A review on sources,toxicity and remediation technologies for removing arsenic from drinking water

Arsenic is a natural element found in the environment in organic and inorganic forms. The inorganic form is much more toxic and is found in ground water, surface water and many foods. This form is responsible for many adverse health effects like cancer (skin, lung, liver, kidney and bladder mainly), and cardiovascular and neurological effects. The estimated number of people in Bangladesh in 1998 exposed to arsenic concentrations above 0.05 mg/l is 28–35 million, and the number of those exposed to more than 0.01 mg/l is 46–57 million. The estimated number of people in West Bengal, India (the border province to Bangladesh), in 1997 actually using arsenic-rich water is more than 1 million for concentrations above 0.05 mg/l and is 1.3 million for concentrations above 0.01 mg/l. The United States Environmental Protection Agency (USEPA) has estimated that 13 million of the US population are exposed to arsenic in drinking water at 0.01 mg/l. The situation has prevailed for more than 10 years and is more severe now. The USEPA lowered the maximum contaminant level (MCL) for drinking water arsenic from 50 to 10 μg/l in 2001 based on international data analysis and research. This recommendation is now on hold. The level of 10 ppb become standard in the European Union (EU) in 2001. Arsenic may be found in water flowing through arsenic-rich rocks. The source is diverse. These include the earth's crust, introduced into water through the dissociation of minerals and ores, industrial effluents to water, combustion of fossil fuels and seafoods. Arsenic-removal methods are coagulation (ferric sulfate, ferrous sulfate, ferric chloride, aluminum sulfate, copper sulfate, and calcium hydroxide as coagulants), adsorption (activated carbon, activated alumina, activated bauxite) ion exchange, bio-sorption, etc.     

para-Selective Arylation of Arenes: A Direct Route to Biaryls by Norbornene Relay Palladation

Biaryl compounds are extremely important structural motifs in natural products, biologically active components and pharmaceuticals. Selective synthesis of biaryls by distinguishing the subtle reactivity difference of distal arene C−H bonds are significantly challenging. Herein, we describe para-selective C−H arylation, which is acheived by a unique combination of a meta-directing group and norbornene as a transient mediator. Upon direct meta-C−H palladation, one-bond relay palladation occurs in presence of norbornene and subsequently para-C−H arylation is achieved for sulfonates, phosphonates and phenols bearing 2,6-disubstitution patterns. The protocol is amenable to electron-deficient aryl iodides. Multisubstituted arenes and phenols are obtained by postsynthetic modification of the products. The protocol allows the synthesis of hexa-substituted benzene by sequential selective distal C−H functionalization.     

Thermal conductivity of deep eutectic solvents

Journal of Thermal Analysis and Calorimetry - We have reported the thermal conductivities of three deep eutectic solvents (DESs). We have used choline chloride, N,N-diethyl ethanol ammonium...     

Oxidation of Ru(III)‐Bound Thiocyanate with Peroxomonosulfate: Kinetic and Mechanistic Studies

The reaction of [Ru^III(edta)(SCN)]^2? (edta^4? = ethylenediaminetetraacetate; SCN^? = thiocyanate ion) with the peroxomonosulfate ion (HSO₅^?) has been studied by using stopped‐flow and rapid scan spectrophotometry as a function of [Ru^III(edta)], [HSO₅^?], and temperature (15–30ºC) at constant pH 6.2 (phosphate buffer). Spectral analyses and kinetic data are suggestive of a pathway in which HSO₅^? effects the oxidation of the coordinated SCN^? by its direct attack at the S‐atom (of SCN^?) coordinated to the Ru^III(edta). The high negative value of entropy of activation (ΔS^≠ = ?90 ± 6 J mol^?1 deg^?1) is consistent with the values reported for the oxygen atom transfer process involving heterolytic cleavage of the O‐O bond in HSO₅^?. Formation of SO₄^2?, SO₃^2?, and OCN^? was identified as oxidation products in ESI‐MS experiments. A detailed mechanism in agreement with the spectral and kinetic data is presented.     

Laser phase modulation approaches towards ensemble quantum computing

Selective control of decoherence is demonstrated for a multilevel system by generalizing the instantaneous phase of any chirped pulse as individual terms of a Taylor series expansion. In the case of a simple two-level system, all odd terms in the series lead to population inversion, while the even terms lead to self-induced transparency. These results also hold for multiphoton transitions that do not have any lower-order photon resonance or any intermediate virtual state dynamics within the laser pulse width. Such results form the basis of a robustly implementable CNOT gate.     

Coded nanoscale self-assembly

We demonstrate coded self-assembly in nanostructures using the code seeded at the component level through computer simulations. Defects or cavities occur in all natural assembly processes including crystallization and our simulations capture this essential aspect under surface minimization constraints for self-assembly. Our bottom-up approach to nanostructures would provide a new dimension towards nanofabrication and better understanding of defects and crystallization process.      

Period adding bifurcation in a logistic map with memory

We introduce a single step memory dependence in the fully chaotic logistic map. This makes it a two dimensional system in general. However, we show that by using composite functions to define two one dimensional maps, it is possible to obtain some analytic results for the bifurcation structure. Numerical results support the calculated bifurcation scheme and, in addition, yield a further insight which allows the calculation of the convergence ratio for a new period adding scenario.     

Highly selective colorimetric fluorescence sensor for Cu: cation-induced ‘switching on’ of fluorescence due to excited state internal charge transfer in the red/near-infrared region of emission spectra

A 1,8-naphthalimide-based colorimetric fluorescence perinone dye, receptor 1 is reported herein for the selective detection of Cu²⁺ over the other heavy and transition metal ions. Receptor 1 shows a strong colorimetric change from orange to purple and a dramatic enhancement of fluorescence intensity due to cation-induced excited state internal charge transfer during the sensing event, that is, a dual optical response that would facilitate naked-eye detection of Cu²⁺.     

Colloidal Microcapsules: Self‐Assembly of Nanoparticles at the Liquid–Liquid Interface

Colloidal microcapsules (MCs) are highly modular, inherently multiscale constructs of capsules stabilized by nano‐/microparticle shells, with applications in many areas of materials and biological sciences, such as drug delivery, encapsulation, and microreactors. Until recently, fabrication of colloidal MCs focused on the use of submicron‐sized particles because the smaller nanoparticles (NPs) are inherently unstable at the interface owing to thermal disorder. However, stable microcapsules can now be obtained by tuning the interactions between the nanometer‐sized building blocks at the liquid–liquid interface. This Review highlights recent developments in the fabrication of colloidal MCs using NPs.     

High sensitive measurements of absorption coefficient and optical nonlinearities

Accurate knowledge of absorption coefficient of a sample is a prerequisite for measuring the third-order optical nonlinearity of materials, which can be a serious limitation for unknown samples. We introduce a method, which measures both the absorption coefficient and the third-order optical nonlinearity of materials with high sensitivity in a single experimental arrangement. We use a dual-beam pump-probe experiment and conventional single-beam z-scan under different conditions to achieve this goal with communication relevant wavelength. We also demonstrate a counterintuitive coupling of the non-interacting probe-beam with the pump-beam in pump-probe z-scan experiment.