| Pyridine is widely used in agriculture,pharmaceutical industry and chemical industry.Because of its stable structure and high toxicity,the biodegradability of pyridine wastewater is poor.‘How to realize efficient biodegradation of pyridine from wastewater ? ’ is one of the hot issues in environmental science research.Screening and isolation of high-efficiency degradation dominant bacteria is an effective solution,but these dominant bacteria are disturbed easily by environmental conditions.Moreover,the cost of cultivating these dominant bacteria is very high and it is difficult to isolate and retain them.In order to improve theirs anti-environmental disturbance ability,the immobilization technology is used to form biofilm and enrich the dominant bacteria,which can effectively enhance theirs activity and stability,so as to strengthen the ability of biodegradation of pyridine and other refractory organic compounds.Therefore,in this study,a series of biochars were developed with waste biomass as raw materials,and the degradation of pyridine by the dominant bacterium Rhodococcus sp.PDX01 immobilized on biochar was studied.The adsorption of pyridine by biochar,the degradation of pyridine by biochar immobilized PDX01 and the treatment effect of actual wastewater were discussed.The relevant mechanisms were preliminarily analyzed by means of SEM,XRD,FTIR,EPR,elemental analysis and adsorption model.The main conclusions are as follows:(1)A series of biochars were successfully developed from waste biomass such as sawdust and apricot shell.Among them,sawdust biochar had the characteristics that were most conducive to microbial adsorption and fixation.The surface pore diameter of sawdust biochar was greater than 5 μm,which was conducive to the entry of PDX01 rod cells;The amount of positive charge on the surface was higher,and the water absorption was as high as 7.216 g water/g biochar,which was more conducive to the immobilization of microorganisms;The carbon content in the element composition was high,and the proportion of C/H was higher,indicating that the aromatization degree was higher than that of other biochars;In addition,the content of persistent free radicals in sawdust biochar was much lower than that of other biochars,which had less stimulation and damage to microorganisms.(2)The adsorption effect of the developed series of biochars on pyridine was as follows:activated carbon > apricot shell biochar > sawdust biochar,but the adsorption mechanisms of the three biochars were different.Among them,the process of sawdust biochar adsorbing pyridine was relatively well fitted with the quasi second-order kinetics,and its adsorption process was mainly controlled by chemical action.The adsorption kinetics of activated carbon and apricot shell biochar were basically consistent with the quasi first-order kinetics,and the adsorption process was mainly physical adsorption.(3)When influent p H,temperature and pyridine concentration was 7.0,35℃ and 200mg/L,the immobilized bacteria of sawdust biochar could completely degrade pyridine within 8 hours,which was 4-6 hours shorter than that of pure bacteria.Moreover,under different temperature conditions such as the concentration of Na Cl in wastewater was up to100 g/L and 25-45℃,the biochar immobilized bacteria showed higher treatment capacity and stability.(4)The process of pyridine degradation by sawdust biochar immobilized bacteria could be divided into two stages.The first stage was mainly completed through the adsorption of pyridine by sawdust biochar and the initial adhesion of PDX01 bacteria to the surface of the material to degrade pyridine;In the second stage,PDX01 bacteria almost occupied the active adsorption point on the material surface,and the degradation of pyridine in wastewater was realized by the intracellular and extracellular enzymes secreted by PDX01 bacteria. |
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