Fe^(3+)(NTA)还原菌的固定化小球制备及还原特性

Preparation and reduction performance of immobilized Fe^(3+)(NTA) reducing bacterium

采用海藻酸钠包埋驯化得到的优势铁还原菌,用于还原络合吸收法脱除NOx过程中形成的中间副产物Fe3+(NTA)。结果表明,最佳包埋条件为海藻酸钠质量浓度4%,菌体质量浓度0.2%,CaC l2质量浓度3%,此条件下制备的小球还原性能好,在微生物用量为20 g(湿重)/L时还原10 mmol/L Fe3+(NTA),经12 h反应后还原率达到96.1%,而相同条件下游离微生物的还原率仅为11.8%,但反应16 h后游离微生物与固定化小球的还原率相近,均为97%左右。但此法制备的小球机械强度不高,溶胀、破裂现象严重。通过添加聚乙烯醇和硅藻土改良固定化小球,可强化小球的机械强度、降低小球的溶胀及破裂现象,对Fe3+(NTA)的还原效果也较改良前的小球有所提高,两者最佳添加量均为20 g/L。改良后的小球与游离微生物相比,耐酸性增强,在pH=5的条件下,仍具有79.8%的还原效率,远高于相同条件下游离微生物的39.5%,但对温度的适应范围两者基本一致。

The immobilized beads were prepared using alginate embedding cultivated iron-reducing bacterium to reduce Fe^3＋ （NTA） , a byproduct formed in the process of NOx removal by ferrous chelate absorption. The beads were prepared when the mass fraction of alginate, cell and calcium chloride were 4% , 0.2% and 3% respectively,which had a good reduction performance. When using immobilized beads which microorganism amount was 20 g（wet weight）/L to reduce 10 mmol/L Fe^3＋ （NTA） , the reduction rate was 96. 1% after 12 h of reaction, while under the same condition, the reduction rate for dissociative microorganism was only 11.8% , and after 16 h of reaction, the reduction rates of two modes were about 97%. But the beads prepared using this method had low mechanical strength and serious swelling, fracture phenomenon. Ameliorating immobilized beads by adding polyvinyl alcohol and/or diatomite would improve the reduction efficiency and mechanical strength, and decrease the phenomenon of swelling and fracture to some extent. The optimal adding amount of PVA and diatomite were both 20 g/L. The modified beads had an enhanced acid resistant compared with dissociative microorganism. It still had 79.8% of reduction efficiency with a pH value of 5,which was higher than that of 39.5% by dissociative microorganism, while the adaptive range of temperature of both was almost the same.