treatment.

Facile synthesis and characterization of a novel 1,2,4,5-benzene tetracarboxylic acid doped polyaniline@zinc phosphate nanocomposite for highly efficient removal of hazardous hexavalent chromium ions from water

The present study describes the preparation of a novel 1,2,4,5-benzene tetracarboxylic acid doped polyaniline@zinc phosphate (BTCA-PANI@ZnP) nanocomposite via a facile two-step procedure. Thereafter, the as-prepared composite material adsorption characteristics for Cr(VI) ions removal were evaluated under batch adsorption. Kinetic approach studies for Cr(VI) removal, clearly demonstrated that the results of the adsorption process followed the pseudo second order and Langmuir models. The thermodynamic study indicated a spontaneous and endothermic process. Furthermore, higher monolayer adsorption was determined to be 933.88 mg g^-1. In addition, the capability study regarding Cr(VI) ions adsorption over BTCA-PANI@ZnP nanocomposite clearly revealed that our method is suitable for large scale application. X-ray photoelectron spectroscopy (XPS) analysis confirmed Cr(VI) adsorption on the BTCA-PANI@ZnP surface, followed by its subsequent reduction to Cr(III). Thus, the occurrence of external mass transfer, electrostatic attraction and reduction phenomenon were considered as main mechanistic pathways of Cr(VI) ions removal. The superior adsorption performance of the material, the multi-dimensional characteristics of the surface and the involvement of multiple removal mechanisms clearly demonstrated the potential applicability of the BTCA-PANI@ZnP material as an effective alternative for the removal of Cr(VI) ions from wastewater.

Removal of Cr(VI) from Aqueous Solution by Polypyrrole/Hollow Mesoporous Silica Particles

The removal of Cr(VI) in wastewater plays an important role in human health and environment. In this work, polypyrrole/hollow mesoporous silica particle (PPy/HMSNs) adsorbents have been newly synthesized by in-situ polymerization, which prevent the aggregation of pyrrole in the process of polymerization and exhibit highly selective and powerful adsorption ability for Cr(VI). The adsorption process was in good agreement with the quasi-second-order kinetic model and the Langmuir isotherm model. And the maximum adsorption capacity of Cr(VI) was 322 mg/g at 25 °C. Moreover, the removal rate of Cr(VI) by PPy/HMSNs was ~100% in a number of binary systems, such as Cl⁻/Cr(VI), NO₃⁻/Cr(VI), SO₄²⁻/Cr(VI), Zn²⁺/Cr(VI), Fe³⁺/Cr(VI), Sn⁴⁺/Cr(VI), and Cu²⁺/Cr(VI). Thus, the PPy/HMSNs adsorbents have great potential for the removal of Cr(VI) in wastewater.

Highly Efficient Removal of Cr(VI) from Aqueous Solutions by Polypyrrole/Monodisperse Latex Spheres

Pyrrole (Py) is easily agglomerated during the polymerization process, affecting its performance. In this paper, polypyrrole/monodispersed latex sphere (PPy/MLS) composites were prepared using in-situ polymerization for the adsorption of hexavalent chromium (Cr(VI)). The specific surface area of PPy/MLS (39.30 m²/g) was increased relative to that of PPy (24.82 m²/g), thus providing more effective adsorption sites. In addition, the adsorption properties of Cr(VI) under different conditions, including Py content, pH of the aqueous solution, and PPy/MLS dosage, were investigated to reveal the adsorption mechanism. The results showed that PPy/MLS possessed high Cr(VI) adsorption capacities when the Py content was 50 wt %. The maximum adsorption capacity was 343.64 mg/g at pH 2.0 and 25 °C. Remarkably, the adsorbents exhibited an excellent removal rate of Cr(VI) after three cycles of adsorption-desorption (over 99%), suggesting that the adsorbents had exceptional recyclability. Furthermore, the adsorption process followed quasi-second-order kinetics and Langmuir isothermal adsorption model. The high adsorption performance, sustainability, and cost-efficiency make this adsorbent a promising candidate for large-scale Cr(VI) contaminant removal.

Influence of Magnetic Nanoparticles on Modified Polypyrrole/m-Phenylediamine for Adsorption of Cr(VI) from Aqueous Solution

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.

