Cobalt(II) bioaccumulation and distribution in Rhodopseudomonas palustris

Figures & data

Figure 1. Effect of metabolic pathways on Co²⁺ removal efficiency and growth incubated in the enrichment medium with the addition of 80 mg/L Co²⁺, 30 °C and pH 6.5. The error bars represent the standard deviation at n = 3.

Figure 2. Effect of pH on Co²⁺ removal efficiency and growth incubated in the enrichment medium with the addition of 80 mg/L Co²⁺, 30 °C and aerobic condition in darkness. The error bars represent the standard deviation at n = 3.

Figure 3. Effect of temperature on Co²⁺ removal efficiency and growth incubated in the enrichment medium with the addition of 80 mg/L Co²⁺, pH 6.5 and aerobic condition in darkness. The error bars represent the standard deviation at n = 3.

Figure 4. Effect of co-cations on Co²⁺ removal efficiency incubated in the enrichment medium with the addition of 80 mg/L Co²⁺, pH 6.5, 30 °C and aerobic condition in darkness. The error bars represent the standard deviation at n = 3.

Figure 5. Effect of initial cobalt concentration on growth incubated in the enrichment medium, pH 6.5, 30 °C and aerobic condition in darkness. The error bars represent the standard deviation at n = 3.

Figure 6. Removal of different concentrations of Co²⁺ by R. palustris, pH 6.5, 30 °C and aerobic condition in darkness. The error bars represent the standard deviation at n = 3.

Table 1. Pseudo-first-order model kinetic equations and kinetic parameters of the removal for different concentration of cobalt by growing R. palustris.

Co^2+ (mg/L)	K	R^2	$C=C_0{e}^{-kt}$
20	0.0540	0.9184	$C=24.53e^{-0.05403t}$
40	0.0546	0.8881	$C=49.96e^{-0.05465t}$
80	0.0500	0.8905	$C=98.00e^{-0.0498t}$
120	0.0429	0.8639	$C=146.92e^{-0.04287t}$
160	0.0264	0.7848	$C=181.06e^{-0.02636t}$

Table 2. Pseudo-second-order model kinetic equations and kinetic parameters of the removal for different concentration of cobalt by growing R. palustris.

Co^2+ (mg/L)	$-\text{d}C/\text{d}t=k_2{C}^2+k_{1}C+k_0$	p	q	h	R^2
20	$-\text{d}C/\text{d}t=-0.0108C^2+0.2672C-0.5368$	0.2195	2.2083	22.5324	0.9519
40	$-\text{d}C/\text{d}t=-0.0069C^2+0.3358C-1.3400$	0.2753	4.3862	44.2804	0.9583
80	$-\text{d}C/\text{d}t=-0.0031C^2+0.2979C-2.3955$	0.2429	8.8710	87.2258	0.9931
120	$-\text{d}C/\text{d}t=-0.0024C^2+0.3201C-4.549$	0.2424	16.1875	117.1875	0.9575
160	$-\text{d}C/\text{d}t=-0.0014C^2+0.2437C-4.2584$	0.1871	20.2607	153.8300	0.9508

Figure 7. Cobalt compartmentalization in selected cell sectors of R. palustris.

Figure 8. X-ray diffraction spectra of R. palustris cells: (a) metal-free control; (b) Co²⁺-loaded (80 mg/L, 40 h) biomass.