PRECIOUS METALS RECOVERY

The recovery of precious metals from manufacturing waste or chemical processes represents an extremely important activity in the economy in the economy of business activities.

The metals dissolved in solutions are often present in different forms and concentrations depending on the type of process from which they derive, and their recovery can take place with different techniques and methods.

Balestri Technologies has developed different types of machinery:

ELECTROWINNING: ELECTROLYTIC UNITS

Electrowinning is a recovery technique that takes place inside an electrolytic cell: the metal dissolved in solution is extracted thanks to the passage of current, making it deposit on a special support called cathode.

The BT-EW-02 electrowinning unit is a modular equipment, made up of a series of anodic and cathodic plates and equipped with a pump for recirculating the solution to be treated and a current rectifier.

The number of cathodes and anodes can vary depending on the volume of the solution/concentration of metals, according to the following configurations:

• BT-EW-02-TICU1: 2 anodes and 1 cathode - basic configuration to treat 200 to 400 liters of solutions per recovery cycle*
• BT-EW-02-TICU2: 3 anodes and 2 cathodes - configuration to treat 600 to 800 liters of solutions per recovery cycle*
• BT-EW-02-TICU3: 4 anodes and 3 cathodes - configuration to treat from 1000 to 1200 liters of solutions per recovery cycle*
• BT-EW-02-TICU5: 6 anodes and 5 cathodes - configuration to treat more than 1500 liters of solutions per recovery cycle*

* the recovery cycle varies from 48 to 72 hours

The material of the anodic and cathodic plates can vary based according to the type of liquid to be treated (pH of the solution), the metal to be recovered and its concentration.

Cathodic plates are consumable elements: once the deposit surface is saturated, the cathode must be replaced with a new element.

The user may decide to replace the cathodes at each recovery cycle or use them for multiple cycles until their depositing surface is exhausted.

The metal deposited on the cathode is then sent to the next treatment cycle: smelting and refining.

The recovery efficiency of the BT-EW-02 electrowinning units is greater than 99%.

The machinery finds applications in various sectors: goldsmith/silversmith, galvanic, mining.

Specifically, the applications successfully tested are:

• recovery of Au and Ag from cyanide-based solutions from jewelry surface finishing processes
• Au and Ag recovery from galvanic solutions
• Au recovery from electroforming solutions
• Au recovery from cyanide-based solutions in mining processes
• Cu recovery from sulfuric solutions
• Ag recovery from acidic solutions

Contact our technical department to evaluate the solution suited to your needs.

IONS EXCHANGE RESINS UNITS

The recovery of metals using ion exchange resins is a technique used to retain precious metals, with a special focus on platinum and palladium, which can be found in the residual waters of aqua regia refining processes.

The BT-IONEX ion exchange resin systems are made up of vertical columns, made of glass or polypropylene, filled with special selective resins that capture precious metals (gold, silver, platinum, palladium and rhodium). The solution to be treated is passed slowly through the resin, for the time necessary for the absorption of the metals.

The efficiency / selectivity of the process is appreciable based on the type of resin used, among the various available on the market.

The recovery of the precious material occurs when the resins are exhausted, through the incineration of the resins.

Contact our technical department to evaluate the solution suited to your needs.

CEMENTATION UNITS

Recovery by means of the cementation technique is based on the different standard reduction potential of metals: the introduction into a solution of an appropriate metal with a lower potential oxidizes the latter, reducing the metal to be recovered.

This technique is particularly suitable for the recovery of copper from exhausted precious metal refining solutions, with the following advantages:

• reduction of the presence of copper as a heavy metal from waste water, to the benefit of the environmental sustainability of the activity;
• the precious metals, if present, precipitate together with the copper, allowing for the subsequent possibility of recovery, to the benefit of the efficiency of the process;
• the recovered copper can be sent to following steps of refining

The BT-CEM Cementation Unit consist of a process tank with an adequate stirring and discharge system on the bottom. The recovered material is collected in a special filter unit.

Contact our technical department to evaluate the solution suited to your needs.