Removal Of Chlorides,Nitrates Or Sulfates Based On Their Natural Fixation

It is well known that,in order to remove the excess cations in the water,we can convert them to some kinds of precipitates.However,the removal of soluble anions is difficult.Compared to membrane separation method and biochemical method,we proposed a biominetic separation based on the natural fixation of soluble salts by a plant for reducing soluble chloride,nitrate and sulfate.Referring to the composition of Hoagland solution,we designed different kinds of formulations to cultivate Sedum spectabile in aqueous solution.During nine week period of cultivation,an appropriate amount of NaCl,NaNO3 or Na2SO4 was added on a regular basis,and the growth status of the plants was observed.After the cultivation,the element contents in the roots and leaves of Sedum spectabile was analyzed,aiming to guide the settlement experiments.The experimental results showed that Sedum spectabile exhibits a certain tolerance to high concentrations of NaCl,NaNO3 or Na2SO4 solution,and its roots are main sites of fixing these salts.The roots cultivated in distilled water containing NaCl,NaNO3 or Na2SO4 showed a more accumulation of these salts than that in other culture mediums.Based on the contents of element in plant' leaves and roots cultivated under NaCl,NaNO3 or Na2SO4 stress,simulating sedimentation experiments were conducted.The results showed that calcium and phosphate is the main species for the fixation of chloride sodium and potassium chloride,as well as for sodium nitrate and potassium nitrate.And the existence of a lot of carbonate is unfavorable for chloride and nitrate settlement.Calcium is also the key species of sulfate fixation,and the presence of phosphate and carbonate is adverse for the precipitation of sulfate sodium and potassium sulfate.The effects of sediment conditions on the removal of the salts were also investigated.The results showed that the higher the initial concentration of the salts is,the more the removal percentage is.Low temperature is beneficial to the precipitation of chlorides and nitrates.Under a near plant's physiological condition(such as pH=6~8),pH value of treated solutions has little effect on the removal of sulfate.Our work provides valuable information for the efficient removal of soluble chlorides,nitrates and sulfates.