Removal Of Manganese (?) And DOM From Water By Enhanced Coagulation Process

With the mining,smelting,and tailings accumulation of metal manganese mines,a large number of heavy metal ions enter the earth's surface and groundwater surrounding the mining area through water erosion,wind erosion,seepage,etc.,causing serious pollution to the surrounding water environment.Due to the widespread presence of dissolved organic matter?DOM?in water,some components in DOM are mainly humic acid?HA?and fulvic acid?FA?,which tend to be complex or chelate with Mn in various water bodies to form a more toxic heavy metal-DOM organically bound complex.The treatment of Mn???,DOM and Mn-DOM compound pollutants in water has become a major problem in water environment management.Current research has shown that iron based inorganic flocculants has a better removal effect of organic matter in water,base on this study and the organic flocculant?PAM-GSH?pre-prepared by the laboratory which can effectively remove the Mn???in the water,developed a kind of organic-inorganic composite flocculant which has good removal effect of the Mn???and DOM in the water.Using ferrous sulfate and aluminium sulfate as raw materials,Fe???was oxidized to Fe???by concentrated nitric acid,and disodium hydrogen phosphate was added as a stabilizer,then preparing the PAFS by microwave induced water bath reaction,which investigate the effects of reaction temperature,molar ratio of Al to Fe,molar ratio of P to Fe,and alkalinity degrees on the flocculation performance of PAFS,and the optimum preparation conditions was obtained:the microwave initiation time was 5 min,the reaction temperature was 60°C,and the synthesis time was 2 h,the molar ratio of Al/Fe was 0.4,the molar ratio of P/Fe was 0.2,the molar ratio of OH/?Fe+Al?was 0.4.The products obtained from the optimal preparation conditions were used for the removal of humic acid in water.When the fast stirring speed was350 rpm,the quick stirring time was 3 min,the slow stirring speed was 40 rpm,the slow stirring time was 12 min,the coagulant dosage was 12.8 mg/L,and the pH was8.0,the removal rate of humic acid?DOC?was up to 81.0%.PAFS under optimized conditions and polymer flocculant?PAM-GSH?pre-prepared in the laboratory were compounded at a certain ratio to obtain organic-inorganic composite flocculant?PAM-GSH-PAFS?.The effects of organic component content?Wp?,intrinsic viscosity?ETA?and Alkalinity of inorganic components?B?on the hydrolytic morphology of flocculating agent were studied by Fe-Ferron hourly complexing colorimetry and ultraviolet-visible spectroscopy.The chemical action between organic component PAM-GSH and inorganic component PAFS was proved by Fourier infrared spectrometer,and strong coordination group?-SH?was introduced in macromolecule chains.By scanning electron microscope,the composite flocculant PAM-GSH-PAFS has a certain spatial structure,and the particle size is smaller than the inorganic flocculant PAFS and the organic flocculant PAM-GSH.It has a larger specific specific surface area and has better adsorption effect on water pollutants.By observing the X-ray diffraction pattern of the compound flocculant,some new crystal structures,such as AlFe₂O₄,Al_0.67Fe_0.33?PO₄?,Fe₂O?PO₄?,Al₁₈P₁₈O₇₂ and some amorphous state crystal structures,have been found in the map.It is further confirmed that there is not a simple mixing between the organic components and the inorganic components,but the new complex polymer is generated by the complex chemical reaction.At the same time,the coagulation water samples of Mn???and DOM?humic acid,HA?were used as simulated water samples.The effect ofcomposite flocculant PAM-GSH-PAFS on the removal of Mn???and DOM in water was studied by enhanced coagulation.The effects of dosage,reaction pH,concentration of manganese ion and concentration of DOM on the flocculation performance of the composite flocculant were investigated.The results showed that under the condition of initial concentration of Mn???and DOM was 10 mg/L,the reaction pH was 7.0,the dosage was 300?L/L?Fe₂O₃,5.76 mg/L?,The highest removal rates were respectively63.5%and 82.4%,and the flocculation effect was significantly higher than that of the inorganic or organic flocculant alone,and at the same time,the dosage was greatly reduced.The study found the interaction mechanism between Mn???and DOM in water.The presence of Mn???at a certain concentration can improve the effect of the flocculant on the removal of DOM.When the concentration of DOC is 15.0 mg/L,the concentration of Mn???is 10 mg/L,and the maximum removal rate of Mn???in water reaches 91.7%.