Research On Modification Of Fly Ash And Its Effect On The Passivation Of Copper And Zinc In Sludge And The Adsorption Of Copper And Zinc In Water

The sludge which produced by urban sewage plant had heavy metals Cu and Zn exceeding more badly,was an important factor to restrict sludge using, and dangerous to the environment. Fly ash is the thermal power plant coal’s solid waste, its accumulated in the occupation of land resources at the same time caused serious pollution to the surroundings. The purpose to use the fly ash to removal Cu²⁺ and Zn²⁺ of the sewage and passivate Cu and Zn of the sludge, was to use the waste treatment waste, and save the economic cost. So the study intended to carry out the contrast, modified, adsorpt of heavy metals, passivate sludge and the sludge of the theoretical research of leaching experiment at the Twelve. Five national water projects.This paper analyzed the composition of fly ash in Heilongjiang province and Liaoning province, the studies had shown that the chemical compositions of both fly ash（silicon, aluminum, iron and calcium oxide） contained similar proportions.Both fly ashes were mainly containing SiO₂（Quartz）, Al₃Si₂O₁₃（Mullite） and SiO₂（such as Cristobalite） crystal phases structure. Their surface areas were about 1.00 m2/g; The surface morphologies were porous glass ball and similar size.Both places of fly ash contained lots of C-C frame vibration peak（1087 cm-1; 1091 cm-1）, Si-O-Si bending stretching vibration peak（796 cm-1）, Si-O bending vibration peak（459 cm-1）. Therefore, the fly ash and fly ash in Liaoning province were similar with Heilongjiang province, this study intended to use coal ash of Liaoning province as the experiment. By orthogonal experiment, through controlling the acid（alkali） concentration, ratio of acid（alkali） and, dipping time, microwave power, microwave time to design of experiment, and determined the modified fly ash adsorption on heavy metal ions. According to the results, when microwave power was 400 W and irradiated for 10 min, Na OH concentration was 6mol/L and immersed for 3h, alkali and fly ash ratio was 5:1, the modified fly ash got the maximum surface area which was21.01 m2/g, there was a new mineral（Ca2Si O4） generated during passivation, which added new group on the surface of fly ash. The surface had more-OH stretching vibration peak（3614 cm-1, 3564 cm-1）, Si-O(661cm-1,-NH2（1620 cm-1）,- NH2（599 cm-1） and-CH3（2970 cm-1） functional groups, particle had rough surface and adsorption channel increased, so the passivation capability of heavy metal significantly enhanced,and the modified fly ash inspired more phase material, the surface had the more active groups. The modified fly ash was conducive for stable transition of Cu and Zn and the passivation performance was better than the unmodified fly ash.In addition, through kinetic model, thermodynamic model and isotherm adsorption experiments to study the external chemical conditions on the best modified fly ash adsorpted Cu²⁺ and Zn²⁺. The results showed that the removal efficiencies of Cu²⁺ and Zn²⁺ augmented gradually with the increasing of p H, initial ion concentration and MFA dosage simultaneously in the MFA adsorbing process, which was in accordance with the Langmuir model. The theoretical maximum adsorption capacity of Cu²⁺ and Zn²⁺ arrived to 26.25 mg/g and 22.03 mg/g, respectively. The reaction was amenable to the pseudo-second-order kinetic model. According to the adsorption thermodynamics model, this absorption process was a kind of chemical spontaneous endothermic reaction.Studied the effects of the passivation of the passivation time and additive quantity by the best modified fly ash to the Cu and Zn, the research showed that as the additive quantity of fly ash continues to increase, the effect of passivation was the better, especially when addition ratio was 40%（ deducting dry release effect） and passivation lasted for 7 days, heavy metal form could reach a stabilized state, and the proportion of each state did not change with time. Finally, through the soil column leaching experiment showed that heavy metal solidification was stabling in the passivation of sludge, not leaching for amount. The economic benefits of the modified fly ash passivated sludge than traditional treatment sludge（200 600） RMB/ton, down to 40 60 RMB/ton, it had more economic benefits.