The simultaneous removal of Cr(Ⅵ) and phenol in a consortium culture containing Cr(Ⅵ) reducer, Bacillus sp. and phenol degrader, Pseudomonas putida Migula (CCTCC AB92019) was studied. Phenol was used as the sole carbon source. Bacillus sp. utilized metabolites formed from phenol degradation as electron donors and energy source for Cr(Ⅵ) reduction. Optimum Cr(Ⅵ) reduction was observed at a phenol concentration of 150 mg/L and an initial Cr(Ⅵ) concentration of 15 mg/L. Both the Cr(Ⅵ) reduction and phenol degradation were influenced by the cell composition of the culture, but the phenol degradation was not significantly affected by the content of Bacillus sp. The experiments also showed that the amount of phenol degraded was more than that stoichiometrically required for Cr(Ⅵ) reduction.
Four chromium(Ⅵ)-resistant bacteria named YB-1,YB-2,YB-3 and YB-4 were isolated from Cr-electroplating sludge. YB-1 and YB-2 were identified as a member of Bacillus sp.based on morphology and Biolog Microstation System.The strain of YB-1 was selected to test for its resistance and ability to remove Cr(Ⅵ)from aqueous solution.The results indicate that YB-1 exhibits high MIC value which can almost reach 140 mg/L and the growth of YB-1 in liquid medium containing 60 mg/L Cr(Ⅵ)is affected especially in the late exponential phase and stationary phase.Furthermore,the potential of living and freeze-dried YB-1 biomass to remove Cr(Ⅵ)was studied in different pH,biosorbent dose,contact time and initial concentration using the batch method. At the optimal conditions,living and freeze-dried biomass are capable of absorbing 34.5 mg/g and 17.8 mg/g chromium(Ⅵ)at initial concentration of 60 mg/L,respectively.The adsorption data were fitted to Langmuir isotherm model for these two sorbents.Kinetic studies show that the rates of sorption all follow the pseudo-second order kinetics.
The experiment was designed to study whether the decrease of Cd in the rhizosphere of Zhongyouza Ⅰ ,one breed of oilseed rapes (Brassica junica) that can hyperaccumulate cadmium from the soil, can improve the living condition of less Cd-tolerant plant pai-tsai (Brassia chinensis) with their roots permitted to intermingle and develop coincident rhizosphere. The extent of rhizosphere interactions between ZhongyouzaⅠ and pai-tsai was controlled by different root barriers, or without barrier. The results show that in the 10 and 20 mg/kg Cd treated soils, pai-tsai gets higher shoot mass and less Cd accumulation in its shoot than in the barrier treatments or in the mono cultures, when its roots are permitted to intermingle with those of ZhongyouzaⅠ .Meanwhile, soil decontamination rates of ZhongyouzaⅠ are not affected much by co-cropping with pai-tsai, they are 80.0% and 91.8% of that in the mono cultures of ZhongyouzaⅠ, respectively. However, the co-cropping method in meliorating the living condition of pai-tsai is not obvious when Cd concentration in soil reaches 40 mg/kg, and soil decontamination rate decreases to 0.14, which is 58.3% of that in the mono culture. These results indicate that the oilseed rape ZhongyouzaⅠ may alleviate Cd toxicity of surrounding less-tolerant species, and its ability of phytoremediation is not affected much at the same time, especially in the middle polluted soil.
The potential of living Aspergillus niger to remove cadmium and zinc from aqueous solution was investigated. Effects of pH, initial concentration, contact time, temperature and agitation rate on the biosorption of Cd(Ⅱ) and Zn(Ⅱ) ions were studied. The optimum adsorption pH value for Cd(Ⅱ) and Zn(Ⅱ) were 4.0 and 6.0. The best temperature and agitation rate were in the range of 25?30 ℃ and 120 r/min for all metal ions. Under the optimal conditions, the maximum uptake capacities of Cd(Ⅱ) and Zn(Ⅱ) ions are 15.50 mg/g and 23.70 mg/g at initial concentrations of 75 mg/L and 150 mg/L, respectively. Biosorption equilibrium is established within 24 h for cadmium and zinc ions. The adsorption data provide an excellent fit to Langmuir isotherm model. The results of the kinetic studies show that the rate of adsorption follows the pseudo-second order kinetics.
The structure of Pb, Zn, Cu and Cd in lead zinc ore tailing soils in Yongzhou, Hunan is analyzed by the optimized BCR sequential extraction procedure. The content and proportion of heavy metals of the mine are measured. Meanwhile, the ecological risks are evaluated with the Lars Hakanson’s potential ecological risk exponential method. The analysis shows that the content of heavy metals is very high, reaching the level of serious pollution. The order of metal pollution degrees are Cd>Pb>Cu>Zn. On the other hand, it is very possible that the heavy metals may combine together as compounds or cling to the crystal form of clay. Since the form of soluble acid and free metals are very little, it is not an easy job for metal eluting or restoration of plants. Yet it is possible to take out those heavy metals adopting the chemical extraction technology. DTPA and EDTA, indicated by a research, both have iterative value and strong conformity effect. So they are effective elutriants to restore the polluted soil. A chemical extraction method is put forward in this paper.
