Characteristics of Bacillus sp. PZ-1 and its biosorption to Pb(II)

Abstract

During the long and cold winter season in northern area of China, wastewater treatment is often inefficient which causes the substandard discharge. In this study, a lead-resistant psychrotrophilic bacterium was isolated and used as an adsorbent to remove Pb(II) from aqueous solution at 15°C. The strain was identified and designated as Bacillus sp. PZ-1 based on the morphology, physiological–biochemical experiments and 16S rDNA sequence analysis. The minimal inhibitory concentration and antibiotic experiments revealed that PZ-1 had high resistance to 1500mgL−1 of Zn(II), 800mgL−1 of Cu(II), 400mgL−1 of Ni(II), 15µgmL−1 of chloramphenicol and 50µgmL−1 of streptomycin, but susceptibility to 200mgL−1 of Co(II). Scanning electron microscopy, energy dispersive X-ray spectroscopy and atomic force microscopy analyses showed that biosorption of Bacillus sp. PZ-1 to Pb(II) involved surface adsorption, ion exchange and micro-precipitate. Fourier transform infrared spectroscopy analyses indicated that hydroxyl, carbonyl and carboxyl on cells may play vital roles in Pb(II) adsorption. Besides, siderophore secreted by PZ-1 had beneficial impacts on the Pb(II) removal. Biosorption experiments were carried out as a function of initial Pb(II) concentration (50–500mgL−1), pH (3.0–7.0), biomass concentration (5–50gL−1) and contact time (5–40min). Biosorption rate of 93.01% with adsorption capacity of 9.30mgg−1 was obtained under the initial Pb(II) concentration of 400mgL−1, pH of 5.0, contact time of 20min, biomass concentration of 40gL−1 and the temperature of 15°C. The equilibrium data were well fitted with Langmuir model, which indicated the adsorption process of Pb(II) is monolayer adsorption. Bacillus sp. PZ-1 appeared to be an efficient biosorbent for removing Pb(II) from wastewater at low temperature.