| Recently,metallic chromium and its compounds have been widely used in various fields of industrial production such as electroplating,metal processing,leather making,paints,pigments,printing and dyeing.The ensuing chrome pollution problem has attracted more and more attention from scholars all around the world.Therefore,finding an efficient and environmentally method for treating Cr???pollution is an important issue.Based on this,this study prepared biochar and modified it by using corn stalks.The single-factor method was used to optimize the modification conditions,and a kind of biochar with good adsorption capacity for Cr???was obtained.The reaction conditions were optimized,the adsorption reaction model was fitted,and the morphological structure and chemical composition of the modified biochar were combined to explore the adsorption mechanism of Cr???.At the same time,the isolation Acinetobacter Baumannii AL-6 from the research group with heterotrophic nitrification-aerobic denitrification performance was studied at different Cr???concentrations.Denitrification performance and the removal performance of Cr???under different initial ammonia nitrogen concentrations,and the possible reaction mechanism was analyzed.Finally,in order to explorethe interactions between biochar and miCrobes affect their ability to remove Cr???,a biochar-bacteria coexisting system was constructed.The main conclusions are as follows:?1?The biochar is prepared by corn stover under the condition of pyrolysis,zinc chloride and ferric chloride are added for amendment.By optimizing the secondary calcination temperature,the addition of zinc chloride and ferric chloride to carbon,the optimal conditions for the amendment of biochar were obtained.The optimal conditions were:the secondary calcination temperature is 400°C.the percentage of ferric chloride added is 0.5,and the proportion of zinc chloride is 0.3.Underneath this condition of modification,While the adsorption capacity of magnetic biochar on Cr???is 6.8,4.5and 2.7 times higher than the adsorption capacity of raw biochar,iron modified biochar and zinc modified biochar,respectively,15 min after adsorption process.?2?The adsorption capacity of composite modified biochar for Cr???inCreased with the inCreasing of Cr???concentration and the contacting of time.Composite modified biochar has good adsorption efficiency for Cr???,and it essentially reaches adsorption equilibrium in 1h.Under the light situation,the elimination rate of Cr???is 10%higher than that reaction in dark circumstance within the adsorption procedure at5 min,which proved the removal of Cr???by the introduction of a photocatalyst within the preparation of Composite modified biochar.It has promoted the improving of elimination efficiency.At the same time,the adsorption reaction of composite modified biochar on Cr???is an endothermic reaction,and the growth of ambient temperature promotes the adsorption reaction.After modification,the composite modified biochar is in particular chemisorbed in the adsorption of Cr???.The purposeful corporations consisting of hydroxyl,carbonyl,and carboxyl groups are involved within the adsorption process.In addition,Fe3O4,ZnFe2O4,and other substances were formed during the preparation of biochar.After the adsorption process,multiple chromium peaks appeared at 35.5o,43.1o and 62.6o.After the phase retrieval,these peaks corresponded to ZnFeCrO4 and FeCr2O4 respectively.It is shown that Cr?VI?in the solution is reduced to Cr?III?by the action of a reducing substance.?3?The A.baumannii AL-6 has no significant difference in heterotrophic nitrification-aerobic denitrification performance at different initial concentrations of Cr???,but has a certain influence on its growth rate.Under the optimal temperature and pH conditions,when the initial ammonia nitrogen concentration was 100-500 mg/L,the removal rates of Cr???were 68%,64%,66%,58%,19%respectively.The removal effect of AL-6 on Cr???was affected by the growth of bacteria.When the concentration of ammonia nitrogen was 100mg/L,the growth of bacteria was the better than the others and show the best removal effect of Cr???.By measuring the total chromium and Cr???of the used culture supernatant,it was confirmed that Cr?III?was contained in the supernatant,which proved that AL-6 had a certain reduction effect on Cr???.?4?The composite modified biochar optimized under orthogonal conditions and the acclimated strain Acinetobacter AL-6 were used to remove Cr???from wastewater.The experimental results show that the combined application of composite modified biochar and AL-6 bacteria has a certain treatment effect on Cr???,and the removal of Cr???in solution by the coexistence system of carbon-bacteria reaches equilibrium at 84h.The removal rates of Cr???in solution at concentrations of 3 mg/L,5 mg/L,7mg/L and 10 mg/L were 66.3%,50.24%,49.1%,and 22.7%,respectively.The results showed that the coexistence system of carbon-bacteria has a good effect on the removal of chromium-containing wastewater under low concentration conditions.This inquiry provides a certain reference for the future removal of pollutants from biochar and miCroorganisms. |
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