Biosorption of copper(II) from aqueous solutions using volcanic rock matrix-immobilized Pseudomonas putida cells with surface-displayed cyanobacterial metallothioneins

Biosorption using biomasses has been confirmed by certain studies to be an effective and economical method in removing heavy metals from wastewaters. However, the usually insufficient physical strength and regenerability of these biomaterials have restricted their use in continuous or large-scale processes. The present study investigates the ability of volcanic rock matrix (VRM)-immobilized Pseudomonas putida cells with surface-displayed metallothioneins to adsorb and recover Cu(II) ions from solutions. The immobilization conditions of P. putida cells via VRM, as well as the factors affecting Cu(II) biosorption, were optimized. Adsorption equilibrium was conducted for 60 min. The pseudo-second-order equation was applicable to all sorption data over the entire time course. The biosorption equilibrium data was described well by both Langmuir adsorption and Freundlich isotherm models. The maximum Cu(II) adsorption capacity on VRM-immobilized biosorbent was 22.23 mg g−1. The results from Fourier transform infrared spectroscopy indicated that recombinant P. putida cells were mainly responsible for the biosorption of Cu(II) ions. The engineered system exhibited high capacities of both Cu(II) adsorption and Cu(II) recovery in five continuous cycles of adsorption/desorption, which revealed that the system had high regenerability. Therefore, the VRM-immobilized biosorbent improved both mechanical strength and performance, showed potential for further large-scale or continuous operations.

► A new volcanic rock-bacterium-metallothionein triplicate metal sorbent system.
► The maximum Cu(II) adsorption capacity was 22.23 mg g−1.
► The system improved biosorption capacity, mass transfer and mechanical strength.
► Repeated adsorption/desorption operations showed high Cu sorption/recovery capacities.
► The regenerable and high-strength nature shows potential for continuous operations.