The study on the biosorption of copper ions using raw eggshells as an adsorbent is presented in this paper. The influence of different process parameters, such as: initial pH value of the solution, initial Cu²⁺ ions concentration, initial mass of the adsorbent, and stirring rate, on the biosorption capacity was evaluated. The SEM-EDS analysis was performed before and after the biosorption process. SEM micrographs indicate a change in the morphology of the sample after the biosorption process. The obtained EDS spectra indicated that K, Ca, and Mg were possibly exchanged with Cu²⁺ ions during the biosorption process. The equilibrium analysis showed that the Langmuir isotherm model best describes the experimental data. Four kinetic models were used to analyze the experimental data, and the results revealed that the pseudo-first order kinetic model is the best fit for the analyzed data. Calculated thermodynamic data indicated that the biosorption process is spontaneous, and that copper ions are possibly bound to the surface of the eggshells by chemisorption. The biosorption process was optimized using Response Surface Methodology (RSM) based on the Box-Behnken Design (BBD), with the selected factors: adsorbent mass, initial metal ion concentration, and contact time.

Lead-free solders have become a main focus of the electronic industry in recent years, because of the high toxicity of lead. Alloys based on the Sn-Bi system figure as potential replacements for Sn-Pb alloys in soldering due to favorable properties and low cost. One of the main advantages of these alloys are low melting temperatures, while additional advantages include good compatibility with substrates, low process temperature, high reliability, and potential applications in conjunction with reduced graphene oxide nanosheets as thermal interface materials. In this paper, characterization of microstructural and thermal properties as well as hardness measurements of seven alloys of different Sn-Bi compositions are performed. Structural properties of the samples were analyzed using optical microscopy and scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS). Thermal conductivity of the samples was investigated using the xenon-flash method, and phase transition temperatures were measured using the differential scanning calorimetry (DSC) analysis.

The roasting of sulfide ores and concentrates is one of the most important steps in pyrometallurgical metal production from primary raw materials, due to the necessity of excess sulfur removal, present in the virgin material. Pentlandite is one of the main sources for nickel pyrometallurgical production. The knowledge of its reaction mechanism, products distribution during oxidation and reaction kinetics is important for optimizing the production process. Raw pentlandite-bearing ore from the Levack mine (Ontario, Canada) was subjected to oxidative roasting in the air atmosphere. A chemical analysis of the initial sample was conducted according to EDXRF (Energy-Dispersive X-ray Fluorescence) and AAS (Atomic Adsorption Spectrometry) results. The characterization of the initial sample and oxidation products was conducted by an XRD (X-ray Diffraction) and SEM/EDS (Scanning Electron Microscopy with Energy Dispersive Spectrometry) analysis. Thermodynamic calculations, a phase analysis and construction of Kellogg diagrams for Ni-S-O and Fe-S-O systems at 298 K, 773 K, 923 K and 1073 K were used for proposing the theoretical reaction mechanism. A thermal analysis (TG/DTA—Thermogravimetric and Differential Thermal Analyses) was conducted in temperature range 298–1273 K, under a heating rate of 15° min⁻¹. A kinetic analysis was conducted according to the non-isothermal method of Daniels and Borchardt, under a heating rate of 15° min⁻¹. Calculated activation energies of 113 kJ mol⁻¹, 146 kJ mol⁻¹ and 356 kJ mol⁻¹ for three oxidation stages imply that in every examined stage of the oxidation process, temperature is a dominant factor determining the reaction rate.

The influence of the ageing temperature on the hardness, electrical conductivity, thermal diffusivity and thermal conductivity of the EN AW-7075 aluminium alloy was studied in this paper. After solution treating the alloy at 480 °C for 1 h and quenching it in ice water, the investigated alloy was characterized using Differential Thermal Analysis (DTA) in order to determine the optimal temperatures for the isochronal ageing treatments. Afterwards, isochronal ageing was conducted at the temperature range of 110 °C-250 °C for 30 min The hardness, electrical conductivity, thermal diffusivity, thermal conductivity and microstructural features were investigated during the ageing treatments. Hardness had a peak value after ageing at 150 °C, while other properties gradually increased with the ageing temperature. Microstructural investigation of the aged alloy by SEM-EDS revealed the existence of precipitated phases that appear homogenously distributed in the microstructure.

The removal of copper ions from aqueous solutions using bean shells as an adsorbent is presented in this paper. The influence of the solution pH on the biosorption capacity was investigated. The biosorption capacity increased with the increase in the solution pH. The pseudo-second order kinetic model showed the best agreement with the analysed experimental data, indicating that chemisorption could be a possible way of binding the copper ions to the surface of the bean shells. The Langmuir isotherm model best fitted the analysed isotherm data. The SEM-EDS analysis was performed before and after the biosorption process. The change in the morphology of the sample after the biosorption process was evident, whereby K, Mg, Si and Ca were possibly exchanged with copper ions. Response surface methodology (RSM) based on the Box?Behnken design (BBD) was used to optimize the biosorption process, with the selected factors: the solution pH, initial copper ions concentration and contact time. The optimum biosorption conditions were determined to be: pH 3?4, initial copper ions concentration, 100 mg dm-3, and contact time, 10?30 min.