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.

Four Bi-Sb alloys with compositions Bi79.6Sb20.4, Bi56.9Sb43.1, Bi39.8Sb60.2, Bi18.6Sb81.4 have been investigated regarding the microstructures and thermal properties. The microstructure was examined by scanning electron microscopy with energy-dispersive X-ray spectrometry. The light flash method was applied to determine thermal diffusivity and to obtain thermal conductivity in the temperature range 25 to 150??, while the indirect Archimedean method was used for determination of densities of the investigated Bi-Sb alloys. The obtained results have shown that the density of the studied alloys decreased monotonically with increasing the antimony content. On the other hand, the specific heat capacity of Bi-Sb alloys increased with the increase in the antimony content as well as with increasing the temperature. Thermal diffusivity of the alloys increased slightly with increasing the temperature. Thermal conductivities of the examined Bi-Sb alloys were determined to be in the range of 3.8 to 7 W m-1 K-1, which is lower than thermal conductivities of pure bismuth and antimony. The results obtained in this work represent a contribution to better knowledge of the thermal properties of Bi-Sb alloys, which are of key importance for determining the possibility of their practical application.

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.