Carboxy-PEG-thiol functionalized gold nanoparticle conjugates for the detection of SARS-CoV-2: Detection tools and analytical method development.

Addressing the need for accessible SARS-CoV-2 testing, carboxy-PEG 12-thiol functionalized gold nanoparticles conjugates were developed for rapid point-of-care (POC) detection against SARS-CoV-2 spike protein, pseudo-SARS-CoV-2, and authentic Beta SARS-CoV-2 virus particles. These conjugates leverage gold nanoparticles (AuNPs) as signal transducers, cross-linked to either angiotensin-converting enzyme 2 (ACE2) or SARS-CoV-2 spike protein receptor-binding domain (RBD) antibodies as bioreceptors and showed a distinct color shift from pink to blue. To assess their POC feasibility, the conjugates were integrated into facemasks and breathalyzers, wherein aerosolized SARS-CoV-2 antigens were successfully detected, producing a color change within 10 and 30 minutes for the breathalyzer and facemask prototypes, respectively. Furthermore, we explored quantitative analysis using varying concentrations of SARS-CoV-2 spike protein. Both conjugates demonstrated a linear relationship between blue color intensity and virus concentration, with linear ranges of 0.08-0.6 ng/mL and 0.04-0.5 ng/mL, respectively. Low limits of detection and quantification were also achieved. They exhibited specificity, responding solely to SARS-CoV-2 even in complex matrices containing diverse proteins, including the SARS-CoV-1 spike protein. Precision tests yielded coefficient of variations below 2 %, showcasing their remarkable reproducibility. This work presents a promising approach for rapid, sensitive, and specific POC detection of SARS-CoV-2 paving the way for improved pandemic response and management.

Preparation of Copper-Decorated Activated Carbon Derived from Platamus occidentalis Tree Fiber for Antimicrobial Applications.

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.

Metallic nickel nanoparticles supported polyaniline nanotubes as heterogeneous Fenton-like catalyst for the degradation of brilliant green dye in aqueous solution.

Metallic nanoparticles supported on porous matrices are promising heterogeneous catalysts for Fenton-like reaction towards the degradation of organic contaminants in water. Herein, novel magnetic nanocomposites (NCs) of metallic nickel (Ni0) nanoparticles and nanotubular polyaniline matrix (PANI/Ni0 NCs) were fabricated by simple reductive formation of Ni0 nanoparticles upon the pre-synthesized PANI nanotubes (NTs) surface and applied as heterogeneous Fenton-like catalyst in degrading cationic brilliant green dye (BG) in aqueous solution. Various physico-chemical characterization techniques revealed effective supporting of soft ferromagnetic well dispersed nano-dimensional Ni0 particles onto the PANI NTs matrix. Heterogeneous Fenton-like catalytic performance of PANI/Ni0 NCs for BG degradation in the presence of hydrogen peroxide (H2O2) oxidant demonstrated their superiority when compared with unsupported Ni0 nanoparticles counterpart. Experiments with a minimum 0.1 g/L of NCs and 10 mM of H2O2 displayed complete degradation of 100 mg/L BG within 120 min reaction time. Improved BG degradation was observed with increase in the dose of PANI/Ni0, H2O2 concentration and temperature, whereas it reduced with rise in initial concentration of BG. The rate of degradation was well described by the pseudo-first- order kinetic model. Six consecutive BG degradation experiments confirmed NCs reusability without loss of original (∼100%) degradation efficiency up to the fifth cycle. Finally, liquid chromatography-mass spectrometric (LC-MS) analyses of the BG samples after 120 min degradation time exposed the formation of N,N-diethylaniline as degradation product along with partial mineralization of the other end products via the attack of reactive hydroxyl radicals (HO•) produced in the catalytic system.

Polyaniline nanofibers, a nanostructured conducting polymer for the remediation of Methyl orange dye from aqueous solutions in fixed-bed column studies.

