Efficient precious metal Rh(III) adsorption by waste P. pastoris and P. pastoris surface display from high-density...

Rhodium is one of the most used precious metals in catalysis both in laboratory reactions and industrial processes. However, the adsorption of Rh(III) by microorganisms has been seldomly reported. In this work, waste P. pastoris and recombinant P. pastoris with surface-displayed Rh metal peptides (P. pastoris GS-R) from high-density culture were used as novel adsorbents to study Rh(III) adsorption. Under the optimal adsorption conditions of biomass of 0.25 g L^-1, pH of 1.2, temperature of 30 °C, and adsorption time of 2 h in simulated wastewater, the maximum adsorption ratios of 55.69% (110.1 mg g^-1) and 75.03% (142.11 mg g^-1) were achieved for waste P. pastoris and P. pastoris GS-R, respectively. Using the two adsorbents, the adsorption kinetic models fit the quasi-second-order equation, and isotherm models followed the Langmuir and Temkin equations, respectively. P. pastoris GS-R showed high adsorption capacity (48.49%) and selectivity (65.86%) in electroplating wastewater, and the desorption ratio reached 34.49% after treatment with 2 M HNO₃ and ultrasonic wave. Therefore, an environmental-friendly strategy was developed for the recovery of Rh(III) and other precious metals by using P. pastoris.