Nanotechnology-based sorption and membrane technologies for the treatment of petroleum-based pollutants in natural ecosystems and wastewater streams

Petroleum processing wastewater (PPW) is a complex mixture of free, soluble, and emulsive hydrocarbons that often contain heavy metals and/or solid particles. As these hazardous constituents can accumulate in human beings and the environment, exposure to the PPW can have harmful effects in various respects. The use of environmental nanotechnologies (E-Nano) is considered an attractive option to resolve the problems associated with PPW. Among different treatment technologies, E-Nano-based sorption (adsorption/absorption) and membrane filtration approaches have been proven to have outstanding efficacy in remediation of PPW pollutants. It is, however, crucial to determine the appropriate technological option (e.g., low-cost operational conditions) for the practical application of such technologies. In this review, the potential of E-Nano-based sorption and membrane technologies in the treatment of various PPW pollutants is discussed based on their performances in comparison to traditional technologies. Their suitability is evaluated further in relation to their merits/disadvantages and economic feasibility with the goal of constructing a perspective map to efficiently implement the E-Nano technologies.

Fabrication of zwitterionic histidine/layered double hydroxide hybrid nanosheets for highly efficient and fast removal of anionic dyes

In this work, the bio-nanohybrids of magnesium-aluminum layered double hydroxide intercalated with zwitterionic histidine (His-LDH) was synthesized. The crystal phase, morphology, and nanostructure of the as-prepared His-LDH were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and nitrogen adsorption-desorption methods. The His-LDHs were used to remove anionic dyes, including Congo red (CR), indigo carmine (IC) and sunset yellow FCF (SY) from aqueous solutions. The detailed investigation of the kinetics and the adsorption isotherms of CR, IC and SY from aqueous solutions showed that the dyes adsorb rapidly, in accordance with a pseudo-second-order kinetics and a Freundlich adsorption isotherm model. The remarkably high adsorption capacity of the dyes on the His-LDH (efficiency of CR removal, 99.98%; maximum specific removal q_max, 1112 mg g^-1; efficiency of IC removal, 98.98%; q_max, 625 mg g^-1; and efficiency of SY removal, 99.78%; q_max, 400 mg g^-1) is rationalized on the basis of electrostatic interactions as well as π-π and H-bonding interactions between the His-LDH adsorbent and the acidic dyes. Adsorption experiments indicate that the resulting His-LDH has great potential applications as an environmentally friendly material for the swift removal of acidic dyes from aqueous solutions.

Applications of magnetic hybrid adsorbent derived from waste biomass for the removal of metal ions and reduction of 4-nitrophenol

The use of industrial waste to synthesize materials of technological interest is a rational way to minimize or solve environmental pollution problems. This work investigates the adsorption of cadmium and lead ions by magnetic hybrid adsorbents synthesized using the in natura biomasses coconut mesocarp (CCFe), sawdust (SAFe), and termite nest (TEFe) for the organic phases and magnetic cobalt ferrite as the inorganic phase. The formation of a cobalt ferrite phase was confirmed by XRD. The use of XRD and FTIR analyses revealed the presence of organic matter in the structure of the material. Removal assays performed at different pH values (2.0-8.0) showed the effectiveness of the adsorbent for the removal of Pb²⁺ at pH 3.0 and Cd²⁺ at pH 4.0. The adsorption processes showed fast kinetics, with removal of 79-86% of Pb²⁺ and 49% of Cd²⁺ within only 5 min, and removal of 92-96% of the metal species at equilibrium. In the case of cadmium, the hybrid sorbents (CCFe, SAFe, and TEFe) showed high removal capacity after three reuse cycles, while the removal of lead decreased from 99% to 40%. The adsorbent matrices saturated with the recovered cadmium and lead ions showed excellent catalytic performance in the reduction of 4-nitrophenol, with 99.9% conversion within 43-56 s. The materials showed high capacities for reuse in three successive reduction cycles. The findings highlight the effectiveness of an industrial symbiosis approach to the development of new technologically important materials.

