| With the rapid development of mining,smelting and electroplating industries,heavy metal pollution is becoming increasingly serious.Immobilized microorganism has the advantages of fast biochemical start-up,strong toxicity resistance and absorption ability,attracting attention from many researchers.However,there are few studies on the immobilization of growing microorganism.In this study,growing Bacillus cereus RC-1 was immobilized on the biochars derived from rice straw,chicken manure and sewage sludge;bio-accumulation characteristics and mechanisms of three beads were also determined qualitatively and quantitatively.(1)Immbolization preparation.Optimal preparation of RSB-beads,CMB-beads and SSB-beads requires sodium alginate of 4?4?4 g,biochar 1.5?0.8?1 g,bacteria 5?25?25 m L,and crosstime 6?4?2 h,respectively.Immobilized beads have a diameter range of3.0-4.0 mm,density between 1.10-1.20 g/cm~3,with good mechanical strength and stability.(2)Bio-accumulation characteristics.The beads reached the maximum after about 22h,while free bacteria need 16 h.The highest capacity as follow RSB-beads(158.77mg/g)>CMB-beads(132.09 mg/g)>SSB-beads(110.14 mg/g)>free bacteria(60.85 mg/g),the highest capacity of RSB-beads was 2.6 times higher than suspended cells.Additionally,their reusability was 96.6%,95.0%and 96.3%,respectively.(3)Bio-accumulation mechanisms.The mechanisms included physical entrapment,ion-exchange,complexation and precipitation.Ion-exchange was the predominant mechanism in RSB-beads(39.5%-45.7%)and SMB-beads(41.4%-46.8%),while the dominant mechanism of SSB-beads was complexation with functional groups,accounting for 56.9%-66.8%.Biochar played a dual role of adsorbent and carrier,but did not provide nutrients to the bacteria. |
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