Efficiency of succinylated-olive stone biosorbent on the removal of cadmium ions from aqueous solutions

Chemical functionalization of olive stone wastes with succinate linkers can potentially improve the performance of wastewater treatment technologies via enhanced adsorption and high affinity of the covalently attached succinate groups for heavy metals. In this study, a novel reusable adsorbent material based on agricultural waste has been synthesized by esterifying the lignocellulosic matrix of olive stones with succinic anhydride in toluene under basic conditions. Characterization of the as-prepared material by FTIR and solid-state MAS ¹³C NMR spectroscopies and TGA confirmed that the heterogeneous esterification has proceeded very efficiently to yield the succinylated-olive stone (S–OS). Subsequent alkaline treatment of S–OS with saturated NaHCO₃ aqueous solution led to the resulting sodic material (NaS–OS), which was subjected to batch experiments in order to evaluate its cadmium-removing efficiency from aqueous solutions at realistic concentrations of cadmium found in industrial effluents. The results obtained from the sorption characteristics have revealed that NaS–OS material is highly effective in removing cadmium from aqueous solutions, with a maximum uptake capacity of 200 mg g⁻¹ (1.78 mmol g⁻¹). The Langmuir isotherm model was found to fit adequately the equilibrium isotherm data. Cadmium adsorption occurs rapidly and the adsorption mechanism is a chemical sorption via ionic exchange between the adsorbate and adsorbent. Thermodynamic parameters were also evaluated from the effect of temperature studies. Regenerability of NaS–OS material was ascertained by quantitative desorption of cadmium with 1 M aqueous NaCl and the reusability of the matrix after five repeated cycles led to nearly no attenuation in its performance (less than 2% in the sorption capacity), indicating that repeated use of NaS–OS is quite feasible. Compared to other low-cost adsorbents utilized for the removal of Cd(II) from water/wastewater, NaS–OS shows higher sorption capacity. These results have important implications for the design of low-cost adsorbents based on agricultural wastes.     

Thiol‐acrylate main‐chain liquid‐crystalline elastomers with tunable thermomechanical properties and actuation strain

The purpose of this study was to investigate the influence of cross‐linking on the thermomechanical behavior of liquid‐crystalline elastomers (LCEs). Main‐chain LCE networks were synthesized via a thiol‐acrylate Michael addition reaction. The robust nature of this reaction allowed for tailoring of the behavior of the LCEs by varying the concentration and functionality of the cross‐linker. The isotropic rubbery modulus, glass transition temperature, and strain‐to‐failure showed strong dependence on cross‐linker concentration and ranged from 0.9 MPa, 3 °C, and 105% to 3.2 MPa, 25 °C, and 853%, respectively. The isotropic transition temperature (T_i) was shown to be influenced by the functionality of the cross‐linker, ranging from 70 °C to 80 °C for tri‐ and tetra‐functional cross‐linkers. The magnitude of actuation can be tailored by controlling the amount of cross‐linker and applied stress. Actuation increased with increased applied stress and decreased with greater amounts of cross‐linking. The maximum strain actuation achieved was 296% under 100 kPa of bias stress, which resulted in work capacity of 296 kJ/m³ for the lowest cross‐linked networks. Overall, the experimental results provide a fundamental insight linking thermomechanical properties and actuation to a homogenous polydomain nematic LCE networks with order parameters of 0.80 when stretched. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 157–168     

Singularities of the solution of a mixed problem for a general second order elliptic equation and boundary stabilizationof the wave equation

We deal here with a second order elliptic mixed problem which is posed in a regular open bounded domain of . We study the regularity of its solution. We apply our results to the boundary stabilization of the wave equation.     

Bis(diphosphaferrocene) palladium(II) dimer complexes as efficient catalysts in the synthesis of arylboronic esters

Bis(diphosphaferrocenes)PdCl₂ dimers efficiently catalyse cross-coupling reactions between aryl iodides and pinacol borane in dioxane at 80 °C to afford the corresponding aryl boronic esters derivatives in excellent yields.     

Kinematic shakedown by the Norton–Hoff–Friaa regularising method and augmented LagrangianAdaptation cinématique par la methode de régularisation de Norton–Hoff–Friaa et du Lagrangien augmenté

The shakedown analysis of elastic perfectly plastic structures is formulated as a discrete nonlinear mathematical programming problem by means of the finite element technique. The kinematical problem is regularized through the introduction of the Norton–Hoff viscoplastic material to overcome the non-differentiability of the objective function, and can be solved numerically by the augmented Lagrangian technique. To cite this article: M.A. Hamadouche, C. R. Mecanique 330 (2002) 305–311.     

Sulfonyl Fluoride‐Based Prosthetic Compounds as Potential 18F Labelling Agents

Nucleophilic incorporation of [¹⁸F]F^? under aqueous conditions holds several advantages in radiopharmaceutical development, especially with the advent of complex biological pharmacophores. Sulfonyl fluorides can be prepared in water at room temperature, yet they have not been assayed as a potential means to ¹⁸F‐labelled biomarkers for PET chemistry. We developed a general route to prepare bifunctional 4‐formyl‐, 3‐formyl‐, 4‐maleimido‐ and 4‐oxylalkynl‐arylsulfonyl [¹⁸F]fluorides from their sulfonyl chloride analogues in 1:1 mixtures of acetonitrile, THF, or tBuOH and Cs[¹⁸F]F/Cs₂CO_3(aq.) in a reaction time of 15 min at room temperature. With the exception of 4‐N‐maleimide‐benzenesulfonyl fluoride ( 3 ), pyridine could be used to simplify radiotracer purification by selectively degrading the precursor without significantly affecting observed yields. The addition of pyridine at the start of [¹⁸F]fluorination (1:1:0.8 tBuOH/Cs₂CO_3(aq.)/pyridine) did not negatively affect yields of 3‐formyl‐2,4,6‐trimethylbenzenesulfonyl [¹⁸F]fluoride ( 2 ) and dramatically improved the yields of 4‐(prop‐2‐ynyloxy)benzenesulfonyl [¹⁸F]fluoride ( 4 ). The N‐arylsulfonyl‐4‐dimethylaminopyridinium derivative of 4 ( 14 ) can be prepared and incorporates ¹⁸F efficiently in solutions of 100 % aqueous Cs₂CO₃ (10 mg mL^?1). As proof‐of‐principle, [¹⁸F] 2 was synthesised in a preparative fashion [88(±8) % decay corrected (n=6) from start‐of‐synthesis] and used to radioactively label an oxyamino‐modified bombesin(6–14) analogue [35(±6) % decay corrected (n=4) from start‐of‐synthesis]. Total preparation time was 105–109 min from start‐of‐synthesis. Although the ¹⁸F‐peptide exhibited evidence of proteolytic defluorination and modification, our study is the first step in developing an aqueous, room temperature ¹⁸F labelling strategy.