Abstract
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.
Highlights
Precious metals from the platinum group (PMs) have various applications in different fields due to their physical and chemical properties, such as catalytic activity, good electrical conductivity, corrosion resistance, etc. [1,2]
The synthesized material was analyzed by X-ray energy dispersion (EDX) using a Quantum FEG 250 scanning electron microscope, and Fourier Transformed Infrared spectroscopy (FTIR) using a Bruker FT-IR spectrometer Platinum ATR-QL Diamond, in the range 4000–400 cm−1
The adsorbent material obtained after Amberlite XAD7 functionalization was dried for 24 h; afterward, several granules of modified adsorbent were glued on the carbon adhesive disks and fixed on the stabs
Summary
Precious metals from the platinum group (PMs) have various applications in different fields due to their physical and chemical properties, such as catalytic activity, good electrical conductivity, corrosion resistance, etc. [1,2]. Precious metals from the platinum group (PMs) have various applications in different fields due to their physical and chemical properties, such as catalytic activity, good electrical conductivity, corrosion resistance, etc. Gold is utilized in the technique of thin starts, printed circuit boards manufacturing, for high-frequency conductors, shielding and surface protection, contact mechanism (contact with plugs), and for connecting surfaces in cable structures of electronic assemblies [5]. Rarity, exceptional properties, and diverse utilizations (due to the resistance to corrosion, good electrical conductivity, and high catalytic activity) increased the demand for gold, making its recovery very important [6]. For some metals, scientists estimated [7,8] that nowadays extracting the same amount as a century ago necessitates the removal of about three times more rocks. Recycling is beneficial from economic and environmental perspectives. Recycling is a valuable source to recover scarce materials [7,9,10,11]
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