Removal of Arsenic (III) from groundwater applying a reusable Mg-Fe-Cl layered double hydroxide

BACKGROUND: Layered double hydroxide compounds (LDHs) have been applied for the removal of oxyanions including arsenate (As(V)). However, the aim of this present research is to develop a LDH to treat arsenite (As(III)). Both batch and column sorption studies were conducted to assess the effect of LDH dosage, contact time, solution pH and initial As(III) concentrations on the As(III) removal performance. The potential re-use of this sorbent was also investigated.<p></p> RESULTS: For 2 g L−1 of Mg-Fe-Cl LDH, As(III) in test solution can be reduced from 400 µg L−1 to <10 µg L−1 after a contact time of 2 h. High As(III) concentration in Bangladesh groundwater can be reduced to meet the national drinking water standards (<50 µg L−1). The maximum adsorption capacity of As(III) by Mg-Fe-Cl LDH is 14.6 mg g−1-LDH. Further, reusability of this sorbent was at least 20 cycles of regeneration with effective As(III) removal between 93.0 and 98.5%. Moreover, As(III) removal was unaffected by the solution pH but affected by the co-existing competing anions and concentration of As(III). Finally, the main mechanism of As(III) removal by Mg-Fe-Cl LDH was suggested to be chemical sorption together with anion and ligand exchange with interlayer Cl− and OH− ions.<p></p> CONCLUSION: High efficiency of sorption of As(III) by the developed Mg-Fe-Cl LDH was demonstrated in this study which is generally not the case for most other sorbent materials. Pilot-scale trials are needed to explore the suitability of full application of the developed Mg-Fe-Cl LDH for the removal of As(III).<p></p&gt

Hamiltonian Theory of the Composite Fermion Wigner Crystal

Experimental results indicating the existence of the high magnetic field Wigner Crystal have been available for a number of years. While variational wavefunctions have demonstrated the instability of the Laughlin liquid to a Wigner Crystal at sufficiently small filling, calculations of the excitation gaps have been hampered by the strong correlations. Recently a new Hamiltonian formulation of the fractional quantum Hall problem has been developed. In this work we extend the Hamiltonian approach to include states of nonuniform density, and use it to compute the excitation gaps of the Wigner Crystal states. We find that the Wigner Crystal states near $\nu=1/5$ are quantitatively well described as crystals of Composite Fermions with four vortices attached. Predictions for gaps and the shear modulus of the crystal are presented, and found to be in reasonable agreement with experiments.Comment: 41 page, 6 figures, 3 table

Carbon nanotube (CNT) composite surfaces for electrical contact interfaces

MEMS relays boast numerous advantages over PIN diode and FET devices, for example: lower on-resistance, higher isolation and cut-off frequency. There are two common implementations of MEMS switches: capacitively coupled and metal-contacting. Whilst the use of capacitive switches at low frequencies is limited, they tend to be capable of surviving high numbers (&gt;500,000,000) of switching cycles without showing any signs of mechanical failure. For metal-contacting switches, the electrical contacts are mechanically brought into contact without the presence of a dielectric layer on the contacts, consequently enabling the transmission of DC to high frequency signals. A combination of electrical and mechanical factors result in degradation of the contact surfaces over consecutive opening and closing processes which ultimately result in switch failure.The use of gold-coated multi-walled carbon nanotube (Au/MWCNT) bilayer composites have been investigated as a method for improving the reliability of switch contacts. Using a gold-coated MEMS cantilever beam to test the composite contacts. With a load current of 50 mA (load voltage 4 V), the use of a composites contact resulted in a switching lifetime in excess of 44,000,000 hot switching cycles. With a load current of 10 mA, the lifetime is in excess of 500,000,000 cycles. The use of Au/MWCNT composites offer a promising solution to enhance the lifetime of MEMS switches.<br/

Human monoclonal antibodies that neutralize anthrax toxin by inhibiting heptamer assembly

A panel of human anti-anthrax protective antigen IgG1 monoclonal antibodies were evaluated to determine the mechanism of toxin neutralization. AVP-22G12, AVP-1C6 and AVP-21D9 bound to the protective antigen with picomolar affinities to distinct non-overlapping linear epitopes. Two of the antibodies neutralized the anthrax toxin by completely inhibiting the protective antigen oligomer assembly process in vitro