生物法制备聚合硫酸铁及其应用研究_英文_(2)

WANG Hui-min, et al/Trans. Nonferrous Met. Soc. China 21(2011) 2542 2547 2543

2.4 Analytical methods

COD was measured by fast digestion- Reaction times Reaction time required/h

spectrophotometric method and the content of dyes 1 72

expressed as visible light absorbance at 665 nm was 2 65

measured by a visible spectrophotometer; the Zn 3 55

concentration in solution was measured by flame atomic

4 50

absorption spectrophotometry. Fourier transform infrared

5 48

spectroscopy (FTIR) was carried out on Nicolet Magna

550 to obtain the structural information of the BPFS above 85% was 72 h. However, the more reaction times composite. conducted, the less time was required. After 4 times

repeated cultivation, the reaction time requried for 3 Results and discussion oxidation rate above 85% was stabilized to be about 50 h, as listed in Table 1. 3.1 Preparation influence factors 3.1.1 Effect of temperature 2.2 Preparation of BPFS Temperature is very important for microbial growth

Based on breeding selection and domestication, and activity of microbial enzymes. To investigate the eosinophilic aerobic autotrophic bacteria T·f were effect of temperature on BPFS preparation, experiments selected as biocatalyst to prepare BPFS with were conducted at four different temperatures (20, 30, 35 FeSO4·7H2O as raw materials. Ferrous sulfate solution and 40 °C) with 10% inoculum at pH 2.0. The results are was prepared by dissolving a certain amount of shown in Fig. 1.

FeSO4·7H2O in deionized water, the pH value of the solution was adjusted with sulfuric acid. After the addition of essential nutrients, strains were introduced and cultivated in thermostatic waterbath at 30 °C. Under the catalysis of microbes, reddish-brown BPFS was synthesized through a series of oxidation, hydrolysis and polymerization reactions.

2.3 Flocculation experiments

To evaluate the flocculation effect of the prepared BPFS, flocculation experiments were carried out in a jar test apparatus. A lake water with high chemical oxygen demand (COD), a dye wastewater and a zinc containing

wastewater were tested. Selected properties of the tested

2+

Fig. 1 Impact of reaction temperature on conversion of Fesolutions were summarized in Table 2. The experimental

procedurzes were as follows: 5 mL BPFS was added to

It is shown that the conversion of Fe2+ at 30 and the jar and then filled with 400 mL tested solution.

35 °C is much stronger than that at 20 and 40 °C, Afterwards, the suspension was agitated at speed of

illustrating that too high or low temperature is likely to 40 60 r/min for 10 min, then it was left undisturbed for

result in significant decrease of Fe2+ oxidation rate, over 30 min, and the supernatant sample (200 300 mL)

moreover, high temperature increases the amount of was collected for further analysis.

sediment. Thus, the optimum temperature is 30 °C for

the preparation of BPFS. Table 2 Selected properties for tested solutions

3.1.2 Effect of pH Absorbance 2+

COD/ ρ(Zn)/pH is critical to the preparation process, as pH Solution pH (methylene 1 12+(mg·L) (mg·L)increases, the oxidation of Fe gets weak and more blue)

precipitation is generated, lowering the basicity of the

Lake water 6.72 7.02 330 product. However, too low pH is also unfavorable for the

oxidation of Fe2+ due to the inhibition of bacteria growth, Dye

8.0 0.143

and it tends to make the prepared product has strong wastewater

corrosivity, therefore, the pH value of the reaction

Zinc

solution should be well-controlled.

5 6 200 containing

The effect of pH is studied at various pH (2.0, 1.8

wastewater

and 1.5) with other experimental conditions constant.

Table 1 Adaptation results of T·f bacteria