Simple gold extraction

Simple gold extraction - gold extraction with aqua regia:

1. Aqua regia preparation cost: hydrochloric acid + nitric acid

• Function: dissolve gold (reaction formula: Au + HNO₃ + 4HCl → HAuCl₄ + NO↑ + 2H₂O).
• Ratio: usually hydrochloric acid: nitric acid = 3:1 (volume ratio)

                       Nitric acid (HNO₃): about 0.4 grams (need to consider the actual reaction efficiency,

          usually an excess).

                       Hydrochloric acid (HCl): about 1.6 grams (mixed with nitric acid at a volume ratio of 3:1)

      Gold dissolves at a rate of about 1.5 grams per 1.5 ml of aqua regia per hour at room temperature.

2. Reducing agent: sodium sulfite (Na₂SO₃)

• Function: reduce dissolved gold ions (Au³⁺) to elemental gold. 2HAuCl₄ + 3Na₂SO₃ → 2Au↓ + 3Na₂SO₄ + 8HCl
• Dosage: about 1.5 g/g gold (calculated according to the reaction formula)

          This method is flexible and adaptable, but requires strict control of the reagent ratio (excessive

nitric acid affects the dissolution efficiency) and reaction conditions (temperature, time); its cost is

significantly affected by the gold content of the raw materials, and the reagent consumption may

increase by dozens of times when processing low-grade raw materials, and the environmental risks

are prominent - the waste liquid contains strong acids, heavy metals and toxic gases (such as NOx),

which require professional neutralization, precipitation and recycling. It is recommended to give

priority to large-scale production or combine more environmentally friendly processes such as

cyanidation and electrolysis to balance efficiency and sustainability.vido