Chelating Properties For Heavy Metals Of Modified Corn Starch

With the development of industry, plenty of heavy-metal wastewater containing chelating agents is draining out of the manufacture world. Traditional chemical precipitated method can not meet the emission regulation to treat the ever increasing wastewater. Finding new efficient measures to decrease the heavy metal concentration without second pollution has become the top priority in the environment protection field.In this dissertation, corn starch which is low-cost and can be degraded easily, is modified and applied for the removal of heavy metals from aqueous solutions. Starting from corn starch, cross-link starch derivative containing dithiocarbamate group(DTCS) is synthesized via a series of processes including crosslink, etheration, amination and addition reaction with CS₂. The final product having 18.24% S is obtained through the optimal process.Some parameters affecting metal removal in solution are investigated in this dissertation. In the solution without complexing agent, experimental results show that the ability of DTCS's removing heavy metals is: Cu²⁺>Pb²⁺>Cd²⁺>Zn²⁺>Ni²⁺. The removal efficiencies of them are Cu²⁺99.91 %, Pb²⁺99.88%, Cd²⁺87.36%, Zn²⁺85.17 %, Ni²⁺66.36%. In the mixed solution (five kinds of heavy metals are involved and every metal concentration is 0.5mmol·L^-1), the removal efficiencies of them are all above 99.7%. In the solution with complexing agent(EDTA, Triethanolamine, Tartaric Acid, Ammonium Chloride, Citric Acid), the removal efficiencies of Cu²⁺ are 98.91 %,98.59%,97.85%,95.23%,92.99%.IR spectra of the compounds indicate that the chelating bonds are formed between this chelating reagent and metals.Both the theory and experimental results show that the chelating reagent synthesized in this dissertation have a good effect on removal of heavy metals. It is safe, stable and high efficient. It also can remove different kinds of heavy metals and have a good prospect.