Immobilization Of Chromium Slag With Alkali Slag-based Geopolymer

Chromium slag is an industrial waste, because it contains Cr6+with high toxicity and is listed as the national hazardous waste. In resource recycling area, before using the chromium slag, needs to be treated harmlessly. Geopolymer is a kind of inorganic polymer materials with excellent properties, having great solidification effect for heavy metals.The preparation of geopolymer for solidifying chromium slag by using blast furnace slag, not only can reduce the environmental problems produced by blast furnace slag stockpiling, but also can effectively prevent the leaching behavior of chromium ion from chromium slag.In this paper, using blast furnace slag as raw material, preparing geopolymer under the action with the alkali activator, the chromium slag is effective solidified. Aim to explore the way for the treatment of chromium slag.In this paper, using XRF, XRD analysis for blast furnace slag composition, shows that the slag containing a number of potentially active substances, such as Ca O, Si O2,Al2O3 and so on which is conducive to the geopolymer preparation.Study on grinding performance of blast furnace slag shows that 12 hours grinding makes it more active.Meanwhile, based on compression strength, the optimum proportion of ingredient for preparing slag-based geopolymer is through the selection of activators, particle size of blast furnace slag and orthogonal experiment. They are as follows that the granularity of blast furnace slag powders is 0.053mm-0.075 mm, the incorporation of blast furnace slag is 90wt%, the mass ratio of water glass/Na OH is 7:3, the liquid-to-solid mass ratio is 0.25. The 28-day compressive strength of geopolymer is 50.4MPa.The preparation of geopolymer with the method of using chromium slag instead of blast furnace slag. From the view of mechanical properties, the strength of geopolymer with 10%~70% chromium slag can meet the requirements for landfill or building material.From the leaching experiment, when chromium slag content is under 60%, the leaching concentrations of Cr6+are below the limits 5.0mg/L which is the established in GB5085.3-2007 "Identification standards for hazardous wastes-Identification for extraction toxicity".All above shows that slag-based geopolymer has better effect on solidifying chromium slag, considering of solidification body mechanics performance and the leaching concentration of chromium slag, the best dosage is 60%.Through the XRD analyzing shows the reaction product of slag-based geopolymer and solidified body are mainly amorphous phase material, and chromium ion may beenclosed in solidified body as in some amorphous phases.SEM analysis shows that the slag-based geopolymer and solidified body are dense state, the SEM-EDS analysis shows that slag-based geopolymer generate geopolymeric gel and CSH gel, and the two amorphous phases of the solidified body are cured with chromium ion.IR comparative analysis indicates that the chromium ion in the solidified body may be involved in the reaction process of geopolymer, it is directly involved in the charge balance, makes the structure of Si-Al recombination happen, and is effectively fixed in solidified body system.Therefore, the solidifying mechanism is the common effect of physical fixation,the adsorption mechanisms and ion exchange.