Highest Qm Research Articles

Hard piezoelectric properties of lead‐free BiFeO3–BaTiO3 ceramics

AbstractHard piezoelectric properties are investigated in lead‐free BiFeO3–BaTiO3 (BF–BT) ceramics. Rhombohedral (R) phase ceramics of (1 – x)BF–xBT (x = 0.20–0.30) were prepared using a conventional solid‐state reaction and water‐quenching process. The R structure is observed in x = 0.20–0.275, and the R and tetragonal phases coexist at x = 0.30. The piezoelectric charge sensor coefficient (d33) and electromechanical planar coupling factor (kp) increase with increasing BT content, whereas the mechanical quality factor (Qm) decreases. The x = 0.20 ceramic shows the best hard piezoelectric properties: the highest Qm = 403 and the highest TC = 607°C. In contrast, x = 0.30 ceramic shows soft piezoelectric properties: d33 = 301 pC/N and kp = 0.33 with TC = 510°C. These results show that the BF–BT system in R‐phase‐rich region has good hard piezoelectric properties for transducer applications.

Structural and electrical properties of Zr-doped K0.48Na0.52NbO3 ceramics: “Hard” lead-free piezoelectric

The structural and electrical properties of K0.48Na0.52Nb1−xZrxO3−δ (x=0–0.04) ceramics prepared by the conventional solid-state reaction method were studied. Pellets with composition x≤0.03 sintered at 1125°C for 2h showed single-phase of potassium sodium niobate (KNN) perovskite structure. Based on X-ray diffraction and Raman results, a mixture of orthorhombic and monoclinic phases was observed in intermediate compositions. The addition of Zr improved the sinterability and the “hard” piezoelectric properties of KNN, increasing the Ec and Qm values. The composition with x=0.03 presented the highest permittivity at room temperature, ɛr′=363 and the lowest dielectric losses, tanδ=0.027. Moreover, it was the sample with the highest Qm and d33 values, with Qm=1781 and d33=82pC/N. It was therefore the best compositions to obtain a “hard” piezoelectric material based on Zr-doped KNN, which makes it promising candidate for use as “hard” lead-free piezoelectric material for high power applications.

Hydrothermal synthesis temperature induces sponge-like loose silica structure: A potential support for Fe2O3-based adsorbent in treating As(V)-contaminated water

Low cost Fe2O3-based sorbents with an exceptional selectivity toward the targeted As(V) pollutant have gained extensive attention in water treatment. However, their structural features often influence removal performance. In this respect, we present herein a rational design of silica-supported Fe2O3 sorbents with an enhanced morphological structure based on a simple temperature-induced process. Low-hydrothermal temperature synthesis (60 and 100 °C) provided a large silica-cluster size with a close packed structure (S-60 and S-100), contributing to an increase in mass transport resistance. Fe2O3/S-60 with 6.2-nm pore width silica achieved a maximum As(V) uptake capacity (qm) of only 3.5 mg g−1. Supporting Fe2O3 on S-100 with an approximately two-fold increase in the pore size (13 nm) did not lead to any evident enhancement in qe (3.7 mg g−1). However, expanding the pore window up to 22.6 nm (S-140) and 39.5 nm (S-180), along with changing from close-packed to sponge-like loose structures induced by high-temperature synthesis (140 °C and 180 °C), resulted in substantial increases in qm. Fe2O3/S-140 had 1.7 and 1.6 times higher qm (5.9 mg g−1) than Fe2O3/S-100 and Fe2O3/S-60, respectively. The highest qm (7.4 mg g−1) was achieved for Fe2O3/S-180, which was attributed to its relatively small-sized silica cluster and the largest cavities that facilitated easier access by As(V) to adsorbing sites.

Selective and effective adsorption of cesium ions by metal hexacyanoferrates (MHCF, M = Cu, Co, Ni) modified chitosan fibrous biosorbent

Selective and effective adsorptive removal of radiocesium is of great importance in terms of nuclear waste management and environmental remediation, but is still challenging because of its radioactive and non-complexing nature. Herein, metal hexacyanoferrates (MHCF, M = Cu, Co, or Ni) modified fibrous chitosan was prepared by multiple sequential adsorption and self-assembly approach, and applied for the selective and effective adsorption of Cs+. The physically supported MHCF in chitosan fibers showed good crystallinity and stability, and the obtained fibrous composite has high specific surface area (18.2–29.4 m2 g−1). Moreover, MHCF crystals endowed the fibrous chitosan-based adsorbent with a high adsorption capacity and selectivity towards Cs+. Its adsorption kinetic and isotherm performance followed the pseudo second-order model and the Sips model. The qm value of three fibrous MHCF/chitosan (M = Cu, Co, or Ni) composites was 24.9–70.3 mg g−1. The fibrous CuHCF/chitosan composite had the highest qm among the three composites. In summary, the modified chitosan can selectively and effectively remove Cs+ from complicated aqueous solutions.

