Removal Heavy Metals From Organic Silicon Wastewater By Induced Crystallization

Organic silicon wastewater contains multiple heavy metal with high COD, which is treated usually with a lot of PAC and PAM. Over the years, a process is being hoped to be developed, which can realize heavy metal self-coagulation, without or less adding PAC and PAM, so as to separate the heavy metal from wastewater. In this study, induced crystallization have been put forward to remove and recycle the heavy metal at the same time, based on the research of the wastewater treatment technology. Harmless and resource recovery are combined in this process, which can provide a new idea to treat the organic silicon heavy metal wastewater.The effect of HRT, chemical addition ratio and hydraulic loading were explored and analyzed. The research shows that, when the Cu2+ concentration is at 20 mg/L and the Zn2+ concentration is at 10 mg/L in the simulated wastewater, the optimal operating conditions are HRT in 90 min, chemical addition ratio 2:1, hydraulic loading 40 m/h. Under the optimal operation conditions, treatment effect of single Cu2+ wastewater is good, with the crystallization product for short rod and block structure. The Zn2+ could not be removed from the single Zn2+ wastewater with the induced crystallization process. Under the optimal operating conditions, reaction treating the flooding water with Cu2+ 20 mg/L, Zn2+ 10 mg/L lasted 73 days divided into 3 stages. The effluent concentration of Cu2+ reduced to around 1.5mg/L and the effluent concentration of Zn2+ reduced to around 5mg/L in the stable stage. Crystal types of the crystallization particle are different in different stages. The main ingredient of crystallization particle is Cu2(OH)2CO3. But the EDS results show that crystallization particle contains zinc carbonate. Zinc carbonate may attach on the surface unevenly. The biggest size of crystallization particle is 0.632 mm. In the alcohol system, polarity of solvent is different with water system, leading different hydration layer of solute ion, which can affect the ions interaction and effluent concentration of heavy metal ions and crystal type.Therefore, treating organic silicon wastewater with high COD by induced crystallization process is feasible. Further research about changing polarity of solvent system should be explored to improve the effect of induce crystallization process treating heavy metal ions removal.