Magnetic nitrogen-doped activated carbon improved biohydrogen production

Low biological hydrogen (bioH2) production due to non-optimal metabolic pathways occurs frequently. In this work, magnetic nitrogen-doped activated carbon (MNAC) was prepared and added into the inoculated sludge with glucose as substrate to enhance hydrogen (H2) yield by mesophilic dark fermentation (DF). The highest H2 yield appeared in 400 mg/L AC (252.8 mL/g glucose) and 600 mg/L MNAC group (304.8 mL/g glucose), which were 26.02% and 51.94% higher than that of 0 mg/L MNAC group (200.6 mL/g glucose). The addition of MNAC allowed for efficient enrichment of Firmicutes and Clostridium-sensu-stricto-1, accelerating the metabolic pathway shifted towards butyrate type. The Fe ions released by MNAC facilitated electron transfer and favored the reduction of ferredoxin (Fd), thereby obtaining more bioH2. Finally, the generation of [Fe-Fe] hydrogenase and cellular components of H2-producing microbes (HPM) during homeostasis was discussed to understand on the use of MNAC in DF system.

3D construct of hydroxyapatite/zinc oxide/palladium nanocomposite scaffold for bone tissue engineering

The purpose of this study was to produce and characterize Hydroxyapatite/Zinc Oxide/Palladium (HA/0.05 wt% ZnO/0.1 wt% Pd) nanocomposite scaffolds and study their mechanical and antibacterial properties, biocompatibility and bioactivity. The initial materials were developed using sol-gel and precipitation methods. Scaffolds were characterized using atomic absorption analysis (AA), scanning electron microcopy (SEM), energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM), atomic force microscopy (AFM) and Brunauer-EmmeS-Teller (BET) method. Furthermore, the bioactivity of scaffolds in simulated body fluid (SBF) and the interaction of dental pulp stem cells (DPSCs) with the nanocomposite scaffolds were assessed. Our results showed that the HA/ZnO/Pd (H1), HA/ZnO/Pd coated by 0.125 g chitosan (H2) and HA/ZnO/Pd coated by 0.25 g chitosan (H3) scaffolds possess higher compressive strength and toughness and lower microhardness and density compared to the pure HA (H0) scaffolds. Immersion of samples in SBF showed the deposition of apatite on the surface of the scaffolds. The biocompatibility assay indicated lower cell proliferation on the H1, H2 and H3 in comparison to the H0. The antibacterial results obtained show a significant impact by loading Pd/ZnO on HA in the deactivation of microorganisms in vitro.

Performance of dissolved organic matter removal from membrane bioreactor effluent by magnetic powdered activated carbon

Magnetic powdered activated carbon (Mag-PAC) was successfully developed and applied as an adsorbent for dissolved organic matter (DOM) removal from the effluent of a membrane bioreactor (MBR) using batch experiments. The results show that a coating of iron oxide particles is consistently distributed on the surface of powdered activated carbon (PAC), resulting in a decrease in the specific surface area and in the pH at the point of zero charge, even though the particle sizes of Mag-PAC and PAC were similar. A Mag-PAC dosage of 4 g/L exhibited efficient and fast DOM adsorption with a relatively short contact time of 5 min. The iron oxide coating on the surface of PAC may play an important role in the DOM removal efficiency. Temkin isotherm and pseudo-second order kinetic models well described the DOM adsorption, suggesting that the adsorption of DOM onto Mag-PAC could be mainly governed by a chemisorption mechanism. Humic acid- and fulvic acid-like compounds and aromatic DOM with molecular weights (MWs) between 2610 Da and 3030 Da were efficiently removed by Mag-PAC, whereas aromatic DOM with an MW of 1760 Da was poorly removed. Our results demonstrate that the application of Mag-PAC for DOM adsorption is attractive and yields benefits as a posttreatment system for MBR effluent due to its efficient and fast DOM adsorption.