Synthesis of starch nanoparticles with controlled morphology and various adsorption rate for urea

Starch nanoparticles (SNPs) with different morphology and particle size can be prepared by modulating the reaction conditions over SNPs preparation. This study was to synthesize various SNPs by using ultrasound assisted nanoprecipitation method, and characterized by particle size analysis, SEM and XRD performing. SNPs were successfully produced via nanoprecipitation and the particle size were controlled in the range of 95 to 150 nm. Moreover, variously different morphologies were obtained when using corn, potato or Trichosanthes kirilowii pulp (TKP) starch to produce nanoparticles, including fiber, flake and film. Results shown film TKP SNPs demonstrated an improved urea adsorption rate to 135.60 mg/g with the highest qm at 1.00 mg/mL. SNPs can be developed using ultrasound assisted nanoprecipitation method and the particle size together with surface morphology can be varied according to the source of starch and preparation method, while surface morphology is the key factor in altering adsorption performance.

Adsorption of pharmaceuticals from biologically treated municipal wastewater using paper mill sludge-based activated carbon.

A waste-based alternative activated carbon (AAC) was produced from paper mill sludge under optimized conditions. Aiming its application in tertiary wastewater treatment, AAC was used for the removal of carbamazepine, sulfamethoxazole, and paroxetine from biologically treated municipal wastewater. Kinetic and equilibrium adsorption experiments were run under batch operation conditions. For comparison purposes, they were also performed in ultrapure water and using a high-performance commercial AC (CAC). Adsorption kinetics was fast for the three pharmaceuticals and similar onto AAC and CAC in either wastewater or ultrapure water. However, matrix effects were observed in the equilibrium results, being more remarkable for AAC. These effects were evidenced by Langmuir maximum adsorption capacities (qm, mgg-1): for AAC, the lowest and highest qm were 194 ± 10 (SMX) and 287 ± 9 (PAR), in ultrapure water, and 47 ± 1 (SMX) and 407 ± 14 (PAR), in wastewater, while for CAC, the lowest and highest qm were 118 ± 7 (SMX) and 190 ± 16 (PAR) in ultrapure water and 123 ± 5 (SMX) and 160 ± 7 (CBZ) in wastewater. It was found that the matrix pH played a key role in these differences by controlling the surface electrostatic interactions between pharmaceutical and AC. Overall, it was evidenced the need of adsorption results in real matrices and demonstrated that AAC is a promising option to be implemented in tertiary wastewater treatments for pharmaceuticals' removal. Graphical abstract Production of an alternative activated carbon (AC) comparing favourably with a commercial AC in the removal of neutral and positive pharmaceuticals from wastewater.

A novel polymer-grafted hydrophobic charge-induction chromatographic resin for enhancing protein adsorption capacity

Hydrophobic charge-induction chromatography (HCIC) is a developing technology for antibody purification. To enhance the protein adsorption capacity, a novel polymer-grafted HCIC resin was developed, in which the surface-initiated activator generated by electron transfer (AGET) atom transfer radical polymerization (ATRP) was explored as a controlled polymerization technique to reconstruct matrix structure and ligand distribution. Using poly(glycidyl methacrylate, GMA) as grafting polymer and 2-mercapto-1-methyl-imidazole (MMI) as functional ligand, poly(GMA)-grafted HCIC resins were prepared with series of grafting and ligand densities. Adsorption behaviors of human immunoglobulin G (hIgG) on the prepared resins demonstrated the necessity of controlling grafting and ligand density. Saturated adsorption capacity (Qm) and effective pore diffusivity (De) reached the maximum under medium ligand density when the grafting density was kept constant. The highest Qm and De values were found under the highest grafting density, which were 73% and 7.17times higher than the non-grafted resin, respectively. Column breakthrough tests indicated that the dynamic binding capacity of the resin with optimized grafting density and ligand density was up to 34.6mg/g when linear velocity was 300cm/h, which was 86.3% higher than dextran-grafted resin. The resin was then used to separate hIgG from a protein mixture (hIgG/human serum albumin=1:4), high purity (>99%) and recovery (>90%) of hIgG were found with 50-cycle reuses, which verified the selectivity and robustness of G-MMI resin prepared. In general, the surface-initiated AGET ATRP provides a controlled grafting strategy to improve protein binding capacity for chromatographic separation, and new resins developed have great potential in large-scale protein purification applications.

