Yashan Zhang

Potassium modified layered Ln2O2CO3 (Ln: La, Nd, Sm, Eu) materials: efficient and stable heterogeneous catalysts for biofuel production.

Potassium modified layered Ln2O2CO3 (Ln: La, Nd, Sm, Eu) biodiesel catalysts were prepared by a coprecipitation method followed by an overnight reflux. A high fatty acid methyl ester (FAME) yield (>95%) was achieved under mild reaction conditions (<100 °C). The FAME yields were investigated as a function of temperature and catalyst weight percentage. Nd2O2CO3 shows a better catalytic performance with a higher reaction rate than the industrial homogeneous KOH catalyst using both microwave irradiation and conventional heating methods. Approximately 100% FAME yield can be reached at 95 °C (microwave radiation) by 1.0 wt% Nd2O2CO3 within 10 min, while the same yield can be reached by 3.0 wt% Nd2O2CO3 at 95 °C (conventional heating method). In addition, leaching tests of the catalysts were performed; no leached rare earth metal ions were detected and the amounts of leached potassium were all under 5 ppm (ASTM standard). The synthesized layered Ln2O2CO3 materials offer a group of ideal alternative catalysts for industrial biodiesel production.

Cadmium Removal from Aqueous Solution by a Deionization Supercapacitor with a Birnessite Electrode

Birnessite is widely used as an excellent adsorbent for heavy metal ions and as active electrode materials for supercapacitors. The occurrence of redox reactions of manganese oxides is usually accompanied by the intercalation-deintercalation of cations during the charge-discharge processes of supercapacitors. In this study, based on the charge-discharge principle of the supercapacitor and excellent adsorption properties of birnessite, a birnessite-based electrode was used to remove Cd2+ from aqueous solutions. The Cd2+ removal mechanism and the influences of birnessite loading and pH on the removal performance were investigated. The results showed that Cd2+ was adsorbed on the surfaces and interlayers of birnessite, and the maximum electrosorption capacity of birnessite for Cd2+ was about 900.7 mg g-1 (8.01 mmol g-1), which was significantly higher than the adsorption isotherm capacity of birnessite (125.8 mg g-1). The electrosorption specific capacity of birnessite for Cd2+ increased with an increase in initial Cd2+ concentration and decreased with an increase in the loading of active birnessite. In the pH range of 3.0-6.0, the electrosorption capacity increased at first with an increase in pH and then reached equilibrium above pH 4.0. This work provides a new method for the highly efficient adsorption of Cd2+ from polluted wastewater.

Zinc removal from aqueous solution using a deionization pseudocapacitor with a high-performance nanostructured birnessite electrode

Manganese oxides are widely studied as heavy metal ion adsorbents and pseudocapacitor electrode materials. Synthesis methods affect the crystal structure, particle size, micromorphology, and the corresponding physicochemical properties of manganese oxides. In this work, nanostructured birnessite was readily obtained through hydrothermal reaction of KMnO4 and β-cyclodextrin under microwave irradiation. Based on the working principle of pseudocapacitors, the nanostructured birnessite was used as an electrode material for Zn2+ removal from aqueous solution by multi-cycle galvanostatic charge–discharge. The effects of electrolyte pH and birnessite mass on Zn2+ removal capacity were further investigated. The results indicate that the Zn2+ removal capacity increases and decreases with the increase of pH and birnessite mass, respectively. The highest Zn2+ removal capacity reaches 530.0 mg g−1, which is remarkably higher than the adsorption isotherm capacity (56.1 mg g−1). The significant improvement of electrochemical removal capacity can be attributed to the nanostructure and the not fully reversible redox reaction of the birnessite. The result of X-ray absorption fine structure (XAFS) indicates that Zn2+ is adsorbed above/below the vacancies and is inserted into the interlayer of birnessite, leading to the transformation of birnessite to Zn-buserite and hetaerolite during the charge–discharge process. The present study proposes a facile method for the rapid synthesis of nanostructured birnessite and highly efficient removal of Zn2+ from aqueous solution.

Pulsed‐laser deposition of magnetic alloys

Targets of SmCo5 and Pr2Fe17 are ablated with a quadrupled Nd:YAG pulsed laser operating at 266 nm with fluence levels of ≊2 J cm−2. The plasmas are condensed on r‐plane sapphire (Al2O3) maintained either at ambient room temperature of ≊400 °C. Preliminary results indicate that Sm+n and Co+n recombine on room temperature substrates to form an alloy with a‐axis orientation that is consistent with an hkl〈200〉 d‐spacing for hexagonal SmCo5. Rare‐earth and Fe plasmas condense at ≊400 °C to form alloys with c‐axis orientation as indicated by a single narrow hkl〈006〉 reflection with a HHFW of about Δ(2θ)=0.4°. When codeposited with N2, an interstitial alloy Re2Fe17N3−δ can be formed. These newly discovered metastable alloys display high Curie temperatures (Tc), large magnetization and anisotropy fields desirable for permanent magnet applications. Preliminary XRD, (SQUID) magnetometry and Auger surveys are presented together with speculation about future work.