3D hierarchical flower-like Mg-Al-layered double hydroxides (Mg-Al-LDHs) were synthesized by a simple solvothermal method in a mixed solution of ethylene glycol (EG) and water. The formation mechanism of the flower-like Mg-Al-LDHs was proposed. After calcination, the flower-like morphology could be completely preserved. With relatively high specific surface areas, Mg-Al-LDHs and calcined Mg-Al-LDHs with 3D hierarchical nanostructures were tested for their application in water purification. When tested as adsorbents in As(V) and Cr(VI) removal, the as-prepared calcined Mg-Al-LDHs showed excellent performance, and the adsorption capacities of calcined Mg-Al-LDHs for As(V) and Cr(VI) were better than those of Mg-Al-LDHs. The adsorption isotherms, kinetics and mechanisms for As(V) and Cr(VI) onto calcined Mg-Al-LDHs were also investigated. The high uptake capability of the as-prepared novel 3D hierarchical calcined Mg-Al-LDHs make it a potentially attractive adsorbent in water purification. Also, this facile strategy may be extended to synthesize other LDHs with 3D hierarchical nanostructures, which may find many other applications due to their novel structural features.

Porous micro-/nanostructured MgO were successfully synthesized through a facile method. Flower-like and nest-like micro-/nanostructured MgO were obtained by adjusting the concentration of precipitant. When tested as adsorbent in arsenic removal, the as-prepared micro-/nanostructured MgO were effective for both As(III) and As(V) removal, particularly the As(III). The adsorption capacities of these micro-/nanostructured MgO for As(III)/As(V) are much higher than those reported for other micro-/nanostructured metal oxides. The adsorption kinetics and adsorption mechanism for As(III) and As(V) onto micro-/nanostructured MgO were also investigated. The high uptake capability of the as-prepared micro-/nanostructured MgO make it a potentially attractive adsorbent for the removal of both As(III) and As(V) from water.

Polycrystalline nickel wires with an average length of 10 µm and diameter of about 200 nm were prepared at 70°C by a hydrothermal process with a 0.25 T magnetic field applied. Studies show that the magnetic field induced one-dimensional assembly of acicular Ni nanocrystallites with dimensions of 200 nm in length and 10-30 nm in diameter, leading to the formation of the polycrystalline nickel wires. Magnetic measurements show saturation magnetization (Ms) of the sample prepared in a 0.25 T external magnetic field is higher than that of the sample synthesized without an external magnetic field applied. It is suggested that the one-dimensional self-assembly of acicular nickel nanocrystallites with their magnetic easy axes [111] aligned along the magnetic line of force results in the improvement of the magnetic properties.