Yolk-structured multifunctional up-conversion nanoparticles for synergistic photodynamic-sonodynamic antibacterial resistance therapy

The worldwide increase in bacterial antibiotic resistance has led to a search for alternative antibacterial therapies. The present study reports the development of yolk-structured multifunctional up-conversion nanoparticles (UCNPs) that combine photodynamic and sonodynamic therapy for effective killing of antibiotic-resistant bacteria. The multifunctional nanoparticles (NPs) were achieved by enclosing hematoporphyrin monomethyl ether (HMME) into its yolk-structured up-conversion core and covalently linked rose bengal (RB) on its silica (SiO₂) shell. Excitation of UCNPs with near-infrared (NIR) light that has improved penetration depth for photodynamic therapy (PDT) enabled the activation of HMME and RB and thus the generation of singlet oxygen (¹O₂). The SiO₂ layer, which improved the biocompatibility of the UCNPs, surrounded the yolk structure, with a cavity space which had a high efficiency of loading photosensitizers. Synergistic PDT and sonodynamic therapy (SDT) improved the photosensitizer utilization rate. As a result, a greater inhibition rate was observed when antibiotic-resistant bacteria were treated with a combined therapy (100%) compared with either the PDT (74.2%) or SDT (70%) alone. Our data indicate that the multifunctional NPs developed in this study have the potential for use in the clinical synergistic PDT-SDT treatment of infectious diseases caused by antibiotic-resistant bacteria.

Highly selective and efficient removal of arsenic(V), chromium(VI) and selenium(VI) oxyanions by layered double hydroxide intercalated with zwitterionic glycine

In this study, a new strategy for highly selective and extremely efficient removal of toxic oxyanions (Cr(VI), Se(VI), and As(V)) from aqueous solutions using zwitterionic glycine intercalated layered double hydroxide (Gly-LDH) was reported. Hence, to investigate the effect of zwitterionic glycine on the adsorption capacity, selectivity factor and adsorption mechanism of LDHs, two NiAl LDHs intercalated with different inter-layer anions, including NO₃^- and glycine, were synthesized. The obtained results show that the adsorption capacity and selectivity factor of oxyanions through ion exchange mechanism in NO₃-LDH is lower than Gly-LDH. Gly-LDH displayed a selectivity order of Se(VI)<Cr(VI)<<<As(V) for the oxyanions. The enormous adsorption capacity of 731.6mgg^-1 for As(V) and very high distribution coefficients (K_d) of 5.98×10⁷mLg^-1, using a V/m ratio of 2000mLg^-1, were observed, which are among the highest values reported for As(V) adsorbents. The adsorption kinetic curves for As(V) fitted well with the pseudo-second order model, suggesting a chemical adsorption mechanism via As(V)NH₃⁺ bonding. For the As(V) (at 40mgL^-1 concentration), the adsorption is exceptionally rapid, showing a 93.5% removal within 30min, 98.0% removal within 40min, and ∼100% removal within 70min.

Green synthesis of a magnetic hybrid adsorbent (CoFe2O4/NOM): Removal of chromium from industrial effluent and evaluation of the catalytic potential of recovered chromium ions

This work describes the removal of chromium ions from industrial effluent using a hybrid magnetic adsorbent, CoFe₂O₄/NOM, synthesized using water rich in natural organic matter. The hybrid obtained at ambient temperature (HbAmb) was calcined at 200, 400, and 800°C for 2h, and formation of the cobalt ferrite phase was confirmed by XRD, which indicated the presence of NOM in the structure of the material. Removal tests showed that HbAmb provided efficient removal of chromium at the natural pH of the effluent, while the other materials were effective at pH 6. Evaluation of the kinetics showed excellent performance of the process, with 70-87% removal in 20min, which provided a high degree of flexibility. The hybrid showed high removal during five reuse cycles, ranging from 96% in the first cycle to 82% in the final. The matrices containing the saturated adsorbent (HbAmb_Sat) and recovered chromium ions (CrD) showed high performance in the catalytic reduction of 4-nitrophenol, with conversion rates of 99.9% in short periods of time, as well as excellent potential for reuse in three cycles. The results demonstrated that the production of a technological material and its use for remediation could be achieved in an ecologically sustainable manner.

