The Effect Of Rhamnolipid On The Soil Leaching Effect And Its Influencing Factors Of Rare Earth Elements Lanthanum, Cerium, Lanthanum And Cerium

The Weathered Crust Rare Earth Ore have been discovered,exploited and utilized since 1960 s In Jiangxi area of China.Due to lack of environmental awareness and corporate supervision is not enough,rare earth elements and heavy metals concentrations were seriously overweight in the surrounding soil environment,it had posed a serious threat to the nearby residents,agricultural development and food security.In the current soil remediation techniques,soil washing was a effective technical means to quickly remove contaminants from the soil,to reduce the concentration of pollutants in the soil in a short period of time.Biosurfactants as a new eluent,has been widespread concern,for the low environment toxicity,biodegradable and other characteristics.For the current situation of soil pollution of rare earth mines,This work examined the performance of rhamnolipids solutions for washing La,Ce,Y,Eu from soil.Analyzed of the mechanism of action in-depth,by measured the complexation constants of rhamnolipid and rare earth elements La,Ce,Y,Eu,and the rhamnolipid adsorption behavior in the soil.Compared to before and after leaching and rare earth elements and soil physicochemical properties,analyzed the feasibility of rhamnolipid as the eluent used in rare earth mine restoration,provided a new way of thinking.Research contents and results are as follows:(1)Through the macro and micro observed,we could found the environmental p H values had a great impact on the form of rhamnolipid in solution.When the p H values is low(p H <7),the larger vesicles form of rhamnolipid in solution mainly in leading,and the p H values was lower,the rhamnolipid was more prone settlement;and with the increase of p H value,the micellar form of rhamnolipid became gradually dominant.(2)Adsorption amount of rhamnolipid in the soil followed a linear increasing trend,by contrasting parameter equation,we could found the action of adsorption behavior of rhamnolipid in soil was conform to the Freundlich equation.The capacity of rhamnolipid adsorption in the soil influenced by the p H value,the higher of the p H value,the greater the adsorption constant,and the action was more conform to the linearity;the lower of the p H value,and the action was more conform to the S-curve.(3)Selected the cation exchange resin as an adsorption medium,compared the complexing strength of rhamnolipid with Cu,Zn,La,Ce,Y,Eu.In aqueous systems,the ion exchange effects would increase with the rhamnolipid concentration increased.After calculating,the strength of complexing ability between the various elements was: Y> La> Eu> Ce.Complexation constants were also subject to environmental impact p H,p H value increased,ability of capacity enhanced;in addition,added(NH4)2SO4 and NH4+,SO42-ions could effectively improve the effect of rhamnolipid complex with rare earth elements.(4)By shaking extraction experimental,we analyzed the leaching effect of rhamnolipid on rare earth element La,Ce,Y,Eu,and the effect factors in the soil washing process.Rhamnolipid has the difference on leaching effect of different rare earth elements,leaching effect of La,Ce,Y,Eu strength were: Y> La> Eu> Ce,that similar to the strength of complexing ability.In the reaction system of "rhamnolipid-Rare Earth Elements-soil micelles",when the concentration of rhamnolipid was small(below the threshold concentration),the competitive adsorption in rare earth and rhamnolipid was the mainly action,therefore,with increasing concentration rhamnolipid,leaching rate was rising;when rhamnolipid concentration exceeded the threshold concentration,leaching rate is mainly affected by the strength of the complexing ability of each rare earth element and rhamnolipid.(5)Rhamnolipid as an eluent,it can rapidly improve the added organic matter content in the soil and increase the water retention capacity by soil particles packaged.Contrasting the change of before and after leaching,we could found,added rhamnolipid could be increasing the liquidity of rare earth elements,while promoting the curing of rare earth elements in the soil,by increasing the proportion of organic combination;Leaching with rhamnolipid coild improved the soil p H value,and that could improve the degree of soil acidification;the content of ammonium nitrogen,phosphorus,potassium also showed,rhamnolipid did not cause soil nutrient loss as the eluent.