| As the industrial waste,steel slag is in great amount of production;the steel slag is used as the absorbent in this subject so as to achieve the“using waste to treat waste”and to repair the arsenic contamination of water;at the same time of reusing the steel slag,the new microbial modification mean shall also be used to improve the absorption performance of the steel slag.Firstly,the arsenic removal performance of the original steel slag shall be researched,and the steel slag composition is combined with the selected microorganism–the metabolic mechanism of iron-oxidizing bacteria to prepare the modified steel slag with iron-oxidizing bacteria;and the research of adsorption isotherm,absorption kinetics and influence factors is also carried out on the modified steel slag;the results indicates that the absorption performance of the modified material can be improved.Material characterization methods such as the X-ray fluorescent?XRF?,X-ray diffraction?XRD?,Fourier transform infrared spectroscopy?FTIR?and scanning electron microscope?SEM?,etc.are used to analyze the materials before and after modification,and to discuss the arsenic removal mechanism.The detailed research conclusion is as follows:?1?The iron-oxidizing bacteria shall obtain the energy required by its growth during the process of Fe?II?oxidized into Fe?III?,and this process may occur in the surface of the metal,which can change the physical and chemical property of the metal.According to the analysis with the combination of steel slag composition,the iron element in the form of Fe?II?exists in the steel slag,according to which we can judge that the metabolic mechanism of iron-oxidizing bacteria can be used to modify the steel slag;the Fe?II?can be oxidized into Fe?III?and the content of Fe?III?can be increased,thus the arsenic absorption performance can be improved.According to the modification result,compared with the original material,the absorbing capacity of steel slag which has been modified for 3 months on As?III?and As?V?has been increased by 378.2?g/g and 506.2?g/g separately.?2?According to the isothermal adsorption fitting of Langmuir model and Freundlich model,the fitting effect of Langmuir model on the original steel slag and the modified steel slag in arsenic adsorption is better.The maximum absorption amount of modified steel slag on As?III?and As?V?is 2500.00?g/g and 3333.33?g/g separately based on the Langmuir adsorption model fitting,which has been increased by 1071.43?g/g and 1333.33?g/g separately by comparing to the original steel slag.?3?The kinetic research of arsenic removal of original steel slag and modified steel slag is subject to the Lagergren quasi-first adsorption kinetic equation,Lagergren quasi-second adsorption kinetic equation and amendment Elovich equation,particle in-diffusion equation for fitting analysis;according to such analysis,the Lagergren quasi-second adsorption kinetic equation can describe the As?III?and As?V?removal process of steel slag better,which means that the arsenic removal by steel slag from the water mainly be achieved through chemical absorption.?4?According to the research on influence factors of original steel slag and modified steel slag on arsenic removal,in case of neutral pH conditions,the absorption quantity of original steel slag on arsenic is the largest,however,the optimum pH for modified steel slag in arsenic removal is 6;with the increase of temperature,the removal effect of steel slag is also improved,but the increase is small;the dosage is in positive correlation to the absorption quantity of steel slag,and with the increase of dosage,the speed increase of absorption quantity of the steel slag slows down;the positive ion in the liquid can assist the arsenic removal of steel slag,but the negative ion is of obvious inhibiting effect on the arsenic removal of steel slag.?5?According to XRF analysis,the Ca and Fe contents in modified steel slag are decreased slightly,and the loss on ignition is increased to 11.936%from zero;according to the XRD and FTIR analysis,the Ca?OH?2 content in modified material is decreased,and few Fe?III?occurs,the water hydroxy content is increased;the SEM and BET indicate that the pore of midwifed steel slag is increased,and it is40.1454m2/g larger than the original steel slag in specific surface area,and the pore volume is increased to 5 times larger than the original.?6?The main absorption mechanism of steel slag in arsenic removal mainly includes:?a?physical absorption:the steel slag is of absorption function on the arsenic ion based on its specific surface area and pore structure;the absorption performance of modified material is improved with the increase of pore volume and specific surface area;?b?the chemical absorption:the metal elements of steel slag or its oxide shall form the coprecipitation with the arsenic ion;it is also an important approach for arsenic removal in water body. |
PDF Full Text Request