Selective removal of toxic Cr(VI) from aqueous solution by adsorption combined with reduction at a magnetic nanocomposite surface

The adsorption of toxic hexavalent chromium (Cr(VI)) and its reduction to trivalent chromium (Cr(III)) are important processes for the treatment of industrial wastewater. Conducting polymers can adsorb and reduce Cr(VI) to less toxic Cr(III) but have low adsorption capacities due to agglomeration of particles and are difficult to separate from treated water. In this study, magnetic polypyrrole (PPy)-polyaniline (PANI)/iron oxide (Fe₃O₄) nanocomposite was synthesized for the selective removal of Cr(VI) in aqueous solution. PPy-PANI/Fe₃O₄ nanocomposite was characterized using various techniques including ATR-FTIR, FE-SEM, HR-TEM, EDX, TGA, XRD, VSM and XPS analyses. PPy-PANI/Fe₃O₄ nanocomposite (0.05g) removed 99% of Cr(VI) from aqueous solution (100mg/L, pH 2). Speciation studies confirmed Cr(VI) adsorption and reduction to Cr(III) by the PPy-PANI/Fe₃O₄ nanocomposite in solutions with initial pH of 2 and 3 and that no Cr(VI) reduction occurred at pH values of 4 and above. The Langmuir maximum adsorption capacity for Cr(VI) removal by PPy-PANI/Fe₃O₄ nanocomposite at pH 2 was 303mg/g at 25°C. PPy-PANI/Fe₃O₄ nanocomposite was highly selective for Cr(VI) removal and could be used for three consecutive treatment cycles without loss of adsorption capacity. Moreover, the magnetic nanocomposite could be separated from the reaction fluid using an external magnet. PPy-PANI/Fe₃O₄ nanocomposite is therefore a promising magnetic adsorbent for the treatment of industrial wastewater.

Rapid and efficient removal of fluoride ions from aqueous solution using a polypyrrole coated hydrous tin oxide nanocomposite

Polypyrrole/hydrous tin oxide nanocomposites (PPy/HSnO NC 1, 2, 3, 4 and 5) were synthesized through encapsulating HSnO by the PPy via an in situ polymerization for fluoride removal. The optimized adsorbent i.e. PPy/HSnO NC 3 was characterized using FE-SEM, HR-TEM, ATR-FTIR, XRD, BET, TGA and zeta sizer. Microscopic images revealed the encapsulation of HSnO by precipitating PPy during polymerization. The FTIR and XRD studies confirmed the presence of both constituents. The BET surface area and pHpzc of the adsorbent were estimated to be 65.758m(2)/g and 7.6, respectively. The fluoride adsorption followed pseudo-second-order model and was commendably rapid. The monolayer adsorption capacity was found to be 26.16-28.99mg/g at pH 6.5±0.1. The thermodynamic parameters indicated the sorption of F(-) was spontaneous, endothermic and that physisorption occurred. The calculated activation energy (Ea∼20.05kJ/mol) provided further evidence of a physisorption mechanism. Moreover, the adsorbent performed very well over a considerably wide pH range of 3.5-8.5 and in the presence of other co-existing ions. The regeneration of the F(-) laden PPy/HSnO NC 3 showed a high desorption efficiency of 95.81% up to 3 cycles. Ground water tested results also demonstrate the potential utility of the PPy/HSnO NC as an effective adsorbent.

Enhanced removal of Cr(VI) from aqueous solutions using polypyrrole wrapped oxidized MWCNTs nanocomposites adsorbent

Polypyrrole wrapped oxidized multiwalled carbon nanotubes nanocomposites (PPy/OMWCNTs NCs) were prepared via in situ chemical polymerization of pyrrole (Py) monomer in the presence of OMWCNTs using FeCl3 as oxidant for the effective removal of hexavalent chromium [Cr(VI)]. The as-prepared PPy/OMWCNTs NCs were characterized by FE-SEM, HR-TEM, ATR-FTIR, XRD, XPS and BET method. Characterization results suggested that PPy was uniformly covered on the OMWCNTs surface and resulted in enhanced specific surface area. Adsorption experiments were carried out in batch sorption mode to investigate the effect of pH, dose of adsorbent, contact time, concentration of Cr(VI) and temperature. The adsorption of Cr(VI) on the nanocomposite surface was highly pH dependent and the kinetics of the adsorption followed the pseudo-second-order model. The adsorption isotherm data were in good conformity with the Langmuir isothermal model. The maximum adsorption capacity of the PPy/OMWCNTs NCs for Cr(VI) was 294mg/g at 25°C. The calculated values of the thermodynamic parameters such as ΔG(0) (-0.237kJ/mol), ΔH(0) (13.237kJ/mol) and ΔS(0) (0.0452kJ/mol/K) revealed that the adsorption process is spontaneous, endothermic and marked with an increase in randomness at the solid-liquid interface. The presence of co-existing ions slightly affected the Cr(VI) removal efficiency of the PPy/OMWCNTs.

