Heavy metal removal with magnetic coffee grain

The presence of heavy metals in environmental waters having an important place in the industrial waste is a major threat to viability. Heavy metals are transported to humans through the ecological cycle, damaging many tissues and organs. In recent years, agricultural and food waste can be used to remove heavy metals. At the present study, magnetically modified coffee grains which are alternative to conventional particle systems were prepared and heavy metal removal performances were investigated. The coffee grains used were magnetically modified by contact with water-based magnetic fluid. Magnetically modified coffee grains were characterized by scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area analysis and electron spin resonance (ESR). Adsorption studies are made with four different heavy metal ions, namely Cu(II), Pb(II), Cd(II) and Zn(II). Adsorption isotherms were determined and heavy metal removal performance of magnetic coffee grains were investigated from synthetic waste water.     

Synthesis and Characterization of the Germanium Sulfonate Ge(CH3SO3)2 – a 3D Coordination Network Solid

The reaction of germanium(II)‐bis(2‐methoxyphenyl)methoxide with methanesulfonic acid provides the germanium(II) sulfonate Ge(CH₃SO₃)₂ ( 1 ), which was characterized by X‐ray diffraction, elemental analysis, NMR spectroscopy, and IR spectroscopy. The decomposition process of 1 was investigated by thermal gravimetric analysis (TGA) and temperature‐dependent X‐ray powder diffraction (PXRD) and both are consistent with the formation of GeO₂ as major final product. Single crystal X‐ray diffraction at 110 K revealed the chiral tetragonal space group P4₁2₁2 and formation of a three‐dimensional (3D) coordination network solid. The 3D network is composed of interconnected twenty four‐membered rings comprising bridging methanesulfonate groups, which link the germanium atoms.     

Photo-degradation of yperite over V, Fe and Mn-doped titania-silica photocatalysts

The photocatalytic decomposition of yperite (bis(2-chloroethyl)sulfide), a chemical warfare agent, was achieved by using titania-silica catalysts doped with several transition metal ions. The preparation of these catalysts was achieved by impregnation of a titania-silica mixed oxide previously synthesized using a sol-gel route with salts of the doping elements (vanadium, iron, manganese). The above catalysts were characterized using several spectroscopic techniques: FTIR, Raman, DR-UV-Vis, and XPS. The band gap energy was measured for each photocatalytic system. The reaction was carried out in two different types of reactors, i.e. naturally aerated and a closed quartz tube aerated under a constant flow, and using two types of irradiation, UV-Vis and Vis. The investigated systems proved to be extremely active, leading to an almost complete degradation of yperite in 2 h of irradiation. An excellent correlation between the photocatalytic performances and the band gap has been found. Based on the characterization data and on the temporal evolution of the reaction products, a reaction mechanism has been suggested. This mechanism considers two distinct pathways for the decomposition of yperite, namely the C-S bond cleavage and the S oxidation.     

On the asymptotic behavior of the solutions of semilinear nonautonomous equations

We consider nonautonomous semilinear evolution equations of the form $$\frac{dx}{dt}= A(t)x+f(t,x) . $$ Here A(t) is a (possibly unbounded) linear operator acting on a real or complex Banach space $\mathbb{X}$ and $f: \mathbb{R}\times\mathbb {X}\to\mathbb{X}$ is a (possibly nonlinear) continuous function. We assume that the linear equation (1) is well-posed (i.e. there exists a continuous linear evolution family {U(t,s)}_(t,s)∈Δ such that for every s∈?₊ and x∈D(A(s)), the function x(t)=U(t,s)x is the uniquely determined solution of Eq. (1) satisfying x(s)=x). Then we can consider the mild solution of the semilinear equation (2) (defined on some interval [s,s+δ),δ>0) as being the solution of the integral equation $$x(t) = U(t, s)x + \int_s^t U(t, \tau)f\bigl(\tau, x(\tau)\bigr) d\tau,\quad t\geq s . $$ Furthermore, if we assume also that the nonlinear function f(t,x) is jointly continuous with respect to t and x and Lipschitz continuous with respect to x (uniformly in t∈?₊, and f(t,0)=0 for all t∈?₊) we can generate a (nonlinear) evolution family {X(t,s)}_(t,s)∈Δ , in the sense that the map $t\mapsto X(t,s)x:[s,\infty)\to\mathbb{X}$ is the unique solution of Eq. (4), for every $x\in\mathbb{X}$ and s∈?₊. Considering the Green’s operator $(\mathbb{G}{f})(t)=\int_{0}^{t} X(t,s)f(s)ds$ we prove that if the following conditions hold