Polyaniline nanofibers (PANI NFs) were synthesized and employed as potential adsorbents in a continuous flow fixed-bed column adsorption study for an organic dye, Methyl Orange (MO) removal from water. These nanostructured adsorbents were characterized using ATR-FTIR, FE-SEM, HR-TEM, TGA, BET, XRD, XPS, and the Zeta-sizer. Morphological representations from SEM and TEM analyses showed that the fibers were nanosized with diameters lower than 80 nm and an interconnected network possessing a smooth surface. The SBET of the PANI NFs was found to be 35.80 m2/g. The impact of column design parameters for instance; influent concentration, flow rate, and bed mass was investigated using pH 4 influent MO solutions optimized through batch studies. The best influent concentration, bed length, and flow rate for this study were determined as 25 mg/L, 9 cm (6 g), and 3 mL/min, respectively. The column information was fitted in Thomas, Yoon-Nelson, and Bohart-Adams models. It appeared that the Thomas and Yoon-Nelson models described the data satisfactorily. The PANI NFs were able to treat 29.16 L of 25 mg/L MO solution at 9 cm bed length. A sulfate peak in a de-convoluted sulfur spectrum using XPS verified the successful adsorption of Methyl Orange.

Characterisation of Engineered Nanomaterials in Nano-Enabled Products Exhibiting Priority Environmental Exposure.

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.

Nickel hydroxide nanoparticles decorated napthalene sulfonic acid-doped polyaniline nanotubes as efficient catalysts for nitroarene reduction.

Nanosize nickel hydroxide decorated 2-napthalene sulfonic acid-doped polyaniline nanotubes nanocomposites (Ni(OH)2@NSA-PANI NCs) were successfully developed for the catalytic reduction of aromatic nitro compounds. The Ni(OH)2@NSA-PANI NCs were synthesised by depositing Ni(OH)2 nanoparticles onto 2-napthalene sulfonic acid doped PANI nanotubes surface. The resulting material was characterized using field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), powder X-ray diffraction (P-XRD), Fourier-transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). The prepared nanocomposite showed a remarkable ability to catalytically hydrogenate aromatic nitro compounds using sodium borohydride (NaBH4) as hydrogen source in aqueous medium at room temperature. Kinetic studies were performed using 4-nitrophenol (4-NP) as the model substrate, using the Langmuir-Hinshelwood model. The catalyst showed pseudo-first-order kinetics, with rate constants estimated between 0.08287 and 0.3649 min-1. Catalyst recyclability without reduced activity was demonstrated over 10 successive cycles. The optimised nanocomposite catalyst demonstrated a low activation energy barrier towards 4-NP reduction.

Polyaniline-Coated TiO2 Nanorods for Photocatalytic Degradation of Bisphenol A in Water.

Polyaniline (PANI)-wrapped TiO2 nanorods (PANI/TiO2), obtained through the oxidative polymerization of aniline at the surface of hydrothermally presynthesized TiO2 nanorods, were evaluated as photocatalysts for the degradation of Bisphenol A (BPA). Fourier-transform infrared spectroscopy analysis revealed the successful incorporation of PANI into TiO2 by the appearance of peaks at 1577 and 1502 cm-1 that are due to the C=C and C-N stretch of the benzenoid or quinoid ring in PANI. Brunauer-Emmett-Teller analysis revealed that PANI/TiO2 had almost double the surface area of TiO2 (44.8999 m2/g vs 28.2179 m2/g). Transmission electron microscopy (TEM) analysis showed that TiO2 nanorods with different diameters were synthesized. The TEM analysis showed that a thin layer of PANI wrapped the TiO2 nanorods. X-ray photon spectroscopy survey scan of the PANI/TiO2 nanocomposite revealed the presence of C, O, Ti, and N. Photocatalytic activity evaluation under UV radiation through the effect of key parameters, including pH, contact time, dosage, and initial concentration of BPA, was carried out in batch studies. Within 80 min, 99.7% of 5 ppm BPA was attained using the 0.2 g/L PANI/TiO2 photocatalyst at pH 10. The quantum yield (QY) of these photocatalysts was evaluated to be 9.86 × 10-5 molecules/photon and 2.82 × 10-5 molecules/photon for PANI/TiO2 and TiO2, respectively. PANI/TiO2 showed better performance than as-synthesized TiO2 with a rate constant of 4.46 × 10-2 min-1 compared to 2.18 × 10-2 min-1. The rate of degradation of PANI/TiO2 was also superior to that of TiO2 (150 mmol/g/h vs 74.89 mmol/g/h). Nitrate ions increased the rate of degradation of BPA, while humic acid consistently inhibited the degradation of BPA. LC-MS analysis identified degradation products with m/z 213.1, 135.1, and 93.1. The PANI/TiO2 nanocomposite was reused up to five cycles with a removal of at least 80% in the fifth cycle. LC-MS results revealed three possible BPA degradation intermediates. LC-MS analysis identified degradation products which included protonated BPA, [C14H13O2 +], and [C9H11O+]. The PANI/TiO2 nanocomposite demonstrated superior photocatalytic activity with respect to improved QY and figure of merit and lower energy consumption.

