Supplementary Cementitious Material Properties And Heavy Metal Ion Dissolution Characteristics Of Synergistic Activated Iron-rich Lead-zinc Tailings

The large accumulation of iron-rich lead-zinc tailings will bring serious ecological and environmental problems.Using iron-rich lead-zinc tailings as the supplementary cementitious materials（SCMs）to prepare concrete in the building materials industry is one of the key measures for its resource utilization.However,the use of iron-rich lead-zinc tailings as SCMs is seriously limited due to low hydration activity and poor adaptability of iron-induced water reducer.Based on this,this paper uses the’alkali-thermal-mechanical’synergistic activation and magnetic separation iron removal process to pretreat iron-rich lead-zinc tailings,aiming to improve the performance defects of iron-rich lead-zinc tailings as SCMs and provide theoretical and technical support for its resource application.Firstly,four chemical activators of Na OH,Ca SO₄,Na₂CO₃ and Na₂Si O₃ were selected in the experiment.The synergistic activation effect of iron-rich lead-zinc tailings was studied by orthogonal test of’three factors and four levels’with the dosage of activator,calcination temperature and grinding time as synergistic activation factors and the activity index of 7d,14d and 28d as investigation indexes.Secondly,the influence of different iron content on the activity index and water reducing agent adaptability of synergistic activated lead-zinc tailings auxiliary cementitious materials was studied by magnetic separation process.Finally,the safety of the synergistic activated lead-zinc tailings as SCMs was evaluated by heavy metal dissolution test.The main conclusions of this study are as follows:（1）The synergistic activation effect of iron-rich lead-zinc tailings with Na OH as activator is the best.The optimum synergistic activation conditions are Na OH dosage of1%,calcination at 800°C for 60 min,mechanical grinding for 40 min;the activity indexes of iron-rich lead-zinc tailings at 7d,14d and 28d under the optimal synergistic activation conditions were 75.31%,78.99%and 82.89%,respectively.（2）The activity index of lead-zinc tailings after magnetic separation was further improved with the decrease of iron content.Compared with the lead-zinc tailings without iron removal,the activity indexes of 7d,14d and 28d were increased by 5.8%,3.9%and 1.5%,respectively.With the decrease of iron content,the fluidity of cement paste of synergistic activation lead-zinc tailings increased significantly,and the adaptability to admixture was improved significantly.（3）The dissolution test of heavy metal ions shows that the synergistic activation increases the dissolution concentration of Pb and Zn heavy metals in the iron-rich lead-zinc tailings,and the cement paste with the synergistic activated lead-zinc tailings as SCMs has a high solid sealing effect on Pb,Zn and other heavy metal ions.The dissolution concentration of heavy metal ions meets the requirements of hazardous waste discharge,and the synergistic activated lead-zinc tailings are safe in engineering applications as SCMs.