Study On The Adsorption Performance Of Magnetically Modified Biochar On Polystyrene Microplastics In Wate

Microplastics have attracted worldwide attention due to their high abundance,easy migration,and potential threats to human health.How to remove microplastics from water is the current research focus.Currently,using biochar to adsorb and remove microplastics from water is considered a promising technology.Due to the relatively limited adsorption capacity of pristine biochar for microplastics,modification treatment is needed to improve its adsorption performance.Most of the current modification methods use chemical reagents for modification,which is cumbersome and may cause secondary pollution to the environment.Therefore,in response to the above problems,this study uses biomass（distillers grains,corn stalks,and sawdust）and modifier（hematite and zinc chloride）to prepare magnetically modified biochar under different temperatures（300,450,and 600℃）for the removal of polystyrene microplastics（PS,1μm）from water.The effects of different influencing factors on the adsorption of PS by magnetically modified distillers grains biochar（MJBC）,magnetically modified corn stalk biochar（MYBC）,and magnetically modified sawdust biochar（MMBC）were investigated.The main adsorption mechanisms were analyzed using SEM,FTIR,XRD,and Zeta potential characterization methods and adsorption models,and their adsorption performance for PS in actual water was explored.On this basis,the economic benefits and practical application potential of MJBC,MYBC,and MMBC were evaluated through dynamic adsorption,cyclic regeneration,risk assessment experiments,and cost accounting.The main results are as follows:（1）The characterization results of the pristine and magnetically modified biochar showed that the specific surface area and total pore volume of the pristine and magnetically modified biochar gradually increased as the pyrolysis temperature increased.Compared to the pristine biochar,the surface of magnetically modified biochar became rough and Fe-O and Zn-O bonds,as well as metal oxides such as Fe₃O₄and Zn O were detected,indicating that the modified substance has been successfully loaded onto the biochar.（2）The experimental research results of influencing factors indicated that the solution p H affected the adsorption performance of magnetically modified biochar on PS,and the most suitable solution p H for PS adsorption was 7.0.When the pyrolysis temperature was 600℃and the mass ratio of biomass:hematite:zinc chloride was 1:1:1,the adsorption performance was the best,with a removal rate of 61.74%.Humic acid and CO₃^2-could inhibit the adsorption of PS.Combining characterization methods such as SEM,FTIR,XRD,BET,and Zeta potential,as well as different adsorption models,the main adsorption mechanisms of magnetically modified biochar for PS were metal bonding,pore filling,and electrostatic attraction.（3）According to Langmuir model fitting,the maximum adsorption capacities of MJBC,MYBC,and MMBC for PS were 99.07,115.08,and 123.86 mg/g,respectively.Thermodynamic experiments showed that the adsorption process of PS by MJBC,MYBC,and MMBC was a spontaneous exothermic process.（4）The results of dynamic adsorption experiments showed that the concentration of PS,the dosage of adsorbent,and the flow rate affected the removal efficiency of PS by the adsorption column.Its adsorption performance increased with the increase of dosage,and decreased with the increase of initial concentration and flow rate.When the amount of MMBC added was 0.20 g,the concentration of PS was 20 mg/L,and the flow rate was 5 m L/min,the dynamic adsorption performance of the dynamic adsorption column for PS was better,with a removal rate of 65%.The adsorption performance of magnetically modified biochar on PS gradually decreased with the increase of its cycle usage.After five cycles,magnetically modified biochar still had a removal efficiency of 20%.