Study On The Remediation Of Chromium And Other Heavy Metals Pollution By Modified Biochar And Dominant Bacterial Flora

At present,the situation of environmental heavy metal pollution is becoming more and more serious,and its remediation is urgent.In contrast,bioremediation using microorganisms such as bacteria is low-cost,but slow and affected by concentration;remediation using adsorbent materials such as biochar is broad-spectrum and fast-acting,but has limited capacity.Based on the FBC,which is a magnetic iron oxide loaded biochar with good removal effect on both chromium/arsenic,this study further explores the modification method to improve the adsorption capacity of FBC,and uses the modified biochar and domesticated chromium removal dominant bacteria for the remediation of chromium polluted water and soil with chromium as the main research object.Its passivation effect on arsenic-contaminated soil was also studied to investigate whether the technology of modified biochar combined with dominant flora could be used for remediation of heavy metal pollution in a broad-spectrum,efficient and low-cost manner.The results are as follows:（1）Biochar BC,phosphoric acid activated biochar HBC and iron oxide loaded phosphoric acid activated biochar HFBC,which are effective in the removal of Cr（VI）,were produced by exploring the conditions such as pyrolysis temperature and atmosphere,using Cyperus rotundus as raw material.The phosphoric acid activation increased the adsorption capacity of the biochar,with the maximum adsorption capacity of 2.03 mg g^-1for BC and 24.41 mg g^-1for HBC for 50 mg L^-1Cr（VI）,and55.5 mg g^-1for HFBC after loading iron oxides.The mechanism of Cr（VI）removal by HFBC is mainly adsorption and reduction,and the adsorption behavior is consistent with the quasi-secondary kinetic model and Langmuir model.The removal rate of Cr（VI）by HFBC is stable at p H 5.0-9.0 and can be applied to most water bodies and soils.（2）The efficient strains with good removal effect on Cr（VI）were obtained by screening.The single strain was not stable in the environment,so the efficient chromium removing strains were combined to obtain an efficient chromium removing colony consisting of strain Shivella 4H（referred to as 4H）and strain Bacillus BC4（referred to as BC4）.4H+BC4 achieved 99.29%removal of 100 mg L^-1Cr（VI）at p H8.0 for 60 h.The removal of chromium by the colony was high under neutral and alkaline conditions,and the removal rate was negatively correlated with the initial concentration,while temperature（25-42°C）and inoculum（1%-8%）only affected the removal rate.Bacterial flora dominated the growth of 4H in the early stage and BC4 in the later stage during the treatment of Cr（VI）.（3）The study on the removal of Cr（VI）from water by modified biochar combined with dominant bacteria showed that the removal of chromium was more effective at neutral and alkaline levels.The removal rate decreased with the increase of initial concentration.When the p H was 8.0,4H+BC4 and HFBC were added at 2%inoculum and 1g L^-1dosage,and the initial concentration increased from 100 to700mg L^-1,the removal rate of Cr（VI）decreased from 99.65%to 17.36%in 36 hours of treatment.(The maximum removal rate of 100 mg L^-1Cr（VI）by HFBC alone was about 48%)（4）A study on the passivation of chromium in soils by modified biochar combined with dominant flora showed an increase in soil p H of 0.45,an increase in CEC of 9.32 cmol kg^-1and a 97.65%reduction in the effective state of chromium in the 0.9%HFBC+flora treated group after 35 days compared to day 1;Increased abundance and diversity of bacterial communities in soils;The addition of HFBC and bacterial flora also promoted the growth of the test crop hollow cabbage and reduced the accumulation of chromium in the cabbage,and the higher the proportion of modified biochar added,the more obvious the growth promotion effect on hollow cabbage.（5）In order to investigate whether the produced modified biochar and the dominant bacteria also have passivating effects on other heavy metals,the two were combined for the treatment of arsenic-contaminated soil.Similar to the treatment of chromium containing soils,soil p H and CEC were increased and the effective state arsenic content was reduced by 80.28%in the 0.9%HFBC+colony treatment group;HFBC and colony dosing also promoted the growth of hollow cabbage and reduced the accumulation of arsenic in the vegetable.