Characterization And Analysis Of Magnetic Biochar And Its Adsorption Performance On Microplastics In Water

In recent years,the resource utilization of biomass waste in various industries has received extensive attention from scientists.The modification of biomass waste to prepare adsorbents for wastewater treatment has been widely applied due to its high processing efficiency and environmental friendliness.Microplastics(MPs)is a new type of pollutant in water environments,characterized by small particle size(< 5 mm)and difficulty in degradation,making them challenging to remove from water environments.MPs can cause serious harm to ecological environments and human health.Therefore,the removal of MPs from water environments has become a hot issue in environmental research.In this study,rice straw and corn straw biomass were used as raw materials to prepare two types of magnetic biochar,including rice straw magnetic biochar(MRB)and corn straw magnetic biochar(MCB/MCB-Ni),for the removal of MPs in wastewater.Firstly,characterization and analysis were conducted on the prepared biochar materials,mainly including: apparent morphology,surface functional groups,and specific surface area.Secondly,biochar was applied for the adsorption and removal of MPs in wastewater,and the changes in the adsorption performance of the adsorbent under different environmental factors were investigated.The regeneration and tests of the adsorbent were also carried out to evaluate the reusability of the adsorbent.Finally,the reaction kinetics of the biochar adsorbent for the adsorption of waterborne MPs were explored,and the adsorption mechanism was investigated in depth by fitting the adsorption isotherms and thermodynamic equations,2D-COS spectra,etc.The main contents and conclusions of the study are as follows:1.Modified biochar(MRB)was prepared from rice straw and characterized by the production of abundant pore structures after pyrolysis.The presence of Fe-O bond stretching vibrations and characteristic peaks in XRD indicated that the surface of MRB was covered with unevenly distributed,granular mineral particles of iron oxide.Following the adsorption of microplastics(MPs),the MRB surface was heavily loaded with uniform,spherical particles through electrostatic attraction,surface complexation,and π-π interactions.Adsorption reaction occurred spontaneously and was facilitated at higher temperatures.Adsorption performance testing revealed that anions had a greater influence on the adsorption reaction,and different concentrations exhibited different degrees of adsorption.MRB after adsorption of MPs could be recycled through heat treatment,with the MRB used four times still able to remove 90% of the MPs.2.Mono-metal(Fe)-modified biochar(MCB)and bimetallic(Fe/Ni)-modified biochar(MCB-Ni)were prepared using corn straw as a raw material.Characterization results confirmed the accumulation of a large number of Fe and Fe/Ni particles,and the increase in surface C and O content of the adsorbent indicated the successful fixation of MPs on the adsorbent.The changes in the concentration of MPs in the aqueous solution over time and the release of metal particles from the adsorbent did not significantly lead to the aggregation of MPs,and the released metal particles did not exceed the metal limit in drinking water.The differences in properties between MCB and MCB-Ni were small,but each exhibited its own advantages.MCB had good repeatability and use performance,but its anti-interference ability and stability were relatively poor.Both materials overall show effective adsorption of MPs.3.A comparative analysis was conducted on the material properties of rice and corn straw biochar(RB/CB)and modified rice and corn straw biochar(MRB/MCB),revealing that RB had a larger specific surface area and a more abundant pore structure than CB.MRB also loaded more magnetic material than MCB,but MCB was more stable with a mass loss of only ≤ 2%.Differences in adsorption pserformance indicated that MCB and MRB showed superior adsorption at low p H,with no significant difference between the two.Reusability studies showed that MRB maintained strong adsorption capability even after four uses,while MCB’s adsorption performance significantly decreased.Therefore,MRB adsorbent was more stable and suitable for multiple modification studies.