Crosslinked chitosan embedded TiO2 NPs and carbon dots-based nanocomposite: An excellent photocatalyst under sunlight irradiation.

Herein, a new hybrid nanocomposite, comprising of titania nanoparticles (TiO2 NPs) and carbon dots (CDs) deposited polyvinyl imidazole crosslinked chitosan [cl-Ch-p(VI)/TiO2NPs-CDs] has been developed. The nanocomposite has been synthesised by in-situ deposition of TiO2 NPs and CDs onto the surface of the copolymer under microwave irradiation. To the best of our knowledge, this in-situ approach has effectively been applied for the first time to fabricate green fluorescent CDs from sugar cane juice at moderate temperature (75 °C) under microwave irradiation. The developed nanocomposite has been characterized using UV-Vis spectroscopy, 13C NMR, XRD, HR-TEM, STEM and XPS analyses. The results suggest that the successful deposition of TiO2 NPs and CDs onto the surface of crosslinked chitosan is achieved. The experimental studies indicate that the NPs/CDs-impregnated nanocomposite allows efficient photocatalytic degradation of toxic organic compounds (~98.6% degradation of 2,4-dicholorophenol, ~95.8% degradation of Reactive Blue 4, ~98.2% degradation of Reactive Red 15) in the presence of sunlight. Finally, LC-MS analysis of the resultant degraded materials reveals the formation of organic molecules with lower molecular mass.

Polypyrrole-coated gum ghatti-grafted poly(acrylamide) composite for the selective removal of hexavalent chromium from waste water.

The aim of this study was to synthesize a gum ghatti-g-poly(acrylamide)/polypyrrole composite using a multi-step aqueous polymerization method, in which the pyrrole monomer was absorbed into the network of the gum ghatti-acrylamide graft copolymer followed by the polymerization of the pyrrole monomers, and use it for the removal of Cr(VI) from water. The prepared was characterized using FT-IR, SEM, BET, XPS and XRD. The effects of the pH, adsorbent dose, contact time, concentration of Cr(VI), and temperature on the adsorption performance of the composite were investigated systematically. The adsorption of Cr(VI) on the composite depended strongly on the pH, and a Cr(VI) removal of 99.6% was attained at pH 2.0, initial concentration of Cr(VI) of 100 mg/L, and adsorbent dosage of 0.035 g. The kinetics of the adsorption followed a pseudo-second order model and the adsorption data fitted well the Langmuir isotherm model. The maximum adsorption capacity of the adsorbent at 298, 308, and 318 K was determined to be 321.5, 357, and 416 mg/g, respectively. The presence of coexisting ions in the solution did not affect the adsorption of Cr(VI) significantly. Adsorption-desorption experiments revealed that the synthesized polymer composite could be used for up to four consecutive cycles.

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.

Removal of Congo red from aqueous solution by adsorption using gum ghatti and acrylamide graft copolymer coated with zero valent iron.

Gum ghatti (Gg) and acrylamide (AAm) grafted copolymer [poly (Gg-AAm)] coated by zero valent iron (ZVI) was developed to remove toxic Congo red (CR) from waste water. Prepared composite, [poly (Gg-AAm)/ZVI] was characterized by FESEM, TEM, BET, FTIR and XRD. CR adsorption from water using [poly (Gg-AAm)/ZVI] was investigated and several parameters discussed, such as solution pH, contact time, dosage and temperature to find out removal efficiency of polymer composite. The kinetic data for the adsorption of CR followed the pseudo-second-order model and the Langmuir maximum adsorption capacity for CR at pH 7.0 were found to be 153.8, 200 and 250 mg/g at 25, 35 and 45 °C correspondingly. Desorption studies revealed that prepared composite can be used up to three cycles efficiently and thermodynamic parameters such as Gibbs free energy (ΔG0), enthalpy (ΔH0) and entropy (ΔS0) changes showed the adsorption of CR onto [poly (Gg-AAm)/ZVI] was feasible, spontaneous and endothermic.

Removal of toxic pollutants from aqueous media using poly (vinyl imidazole) crosslinked chitosan synthesised through microwave assisted technique.

