| With the widespread use of antibiotics in clinical practice,a large number of antibiotic residues are discharged into natural water bodies,which brings great health threats to human beings and aquatic organisms.Adsorption method has the advantages of high efficiency,green,simple operation and low cost,and is the first choice for water environmental pollution remediation.Biochar is widely used in the adsorption of organic pollutants in water because of its well-developed pore structure and large specific surface area.However,adsorption alone can not completely solve the essential problem,and advanced oxidation technology based on persulfate activation can quickly and completely mineralize antibiotics.The methods of activating persulfate mainly include thermal activation,alkali activation,transition metal activation,etc.The transition metal activation can be carried out at room temperature and in a wider pH range.Based on the above theories,in this paper,biochar(BC)was prepared from anaerobic fermentation biogas residue of kitchen waste,which was modified and optimized with hydrochloric acid to obtain HCl-BC material.After dipping HCl-BC with Co metal salt solution,magnetic biochar based composite CO-BC material was obtained.The mechanism of adsorption/degradation of typical antibiotics by HCl-BC and Co-BC materials was studied through material characterization,adsorption and degradation experiments.The specific research results are as follows:1、Biogas biochar(BC)is obtained by pyrolysis of biogas residue as raw material,and HCl-BC material is obtained by impregnating BC with hydrochloric acid.The results of scanning electron microscopy(SEM)and transmission electron microscopy(TEM)showed that after hydrochloric acid impregnation,a large amount of metal ash was removed from the surface of BC material,and the pore structure was improved,and the specific surface area was about 11 times of that before modification.The results of X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS)analysis show that HCl-BC is mainly composed of C element,and contains a small amount of quartz crystal and calcium carbonate.2、When HCl-BC material was used for tetracycline adsorption,the dosage of HCl-BC was 2 g/L at 25℃,the initial concentration of tetracycline was 20 mg/L,and the suitable pH range was 5-7,the adsorption effect of HCl-BC on tetracycline could reach 91.4%.The adsorption of tetracycline by HCl-BC conforms to the quasi-second-order kinetics,which is mainly chemisorption.The adsorption isotherm model is consistent with Freundlich model,belonging to multimolecular layer adsorption,and the adsorption process is facilitated by increasing temperature.3、Co-BC material was obtained by impregnating HCl-BC with cobalt chloride solution and adding sodium hydroxide solution to coprecipitate and pyrolysis cobalt ions with HCl-BC.The Co-BC material was characterized.The results show that the Co element in Co-BC material mainly exists in the form of CoO and Co elemental,the specific surface area of the material is increased by 74%,and the material surface has more types and quantities of functional groups than HCl-BC material.4、The experimental results of Co-BC on the degradation of Gatifloxacin showed that at 25℃,pH 7,0.01 g of Co-BC,20 mg/L of Gatifloxacin and 0.5 mmol/L of permonsulfate,the degradation of Gatifloxacin by Co-BC could reach 100%.In the process of Co-BC activated persulfate degradation of Gatifloxacin,two mechanisms of free radicals(sulfate radicals and hydroxyl radicals)and non-free radicals(singlet oxygen and oxidizing holes)are synergistic.In the radical degradation mechanism,sulfate radical plays a leading role and hydroxyl radical plays an auxiliary role.In the non-free radical degradation mechanism,the surface sp2 hybrid carbon networks,defect sites and free-flowing π electrons affect the electron configuration of permonophosphate,and the O-O bond breaks are activated and destroyed by electron transfer.Oxygen holes play a major role in the degradation mechanism. |
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