Separation and pre-concentration of palladium(II) from environmental and industrial samples by formation of a derivative of 1,2,4-triazole complex on Amberlite XAD–2010 resin

A simple separation/pre-concentration method was developed for extraction of Pd(II) in various environmental samples, based on its adsorption of 4–phenyl–5–{[(4–phenyl–5–pyridin–4–yl–4H–1,2,4–triazole–3–yl)thio]methyl}–4H–1,2,4–triazole–3–thyol (PPTTMET) complex on Amberlite XAD–2010 resin in a mini column. The ligand has high affinity for Pd(II) among many other metals that are taken into consideration. The flame atomic absorption spectrometry is employed to determine the concentration of Pd(II). The optimum working conditions which were determined are as follows: 0.05?mol?L^?1 HNO₃ as working medium, 1.0?mol?L^?1 HCI in acetone as elution solvent, 0.75?mg of PPTTMET amount and 750?mL of sample volume. The system was independent from the flow rates between 3.1 and 23.1?mL?min^?1. The Pd(II) adsorption capacity of Amberlite XAD–2010 resin was found to be 12.8?mg?g^?1 and the enrichment factor was calculated as 375. The method was successfully applied for the determination of Pd(II) in motorway dust samples, anodic sludge, gold ore, industrial electronic waste materials and various water samples.     

Synthesis of cyclopropane-annulated conduritol derivatives: norcaran-2,3,4,5-tetraoles

Norcaran-2,3,4,5-tetraoles were synthesized starting from methyl 1,3,5-cycloheptatriene-7-carboxylate in several steps. Norcaradiene endoperoxide is the key component; it was obtained by photooxygenation of methyl 1,3,5-cycloheptatriene-7-carboxylate. The other oxygen functionalities are introduced through epoxide ring opening and OsO₄-hydroxylation reactions.     

Multi-period reverse logistics network design

The configuration of the reverse logistics network is a complex problem comprising the determination of the optimal sites and capacities of collection centers, inspection centers, remanufacturing facilities, and/or recycling plants. In this paper, we propose a profit maximization modeling framework for reverse logistics network design problems. We present a mixed-integer linear programming formulation that is flexible to incorporate most of the reverse network structures plausible in practice. In order to consider the possibility of making future adjustments in the network configuration to allow gradual changes in the network structure and in the capacities of the facilities, we consider a multi-period setting. We propose a multi-commodity formulation and use a reverse bill of materials in order to capture component commonality among different products and to have the flexibility to incorporate all plausible means in tackling product returns. The proposed general framework is justified by a case study in the context of reverse logistics network design for washing machines and tumble dryers in Germany. We conduct extensive parametric and scenario analysis to illustrate the potential benefits of using a dynamic model as opposed to its static counterpart, and also to derive a number of managerial insights.