Precious metal recovery by selective adsorption using biosorbents

Area of Science:

• Materials Science
• Environmental Chemistry
• Biotechnology

Background:

• Low-cost biosorbents are crucial for efficient metal recovery from waste streams.
• Silk sericin and chitosan are abundant biopolymers with potential for heavy metal adsorption.

Purpose of the Study:

• To evaluate and compare the efficiency and selectivity of silk sericin and chitosan for gold adsorption.
• To investigate the adsorption mechanisms and potential for gold recovery from complex solutions.

Main Methods:

• Biosorption experiments using silk sericin and chitosan as adsorbents for gold.
• Analysis of adsorption capacity, selectivity, and binding sites using techniques like K(d) value determination.
• Testing separation efficiency in binary, five-component, and six-component metal solutions.

Main Results:

• Both biosorbents showed high gold adsorption capacity, with chitosan adsorbing 3.3 mmol/g and silk sericin 1 mmol/g.
• Silk sericin exhibited superior selectivity for gold (Sel(Au)>2.4) compared to chitosan.
• Gold was recovered at 99.5% purity using silk sericin, and 90% purity in the presence of palladium.

Conclusions:

• Silk sericin and chitosan are effective, low-cost biosorbents for gold recovery.
• Silk sericin offers higher selectivity and purity for gold recovery, especially from complex mixtures.
• The study highlights the potential of waste-derived biomaterials for sustainable precious metal recycling.