Study On Technology And Mechanism Of Preparing Geopolymer From Vanadium-bearing Shale Acid Leaching Residue

Geopolymer is a kind of cementitious material with Si-O-Al network structure,which is mainly composed of ionic bond or covalent bond,formed by activated Silicate-Aluminate materials.They have attracted much attention due to their excellent chemical corrosion resistance,high temperature resistance,freeze-thaw resistance and solidification of heavy metal ions.The vanadium-bearing shale acid leaching residue are common solid wastes in the shale vanadium industry in China.Generally,the content of Si and Al components is relatively high and the particle size is suitable,which has the basic conditions for the preparation of geopolymer.This paper takes the vanadium-bearing shale acid leaching residue as the object of study.Firstly,thermal-chemical activation is used to study the activation pretreatment process of the vanadium-bearing shale acid leaching residue.Then,the vanadium-bearing shale acid leaching residue before and after activation is characterized by XRD,FTIR,SEM-EDS,and its activation mechanism is revealed.The geopolymer with good index was successfully prepared.The research results broadened the raw material sources of geopolymer and solved the environmental problems caused by vanadium tailings.The main conclusions are as follows:Through thermodynamic analysis of the main substances in vanadium-bearing shale acid leaching residue,it was found that sodium carbonate can react with silicon and aluminium minerals in the vanadium-bearing shale acid leaching residue to realize simultaneous activation.The?Si+Al?leaching concentration of activated residue reached 1350.2 mg/L under the conditions of 15 wt%Na₂CO₃ addition,450°C activation temperature and 60 min activation time.Compared with NaOH under the same conditions,the?Si+Al?leaching concentration of activated residue increased by about 30%.Chemical phase transformation analysis of alkali fusion reaction of sodium carbonate shows that under the action of sodium carbonate,the diffraction peaks of quartz in the vanadium-bearing shale acid leaching residue gradually weaken and nepheline gradually appears,which indicates that the crystals of silica-aluminium minerals in the vanadium-bearing shale acid leaching residue have been seriously damaged and nepheline has been formed..At the same time,because the nature of sodium carbonate is milder than sodium hydroxide,its operability is stronger.Thus,safe and efficient activation of vanadium-bearing shale acid leaching residue can be realized.Using the activated vanadium-bearing shale acid leaching residue as raw material,the optimum preparation process of geopolymer was obtained as follows:the ratio of vanadium-bearing shale acid leaching residue to metakaolin is 9:1,the modulus of liquid sodium silicate is 3.0 and the addition of liquid sodium silicate is 14 wt%,Under these conditions,the compressive strength of geopolymer samples can reach27.55 MPa in 3 days.Characterization of the geopolymers prepared by liquid sodium silicate with different modulus indicates that the silicic in liquid sodium silicate acts as an inducer.The higher the modulus of liquid sodium silicate,the higher the content of silicate is,the more rapid the reaction is with the amorphous silicon aluminum material in the vanadium tailing slag,resulting in the formation of more silica alumina gel phase and the enhancement of the compressive strength of the geopolymer.By evaluating the frosting phenomenon of the geopolymer prepared with sodium carbonate as activator,it was found that no frosting phenomenon occurred for a long time?28d?.This indicates that the reaction between sodium carbonate and vanadium-bearing shale acid leaching residue is more sufficient,and the activation efficiency is higher and the activation effect is better.