Preparation Of Sludge-based Biochar And Its Adsorption Of Ciprofloxacin Hydrochloride

In recent decades,a large amount of municipal sludge has been produced in China.However,because the sludge waste often contains various pollutants and cannot be directly discarded,dumped and buried,the treatment and reuse of sludge waste has become a research hotspot in recent years.Heat treatment is used to convert sludge waste into functional biochar and valuable biofuel,providing an economical and environmentally friendly method for sludge recycling.Therefore,in this study,different biochar were prepared by using the residual sludge of sewage treatment plants.The adsorption performance of biochar was optimized by optimizing the process conditions,and the adsorption performance of biochar on ciprofloxacin hydrochloride was studied.The main conclusions are as follows:(1)In this paper,sludge was used as raw material and ciprofloxacin hydrochloride was used as the target pollutant.Sludge based biochar(BC500-5,BC500-10,BC500-20,BC700-5,BC700-10,BC700-20,800-5,BC800-10,BC800-20)were prepared at the heating rate of5℃/min,10℃/min and 20℃/min.Through the heating rate experiment,it was found that the removal rate of biochar prepared at the heating rate of 10℃/min was higher than that prepared at 5℃/min and 20℃/min.With the increase of the dosage of BC500-10,BC700-10 and BC800-10 adsorbents,the removal rate of biochar on ciprofloxacin hydrochloride also increased.When the dosage was 0.08 g,the removal rate of BC500-10 on ciprofloxacin hydrochloride reached the highest,and the removal rate was 94.46%.The removal rates of ciprofloxacin hydrochloride by BC700-10 and BC800-10 were 88.9% and 80.63%,respectively.With the increase of solution p H,the removal rate of ciprofloxacin hydrochloride by BC500-10,BC700-10 and BC800-10 was firstly increased and then decreased.When p H=5,the removal rate of ciprofloxacin hydrochloride by BC500-10,BC700-10 and BC800-10 was the highest.With the increase of the initial solution concentration,the removal rate of ciprofloxacin hydrochloride by BC500-10,BC700-10 and BC800-10 gradually decreased.Through SEM and BET characterization of biochar materials,the specific surface area and pore size of BC500-10 are larger than those of BC700-10 and BC800-10,and the pore structure is rich,indicating that the specific surface area and pore size of biochar are affected by pyrolysis temperature.FTIR showed that the biochar prepared by sludge pyrolysis formed characteristic absorption peaks,and XRD showed that the oxygen-containing functional groups on the surface were increased by pyrolysis.(2)Taking sludge and red mud with different mass ratios(1:3,2:2,3:1)as raw materials,Biochar with different final pyrolysis temperatures(BR500-3/1,BR500-2/2,BR500-1/3,BR700-3/1,BR700-2/2,BR700-1/3,BR800-3/1,BR800-2/2,BR800-1/3)were prepared.The effects of different mass ratios of sludge and red mud(1:3,2:2,3:1)on the adsorption of ciprofloxacin hydrochloride were studied.Through experiments,it was found that when the ratio of sludge to red mud was 3:1,the removal rate of biochar on ciprofloxacin hydrochloride was higher than that when the ratio of sludge to red mud was 2:2 and 1:3.The removal rate of ciprofloxacin hydrochloride by biochar increased with the increase of biochar dosage.With the increase of solution p H,the removal of ciprofloxacin hydrochloride by BR500-3/1,BR700-3/1 and BR800-3/1 was firstly increased and then decreased.When p H=5,the removal rate of ciprofloxacin hydrochloride by BR500-3/1,BR700-3/1 and BR800-3/1was the highest.With the increase of the initial concentration of solution,the removal rate of ciprofloxacin hydrochloride by BR500-3/1,BR700-3/1 and BR800-3/1 decreased.Through SEM and BET characterization of biochar materials,it is found that red mud affects the development of biochar pore structure.XRD shows that red mud reduces the degree of graphitization of the material.(3)Study on removal of ciprofloxacin hydrochloride by activated biochar with persulfate.The effects of the molar ratio of persulfate to ciprofloxacin hydrochloride(2:1,20:1,40:1,100:1,200:1)on the removal of ciprofloxacin hydrochloride were studied.When the molar ratio of persulfate to ciprofloxacin hydrochloride was 40:1,BR500-3/1,BR700-3/1,BR 800-3With the increase of p H,the removal rates of ciprofloxacin hydrochloride by BR500-3/1,BR700-3/1 and BR800-3/1 gradually decreased.when p H=1,the removal rates of BR500-3/1and BR700-3/1 were 96.46%,96.26% and 94.36%.When the initial concentration of solution was 0.5mg/L,the adsorption removal rate of ciprofloxacin hydrochloride by BR500-3/1 was99.56%.The removal rates of ciprofloxacin hydrochloride by BR700-3/1 and BR800-3/1were 99.35% and 97.12%,respectively.(4)Through the adsorption kinetics model fitting,the adsorption of biochar for ciprofloxacin hydrochloride was observed to conform to the quasi-second-order kinetics model;The adsorption of biochar is an endothermic,spontaneous and entropy-increasing process through isothermal adsorption and thermodynamic study.