Research On Adsorption Properties Of Ferromanganese Oxide-biochar Composites For Heavy Metals

Heavy metals?HMs?pose a serious threat to human health and environment,thus there is an urgent need to find an effective way to remove them.Biochar?BC?is a kind of“green”and low-cost porous adsorbent.In recent years,due to its distinctive elemental composition,surface physicochemical properties and pore structure,it has received extensive attention.However,the application of BC in the field of wastewater treatment is limited,such as insufficient adsorption efficiency,difficulty in recovery and recycling.Therefore,in response to these problems,the ferromanganese oxide is used to modify teawaste biochar to prepare composite materials,so that the technical advantages of the two are complementary,and research on strengthening biochar's removal efficiency of HMs and corresponding mechanism are carried out.The optimum preparation conditions of the composites were preliminarily investigated by the yield,material ratio and pyrolysis final temperature.The structural characteristics and corresponding mechanisms of BC to remove HMs by means of various characterization methods.The results showed that 0.5 is the best iron-manganese modification ratio.The increase of the final temperature of pyrolysis led to changes in the surface properties of biochar.the pore structure of biochar changed,the hydrophilic properties of the material decrease,the aromaticity and the content of inorganic mineral increases and the surface acidic functional group was also reduced with the increase of cracking temperature.The modification of ferromanganese oxide introduced Fe-O and Mn-O characteristic functional groups on the surface of biochar,and the deposition of iron-manganese particles led to a decrease of the XRD peak intensity of the composite..The study also probed the effects of environmental factors,removal time and other parameters,we compared the removal effect of activated carbon,and combined with kinetic and thermodynamic model,revealing the potential application and mechanism of composite materials for strengthening single heavy metal removal in water.The results showed that the pH is 5 and the dosage is 1.5 g/L were the best condition;Compared to the original biochar,the composites showed good removal effects on single Pb²⁺and Cd²⁺,and the removal ratio of Cu²⁺by BC300Fe₁Mn₂ was also significantly improved.Kinetic fit results indicate the adsorption process of BCFe₁Mn₂ on single Pb²⁺,Cd²⁺and Zn²⁺mainly included chemical bonds and shared electrons,while the adsorption of single Cu²⁺was more suitable for simple diffusion and electrostatic interaction.The results of thermodynamic fitting showed that the adsorption and removal process of BCFe₁Mn₂ on single Pb²⁺,Cu²⁺,Cd²⁺and Zn²⁺were homogeneous surface adsorption process.By exploring the removal effect and application conditions of BC300Fe₁Mn₂ on mixed HMs,the effect of other metal ions on the removal of HMs in composites and the corresponding mechanism,and the feasibility of using composite materials for the treatment of simulated wastewater of lead-zinc smelting.The results showed that the increase of pH was beneficial to the removal of Pb²⁺ions.In the presence of other metal ions,the adsorption capacity of BC300Fe₁Mn₂ to Pb²⁺increased with the increase of Pb²⁺concentration.When Cu²⁺,Cd²⁺and Zn²⁺were the main research objects,the adsorption capacity of BC300Fe₁Mn₂ for Cu²⁺,Cd²⁺and Zn²⁺increased first and then decreased slightly,and increased again.After treatment with BC300Fe₁Mn₂,the concentration of Pb²⁺,Cu²⁺and pH value of the HMs-containing acidic wastewater discharged from the lead-zinc industry could reach the emission standard,and Cd²⁺basically reached the emission standard.