Rapid And Selective Removal Of Copper And Antimony By Manganese Oxide Impregnated Onto A Biochar With Enlarged Pore Structure

Heavy metal pollution in water has become a global environmental problem,and its in-depth treatment is an important guarantee for water quality safety control.This paper in view of the heavy metals deep purification manganese oxide powder state within the territory of the solid-liquid separation difficulties of engineering application,and the technical bottleneck,with big head loss choose macroporous biochar with special pore structure as the carrier,using"precursor implanted in situ settlement technology"successfully developed a macroporous biochar-manganese oxide composite adsorbent,its typical ionic contaminants in water system studied Sb???,Cu???adsorption performance,and to reveal the potential adsorption mechanism;On this basis,the application potential of composite adsorbent in antimony/copper wastewater purification is evaluated,so as to provide theoretical basis and technical support for antimony and copper pollution purification.In this paper,macroporous biochar was firstly obtained by the pyrolysis of KHCO₃with the technique of pore reamer,and then the macroporous biochar-oxide composite adsorbent?MO-L-BC?was prepared by the in situ precipitation method.The adsorption behavior of the synthesized MO-L-BC to Sb???and Cu???was studied from the aspects of dynamics,isotherm,p H effect and competitive effect.The results showed that the prepared mo-l-bc had a strong targeting adsorption ability to Sb???and Cu???in water.Since l-bc has a high proportion of large pores?>2 nm??87%?,which reduces the diffusion resistance of target pollutants in the pore area of MO-L-BC,the adsorption of Sb???and Cu???on MO-L-BC reaches an equilibrium within 15min.The maximum adsorption capacity of Sb???and Cu???by MO-L-BC can reach248 mg g^-1and 126 mg g^-1respectively.The adsorption of MO-L-BC on the target pollutant is in good agreement with the in-particle diffusion?IPD?model and the fekker's second law model as well as the Freundlich isothermal model.The effective coefficients of their in-particle diffusion?D?are 8.6x10^-8and 1.5x10^-7cm²s^-1respectively,which are only one order of magnitude lower than the aqueous p Hase.Even under the coexistence of competing ions such as the interfering components Ca???,Mg???,SO₄^2-,NO₃^-,HCO₃^-and HA in high concentration,MO-L-BC still showed a strong adsorption selectivity for the target pollutant,among which HA of 25 mg L^-1only reduced the adsorption capacity of Cu???and Sb???on MO-L-BC by 20%and 23%respectively.By means of experimental verification,FTIR and XPS spectroscopy,the potential adsorption mechanism of biological carbon-based manganese oxide composites was preliminarily revealed.The results showed that the large pore volume ratio of L-BC?>2 nm?was almost twice that of BC due to the pyrolysis of KHCO₃.After the digestion of MO-L-BC,the content of Mn is 7.9mg g^-1.Most of the embedded MO particles are nano-like and composed of three valence states,namely Mn???,Mn???and Mn?IV?.For Cu???adsorption,due to take off the proton process,increase the p H of the solution will strengthen the surface of the MO-L-BC electronegativity,leading to Cu???adsorption quantity increases gradually,and Sb???mainly for Sb?OH?₂⁺,neutral Sb?OH?₃and electronegativity Sb?OH?^4-exists in the form of strong acid and weak acid and neutral p H and alkaline p H range,with the increase of p H,proton process in acidic p H range promotes positive Sb?OH?₂⁺adsorption,and in alkaline p H range inhibits negative Sb?OH?₄^-adsorption;The strong adsorption selectivity of MO-L-BC on the target pollutant is derived from the intergranular complexation between the embedded manganese oxide and the target heavy metal,which can significantly increase the concentration of the target pollutant in the solid p Hase region and increase the adsorption capacity.XPS analysis showed that the adsorption of Sb???by MO-L-BC was completed in two steps:Sb???was firstly adsorbed,then part of the adsorption Sb???was oxidized to Sb?V?,and Mn?IV?was reduced to generate Mn???,but the generated Mn???could be re-adsorbed to MO-L-BC through the interaction of surface complexes.In terms of practical application,for Sb???and Cu???coexistence system,Sb???increased from 0 to 50 mg L^-1,which only reduced the adsorption capacity of MO-L-BC to Cu???by 20%.Using fixed bed adsorption-stripping experiment to evaluate the biological carbon manganese oxide composite material purifying pollutants practical application potential,the results show that MO-L-BC can not only successfully applied in a fixed bed adsorption system,and can realize the depth of the simulated wastewater purification,MO-L-BC can implement the tertiary flow rate is as high as 0.27 mh^-1single pollutant?Sb???or Cu????or total waste water pollution,its thousands of times their own weight can be reduced to the corresponding target of metal concentration in the wastewater of wastewater under the control standard,even drinking water under the maximum residual standard.In addition,the column adsorbed saturated MO-L-BC can be regenerated stably in situ with a small amount of acid-salt mixed solution,and the results show that the carbon-based manganese oxide nanocomposite has a very broad application prospect in the field of heavy metal purification in water,especially in depth purification.