Heterostructured zero valent iron-montmorillonite nanohybrid and their catalytic efficacy

Nanohybrid catalysts that comprised montmorillonite (Mt) matrix and embedded zero-valent Fe nanoparticle are presented. In this process, clay particles are used as 2-dimensional template that induce the growth of intercalated nanomaterials. Fe polycations are first embedded within the interlayer space and then reduced to Fe nanoparticles through thermal annealing in reducing atmosphere. Structural studies using electron microscopy and high energy X-ray show that the intercalated status of the polycations dictates the crystal structure, shape and size of final Fe compound particles. The magnetic property and caltalytic efficacy of hybrid particles have been verified using magnetometer measurement and Fenton reaction. Hybrized α-Fe nanoparticles show high magnetization inherent to zero valent Fe, and high catalytic efficacy in decomposing Rhodamine B due to their zero valency and large surface areas. This simple synthesis process of stable iron nanoparticle without organic agents will be beneficial for large scale production of highly effective catalysts exploiting controlled phase and shape of embedded nanoparticles. © 2012 Elsevier B.V.

Rheological behavior of clay-nanoparticle hybrid-added bentonite suspensions: Specific role of hybrid additives on the gelation of clay-based fluids

Two different types of clay nanoparticle hybrid, iron oxide nanoparticle clay hybrid (ICH) and Al2O3-SiO2 nanoparticle clay hybrid (ASCH), were synthesized and their effects on the rheological properties of aqueous bentonite fluids in steady state and dynamic state were explored. When ICH particles were added, bentonite particles in the fluid cross-link to form relatively well-oriented porous structure. This is attributed to the development of positively charged edge surfaces in ICH that leads to strengthening of the gel structure of the bentonite susensions. The role of ASCH particles on the interparticle association of the bentonite fluids is different from that of ICH and sensitive to pH. As pH of ASCH-added bentonite suspensions increased, the viscosity, yield stress, storage modulus, and flow stress decreased. In contrast, at low pH, the clay suspensions containing ASCH additives were coagulated and their rheological properties become close to those of ICH added bentonite fluids. A correlation between the net surface charge of the hybrid additives and the rheological properties of the fluids indicates that the embedded nanoparticles within the interlayer space control the variable charge of the edge surfaces of the platelets and determine the particles association behavior of the clay fluids. © 2011 American Chemical Society

Characterization of ZnO nanoparticle suspension in water: Effectiveness of ultrasonic dispersion

Suspensions of ZnO nanoparticles in water were prepared with the two-step powder dispersion process using several methods of ultrasonication. The dispersion of ZnO was found to proceed by a fragmentation process, with minimum achievable particle size in the range 50 to 300 nm. This is consistent with other oxide nanopowder systems, in which most primary particulates still remain in hardened aggregates that cannot be further reduced. A submersible accelerometer probe was developed and used to measure the relative ultrasonic energy field in the liquid for the various ultrasonication methods. Oscillation at the expected frequencies was identified in each case, with strong variability at different locations in the liquid volume. © 2009 Elsevier B.V. All rights reserved