Study On The Treatment Of Cr(?) And Mn(?) In Electrolytic Manganese Wastewater By Microbial Fuel Cell(MFC)Combined With Activated Carbon Derived From Waste-Areca(ACWA)

There are abundant manganese resources in Western Hunan Province,and Huayuan County is known as the"manganese capital"in the world.Every year,a large amount of Electrolytic manganese waste water is produced in Electrolytic manganese enterprises,which seriously pollutes the ecological environment.Among them,the main pollution ions are Cr?VI?and Mn?II?.Although there are many methods to deal with Cr?VI?or Mn?II?,there is no efficient process to deal with Cr?VI?and Mn?II?at the same time.Therefore,the development of a process that can simultaneously and efficiently treat Cr?VI?and Mn?II?has obvious theoretical and practical significance for the efficient removal of Cr?VI?and Mn?II?in the waste water of electrolytic manganese and the ecological restoration of polluted water.Based on the advantages of microbial fuel cell?MFC?technology and sintered carbon in waste water treatment,especially in the treatment of the waste water with heavy metal ions of high valence,and the adsorption effect of biochar on heavy metal ions.This paper proposes a combined method of microbial fuel cell?MFC?-sintered carbon derived from waste-areca?ACWA?to simultaneously remove Cr?VI?and Mn?II?from the waste water of electrolytic manganese.The main research contents are as follows:In this paper,a two-chamber microbial fuel cell?MFC?was constructed by using F026 strain as an anodic electrobacteria and simulated electrolytic manganese waste water containing Cr?VI?as cathode solution.We carried out three experiments to treat the simulated electrolytic manganese?Mn?waste water by MFC.The removal rate of Cr?VI?and the electrolytic performance of MFC were studied under different reaction conditions(p H of simulated electrolytic manganese waste water,initial concentration of Cr?VI?,working temperature of MFC,etc.By investigating the effect of MFC on the treatment of electrolytic manganese waste water,the optimum reaction conditions were summarized.The results showed that when the p H value of the reaction condition was2,the initial mass concentration of Cr?VI?is 60 mg/L,and the operating temperature of MFC was 30?.This condition,the removal rate of Cr?VI?in simulated waste water containing Cr?VI?by MFC operation for 52 h and 56 h can reach 99.2%and 100%.ACWA was prepared by carbonization of areca nut residue?WA?in argon atmosphere at 450?for 45 min.The carbon was characterized by X-ray diffraction,scanning electron microscopy,iodine adsorption value determination and specific surface measurement.The results showed that the sintered carbon was porous with an average pore size of 4.25 nm,and its specific surface area and iodine adsorption value were 742.53 g/m² and 1241.82 mg/g,respectively.Then,the adsorption of Mn?II?in simulated waste water was studied by using ACWA as adsorbent.The effects of ACWA waste water on the adsorption of Mn?II?were investigated.The adsorption isotherm and kinetics of ACWA were also investigated.The results showed that ACWA was well done for the adsorption capacity of Mn?II?.The maximum adsorption capacity of Mn?II?waste water with 180 mg/L concentration can be 34.28 mg/g within 60 min,and the adsorption rate of Mn?II?was 95.2%.Thermodynamic and kinetic studies showed that the adsorption isotherm equation of Mn?II?by ACWA can be described by Langmuir adsorption isotherm equation,and the adsorption kinetics coincides with quasi-second-order kinetics model.The mechanism study showed that ACWA can effectively remove Mn?II?from waste water by chemical complexation and electrostatic adsorption because of the abundant negative functional groups on the surface.Based on the research conclusion of waste water treatment by MFC and ACWA,this paper constructs the MFC-ACWA combined method.Under the optimal reaction conditions,the feasibility of the combined method was preliminarily verified by the treatment of simulated electrolytic manganese waste water,which was contained both Cr?VI?and Mn?II?.First,the actual electrolytic manganese waste water was treated.Second,the removal effect of the combined method for Cr?VI?and Mn?II?was examined.Third,the power generation of MFC was tested.Last,we also investigated the resulting products of these processing.The results showed that under the optimum conditions,the removal rate of Cr?VI?and Mn?II?was 92.1%after 80 hours of treatment of actual electrolytic manganese waste water with mass concentration of 124mg/L and 48 mg/L,respectively,and reduced to a-Cr₂O₃ with lower toxicity.After 155hours treatment,the removal rate was up to 100%,the power of electricity generation was up to 914.7 m W/cm²,and the removal rate of manganese ion Mn?II?in waste water was up to 93.76%,the concentration of Mn?II?ion in the solution was reduced to 2.99mg/L,which met the secondary standard of the comprehensive waste water discharge standard?GB8978-1996??no more than 5 mg/L?.The comprehensive results showed that microbial fuel cell-sintered carbon combined method is a promising treatment process for electrolytic manganese waste water containing Cr?VI?and Mn?II?,with simple process,high efficiency,low cost and other characteristics.