Study On The Effect Of Modified Fly Ash On The Removal Of Ciprofloxacin From Aquaculture Wastewater

With the continuous development of large-scale livestock and poultry farming in China,the problem of farming wastewater pollution has become more and more concerned.The low removal of antibiotics and heavy metals from wastewater is an urgent and challenging environmental issue for many developing countries due to current wastewater treatment technologies.Currently,it is detected in surface water,groundwater,soil and sediment,endangering human health.Modified fly ash has a loose and porous structure and shows good adsorption performance for antibiotics and heavy metals,which can be used as a good adsorption material and also can reduce environmental pollution and achieve the purpose of"treating waste with waste".To investigate the effect of Cu²⁺stress modified fly ash on the removal of ciprofloxacin（CIP）.In this study,fly ash（FA）was used as the raw material and CIP was used as the target pollutant,and the conditions of fly ash modification were optimized by the response surface method（Box-Benhnken）to compare and analyze the effect of exogenous Cu²⁺on the adsorption characteristics of CIP;the modified fly ash（AFA）was used as the carrier and loaded with ZnO to prepare photocatalytic nanomaterials to investigate the photodegradation characteristics of ZnO-modified fly ash（ZFA）on The photocatalytic nanomaterials were prepared with modified fly ash（AFA）carrier loaded with ZnO to investigate the photodegradation characteristics of ZnO-modified fly ash（ZFA）on CIP.The main research results are as follows:Using the adsorption amount of CIP as the response value,the preparation conditions of AFA were optimized by the response surface optimization method,and the optimal modification parameters were obtained:the alkali-ash ratio of 1.5,the calcination temperature of 400℃,and the calcination time of 3 h.The adsorption amount of CIP was 19.33 mg·g^-1,which increased about 9.8 mg·g^-1 compared with that of FA.After the modification of fly ash,the surface is rough and loose,and the glass phase structure is destroyed,exposing the deep pore structure and increasing the specific surface area.The zero potential point of FA increased from 7.18 to 7.88 after Na OH modification.The adsorption process of FA and AFA on CIP was divided into fast adsorption phase,slow adsorption phase and adsorption equilibrium phase,and the equilibrium adsorption amounts were 9.51 and 19.14 mg·g^-1,respectively.The adsorption kinetics of CIP could be fitted by quasi-secondary kinetic equations.The adsorption of FA and AFA on CIP decreases with increasing temperature,and the adsorption isotherms can be fitted with the Langmuir equation.The adsorption thermodynamic parameters?G<0,?H<0,and?S>0 indicate that the adsorption is an exothermic reaction.In the p H range of the test（3-11）,the adsorption amount of CIP showed a trend of increasing and then decreasing with the increase of p H,and the adsorption amount reached the maximum when the p H was 6.In a complex contaminated system with exogenous Cu²⁺addition,the CIP adsorption characteristics were similar to those in the single contaminant system,but the adsorption equilibrium time was shortened and quasi-secondary kinetics fitted best for the adsorption kinetic behavior of both contaminants.The isothermal results of FA and AFA for the adsorption of CIP and Cu²⁺were more consistent with the Langmuir model.According to the distribution coefficient results showed that the competitive adsorption capacity of Cu²⁺was greater than that of CIP in the binary contamination system.ZFA,a nano-zinc oxide（ZnO）/AFA composite,was prepared by ultrasonic dispersion and high-temperature immobilization method.The adsorption characteristics of ZFA were similar to those of AFA under light and dark reaction conditions,and the adsorption reached21.7 mg·g^-1.The photodegradation reaction of ZFA on CIP was in accordance with the primary kinetics,and the degradation rate reached the maximum of 83.21%after 300 min of254 nm UV illumination.Comparing with 365 nm UV light and natural light,ZFA can break the chemical bonds such as C-O and C-H in CIP and some degradation products or intermediate products in solution under the excitation of 254 nm UV light irradiation.The photodegradation rate decreased as the initial concentration of CIP increased;the degradation rate of CIP was greatest under neutral conditions.The addition of exogenous Cu²⁺,the complex formed by Cu²⁺and CIP,increases the energy required to absorb photons to reach the excited state,which decreases the photodegradation rate,and the larger the concentration of Cu²⁺,the more obvious the inhibition.The burst test shows that·O₂^-and h⁺play a major role in the photodegradation of CIP,and the order of the three free radicals in the degradation process is·O₂^->h⁺>-OH.