The Study On The Speciation Of Lead In Aquatic System And The Forming Mechanism Of Non-dissolved Lead

The difference of the content of non-dissolved lead was determined between experimental dataand theoretical value calculated by Visual MINTEQ （Version3.0）（to set the parameters accordingto the experiments lead and the concentration of other ions （ionic groups） in MMS solution）. Dueto the practical and the theoretical value does not match, it was studied that the basic physical andchemical characteristics of non-dissolved lead and its change of speciation and quantity with time,temperature, pH, etc. On the basis of theoretical studies in laboratory, it was explored weather thenatural water brought in non-dissolved lead, the impact of non-dissolved lead on the adsorptionof lead onto suspended particulate matter. The adsorption of lead onto suspended particulatematter was important process of the lead migration in aquatic environment. It was conducive toaccurate analysis of the lead migration in aquatic environment to combine generation ofnon-dissolved lead with the adsorption of lead onto suspended particulate matter.The purpose of this study is to explore the physical and chemical characteristics of non-dissolvedlead under laboratory conditions, as well as the impact of the factors on non-dissolved state leadformation. Microporous membrane filtration and dialysis were used to determine weather thenon-dissolved state lead existed；The electron microscope was used to observe the morphology ofdissolved lead；EMPA analysis was used to determine the elements of dissolved lead; The factorswere studied affecting the formation of dissolved lead.The study showed that the free lead ion changed into the non-dissolved state of lead under pH=6.0in the MMS solution, which did not pass through the molecular weight of8000to14000dialysis membrane. Observing non-dissolved state lead through an electron microscope, we sawdissolved lead was gathered together by the particle size≤0.5ultrafine particles, and the shape ofthe aggregates of these ultrafine particles was irregular. Dissolved lead did not precipitate in thewater naturally. Non-dissolved state lead was detected by EMPA analysis for the formation ofnon-dissolved lead to find that ultrafine particles were mixture of lead, calcium, phosphorus at themolar ratio of about1:1:2, and the formation of non-dissolved state lead related to CaCl₂,KH₂PO₄of MMS solution. The factors including MMS, pH value and temperature affected theformation of non-dissolved lead: Phosphate plays a decisive role in the formation ofnon-dissolved lead; pH value changes affected the OH-concentration in solution; the pH value is bigger, the more non-dissolved state lead generated; The higher the temperature is, the biggerultrafine particle size is and the more loose the combination is. Free of lead ions in natural waterbodies can change into dissolved lead. Due to phosphorus content in natural water is less than theamount of laboratory simulation, and various forms of phosphorus is not all facilitate to theformation of dissolved lead in natural waters, The formation of non-dissolved state of lead is lessthan the amount in laboratory. Non-dissolved lead easily combined with the suspended particlesin the aquatic system, which is conducive to lead transferring to the solid phase in the aquaticenvironment.