Fabrication of calixarene-grafted magnetic nanocomposite for the effective removal of lead(II) from aqueous solution

Magnetic nanocomposites adorned with calixarene were successfully prepared by immobilizing diethanolamine functionalized p-tert-butylcalix[4]arene (DEA-Calix) onto silica-coated magnetic nanoparticles (MNPs). The synthesis, surface morphology, purity, elemental composition and thermal stability of newly prepared nanocomposites were analyzed using FT-IR spectroscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX), X-ray diffractometer (XRD), thermal gravimetric analysis (TGA) and vibrating sample magnetometer (VSM). Magnetic solid-phase adsorption (MSPA) was employed to explore the adsorption behavior of DEA-Calix-MNPs towards Pb(II) from water samples prior to its flame atomic absorption spectrometric analysis. The essential analytical factors governing the adsorption efficiency such as solution pH, mass of adsorbent, concentration and contact time have been investigated and optimized. The results depict that DEA-Calix-MNPs has excellent adsorption efficiency 97% (at pH 5.5) with high adsorption capacity of 51.81 mg g^-1 for Pb(II) adsorption. Additionally, kinetic and equilibrium studies suggested that Pb(II) adsorption process follows a pseudo-second-order model and Langmuir isotherms, respectively. Real sample analysis also confirmed field applicability of the new DEA-Calix-MNPs adsorbent.

A novel natural chitosan/activated carbon/iron bio-nanocomposite: Sonochemical synthesis, characterization, and application for cadmium removal in batch and continuous adsorption process

The natural chitosan was synthesized using shrimp shells via sonochemical method, and activated carbon produced from grape stalks biomass. The novel bio-nanocomposite of chitosan/activated carbon/iron nanoparticles was synthesized via the sonochemical method and characterized using FTIR, SEM, and BET techniques. This bio-based nanocomposite was utilized to cadmium removal from dilute solution. The adsorption process via batch method was optimized, and the impacts of pH of feed, the dosage of adsorbent, and concentration of cadmium were analyzed. The kinetics and equilibrium analysis was done, and results indicate the predomination of chemical absorption and the single-layer adsorption process. Langmuir data indicates that the synthesized bio-nanocomposite can adsorb 344 mg cadmium per each gram. To evaluate the ability of the synthesized nanocomposite in the industrial application, the adsorption tests were done in a continuous adsorption system in three cycles.

Porous Fe0/C ceramsites for removal of aqueous Pb(ii) ions: equilibrium, long-term performance and mechanism studies

This study reports the equilibrium, long-term performance and mechanisms in removing Pb(ii) ions by metallic iron/carbon (Fe0/C) ceramsites (FCC). The Pb(ii) removal equilibrium data was analyzed using the Langmuir, Freundlich and Dubinin-Radushkevich isotherms. At the FCC dosage of 1.14 g L-1, 95.97% of Pb(ii) ions were removed from 50 mg L-1 Pb(ii) solution at initial pH 6.0. The Langmuir isotherm could fit well with the data at initial pH 3.0 with a maximum monolayer adsorption capacity of 112.36 mg g-1 at 25 °C, while the data obtained at initial pH 6.0 could be described by the Freundlich model, indicating multilayer adsorption of Pb species on the FCC. Column tests demonstrated that FCC achieved the highest Pb(ii) removal of 65.86% after 12 days' run compared to 32.35% for Fe0/activated carbon couples and only 1.24% for activated carbon. The X-ray diffraction and X-ray photoelectron spectroscopy analysis revealed that the PbO (dominant Pb species), Pb0, asisite and plumbojarosite appeared after Pb(ii) removal. Scanning electron microscopy with energy dispersive X-ray spectroscopy showed that PbO particles with numerous structures were deposited on the FCC surface in a high amount. The decrease of the Fe/C mass ratio from 7.5 : 1 to 0.298 : 1 revealed that microscale Fe0 could been readily corroded by forming galvanic couples between Fe0 and carbon. The mechanisms of Pb(ii) removal by the FCC were proposed.