Research Of The Effcet Of Metal Ions On The Formation Of Disinfection By-products During Chlorination

Due to the pollution of industrial wastewater and the corrosion of metal pipes,the amounts and type of metal ion are increased in the natural water environment.The presense of metal ions affect the decay of chlorine and change the formation of disinfection by-products?DBPs?in water.Then,in this study,a variety of humic substance?HS?were used as the model precursors,the effects of Cu²⁺,Ca²⁺,Zn²⁺and Pb²⁺on the formation and distribution of THMs investigated.The main contents and results of this paper are as follows:The structural and functional properties of 5 types of HS were investigated.Results indicated that the chemical and structural properties of HS were different from each other for their dissimilar origin.Increased the chlorine dosage and reaction time improved the formation of CHCl₃ yield.THMsFP yields followed an increasing pattern with increasing Br^-dosage and pH.The structure of the HS was destroyed and the aromaticity of HS was reduced in the chlorination reaction.The products containing C=C,oxygen-containing functional groups,C-Cl and C-Br structures were produced.The effects of metal ions of THMsFP yields did not inconsistent between pH 3 and9.9 during chlorination.Cu²⁺has a catalytic effect on the formation of THMsFP yields.Except for the inhibition of HA-1 and HA-2 in acidic conditions,Ca²⁺promoted THMsFP yields of the other HS.The promotion effect of Zn²⁺on the other HS was observed except for the inhibition of FA-2 in acidic conditions.Pb²⁺except for HA-2 and FA-3 had a weak inhibitory effect at acidic conditions,and other HS were promoted.This effects of increased THMsFP yields of HS followed the order:Cu²⁺>Ca²⁺>Pb²⁺>Zn²⁺.The effects of Cu²⁺,Ca²⁺,Zn²⁺and Pb²⁺on the molecular weight?MW?of HS were inconsistent,and the order of actions were independent of the molecular weight.The most promotion effects of Cu²⁺occurred in the MW range of 10-30 kDa and 5-10 kDa.Ca²⁺showed the enhancement effect on the 10-30 kDa and 5-10 kDa parts,except for the5-10 kDa,<5 kDa,30-100 kDa fractions of FA-3.The inconsistent effects of Zn²⁺on different sources of HS and different molecular weights were observed.the THMsFP yields of the 5-10 kDa of HA and the 10-30 kDa,>100 kDa of FA were prompted mostly by Pb²⁺.The results of UV-Vis spectrum and FTIR spectra indicated oxygen-containing functional groups and methyl and methylene groups were responsible for Cu²⁺binding due to their capability of electron pair donation include carboxylic acids,phenols,alcohols,carbonyls,ethers,and esters.Then,the presence of Cu²⁺varied the pathway of chlorinated reaction and decreased the number of oxygen containing functional groups in chlorine products.The formation of oxygen-containing functional groups were inhibited by Zn²⁺during chlorination.The bands shown on the spectra indicated that the complexation through unsaturated structures?aromatic functional groups?coupled with methyl and methylene or oxygen-substituted functional groups in this HS–Pb²⁺complex.The presence of Pb²⁺in the chloination inhibited the formation of the products with C=O functional groups and C=C structures,and prompted the formation of aliphatic hydrocarbons.