• the map $\mathbb{G}{f}$ lies in $L^{q}(\mathbb{R}_{+},\mathbb{X})$ for all $f\in L^{p}(\mathbb{R}_{+},\mathbb{X})$ , and
• $\mathbb{G}:L^{p}(\mathbb{R}_{+},\mathbb{X})\to L^{q}(\mathbb {R}_{+},\mathbb{X})$ is Lipschitz continuous, i.e. there exists K>0 such that $$\|\mathbb{G} {f}-\mathbb{G} {g}\|_{q} \leq K\|f-g\|_{p} , \quad\mbox{for all}\ f,g\in L^p(\mathbb{R}_+,\mathbb{X}) , $$

then the above mild solution will have an exponential decay.     

Reduction of bowl-shaped hydrocarbons: dianions and tetraanions of annelated corannulenes

[structure: see text] The reduction of several annelated corannulene derivatives was undertaken using lithium and potassium metals. It was found that annelation affects the annulenic character of corannulene by changing its charge distribution; the dianions of derivatives that are annelated with six-membered rings have less annulenic character and are less paratropic than corannulene dianion. This effect is even more pronounced in corannulenes that are peri-annelated with five-membered rings. The alkali metal used in the reduction process has a great influence on the outcome, especially on the degree of reduction. Most derivatives get reduced to tetraanions only with potassium, and not with lithium, the exception being systems that can stabilize the tetraanion with lithium by special means, such as aggregation or dimerization. One such system is cyclopenta[bc]corannulene (acecorannulylene), which gives a coordinative dimer that consists of two cyclopentacorannulene tetraanions, bound together in a convex-convex fashion by lithium cations. The points of contact in this dimer are two rehybridized carbons from each cyclopentacorannulene unit, which are bridged together by two lithium cations.     

On the class groups of cyclotomic extensions in presence of a solution to Catalan's equation

Catalan's conjecture states that the equation xp−yq=1 has no other integer solutions but ³²−²³=1. We investigate the consequences of existence of further solutions (with odd prime exponents p,q) upon the relative class group of the pth cyclotomic extension. We thus obtain several new results which merge into the condition

     

Infinitely many solutions for elliptic problems with variable exponent and nonlinear boundary conditions

We analyze a class of quasilinear elliptic problems involving a p(·)-Laplace-type operator on a bounded domain W ì \mathbb R^N{\Omega\subset{\mathbb R}^N}, N ≥ 2, and we deal with nonlinear conditions on the boundary. Working on the variable exponent Lebesgue–Sobolev spaces, we follow the steps described by the “fountain theorem” and we establish the existence of a sequence of weak solutions.     

Experimental demonstration of a passive all-fiber Q-switched erbium- and samarium-doped laser

Self-Q-switched operation of the all-fiber laser using erbium and samarium fibers in the cavity is realized experimentally. This passively Q-switched all-fiber laser produces very stable pulses with energy of 142 nJ and duration of 450 ns. The experimental results were well reproduced by the results obtained through the numerical integration of a rate-equations model.     

Neue Tetrathiocyanato-diamin-Chromiate mit tertiären aliphatischen Aminen

New Tetrathiocyanato Diamine Chromiates with Tertiary Aliphatic Amines Three new Reinecke salt like complexes: [Cr(NCS)₄(amine)₂]^? were obtained by means of substitution reactions of anhydrous K₃[Cr(NCS)₆] with triethyl-, tripropyl-, and tributylamine, respectively, without solvent. The formulae of the new complex anions were established by preparation of 63 derivatives with the hydrochlorides of some amines and alkaloides, with metal ions and cobalt(III) amine bases, respectively. The electronic and i.r. spectra of some derivatives were recorded. Some structural problems were discussed on the basis of spectral data.