The Study Of Alkali-activated Slag Cementitious Material For Solidification Of Lead-zinc Smelting Slag

In this paper,lead-zinc smelting slag was taken as research object.It was solidified by alkali activated slag cementing material（AAS）.The safety of solidified body with lead-zinc smelting slag was discussed.At the same time,the addition of bentonite strengthens the mechanical properties of the AAS and improves the solidification effect of the AAS on LZSS.The solidification effect of AAS on LZSS was characterized by leaching test and compressive strength test.The solidification mechanism of AAS on LZSS was analyzed.The following results were achieved through laboratory experiments.（1）The preparation parameters of AAS were optimized by single factor experiment and orthogonal experiment.The experiments showed that the compressive strength of AAS could reach 92.89 MPa prepared under the conditions which water glass modulus was 1.4,liquid-solid ratio was 0.26 and curing temperature was 25°C.In addition,bentonite was added to the AAS as an auxiliary additive to strengthen the mechanical properties of AAS.The experiment showed that the addition of 4%bentonite in AAS increased the compressive strength of AASB to 94.57 MPa.（2）The leaching test of LZSS showed that the leaching concentration of Pb²⁺exceeded the Toxicity Characteristic Leaching Procedure（TCLP）standard,and the leaching concentration of Zn²⁺and Mn²⁺was high(Zn²⁺:368.60 mg/L;Mn²⁺:71.83mg/L).The LZSS partially replaced the blast furnace slag（BFS）to prepare the solidified body.With the increase of LZSS in AAS（up to 70%）,the compressive strength of the solidified bodies were reduced,but all of solidified bodies still exceeded60 MPa,which could meet the requirement of compressive strength on geological landfill and building materials（≥10 MPa）;The leaching experiment about solidified bodies showed that the leaching concentration of heavy metals in the solidified bodies was significantly reduced,and the leaching concentration of heavy metals in the AASB was smaller than AAS;The results of morphological analysis of heavy metals showed that heavy metals migrated from relatively unstable states（exchangeable,carbonate bound and iron-manganese oxide bound）to relatively stable states（organio-bound and residual）after solidified by AAS indicating that some heavy metals were stabilized in AAS.As well as,this phenomenon was more obvious in AASB than AAS.（3）The XRD,FTIR and SEM analyses on solidified bodies had indicated that solidification mechanism was carried out by both physical encapsulation and chemical fixation.When the bentonite was added to the AAS to solidify the LZSS,the ion exchange between the bentonite and some heavy metal ions made the heavy metals more stable,and at the same time,the physical entanglement and chemical reaction of the AASB acted on the heavy metals.The double effect enhanced the solidification/stabilization efficiency of AASB on LZSS.