Gold is one of the precious metals with multiple uses, whose deposits are much smaller than the global production needs. Therefore, extracting maximum gold quantities from industrial diluted solutions is a must. Am-L-GA is a new material, obtained by an Amberlite XAD7-type commercial resin, functionalized through saturation with L-glutamic acid, whose adsorption capacity has been proved to be higher than those of other materials utilized for gold adsorption. In this context, this article presents the results of a factorial design experiment for optimizing the gold recovery from residual solutions resulting from the electronics industry using Am-L-GA. Firstly, the material was characterized using atomic force microscopy (AFM), to emphasize the material’s characteristics, essential for the adsorption quality. Then, the study showed that among the parameters taken into account in the analysis (pH, temperature, initial gold concentration, and contact time), the initial gold concentration in the solution plays a determinant role in the removal process and the contact time has a slightly positive effect, whereas the pH and temperature do not influence the adsorption capacity. The maximum adsorption capacity of 29.27 mg/L was obtained by optimizing the adsorption process, with the control factors having the following values: contact time ~106 min, initial Au(III) concentration of ~164 mg/L, pH = 4, and temperature of 25 °C. It is highlighted that the factorial design method is an excellent instrument to determine the effects of different factors influencing the adsorption process. The method can be applied for any adsorption process if it is necessary to reduce the number of experiments, to diminish the resources or time consumption, or for expanding the investigation domain above the experimental limits.

2,2′-thiobisethanol dimethacrylate/ethylene glycol dimethacrylate copolymer (coP-TEDMA/EGDMA) was used as a sorbent for gold recovery from residual solutions resulting from the electroplating industry. Firstly, synthesized material was characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and confocal laser scanning microscopy. The sorption process mechanism was evidenced on the basis of kinetic, thermodynamic and equilibrium studies. To highlight this, the influence of solution pH, temperature and gold initial concentration on maximum sorption capacity was studied. The obtained experimental data were modeled using Langmuir, Freundlich and Sips sorption isotherms, and it was observed that the Sips one was better for describing the studied sorption process. Kinetic data were fitted using pseudo-first-order and pseudo-second-order kinetic models. Of these models, the studied process was better described by the pseudo-second-order model. The thermodynamic parameters free Gibbs energy (ΔG0), enthalpy (ΔH0), and entropy (ΔS0) were evaluated on the basis of the van’t Hoff equation. On the basis of the thermodynamic study, it was concluded that gold recovery on coP-TEDMA/EGDMA is a spontaneous and endothermic process.

The aim of this study was to develop new materials with adsorbent properties that can be used for the adsorption recovery of Au(III) from aqueous solutions. To achieve this result, it is necessary to obtain inexpensive adsorbent materials in a granular form. Concomitantly, these materials must have a high adsorption capacity and selectivity. Other desired properties of these materials include a higher physical resistance, insolubility in water, and materials that can be regenerated or reused. Among the methods applied for the separation, purification, and preconcentration of platinum-group metal ions, adsorption is recognised as one of the most promising methods because of its simplicity, high efficiency, and wide availability. The studies were carried out using three supports: cellulose (CE), chitosan (Chi), and diatomea earth (Diat). These supports were functionalised by impregnation with extractants, using the ultrasound method. The extractants are environmentally friendly and relatively cheap amino acids, which contain in their structure pendant groups with nitrogen and sulphur heteroatoms (aspartic acid—Asp, l-glutamic acid—Glu, valine—Val, DL-cysteine—Cys, or serine—Ser). After preliminary testing from 75 synthesised materials, CE-Cys was chosen for the further recovery of Au(III) ions from aqueous solutions. To highlight the morphology and the functionalisation of the material, we physicochemically characterised the obtained material. Therefore, the analysis of the specific surface and porosity showed that the CE-Cys material has a specific surface of 4.6 m²/g, with a porosity of about 3 nm. The FT-IR analysis showed the presence, at a wavelength of 3340 cm⁻¹, of the specific NH bond vibration for cysteine. At the same time, pHpZc was determined to be 2.8. The kinetic, thermodynamic, and equilibrium studies showed that the pseudo-second-order kinetic model best describes the adsorption process of Au(III) ions on the CE-Cys material. A maximum adsorption capacity of 12.18 mg per gram of the adsorbent material was achieved. It was established that the CE-Cys material can be reused five times with a good recovery degree.

The 1st and the 2nd laws of thermodynamics are among the principles with the most serious approaches in science, especially due to the overwhelming implications they have, both in the elaboration and development of theoretical concepts in the most diverse fields, as well as in the technical applications that have revolutionized industrial production. One of the questions related to these laws is whether or not they can be applied to the scale of the entire universe. The implications resulting from this approach are very diverse as they underpin concepts such as the continuous accelerated expansion of the universe, the thermal death of the universe, the entropy of the universe and the evolution of the universe as a cyclical process, energy as a property of the space-time relationship, dark energy and matter, black holes, white holes etc. This paper is an attempt to provide some answers to the challenge of discussing the applicability or inapplicability of the First and Second Laws of Thermodynamics on the scale of the entire universe, with arguments for and against, generated by well-defined or only incipient theoretical developments that treat cosmogony and cosmology through the prism of thermodynamics.

This study evaluates the impact of long-term mining activities on stream surface waters in the Danube Basin in eastern Serbia. Seasonal variations in water chemistry were investigated during three hydrological periods to assess current contamination levels and temporal changes following recent environmental protection measures. The highest element concentrations were recorded during the autumn low-flow period. In contrast, the lowest concentrations occurred during the snowmelt season, indicating a strong influence of seasonal hydrological conditions on contaminant distribution. In streams located downstream of mining facilities, element concentrations were additionally controlled by anthropogenic inputs associated with mining activities. Elevated concentrations of SO₄²⁻ (1054 mg/L), Cu (393 µg/L), and Mn (2064 µg/L) were detected compared with background values characteristic of non-contaminated streams (e.g., SO₄²⁻~100 mg/L, Cu~20 µg/L, and Mn~20 µg/L). Recent environmental protection measures, including the neutralization of mining wastewater before discharge into rivers, have substantially reduced contamination levels. Compared with historical periods when untreated wastewater was directly discharged into river systems, concentrations of Fe, As, Cu, and Mn decreased by approximately 2650-, 900-, 740-, and 6-fold, respectively. In contrast, sulfate concentrations remained relatively unchanged, indicating persistent mining-related pollution and suggesting sulfate as a reliable indicator of contamination in similar mining environments. Overall, the results demonstrate partial recovery of the aquatic system and improved water quality over time; however, elevated concentrations of SO₄²⁻, Mn, and Cu indicate ongoing environmental impacts of mining activities and highlight the need for long-term environmental monitoring and management.