Study On Incorporation Of Heavy Metals In Hazardous Industrial Wastes With Cement Clinker

There is a trend around the world for cement industry to dispose hazardousindustrial wastes (HIW) by means of cement rotary kiln. In the paper, no the base ofcontrast existing waste treating means, introduce some problems on disposinghazardous industrial wastes (HIW) by means of cement rotary kiln and formulate themerits and demerits. A simulation of burning HIW with cement sintering processunder laboratory condition was studied to make certain of the effect of heavy metalelements from HIW on the clinker forming process and the heavy metal elements'incorporation mechanism in the clinker during the process by means of XRD,XPS,DTA and EMPA. Make experiments such as sintering character of raw ,theincorporation ratio and distribution of heavy metals in clinkers, the main mineralphase of clinker fixed heavy metals and the main quantivalency appearing in theclinke were made. With the mixed waste addition bigger, the sintering character of raw and thereaction between solid and liquid phase have been improved, the C3S formationtemperature is fall down as much as 200℃. The DTA showed that only the mixedwaste addition reach a define level, utilizing of heat energy become possible. Moreresearch should be put on the mechanism of high mixed waste addition effect on rawsintering character. The incorporation ratio of heavy metals in lab is :Cr 83.8%；Co 86.1%；Ni86.5%；Cu 74.3%；Zn 74.3%；Cd 88.1%；Pb 86.3%；As 89.3%. As the gas loop modein lab is not as in rotary kiln, The incorporation ratio of heavy metals in lab is smallerthan in rotary kiln. The exist mode of heavy metals in mixed waste have some effecton the incorporation ratio, and make it larger than pure chemical agent. The differentclinker have different incorporation ratio. The incorporation of heavy metals to different clinker minerals is selectivity: Znis concentrated in the interphase of clinker; As,Co,Cu and Ni is mainly incorporatedby C3A and C4AF, but also in C3S and C2S. Cd and Pb can not be separated clearlyfrom interphase and C3S and C2S, they are distributed homogeneously in clinkerminerals. Under the addition of this experiment, the heavy metals doped in the clinker donot have some essential effects on the clinker minerals. Belonging to the first transitional elements, the atomic structure of Co；Ni；Cu；Zn have more similarity as Fe. They can replace Fe to form substitutional solidsolution: :most of Co3+,Ni3+,Cu2+ replace the Fe3+ in octahedron, but Zn2+ replacethe Fe3+ in tetrahedron. Some of Co3+,Ni3+,Cu2+ and Zn2+ also can fill in the cavitywhich radius as much as 1.47 ? in C3A to form solid solution. ；Cd2+ and Pb4+ canreplace Ca2+ in Ca-O octahedron in C3S. Some Si4+ in SiO4 tetrahedron are replacedby As3+. The atomic number and electronegativity of Co；Ni；Cu；Zn is become bigger sothe attractive power between them and O2－ also bigger, the distance of them issmaller. All of these can make the interplanar distance smaller. Either mixed waste III北京工业大学工学硕士学位论文or chemical agent, the heavy metals incorporated in the clinker minerals can reducethe interplanar distance of interphase but not in C3S and C2S. By means of XPS and thermodynamics analyse, The main quantivalency of the8 kinds of heavy metals appearing in the clinker are Cr,＋3； Co,＋3；Ni,＋3；Cu,＋2；Zn,＋2； Cd,＋2； Pb,＋4； As,＋3. The results showed that the burning ability of the raw meal doped with heavymetal elements can also be improved and exhibited much easier especially whentemperature is below 1350℃. Most of the heavy metal elements can be incorporatedin the sintered clinker phases although the incorporation is element selective dependedon the variety of clinker phases. No new substance has been found in clinker. Most ofthe heavy metals can be incorporated by the interphase of clinker because of the spaceexisting in crystal structure. Oxidizing atmosphere of the rot...