Water contamination owing to the presence of toxic organic chemicals/heavy metals are considered to be one of the serious global environmental issues. Various advanced polymeric materials have been developed and used for the separation/removal of these contaminants. To consider the afore-mentioned problem, recently in authors' laboratory, an efficient biopolymeric adsorbent has been prepared using poly (vinyl imidazole) crosslinked chitosan (cl-Ch-pVI) through a simple microwave-assisted free radical polymerization technique. The structural characteristics of the developed hydrogel have been studied in details. The copolymer cl-Ch-pVI reveals excellent gel characteristics, demonstrates superior efficiency towards removal of toxic Cr(VI) from aqueous solution. Moreover, the copolymer also shows outstanding adsorption capacity to remediation of organic dye reactive black 5 (RB5), which manifests the potential application of synthesised copolymer in wastewater treatment.

Hydrous CeO2-Fe3O4 decorated polyaniline fibers nanocomposite for effective defluoridation of drinking water.

Hydrous CeO2-Fe3O4 (HCeFe) decorated polyaniline nanofibers (HCeFe NFs) were obtained through a simple co-precipitation deposition approach on pre-synthesized polyaniline nano-fibers (PANI NFs), and evaluated as adsorbents for fluoride removal from synthetic and real water samples. Field emission scanning electron microscopy/energy dispersive X-ray spectroscopy (FE-SEM/EDS), high resolution-transmission electron microscopy (HR-TEM), Braunauer-Emmett-Teller (BET), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric-differential thermal analysis (TGA-DTA), X-ray photoelectron spectroscopy (XPS) and dynamic mechanical analysis (DMA) techniques were used to characterize the hybrid nanomaterials. The optimised HCeFe NFs adsorbent with specific surface area 66 m2/g, exhibited excellent adsorption efficiency towards fluoride ions (F-) via both electrostatic interactions and ion exchange mechanisms. F- adsorption followed the pseudo-second-order rate model and best fitted the Langmuir isotherm, with the maximum capacities within 93.46-117.64 mg/g over a broad pH range 3-10, respectively. The determined thermodynamic parameters, including enthalpy (ΔH°â€¯- 15.1 kJ/mol) and Gibbs free energies change (ΔG°â€¯< 0) indicated to the exothermic and a spontaneous nature of the sorption process. The regeneration of HCeFe NFs showed a considerable adsorption-desorption efficiency over three consecutive cycles. Ultimately, the adsorbent was tested on spiked F- containing groundwater and the obtained results demonstrated its potential utility for defluoridation of natural water.

Fixed-bed operation for manganese removal from water using chitosan/bentonite/MnO composite beads.

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.

Fe-polyaniline composite nanofiber catalyst for chemoselective hydrolysis of oxime.

A facile chemoselective one-pot strategy for the deprotection of oxime has been developed using Fe0-polyaniline composite nanofiber (Fe0-PANI), as a catalyst. Nano material based Fe0-PANI catalyst has been synthesized via in-situ polymerization of ANI monomer and followed by reductive deposition of Fe0 onto PANI matrix. The catalyst was characterized by FE-SEM, HR-TEM, BET, XRD, ATR-FTIR, XPS and VSM techniques. The scope of the transformation was studied for aryl, alkyl and heteroarylketoxime with excellent chemoselectivity (>99%). Mechanistic investigations suggested the involvement of a cationic intermediate with Fe3+ active catalytic species. Substituent effect showed a linear free energy relationship. The activation energy (Ea) was calculated to be 17.46 kJ mol-1 for acetophenone oxime to acetophenone conversion. The recyclability of the catalyst demonstrated up to 10 cycles without any significant loss of efficiency. Based on the preliminary experiments a plausible mechanism has been proposed involving a carbocationic intermediate.

Synthesis and characterization of alginate beads encapsulated zinc oxide nanoparticles for bacteria disinfection in water.

The use of polymer nanocomposites as novel materials for water remediation has emerged as a promising alternative for disinfection of bacteria contaminated water. Sodium alginate, a natural biopolymer has been investigated in this study by encapsulating antimicrobial zinc oxide nanoparticles supported bentonite. The confirmation of the alginate nanocomposites was done by use of TEM, SEM-EDS and XRD. The antimicrobial activity of the alginate nanocomposites was investigated by batch studies using surface water and synthetic bacteria contaminated water containing Staphylococcus aureus. The effect of nanocomposite amount and initial bacteria concentration has been studied. The inactivation results indicated that the nanocomposite effectively inactivated bacteria in both the synthetic and surface water. With an amount of 0.5 g of the nanocomposites, no bacteria was observed in the water after 70 min of contact time with initial bacteria concentration of 200 cfu/ml for synthetic water and within a min, no bacteria was observed in the water for surface water. It is worth noting that 200 cfu/ml is the bacteria concentration range in which environmental water is likely to contain. Therefore, the results of this study have indicated that the alginate nanocomposites can be deemed as a potential antimicrobial agent for water disinfection.

