Study On The Heavy Metal Chelating Agent Synthesis And Its Application Performance

In this work,a multi-dithiocarbamate heavy metal chelating agent is synthesized by using 1,6-Hexanediamine?HMD?and carbon disulfide?CS₂?,named HDTC.The main influencing factors for optimum synthetic condition of HDTC on lead removal are raw materials dosage,synthetic temperature,synthetic time and organic solvent.The optimum synthetic conditions are as follow:HMD and CS2 are put into the reactor in accordance with molar ratio 2.2:1,synthetic temperature is 25?,synthetic time is 2h,volume ratio of ethanol and water is 1:1.The structures of HDTC are characterized by infrared analysis,scanning electron microscopy and energy spectrum and elemental analysis,the results shows that HMD grafted dithiocarboxyl group successfully,while the molecular formula of HDTC is confirmed as C₈H₁₆N₂S₄.HDTC is soluble in water and NaOH solution,it's slightly soluble or even insoluble in common organic solvent,and the water solution of HDTC is neutral.Then the heavy metal ions Pb²⁺?Zn²⁺?Cd²⁺?Mn²⁺in the single system are treated by HDTC,the main influencing factors for treatment effect are pH,dosage of HDTC,initial concentration and reaction time,and the results show that HDTC can effectively remove Pb²⁺,Zn²⁺,Cd²⁺and Mn²⁺,respectively.Four heavy metal ion effluents with a concentration of 50mg/L are treated in 200m L,the optimal pH values are 6,7,8 and 8,respectively,the reaction temperature is 10¹4min,the highest removal rates of Pb²⁺,Zn²⁺,Cd²⁺and Mn²⁺are 99.1%,97.32%,98.96%and 92%while the dosage of HDTC are 35mg,50mg,45mg and 80mg respectively.Increasing the dosage of HDTC appropriately that several heavy metal ions mentioned above can also be removed effectively when treating high concentration wastewater.When there are many heavy metal ions in the wastewater,HDTC has a certain sequence on heavy metal ions removal,and the sequence is Pb²⁺>Cd²⁺>Zn²⁺>Mn²⁺.The main mechanism of HDTC capture heavy metal ions in single system is that chelation reaction occurs between heavy metal ions and dithiocarboxyl groups on HDTC molecules,so that the heavy metal ions can be removed by precipitation.Though heavy metal ions also react with the amino group on HDTC,but the main functional group is dithiocarboxyl.To treat the real wastewater by using HDTC,while Pb²⁺,Zn²⁺and Cd²⁺have been well removed,the concentration of Mn²⁺is still high,because of the higher concentration of manganese ions in the wastewater,and other auxiliary means should be considered to remove Mn²⁺.Heavy metal chelating flocs will be generated after treatment,which have good stability and not easy to produce secondary pollution.