Heavy metal removal using SnO2 nanoparticles prepared in a grape extract media

SnO2 nanoparticles were first synthesized using a grape extract media, then characterized by XRD, FE-SEM, TEM, BET, and DLS techniques, and finally used as an efficient adsorbent for the removal of Pb2+ and Cd2+ ions from wastewater. The prepared sample had a tetragonal phase with an average crystallite size of 41 nm (XRD analysis), a specific surface area of 47.08 m2.g-1 (BET method)/46.25 m2.g-1 (BJH method), and a pore diameter of 6.49 nm (BJH method). The best conditions for adsorbing were a 30 ppm concentration of metal ions, ambient temperature, pH of 6, and 0.025 g of an adsorbent. The maximum adsorption for Pb and Cd ions was 97 and 93%, respectively. The Elovich model was matched as the most suitable kinetic model, indicating that the adsorption mechanism is chemical adsorption. The negative values of ΔG (Pb: -6.38 kJ.mol-1; Cd: -4.16 kJ.mol-1) represent the spontaneousness of the adsorption process. The negative values of the parameters ΔH (Pb: -63.0 kJ.mol-1; Cd: -42.95  kJ.mol-1) and ΔS (Pb: -188.8 J.mol-1; Cd: -128.4 J.mol-1) represent the exothermic nature of the adsorption

Deposition of nanostructured fluorine-doped hydroxyapatite-polycaprolactone duplex coating to enhance the mechanical properties and corrosion resistance of Mg alloy for biomedical applications

The present study addressed the synthesis of a bi-layered nanostructured fluorine-doped hydroxyapatite (nFHA)/polycaprolactone (PCL) coating on Mg-2Zn-3Ce alloy via a combination of electrodeposition (ED) and dip-coating methods. The nFHA/PCL composite coating is composed of a thick (70-80 μm) and porous layer of PCL that uniformly covered the thin nFHA film (8-10 μm) with nanoneedle-like microstructure and crystallite size of around 70-90 nm. Electrochemical measurements showed that the nFHA/PCL composite coating presented a high corrosion resistance (Rp = 2.9 × 103 kΩ cm2) and provided sufficient protection for a Mg substrate against galvanic corrosion. The mechanical integrity of the nFHA/PCL composite coatings immersed in SBF for 10 days showed higher compressive strength (34% higher) compared with the uncoated samples, indicating that composite coatings can delay the loss of compressive strength of the Mg alloy. The nFHA/PCL coating indicted better bonding strength (6.9 MPa) compared to PCL coating (2.2 MPa). Immersion tests showed that nFHA/PCL composite-coated alloy experienced much milder corrosion attack and more nucleation sites for apatite compared with the PCL coated and uncoated samples. The bi-layered nFHA/PCL coating can be a good alternative method for the control of corrosion degradation of biodegradable Mg alloy for implant applications

Microstructural, mechanical properties and corrosion behavior of plasma sprayed NiCrAlY/nano-YSZ duplex coating on Mg-1.2Ca-3Zn alloy

In this study, microstructural evolution, mechanical properties and corrosion behavior of plasma sprayed NiCrAlY/nano-yttria stabilized zirconia (nano-YSZ) dual-layered coating on Mg-1.2Ca-3Zn alloy were investigated. NiCrAlY underlayer is composed of large amount of porosities and micro-cracks with thickness around 80-90 µm. However, nano-YSZ overlayer shows bimodal microstructure consisting of columnar grains and some partially molten parts of the nanostructured powders with thickness around 270-300 µm. The microhardness of dual-layered NiCrAlY/nano-YSZ coating is significantly higher than that of single-layered NiCrAlY. Despite that, the bonding strength of dual-layered coating is slightly higher than single-layered plasma sprayed coating. Results also showed that both single-layer NiCrAlY and dual-layer NiCrAlY/nano-YSZ coatings decreased the corrosion current density of Mg alloy from 217.1 µA/cm2 to 114.5 and 82.4 µA/cm2, respectively