T. Hayat

Synergistic coagulation of GO and secondary adsorption of heavy metal ions on Ca/Al layered double hydroxides

With the extensive application of graphene oxide (GO), it is noticeable that part of GO is directly/indirectly released into the environment and widespread research indicated that it had adverse influences on human health and ecological balance. In this work, a novel nanobelt-like Ca/Al layered double hydroxides (CA-LDH) was synthesized and applied as efficient coagulant for the removal of GO from aqueous solutions. The results indicated that neutral pH, co-existing cations and higher temperature were beneficial to the coagulation of GO. The sequence of cation effect for promoting of GO coagulation was Ca2+xa0>xa0Mg2+xa0>xa0K+xa0>xa0Na+, whereas the effect of anions on GO coagulation was PO43-xa0>xa0CO32-xa0>xa0SO42-xa0>xa0Cl-. Comparing with anions, the cations showed more dominate effect for GO coagulation than anions. Hydrogen bonds and electrostatic interaction were the main coagulation mechanisms for GO coagulation, which were evidenced by FT-IR and XPS analysis. Specifically, for the first time, the reclaimed product of CA-LDH after GO coagulation (CA-LDHxa0+xa0GO) was applied as adsorbents for the secondary application in the removal of heavy metal ions from aqueous solutions. Interestingly, the CA-LDHxa0+xa0GO still had high adsorption capacities, i.e., the maximum adsorption capacities (qmax) for Cu(II), Pb(II), and Cr(VI) were 122.7xa0mg/g, 221.2xa0mg/g and 64.4xa0mg/g, respectively, higher than other similar materials. This paper highlighted the LDH-based nanomaterials are promising materials for the elimination of environmental pollutants and the migration and transformation of carbon nanomaterials in the natural environment.

Enhanced immobilization of U(VI) on Mucor circinelloides in presence of As(V): Batch and XAFS investigation

The combined pollution of radionuclides and heavy metals has been given rise to widespread concern during uranium mining. The influence of As(V) on U(VI) immobilization by Mucor circinelloides (M.xa0circinelloides) was investigated using batch experiments. The activity of antioxidative enzymes and concentrations of thiol compounds and organic acid in M.xa0circinelloides increased to respond to different U(VI) and As(V) stress. The morphological structure of M.xa0circinelloides changed obviously under U(VI) and As(V) stress by SEM and TEM analysis. The results of XANES and EXAFS analysis showed that U(VI) was mainly reduced to nano-uraninite (nano-UO2, 30.1%) in U400, while only 9.7% of nano-UO2 was observed in the presence of As(V) in U400-As400 due to the formation of uranyl arsenate precipitate (Trögerite, 48.6%). These observations will provide the fundamental data for fungal remediation of uranium and heavy metals in uranium-contaminated soils.

CATTANEO–CHRISTOV HEAT FLUX MODEL FOR SQUEEZED FLOW OF THIRD GRADE FLUID

This paper addresses the squeezed flow of third grade fluid between two parallel disks. Heat transfer in present flow is characterized by Cattaneo–Christov theory. Thermal relaxation time effects on the boundary layer is examined. Suitable transformations are invoked for a system of ordinary differential equations. Convergent series solutions are thus obtained using homotopic approach. Influences of different parameters on the velocity and temperature profile are discussed.