Preparation Of Nano FeS And Its Treatment Of Acidic Chromium Containing Wastewater

Considering the toxicity and difficulty of treating acidic chromium-containing wastewater,nano FeS were prepared by ultrasonic chemical precipitation and Sulfate Reducing Bacteria?SRB?biological methods,and experiments were carried out to treat acidic chromium-containing wastewater.The optimal reaction conditions for preparing nano FeS by ultrasonic precipitation were studied by single factor experiment.The removal effects of nano FeS on Cr?VI?were compared under different reaction conditions,such as mixed droplet flow rate,ultrasonic treatment time,ultrasonic treatment frequency,iron source,Fe/S molar ratio,pH value and temperature.The results showed that the most influential reaction conditions are mixed droplet flow rate,Fe/S molar ratio and temperature.Response surface experiments were carried out with the above three reaction conditions as the influencing factors.The study showed that the optimal reaction conditions for preparing nano FeS by ultrasonic precipitation method are as follows:mixed drip velocity is 0.50 mL/s,Fe/S molar ratio is 3.5,and temperature is 12?.The optimum reaction conditions for preparing nano FeS by SRB biological method were studied by single factor experiment.The production of nano FeS and the removal effect of Cr?VI?were compared under different reaction conditions,such as N/C molar ratio,temperature,dosage of Fe source,pH value,type of nitrogen source and S/Fe molar ratio.The results showed that the most influential reaction conditions are the molar ratio of N/C,the dosage of Fe source and the pH value.Response surface experiments were carried out with the above three reaction conditions as the influencing factors.The study showed that the optimal reaction conditions for the preparation of nano FeS by SRB biological method are as follows:N/C molar ratio is 1.9,Fe source dosage is 6.30g/L and pH value is 7.50.The analysis showed that the nano FeS prepared by ultrasonic method and biological method are needle-like and whisker-like,by X-ray diffraction?XRD?and transmission electron microscope?TEM?and scanning electron microscope?SEM?.And the Cr???and total chromium removal process are consistent with the first-order reaction kinetics model.BET-N₂ analysis showed that the adsorption process of nano FeS prepared by ultrasonic method and biological method are all type III adsorption isotherms,which are in good agreement with Freundlich model.Their specific surface area and average pore size are 4.1445 m2/g and 4.1692 m2/g,0.0183 cm³/g and 0.0141 cm³/g,respectively.The 1#,2#,3#,4#dynamic column experimental model of two kinds of nano FeS and its immobilized particles were respectively constructed.The effects of nano FeS on the treatment of acidic Cr?VI?containing wastewater under different reaction conditions were studied.The results showed that the effluent pH values of the four dynamic columns were all neutral,the average removal rates of Cr?VI?and total chromium by 1#columns and 2#columns were 99.67%,97.74%,94.93%and 92.34%,respectively,which were higher than those of 3#column and 4#column,that average removal rate were 81.29%,74.09%and 45.76%,34.58%.The average releases of COD and TFe in the effluents of 1#and 2#columns were 18.44mg/L,31.44mg/L and1.22mg/L,1.28mg/L,respectively,which were lower than those of 3#column and 4#column,that average release of TFe were 994.19 mg/L,1069.19 mg/L,and 3.25 mg/L,4.15 mg/L.However,the effluent average turbidities of 1#column and 2#column were 26.96 NTU and25.96 NTU,respectively,which were higher than the average turbidities of 0.68 NTU and 0.76NTU in the effluent of 3#column and 4#column.In conclusion,the removal effect of Cr?VI?by nano FeS prepared by ultrasonic precipitation is better than that by immobilized particles and SRB biological method.This paper contains 46 figures,19 tables and 107 references.