Cadmium Resistance, Microbial Biosorptive Performance and Mechanisms of a Novel Biocontrol Bacterium Paenibacillus sp. LYX-1

In order to explore whether the newly discovered biocontrol strain Paenibacillus sp., LYX-1 having antagonistic effect on peach brown rot was resistant to Cd2+, a series of growth of strain LYX-1 under different Cd concentration and biosorption experiments were conducted to living and dead strain LYX-1. Meanwhile, the Cd2+ resistance and biosorption mechanisms were further identified by Cd-resistant genes, TEM, SEM-EDS, FTIR and XPS analysis. The results showed that strain LYX-1 could resist 50 mg/L Cd2+ and the adsorption process of both living and dead strain LYX-1 all satisfied the pseudo-second kinetic equation. Under pH 8.0 and at a dose of 1.0 g/L strain, the removal capacities of living and dead cells were as high as 90.39% and 75.67% at 20 mg/L Cd2+, respectively. For the adsorption isotherm test, results revealed that both Langmuir (R2=0.9704) and Freundlich (R2=0.9915) model could describe the Cd2+ biosorption well for living strain LYX-1. The maximum equilibrium biosorption capacities of living and dead biomass were 30.6790 and 24.3752 mg/g, respectively. The adsorption mechanism was controlled by chemisorption with -OH, -NH, -C=O, O=C-O, C-N, S2− and phosphate functional groups on the cell surface of strain LYX-1, which were further identified by XPS. The insignificant biosorption difference of living and dead biomass was caused by CzcD gene in strain LYX-1 detoxifying cadmium through the heavy metal efflux system. The above results indicated that strain LYX-1 had higher tolerance and fixed capacity to Cd2+.

Adsorption of chromium (Cr6+) on dead biomass of Salvinia molesta (Kariba weed) and Typha latifolia (broadleaf cattail): isotherm, kinetic, and thermodynamic study

This study evaluated the adsorption of Cr6+ from aqueous solution using dead biomass of aquatic plants Salvinia molesta (Kariba weed) and Typha latifolia (broadleaf cattail). The batch experiments were carried out to study the effects of pH, adsorbent dose, initial metal concentration, contact time, agitation speed in rotation per minute (rpm), and temperature. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to characterize the adsorbent and analyze the functional groups and morphology of the adsorbent, respectively. The hydroxyl and amine groups were the main functional groups involved in the adsorption. Both adsorbents showed good results at pH 1, metal concentration of 20 mg/L for Cr6+ removal, and adsorption equilibrium was attained within 60 min with 150 rpm at 25 °C. The adsorption rate obtained was above 95% for both the adsorbents at a dose of 0.150 g for S. molesta and 0.8 g for T. latifolia. Isotherm and kinetic models were applied on the adsorption data. The monolayer adsorption capacity (qm) was found to be 33.33 mg/g for S. molesta and 10.30 mg/g for T. latifolia. The Langmuir isotherm was better fitted to S. molesta, while the Freundlich isotherm was better fitted to T. latifolia. It was reported that the pseudo-second-order model (R2 = 0.999) was better fitted to the adsorption data for both the adsorbents. The thermodynamic study was also conducted and found the adsorption process was exothermic and spontaneous. Results revealed the good adsorption potential of S. molesta and T. latifolia, and they can be used for the removal of hexavalent chromium.

Kinetic and thermodynamic studies for evaluation of adsorption capacity of fungal dead biomass for direct dye

This study focuses on evaluation of degradation aptitude of white rot fungus (Coriolus versicolor) against Indosol Turquoise FBL dye. The outcome of numerous parameters including pH, temperature, carbon sources, nitrogen sources, C/N ratio and effect of dye concentration were studied. Maximum decolorization (99.896%) of Indosol Turquoise FBL was obtained by C. versicolor under optimized conditions. After three days, the maximum dye degradation (98%) was observed at pH 4 and 30 °C. Six carbon sources fructose, glucose, maltose, sucrose, rice bran and wheat bran were used and 96.66% degradation was observed by maltose at its optimum growth concentration (0.1 g/100 mL). Various nitrogen sources were employed for decolorization but ammonium nitrate decolorized dye up to 98.05%. The activity of three different enzymes laccase, Lignin peroxidase (LiP) and Manganese peroxidase (MnP) were calculated. The dead biomass of White rot fungus (WRF) was used for biosorption experiments. Maximum q (36 mg/g) was obtained at pH 2, at 30 °C using 0.05 g biosorbent. An increase in the q value was observed with increase in dye concentration. Freundlich adsorption isotherm and pseudo second order kinetics were followed by the data. It can be concluded that C. versicolor could be an efficient source for degradation of dyes from industrial effluents.

Isotherm, Kinetics and Thermodynamic Studies of Hexavalent Chromium Adsorption by Using Dead Biomass of Eichhornia crassipes

This study examined the utilization of Raw Eichhornia crassipes (REC) biomass to exclude the hexavalent chromium heavy metal from synthetic liquid for determination of sorption isotherm, kinetics and thermodynamic parameters of adsorption during the batch experiment process. The effect of adsorbent doses, agitation time and temperature on sorption capacity was studied. The plot qt versus t1/2 determined the intra-particle diffusion effect, which was not passing from the origin of plot indicated that apart from intra-particle diffusion some other mechanism also involved in this study. Freundlich isotherm better fitted as compared to Langmuir isotherm in the present study. The kinetics study show that pseudo-second-order better followed by REC adsorbent. At 293 K temperature, Δ Go negative value suggested that process favoured the sorption and spontaneous in nature, but at higher temperatures, positive values Δ Go confirmed the non-spontaneous nature of adsorption. It is concluded that Eichhornia crassipes dead biomass has the potential to treat wastewaters as an adsorbent.