Hydrous ZrO2 decorated polyaniline nanofibres: Synthesis, characterization and application as an efficient adsorbent for water defluoridation.

A new hybrid material comprising hydrous zirconium oxide (HZrO2) supported onto polyaniline (PANI) nanofibres (HZrO2@PANI NFs) was prepared via the precipitation of HZrO2 onto as-synthesized PANI NFs and tested for its defluoridation capabilities. The developed adsorbent (HZrO2@PANI NFs) was fully characterized by FTIR, BET, XRD, SEM-EDX, TEM-(S)TEM, XPS, and zeta potential measurements. HZrO2@PANI NFs achieved 2-fold BET surface area ∼86.64 m2/gas compared to PANI NFs ∼44.72 m2/g, implying that the incorporation of HZrO2 onto the PANI nanofibres enhanced the available surface area for effective fluoride adsorption. Moreover, HZrO2@PANI NFs was found to be effective over a wide pH range (3-9) as designated by its high pHpzc ∼9.8. The adsorption kinetics obeyed the pseudo-second-order model well with equilibrium attainment in 30min. Adsorption isotherm was best described by the Langmuir model and the maximum adsorption capacities obtained were 83.23 and 28.77mg/g at pH 3 and 6.5, respectively, which is superior to most ZrO2 based adsorbents reported in the literature and better than that of native PANI. Furthermore, the developed adsorbent manifested quite a selective fluoride uptake at pH 3 as compared to pH 6.5±0.1 wherein significant chemical affinity competition was presented by phosphate ions followed by bicarbonate and sulfate. The recyclability of HZrO2@PANI NFs for four cycles and its applicability to fluoride spiked ground water has also been demonstrated. The adsorption mechanism was interpreted with the help of FTIR, XPS and Zeta potential analysis and the results revealed the involvement of both anion exchange and electrostatic attraction in the adsorption of F- ions. Thus, a new efficient adsorbent with reasonably high adsorption capacity and superior pH tolerance has been developed for fluoride removal.

Synthesis and characterization of Fe0/TiO2 nano-composites for ultrasound assisted enhanced catalytic degradation of reactive black 5 in aqueous solutions.

In the present study, nanocomposites (NCs) of zero valent iron nanoparticles (Fe0 NPs) and titanium dioxide nanoparticles (Fe0/TiO2 NCs) were prepared by coating Fe0 NPs onto the surface of TiO2 NPs through borohydride reduction of Fe(II) salt for the ultrasound assisted removal/ degradation of reactive black 5 (RB5) dye from aqueous solutions. Morphological and structural characterizations of the Fe0/TiO2 NCs were performed by FE-SEM, HR-TEM, XRD, XPS and Brunauer-Emmett-Teller (BET) method. The Fe0/TiO2 NCs exhibited highly efficient ultrasonic degradation/decolourization of RB5, compared to TiO2 NPs counterpart. In the presence of ultrasonic irradiation, 0.25g/L of Fe0/TiO2 NCs showed complete removal of 100mg/L RB5 dye within 10min of reaction. An increase in RB5 removal efficiency was obtained with decrease in initial concentration and solution pH, whereas it was decreased with decrease in the amount of Fe0/TiO2 NCs. The rate of RB5 degradation was in good agreement with the pseudo-first-order kinetic model. Higher RB5 removal efficiency was observed at a higher ultrasonic power level. Coexisting NO3- and SO42- ions had only a minor impact on the removal of RB5, whereas, CO32- ions considerably affected the% removal of RB5 using Fe0/TiO2 NCs. Regeneration/reusability experiments revealed that Fe0/TiO2 NCs could be reused efficiently up to 7th removal cycle without considerable loss of their original RB5 removal performance. Liquid chromatography-mass spectrometry (LC-MS) study, used for the detection of the RB5 degradation products showed that the degradation mechanism proceeds via the reductive cleavage of the azo linkage of the dye which produced 1-sulfonic, 2(4-aminobenzenesulfonyl) ethanol as the stable end product.

Batch equilibrium and kinetics of mercury removal from aqueous solutions using polythiophene/graphene oxide nanocomposite.

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.

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.