The removal of heavy metal ions from wastewater/aqueous solution using polypyrrole-based adsorbents: a review

Water pollution caused by heavy metal ions is becoming a serious threat to human and aquatic lives day by day.

Microstructured macroporous adsorbent composed of polypyrrole modified natural corncob-core sponge for Cr(vi) removal

A high-performance, cost-effective and spongy adsorbent is rationally designed for Cr(vi) removal based on polypyrrole modified corncob-core natural microsheets.

Iron Oxide@PEDOT-Based Recyclable Photothermal Nanoparticles with Poly(vinylpyrrolidone) Sulfobetaines for Rapid and Effective Antibacterial Activity

Growing microbial resistance that renders antibiotic treatment vulnerable has emerged, attracting a great deal of interest in the need to develop alternative antimicrobial treatments. To contribute to this effort, we report magnetic iron oxide (Fe3O4) nanoparticles (NPs) coated with catechol-conjugated poly(vinylpyrrolidone) sulfobetaines (C-PVPS). This negatively charged Fe3O4@C-PVPS is subsequently encapsulated by poly(3,4-ethylenedioxythiophene) (PEDOT) following a layer-by-layer (LBL) self-assembly method. The obtained Fe3O4@C-PVPS:PEDOT nanoparticles appear to be novel NIR-irradiated photothermal agents that can achieve effective bacterial killing and are reusable after isolation of the used particles using external magnetic fields. The recyclable Fe3O4@C-PVPS:PEDOT NPs exhibit a high efficiency in converting photothermal heat for rapid antibacterial effects against Staphylococcus aureus and Escherichia coli. In this study, antibacterial tests for repeated uses maintained almost 100% antibacterial efficiency during three cycles and provided rapid and effective killing of 99% Gram-positive and -negative bacteria within 5 min of near-infrared (NIR) light exposure. The core-shell nanoparticles (Fe3O4@C-PVPS:PEDOT) exhibit the required stability, and their paramagnetic nature means that they rapidly convert photothermal heat sufficient for use as NIR-irradiated antibacterial photothermal sterilizing agents.

Combination of cathodic reduction with adsorption for accelerated removal of Cr(VI) through reticulated vitreous carbon electrodes modified with sulfuric acid-glycine co-doped polyaniline

Improving the reduction kinetics is crucial in the electroreduction process of Cr(VI). In this study, we developed a novel adsorption-electroreduction system for accelerated removal of Cr(VI) by employing reticulated vitreous carbon electrode modified with sulfuric acid-glycine co-doped polyaniline (RVC/PANI-SA-GLY). Firstly, response surface methodology confirmed the optimum polymerization condition of co-doped polyaniline for modifying electrodes (Aniline, sulfuric acid and glycine, respectively, of 0.2 mol/L, 0.85 mol/L, 0.93 mol/L) when untraditional dopant glycine was added. Subsequently, RVC/PANI-SA-GLY showed higher Cr(VI) removal percentages in electroreduction experiments over RVC electrode modified with sulfuric acid doped polyaniline (RVC/PANI-SA) and bare RVC electrode. In contrast to RVC/PANI-SA, the improvement by RVC/PANI-SA-GLY was more significant and especially obvious at more negative potential, lower initial Cr(VI) concentration, relatively less acidic solution and higher current densities, best achieving 7.84% higher removal efficiency with entire Cr(VI) eliminated after 900 s. Current efficiencies were likewise enhanced by RVC/PANI-SA-GLY under quite negative potentials. Fourier transform infrared (FTIR) and energy dispersive spectrometer (EDS) analysis revealed a possible adsorption-reduction mechanism of RVC/PANI-SA-GLY, which greatly contributed to the faster reduction kinetics and was probably relative to the absorption between protonated amine groups of glycine and HCrO4(-). Eventually, the stability of RVC/PANI-SA-GLY was proven relatively satisfactory.