Study On Preparation Of Granulated Composite Materials Of Montmorillonite For Treatment Of Heavy Metal Wastewater

On the basis of an extensive survey of references, the preparation of granulated adsorption materials of montmorillonite/fly ash and their application were systematically studied in this dissertation. The preparation conditions of a granulated adsorption material were firstly explored with the activating agent of fly ash, the cementitious agent of montmorillonite, and the bubbling agent of industrial starch.The optimum preparation conditions for granulated adsorption material of montmorillonite / fly ash were a ratio of montmorillonite to fly ash of 7:3, 10% additive (industrial starch), a calcination temperature of 450℃, a reaction time of 30 minutes, and the diameter of the granular was 1-2mm.The granulated adsorption materials prepared on the above conditions not only was the best effect of removing of heavy metal ions, but also the lowest spallation loss ratio. Analysis methods of XRD, TG and SEM were adopted to characterize the granulated composite materials of montmorillonite/fly ash. The analysis of XRD showed that the mineral phases were not changed. Montmorillonite mainly lost its adsorption water and interlayer water, which was observed from the TG pattern. The granulated adsorption materials improved thermal stability because of industrial starch volatiled. SEM pictures showed that the granulated material had very good porous structure. The diameters of pore were from 20μm to 50μm.The optimal conditions of removal of heavy metal ions with granulated composite materials of montmorillonite/fly ash were as follows: an amount of the granulated adsorbent of 12 g·L^-1, a reaction time of 80 minutes, reaction temperature of 30℃and pH of 5.03 at initial concentration of 200 mg·L^-1 for Cu²⁺; an amount of the granulated adsorbent of 20 g·L^-1, a reaction time of 60 minutes, and reaction temperature of 30℃, pH of 3.00 at initial concentration of 50 mg·L^-1 for Zn²⁺; an amount of the granulated adsorbent of 24 g·L^-1, a reaction time of 80 minutes, and reaction temperature of 30℃, pH of 7.0 at initial concentration of 50mg·L^-1 for Ni²⁺.The removal ratio of Cu²⁺,Zn²⁺,Ni²⁺ were respectively 92.89%, 96.27% and 91.66%. The results of orthogonal analysis showed that the removal ratio was dependent on the reaction condition. The importance of factors to the removal ratio were as follows: For Cu²⁺: adsorbent dosage>pH>adsorption time>the initial concentration of solution, for Zn²⁺:pH > adsorbent dosage>adsorption time>the initial concentration of solution, for Ni²⁺: adsorption time>pH>adsorbent dosage>the initial concentration of solution. The reaction of adsorption was the first order reaction kinetics equation: C_t=C₀×e^-kt, namelylnC_Cu2+=-0.0223t+4.8007,lnC_Zn2+=-0.0066t+3.03, lnC_Ni2+=-0.0047t+3.4447. Above reaction kinetics equation showed that the adsorption was mainly controlled by liquid membrane diffusion. The adsorption data was in line with the Langmuir equation. The thermodynamic parameters wereâ–³H=-14.34kJ/mol;â–³S=-29.50J/mol·K;â–³G=-5.54 kJ/mol<0 which showed that the decrease ofâ–³G was the main driving force for the removal of the heavy metal ions.The granulated composite materials of montmorillonite/fly ash after being used to treat heavy metal wastewater could be desorbed effectively with 1 mol·L^-1 sodium chloride (NaCl). After being regenerated and reused for five times, the exchange capacity of heavy metal ions adsorbed by the granulated adsorption material of montmorillonite /fly ash had decreased slightly, the removal ratio of Cu²⁺,Zn²⁺,Ni²⁺ were respectively 78.63%, 82.92% and 79.00%. The spallation loss ratio of Cu²⁺,Zn²⁺,Ni²⁺ were respectively 6.12%,7.37% and 9.34%. All aboved showed that the granulated adsorption materials regenerated had good treatment effect on heavy metals wastewater.