Gold recovery from secondary waste of PCBs by electro-Cl2 leaching in brine solution and solvo-chemical separation with tri-butyl phosphate

Deicing of pavements is essential to ensure safe and timely movement of traffic in geographical locations where snow and ice events are anticipated. State and local municipalities employ brine solution with 23.3 wt% sodium chloride (NaCl) available in the form of rock salt to deice the pavements. Unlike water, the brine solution does not freeze until the temperature falls below −21.0 °C, i.e., the freezing point of water is depressed by −21.0 °C with the addition of 23.3 wt% NaCl. The depressed freezing point of the brine solution plays a key role in deicing pavements. Unfortunately, a further increase in rock salt content does not lower the freezing point of the brine solution. In this study, different combinations of agricultural products such as polyols including sorbitol, maltitol, and mannitol in brine (23.3 wt% of NaCl in water), and NaCl-juice (corn and beet juice) were investigated to achieve freezing point depressions below −21.0 °C for potential deicing applications in extremely cold areas. Different weight fractions of polyols-brine solutions ranging from 7.14% to 27.77% were considered, and corresponding freezing points were determined. While the sorbitol-brine solution exhibited the lowest freezing point of −38.1 °C at a higher concentration, the maltitol-brine solution exhibited a freezing point of −35.6 °C at the same concentration. Based on the °Brix value, beet juice had almost three times more soluble solids and a lower freezing point compared to corn juice. Adding 23.3 wt% of NaCl in 70% corn juice lowered the freezing point up to −23.5 °C.

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Full Factorial Design for Gold Recovery from Industrial Solutions

Toxics ◽

10.3390/toxics9050111 ◽

2021 ◽

Vol 9 (5) ◽

pp. 111

Author(s):

Maria Mihăilescu ◽

Adina Negrea ◽

Mihaela Ciopec ◽

Petru Negrea ◽

Narcis Duțeanu ◽

...

Keyword(s):

Factorial Design ◽

Adsorption Capacity ◽

Contact Time ◽

Adsorption Process ◽

Design Method ◽

Precious Metals ◽

Gold Recovery ◽

Maximum Adsorption Capacity ◽

Gold Concentration ◽

Commercial Resin

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.

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Implications of breakpoint chlorination on chloramines decay and disinfection by-products formation in brine solution

Desalination ◽

10.1016/j.desal.2021.114961 ◽

2021 ◽

Vol 504 ◽

pp. 114961

Author(s):

Parmila Devi ◽

Ajay K. Dalai

Keyword(s):

Brine Solution ◽

By Products

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Performance-Based Selection of the Cathode Material for the Electrodeposition-Redox Replacement Process of Gold Recovery from Chloride Solutions

Metallurgical and Materials Transactions B ◽

10.1007/s11663-021-02239-x ◽

2021 ◽

Author(s):

Ivan Korolev ◽

Kirsi Yliniemi ◽

Mari Lindgren ◽

Leena Carpén ◽

Mari Lundström

Keyword(s):

Material Selection ◽

Recovery Process ◽

Multiple Attribute Decision Making ◽

Gold Recovery ◽

Process Efficiency ◽

Gold Extraction ◽

Corrosion Properties ◽

Multiple Attribute ◽

Replacement Process ◽

Cathode Substrate

AbstractRecently, an emerging electrodeposition-redox replacement (EDRR) method was demonstrated to provide exceptionally efficient gold recovery from cyanide-free hydrometallurgical solutions. However, the effect of electrode material and its corrosion resistance in this process was overlooked, even though the EDRR process is carried out in extremely corrosive, acidic chloride solution that also contains significant amounts of strong oxidants, i.e., cupric ions. In the current study, nickel alloy C-2000, stainless steels 316L and 654SMO, and grade 2 titanium were for the first time critically evaluated as potential cathode materials for EDRR. The particular emphasis was placed on better understanding of the effect of cathode substrate on the overall efficiency of the gold recovery process. The use of a multiple attribute decision-making method of material selection allowed reaching of a well-founded compromise between the corrosion properties of the electrodes and process efficiency of gold extraction. The 654SMO steel demonstrated outstanding performance among the examined materials, as it enabled gold recovery of 28.1 pct after 3000 EDRR cycles, while its corrosion rate (CR) was only 0.02 mm/year.

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