Analysis Of The Pyrolysis Stabilization Of Manganese Enriched Biomass And Its Adsorption Mechanism For Lead And Tetracycline

Heavy metals in manganese(Mn)mine will cause large-scale soil pollution.As an efficient and environmentally friendly soil remediation technology,phytoremediation can effectively improve the pollution of heavy metals in tailings.However,the treatment and disposal of a large number of heavy metals enriched plant biomass obtained after phytoremediation has become the key to the sustainable development of this technology.Pyrolysis can not only reduce the amount of plant residues,but also stabilize the heavy metals in biomass and avoid secondary pollution.Meanwhile,heavy metals and antibiotics pollution in the water environment is increasing,and the toxicity stabilization and mobility of the reaction complexes formed by the complexation of heavy metals and antibiotics will be further enhanced.The Mn enriched Phytolacca acinosa Roxb.biomass,is expected to convert into Mn enriched biochar without potential environmental risks,and can be applied to the removal of heavy metal and antibiotic,providing an effective solution for plant residues reutilization.In this study,Mn hyperaccumulator Phytolacca acinosa Roxb.biomass was chosen as the research object to prepare biochar with the best stability and without potential environmental risks to remove lead(Pb(II))and tetracycline(TC)in wastewater.Give full play to the production potential of Phytolacca acinosa Roxb.biomass to achieve the best benefits of reutilization and wastewater treatment.The main research contents and conclusions of this paper are as follows:The first prat measured the total content,chemical fractions distribution and leaching toxicity of heavy metals(Mn,Pb,Cr and Cd)in Phytolacca acinosa Roxb.biomass after Mn mine phytoremediation and biochar under different pyrolysis temperatures(300℃,450℃ and 600℃).The effect of pyrolysis temperature on the migration and transformation of heavy metals in Phytolacca acinosa Roxb.biomass and its potential environmental risks were explored.The results illuminated that high temperature pyrolysis can effectively realize the reduction the Phytolacca acinosa Roxb.biomass,and with the increase of pyrolysis temperature,the enrichment of heavy metals in biochar gradually increases.At the same time,the pyrolysis temperature can significantly affect the occurrence forms of heavy metals in Mn enriched biochar,and the increase of the pyrolysis temperature is helpful for the transformation of heavy metals into stable forms.Compared with Phytolacca acinosa Roxb.biomass,pyrolysis can effectively reduce the leaching toxicity of heavy metals,and the biochar(PSB450)pyrolyzed at 450℃ has the lowest potential environmental risks.Based on the stability of heavy metals and potential environmental risks,450℃ was used as the optimal pyrolysis temperature in the research on the reutilization of Phytolacca acinosa Roxb.biomass in the later stage.The second part,PSB450,which has the best stability,was applied to for reutilization.The removal efficiency and mechanism of PSB450 for Pb(Ⅱ)and TC sorption in the single/binary systems were explored.In the single system,with the increase of pH value,the removal efficacy of PSB450 for Pb(Ⅱ)and TC gradually increased,and their adsorption capacity can reach 198.35 mg/g and 14.51 mg/g,respectively at pH 6.The result of Zeta potential showed that the electrostatic interactions may exist between the Pb(Ⅱ)and PSB450,while hydrogen bond andπ-π interaction may be the main mechanisms of TC removal.The adsorption process of Pb(Ⅱ)and TC by PSB450 were consistent with the pseudo second-order kinetic model,indicating that the adsorption behavior was closer to the autonomous exothermic process dominated by chemical adsorption.The key rate-controlling step was membrane diffusion by fitting the intraparticle diffusion model and film diffusion model in the adsorption process.Meanwhile,the adsorption of Pb(Ⅱ)and TC by PSB450 conforms to the Langmuir isotherm model,indicating that the adsorption behavior is dominated by monolayer adsorption,and the maximum adsorption capacities of Pb(Ⅱ)and TC by PSB450 can reach 279.33 mg/g and 47.51 mg/g,respectively.In the binary system,there existed sorption enhancement and site competition which were concentration-dependent.Lower coexisting concentrations of TC which can promote the removal of Pb(Ⅱ)by forming ternary complexes(PSB450-Pb(Ⅱ)-TC0)with Pb(Ⅱ)and PSB450,while higher concentrations of Pb(Ⅱ)can form the complex with TC(MeTC0),or would serve as a bridge between PSB450 and TC by complexation,thus facilitating the removal effect of TC.The third part,the non-pollution pristine phytolaccaceae biomass was applied to prepare the biochar(PPSB450)under the same pyrolysis conditions,and the adsorption efficiencies of PSB450 and PPSB450 on Pb(Ⅱ)and TC were compared.The effect of Mn-rich properties of PSB450 on its adsorption properties was investigated by combined with SEM,XRD,FTIR and XPS characterization methods.Results illustrated that,compared with PPSB450,PSB450 exhibited better removal efficiency in the single or binary systems.The characterization results also indicated that Mn in biomass could convert to the Mn oxides(Mn2O3 and MnO2)and Mn minerals(MnSiO3 and Mn2P2O7)on the surface of PSB450 after pyrolysis.After the binary adsorption of Pb(Ⅱ)and TC,Mn2O3 on the surface of PSB450 was converted into MnO2,indicating that MnOx could effectively promote the synergistic sorption of Pb(Ⅱ)and TC on PSB450.This study provided a win-win approach for reutilization of heavy metals contaminated biomass after phytoremediation and the treatment of heavy metal and antibiotic contamination in wastewater.