| Azo dyes are widely used as dyes due to their wide spectrum and low cost,but their strong stability makes them difficult to be effectively degraded by ecosystems.At present,anaerobic biological treatment of azo dyes is a relatively cost-effective and non secondary pollution reduction process,which has become the main method for degradation of azo dyes.However,due to the toxicity of azo dyes,the metabolic rate of anaerobic microorganisms becomes slow and electron transfer is blocked.Therefore,it is necessary to strengthen the anaerobic biodegradation of azo dyes.In addition,sludge contains a large amount of organic matter and metal ions,which can cause serious environmental pollution if discharged directly.How to realize the resource utilization of sludge has become a research hotspot.Among them,the preparation of iron carbon composite materials from sludge to enhance anaerobic biological treatment process has a high application prospect.In this paper,iron sulfate is used as an activator to prepare iron carbon composite materials from sludge through pyrolysis,and they are added to anaerobic biological systems to explore their enhanced biodegradation efficiency,providing a new method for sludge recycling and efficient removal of high concentration azo dye wastewater.The main research contents and conclusions are as follows:(1)With characterization methods such as X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),and specific surface area(BET),the physical and chemical properties of different iron carbon composites were investigated,and then the removal efficiency of different iron carbon composites as adsorbent for methyl orange(MO)was studied.Kinetic models and isothermal models were used to fit and analyze the adsorption capacity of iron carbon composites for MO.The characterization results showed that the substances contained in the iron carbon composite,the functional groups on the surface,and the specific surface area were affected by the pyrolysis temperature and the mass fraction of iron salts.In the dye removal experiment,it was found that the iron carbon composite material with a pyrolysis temperature of 400℃ and a mass ratio of0.6 had the best adsorption performance for MO.At this time,the maximum adsorption capacity for MO was 23.57mg/g,and the removal rate was 96.01%.Based on the data fitting analysis,it was found that the adsorption kinetics of iron carbon composites for MO conformed to Pseudo-second order model,indicating that the rate mechanism of dye adsorption may be determined by chemical adsorption.Through isothermal model analysis,it can be concluded that both homogeneous monolayer adsorption and heterogeneous multi molecular layer adsorption coexist in the adsorption process of Fe/C-400-0.6 for MO.(2)The strengthening effect of iron carbon composite materials on anaerobic biodegradation of azo dyes was studied,and the reaction mechanism was analyzed from the perspective of microbial community structure.Firstly,the domestication of anaerobic sludge can be concluded that the initial concentration of azo dyes affects the degradation of anaerobic sludge;In the co-digestion experiment of sodium acetate wastewater,the degradation rate of azo dyes by anaerobic sludge reached82.33%;After removing additional carbon sources,MO can still be efficiently degraded by anaerobic sludge only under wastewater conditions.Characterization by Ultraviolet visible absorption spectrum and high performance liquid chromatography showed that MO degradation is mainly through reduction rather than adsorption.When iron carbon composite materials were added to the anaerobic biological system,the degradation rate of MO increased from 47.18% to 90.78%,and the formation rate of ABS increased from 37.11% to 66%.At the same time,the analysis of microbial communities showed that the addition of iron carbon composite materials can enrich the electrochemical active bacteria(Proteobacteria)and iron reducing bacteria(Geobacter)in the anaerobic biological system,accelerate the transfer of electrons,and further promote the degradation of anaerobic organisms and azo dyes.This indicates that iron carbon composite materials have a significant strengthening effect on anaerobic biodegradation of azo dyes.(3)To explore the anaerobic biodegradation process of azo dyes enhanced by different iron carbon composites and determine the optimal reaction conditions.The experimental results showed that the iron-carbon composite material with the same pyrolysis temperature and a mass ratio of 0.6 had the strongest enhancement effect on the degradation of MO in the anaerobic biological system,and the degradation rate increased from 31.13% to 75.07% within 10 hours;In the same mass ratio,the iron carbon composite material with a pyrolysis temperature of 400℃ has the strongest strengthening effect when added to the biological system,and the degradation rate of MO increases from 37.57% to 80.2% within 12 hours.This is due to the rich oxidation-reduction functional groups and iron oxides on the surface of this material,which can better carry out electron transfer;within the range of p H,temperature,and dosage studied,when p H is 7,temperature is 50℃,and dosage is 1g,the degradation effect is the best.From this,it can be concluded that the optimal reaction conditions for iron-carbon composite materials with a pyrolysis temperature of 400℃ and a mass ratio of 0.6 were p H 7,temperature of 50℃,and dosage of 1g.At this time,azo dyes in the anaerobic biological system were basically completely removed,which can effectively improve the removal effect of azo dyes.Figure [37] table [13] reference [133]... |
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