Study On The Reduction Of Cr(Ⅵ) By Phenol Group Synergistic With Shewanella In Bagasse

In recent decades,China’s economy and industrialization have developed rapidly,but with it,the destruction of the ecological environment,especially the heavy metal chromium pollution has seriously threatened the national health.In order to build a modern socialist country in which man and nature live in harmony,it is urgent to solve chromium pollution in the water environment.In this paper,we selected the agricultural waste bagasse and dissipatifying metal reducing microorganism Shewanella to explore the reduction ability and reduction mechanism of bagasse lignin phenol-based synergistic Shewanella on Cr(Ⅵ)under different influencing factors.The main contents and conclusions are as follows:Through single factor optimization experiments,it was found that the introduction of bagasse,it was found that the introduction of bagasse could effectively enhance the reduction effect of MR-1 on Cr(Ⅵ).However,the activity of bacteria is easily affected by different temperature,pH and Cr(Ⅵ)concentration,which affects the utilization rate of MR-1 to bagasse.Under the conditions of optimal temperature,pH and Cr(Ⅵ)concentration,that is,temperature 35 °C,pH 7,and initial concentration of Cr(Ⅵ)of 20 mg/L,the reduction ability of bagasse + sodium lactate+ MR-1 for 20 mg/L Cr(Ⅵ)within 3 days was close to 90%,which greatly exceeded the poor reduction ability(only 31.6%)without bagasse.In addition,different metal ions also have a significant impact on the removal effect,calcium ions can enhance the removal effect,while cadmium ions significantly inhibit the removal of Cr(Ⅵ).Through the response surface optimization method(RSM)reduction condition optimization experimental method,taking the bagasse dosage,incubation time and incubation temperature as independent variables,and using the reduction rate of sugarcanace + sodium lactate + MR-1 system on Cr(Ⅵ)in water as the response value,the three-factor and three-level orthogonal experiments were designed,and the optimal experimental conditions for removing Cr(Ⅵ)from sugarbagasse + sodium lactate + MR-1 could be obtained: the dosage of bagasse was 1.78 g,the incubation temperature was 38.59 °C,and the incubation time was 3.21 d.The predicted value of bagasse + MR-1 on Cr(Ⅵ)removal rate under this condition was 98.84%,which was very close to the actual measured Cr(Ⅵ)removal rate of 97.80%.The mechanism of reduction of Cr(Ⅵ) by Bagasse by Shewanella using bagasse was analyzed by three-dimensional fluorescence,ultraviolet-visible spectroscopy and other detection methods.The extracellular polymer secreted by MR-1 is composed of tyrosine,tryptophan and protein-like substances,and its components are mainly oxygen-containing functional groups such as hydroxyl,amino and phosphorus-oxygen double bonds,which can not only adsorb chromium ions on the bacteria through ion exchange,but also why MR-1 is able to restore Cr(Ⅵ).In addition,the lignin phenol group contained in bagasse is also involved in MR-1reduction process to Cr(Ⅵ).Based on this,it is speculated that the four phenolic hydroxyl groups with strong reducing properties in bagasse lignin are in Under the stimulation of the weak current generated by MR-1 on Cr(Ⅵ),part of Cr(Ⅵ)can be reduced,and its reduction product is quinone,and the quinone substance is again received from the electron of MR-1 can then be reduced to new Cr(Ⅵ),so the cycle further improves the reduction efficiency.This paper provides a possible principle analysis for the reduction of Cr(Ⅵ)by phenol based synergy with Shewanella in bagasse.