Analysis On Testing Method Of Heavy Metals In Cement Clinker And Cement

Along with the development of cement industry co-processing of industrial wasteand domestic waste (e.g. sludge), the testing methods of heavy metals in the cementclinker and cement products have caused a great deal of attention of scientists andexperts. This project aims to identify the heavy metal detection methods for clinkerand cement, in order to assess the environmental safety of the heavy metals. Thetesting method of heavy metals is an important technique to assess the possibility ofheavy metal hazards.The total-dissolution testing method of heavy metals for clinkeris a method that all the components through dissolution, complexation, all dissolvedinto the solution; the leaching test method for cement products is a method that thesoluble fraction of sample by means of diffusion, leaching, etc. dissolved into thesolution.In this paper, using the modern testing means, author have made a study ofcomparative testing methods of heavy metals for clinker and different conditions,made a study of comparative leaching method of heavy metal for cement and differentleaching factors, but also made a study of long-term leaching method for mortar andconcrete. On this basis, the heavy metal detection method suitable for clinker andcement are provided, which provide reliable support for the cement kiln and technicalmanagement for the co-disposal of waste. The relevant results are as follows:1. Testing methods are in research, by access to domestic and foreignrepresentative heavy metal total-dissolving and leaching methods, of which wereelected to be in following comparative test.2. The comparison experiments for heavy metal detection were carried on, therepresentative of the clinker total-dissolving method were selected as ASTMD6357-2004, GB/T22105.2-2008, Method A and Method B, evaluation results showthat Method A works well, the other three methods are poor, of which there are stillroom for improvement in accuracy, timeliness, experimental and security, economicand other aspects. The influencing factors on heavy metal testing methods are inresearch, of which for testing method of clinker, the test parameters such as the acidsystem, high temperature and the holding time of high temperature, thelow-temperature complexation time are in research;6ml-2ml-2ml (HCl: HNO3: HF)digestion acid system can achieve the accuruary tesing of the heavy metal contents ofclinker. Finally the optimizations of method for clinker have sorted out. 3. The representation heavy metal testing method of cemnet were selected as theUnited States TCLP, No.46notices of the Japanese Ministry of Environment, NEN7341GB5086.1, EN12457-3in comparison test, and comprehensive analysis showsthat TCLP has good effect, but whether the leaching values are universal (too large ortoo low values are not conducive to assess security control of heavy metals) still needto verify. The influencing factors on heavy metal testing methods for cement are inresearch, test parameters such as sample volume, sample preparation methods,liquid-solid ratio of the extractant, acidity, extraction time, sample size, the standingtime and the oscillation speed are in research. The tests show that acid system, acidity,liquid to solid ratio, significantly affects the detecting value of heavy metals. Acetatebuffer system, low acidity of3.34to4.0and liquid to solid ratio20:1(L/kg) canproduce representative testing results of the cement. Finally the optimizations ofmethod for cement have sorted out.4. Long-term leaching method of heavy metal also is in research, through thewater, the acidic extractant, sulfate/chloride salt solution, carbonation-leaching in thelong-term leaching of mortar and concrete, results show that for the mortar andconcrete, heavy metals have a long-term release process, and the leaching value ofheavy metals are very low. Therefore, from the precision of the experimental resultsand the cyclical experimental time aspect, it is to consider that long-term leaching testis not conducive to the safety assessment of heavy metals, while above optimizedmortar leaching test method should be applied, such rapid detection method.