Mechanistic aspects of Au(III) sorption by Aspergillus terreus SRD49

Recovery of gold from electronic wastewater by Phomopsis sp. XP-8 and its potential application in the degradation of toxic dyes

Environmentally friendly, efficient, and economical methods of gold recovery are significant challenges for high-tech industries and environmental protection. In this study, Phomopsis sp. XP-8, a filamentous endophytic fungus, demonstrated great potential for selectively recovering gold from electronic wastewater without any pretreatment and was shown to be convenient and safe in practical application. Under optimum conditions, the gold recovery rate was more than 80% at a dilute concentration of Au³⁺. Model-fitting analysis indicated the adsorption of Au³⁺ was well described by the pseudo-second-order kinetic model and the Langmuir isotherm model. The maximum Au³⁺ adsorption was from 208 to 280 mg/g within the temperature range of 20-50 °C. The data from electronic wastewater revealed its great potential for selective recovery of gold from complex aqueous solutions. Additionally, the formed nanogold-bioconjugates exhibited efficient degradation of toxic dyes in wastewater, which demonstrated the potential application of these byproducts produced via the biosorption process.

Fabrication of Triethylenetetramine Terminal Hyperbranched Dendrimer-Like Polymer Modified Silica Gel and Its Prominent Recovery Toward Au (III)

To further increase the quantity and density of functional groups on adsorbent, terminal triethylenetetramine hyperbranched dendrimer-like polymer modified silica-gel (SG-TETA and SG-TETA2) was synthesized. The hyperbranched dendrimer-like polymer was successfully introduced onto silica gel and new cavities were formed, which was demonstrated by FTIR, SEM, and BET. The highest adsorption capacities of SG-TETA and SG-TETA2 obtained from Langmuir model toward Au(III) were 2.11, and 2.27 mmol g⁻¹, respectively, indicating that SG-TETA2 possessing more functional groups had a better adsorption ability. Moreover, the adsorbents combined with Au(III) ion through chelation and electrostatic attraction mechanism, after which reduction reactions for Au(III) ion loaded on adsorbents proceeded. SG-TETA2 had better adsorption selectivity than SG-TETA in removing Au(III) in Au-existed ion solution systems. SG-TETA2 had higher overall adsorption capacities compared to silica-gel-based hyperbranched polymers functionalized by diethylenetriamine. Therefore, the effective recovery makes SG-TETA2 a practical adsorbent in removing Au(III) ion from e-wastes and industrial effluents with much prospect.