Removal And Recovery Of Heavy Metals From Wastewater By Induced Crystallization

The treatment of the heavy metals wastewater has become even more important with the implementing of the global sustainable development strategy. Although the pollution index is very high, the heavy metal wastewater is a valuable resource and has a very high potential to reuse or recycle. Therefore, it has vital significance to take widely research about the process which can treat the wastewater environment friendly and convert to reasonable resource. The thesis will use the induced crystallization to remove and recycle the valuable metal, and provide a new idea for the harmlessness and resourcefulness of heavy metals and other valuable materials.The thesis discussed the effects of crystal seeds and running conditions on induced crystallization. The available surface area and the similarity of the lattice structure between crystal seeds and newly born crystals enhanced the diffusion integration process. And when the influent copper concentration was 20 mg/L, the optimum chemical reagent was Na2CO3; the molar ratio of [CT]/[Cu2+] was 1-2, and the hydraulic loading was not be more than 25m/h.According to the problem of homogeneous nucleation while treating high concentration wastewater, there was a preliminary investigation to identify the metastable zone representing a potential zone of optimal supersaturation at which nucleation may have a limiting effect. And then the research put forward several ways for controlling the supersaturation at the intake of the reactor to avoid homogeneous nucleation. On the basic of the conclusions, when the influent copper concentration were 100mg/L and 1000mg/L, the removal efficiency were up to 98%,99% with controlled supersaturation of the reactor.Based on the research of optiumum conditions for crystallization, induced crystallization was employed to treat copper-containing wastewater continuously. After 220 days, there was noticeable growth for the copper pellets and it was verified that the products of crystallization was malachite (Cu2(OH)2CO3) by XRD.In this thesis the induced crystallization replaced precipitation in the PCB wastewater treatment, the removal efficiency of Cu and Ni were up to 90%. And for the first time the induced crystallization was employed to to removal and recycle the heavy metals in the swine wastewater. The recoverd pellets from the wastewaters had a high purity without the growth of biomembrane. It was also verified that the suspended solids of the wastewater had a vital effect on the induced crystallization.