Transport of surface-modified iron nanoparticle in porous media and application to arsenic(III) remediation

The surface-modified iron nanoparticles (S-INP) were synthesized, characterized and tested for the remediation of arsenite (As(III)), a well known toxic groundwater contaminant of concern. The S-INP material was fully dispersed in the aqueous phase with a particle size distribution of 2–10 nm estimated from high-resolution transmission electron microscopy (HR-TEM). X-ray photoelectron spectroscopy (XPS) revealed that an Fe(III) oxide surface film was present on S-INP in addition to the bulk zero-valent Fe⁰ oxidation state. Transport of S-INP through porous media packed in 10 cm length column showed particle breakthroughs of 22.1, 47.4 and 60 pore volumes in glass beads, unbaked sand, and baked sand, respectively. Un-modified INP was immobile and aggregated on porous media surfaces in the column inlet area. Results using S-INP pretreated 10 cm sand-packed columns containing ∼2 g of S-INP showed that 100 % of As(III) was removed from influent solutions (flow rate 1.8 mL min⁻¹) containing 0.2, 0.5 and 1.0 mg L⁻¹ As(III) for 9, 7 and 4 days providing 23.3, 20.7 and 10.4 L of arsenic free water, respectively. In addition, it was found that 100% of As(III) in 0.5 mg/L solution (flow rate 1.8 mL min⁻¹) was removed by S-INP pretreated 50 cm sand packed column containing 12 g of S-INP for more than 2.5 months providing 194.4 L of arsenic free water. Field emission scanning electron microscopy (FE-SEM) showed S-INP had transformed to elongated, rod-like shaped corrosion product particles after reaction with As(III) in the presence of sand. These results suggest that S-INP has great potential to be used as a mobile, injectable reactive material for in-situ sandy groundwater aquifer treatment of As(III).     

Lysozyme coated DNA and DNA/SWNT fibers by solution spinning

DNA fibers were prepared by solution spinning of DNA in a lysozyme (LSZ) coagulation/gelation bath. Strong positive charges carried by LSZ protein condensed the DNA (strong negative charged) molecules resulting in self‐assembly and the formation of fibrillar structures in a gel‐like network. DNA/LSZ fibril formation was found to be dependent on the ratio of DNA to LSZ. A minimum 0.1 wt.‐% of LSZ was necessary to condense 0.1 wt.‐% of DNA into micro‐fibrils. Macroscopic fiber spinning was possible by introducing a 0.1 wt.‐% DNA aqueous solution into a 0.2 wt.‐% LSZ coagulation bath which resulted in fibers with ≈20 µm diameter. Single‐walled carbon nanotubes (SWNT) were also incorporated into these fibers to explore the possibility for creating hybrid materials. All DNA‐based fibers exhibit strong birefringence confirming molecular orientation along the fiber axis. Due to the presence of LSZ, the fibers exhibit antimicrobial activity against bacteria like Micrococcus lysodeikticus.

     

Spectral statistics of random Schrödinger operator with growing potential

In this work we investigate the spectral statistics of random Schrödinger operators acting on where are i.i.d random variables distributed uniformly on [0,1].     

The Fischer–Marsden conjecture and contact geometry

In this paper, we consider the Fischer–Marsden conjecture within the frame-work of K-contact manifolds and \((\kappa ,\mu )\)-contact manifolds. First, we prove that a complete K-contact metric satisfying \(\mathcal {L}^{*}_g(\lambda )=0\) is Einstein and is isometric to a unit sphere \(S^{2n+1}\). Next, we prove that if a non-Sasakian \((\kappa ,\mu )\)-contact metric satisfies \(\mathcal {L}^{*}_g(\lambda )=0\), then \( M^{3} \) is flat, and for \(n > 1\), \(M^{2n+1}\) is locally isometric to the product of a Euclidean space \(E^{n+1}\) and a sphere \(S^n(4)\) of constant curvature \(+\,4\).     

Quantitative Estimation of Ruthenium(III) Using Morpholine-4-Carbodithioate as a New Analytical Reagent

Ruthenium(III) has been precipitated gravimetrically in the pH range 7.0-8.5 with morpholine-4-carbodithioate and determined by weighing as a black complex (C₅H₆ONS₂)₃ Ru after drying at l00–110°C. The interference of the various metal ions has been avoided by using an ammonical mixture of EDTA and tartrate (1:1 molar ratio). The complex is thermally stable up to l60°C.