Chromium recovery from chrome shaving generated in tanning process

Area of Science:

• Environmental Science
• Materials Science
• Chemical Engineering

Background:

• Chrome shaving is a chromium-rich solid waste from the leather tanning industry.
• Efficient recovery of chromium from this waste is crucial for resource sustainability and pollution reduction.

Purpose of the Study:

• To investigate chromium recovery from chrome shaving as soluble chromate.
• To prepare a basic Cr(III) sulfate solution for tanning from the recovered chromate.
• To identify the most effective oxidation agent and conditions for chromate formation.

Main Methods:

• Oxidation of chrome shaving using air, oxygen, and sodium peroxide (Na2O2).
• Investigation of oxidation yield at 850°C for air and oxygen.
• Determination of optimal Na2O2 concentration for maximum chromium recovery.
• Leaching of generated chromate with distilled water to form a pregnant chromate solution.
• Reduction of chromate ions using sodium sulfite (Na2SO3) to obtain Cr(III) sulfate solution.

Main Results:

• Oxidation agent is the most critical parameter for chromate formation.
• Maximum oxidation yields were 23.02% (air) and 30.41% (oxygen) at 850°C.
• The highest chromium recovery efficiency (99.45%) was achieved using eight times the stoichiometric amount of Na2O2.
• A pregnant chromate solution was prepared, and subsequent reduction yielded a Cr(III) sulfate solution.

Conclusions:

• Sodium peroxide (Na2O2) is a highly effective agent for chromium recovery from chrome shaving.
• The developed process enables efficient recovery of chromium and preparation of Cr(III) sulfate solution for tanning applications.
• This method offers a sustainable approach to managing chromium-containing solid waste.