Study On Preparation Of Carbide Slag Composite Particles And The Film-forming Mineralization Characteristics Of Cu²⁺ In AMD

To solve the serious harm of acid mine drainage（AMD）containing heavy metal ions,and the challenge of treatment methods or materials existing low efficiency,high cost,no energy saving,large amount of sludge,difficult fixation and recovery of heavy metal ions.In this paper,alkaline industrial solid waste carbide slag and bentonite are used to calcine and modify to prepare carbide slag composite particles that can generate crystal ions OH^-endogenic internally.It can not only solve the problems of overqiuck alkaline release rate of carbide slag and difficult separation of mud and water,but also realize simultaneous removal of acid and heavy metal ions.In particular,mineralized films can be spontaneously formed around the composite particles to achieve fixed mineralization recovery of Cu²⁺.Macro experiment,micro test,theoretical analysis,data calculation and fitting modeling methods are used in this paper to systematically study the law of influence,preparation mechanism,alkalinity slow release mechanism of the main factors in preparing composite particles,and the film forming and mineralization characteristics,mechanism and law of Cu²⁺in AMD.It is cleared that too high proportion of bentonite or calcium carbide slag will lead to high loss rate of particles and insufficient production of hydrated calcium silicate gel（C-S-H）.NaOH generated by reaction of Na₂CO₃ with Ca（OH）₂ can activate SiO₂ in bentonite to form Na₂SiO₃ and C-S-H gel,which is conducive to particle bonding and alkalinity slow release.Increasing calcination temperature and prolonging calcination time can activate the reaction activity of Si in montmorillonite lattice of bentonite to increase C-S-H production.However,when calcination temperature exceeds 500℃,C-S-H will transform to silicate,calcium aluminate and other crystals,and the particle loss rate will increase and become inactive,which is unfavorable to the removal of Cu²⁺;The optimum preparation conditions of composite particles were determined as:the mass ratio of bentonite to carbide slag was 3:7,the amount of Na₂CO₃ was 10 wt%,and the particles were calcined at 500℃for 60 minutes.In this condition,the particles had good effect on film forming,mineralization and fixation of Cu²⁺;It is revealed that Na₂SiO₃ and C-S-H formed under the action of Na₂CO₃activator and calcination process are beneficial to the preparation mechanism of particle bonding and the mechanism of alkalinity slow release;It is clarified that the mineralization process of mineralized film formation includes two stages:liquid film formation and mineralized growth.It is revealed that the initial formation of liquid film mainly depends on the heat released by particle hydration reaction,the formation of interface layer by Ca（OH）₂ colloid adsorbing thicker water film,and the mechanism of mineralized growth after film formation;It was determined that rotational speed,temperature and initial concentration were the main factors that affecting the mineralization effect of Cu²⁺film-forming.Film-forming mineralization effect of Cu₄SO₄（OH）₆·2H₂O was good under standing conditions,temperature of 25℃～35℃and Cu²⁺concentration of 200～300 mg/L,and the removal rate of Cu²⁺was close to 100%,which could realize the mineralization recovery of Cu²⁺fixed film-forming.In addition,the quasi first order reaction kinetics equation of initial liquid membrane adsorption and the zero order reaction kinetics equation of film-forming mineralization were established.This study provides a new treatment idea for heavy metal ion removal,fixed mineralization and recovery in the field of AMD treatment.The research results have important scientific and theoretical significance and practical application value for the preparation of alkaline composite particulate materials and the fixed recovery of heavy metal ion by film-forming mineralization.This paper has 93 figures,13 tables and 176 references.