Recyclable composite nanofiber adsorbent for Li+ recovery from seawater desalination retentate

Composite poly(acrylonitrile) (PAN) nanofibers with H1.6Mn1.6O4 (HMO) lithium ion-sieves were prepared, characterized and tested for lithium ion (Li+) recovery. Nanofibers were prepared by electrospinning 10 wt% HMO/PAN dope solutions in dimethylformamide with varied HMO loadings. Characterizations performed via XRD, SEM-EDS, capillary flow porometry and mechanical testing revealed highly porous, mechanically and chemically stable composite nanofibers with high water absorption capacity. The similar nanofiber diameters (<300 nm) and HMO particle sizes (<100 nm) rendered PAN as a binder to have minimal hindrance to the HMOs. Exposure of HMOs on the fiber surface provided good accessibility to the Li+ source, as indicated by the minimal loss of Li+ adsorption capacity of HMOs in PAN as compared to the support-free powdered HMO. All tested adsorbents followed Langmuir-type Li+ adsorption (qm). Increased HMO loadings resulted in improved adsorption performance as more HMOs were exposed on fiber surface and became less affected by the binder; the highest qm = 10.3 mg/g obtained from 60 wt% HMO/PAN was only 4% lower than the support-free HMO. Adsorption loss after ten reuses was minor (<4%), which suggests the long-term stability of HMO/PAN. In seawater desalination retentate, HMO/PAN (60 wt%) preferentially adsorbed Li+ over other cations, achieving 99–5312 Li+ separation factors and high Li+ distribution coefficient (KD = 770). Li+ was concentrated up to 486 times while interfering cations were enriched only up to <7 times. Overall results demonstrate the potential use and recyclability of the developed HMO/PAN composite nanofiber for Li+ recovery from seawater or other prospective sources.

Effects of organic management on water-extractable organic matter and C mineralization in European arable soils

In this study we tested the hypothesis that water-extractable organic carbon (WEOC) content and its properties can be used to distinguish conventionally (CONV) from organically (ORG) managed arable soils as responsible for C mineralization. We sampled soils at three different European sites located in Mediterranean (Italy) and continental (Switzerland) regions under conventional and organic management. The Mediterranean sites are here called CVI and LSI and the continental one DOK. The main difference between the two management systems (ORG and CONV) at all sites was the amount of organic fertilizer yearly added into the soil: in the ORG systems 2.2–2.5 Mg C year −1 were added as organic fertilizer, while in the CONV systems only mineral fertilizers were used. Moreover, the crop rotation was different between the two management systems at first two sites (7 years-crop vs. 4 years-crop rotation), while at DOK site a 7 years-crop rotation was adopted in both managements. In these soils we analyzed C mineralization rate expressed as percentage of mineralized C in a 90-day incubation with respect to soil total organic C (qM), the content of water-extractable organic carbon (WEOC), its initial composition by fluorescence spectroscopy (humification index – HIX) and its biodegradability (ΔWEOC). The Mediterranean basic soil accumulated more organic C showing a more complex WEOC than continental acid soil. Moreover, among management practices the crop rotation seemed to be one of the most important factor affecting WEOC properties and C mineralization rate (qM). In particular the highest qM and WEOC content were observed in both systems with 7 years-crop rotation including pasture, such as alfalfa or grass clover, according to the order ORG(DOK) = CONV(DOK) > ORG(LSI) > ORG(CVI). With respect to the effect of the management systems on C mineralization rate and WEOC properties, significant differences of WEOC content were observed between ORG and CONV soils at all sites (5.7 vs. 7.7; 14.5 vs. 17.9; 6.8 vs. 13.5 at CVI, DOK and LSI, respectively), whereas qM and HIX were significantly different only at the Mediterranean sites (qM: 4.4 vs. 5.8 and 6.6 vs. 8.2; HIX: 9.4 vs. 13.7 and 3.4 vs. 13.6 at CVI and LSI, respectively). Therefore, we can conclude that WEOC content is not a generally applicable parameter to distinguish conventionally from organically managed soils as responsible for C mineralization. Specific cropping systems, soil properties and climate conditions should be considered as important factors affecting mineralization process and WEOC properties.