Study On The Performance Of Biochar Adsorption Of Nano-Plastic And The Synergistic Removal Of Ammonia Nitrogen By Modified Bioretention Cell

While the widespread use of plastics has made life more convenient,it has also caused environmental contamination,particularly in the water environment,which is vital to life.Microplastics are created when plastics degrade in the environment and become a new pollutant in water bodies.While the study of microplastics has grown recently,that of nanoplastics is still in its early stages.In comparison to microplastics,which can easily adsorb other pollutants in the water environment and act as carriers to cause secondary pollution of the water environment,nanoplastics are smaller in size and have more complex physicochemical properties.They are also highly susceptible to penetrating biological cells with potentially irreversible effects on the organism and may be dangerous to human health.While biochar’s unique pore structure,high specific surface area,and high carbon content have the ability to effectively adsorb nano-plastics,conventional water treatment systems have several difficulties in the removal of these tiny plastic particles.Little research has been done on biochar’s ability to remove nanoscale plastic particles,but given their complementary adsorption capacities and characteristics,there may be a chance for co-adsorption of other contaminants.It is crucial to research the synergistic control of runoff pollutants in bioretention basins and the adsorption of nano-plastics by biochar.In this study,the adsorption of biochar on polystyrene nanoplastics（PSNPs）in aqueous solution was examined.Three varieties of biochar（WBC,YBC and GBC）were synthesised from sycamore bark,maize cobs,and coconut shell as biomass raw materials.Scanning electron microscopy（SEM）,elemental analysis energy spectrometry（EDS）,fourier transform infrared spectroscopy（FTIR）,X-ray diffraction（XRD）,and Zeta potential were used to investigate the mechanism of nano-plastic adsorption on biochar in conjunction with adsorption kinetic and isotherm models.Analyzed are the ways through which various external environmental elements affect sorption behaviour.The biochar material’s capacity to be reused was also examined.Finally,using NH₄⁺-N as the representative pollutant under test,the synergistic effect of biochar and nanoplastics on the removal of organic pollutants in bioretention cells was examined.The following are the main findings:Pyrolysis was used to create the biochar,which was then characterised both before and after adsorption tests.The biochar surface has a rich microporous structure,according to SEM measurements.It was more significant the higher the biomass cellulose content,and after adsorption PSNPs accumulated on the surface and in the pores.The size of the biochar’s specific surface area has no real bearing on adsorption;FTIR results show that biochar is rich in oxygen-containing functional groups like—OH and aromatic compounds,and that this aromatic structure enhances the adsorption of non-polar nanoplastics.Zeta potential analysis suggests that biochar is positively charged under strongly acidic conditions and negatively charged under both neutral and basic conditions,and that PSNPs are non-polar.XRD results show that biochar is stable with a turbo-layered graphite structure.Adsorption performance is shown to be in the order of WBC>YBC>GBC,with WBC having the highest adsorption to PSNPs in the environmental influence factor adsorption trials and cyclic adsorption experiments.Strong adsorption stability and recyclability are displayed by biochar.As the amount of biochar added grows,removal rate increases but adsorption capacity decreases;as the concentration of nano-plastics rises,adsorption capacity increases but removal rate decreases;adsorption is encouraged by weak acids and neutral conditions（pH=6～7）,with maximum adsorption;anions compete for adsorption sites,reducing removal,and trace levels of Cl^-encourage adsorption;organic matter has the potential to obstruct space,which would hinder the adsorption process.The proposed primary kinetic model correlation（R²>0.93）was greater than the proposed secondary kinetic model.The adsorption process is divided into two stages:rapid adsorption and slow adsorption,primarily surface adsorption,and dominated by physical adsorption.Adsorption kinetics and the intraparticle diffusion model experimentally show that internal diffusion is not the only step that limits the rate of adsorption.With maximum sorption quantities of 5.25 mg/g,4.54 mg/g,and 3.97mg/g for PSNPs,respectively,isotherm experiments showed that the Langmuir model（R²>0.95）suited the experimental data better than the Freundlich model,suggesting that the adsorption mechanism is mostly monomolecular layer adsorption.According to the biochar column model and effect factor tests,the main adsorption mechanisms include electrostatic,hydrophobic,physical retention,andπ-πEDA interactions.The removal efficiency of the system over vermiculite filler modified bioretention systems has been greatly improved by coexisting biochar and nano-plastics,according to bioretention cell studies.It also has some removal effect on PSNPs.It was also discovered that adding biochar filler made it easier to remove organic contaminants from runoff in bioretention basins.The study’s findings provide conclusive evidence that biochar is efficient at adsorbing and removing nano-plastics.