Removal of lead from aqueous solution using electrospun nanofibers: preparation, characterization, adsorption isotherm, and kinetic study.

Lead is one of the most hazardous toxic heavy metal ions in industrial wastewater. The removal of Pb(II) from aqueous environment is an extremely essential topic due to acquiring clean water resources and its significant impact on human health. Adsorption is an effective and the most widely used method for heavy metal removal from an aqueous medium. Nanofibers have potential advantages in the adsorption of heavy metal ions from wastewater. In this study, nanofibers based on polyvinyl alcohol (PVA) were fabricated for the removal of lead ions from aqueous samples. Nanofibers produced by electrospinning were characterized by scanning electron microscopy (SEM/EDX) and Fourier transform infrared (FT-IR) techniques. A batch system was used for the adsorption of Pb(II) ions onto cross-linked PVA (%10) and PVA (%10):MSs (%2) (Malva Sylestris L. seed biomaterial) nanofibers. The effectiveness of cross-linking was determined by the water absorbency test. The pH, adsorbent amount, adsorption kinetics, isotherms, and thermodynamic values were thoroughly investigated in the adsorption tests. Pb(II) adsorption on the polymer was confirmed by EDX analysis. The optimum values found were a pH of 6, an adsorbent dose of 5.0 mg, and a contact time of 120 min. Lead ion concentrations were determined by flame atomic absorption spectrometry (FAAS). The Freundlich models could explain the results from the adsorption data. Similar results were obtained from adsorption isotherm models, and the results were found to support each other. The adsorption capacity for PVA (10%) and PVA (10%):MSs (2%) nanofibers were found to be 444.2 mg g-1 and 588.2 mg g-1, respectively. The adsorption capacity increases with the addition of MSs (2%) biomaterial. As a result, nanofibers can be used as effective adsorbents in the removal of Pb(II) ions. The developed methods are environmentally friendly and promising for the separation of toxic Pb(II) ions from aqueous systems, which is a major problem for environmental pollution.

Cyclotide-rich fractions containing nanofibers by electrospinning: preparation, characterization and examination of antimicrobial activity.

In this study, antimicrobial nanofibers were produced with the mixtures of polyvinyl alcohol (PVA) and cyclotide-rich fractions by electrospinning method. After extraction, the first separation was carried out with C18 flash chromatography and then fractioned into five separate parts by reversed-phase high-pressure liquid chromatography (RP-HPLC). The molecular weights of cyclotides in each fraction were determined by quadrupole time-of-flight liquid chromatography-mass spectrometry (Q-TOF LC-MS). Cyclotide-rich fractions were mixed with 10% of PVA solution and nanofibers were produced from this biocomposite mixture by electrospinning method. The nanofibers were characterized by field emission scanning electron microscopy (FE-SEM), and it was observed that 100% peptide-containing nanofibers (cyclotide-rich fraction/10% PVA, w/v) had more regular fiber textures. The presence of the peptides in the nanofiber was also confirmed by analytical RP-HPLC, as the peptides in both peptide fractions and nanofiber solutions have the same retention times. The nanofibers produced with the fourth cyclotide-rich fraction showed activity against gram-positive bacteria (Bacillus cereus) in antimicrobial susceptibility test. As a result of these findings, cyclotide-containing nanofibers with antimicrobial activity can be produced for pharmaceutical research and development studies.

Preconcentration of trace amount Cu(II) by solid-phase extraction method using activated carbon-based ion-imprinted sorbent.

In this study, preconcentration conditions of trace amounts of copper ions were investigated with solid-phase extraction (SPE) method by synthesizing activated carbon-based ion-imprinted sorbent (Cu(II)-IAC) with a novel and selective approach. Flame atomic absorption spectrometry (FAAS) was used for the determination of metal ions concentrations. For the characterization of the sorbents, scanning electron microscopy, energy dispersive X-ray (SEM/EDX) analysis, and Fourier transform infrared spectroscopy (FTIR) were used. Optimum conditions for the SPE procedure, various parameters such as pH value, eluent type and concentration, sample volume, sample flow rate, adsorption capacity, and selectivity were studied. The adsorption isotherm was analyzed by Freundlich and Langmuir isotherm, and the maximum adsorption capacity was found to be 142.9 and 312.5 mg/g for activated carbon-based nonimprinted (Cu(II)-non-IAC) and Cu(II)-IAC sorbents, respectively from the Langmuir isotherm. Limit of determination (LOD) and limit of quantification (LOQ) values were found to be 0.038 and 0.113 µg/L, respectively for Cu(II)-IAC sorbent, and the results were compared with the literature. The accuracy and validity of the proposed method were evaluated by the determination of Cu(II) ions from tap water samples and certified reference materials (CRMs) (soft drinking water ERML-CA021e and NIST 1643e) analysis. Good and quantitative recoveries were obtained for the spiked analysis.

Chelating agent free-solid phase extraction (CAF-SPE) of Co(II), Cu(II) and Cd(II) by new nano hybrid material (ZrO2/B2O3).

New nano hybrid material (ZrO(2)/B(2)O(3)) was synthesized and applied as a sorbent for the separation and/or preconcentration of Co(II), Cu(II) and Cd(II) in water and tea leaves prior to their determination by flame atomic absorption spectrometry. Synthesized nano material was characterized by scanning electron microscope, transmission electron microscope and X-ray diffraction. The optimum conditions for the quantitative recovery of the analytes, including pH, eluent type and volume, flow rate of sample solution were examined. The effect of interfering ions was also investigated. Under the optimum conditions, adsorption isotherms and adsorption capacities have been examined. The recoveries of Co(II), Cu(II) and Cd(II) were 96 ± 3%, 95 ± 3%, 98 ± 4% at 95% confidence level, respectively. The analytical detection limits for Co(II), Cu(II), and Cd(II) were 3.8, 3.3, and 3.1 µg L(-1), respectively. The reusability and adsorption capacities (32.2 mg g(-1) for Co, 46.5 mg g(-1) for Cu and 109.9 mg g(-1) for Cd) of the sorbent were found as satisfactory. The accuracy of the method was confirmed by analyzing certified reference material (GBW-07605 Tea leaves) and spiked real samples. The method was applied for the determination of analytes in tap water and tea leaves.

Synthesis of nano B2O3/TiO2 composite material as a new solid phase extractor and its application to preconcentration and separation of cadmium.

A new solid phase extractor, nano-scale diboron trioxide/titanium dioxide composite material, was synthesized and used for separation and/or preconcentration of trace cadmium ion from various samples. The characterization of the synthesized material was performed by scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffractometer methods (XRD). The specific surface area of the material was also determined and found as 3.4m(2)/g. Analytical parameters including pH of sample solution, sample volume, flow rate of sample solution, volume and concentration of eluent for the column solid phase extraction (SPE) procedure were examined. The effect of common matrix ions on the recovery of the cadmium has also been investigated and found that they did not interfere on cadmium preconcentration. Under the optimum experimental conditions, preconcentration factor and analytical detection limit were determined as 50 and 1.44 microg/L, respectively. The reusability (stabile up to 100 run) and adsorption capacity (49 mg/g) of the sorbent were excellent. The accuracy of the method was confirmed by analyzing certified reference materials (Tea leaves GBW-07605). The results demonstrated good agreement with the certified values (relative error <10%). The precision of the method was also satisfactory. The recovery of cadmium under the optimum conditions was found to be 96+/-3% at 95% confidence level. The method was applied for the determination of cadmium in tap water and tea leaves.