Study On The Performance And Mechanism Of Biochar Loaded With Efficient Degrading Bacteria And Co₃O₄ To Remove Typical Organic Pollutants In Water

Many organic pollutants enhance their stability due to their complex structures,which makes them difficult to degrade and remaining in water for a long time,thus causing environmental pollution.Among them,pentachlorophenol（PCP）and ciprofloxacin（CIP）are typical pollutants because of their great environmental harm and difficulty in degradation.They are persistent in the environment.Also,they can accumulate in organisms with the food chain and produce many adverse reactions,even cause cancer,physical deformities and mutations,which will seriously affect the ecological environment and human health.Therefore,it is of great theoretical significance and practical value to study an efficient,economic and green treatment technology for PCP and CIP organic pollution in water.Biochar has become a high-quality carrier material in the field of environmental remediation because of its environmental friendliness and special morphological feature and composition.Firstly,as a strong adsorbent,biochar can fix the target pollutants on its surface,limiting their fluidity and reducing their environmental harm.Secondly,taking biochar as the bottom plate can realize the uniform dispersion of the materials loaded on it,further increase the contact surface between the materials and the target pollutants,resulting in the increase of the degradation efficiency.Finally,the loading of biochar can reduce the agglomeration and leakage of the loaded materials,so as to improve the stability and reuse rate of the materials.Physical,chemical and biological methods are the most common treatment methods for PCP and CIP water pollution.Using biochar having the characteristics of physical adsorption as adsorption material and carrier material,combined with chemical method or biological method,has become a new way to develop new pollution treatment technology.In this paper,rice straw and wastewater treatment sludge were used to prepare biochar（BC）,and specific bacteria that can degrade PCP efficiently were screened out.Then,biochar was used as carrier to load highly-efficient PCP-degrading bacteria and Co₃O₄,to prepare new composite materials named as BC@PN and BC@CNP,respectively.Furthermore,they were characterized,analyzed,and applied to remove PCP-Cd（Ⅱ）compound pollution and CIP from water,and the influencing factors and mechanisms were clarified.The main conclusions are as follows:（1）A Cd-resistant PCP-degrading strain was isolated from different sources by domestication culture.The colony was round,non-convex,white and dry;The bacterium was oblong,about 10～16μmlong and about 3～6μmwide.And it was identified as Pseudomonas nitroreducens（PN）by 16Sr DNA gene identification method.（2）Rice straw biomass was pyrolyzed at 800℃to form biochar material with high loading performance.SEM observation showed that PN cells were successfully loaded on BC and thus PN immobilization was realized.（3）For the combined pollution of PCP-Cd（Ⅱ）,the biochar loaded with high-efficiency degrading bacteria could reduce the concentration of PCP and Cd（Ⅱ）by98.6%and 96.1%,respectively under the conditions of adsorption material dosage of 1g/L,temperature of 25℃and 7.0 pH value,which is better than the treatment effect of single biochar or degrading bacteria.（4）BC formed by high-temperature pyrolysis of sludge biomass at 800℃was precipitated and mixed with Co material.BC-Co₃O₄precursor was obtained through hydrothermal reaction,and then calcined to form nano plate structure BC@CNP compound material.SEM,XRD and XPS analysis showed that Co₃O₄nanoplates were successfully loaded on BC,and the crystal structure of Co₃O₄remained same before and after recombination.（5）In BC@CNP/PI system,catalytic oxidation and adsorption worked together to improve the reaction rate.With the increase of the dose of each component in BC@CNP/PI system,the removal rate of CIP was further improved.The change of pH affected the removal effect of CIP.The best removal condition of CIP was 0.1 g/L BC@CNP,0.2 g/L PI,10 mg/L CIP,initial pH 9,reaction time 120 min.At the same time,inorganic anions in the environment had little effect on the CIP removal by BC@CNP/PI system,which proved that the stability of BC@CNP/PI system in removing CIP in water.Quenching experiments and EPR showed that singlet oxygen（¹O₂）was main active species for oxidative removal of CIP in BC@CNP/PI system,hydroxyl radical（·OH）was the secondary active substance,the electron transfer mechanism also played a role,indicating that the free radical and non-free radical degradation mechanisms played a common role in the reaction.The removal technologies of PCP-Cd（Ⅱ）compound pollution and CIP from water studied in this paper have achieved better treatment effects,and furthermore they are environmentally safe and efficient.The research results can provide new methods and basic data for the remediation of these two kinds of polluted water environments.